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Sample records for axon guidance receptors

  1. Cannabinoid receptor CB2 modulates axon guidance

    DEFF Research Database (Denmark)

    Duff, Gabriel; Argaw, Anteneh; Cecyre, Bruno;

    2013-01-01

    Navigation of retinal projections towards their targets is regulated by guidance molecules and growth cone transduction mechanisms. Here, we present in vitro and in vivo evidences that the cannabinoid receptor 2 (CB2R) is expressed along the retino-thalamic pathway and exerts a modulatory action ...... CB2R's implication in retinothalamic development. Overall, this study demonstrates that the contribution of endocannabinoids to brain development is not solely mediated by CB1R, but also involves CB2R....

  2. A developmental timing switch promotes axon outgrowth independent of known guidance receptors.

    Directory of Open Access Journals (Sweden)

    Katherine Olsson-Carter

    2010-08-01

    Full Text Available To form functional neuronal connections, axon outgrowth and guidance must be tightly regulated across space as well as time. While a number of genes and pathways have been shown to control spatial features of axon development, very little is known about the in vivo mechanisms that direct the timing of axon initiation and elongation. The Caenorhabditis elegans hermaphrodite specific motor neurons (HSNs extend a single axon ventrally and then anteriorly during the L4 larval stage. Here we show the lin-4 microRNA promotes HSN axon initiation after cell cycle withdrawal. Axons fail to form in lin-4 mutants, while they grow prematurely in lin-4-overexpressing animals. lin-4 is required to down-regulate two inhibitors of HSN differentiation--the transcriptional regulator LIN-14 and the "stemness" factor LIN-28--and it likely does so through a cell-autonomous mechanism. This developmental switch depends neither on the UNC-40/DCC and SAX-3/Robo receptors nor on the direction of axon growth, demonstrating that it acts independently of ventral guidance signals to control the timing of HSN axon elongation.

  3. The axon guidance receptor gene ROBO1 is a candidate gene for developmental dyslexia.

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    Katariina Hannula-Jouppi

    2005-10-01

    Full Text Available Dyslexia, or specific reading disability, is the most common learning disorder with a complex, partially genetic basis, but its biochemical mechanisms remain poorly understood. A locus on Chromosome 3, DYX5, has been linked to dyslexia in one large family and speech-sound disorder in a subset of small families. We found that the axon guidance receptor gene ROBO1, orthologous to the Drosophila roundabout gene, is disrupted by a chromosome translocation in a dyslexic individual. In a large pedigree with 21 dyslexic individuals genetically linked to a specific haplotype of ROBO1 (not found in any other chromosomes in our samples, the expression of ROBO1 from this haplotype was absent or attenuated in affected individuals. Sequencing of ROBO1 in apes revealed multiple coding differences, and the selection pressure was significantly different between the human, chimpanzee, and gorilla branch as compared to orangutan. We also identified novel exons and splice variants of ROBO1 that may explain the apparent phenotypic differences between human and mouse in heterozygous loss of ROBO1. We conclude that dyslexia may be caused by partial haplo-insufficiency for ROBO1 in rare families. Thus, our data suggest that a slight disturbance in neuronal axon crossing across the midline between brain hemispheres, dendrite guidance, or another function of ROBO1 may manifest as a specific reading disability in humans.

  4. The Axon Guidance Receptor Gene ROBO1 Is a Candidate Gene for Developmental Dyslexia.

    Directory of Open Access Journals (Sweden)

    2005-10-01

    Full Text Available Dyslexia, or specific reading disability, is the most common learning disorder with a complex, partially genetic basis, but its biochemical mechanisms remain poorly understood. A locus on Chromosome 3, DYX5, has been linked to dyslexia in one large family and speech-sound disorder in a subset of small families. We found that the axon guidance receptor gene ROBO1, orthologous to the Drosophila roundabout gene, is disrupted by a chromosome translocation in a dyslexic individual. In a large pedigree with 21 dyslexic individuals genetically linked to a specific haplotype of ROBO1 (not found in any other chromosomes in our samples, the expression of ROBO1 from this haplotype was absent or attenuated in affected individuals. Sequencing of ROBO1 in apes revealed multiple coding differences, and the selection pressure was significantly different between the human, chimpanzee, and gorilla branch as compared to orangutan. We also identified novel exons and splice variants of ROBO1 that may explain the apparent phenotypic differences between human and mouse in heterozygous loss of ROBO1. We conclude that dyslexia may be caused by partial haplo-insufficiency for ROBO1 in rare families. Thus, our data suggest that a slight disturbance in neuronal axon crossing across the midline between brain hemispheres, dendrite guidance, or another function of ROBO1 may manifest as a specific reading disability in humans.

  5. Functions of axon guidance molecules in synapse formation

    OpenAIRE

    Chen, Shih-Yu; Cheng, Hwai-Jong

    2009-01-01

    Axon guidance and synapse formation are important developmental events for establishing a functional neuronal circuitry. These two related cellular processes occur in a coordinated fashion but previous studies from multiple model organisms seemed to suggest that axon guidance and synapse formation are mediated by distinct molecular cues. Thus, axon guidance molecules are responsible for guiding the navigating axon toward its target area, while other adhesion or ligand-receptor molecules speci...

  6. Low-density Lipoprotein Receptor-related Proteins in a Novel Mechanism of Axon Guidance and Peripheral Nerve Regeneration.

    Science.gov (United States)

    Landowski, Lila M; Pavez, Macarena; Brown, Lachlan S; Gasperini, Robert; Taylor, Bruce V; West, Adrian K; Foa, Lisa

    2016-01-15

    The low-density lipoprotein receptor-related protein receptors 1 and 2 (LRP1 and LRP2) are emerging as important cell signaling mediators in modulating neuronal growth and repair. We examined whether LRP1 and LRP2 are able to mediate a specific aspect of neuronal growth: axon guidance. We sought to identify LRP1 and LRP2 ligands that could induce axonal chemoattraction, which might have therapeutic potential. Using embryonic sensory neurons (rat dorsal root ganglia) in a growth cone turning assay, we tested a range of LRP1 and LRP2 ligands for the ability to guide growth cone navigation. Three ligands were chemorepulsive: α-2-macroglobulin, tissue plasminogen activator, and metallothionein III. Conversely, only one LRP ligand, metallothionein II, was found to be chemoattractive. Chemoattraction toward a gradient of metallothionein II was calcium-dependent, required the expression of both LRP1 and LRP2, and likely involves further co-receptors such as the tropomyosin-related kinase A (TrkA) receptor. The potential for LRP-mediated chemoattraction to mediate axonal regeneration was examined in vivo in a model of chemical denervation in adult rats. In these in vivo studies, metallothionein II was shown to enhance epidermal nerve fiber regeneration so that it was complete within 7 days compared with 14 days in saline-treated animals. Our data demonstrate that both LRP1 and LRP2 are necessary for metallothionein II-mediated chemotactic signal transduction and that they may form part of a signaling complex. Furthermore, the data suggest that LRP-mediated chemoattraction represents a novel, non-classical signaling system that has therapeutic potential as a disease-modifying agent for the injured peripheral nervous system.

  7. The Caenorhabditis elegans Eph receptor activates NCK and N-WASP, and inhibits Ena/VASP to regulate growth cone dynamics during axon guidance.

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    Mohamed, Ahmed M; Boudreau, Jeffrey R; Yu, Fabian P S; Liu, Jun; Chin-Sang, Ian D

    2012-01-01

    The Eph receptor tyrosine kinases (RTKs) are regulators of cell migration and axon guidance. However, our understanding of the molecular mechanisms by which Eph RTKs regulate these processes is still incomplete. To understand how Eph receptors regulate axon guidance in Caenorhabditis elegans, we screened for suppressors of axon guidance defects caused by a hyperactive VAB-1/Eph RTK. We identified NCK-1 and WSP-1/N-WASP as downstream effectors of VAB-1. Furthermore, VAB-1, NCK-1, and WSP-1 can form a complex in vitro. We also report that NCK-1 can physically bind UNC-34/Enabled (Ena), and suggest that VAB-1 inhibits the NCK-1/UNC-34 complex and negatively regulates UNC-34. Our results provide a model of the molecular events that allow the VAB-1 RTK to regulate actin dynamics for axon guidance. We suggest that VAB-1/Eph RTK can stop axonal outgrowth by inhibiting filopodia formation at the growth cone by activating Arp2/3 through a VAB-1/NCK-1/WSP-1 complex and by inhibiting UNC-34/Ena activity.

  8. Wnt-induced calcium signaling mediates axon growth and guidance in the developing corpus callosum.

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    Hutchins, B Ian; Li, Li; Kalil, Katherine

    2012-01-10

    Wnt5a gradients guide callosal axons by repulsion through Ryk receptors in vivo. We recently found that Wnt5a repels cortical axons and promotes axon outgrowth through calcium signaling in vitro. Here, using cortical slices, we show that Wnt5a signals through Ryk to guide and promote outgrowth of callosal axons after they cross the midline. Calcium transient frequencies in callosal growth cones positively correlate with axon outgrowth rates in vitro. In cortical slices, calcium release through inositol 1,4,5-trisphosphate (IP(3)) receptors and calcium entry through transient receptor potential channels modulate axon growth and guidance. Knocking down Ryk inhibits calcium signaling in cortical axons, reduces rates of axon outgrowth subsequent to midline crossing, and causes axon guidance defects. Calcium- and calmodulin-dependent protein kinase II (CaMKII) is required downstream of Wnt-induced calcium signaling for postcrossing callosal axon growth and guidance. Taken together, these results suggest that growth and guidance of postcrossing callosal axons by Wnt-Ryk-calcium signaling involves axon repulsion through CaMKII.

  9. Wnt5a regulates midbrain dopaminergic axon growth and guidance.

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    Brette D Blakely

    Full Text Available During development, precise temporal and spatial gradients are responsible for guiding axons to their appropriate targets. Within the developing ventral midbrain (VM the cues that guide dopaminergic (DA axons to their forebrain targets remain to be fully elucidated. Wnts are morphogens that have been identified as axon guidance molecules. Several Wnts are expressed in the VM where they regulate the birth of DA neurons. Here, we describe that a precise temporo-spatial expression of Wnt5a accompanies the development of nigrostriatal projections by VM DA neurons. In mice at E11.5, Wnt5a is expressed in the VM where it was found to promote DA neurite and axonal growth in VM primary cultures. By E14.5, when DA axons are approaching their striatal target, Wnt5a causes DA neurite retraction in primary cultures. Co-culture of VM explants with Wnt5a-overexpressing cell aggregates revealed that Wnt5a is capable of repelling DA neurites. Antagonism experiments revealed that the effects of Wnt5a are mediated by the Frizzled receptors and by the small GTPase, Rac1 (a component of the non-canonical Wnt planar cell polarity pathway. Moreover, the effects were specific as they could be blocked by Wnt5a antibody, sFRPs and RYK-Fc. The importance of Wnt5a in DA axon morphogenesis was further verified in Wnt5a-/- mice, where fasciculation of the medial forebrain bundle (MFB as well as the density of DA neurites in the MFB and striatal terminals were disrupted. Thus, our results identify a novel role of Wnt5a in DA axon growth and guidance.

  10. EFN-4 functions in LAD-2-mediated axon guidance in Caenorhabditis elegans.

    Science.gov (United States)

    Dong, Bingyun; Moseley-Alldredge, Melinda; Schwieterman, Alicia A; Donelson, Cory J; McMurry, Jonathan L; Hudson, Martin L; Chen, Lihsia

    2016-04-01

    During development of the nervous system, growing axons rely on guidance molecules to direct axon pathfinding. A well-characterized family of guidance molecules are the membrane-associated ephrins, which together with their cognate Eph receptors, direct axon navigation in a contact-mediated fashion. InC. elegans, the ephrin-Eph signaling system is conserved and is best characterized for their roles in neuroblast migration during early embryogenesis. This study demonstrates a role for the C. elegans ephrin EFN-4 in axon guidance. We provide both genetic and biochemical evidence that is consistent with the C. elegans divergent L1 cell adhesion molecule LAD-2 acting as a non-canonical ephrin receptor to EFN-4 to promote axon guidance. We also show that EFN-4 probably functions as a diffusible factor because EFN-4 engineered to be soluble can promote LAD-2-mediated axon guidance. This study thus reveals a potential additional mechanism for ephrins in regulating axon guidance and expands the repertoire of receptors by which ephrins can signal.

  11. Whole Genome Sequencing of Newly Established Pancreatic Cancer Lines Identifies Novel Somatic Mutation (c.2587G>A in Axon Guidance Receptor Plexin A1 as Enhancer of Proliferation and Invasion.

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    Rebecca Sorber

    Full Text Available The genetic profile of human pancreatic cancers harbors considerable heterogeneity, which suggests a possible explanation for the pronounced inefficacy of single therapies in this disease. This observation has led to a belief that custom therapies based on individual tumor profiles are necessary to more effectively treat pancreatic cancer. It has recently been discovered that axon guidance genes are affected by somatic structural variants in up to 25% of human pancreatic cancers. Thus far, however, some of these mutations have only been correlated to survival probability and no function has been assigned to these observed axon guidance gene mutations in pancreatic cancer. In this study we established three novel pancreatic cancer cell lines and performed whole genome sequencing to discover novel mutations in axon guidance genes that may contribute to the cancer phenotype of these cells. We discovered, among other novel somatic variants in axon guidance pathway genes, a novel mutation in the PLXNA1 receptor (c.2587G>A in newly established cell line SB.06 that mediates oncogenic cues of increased invasion and proliferation in SB.06 cells and increased invasion in 293T cells upon stimulation with the receptor's natural ligand semaphorin 3A compared to wild type PLXNA1 cells. Mutant PLXNA1 signaling was associated with increased Rho-GTPase and p42/p44 MAPK signaling activity and cytoskeletal expansion, but not changes in E-cadherin, vimentin, or metalloproteinase 9 expression levels. Pharmacologic inhibition of the Rho-GTPase family member CDC42 selectively abrogated PLXNA1 c.2587G>A-mediated increased invasion. These findings provide in-vitro confirmation that somatic mutations in axon guidance genes can provide oncogenic gain-of-function signals and may contribute to pancreatic cancer progression.

  12. Dopaminergic axon guidance: which makes what?

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    Laetitia ePrestoz

    2012-07-01

    Full Text Available Mesotelencephalic pathways in the adult central nervous system have been studied in great detail because of their implication in major physiological functions as well as in psychiatric, neurological and neurodegenerative diseases. However, the ontogeny of these pathways and the molecular mechanisms that guide dopaminergic axons during embryogenesis have been only recently studied. This line of research is of crucial interest for the repair of lesioned circuits in adulthood following neurodegenerative diseases or common traumatic injuries. For instance, in the adult, the anatomic and functional repair of the nigrostriatal pathway following dopaminergic embryonic neuron transplantation suggests that specific guidance cues exist which govern embryonic fibers outgrowth, and suggests that axons from transplanted embryonic cells are able to respond to theses cues, which then guide them to their final targets. In this review, we first synthesize the work that has been performed in the last few years on developing mesotelencephalic pathways, and summarize the current knowledge on the identity of cellular and molecular signals thought to be involved in establishing mesotelencephalic dopaminergic neuronal connectivity during embryogenesis in the central nervous system of rodents. Then, we review the modulation of expression of these molecular signals in the lesioned adult brain and discuss their potential role in remodeling the mesotelencephalic dopaminergic circuitry, with a particular focus on Parkinson’s disease. Identifying guidance molecules involved in the connection of grafted cells may be useful for cellular therapy in Parkinsonian patients, as these molecules may help direct axons from grafted cells along the long distance they have to travel from the substantia nigra to the striatum.

  13. Axon guidance and neuronal migration research in China

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Proper migration of neuronal somas and axonal growth cones to designated locations in the developing brain is essential for the assembly of functional neuronal circuits.Rapid progress in research of axon guidance and neuronal migration has been made in the last twenty years.Chinese researchers began their exploration in this field ten years ago and have made significant contributions in clarifying the signal transduction of axon guidance and neuronal migration.Several unique experimental approaches,including the migration assay of single isolated neurons in response to locally delivered guidance cues,have been developed by Chinese neuroscientists to investigate the molecular machinery underlying these guidance events.

  14. Signaling mechanisms in cortical axon growth, guidance and branching

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    Katherine eKalil

    2011-09-01

    Full Text Available Precise wiring of cortical circuits during development depends upon axon extension, guidance and branching to appropriate targets. Motile growth cones at axon tips navigate through the nervous system by responding to molecular cues, which modulate signaling pathways within axonal growth cones. Intracellular calcium signaling has emerged as a major transducer of guidance cues but exactly how calcium signaling pathways modify the actin and microtubule cytoskeleton to evoke growth cone behaviors and axon branching is still mysterious. Axons must often pause in their outgrowth while their branches extend into targets. Some evidence suggests a competition between growth of axons and branches but the mechanisms are poorly understood. Since it is difficult to study growing axons deep within the mammalian brain, much of what we know about signaling pathways and cytoskeletal dynamics has come from studies of axonal growth cones, in many cases from non-mammalian species, growing in tissue culture. Consequently it is not well understood how guidance cues relevant to mammalian neural development in vivo signal to the growth cone cytoskeleton during axon outgrowth and guidance. In this review we describe our recent work in dissociated cultures of developing rodent sensorimotor cortex in the context of the current literature on molecular guidance cues, calcium signaling pathways and cytoskeletal dynamics that regulate growth cone behaviors. A major challenge is to relate findings in tissue culture to mechanisms of cortical development in vivo. Toward this goal, we describe our recent work in cortical slices, which preserve the complex cellular and molecular environment of the mammalian brain but allow direct visualization of growth cone behaviors and calcium signaling. Findings from this work suggest that mechanisms regulating axon growth and guidance in dissociated culture neurons also underlie development of cortical connectivity in vivo.

  15. RGM is a repulsive guidance molecule for retinal axons

    DEFF Research Database (Denmark)

    Monnier, Philippe P; Sierra, Ana; Macchi, Paolo;

    2002-01-01

    Axons rely on guidance cues to reach remote targets during nervous system development. A well-studied model system for axon guidance is the retinotectal projection. The retina can be divided into halves; the nasal half, next to the nose, and the temporal half. A subset of retinal axons, those from...... the temporal half, is guided by repulsive cues expressed in a graded fashion in the optic tectum, part of the midbrain. Here we report the cloning and functional characterization of a membrane-associated glycoprotein, which we call RGM (repulsive guidance molecule). This molecule shares no sequence homology...... with known guidance cues, and its messenger RNA is distributed in a gradient with increasing concentration from the anterior to posterior pole of the embryonic tectum. Recombinant RGM at low nanomolar concentration induces collapse of temporal but not of nasal growth cones and guides temporal retinal axons...

  16. Prolyl Isomerase Pin1 Regulates Axon Guidance by Stabilizing CRMP2A Selectively in Distal Axons

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    Martin Balastik

    2015-10-01

    Full Text Available Axon guidance relies on precise translation of extracellular signal gradients into local changes in cytoskeletal dynamics, but the molecular mechanisms regulating dose-dependent responses of growth cones are still poorly understood. Here, we show that during embryonic development in growing axons, a low level of Semaphorin3A stimulation is buffered by the prolyl isomerase Pin1. We demonstrate that Pin1 stabilizes CDK5-phosphorylated CRMP2A, the major isoform of CRMP2 in distal axons. Consequently, Pin1 knockdown or knockout reduces CRMP2A levels specifically in distal axons and inhibits axon growth, which can be fully rescued by Pin1 or CRMP2A expression. Moreover, Pin1 knockdown or knockout increases sensitivity to Sema3A-induced growth cone collapse in vitro and in vivo, leading to developmental abnormalities in axon guidance. These results identify an important isoform-specific function and regulation of CRMP2A in controlling axon growth and uncover Pin1-catalyzed prolyl isomerization as a regulatory mechanism in axon guidance.

  17. Guidance Receptors in the Nervous and Cardiovascular Systems.

    Science.gov (United States)

    Rubina, K A; Tkachuk, V A

    2015-10-01

    Blood vessels and nervous fibers grow in parallel, for they express similar receptors for chemokine substances. Recently, much attention is being given to studying guidance receptors and their ligands besides the growth factors, cytokines, and chemokines necessary to form structures in the nervous and vascular systems. Such guidance molecules determine trajectory for growing axons and vessels. Guidance molecules include Ephrins and their receptors, Neuropilins and Plexins as receptors for Semaphorins, Robos as receptors for Slit-proteins, and UNC5B receptors binding Netrins. Apart from these receptors and their ligands, urokinase and its receptor (uPAR) and T-cadherin are also classified as guidance molecules. The urokinase system mediates local proteolysis at the leading edge of cells, thereby providing directed migration. T-cadherin is a repellent molecule that regulates the direction of growing axons and blood vessels. Guidance receptors also play an important role in the diseases of the nervous and cardiovascular systems.

  18. Highly effective photonic cue for repulsive axonal guidance.

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    Bryan J Black

    Full Text Available In vivo nerve repair requires not only the ability to regenerate damaged axons, but most importantly, the ability to guide developing or regenerating axons along paths that will result in functional connections. Furthermore, basic studies in neuroscience and neuro-electronic interface design require the ability to construct in vitro neural circuitry. Both these applications require the development of a noninvasive, highly effective tool for axonal growth-cone guidance. To date, a myriad of technologies have been introduced based on chemical, electrical, mechanical, and hybrid approaches (such as electro-chemical, optofluidic flow and photo-chemical methods. These methods are either lacking in desired spatial and temporal selectivity or require the introduction of invasive external factors. Within the last fifteen years however, several attractive guidance cues have been developed using purely light based cues to achieve axonal guidance. Here, we report a novel, purely optical repulsive guidance technique that uses low power, near infrared light, and demonstrates the guidance of primary goldfish retinal ganglion cell axons through turns of up to 120 degrees and over distances of ∼90 µm.

  19. Shh goes multidirectional in axon guidance

    Institute of Scientific and Technical Information of China (English)

    Paola Bovolenta; Luisa Sanchez-Arrones

    2012-01-01

    Shh and Wnts,secreted by the floor and roof plate of the spinal cord,direct longitudinal growth of the axons from the adjacent ventral funiculus and cortico-spinal tract.Whether these midline cues influencethe directionality of axons elongating in more lateral positions of the spinal cord is unexplored.Song and colleagues investigate this possibility and demonstrate that the location of descending raphe-spinal tract in the ventrolateral spinal cord is dictated by the simultaneous repellent activity of Shh gradients in both the anteriorto-posterior (A-P) and medial-tolateral (M-L) axis. The spinal cord is the main pathway for exchange of information between the brain and the rest of the body.Sensory information collected in the body periphery is conveyed to the brain by axonal tracts that ascend along the spinal cord whereas motor information travels from the brain to the periphery in descending tracts.Precise spatial organization of these fiber tracts is thus essential for animal behavior and survival.

  20. Synergistic integration of Netrin and ephrin axon guidance signals by spinal motor neurons.

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    Poliak, Sebastian; Morales, Daniel; Croteau, Louis-Philippe; Krawchuk, Dayana; Palmesino, Elena; Morton, Susan; Cloutier, Jean-François; Charron, Frederic; Dalva, Matthew B; Ackerman, Susan L; Kao, Tzu-Jen; Kania, Artur

    2015-01-01

    During neural circuit assembly, axonal growth cones are exposed to multiple guidance signals at trajectory choice points. While axonal responses to individual guidance cues have been extensively studied, less is known about responses to combination of signals and underlying molecular mechanisms. Here, we studied the convergence of signals directing trajectory selection of spinal motor axons entering the limb. We first demonstrate that Netrin-1 attracts and repels distinct motor axon populations, according to their expression of Netrin receptors. Quantitative in vitro assays demonstrate that motor axons synergistically integrate both attractive or repulsive Netrin-1 signals together with repulsive ephrin signals. Our investigations of the mechanism of ephrin-B2 and Netrin-1 integration demonstrate that the Netrin receptor Unc5c and the ephrin receptor EphB2 can form a complex in a ligand-dependent manner and that Netrin-ephrin synergistic growth cones responses involve the potentiation of Src family kinase signaling, a common effector of both pathways. PMID:26633881

  1. Mechanisms of TSC-mediated control of synapse assembly and axon guidance.

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    Sarah Knox

    Full Text Available Tuberous sclerosis complex is a dominant genetic disorder produced by mutations in either of two tumor suppressor genes, TSC1 and TSC2; it is characterized by hamartomatous tumors, and is associated with severe neurological and behavioral disturbances. Mutations in TSC1 or TSC2 deregulate a conserved growth control pathway that includes Ras homolog enriched in brain (Rheb and Target of Rapamycin (TOR. To understand the function of this pathway in neural development, we have examined the contributions of multiple components of this pathway in both neuromuscular junction assembly and photoreceptor axon guidance in Drosophila. Expression of Rheb in the motoneuron, but not the muscle of the larval neuromuscular junction produced synaptic overgrowth and enhanced synaptic function, while reductions in Rheb function compromised synapse development. Synapse growth produced by Rheb is insensitive to rapamycin, an inhibitor of Tor complex 1, and requires wishful thinking, a bone morphogenetic protein receptor critical for functional synapse expansion. In the visual system, loss of Tsc1 in the developing retina disrupted axon guidance independently of cellular growth. Inhibiting Tor complex 1 with rapamycin or eliminating the Tor complex 1 effector, S6 kinase (S6k, did not rescue axon guidance abnormalities of Tsc1 mosaics, while reductions in Tor function suppressed those phenotypes. These findings show that Tsc-mediated control of axon guidance and synapse assembly occurs via growth-independent signaling mechanisms, and suggest that Tor complex 2, a regulator of actin organization, is critical in these aspects of neuronal development.

  2. Primary neuron culture for nerve growth and axon guidance studies in zebrafish (Danio rerio.

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    Zheyan Chen

    Full Text Available Zebrafish (Danio rerio is a widely used model organism in genetics and developmental biology research. Genetic screens have proven useful for studying embryonic development of the nervous system in vivo, but in vitro studies utilizing zebrafish have been limited. Here, we introduce a robust zebrafish primary neuron culture system for functional nerve growth and guidance assays. Distinct classes of central nervous system neurons from the spinal cord, hindbrain, forebrain, and retina from wild type zebrafish, and fluorescent motor neurons from transgenic reporter zebrafish lines, were dissociated and plated onto various biological and synthetic substrates to optimize conditions for axon outgrowth. Time-lapse microscopy revealed dynamically moving growth cones at the tips of extending axons. The mean rate of axon extension in vitro was 21.4±1.2 µm hr(-1 s.e.m. for spinal cord neurons, which corresponds to the typical ∼0.5 mm day(-1 growth rate of nerves in vivo. Fluorescence labeling and confocal microscopy demonstrated that bundled microtubules project along axons to the growth cone central domain, with filamentous actin enriched in the growth cone peripheral domain. Importantly, the growth cone surface membrane expresses receptors for chemotropic factors, as detected by immunofluorescence microscopy. Live-cell functional assays of axon extension and directional guidance demonstrated mammalian brain-derived neurotrophic factor (BDNF-dependent stimulation of outgrowth and growth cone chemoattraction, whereas mammalian myelin-associated glycoprotein inhibited outgrowth. High-resolution live-cell Ca(2+-imaging revealed local elevation of cytoplasmic Ca(2+ concentration in the growth cone induced by BDNF application. Moreover, BDNF-induced axon outgrowth, but not basal outgrowth, was blocked by treatments to suppress cytoplasmic Ca(2+ signals. Thus, this primary neuron culture model system may be useful for studies of neuronal development

  3. Quantifying mechanical force in axonal growth and guidance

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    Ahmad Ibrahim Mahmoud Athamneh

    2015-09-01

    Full Text Available Mechanical force plays a fundamental role in neuronal development, physiology, and regeneration. In particular, research has shown that force is involved in growth cone-mediated axonal growth and guidance as well as stretch-induced elongation when an organism increases in size after forming initial synaptic connections. However, much of the details about the exact role of force in these fundamental processes remain unknown. In this review, we highlight (1 standing questions concerning the role of mechanical force in axonal growth and guidance and (2 different experimental techniques used to quantify forces in axons and growth cones. We believe that satisfying answers to these questions will require quantitative information about the relationship between elongation, forces, cytoskeletal dynamics, axonal transport, signaling, substrate adhesion, and stiffness contributing to directional growth advance. Furthermore, we address why a wide range of force values have been reported in the literature, and what these values mean in the context of neuronal mechanics. We hope that this review will provide a guide for those interested in studying the role of force in development and regeneration of neuronal networks.

  4. Pancreatic cancer genomes reveal aberrations in axon guidance pathway genes.

    Science.gov (United States)

    Biankin, Andrew V; Waddell, Nicola; Kassahn, Karin S; Gingras, Marie-Claude; Muthuswamy, Lakshmi B; Johns, Amber L; Miller, David K; Wilson, Peter J; Patch, Ann-Marie; Wu, Jianmin; Chang, David K; Cowley, Mark J; Gardiner, Brooke B; Song, Sarah; Harliwong, Ivon; Idrisoglu, Senel; Nourse, Craig; Nourbakhsh, Ehsan; Manning, Suzanne; Wani, Shivangi; Gongora, Milena; Pajic, Marina; Scarlett, Christopher J; Gill, Anthony J; Pinho, Andreia V; Rooman, Ilse; Anderson, Matthew; Holmes, Oliver; Leonard, Conrad; Taylor, Darrin; Wood, Scott; Xu, Qinying; Nones, Katia; Fink, J Lynn; Christ, Angelika; Bruxner, Tim; Cloonan, Nicole; Kolle, Gabriel; Newell, Felicity; Pinese, Mark; Mead, R Scott; Humphris, Jeremy L; Kaplan, Warren; Jones, Marc D; Colvin, Emily K; Nagrial, Adnan M; Humphrey, Emily S; Chou, Angela; Chin, Venessa T; Chantrill, Lorraine A; Mawson, Amanda; Samra, Jaswinder S; Kench, James G; Lovell, Jessica A; Daly, Roger J; Merrett, Neil D; Toon, Christopher; Epari, Krishna; Nguyen, Nam Q; Barbour, Andrew; Zeps, Nikolajs; Kakkar, Nipun; Zhao, Fengmei; Wu, Yuan Qing; Wang, Min; Muzny, Donna M; Fisher, William E; Brunicardi, F Charles; Hodges, Sally E; Reid, Jeffrey G; Drummond, Jennifer; Chang, Kyle; Han, Yi; Lewis, Lora R; Dinh, Huyen; Buhay, Christian J; Beck, Timothy; Timms, Lee; Sam, Michelle; Begley, Kimberly; Brown, Andrew; Pai, Deepa; Panchal, Ami; Buchner, Nicholas; De Borja, Richard; Denroche, Robert E; Yung, Christina K; Serra, Stefano; Onetto, Nicole; Mukhopadhyay, Debabrata; Tsao, Ming-Sound; Shaw, Patricia A; Petersen, Gloria M; Gallinger, Steven; Hruban, Ralph H; Maitra, Anirban; Iacobuzio-Donahue, Christine A; Schulick, Richard D; Wolfgang, Christopher L; Morgan, Richard A; Lawlor, Rita T; Capelli, Paola; Corbo, Vincenzo; Scardoni, Maria; Tortora, Giampaolo; Tempero, Margaret A; Mann, Karen M; Jenkins, Nancy A; Perez-Mancera, Pedro A; Adams, David J; Largaespada, David A; Wessels, Lodewyk F A; Rust, Alistair G; Stein, Lincoln D; Tuveson, David A; Copeland, Neal G; Musgrove, Elizabeth A; Scarpa, Aldo; Eshleman, James R; Hudson, Thomas J; Sutherland, Robert L; Wheeler, David A; Pearson, John V; McPherson, John D; Gibbs, Richard A; Grimmond, Sean M

    2012-11-15

    Pancreatic cancer is a highly lethal malignancy with few effective therapies. We performed exome sequencing and copy number analysis to define genomic aberrations in a prospectively accrued clinical cohort (n = 142) of early (stage I and II) sporadic pancreatic ductal adenocarcinoma. Detailed analysis of 99 informative tumours identified substantial heterogeneity with 2,016 non-silent mutations and 1,628 copy-number variations. We define 16 significantly mutated genes, reaffirming known mutations (KRAS, TP53, CDKN2A, SMAD4, MLL3, TGFBR2, ARID1A and SF3B1), and uncover novel mutated genes including additional genes involved in chromatin modification (EPC1 and ARID2), DNA damage repair (ATM) and other mechanisms (ZIM2, MAP2K4, NALCN, SLC16A4 and MAGEA6). Integrative analysis with in vitro functional data and animal models provided supportive evidence for potential roles for these genetic aberrations in carcinogenesis. Pathway-based analysis of recurrently mutated genes recapitulated clustering in core signalling pathways in pancreatic ductal adenocarcinoma, and identified new mutated genes in each pathway. We also identified frequent and diverse somatic aberrations in genes described traditionally as embryonic regulators of axon guidance, particularly SLIT/ROBO signalling, which was also evident in murine Sleeping Beauty transposon-mediated somatic mutagenesis models of pancreatic cancer, providing further supportive evidence for the potential involvement of axon guidance genes in pancreatic carcinogenesis.

  5. Midline governs axon pathfinding by coordinating expression of two major guidance systems.

    Science.gov (United States)

    Liu, Qing-Xin; Hiramoto, Masaki; Ueda, Hitoshi; Gojobori, Takashi; Hiromi, Yasushi; Hirose, Susumu

    2009-05-15

    Formation of the neural network requires concerted action of multiple axon guidance systems. How neurons orchestrate expression of multiple guidance genes is poorly understood. Here, we show that Drosophila T-box protein Midline controls expression of genes encoding components of two major guidance systems: Frazzled, ROBO, and Slit. In midline mutant, expression of all these molecules are reduced, resulting in severe axon guidance defects, whereas misexpression of Midline induces their expression. Midline is present on the promoter regions of these genes, indicating that Midline controls transcription directly. We propose that Midline controls axon pathfinding through coordinating the two guidance systems.

  6. Gogo receptor contributes to retinotopic map formation and prevents R1-6 photoreceptor axon bundling.

    Directory of Open Access Journals (Sweden)

    Irina Hein

    Full Text Available BACKGROUND: Topographic maps form the basis of neural processing in sensory systems of both vertebrate and invertebrate species. In the Drosophila visual system, neighboring R1-R6 photoreceptor axons innervate adjacent positions in the first optic ganglion, the lamina, and thereby represent visual space as a continuous map in the brain. The mechanisms responsible for the establishment of retinotopic maps remain incompletely understood. RESULTS: Here, we show that the receptor Golden goal (Gogo is required for R axon lamina targeting and cartridge elongation in a partially redundant fashion with local guidance cues provided by neighboring axons. Loss of function of Gogo in large clones of R axons results in aberrant R1-R6 fascicle spacing. Gogo affects target cartridge selection only indirectly as a consequence of the disordered lamina map. Interestingly, small clones of gogo deficient R axons perfectly integrate into a proper retinotopic map suggesting that surrounding R axons of the same or neighboring fascicles provide complementary spatial guidance. Using single photoreceptor type rescue, we show that Gogo expression exclusively in R8 cells is sufficient to mediate targeting of all photoreceptor types in the lamina. Upon lamina targeting and cartridge selection, R axons elongate within their individual cartridges. Interestingly, here Gogo prevents bundling of extending R1-6 axons. CONCLUSION: Taken together, we propose that Gogo contributes to retinotopic map formation in the Drosophila lamina by controlling the distribution of R1-R6 axon fascicles. In a later developmental step, the regular position of R1-R6 axons along the lamina plexus is crucial for target cartridge selection. During cartridge elongation, Gogo allows R1-R6 axons to extend centrally in the lamina cartridge.

  7. Slit/Robo-mediated axon guidance in Tribolium and Drosophila: divergent genetic programs build insect nervous systems.

    Science.gov (United States)

    Evans, Timothy A; Bashaw, Greg J

    2012-03-01

    As the complexity of animal nervous systems has increased during evolution, developmental control of neuronal connectivity has become increasingly refined. How has functional diversification within related axon guidance molecules contributed to the evolution of nervous systems? To address this question, we explore the evolution of functional diversity within the Roundabout (Robo) family of axon guidance receptors. In Drosophila, Robo and Robo2 promote midline repulsion, while Robo2 and Robo3 specify the position of longitudinal axon pathways. The Robo family has expanded by gene duplication in insects; robo2 and robo3 exist as distinct genes only within dipterans, while other insects, like the flour beetle Tribolium castaneum, retain an ancestral robo2/3 gene. Both Robos from Tribolium can mediate midline repulsion in Drosophila, but unlike the fly Robos cannot be down-regulated by Commissureless. The overall architecture and arrangement of longitudinal pathways are remarkably conserved in Tribolium, despite it having only two Robos. Loss of TcSlit causes midline collapse of axons in the beetle, a phenotype recapitulated by simultaneous knockdown of both Robos. Single gene knockdowns reveal that beetle Robos have specialized axon guidance functions: TcRobo is dedicated to midline repulsion, while TcRobo2/3 also regulates longitudinal pathway formation. TcRobo2/3 knockdown reproduces aspects of both Drosophila robo2 and robo3 mutants, suggesting that TcRobo2/3 has two functions that in Drosophila are divided between Robo2 and Robo3. The ability of Tribolium to organize longitudinal axons into three discrete medial-lateral zones with only two Robo receptors demonstrates that beetle and fly achieve equivalent developmental outcomes using divergent genetic programs.

  8. Convergent differential regulation of SLIT-ROBO axon guidance genes in the brains of vocal learners.

    Science.gov (United States)

    Wang, Rui; Chen, Chun-Chun; Hara, Erina; Rivas, Miriam V; Roulhac, Petra L; Howard, Jason T; Chakraborty, Mukta; Audet, Jean-Nicolas; Jarvis, Erich D

    2015-04-15

    Only a few distantly related mammals and birds have the trait of complex vocal learning, which is the ability to imitate novel sounds. This ability is critical for speech acquisition and production in humans, and is attributed to specialized forebrain vocal control circuits that have several unique connections relative to adjacent brain circuits. As a result, it has been hypothesized that there could exist convergent changes in genes involved in neural connectivity of vocal learning circuits. In support of this hypothesis, expanding on our related study (Pfenning et al. [2014] Science 346: 1256846), here we show that the forebrain part of this circuit that makes a relatively rare direct connection to brainstem vocal motor neurons in independent lineages of vocal learning birds (songbird, parrot, and hummingbird) has specialized regulation of axon guidance genes from the SLIT-ROBO molecular pathway. The SLIT1 ligand was differentially downregulated in the motor song output nucleus that makes the direct projection, whereas its receptor ROBO1 was developmentally upregulated during critical periods for vocal learning. Vocal nonlearning bird species and male mice, which have much more limited vocal plasticity and associated circuits, did not show comparable specialized regulation of SLIT-ROBO genes in their nonvocal motor cortical regions. These findings are consistent with SLIT and ROBO gene dysfunctions associated with autism, dyslexia, and speech sound language disorders and suggest that convergent evolution of vocal learning was associated with convergent changes in the SLIT-ROBO axon guidance pathway.

  9. TIPsy tour guides: How microtubule plus-end tracking proteins (+TIPs facilitate axon guidance

    Directory of Open Access Journals (Sweden)

    Elizabeth A Bearce

    2015-06-01

    Full Text Available The growth cone is a dynamic cytoskeletal vehicle, which drives the end of a developing axon. It serves to interpret and navigate through the complex landscape and guidance cues of the early nervous system. The growth cone’s distinctive cytoskeletal organization offers a fascinating platform to study how extracellular cues can be translated into mechanical outgrowth and turning behaviors. While many studies of cell motility highlight the importance of actin networks in signaling, adhesion, and propulsion, both seminal and emerging works in the field have highlighted a unique and necessary role for microtubules in growth cone navigation. Here, we focus on the role of singular pioneer microtubules, which extend into the growth cone periphery and are regulated by a diverse family of microtubule plus-end tracking proteins (+TIPs. These +TIPs accumulate at the dynamic ends of microtubules, where they are well-positioned to encounter and respond to key signaling events downstream of guidance receptors, catalyzing immediate changes in microtubule stability and actin cross-talk, that facilitate both axonal outgrowth and turning events.

  10. Regulation of Axonal Midline Guidance by Prolyl 4-Hydroxylation in Caenorhabditis elegans

    DEFF Research Database (Denmark)

    Torpe, Nanna; Pocock, Roger David John

    2014-01-01

    Neuronal wiring during development requires that the growth cones of axons and dendrites are correctly guided to their appropriate targets. As in other animals, axon growth cones in Caenorhabditis elegans integrate information in their extracellular environment via interactions among transiently......, little is known of its importance in the control of axon guidance. In a screen of prolyl 4-hydroxylase (P4H) mutants, we found that genetic removal of a specific P4H subunit, DPY-18, causes dramatic defects in C. elegans neuroanatomy. In dpy-18 mutant animals, the axons of specific ventral nerve cord...

  11. The Alzheimer's β-secretase enzyme BACE1 is required for accurate axon guidance of olfactory sensory neurons and normal glomerulus formation in the olfactory bulb

    Directory of Open Access Journals (Sweden)

    Rajapaksha Tharinda W

    2011-12-01

    Full Text Available Abstract Background The β-secretase, β-site amyloid precursor protein cleaving enzyme 1 (BACE1, is a prime therapeutic target for lowering cerebral β-amyloid (Aβ levels in Alzheimer's disease (AD. Clinical development of BACE1 inhibitors is being intensely pursued. However, little is known about the physiological functions of BACE1, and the possibility exists that BACE1 inhibition may cause mechanism-based side effects. Indeed, BACE1-/- mice exhibit a complex neurological phenotype. Interestingly, BACE1 co-localizes with presynaptic neuronal markers, indicating a role in axons and/or terminals. Moreover, recent studies suggest axon guidance molecules are potential BACE1 substrates. Here, we used a genetic approach to investigate the function of BACE1 in axon guidance of olfactory sensory neurons (OSNs, a well-studied model of axon targeting in vivo. Results We bred BACE1-/- mice with gene-targeted mice in which GFP is expressed from the loci of two odorant-receptors (ORs, MOR23 and M72, and olfactory marker protein (OMP to produce offspring that were heterozygous for MOR23-GFP, M72-GFP, or OMP-GFP and were either BACE1+/+ or BACE1-/-. BACE1-/- mice had olfactory bulbs (OBs that were smaller and weighed less than OBs of BACE1+/+ mice. In wild-type mice, BACE1 was present in OSN axon terminals in OB glomeruli. In whole-mount preparations and tissue sections, many OB glomeruli from OMP-GFP; BACE1-/- mice were malformed compared to wild-type glomeruli. MOR23-GFP; BACE1-/- mice had an irregular MOR23 glomerulus that was innervated by randomly oriented, poorly fasciculated OSN axons compared to BACE1+/+ mice. Most importantly, M72-GFP; BACE1-/- mice exhibited M72 OSN axons that were mis-targeted to ectopic glomeruli, indicating impaired axon guidance in BACE1-/- mice. Conclusions Our results demonstrate that BACE1 is required for the accurate targeting of OSN axons and the proper formation of glomeruli in the OB, suggesting a role for BACE1 in

  12. Effects of laminin blended with chitosan on axon guidance on patterned substrates

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, N; Guan, Y J; Chen, X B [Division of Biomedical Engineering, University of Saskatchewan, Saskatoon S7N 5A9 (Canada); Li, M G [Department of Mechanical Engineering, University of Saskatchewan, Saskatoon S7N 5A9 (Canada); Schreyer, D J, E-mail: niz504@mail.usask.c [Department of Anatomy and Cell Biology, Cameco MS Neuroscience Research Center, University of Saskatchewan, Saskatoon, S7K 0M7 (Canada)

    2010-12-15

    Axon guidance is a crucial consideration in the design of tissue scaffolds used to promote nerve regeneration. Here we investigate the combined use of laminin (a putative axon adhesion and guidance molecule) and chitosan (a leading candidate base material for the construction of scaffolds) for promoting axon guidance in cultured adult dorsal root ganglion (DRG) neurons. Using a dispensing-based rapid prototyping (DBRP) technique, two-dimensional grid patterns were created by dispensing chitosan or laminin-blended chitosan substrate strands oriented in orthogonal directions. In vitro experiments illustrated DRG neurites on these patterns preferentially grew upon and followed the laminin-blended chitosan pathways. These results suggest that an orientation of neurite growth can be achieved in an artificially patterned substrate by creating selectively biofunctional pathways. The DBRP technique may provide improved strategies for the use of biofunctional pathways in the design of three-dimensional scaffolds for guidance of nerve repair.

  13. Receptor Tyrosine Kinases: Molecular Switches Regulating CNS Axon Regeneration

    Directory of Open Access Journals (Sweden)

    Vasanthy Vigneswara

    2012-01-01

    Full Text Available The poor or lack of injured adult central nervous system (CNS axon regeneration results in devastating consequences and poor functional recovery. The interplay between the intrinsic and extrinsic factors contributes to robust inhibition of axon regeneration of injured CNS neurons. The insufficient or lack of trophic support for injured neurons is considered as one of the major obstacles contributing to their failure to survive and regrow their axons after injury. In the CNS, many of the signalling pathways associated with neuronal survival and axon regeneration are regulated by several classes of receptor tyrosine kinases (RTK that respond to a variety of ligands. This paper highlights and summarises the most relevant recent findings pertinent to different classes of the RTK family of molecules, with a particular focus on elucidating their role in CNS axon regeneration.

  14. Motor Axon Pathfinding

    OpenAIRE

    Bonanomi, Dario; Pfaff, Samuel L

    2010-01-01

    Motor neurons are functionally related, but represent a diverse collection of cells that show strict preferences for specific axon pathways during embryonic development. In this article, we describe the ligands and receptors that guide motor axons as they extend toward their peripheral muscle targets. Motor neurons share similar guidance molecules with many other neuronal types, thus one challenge in the field of axon guidance has been to understand how the vast complexity of brain connection...

  15. Fcγ receptor-mediated inflammation inhibits axon regeneration.

    Directory of Open Access Journals (Sweden)

    Gang Zhang

    Full Text Available Anti-glycan/ganglioside antibodies are the most common immune effectors found in patients with Guillain-Barré Syndrome, which is a peripheral autoimmune neuropathy. We previously reported that disease-relevant anti-glycan autoantibodies inhibited axon regeneration, which echo the clinical association of these antibodies and poor recovery in Guillain-Barré Syndrome. However, the specific molecular and cellular elements involved in this antibody-mediated inhibition of axon regeneration are not previously defined. This study examined the role of Fcγ receptors and macrophages in the antibody-mediated inhibition of axon regeneration. A well characterized antibody passive transfer sciatic nerve crush and transplant models were used to study the anti-ganglioside antibody-mediated inhibition of axon regeneration in wild type and various mutant and transgenic mice with altered expression of specific Fcγ receptors and macrophage/microglia populations. Outcome measures included behavior, electrophysiology, morphometry, immunocytochemistry, quantitative real-time PCR, and western blotting. We demonstrate that the presence of autoantibodies, directed against neuronal/axonal cell surface gangliosides, in the injured mammalian peripheral nerves switch the proregenerative inflammatory environment to growth inhibitory milieu by engaging specific activating Fcγ receptors on recruited monocyte-derived macrophages to cause severe inhibition of axon regeneration. Our data demonstrate that the antibody orchestrated Fcγ receptor-mediated switch in inflammation is one mechanism underlying inhibition of axon regeneration. These findings have clinical implications for nerve repair and recovery in antibody-mediated immune neuropathies. Our results add to the complexity of axon regeneration in injured peripheral and central nervous systems as adverse effects of B cells and autoantibodies on neural injury and repair are increasingly recognized.

  16. Extracellular matrix molecules play diverse roles in the growth and guidance of central nervous system axons

    Directory of Open Access Journals (Sweden)

    M.A. Pires-Neto

    1999-05-01

    Full Text Available Axon growth and guidance represent complex biological processes in which probably intervene diverse sets of molecular cues that allow for the appropriate wiring of the central nervous system (CNS. The extracellular matrix (ECM represents a major contributor of molecular signals either diffusible or membrane-bound that may regulate different stages of neural development. Some of the brain ECM molecules form tridimensional structures (tunnels and boundaries that appear during time- and space-regulated events, possibly playing relevant roles in the control of axon elongation and pathfinding. This short review focuses mainly on the recognized roles played by proteoglycans, laminin, fibronectin and tenascin in axonal development during ontogenesis.

  17. Drosophila Ryks and their roles in axon and muscle guidance

    NARCIS (Netherlands)

    Lahaye, Liza Lucia

    2015-01-01

    In the last decade it has become clear that a number of the molecular mechanisms that are required for proper navigation of axons in complex nervous systems are also employed to guide muscles to their appropriate attachment sites. Among the gene families that mediate these diverse processes is the R

  18. The Drosophila immunoglobulin gene turtle encodes guidance molecules involved in axon pathfinding

    Directory of Open Access Journals (Sweden)

    Al-Anzi Bader

    2009-08-01

    Full Text Available Abstract Background Neuronal growth cones follow specific pathways over long distances in order to reach their appropriate targets. Research over the past 15 years has yielded a large body of information concerning the molecules that regulate this process. Some of these molecules, such as the evolutionarily conserved netrin and slit proteins, are expressed in the embryonic midline, an area of extreme importance for early axon pathfinding decisions. A general model has emerged in which netrin attracts commissural axons towards the midline while slit forces them out. However, a large number of commissural axons successfully cross the midline even in the complete absence of netrin signaling, indicating the presence of a yet unidentified midline attractant. Results The evolutionarily conserved Ig proteins encoded by the turtle/Dasm1 genes are found in Drosophila, Caenorhabditis elegans, and mammals. In Drosophila the turtle gene encodes five proteins, two of which are diffusible, that are expressed in many areas, including the vicinity of the midline. Using both molecular null alleles and transgenic expression of the different isoforms, we show that the turtle encoded proteins function as non-cell autonomous axonal attractants that promote midline crossing via a netrin-independent mechanism. turtle mutants also have either stalled or missing axon projections, while overexpression of the different turtle isoforms produces invasive neurons and branching axons that do not respect the histological divisions of the nervous system. Conclusion Our findings indicate that the turtle proteins function as axon guidance cues that promote midline attraction, axon branching, and axonal invasiveness. The latter two capabilities are required by migrating axons to explore densely packed targets.

  19. Evidence for Dysregulation of Axonal Growth and Guidance in the Etiology of ASD

    Directory of Open Access Journals (Sweden)

    Kathryn eMcFadden

    2013-10-01

    Full Text Available Current theories concerning the cause of autism spectrum disorders (ASDs have converged on the concept of abnormal development of brain connectivity. This concept is supported by accumulating evidence from functional imaging, DTI, and high definition fiber tracking (HDFT studies which suggest altered microstructure in the axonal tracts connecting cortical areas may underly many of the cognitive manifestations of ASD. Additionally, large-scale genomic studies implicate numerous gene candidates known or suspected to mediate neuritic outgrowth and axonal guidance in fetal and perinatal life. Neuropathological observations in postmortem ASD brain samples further support this model and include subtle disturbances of cortical lamination and subcortical axonal morphology. Of note is the relatively common finding of poor differentiation of the gray-white junction associated with an excess superficial white matter or interstitial neurons (INs. INs are thought to be remnants of the fetal subplate, a transient structure which plays a key role in the guidance and morphogenesis of thalamocortical and cortico-cortical connections and the organization of cortical columnar architecture. While not discounting the importance of synaptic dysfunction in the etiology of ASD, this paper will briefly review the cortical abnormalities and genetic evidence supporting a model of dysregulated axonal growth and guidance as key developmental processes underlying the clinical manifestations of ASD.

  20. The fax-1 nuclear hormone receptor regulates axon pathfinding and neurotransmitter expression.

    Science.gov (United States)

    Much, J W; Slade, D J; Klampert, K; Garriga, G; Wightman, B

    2000-02-01

    Specification of neuron identity requires the activation of a number of discrete developmental programs. Among these is pathway selection by growth cones: in order for a neuron's growth cone to respond appropriately to guidance cues presented by other cells or the extracellular matrix, the neuron must express genes to mediate the response. The fax-1 gene of C. elegans is required for pathfinding of axons that extend along the ventral nerve cord. We show that fax-1 is also required for pathfinding of axons in the nerve ring, the largest nerve bundle in the nematode, and for normal expression of FMRFamide-like neurotransmitters in the AVK interneurons. The fax-1 gene encodes a member of the superfamily of nuclear hormone receptors and has a DNA-binding domain related to the human PNR and Drosophila Tailless proteins. We observe fax-1 expression in embryonic neurons, including the AVK interneurons, just prior to axon extension, but after neurogenesis. These data suggest that fax-1 coordinately regulates the transcription of genes that function in the selection of axon pathways, neurotransmitter expression and, perhaps, other aspects of the specification of neuron identity.

  1. A genomic pathway approach to a complex disease: axon guidance and Parkinson disease.

    Directory of Open Access Journals (Sweden)

    Timothy G Lesnick

    2007-06-01

    Full Text Available While major inroads have been made in identifying the genetic causes of rare Mendelian disorders, little progress has been made in the discovery of common gene variations that predispose to complex diseases. The single gene variants that have been shown to associate reproducibly with complex diseases typically have small effect sizes or attributable risks. However, the joint actions of common gene variants within pathways may play a major role in predisposing to complex diseases (the paradigm of complex genetics. The goal of this study was to determine whether polymorphism in a candidate pathway (axon guidance predisposed to a complex disease (Parkinson disease [PD]. We mined a whole-genome association dataset and identified single nucleotide polymorphisms (SNPs that were within axon-guidance pathway genes. We then constructed models of axon-guidance pathway SNPs that predicted three outcomes: PD susceptibility (odds ratio = 90.8, p = 4.64 x 10(-38, survival free of PD (hazards ratio = 19.0, p = 5.43 x 10(-48, and PD age at onset (R(2 = 0.68, p = 1.68 x 10(-51. By contrast, models constructed from thousands of random selections of genomic SNPs predicted the three PD outcomes poorly. Mining of a second whole-genome association dataset and mining of an expression profiling dataset also supported a role for many axon-guidance pathway genes in PD. These findings could have important implications regarding the pathogenesis of PD. This genomic pathway approach may also offer insights into other complex diseases such as Alzheimer disease, diabetes mellitus, nicotine and alcohol dependence, and several cancers.

  2. The neural adhesion molecule TAG-1 modulates responses of sensory axons to diffusible guidance signals.

    Science.gov (United States)

    Law, Chris O; Kirby, Rebecca J; Aghamohammadzadeh, Soheil; Furley, Andrew J W

    2008-08-01

    When the axons of primary sensory neurons project into the embryonic mammalian spinal cord, they bifurcate and extend rostrocaudally before sending collaterals to specific laminae according to neuronal subclass. The specificity of this innervation has been suggested to be the result both of differential sensitivity to chemorepellants expressed in the ventral spinal cord and of the function of Ig-like neural cell adhesion molecules in the dorsal horn. The relationship between these mechanisms has not been addressed. Focussing on the pathfinding of TrkA+ NGF-dependent axons, we demonstrate for the first time that their axons project prematurely into the dorsal horn of both L1 and TAG-1 knockout mice. We show that axons lacking TAG-1, similar to those lacking L1, are insensitive to wild-type ventral spinal cord (VSC)-derived chemorepellants, indicating that adhesion molecule function is required in the axons, and that this loss of response is explained in part by loss of response to Sema3A. We present evidence that TAG-1 affects sensitivity to Sema3A by binding to L1 and modulating the endocytosis of the L1/neuropilin 1 Sema3A receptor complex. However, TAG-1 appears to affect sensitivity to other VSC-derived chemorepellants via an L1-independent mechanism. We suggest that this dependence of chemorepellant sensitivity on the functions of combinations of adhesion molecules is important to ensure that axons project via specific pathways before extending to their final targets. PMID:18550718

  3. Morphogenesis of the C. elegans Intestine Involves Axon Guidance Genes.

    Science.gov (United States)

    Asan, Alparsan; Raiders, Stephan A; Priess, James R

    2016-04-01

    Genetic and molecular studies have provided considerable insight into how various tissue progenitors are specified in early embryogenesis, but much less is known about how those progenitors create three-dimensional tissues and organs. The C. elegans intestine provides a simple system for studying how a single progenitor, the E blastomere, builds an epithelial tube of 20 cells. As the E descendants divide, they form a primordium that transitions between different shapes over time. We used cell contours, traced from confocal optical z-stacks, to build a 3D graphic reconstruction of intestine development. The reconstruction revealed several new aspects of morphogenesis that extend and clarify previous observations. The first 8 E descendants form a plane of four right cells and four left cells; the plane arises through oriented cell divisions and VANG-1/Van Gogh-dependent repositioning of any non-planar cells. LIN-12/Notch signaling affects the left cells in the E8 primordium, and initiates later asymmetry in cell packing. The next few stages involve cell repositioning and intercalation events that shuttle cells to their final positions, like shifting blocks in a Rubik's cube. Repositioning involves breaking and replacing specific adhesive contacts, and some of these events involve EFN-4/Ephrin, MAB-20/semaphorin-2a, and SAX-3/Robo. Once cells in the primordium align along a common axis and in the correct order, cells at the anterior end rotate clockwise around the axis of the intestine. The anterior rotation appears to align segments of the developing lumen into a continuous structure, and requires the secreted ligand UNC-6/netrin, the receptor UNC-40/DCC, and an interacting protein called MADD-2. Previous studies showed that rotation requires a second round of LIN-12/Notch signaling in cells on the right side of the primordium, and we show that MADD-2-GFP appears to be downregulated in those cells.

  4. The discovery of the growth cone and its influence on the study of axon guidance

    Directory of Open Access Journals (Sweden)

    Elisa eTamariz

    2015-05-01

    Full Text Available For over a century, there has been a great deal of interest in understanding how neural connectivity is established during development and regeneration. Interest in the latter arises from the possibility that knowledge of this process can be used to reestablish lost connections after lesion or neurodegeneration. At the end of the XIX century, Santiago Ramón y Cajal discovered that the distal tip of growing axons contained a structure that he called the growth cone. He proposed that this structure enabled the axon’s oriented growth in response to attractants, now known as chemotropic molecules. He further proposed that the physical properties of the surrounding tissues could influence the growth cone and the direction of growth. This seminal discovery afforded a plausible explanation for directed axonal growth and has led to the discovery of axon guidance mechanisms that include diffusible attractants and repellants and guidance cues anchored to cell membranes or extracellular matrix. In this review the major events in the development of this field are discussed.

  5. Repulsive axon guidance by Draxin is mediated by protein Kinase B (Akt), glycogen synthase kinase-3β (GSK-3β) and microtubule-associated protein 1B.

    Science.gov (United States)

    Meli, Rajeshwari; Weisová, Petronela; Propst, Friedrich

    2015-01-01

    Draxin is an important axon guidance cue necessary for the formation of forebrain commissures including the corpus callosum, but the molecular details of draxin signaling are unknown. To unravel how draxin signals are propagated we used murine cortical neurons and genetic and pharmacological approaches. We found that draxin-induced growth cone collapse critically depends on draxin receptors (deleted in colorectal cancer, DCC), inhibition of protein kinase B/Akt, activation of GSK-3β (glycogen synthase kinase-3β) and the presence of microtubule-associated protein MAP1B. This study, for the first time elucidates molecular events in draxin repulsion, links draxin and DCC to MAP1B and identifies a novel MAP1B-depenent GSK-3β pathway essential for chemo-repulsive axon guidance cue signaling.

  6. Regulation of action potential waveforms by axonal GABAA receptors in cortical pyramidal neurons.

    Directory of Open Access Journals (Sweden)

    Yang Xia

    Full Text Available GABAA receptors distributed in somatodendritic compartments play critical roles in regulating neuronal activities, including spike timing and firing pattern; however, the properties and functions of GABAA receptors at the axon are still poorly understood. By recording from the cut end (bleb of the main axon trunk of layer -5 pyramidal neurons in prefrontal cortical slices, we found that currents evoked by GABA iontophoresis could be blocked by picrotoxin, indicating the expression of GABAA receptors in axons. Stationary noise analysis revealed that single-channel properties of axonal GABAA receptors were similar to those of somatic receptors. Perforated patch recording with gramicidin revealed that the reversal potential of the GABA response was more negative than the resting membrane potential at the axon trunk, suggesting that GABA may hyperpolarize the axonal membrane potential. Further experiments demonstrated that the activation of axonal GABAA receptors regulated the amplitude and duration of action potentials (APs and decreased the AP-induced Ca2+ transients at the axon. Together, our results indicate that the waveform of axonal APs and the downstream Ca2+ signals are modulated by axonal GABAA receptors.

  7. Expression of the Wnt signaling system in central nervous system axon guidance and regeneration

    Directory of Open Access Journals (Sweden)

    Edmund eHollis

    2012-02-01

    Full Text Available Wnt signaling is essential for axon wiring throughout the development of the nervous system in vertebrates and invertebrates. In vertebrates, Wnts are expressed in gradients that span the entire anterior-posterior axis in the spinal cord and the medial-lateral axis in the superior colliculus. In the brainstem, Wnts are expressed in more complex gradients along the anterior-posterior axis. These gradients provide directional information for axon pathfinding and positional information for topographic mapping and are detected by cell polarity signaling pathways. The gradient expression of Wnts and the coordinated expression of Wnt signaling systems are regulated by mechanisms which are currently unknown. Injury to the adult spinal cord results in the re-induction of Wnts in multiple cell types around the lesion site and their signaling system in injured axons. Reinduced Wnts form gradients around the lesion site, with the lesion site being the peak. The reinduced Wnts may be responsible for the well-known retraction of descending motor axons through the atypical kinase receptor Ryk. Wnt signaling is an appealing therapeutic target for CNS repair. The mechanisms regulating the reinduction will be informative for therapeutic design.

  8. Complete Loss of Netrin-1 Results in Embryonic Lethality and Severe Axon Guidance Defects without Increased Neural Cell Death

    Directory of Open Access Journals (Sweden)

    Jenea M. Bin

    2015-08-01

    Full Text Available Netrin-1 regulates cell migration and adhesion during the development of the nervous system, vasculature, lung, pancreas, muscle, and mammary gland. It is also proposed to function as a dependence ligand that inhibits apoptosis; however, studies disagree regarding whether netrin-1 loss-of-function mice exhibit increased cell death. Furthermore, previously studied netrin-1 loss-of-function gene-trap mice express a netrin-1-β-galactosidase protein chimera with potential for toxic gain-of-function effects, as well as a small amount of wild-type netrin-1 protein. To unambiguously assess loss of function, we generated netrin-1 floxed and netrin-1 null mouse lines. Netrin-1−/− mice die earlier and exhibit more severe axon guidance defects than netrin-1 gene-trap mice, revealing that complete loss of function is more severe than previously reported. Netrin-1−/− embryos also exhibit increased expression of the netrin receptors DCC and neogenin that are proposed dependence receptors; however, increased apoptosis was not detected, inconsistent with netrin-1 being an essential dependence receptor ligand in the embryonic spinal cord.

  9. Axon guidance of sympathetic neurons to cardiomyocytes by glial cell line-derived neurotrophic factor (GDNF.

    Directory of Open Access Journals (Sweden)

    Keiko Miwa

    Full Text Available Molecular signaling of cardiac autonomic innervation is an unresolved issue. Here, we show that glial cell line-derived neurotrophic factor (GDNF promotes cardiac sympathetic innervation in vitro and in vivo. In vitro, ventricular myocytes (VMs and sympathetic neurons (SNs isolated from neonatal rat ventricles and superior cervical ganglia were cultured at a close distance. Then, morphological and functional coupling between SNs and VMs was assessed in response to GDNF (10 ng/ml or nerve growth factor (50 ng/ml. As a result, fractions of neurofilament-M-positive axons and synapsin-I-positive area over the surface of VMs were markedly increased with GDNF by 9-fold and 25-fold, respectively, compared to control without neurotrophic factors. Pre- and post-synaptic stimulation of β1-adrenergic receptors (BAR with nicotine and noradrenaline, respectively, resulted in an increase of the spontaneous beating rate of VMs co-cultured with SNs in the presence of GDNF. GDNF overexpressing VMs by adenovirus vector (AdGDNF-VMs attracted more axons from SNs compared with mock-transfected VMs. In vivo, axon outgrowth toward the denervated myocardium in adult rat hearts after cryoinjury was also enhanced significantly by adenovirus-mediated GDNF overexpression. GDNF acts as a potent chemoattractant for sympathetic innervation of ventricular myocytes, and is a promising molecular target for regulation of cardiac function in diseased hearts.

  10. Axon guidance of sympathetic neurons to cardiomyocytes by glial cell line-derived neurotrophic factor (GDNF).

    Science.gov (United States)

    Miwa, Keiko; Lee, Jong-Kook; Takagishi, Yoshiko; Opthof, Tobias; Fu, Xianming; Hirabayashi, Masumi; Watabe, Kazuhiko; Jimbo, Yasuhiko; Kodama, Itsuo; Komuro, Issei

    2013-01-01

    Molecular signaling of cardiac autonomic innervation is an unresolved issue. Here, we show that glial cell line-derived neurotrophic factor (GDNF) promotes cardiac sympathetic innervation in vitro and in vivo. In vitro, ventricular myocytes (VMs) and sympathetic neurons (SNs) isolated from neonatal rat ventricles and superior cervical ganglia were cultured at a close distance. Then, morphological and functional coupling between SNs and VMs was assessed in response to GDNF (10 ng/ml) or nerve growth factor (50 ng/ml). As a result, fractions of neurofilament-M-positive axons and synapsin-I-positive area over the surface of VMs were markedly increased with GDNF by 9-fold and 25-fold, respectively, compared to control without neurotrophic factors. Pre- and post-synaptic stimulation of β1-adrenergic receptors (BAR) with nicotine and noradrenaline, respectively, resulted in an increase of the spontaneous beating rate of VMs co-cultured with SNs in the presence of GDNF. GDNF overexpressing VMs by adenovirus vector (AdGDNF-VMs) attracted more axons from SNs compared with mock-transfected VMs. In vivo, axon outgrowth toward the denervated myocardium in adult rat hearts after cryoinjury was also enhanced significantly by adenovirus-mediated GDNF overexpression. GDNF acts as a potent chemoattractant for sympathetic innervation of ventricular myocytes, and is a promising molecular target for regulation of cardiac function in diseased hearts.

  11. Trafifc lights for axon growth:proteoglycans and their neuronal receptors

    Institute of Scientific and Technical Information of China (English)

    Yingjie Shen

    2014-01-01

    Axon growth is a central event in the development and post-injury plasticity of the nervous system. Growing axons encounter a wide variety of environmental instructions. Much like trafifc lights in controlling the migrating axons, chondroitin sulfate proteoglycans (CSPGs) and hepa-ran sulfate proteoglycans (HSPGs) often lead to“stop”and“go”growth responses in the axons, respectively. Recently, the LAR family and NgR family molecules were identified as neuronal receptors for CSPGs and HSPGs. These discoveries provided molecular tools for further study of mechanisms underlying axon growth regulation. More importantly, the identiifcation of these proteoglycan receptors offered potential therapeutic targets for promoting post-injury axon re-generation.

  12. Vomeronasal receptors: from monogenic expression to axon guidance

    OpenAIRE

    Capello, Luca

    2009-01-01

    Le système olfactif fait face à un devoir remarquable: extraire une information cohérente d'un monde qu'il n'a jamais rencontré. Les outils moléculaires lui permettant d'effectuer cette tâche sont représentés par différents types de chimiorécepteurs, qui sont exprimés par des neurones sensoriels localisés dans le nez. Ceux-ci sont codés par de très grandes familles de gènes, et incluent les récepteurs à odeurs (plus de 1000 gènes chez la souris), les récepteurs TAAR, V1R et V2R, et les récept...

  13. Odorant receptors regulate the final glomerular coalescence of olfactory sensory neuron axons.

    Science.gov (United States)

    Rodriguez-Gil, Diego J; Bartel, Dianna L; Jaspers, Austin W; Mobley, Arie S; Imamura, Fumiaki; Greer, Charles A

    2015-05-01

    Odorant receptors (OR) are strongly implicated in coalescence of olfactory sensory neuron (OSN) axons and the formation of olfactory bulb (OB) glomeruli. However, when ORs are first expressed relative to basal cell division and OSN axon extension is unknown. We developed an in vivo fate-mapping strategy that enabled us to follow OSN maturation and axon extension beginning at basal cell division. In parallel, we mapped the molecular development of OSNs beginning at basal cell division, including the onset of OR expression. Our data show that ORs are first expressed around 4 d following basal cell division, 24 h after OSN axons have reached the OB. Over the next 6+ days the OSN axons navigate the OB nerve layer and ultimately coalesce in glomeruli. These data provide a previously unidentified perspective on the role of ORs in homophilic OSN axon adhesion and lead us to propose a new model dividing axon extension into two phases. Phase I is OR-independent and accounts for up to 50% of the time during which axons approach the OB and begin navigating the olfactory nerve layer. Phase II is OR-dependent and concludes as OSN axons coalesce in glomeruli.

  14. Exosomes mediate cell contact-independent ephrin-Eph signaling during axon guidance.

    Science.gov (United States)

    Gong, Jingyi; Körner, Roman; Gaitanos, Louise; Klein, Rüdiger

    2016-07-01

    The cellular release of membranous vesicles known as extracellular vesicles (EVs) or exosomes represents a novel mode of intercellular communication. Eph receptor tyrosine kinases and their membrane-tethered ephrin ligands have very important roles in such biologically diverse processes as neuronal development, plasticity, and pathological diseases. Until now, it was thought that ephrin-Eph signaling requires direct cell contact. Although the biological functions of ephrin-Eph signaling are well understood, our mechanistic understanding remains modest. Here we report the release of EVs containing Ephs and ephrins by different cell types, a process requiring endosomal sorting complex required for transport (ESCRT) activity and regulated by neuronal activity. Treatment of cells with purified EphB2(+) EVs induces ephrinB1 reverse signaling and causes neuronal axon repulsion. These results indicate a novel mechanism of ephrin-Eph signaling independent of direct cell contact and proteolytic cleavage and suggest the participation of EphB2(+) EVs in neural development and synapse physiology. PMID:27354374

  15. Endoplasmic reticulum sorting and kinesin-1 command the targeting of axonal GABAB receptors.

    Directory of Open Access Journals (Sweden)

    Viviana Valdés

    Full Text Available In neuronal cells the intracellular trafficking machinery controls the availability of neurotransmitter receptors at the plasma membrane, which is a critical determinant of synaptic strength. Metabotropic γ amino-butyric acid (GABA type B receptors (GABA(BRs are neurotransmitter receptors that modulate synaptic transmission by mediating the slow and prolonged responses to GABA. GABA(BRs are obligatory heteromers constituted by two subunits, GABA(BR1 and GABA(BR2. GABA(BR1a and GABA(BR1b are the most abundant subunit variants. GABA(BR1b is located in the somatodendritic domain whereas GABA(BR1a is additionally targeted to the axon. Sushi domains located at the N-terminus of GABA(BR1a constitute the only difference between both variants and are necessary and sufficient for axonal targeting. The precise targeting machinery and the organelles involved in sorting and transport have not been described. Here we demonstrate that GABA(BRs require the Golgi apparatus for plasma membrane delivery but that axonal sorting and targeting of GABA(BR1a operate in a pre-Golgi compartment. In the axon GABA(BR1a subunits are enriched in the endoplasmic reticulum (ER, and their dynamic behavior and colocalization with other secretory organelles like the ER-to-Golgi intermediate compartment (ERGIC suggest that they employ a local secretory route. The transport of axonal GABA(BR1a is microtubule-dependent and kinesin-1, a molecular motor of the kinesin family, determines axonal localization. Considering that progression of GABA(BRs through the secretory pathway is regulated by an ER retention motif our data contribute to understand the role of the axonal ER in non-canonical sorting and targeting of neurotransmitter receptors.

  16. Sensory axon guidance with semaphorin 6A and nerve growth factor in a biomimetic choice point model

    International Nuclear Information System (INIS)

    The direct effect of guidance cues on developing and regenerating axons in vivo is not fully understood, as the process involves a multiplicity of attractive and repulsive signals, presented both as soluble and membrane-bound ligands. A better understanding of axon guidance is critical to functional recovery following injury to the nervous system through improved outgrowth and mapping of damaged nerves. Due to their implications as inhibitors to central nervous system regeneration, we investigated the repulsive properties of semaphorin 6A and ephrin-B3 on E15 rat dorsal root ganglion explants, as well as possible interactions with soluble gradients of chemoattractive nerve growth factor (NGF). We employed a 3D biomimetic in vitro choice point model, which enabled the simple and rapid preparation of patterned gel growth matrices with quantifiable presentation of guidance cues in a specifiable manner that resembles the in vivo presentation of soluble and/or immobilized ligands. Neurites demonstrated an inhibitory response to immobilized Sema6A by lumbosacral dorsal root ganglion explants, while no such repulsion was observed for immobilized ephrin-B3 by explants at any spinal level. Interestingly, Sema6A inhibition could be partially attenuated in a concentration-dependent manner through the simultaneous presentation of soluble NGF gradients. The in vitro model described herein represents a versatile and valuable investigative tool in the quest for understanding developmental processes and improving regeneration following nervous system injury. (paper)

  17. Asymmetric axonal edge guidance: a new paradigm for building oriented neuronal networks.

    Science.gov (United States)

    Renault, Renaud; Durand, Jean-Baptiste; Viovy, Jean-Louis; Villard, Catherine

    2016-06-21

    We present a novel kind of directional axon guides for brain-on-a-chip applications. Contrarily to previous works, the directionality in our design is created by rerouting axons growing in the unwanted direction back to their original compartment while leaving the other growth direction unaffected. This design yields state-of-the-art levels of directionality without the disadvantages of previously reported technologies.

  18. Expression patterns of semaphorin7A and plexinC1 during rat neural development suggest roles in axon guidance and neuronal migration

    Directory of Open Access Journals (Sweden)

    Hellemons Anita JCGM

    2007-08-01

    Full Text Available Abstract Background Although originally identified as embryonic axon guidance cues, semaphorins are now known to regulate multiple, distinct, processes crucial for neuronal network formation including axon growth and branching, dendritic morphology, and neuronal migration. Semaphorin7A (Sema7A, the only glycosylphosphatidylinositol-anchored semaphorin, promotes axon growth in vitro and is required for the proper growth of the mouse lateral olfactory tract in vivo. Sema7A has been postulated to signal through two unrelated receptors, an RGD-dependent α1β1-integrin and a member of the plexin family, plexinC1. β1-integrins underlie Sema7A-mediated axon growth and Sema7A function in the immune system. Sema7A-plexinC1 interactions have also been implicated in immune system function, but the neuronal role of this ligand-receptor pair remains to be explored. To gain further insight into the function(s of Sema7A and plexinC1 during neural development, we present here a detailed analysis of Sema7A and plexinC1 expression in the developing rat nervous system. Results In situ hybridization revealed select expression of Sema7A and plexinC1 in multiple neuronal systems including: the olfactory system, the hypothalamo-hypophysial system, the hippocampus, the meso-diencephalic dopamine system, and the spinal cord. Within these systems, Sema7A and plexinC1 are often expressed in specific neuronal subsets. In general, Sema7A transcript levels increase significantly towards adulthood, whereas plexinC1 expression decreases as development proceeds. PlexinC1, but not Sema7A, is strongly expressed by distinct populations of migrating neurons. In addition to neuronal expression, Sema7A and plexinC1 transcripts were detected in oligodendrocytes and ependymal cells, respectively. Conclusion Sema7A and plexinC1 expression patterns are consistent with these proteins serving both cooperative and separate functions during neural development. The prominent expression of

  19. Expression patterns of semaphorin7A and plexinC1 during rat neural development suggest roles in axon guidance and neuronal migration

    Science.gov (United States)

    Pasterkamp, R Jeroen; Kolk, Sharon M; Hellemons, Anita JCGM; Kolodkin, Alex L

    2007-01-01

    Background Although originally identified as embryonic axon guidance cues, semaphorins are now known to regulate multiple, distinct, processes crucial for neuronal network formation including axon growth and branching, dendritic morphology, and neuronal migration. Semaphorin7A (Sema7A), the only glycosylphosphatidylinositol-anchored semaphorin, promotes axon growth in vitro and is required for the proper growth of the mouse lateral olfactory tract in vivo. Sema7A has been postulated to signal through two unrelated receptors, an RGD-dependent α1β1-integrin and a member of the plexin family, plexinC1. β1-integrins underlie Sema7A-mediated axon growth and Sema7A function in the immune system. Sema7A-plexinC1 interactions have also been implicated in immune system function, but the neuronal role of this ligand-receptor pair remains to be explored. To gain further insight into the function(s) of Sema7A and plexinC1 during neural development, we present here a detailed analysis of Sema7A and plexinC1 expression in the developing rat nervous system. Results In situ hybridization revealed select expression of Sema7A and plexinC1 in multiple neuronal systems including: the olfactory system, the hypothalamo-hypophysial system, the hippocampus, the meso-diencephalic dopamine system, and the spinal cord. Within these systems, Sema7A and plexinC1 are often expressed in specific neuronal subsets. In general, Sema7A transcript levels increase significantly towards adulthood, whereas plexinC1 expression decreases as development proceeds. PlexinC1, but not Sema7A, is strongly expressed by distinct populations of migrating neurons. In addition to neuronal expression, Sema7A and plexinC1 transcripts were detected in oligodendrocytes and ependymal cells, respectively. Conclusion Sema7A and plexinC1 expression patterns are consistent with these proteins serving both cooperative and separate functions during neural development. The prominent expression of plexinC1 in several distinct

  20. Axon guidance factor SLIT2 inhibits neural invasion and metastasis in pancreatic cancer.

    Science.gov (United States)

    Göhrig, Andreas; Detjen, Katharina M; Hilfenhaus, Georg; Körner, Jan L; Welzel, Martina; Arsenic, Ruza; Schmuck, Rosa; Bahra, Marcus; Wu, Jane Y; Wiedenmann, Bertram; Fischer, Christian

    2014-03-01

    Pancreatic ductal adenocarcinoma (PDAC) metastasizes by neural, vascular, and local invasion routes, which limit patient survival. In nerves and vessels, SLIT2 and its ROBO receptors constitute repellent guidance cues that also direct epithelial branching. Thus, the SLIT2-ROBO system may represent a key pinch point to regulate PDAC spread. In this study, we examined the hypothesis that escaping from repellent SLIT2-ROBO signaling is essential to enable PDAC cells to appropriate their local stromal infrastructure for dissemination. Through immunohistochemical analysis, we detected SLIT2 receptors ROBO1 and ROBO4 on epithelia, nerves, and vessels in healthy pancreas and PDAC specimens, respectively. SLIT2 mRNA expression was reduced in PDAC compared with nontransformed pancreatic tissues and cell lines, suggesting a reduction in SLIT2-ROBO pathway activity in PDAC. In support of this interpretation, restoring the SLIT2 expression in SLIT2-deficient PDAC cells inhibited their bidirectional chemoattraction with neural cells, and more specifically, impaired unidirectional PDAC cell navigation along outgrowing neurites in models of neural invasion. Restoring autocrine/paracrine SLIT2 signaling was also sufficient to inhibit the directed motility of PDAC cells, but not their random movement. Conversely, RNA interference-mediated silencing of ROBO1 stimulated the motility of SLIT2-competent PDAC cells. Furthermore, culture supernatants from SLIT2-competent PDAC cells impaired migration of endothelial cells (human umbilical vein endothelial cells), whereas an N-terminal SLIT2 cleavage fragment stimulated such migration. In vivo investigations of pancreatic tumors with restored SLIT2 expression demonstrated reduced invasion, metastasis, and vascularization, with opposing effects produced by ROBO1 silencing in tumor cells or sequestration of endogenous SLIT2. Analysis of clinical specimens of PDAC showed that those with low SLIT2 mRNA expression exhibited a higher incidence

  1. Axon regeneration impediment:the role of paired immunoglobulin-like receptor B

    Institute of Scientific and Technical Information of China (English)

    Jing Liu; Yan Wang; Wei Fu

    2015-01-01

    Regenerative capacity is weak after central nervous system injury because of the absence of an enhancing microenvironment and presence of an inhibitory microenvironment for neuronal and axonal repair. In addition to the Nogo receptor (NgR), the paired immunoglobulin-like receptor B (PirB) is a recently discovered coreceptor of Nogo, myelin-associated glycoprotein, and myelin oligodendrocyte glycoprotein. Concurrent blocking of NgR and PirB almost completely elim-inates the inhibitory effect of myelin-associated inhibitory molecules on axonal regeneration. PirB participates in a key pathological process of the nervous system, speciifcally axonal regener-ation inhibition. PirB is an inhibitory receptor similar to NgR, but their effects are not identical. This study summarizes the structure, distribution, relationship with common nervous system diseases, and known mechanisms of PirB, and concludes that PirB is also distributed in cells of the immune and hematopoietic systems. Further investigations are needed to determine if im-munomodulation and blood cell migration involve inhibition of axonal regeneration.

  2. Effects of treadmill training after cerebral ischemia on expression in the brain of axonal guidance factor Netrin-4 and its receptor protein%跑台运动训练对脑缺血大鼠轴突导向因子Netrin-4及其受体DCC蛋白表达的影响

    Institute of Scientific and Technical Information of China (English)

    黄欢; 刘楠

    2015-01-01

    目的 观察跑台运动训练对脑缺血大鼠脑组织中轴突导向因子Netrin-4及其受体结直肠癌缺失(DCC)蛋白表达的影响,旨在探讨运动训练促进脑缺血后神经功能恢复的相关机制.方法 取成年雄性SD大鼠63只,按随机数字表法分为假手术组(n=9)、模型组(n=27)和运动组(n=27).模型组和运动组大鼠采用改良的Longa线栓法制备大脑中动脉闭塞(MCAO)脑缺血模型,假手术组大鼠手术方法同模型组和运动组,但是不插入线栓.运动组于造模成功后24 h采用跑台训练器进行运动训练,其余2组则不进行运动训练.采用修正的神经行为学评分方法(mNSS)评价模型组和运动组大鼠造模后第3、7、14天的神经功能,并断头取脑,采用Western blot法以及免疫荧光法检测脑缺血区组织中Netrin-4、DCC蛋白的表达情况.结果 造模后第3、7、14天,运动组和模型组的mNSS评分与假手术组比较,差异均有统计学意义(P<0.01);造模后第7、14天,运动组的mNSS评分分别为(6.89±1.27)分和(5.22±1.09)分,低于模型组同时间点,差异均有统计学意义(P<0.05);造模后第7、14天,运动组的Netrin-4、DCC蛋白表达均较模型组增强(P<0.05);造模后第14天,经免疫荧光法检测发现,Netrin-4主要在脑缺血区的血管和星形胶质细胞中表达,而DCC蛋白主要在脑缺血区的神经元轴突和星形胶质细胞中表达.结论 跑台运动训练可促进脑缺血大鼠神经功能恢复,其机制可能与上调脑缺血区组织中Netrin-4、DCC蛋白的表达,进而增强了神经、血管的再生和重建有关.%Objective To observe the effects of treadmill training on the expression of axonal guidance factor Netrin-4 and its receptor deleted in colorectal cancer (DCC) protein in the brains of rats with cerebral ischemia.Also to explore how training promotes the recovery of neurological function after cerebral ischemia.Methods Sixty-three adult, male Sprague

  3. Retinoic acid receptor beta2 promotes functional regeneration of sensory axons in the spinal cord.

    Science.gov (United States)

    Wong, Liang-Fong; Yip, Ping K; Battaglia, Anna; Grist, John; Corcoran, Jonathan; Maden, Malcolm; Azzouz, Mimoun; Kingsman, Susan M; Kingsman, Alan J; Mazarakis, Nicholas D; McMahon, Stephen B

    2006-02-01

    The embryonic CNS readily undergoes regeneration, unlike the adult CNS, which has limited axonal repair after injury. Here we tested the hypothesis that retinoic acid receptor beta2 (RARbeta2), critical in development for neuronal growth, may enable adult neurons to grow in an inhibitory environment. Overexpression of RARbeta2 in adult rat dorsal root ganglion cultures increased intracellular levels of cyclic AMP and stimulated neurite outgrowth. Stable RARbeta2 expression in DRG neurons in vitro and in vivo enabled their axons to regenerate across the inhibitory dorsal root entry zone and project into the gray matter of the spinal cord. The regenerated neurons enhanced second-order neuronal activity in the spinal cord, and RARbeta2-treated rats showed highly significant improvement in sensorimotor tasks. These findings show that RARbeta2 induces axonal regeneration programs within injured neurons and may thus offer new therapeutic opportunities for CNS regeneration. PMID:16388307

  4. Shank3 is localized in axons and presynaptic specializations of developing hippocampal neurons and involved in the modulation of NMDA receptor levels at axon terminals.

    Science.gov (United States)

    Halbedl, Sonja; Schoen, Michael; Feiler, Marisa S; Boeckers, Tobias M; Schmeisser, Michael J

    2016-04-01

    Autism-related Shank1, Shank2, and Shank3 are major postsynaptic scaffold proteins of excitatory glutamatergic synapses. A few studies, however, have already indicated that within a neuron, the presence of Shank family members is not limited to the postsynaptic density. By separating axons from dendrites of developing hippocampal neurons in microfluidic chambers, we show that RNA of all three Shank family members is present within axons. Immunostaining confirms these findings as all three Shanks are indeed found within separated axons and further co-localize with well-known proteins of the presynaptic specialization in axon terminals. Therefore, Shank proteins might not only serve as postsynaptic scaffold proteins, but also play a crucial role during axonal outgrowth and presynaptic development and function. This is supported by our findings that shRNA-mediated knockdown of Shank3 results in up-regulation of the NMDA receptor subunit GluN1 in axon terminals. Taken together, our findings will have major implications for the future analysis of neuronal Shank biology in both health and disease. Shank1, Shank2, and Shank3 are major postsynaptic scaffold proteins of excitatory glutamatergic synapses strongly related to several neuropsychiatric disorders. However, a few studies have already implicated a functional role of the Shanks beyond the postsynaptic density (PSD). We here show that all three Shanks are localized in both axons and pre-synaptic specializiations of developing hippocampal neurons in culture. We further provide evidence that Shank3 is involved in the modulation of NMDA receptor levels at axon terminals. Taken together, our study will open up novel avenues for the future analysis of neuronal Shank biology in both health and disease.

  5. Axon-to-Glia Interaction Regulates GABAA Receptor Expression in Oligodendrocytes.

    Science.gov (United States)

    Arellano, Rogelio O; Sánchez-Gómez, María Victoria; Alberdi, Elena; Canedo-Antelo, Manuel; Chara, Juan Carlos; Palomino, Aitor; Pérez-Samartín, Alberto; Matute, Carlos

    2016-01-01

    Myelination requires oligodendrocyte-neuron communication, and both neurotransmitters and contact interactions are essential for this process. Oligodendrocytes are endowed with neurotransmitter receptors whose expression levels and properties may change during myelination. However, only scant information is available about the extent and timing of these changes or how they are regulated by oligodendrocyte-neuron interactions. Here, we used electrophysiology to study the expression of ionotropic GABA, glutamate, and ATP receptors in oligodendrocytes derived from the optic nerve and forebrain cultured either alone or in the presence of dorsal root ganglion neurons. We observed that oligodendrocytes from both regions responded to these transmitters at 1 day in culture. After the first day in culture, however, GABA sensitivity diminished drastically to less than 10%, while that of glutamate and ATP remained constant. In contrast, the GABA response amplitude was sustained and remained stable in oligodendrocytes cocultured with dorsal root ganglion neurons. Immunochemistry and pharmacological properties of the responses indicated that they were mediated by distinctive GABAA receptors and that in coculture with neurons, the oligodendrocytes bearing the receptors were those in direct contact with axons. These results reveal that GABAA receptor regulation in oligodendrocytes is driven by axonal cues and that GABA signaling may play a role in myelination and/or during axon-glia recognition.

  6. Structural plasticity of GABAergic axons is regulated by network activity and GABAA receptor activation

    Directory of Open Access Journals (Sweden)

    Anne eSchuemann

    2013-06-01

    Full Text Available Coordinated changes at excitatory and inhibitory synapses are essential for normal brain development and function. It is well established that excitatory neurons undergo structural changes, but our knowledge about inhibitory structural plasticity is rather scarce. Here we present a quantitative analysis of the dynamics of GABAergic boutons in the dendritic region of the hippocampal CA1 area using time-lapse two-photon imaging in organotypic hippocampal cultures from GAD65-GFP mice. We show that ~20% of inhibitory boutons are not stable. They are appearing, disappearing and reappearing at specific locations along the inhibitory axon and reflect immature or incomplete synapses. Furthermore, we observed that persistent boutons show large volume fluctuations over several hours, suggesting that presynaptic content of inhibitory synapses is not constant. Our data show that inhibitory boutons are highly dynamic structures and suggest that inhibitory axons are continuously probing potential locations for inhibitory synapse formation by redistributing presynaptic material along the axon.In addition, we found that neuronal activity affects the exploratory dynamics of inhibitory axons. Blocking network activity rapidly reduces the number of transient boutons, whereas enhancing activity reduces the number of persistent inhibitory boutons, possibly reflecting enhanced competition between boutons along the axon. The latter effect requires signaling through GABAA receptors. We propose that activity-dependent regulation of bouton dynamics contributes to inhibitory synaptic plasticity.

  7. Evidence for Dysregulation of Axonal Growth and Guidance in the Etiology of ASD

    OpenAIRE

    Kathryn eMcFadden; Nancy eMinshew

    2013-01-01

    Current theories concerning the cause of autism spectrum disorders (ASDs) have converged on the concept of abnormal development of brain connectivity. This concept is supported by accumulating evidence from functional imaging, DTI, and high definition fiber tracking (HDFT) studies which suggest altered microstructure in the axonal tracts connecting cortical areas may underly many of the cognitive manifestations of ASD. Additionally, large-scale genomic studies implicate numerous gene candidat...

  8. Spatiotemporal expression of repulsive guidance molecules (RGMs and their receptor neogenin in the mouse brain.

    Directory of Open Access Journals (Sweden)

    Dianne M A van den Heuvel

    Full Text Available Neogenin has been implicated in a variety of developmental processes such as neurogenesis, neuronal differentiation, apoptosis, migration and axon guidance. Binding of repulsive guidance molecules (RGMs to Neogenin inhibits axon outgrowth of different neuronal populations. This effect requires Neogenin to interact with co-receptors of the uncoordinated locomotion-5 (Unc5 family to activate downstream Rho signaling. Although previous studies have reported RGM, Neogenin, and/or Unc5 expression, a systematic comparison of RGM and Neogenin expression in the developing nervous system is lacking, especially at later developmental stages. Furthermore, information on RGM and Neogenin expression at the protein level is limited. To fill this void and to gain further insight into the role of RGM-Neogenin signaling during mouse neural development, we studied the expression of RGMa, RGMb, Neogenin and Unc5A-D using in situ hybridization, immunohistochemistry and RGMa section binding. Expression patterns in the primary olfactory system, cortex, hippocampus, habenula, and cerebellum were studied in more detail. Characteristic cell layer-specific expression patterns were detected for RGMa, RGMb, Neogenin and Unc5A-D. Furthermore, strong expression of RGMa, RGMb and Neogenin protein was found on several major axon tracts such as the primary olfactory projections, anterior commissure and fasciculus retroflexus. These data not only hint at a role for RGM-Neogenin signaling during the development of different neuronal systems, but also suggest that Neogenin partners with different Unc5 family members in different systems. Overall, the results presented here will serve as a framework for further dissection of the role of RGM-Neogenin signaling during neural development.

  9. A neuron-benign microfluidic gradient generator for studying the response of mammalian neurons towards axon guidance factors.

    Science.gov (United States)

    Bhattacharjee, Nirveek; Li, Nianzhen; Keenan, Thomas M; Folch, Albert

    2010-11-01

    Investigation of biochemical cues in isolation or in combinations in cell culture systems is crucial for unraveling the mechanisms that govern neural development and repair. The most widely used experimental paradigms that elicit axon guidance in vitro utilize as the source of the gradient a pulsatile pipette, transfected cells, or a loaded gel, producing time-varying gradients of poor reproducibility which are not well suited for studying slow-growing mammalian cells. Although microfluidic device design have allowed for generating stable, complex gradients of diffusible molecules, the flow-induced shear forces in a microchannel has made it impossible to maintain viable mammalian neuronal cultures for sufficiently long times. In this paper, we describe axonal responses of mouse cortical neurons in a "neuron-benign" gradient-generator device based on an open chamber that can establish highly stable gradients of diffusible molecules for at least 6 h with negligible shear stress, and also allows the neurons to thrive for at least 2 weeks. Except for the period when the gradient is on, the cells in the gradient are under the same conditions as the cells on the control surfaces, which ensure a consistent set of micro-environmental variables. The gradient stability and uniformity over the cell culture surface achieved by the device, together with our software platform for acquiring, post-processing and quantitatively analyzing the large number of images allowed us to extract valuable information even from small datasets. We report a directed response of primary mammalian neurons (from E14 embryonic mice cortex) to a diffusible gradient of netrin in vitro. We infer from our studies that a large majority (∼73%) of the neurons that extend axons during the gradient application grow towards the netrin source, and our data analysis also indicates that netrin acts as a growth factor for this same population of neurons.

  10. Overexpression of Pax6 results in microphthalmia, retinal dysplasia and defective retinal ganglion cell axon guidance

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    Jeffery Glen

    2008-05-01

    Full Text Available Abstract Background The transcription factor Pax6 is expressed by many cell types in the developing eye. Eyes do not form in homozygous loss-of-function mouse mutants (Pax6Sey/Sey and are abnormally small in Pax6Sey/+ mutants. Eyes are also abnormally small in PAX77 mice expressing multiple copies of human PAX6 in addition to endogenous Pax6; protein sequences are identical in the two species. The developmental events that lead to microphthalmia in PAX77 mice are not well-characterised, so it is not clear whether over- and under-expression of Pax6/PAX6 cause microphthalmia through similar mechanisms. Here, we examined the consequences of over-expression for the eye and its axonal connections. Results Eyes form in PAX77+/+ embryos but subsequently degenerate. At E12.5, we found no abnormalities in ocular morphology, retinal cell cycle parameters and the incidence of retinal cell death. From E14.5 on, we observed malformations of the optic disc. From E16.5 into postnatal life there is progressively more severe retinal dysplasia and microphthalmia. Analyses of patterns of gene expression indicated that PAX77+/+ retinae produce a normal range of cell types, including retinal ganglion cells (RGCs. At E14.5 and E16.5, quantitative RT-PCR with probes for a range of molecules associated with retinal development showed only one significant change: a slight reduction in levels of mRNA encoding the secreted morphogen Shh at E16.5. At E16.5, tract-tracing with carbocyanine dyes in PAX77+/+ embryos revealed errors in intraretinal navigation by RGC axons, a decrease in the number of RGC axons reaching the thalamus and an increase in the proportion of ipsilateral projections among those RGC axons that do reach the thalamus. A survey of embryos with different Pax6/PAX6 gene dosage (Pax6Sey/+, Pax6+/+, PAX77+ and PAX77+/+ showed that (1 the total number of RGC axons projected by the retina and (2 the proportions that are sorted into the ipsilateral and

  11. The H3K4me3/2 histone demethylase RBR-2 controls axon guidance by repressing the actin-remodeling gene wsp-1

    DEFF Research Database (Denmark)

    Mariani, Luca; Lussi, Yvonne C.; Vandamme, Julien;

    2016-01-01

    . Here, we show that RBR-2, the sole homolog of the KDM5 family of H3K4me3/2 demethylases in Caenorhabditis elegans, ensures correct axon guidance by controlling the expression of the actin regulator wsp-1. Loss of rbr-2 results in increased levels of H3K4me3 at the transcriptional start site of wsp-1...

  12. Functional and structural characterization of axonal opioid receptors as targets for analgesia

    Science.gov (United States)

    Mambretti, Egle M; Kistner, Katrin; Mayer, Stefanie; Massotte, Dominique; Kieffer, Brigitte L; Hoffmann, Carsten; Reeh, Peter W; Brack, Alexander; Asan, Esther

    2016-01-01

    Background Opioids are the gold standard for the treatment of acute pain despite serious side effects in the central and enteric nervous system. µ-opioid receptors (MOPs) are expressed and functional at the terminals of sensory axons, when activated by exogenous or endogenous ligands. However, the presence and function of MOP along nociceptive axons remains controversial particularly in naïve animals. Here, we characterized axonal MOPs by immunofluorescence, ultrastructural, and functional analyses. Furthermore, we evaluated hypertonic saline as a possible enhancer of opioid receptor function. Results Comparative immunolabeling showed that, among several tested antibodies, which all provided specific MOP detection in the rat central nervous system (CNS), only one monoclonal MOP-antibody yielded specificity and reproducibility for MOP detection in the rat peripheral nervous system including the sciatic nerve. Double immunolabeling documented that MOP immunoreactivity was confined to calcitonin gene-related peptide (CGRP) positive fibers and fiber bundles. Almost identical labeling and double labeling patterns were found using mcherry-immunolabeling on sciatic nerves of mice producing a MOP-mcherry fusion protein (MOP-mcherry knock-in mice). Preembedding immunogold electron microscopy on MOP-mcherry knock-in sciatic nerves indicated presence of MOP in cytoplasm and at membranes of unmyelinated axons. Application of [D-Ala2, N-MePhe4, Gly-ol]-enkephalin (DAMGO) or fentanyl dose-dependently inhibited depolarization-induced CGRP release from rat sciatic nerve axons ex vivo, which was blocked by naloxone. When the lipophilic opioid fentanyl was applied perisciatically in naïve Wistar rats, mechanical nociceptive thresholds increased. Subthreshold doses of fentanyl or the hydrophilic opioid DAMGO were only effective if injected together with hypertonic saline. In vitro, using β-arrestin-2/MOP double-transfected human embryonic kidney cells, DAMGO as well as fentanyl

  13. Lazarillo, a neuronal lipocalin in grasshoppers with a role in axon guidance.

    Science.gov (United States)

    Sánchez, D; Ganfornina, M D; Bastiani, M J

    2000-10-18

    In this report we present a review on the grasshopper lipocalin Lazarillo with special emphasis on how its molecular properties could account for its known function: the guidance of pioneer neurons during nervous system development. The expression and function of Lazarillo in a subset of developing neurons, its heavy glycosylation and its glycosylphosphatidylinositol linkage to the plasma membrane, make Lazarillo a unique member of the lipocalin family. We have built a model of the tertiary structure of Lazarillo in which we have studied the exposed surfaces in search for clues about ligand and protein interactions with Lazarillo. Our hypotheses about how this lipocalin can exert its function are discussed.

  14. Spatial temperature gradients guide axonal outgrowth

    Science.gov (United States)

    Black, Bryan; Vishwakarma, Vivek; Dhakal, Kamal; Bhattarai, Samik; Pradhan, Prabhakar; Jain, Ankur; Kim, Young-Tae; Mohanty, Samarendra

    2016-07-01

    Formation of neural networks during development and regeneration after injury depends on accuracy of axonal pathfinding, which is primarily believed to be influenced by chemical cues. Recently, there is growing evidence that physical cues can play crucial role in axonal guidance. However, detailed mechanism involved in such guidance cues is lacking. By using weakly-focused near-infrared continuous wave (CW) laser microbeam in the path of an advancing axon, we discovered that the beam acts as a repulsive guidance cue. Here, we report that this highly-effective at-a-distance guidance is the result of a temperature field produced by the near-infrared laser light absorption. Since light absorption by extracellular medium increases when the laser wavelength was red shifted, the threshold laser power for reliable guidance was significantly lower in the near-infrared as compared to the visible spectrum. The spatial temperature gradient caused by the near-infrared laser beam at-a-distance was found to activate temperature-sensitive membrane receptors, resulting in an influx of calcium. The repulsive guidance effect was significantly reduced when extracellular calcium was depleted or in the presence of TRPV1-antagonist. Further, direct heating using micro-heater confirmed that the axonal guidance is caused by shallow temperature-gradient, eliminating the role of any non-photothermal effects.

  15. PLR-1, a putative E3 ubiquitin ligase and AEX-3, the GDP/GTP exchange factor homologue for RAB-3, respectively regulate cell polarity and axon navigation of the ventral nerve cord pioneer AVG in Caenorhabditis elegans

    OpenAIRE

    Bhat, Jaffar Mohd

    2015-01-01

    Accurate and precise neuronal circuit formation is the hallmark of a functional nervous system. During development neurons extend axons and dendrites that have to reach their appropriate targets. This process is highly regulated and is achieved by using a set of conserved guidance cues and receptors. ‘Pioneer’ neurons extend axons first and are closely followed by the late outgrowing axons called ‘followers’ to extend upon. In Caenorhabditis elegans, the AVG axon pioneers the right axon tract...

  16. Transcriptional control of axonal guidance and sorting in dorsal interneurons by the Lim-HD proteins Lhx9 and Lhx1

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    Schejter Adi

    2009-06-01

    Full Text Available Abstract Background Lim-HD proteins control crucial aspects of neuronal differentiation, including subtype identity and axonal guidance. The Lim-HD proteins Lhx2/9 and Lhx1/5 are expressed in the dorsal spinal interneuron populations dI1 and dI2, respectively. While they are not required for cell fate acquisition, their role in patterning the axonal trajectory of dI1 and dI2 neurons remains incompletely understood. Results Using newly identified dI1- and dI2-specific enhancers to trace axonal trajectories originating from these interneurons, we found that each population is subdivided into several distinct groups according to their axonal pathways. dI1 neurons project axons rostrally, either ipsi- or contra-laterally, while dI2 are mostly commissural neurons that project their axons rostrally and caudally. The longitudinal axonal tracks of each neuronal population self-fasciculate to form dI1- and dI2-specific bundles. The dI1 bundles are spatially located ventral relative to dI2 bundles. To examine the functional contribution of Lim-HD proteins to establishment of dI axonal projections, the Lim-HD code of dI neurons was altered by cell-specific ectopic expression. Expression of Lhx1 in dI1 neurons caused a repression of Lhx2/9 and imposed caudal projection to the caudal commissural dI1 neurons. Complementarily, when expressed in dI2 neurons, Lhx9 repressed Lhx1/5 and triggered a bias toward rostral projection in otherwise caudally projecting dI2 neurons, and ventral shift of the longitudinal axonal fascicule. Conclusion The Lim-HD proteins Lhx9 and Lhx1 serve as a binary switch in controlling the rostral versus caudal longitudinal turning of the caudal commissural axons. Lhx1 determines caudal turning and Lhx9 triggers rostral turning.

  17. Distinct interneuron types express m2 muscarinic receptor immunoreactivity on their dendrites or axon terminals in the hippocampus.

    Science.gov (United States)

    Hájos, N; Papp, E C; Acsády, L; Levey, A I; Freund, T F

    1998-01-01

    In previous studies m2 muscarinic acetylcholine receptor-immunoreactive interneurons and various types of m2-positive axon terminals have been described in the hippocampal formation. The aim of the present study was to identify the types of interneurons expressing m2 receptor and to examine whether the somadendritic and axonal m2 immunostaining labels the same or distinct cell populations. In the CA1 subfield, neurons immunoreactive for m2 have horizontal dendrites, they are located at the stratum oriens/alveus border and have an axon that project to the dendritic region of pyramidal cells. In the CA3 subfield and the hilus, m2-positive neurons are multipolar and are scattered in all layers except stratum lacunosum-moleculare. In stratum pyramidale of the CA1 and CA3 regions, striking axon terminal staining for m2 was observed, surrounding the somata and axon initial segments of pyramidal cells in a basket-like manner. The co-localization of m2 with neurochemical markers and GABA was studied using the "mirror" technique and fluorescent double-immunostaining at the light microscopic level and with double-labelling using colloidal gold-conjugated antisera and immunoperoxidase reaction (diaminobenzidine) at the electron microscopic level. GABA was shown to be present in the somata of most m2-immunoreactive interneurons, as well as in the majority of m2-positive terminals in all layers. The calcium-binding protein parvalbumin was absent from practically all m2-immunoreactive cell bodies and dendrites. In contrast, many of the terminals synapsing on pyramidal cell somata and axon initial segments co-localized parvalbumin and m2, suggesting a differential distribution of m2 receptor immunoreactivity on the axonal and somadendritic membrane of parvalbumin-containing basket and axo-axonic cells. The co-existence of m2 receptors with the calcium-binding protein calbindin and the neuropeptides cholecystokinin and vasoactive intestinal polypeptide was rare throughout the

  18. Ionotropic receptors at hippocampal mossy fibres: roles in axonal excitability, synaptic transmission and plasticity

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    Arnaud J Ruiz

    2013-01-01

    Full Text Available Dentate granule cells process information from the enthorinal cortex en route to the hippocampus proper. These neurons have a very negative resting membrane potential and are relatively silent in the slice preparation. They are also subject to strong feed-forward inhibition. Their unmyelinated axon or mossy fibre ramifies extensively in the hilus and projects to stratum lucidum where it makes giant en-passant boutons with CA3 pyramidal neurons. There is compelling evidence that mossy fibre boutons express presynaptic GABAA receptors, which are commonly found in granule cell dendrites. There is also suggestive evidence for the presence of other ionotropic receptors, including glycine, NMDA and kainate receptors, in mossy fibre boutons. These presynaptic receptors have been proposed to lead to mossy fibre membrane depolarisation. How this phenomenon alters the excitability of synaptic boutons, the shape of presynaptic action potentials, Ca2+ influx and neurotransmitter release has remained elusive, but high-resolution live imaging of individual varicosities and direct patch-clamp recordings have begun to shed light on these phenomena. Presynaptic GABAA and kainate receptors have also been reported to facilitate the induction of long-term potentiation at mossy fibre – CA3 synapses. Although mossy fibres are highly specialised, some of the principles emerging at this connection may apply elsewhere in the CNS.

  19. Endosome-mediated retrograde axonal transport of P2X3 receptor signals in primary sensory neurons

    Institute of Scientific and Technical Information of China (English)

    Xu-Qiao Chen; BinWang; Chengbiao Wu; Jin Pan; Bo Yuan; Yuan-Yuan Su; Xing-Yu Jiang; Xu Zhang; Lan Bao

    2012-01-01

    Neurotrophins and their receptors adopt signaling endosomes to transmit retrograde signals.However,the mechanisms of retrograde signaling for other ligand/receptor systems are poorly understood.Here,we report that the signals of the purinergic (P)2X3 receptor,an ATP-gated ion channel are retrogradely transported in dorsal root ganglion (DRG) neuron axons.We found that Rab5,a small GTPase,controls the early sorting of P2X3 receptors into endosomes,while Rab7 mediates the fast retrograde transport of P2X3 receptors.Intraplantar injection and axonal application into the microfluidic chamber of α,β-methylene-ATP (α,β-MeATP),a P2X selective agonist,enhanced the endocytosis and retrograde transport of P2X3 receptors.The α,β-MeATP-induced Ca2+ influx activated a pathway comprised of protein kinase C,rat sarcoma viral oncogene and extracellular signal-regulated protein kinase (ERK),which associated with endocytic P2X3 receptors to form signaling endosomes.Disruption of the lipid rafts abolished the α,β-MeATP-induced ERK phosphorylation,endocytosis and retrograde transport of P2X3 receptors.Furthermore,treatment of peripheral axons with α,β-MeATP increased the activation level of ERK and cAMP response element-binding protein in the cell bodies of DRG neurons and enhanced neuronal excitability.Impairment of either microtubule-based axonal transport in vivo or dynein function in vitro blocked α,β-MeATP-induced retrograde signals.These results indicate that P2X3 receptor-activated signals are transmitted via retrogradely transported endosomes in primary sensory neurons and provide a novel signaling mechanism for ligand-gated channels.

  20. 2- and 6-O-sulfated proteoglycans have distinct and complementary roles in cranial axon guidance and motor neuron migration

    Science.gov (United States)

    Maden, Charlotte H.; Davidson, Kathryn; Fantin, Alessandro

    2016-01-01

    The correct migration and axon extension of neurons in the developing nervous system is essential for the appropriate wiring and function of neural networks. Here, we report that O-sulfotransferases, a class of enzymes that modify heparan sulfate proteoglycans (HSPGs), are essential to regulate neuronal migration and axon development. We show that the 6-O-sulfotransferases HS6ST1 and HS6ST2 are essential for cranial axon patterning, whilst the 2-O-sulfotransferase HS2ST (also known as HS2ST1) is important to regulate the migration of facial branchiomotor (FBM) neurons in the hindbrain. We have also investigated how HS2ST interacts with other signals in the hindbrain and show that fibroblast growth factor (FGF) signalling regulates FBM neuron migration in an HS2ST-dependent manner. PMID:27048738

  1. Similar GABAA receptor subunit composition in somatic and axon initial segment synapses of hippocampal pyramidal cells.

    Science.gov (United States)

    Kerti-Szigeti, Katalin; Nusser, Zoltan

    2016-01-01

    Hippocampal pyramidal cells (PCs) express many GABAAR subunit types and receive GABAergic inputs from distinct interneurons. Previous experiments revealed input-specific differences in α1 and α2 subunit densities in perisomatic synapses, suggesting distinct IPSC decay kinetics. However, IPSC decays evoked by axo-axonic, parvalbumin- or cholecystokinin-expressing basket cells were found to be similar. Using replica immunogold labeling, here we show that all CA1 PC somatic and AIS synapses contain the α1, α2, β1, β2, β3 and γ2 subunits. In CA3 PCs, 90% of the perisomatic synapses are immunopositive for the α1 subunit and all synapses are positive for the remaining five subunits. Somatic synapses form unimodal distributions based on their immunoreactivity for these subunits. The α2 subunit densities in somatic synapses facing Cav2.1 (i.e. parvalbumin) or Cav2.2 (cholecystokinin) positive presynaptic active zones are comparable. We conclude that perisomatic synapses made by three distinct interneuron types have similar GABAA receptor subunit content. PMID:27537197

  2. Local translation and directional steering in axons

    OpenAIRE

    Lin, Andrew C; Holt, Christine E.

    2007-01-01

    The assembly of functional neural circuits in the developing brain requires neurons to extend axons to the correct targets. This in turn requires the navigating tips of axons to respond appropriately to guidance cues present along the axonal pathway, despite being cellular ‘outposts' far from the soma. Work over the past few years has demonstrated a critical role for local translation within the axon in this process in vitro, making axon guidance another process that requires spatially locali...

  3. Current progress in functions of axon guidance molecule Slit and underlying molecular mechanism%神经轴突导向分子Slit的功能及其分子作用机制研究进展

    Institute of Scientific and Technical Information of China (English)

    于奇; 周启升; 赵晓; 刘庆信

    2012-01-01

    神经轴突导向分子Slit是一种在进化上高度保守的分泌型糖蛋白,Slit对神经轴突导向、神经细胞迁移、神经细胞形态分化、肿瘤转移、血管生成、心脏形态发生等多种生命活动具有调节作用.Slit功能的实现主要是通过其LRR-2结构域与受体Roundabout (Robo)的Igl结构域相结合而实现的,另外硫酸肝素蛋白多糖(heparan sulfate proteoglycans,HSPGs)、GTP酶激活蛋白(GTPase-activating proteins,GAPs)、酪氨酸激酶Abelson、Ca2+、MicroRNA-218和其它轴突导向分子等多种信号分子也参与了Slit功能的实现.slit基因受到Single-minded、Irx4和Midline等转录因子的调控,另外,转录后水平的选择性剪接使slit基因存在多种亚型.Slit导向机制的研究有助于揭示生物神经发育和再生过程中神经网络形成的内在分子基础,同时,也将为预防和治疗人类神经疾病、抑制癌细胞转移等提供理论参考.%The axon guidance molecule Slit is a secreted glucoprotein which is conserved during evolution. Slit has been implicated in regulating a variety of life activities, such as axon guidance, neuronal migration, neuronal morphological differentiation, tumor metastasis, angiogenesis and heart morphogenesis. Slit function mainly depends on the binding of its LRR-2 domain to the Ig1 domain of Roundabout (Robo) receptor, meanwhile Slit function is also mediated by a range of signaling molecules, including the heparan sul-fate proteoglycans (HSPGs), GTPase-activating proteins (GAPs), tyrosine kinase Abelson, calcium ions, MicroRNA-218 and other axon guidance molecules. Several transcription factors, including Single-minded, Irx and Midline, were shown to regulate slit expression. In addition, multiple Slit isoforms exist as a consequence of alternative spliced transcripts. The research on guidance mechanism of Slit will facilitate the understanding of molecular mechanism underlying neural networks formation in the process of

  4. Transcriptional control in embryonic Drosophila midline guidance assessed through a whole genome approach

    Directory of Open Access Journals (Sweden)

    Tomancak Pavel

    2007-07-01

    Full Text Available Abstract Background During the development of the Drosophila central nervous system the process of midline crossing is orchestrated by a number of guidance receptors and ligands. Many key axon guidance molecules have been identified in both invertebrates and vertebrates, but the transcriptional regulation of growth cone guidance remains largely unknown. It is established that translational regulation plays a role in midline crossing, and there are indications that transcriptional regulation is also involved. To investigate this issue, we conducted a genome-wide study of transcription in Drosophila embryos using wild type and a number of well-characterized Drosophila guidance mutants and transgenics. We also analyzed a previously published microarray time course of Drosophila embryonic development with an axon guidance focus. Results Using hopach, a novel clustering method which is well suited to microarray data analysis, we identified groups of genes with similar expression patterns across guidance mutants and transgenics. We then systematically characterized the resulting clusters with respect to their relevance to axon guidance using two complementary controlled vocabularies: the Gene Ontology (GO and anatomical annotations of the Atlas of Pattern of Gene Expression (APoGE in situ hybridization database. The analysis indicates that regulation of gene expression does play a role in the process of axon guidance in Drosophila. We also find a strong link between axon guidance and hemocyte migration, a result that agrees with mounting evidence that axon guidance molecules are co-opted in vertebrate vascularization. Cell cyclin activity in the context of axon guidance is also suggested from our array data. RNA and protein expression patterns of cell cyclins in axon guidance mutants and transgenics support this possible link. Conclusion This study provides important insights into the regulation of axon guidance in vivo.

  5. Current and calcium responses to local activation of axonal NMDA receptors in developing cerebellar molecular layer interneurons.

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    Bénédicte Rossi

    Full Text Available In developing cerebellar molecular layer interneurons (MLIs, NMDA increases spontaneous GABA release. This effect had been attributed to either direct activation of presynaptic NMDA receptors (preNMDARs or an indirect pathway involving activation of somato-dendritic NMDARs followed by passive spread of somatic depolarization along the axon and activation of axonal voltage dependent Ca(2+ channels (VDCCs. Using Ca(2+ imaging and electrophysiology, we searched for preNMDARs by uncaging NMDAR agonists either broadly throughout the whole field or locally at specific axonal locations. Releasing either NMDA or glutamate in the presence of NBQX using short laser pulses elicited current transients that were highly sensitive to the location of the spot and restricted to a small number of varicosities. The signal was abolished in the presence of high Mg(2+ or by the addition of APV. Similar paradigms yielded restricted Ca(2+ transients in interneurons loaded with a Ca(2+ indicator. We found that the synaptic effects of NMDA were not inhibited by blocking VDCCs but were impaired in the presence of the ryanodine receptor antagonist dantrolene. Furthermore, in voltage clamped cells, bath applied NMDA triggers Ca(2+ elevations and induces neurotransmitter release in the axonal compartment. Our results suggest the existence of preNMDARs in developing MLIs and propose their involvement in the NMDA-evoked increase in GABA release by triggering a Ca(2+-induced Ca(2+ release process mediated by presynaptic Ca(2+ stores. Such a mechanism is likely to exert a crucial role in various forms of Ca(2+-mediated synaptic plasticity.

  6. Pioneer Axon Navigation Is Controlled by AEX-3, a Guanine Nucleotide Exchange Factor for RAB-3 in Caenorhabditis elegans.

    Science.gov (United States)

    Bhat, Jaffar M; Hutter, Harald

    2016-07-01

    Precise and accurate axon tract formation is an essential aspect of brain development. This is achieved by the migration of early outgrowing axons (pioneers) allowing later outgrowing axons (followers) to extend toward their targets in the embryo. In Caenorhabditis elegans the AVG neuron pioneers the right axon tract of the ventral nerve cord, the major longitudinal axon tract. AVG is essential for the guidance of follower axons and hence organization of the ventral nerve cord. In an enhancer screen for AVG axon guidance defects in a nid-1/Nidogen mutant background, we isolated an allele of aex-3 aex-3 mutant animals show highly penetrant AVG axon navigation defects. These defects are dependent on a mutation in nid-1/Nidogen, a basement membrane component. Our data suggest that AEX-3 activates RAB-3 in the context of AVG axon navigation. aex-3 genetically acts together with known players of vesicular exocytosis: unc-64/Syntaxin, unc-31/CAPS, and ida-1/IA-2. Furthermore our genetic interaction data suggest that AEX-3 and the UNC-6/Netrin receptor UNC-5 act in the same pathway, suggesting AEX-3 might regulate the trafficking and/or insertion of UNC-5 at the growth cone to mediate the proper guidance of the AVG axon. PMID:27116976

  7. Transcriptome Profiling Identifies Multiplexin as a Target of SAGA Deubiquitinase Activity in Glia Required for Precise Axon Guidance During Drosophila Visual Development

    Directory of Open Access Journals (Sweden)

    Jingqun Ma

    2016-08-01

    Full Text Available The Spt-Ada-Gcn5 Acetyltransferase (SAGA complex is a transcriptional coactivator with histone acetylase and deubiquitinase activities that plays an important role in visual development and function. In Drosophila melanogaster, four SAGA subunits are required for the deubiquitination of monoubiquitinated histone H2B (ubH2B: Nonstop, Sgf11, E(y2, and Ataxin 7. Mutations that disrupt SAGA deubiquitinase activity cause defects in neuronal connectivity in the developing Drosophila visual system. In addition, mutations in SAGA result in the human progressive visual disorder spinocerebellar ataxia type 7 (SCA7. Glial cells play a crucial role in both the neuronal connectivity defect in nonstop and sgf11 flies, and in the retinal degeneration observed in SCA7 patients. Thus, we sought to identify the gene targets of SAGA deubiquitinase activity in glia in the Drosophila larval central nervous system. To do this, we enriched glia from wild-type, nonstop, and sgf11 larval optic lobes using affinity-purification of KASH-GFP tagged nuclei, and then examined each transcriptome using RNA-seq. Our analysis showed that SAGA deubiquitinase activity is required for proper expression of 16% of actively transcribed genes in glia, especially genes involved in proteasome function, protein folding and axon guidance. We further show that the SAGA deubiquitinase-activated gene Multiplexin (Mp is required in glia for proper photoreceptor axon targeting. Mutations in the human ortholog of Mp, COL18A1, have been identified in a family with a SCA7-like progressive visual disorder, suggesting that defects in the expression of this gene in SCA7 patients could play a role in the retinal degeneration that is unique to this ataxia.

  8. Transcriptome Profiling Identifies Multiplexin as a Target of SAGA Deubiquitinase Activity in Glia Required for Precise Axon Guidance During Drosophila Visual Development

    Science.gov (United States)

    Ma, Jingqun; Brennan, Kaelan J.; D’Aloia, Mitch R.; Pascuzzi, Pete E.; Weake, Vikki M.

    2016-01-01

    The Spt-Ada-Gcn5 Acetyltransferase (SAGA) complex is a transcriptional coactivator with histone acetylase and deubiquitinase activities that plays an important role in visual development and function. In Drosophila melanogaster, four SAGA subunits are required for the deubiquitination of monoubiquitinated histone H2B (ubH2B): Nonstop, Sgf11, E(y)2, and Ataxin 7. Mutations that disrupt SAGA deubiquitinase activity cause defects in neuronal connectivity in the developing Drosophila visual system. In addition, mutations in SAGA result in the human progressive visual disorder spinocerebellar ataxia type 7 (SCA7). Glial cells play a crucial role in both the neuronal connectivity defect in nonstop and sgf11 flies, and in the retinal degeneration observed in SCA7 patients. Thus, we sought to identify the gene targets of SAGA deubiquitinase activity in glia in the Drosophila larval central nervous system. To do this, we enriched glia from wild-type, nonstop, and sgf11 larval optic lobes using affinity-purification of KASH-GFP tagged nuclei, and then examined each transcriptome using RNA-seq. Our analysis showed that SAGA deubiquitinase activity is required for proper expression of 16% of actively transcribed genes in glia, especially genes involved in proteasome function, protein folding and axon guidance. We further show that the SAGA deubiquitinase-activated gene Multiplexin (Mp) is required in glia for proper photoreceptor axon targeting. Mutations in the human ortholog of Mp, COL18A1, have been identified in a family with a SCA7-like progressive visual disorder, suggesting that defects in the expression of this gene in SCA7 patients could play a role in the retinal degeneration that is unique to this ataxia. PMID:27261002

  9. Coordinated Eph-ephrin signaling guides migration and axon targeting in the avian auditory system

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    Allen-Sharpley Michelle R

    2012-08-01

    Full Text Available Abstract Background In the avian sound localization circuit, nucleus magnocellularis (NM projects bilaterally to nucleus laminaris (NL, with ipsilateral and contralateral NM axon branches directed to dorsal and ventral NL dendrites, respectively. We previously showed that the Eph receptor EphB2 is expressed in NL neuropil and NM axons during development. Here we tested whether EphB2 contributes to NM-NL circuit formation. Results We found that misexpression of EphB2 in embryonic NM precursors significantly increased the number of axon targeting errors from NM to contralateral NL in a cell-autonomous manner when forward signaling was impaired. We also tested the effects of inhibiting forward signaling of different Eph receptor subclasses by injecting soluble unclustered Fc-fusion proteins at stages when NM axons are approaching their NL target. Again we found an increase in axon targeting errors compared to controls when forward signaling was impaired, an effect that was significantly increased when both Eph receptor subclasses were inhibited together. In addition to axon targeting errors, we also observed morphological abnormalities of the auditory nuclei when EphB2 forward signaling was increased by E2 transfection, and when Eph-ephrin forward signaling was inhibited by E6-E8 injection of Eph receptor fusion proteins. Conclusions These data suggest that EphB signaling has distinct functions in axon guidance and morphogenesis. The results provide evidence that multiple Eph receptors work synergistically in the formation of precise auditory circuitry.

  10. Central connectivity of transient receptor potential melastatin 8-expressing axons in the brain stem and spinal dorsal horn.

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    Yun Sook Kim

    Full Text Available Transient receptor potential melastatin 8 (TRPM8 ion channels mediate the detection of noxious and innocuous cold and are expressed by primary sensory neurons, but little is known about the processing of the TRPM8-mediated cold information within the trigeminal sensory nuclei (TSN and the spinal dorsal horn (DH. To address this issue, we characterized TRPM8-positive (+ neurons in the trigeminal ganglion and investigated the distribution of TRPM8+ axons and terminals, and their synaptic organization in the TSN and in the DH using light and electron microscopic immunohistochemistry in transgenic mice expressing a genetically encoded axonal tracer in TRPM8+ neurons. TRPM8 was expressed in a fraction of small myelinated primary afferent fibers (23.7% and unmyelinated fibers (76.3%, suggesting that TRPM8-mediated cold is conveyed via C and Aδ afferents. TRPM8+ axons were observed in all TSN, but at different densities in the dorsal and ventral areas of the rostral TSN, which dominantly receive sensory afferents from intra- and peri-oral structures and from the face, respectively. While synaptic boutons arising from Aδ and non-peptidergic C afferents usually receive many axoaxonic contacts and form complex synaptic arrangements, TRPM8+ boutons arising from afferents of the same classes of fibers showed a unique synaptic connectivity; simple synapses with one or two dendrites and sparse axoaxonic contacts. These findings suggest that TRPM8-mediated cold is conveyed via a specific subset of C and Aδ afferent neurons and is processed in a unique manner and differently in the TSN and DH.

  11. Tumor necrosis factor and its p55 and p75 receptors are not required for axonal lesion-induced microgliosis in mouse fascia dentata

    DEFF Research Database (Denmark)

    Fenger, Christina; Drøjdahl, Nina; Nielsen, Martin Wirenfeldt;

    2006-01-01

    and terminal degeneration in mice, we studied the effect of TNF and its p55 and p75 receptors on axonal lesion-induced microglial activation in fascia dentata following transection of the perforant path (PP) projection. Unexpectedly, cell counting showed that the axonal lesion-induced microglial response...... maximum. However, in spite of the induction of TNF mRNA, TNF protein level remained at base-line in fascia dentata using immunohistochemistry and ELISA. In conclusion, the results showed a lower than expected lesion-induced increase in TNF protein, and that neither TNF nor its receptors were required...... for the axonal lesion-induced microglial morphological transformation and proliferation or for the initial clearance of degenerated myelin in the PP-deafferented fascia dentata....

  12. Developmental expression profiles of axon guidance signaling and the immune system in the marmoset cortex: potential molecular mechanisms of pruning of dendritic spines during primate synapse formation in late infancy and prepuberty (I).

    Science.gov (United States)

    Sasaki, Tetsuya; Oga, Tomofumi; Nakagaki, Keiko; Sakai, Kazuhisa; Sumida, Kayo; Hoshino, Kohei; Miyawaki, Izuru; Saito, Koichi; Suto, Fumikazu; Ichinohe, Noritaka

    2014-02-14

    The synapse number and the related dendritic spine number in the cerebral cortex of primates shows a rapid increase after birth. Depending on the brain region and species, the number of synapses reaches a peak before adulthood, and pruning takes place after this peak (overshoot-type synaptic formation). Human mental disorders, such as autism and schizophrenia, are hypothesized to be a result of either too weak or excessive pruning after the peak is reached. Thus, it is important to study the molecular mechanisms underlying overshoot-type synaptic formation, particularly the pruning phase. To examine the molecular mechanisms, we used common marmosets (Callithrix jacchus). Microarray analysis of the marmoset cortex was performed in the ventrolateral prefrontal, inferior temporal, and primary visual cortices, where changes in the number of dendritic spines have been observed. The spine number of all the brain regions above showed a peak at 3 months (3 M) after birth and gradually decreased (e.g., at 6 M and in adults). In this study, we focused on genes that showed differential expression between ages of 3 M and 6 M and on the differences whose fold change (FC) was greater than 1.2. The selected genes were subjected to canonical pathway analysis, and in this study, we describe axon guidance signaling, which had high plausibility. The results showed a large number of genes belonging to subsystems within the axon guidance signaling pathway, macrophages/immune system, glutamate system, and others. We divided the data and discussion of these results into 2 papers, and this is the first paper, which deals with the axon guidance signaling and macrophage/immune system. Other systems will be described in the next paper. Many components of subsystems within the axon guidance signaling underwent changes in gene expression from 3 M to 6 M so that the synapse/dendritic spine number would decrease at 6 M. Thus, axon guidance signaling probably contributes to the decrease in

  13. Plexin A3 and turnout regulate motor axonal branch morphogenesis in zebrafish.

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    Rajiv Sainath

    Full Text Available During embryogenesis motor axons navigate to their target muscles, where individual motor axons develop complex branch morphologies. The mechanisms that control axonal branching morphogenesis have been studied intensively, yet it still remains unclear when branches begin to form or how branch locations are determined. Live cell imaging of individual zebrafish motor axons reveals that the first axonal branches are generated at the ventral extent of the myotome via bifurcation of the growth cone. Subsequent branches are generated by collateral branching restricted to their synaptic target field along the distal portion of the axon. This precisely timed and spatially restricted branching process is disrupted in turnout mutants we identified in a forward genetic screen. Molecular genetic mapping positioned the turnout mutation within a 300 kb region encompassing eight annotated genes, however sequence analysis of all eight open reading frames failed to unambiguously identify the turnout mutation. Chimeric analysis and single cell labeling reveal that turnout function is required cell non-autonomously for intraspinal motor axon guidance and peripheral branch formation. turnout mutant motor axons form the first branch on time via growth cone bifurcation, but unlike wild-type they form collateral branches precociously, when the growth cone is still navigating towards the ventral myotome. These precocious collateral branches emerge along the proximal region of the axon shaft typically devoid of branches, and they develop into stable, permanent branches. Furthermore, we find that null mutants of the guidance receptor plexin A3 display identical motor axon branching defects, and time lapse analysis reveals that precocious branch formation in turnout and plexin A3 mutants is due to increased stability of otherwise short-lived axonal protrusions. Thus, plexin A3 dependent intrinsic and turnout dependent extrinsic mechanisms suppress collateral branch

  14. The SAX-3 receptor stimulates axon outgrowth and the signal sequence and transmembrane domain are critical for SAX-3 membrane localization in the PDE neuron of C. elegans.

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    Jia Li

    Full Text Available SAX-3, a receptor for Slit in C. elegans, is well characterized for its function in axonal development. However, the mechanism that regulates the membrane localization of SAX-3 and the role of SAX-3 in axon outgrowth are still elusive. Here we show that SAX-3::GFP caused ectopic axon outgrowth, which could be suppressed by the loss-of-function mutation in unc-73 (a guanine nucleotide exchange factor for small GTPases and unc-115 (an actin binding protein, suggesting that they might act downstream of SAX-3 in axon outgrowth. We also examined genes related to axon development for their possible involvement in the subcellular localization of SAX-3. We found the unc-51 mutants appeared to accumulate SAX-3::GFP in the neuronal cell body of the posterior deirid (PDE neuron, indicating that UNC-51 might play a role in SAX-3 membrane localization. Furthermore, we demonstrate that the N-terminal signal sequence and the transmembrane domain are essential for the subcellular localization of SAX-3 in the PDE neurons.

  15. AT2-receptor stimulation enhances axonal plasticity after spinal cord injury by upregulating BDNF expression

    DEFF Research Database (Denmark)

    Namsolleck, Pawel; Boato, Francesco; Schwengel, Katja;

    2013-01-01

    outgrowth was absent in neurons derived from AT2R-KO mice. In primary neurons, treatment with C21 further induced RNA expression of anti-apoptotic Bcl-2 (+75.7%), brain-derived neurotrophic factor (BDNF) (+53.7%), the neurotrophin receptors TrkA (+57.4%) and TrkB (+67.9%) and a marker for neurite growth...

  16. AMIGO3 is an NgR1/p75 co-receptor signalling axon growth inhibition in the acute phase of adult central nervous system injury.

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    Zubair Ahmed

    Full Text Available Axon regeneration in the injured adult CNS is reportedly inhibited by myelin-derived inhibitory molecules, after binding to a receptor complex comprised of the Nogo-66 receptor (NgR1 and two transmembrane co-receptors p75/TROY and LINGO-1. However, the post-injury expression pattern for LINGO-1 is inconsistent with its proposed function. We demonstrated that AMIGO3 levels were significantly higher acutely than those of LINGO-1 in dorsal column lesions and reduced in models of dorsal root ganglion neuron (DRGN axon regeneration. Similarly, AMIGO3 levels were raised in the retina immediately after optic nerve crush, whilst levels were suppressed in regenerating optic nerves, induced by intravitreal peripheral nerve implantation. AMIGO3 interacted functionally with NgR1-p75/TROY in non-neuronal cells and in brain lysates, mediating RhoA activation in response to CNS myelin. Knockdown of AMIGO3 in myelin-inhibited adult primary DRG and retinal cultures promoted disinhibited neurite growth when cells were stimulated with appropriate neurotrophic factors. These findings demonstrate that AMIGO3 substitutes for LINGO-1 in the NgR1-p75/TROY inhibitory signalling complex and suggests that the NgR1-p75/TROY-AMIGO3 receptor complex mediates myelin-induced inhibition of axon growth acutely in the CNS. Thus, antagonizing AMIGO3 rather than LINGO-1 immediately after CNS injury is likely to be a more effective therapeutic strategy for promoting CNS axon regeneration when combined with neurotrophic factor administration.

  17. AMIGO3 is an NgR1/p75 co-receptor signalling axon growth inhibition in the acute phase of adult central nervous system injury.

    Science.gov (United States)

    Ahmed, Zubair; Douglas, Michael R; John, Gabrielle; Berry, Martin; Logan, Ann

    2013-01-01

    Axon regeneration in the injured adult CNS is reportedly inhibited by myelin-derived inhibitory molecules, after binding to a receptor complex comprised of the Nogo-66 receptor (NgR1) and two transmembrane co-receptors p75/TROY and LINGO-1. However, the post-injury expression pattern for LINGO-1 is inconsistent with its proposed function. We demonstrated that AMIGO3 levels were significantly higher acutely than those of LINGO-1 in dorsal column lesions and reduced in models of dorsal root ganglion neuron (DRGN) axon regeneration. Similarly, AMIGO3 levels were raised in the retina immediately after optic nerve crush, whilst levels were suppressed in regenerating optic nerves, induced by intravitreal peripheral nerve implantation. AMIGO3 interacted functionally with NgR1-p75/TROY in non-neuronal cells and in brain lysates, mediating RhoA activation in response to CNS myelin. Knockdown of AMIGO3 in myelin-inhibited adult primary DRG and retinal cultures promoted disinhibited neurite growth when cells were stimulated with appropriate neurotrophic factors. These findings demonstrate that AMIGO3 substitutes for LINGO-1 in the NgR1-p75/TROY inhibitory signalling complex and suggests that the NgR1-p75/TROY-AMIGO3 receptor complex mediates myelin-induced inhibition of axon growth acutely in the CNS. Thus, antagonizing AMIGO3 rather than LINGO-1 immediately after CNS injury is likely to be a more effective therapeutic strategy for promoting CNS axon regeneration when combined with neurotrophic factor administration. PMID:23613963

  18. Knockdown of Ephrin-A5 Expression by 40% Does not Affect Motor Axon Growth or Migration into the Chick Hindlimb

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    Robert S. Winning

    2011-11-01

    Full Text Available Bidirectional signaling between Eph receptor tyrosine kinases and their cell-surface protein signals, the ephrins, comprises one mechanism for guiding motor axons to their proper targets. During projection of motor axons from the lateral motor column (LMC motor neurons of the spinal cord to the hindlimb muscles in chick embryos, ephrin-A5 has been shown to be expressed in the LMC motor axons until they reach the base of the limb bud and initiate sorting into their presumptive dorsal and ventral nerve trunks, at which point expression is extinguished. We tested the hypothesis that this dynamic pattern of ephrin-A5 expression in LMC motor axons is important for the growth and guidance of the axons to, and into, the hindlimb by knocking down endogenous ephrin-A5 expression in the motor neurons and their axons. No perturbation of LMC motor axon projections was observed in response to this treatment, suggesting that ephrin-A5 is not needed for LMC motor axon growth or guidance.

  19. Constitutively expressed Protocadherin-α regulates the coalescence and elimination of homotypic olfactory axons through its cytoplasmic region

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    Sonoko eHasegawa

    2012-10-01

    Full Text Available Olfactory sensory neuron (OSN axons coalesce into specific glomeruli in the olfactory bulb (OB according to their odorant receptor (OR expression. Several guidance molecules enhance the coalescence of homotypic OSN projections, in an OR-specific- and neural-activity-dependent manner. However, the mechanism by which homotypic OSN axons are organized into glomeruli is unsolved. We previously reported that the clustered protocadherin-α (Pcdh-α family of diverse cadherin-related molecules plays roles in the coalescence and elimination of homotypic OSN axons throughout development. Here we showed that the elimination of small ectopic homotypic glomeruli required the constitutive expression of a Pcdh-α isoform and Pcdh-α’s cytoplasmic region, but not OR specificity or neural activity. These results suggest that Pcdh-α proteins provide a cytoplasmic signal to regulate repulsive activity for homotypic OSN axons independently of OR expression and neural activity. The counterbalancing effect of Pcdh-α proteins for the axonal coalescence mechanisms mediated by other olfactory guidance molecules indicate a possible mechanism for the organization of homotypic OSN axons into glomeruli during development.

  20. A Simple Method for 3D Analysis of Immunolabeled Axonal Tracts in a Transparent Nervous System

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    Morgane Belle

    2014-11-01

    Full Text Available Clearing techniques have been developed to transparentize mouse brains, thereby preserving 3D structure, but their complexity has limited their use. Here, we show that immunolabeling of axonal tracts followed by optical clearing with solvents (3DISCO and light-sheet microscopy reveals brain connectivity in mouse embryos and postnatal brains. We show that the Robo3 receptor is selectively expressed by medial habenula axons forming the fasciculus retroflexus (FR and analyzed the development of this commissural tract in mutants of the Slit/Robo and DCC/Netrin pathways. Netrin-1 and DCC are required to attract FR axons to the midline, but the two mutants exhibit specific and heterogeneous axon guidance defects. Moreover, floor-plate-specific deletion of Slit ligands with a conditional Slit2 allele perturbs not only midline crossing by FR axons but also their anteroposterior distribution. In conclusion, this method represents a unique and powerful imaging tool to study axonal connectivity in mutant mice.

  1. Electrokinetic confinement of axonal growth for dynamically configurable neural networks.

    Science.gov (United States)

    Honegger, Thibault; Scott, Mark A; Yanik, Mehmet F; Voldman, Joel

    2013-02-21

    Axons in the developing nervous system are directed via guidance cues, whose expression varies both spatially and temporally, to create functional neural circuits. Existing methods to create patterns of neural connectivity in vitro use only static geometries, and are unable to dynamically alter the guidance cues imparted on the cells. We introduce the use of AC electrokinetics to dynamically control axonal growth in cultured rat hippocampal neurons. We find that the application of modest voltages at frequencies on the order of 10(5) Hz can cause developing axons to be stopped adjacent to the electrodes while axons away from the electric fields exhibit uninhibited growth. By switching electrodes on or off, we can reversibly inhibit or permit axon passage across the electrodes. Our models suggest that dielectrophoresis is the causative AC electrokinetic effect. We make use of our dynamic control over axon elongation to create an axon-diode via an axon-lock system that consists of a pair of electrode 'gates' that either permit or prevent axons from passing through. Finally, we developed a neural circuit consisting of three populations of neurons, separated by three axon-locks to demonstrate the assembly of a functional, engineered neural network. Action potential recordings demonstrate that the AC electrokinetic effect does not harm axons, and Ca(2+) imaging demonstrated the unidirectional nature of the synaptic connections. AC electrokinetic confinement of axonal growth has potential for creating configurable, directional neural networks. PMID:23314575

  2. Evidence for a role of srGAP3 in the positioning of commissural axons within the ventrolateral funiculus of the mouse spinal cord.

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    Claire Bacon

    Full Text Available Slit-Robo signaling guides commissural axons away from the floor-plate of the spinal cord and into the longitudinal axis after crossing the midline. In this study we have evaluated the role of the Slit-Robo GTPase activating protein 3 (srGAP3 in commissural axon guidance using a knockout (KO mouse model. Co-immunoprecipitation experiments confirmed that srGAP3 interacts with the Slit receptors Robo1 and Robo2 and immunohistochemistry studies showed that srGAP3 co-localises with Robo1 in the ventral and lateral funiculus and with Robo2 in the lateral funiculus. Stalling axons have been reported in the floor-plate of Slit and Robo mutant spinal cords but our axon tracing experiments revealed no dorsal commissural axon stalling in the floor plate of the srGAP3 KO mouse. Interestingly we observed a significant thickening of the ventral funiculus and a thinning of the lateral funiculus in the srGAP3 KO spinal cord, which has also recently been reported in the Robo2 KO. However, axons in the enlarged ventral funiculus of the srGAP3 KO are Robo1 positive but do not express Robo2, indicating that the thickening of the ventral funiculus in the srGAP3 KO is not a Robo2 mediated effect. We suggest a role for srGAP3 in the lateral positioning of post crossing axons within the ventrolateral funiculus.

  3. Mechanisms of axon degeneration: from development to disease.

    Science.gov (United States)

    Saxena, Smita; Caroni, Pico

    2007-10-01

    Axon degeneration is an active, tightly controlled and versatile process of axon segment self-destruction. Although not involving cell death, it resembles apoptosis in its logics. It involves three distinct steps: induction of competence in specific neurons, triggering of degeneration at defined axon segments of competent neurons, and rapid fragmentation and removal of the segments. The mechanisms that initiate degeneration are specific to individual settings, but the final pathway of pruning is shared; it involves microtubule disassembly, axon swellings, axon fragmentation, and removal of the remnants by locally recruited phagocytes. The tight regulatory properties of axon degeneration distinguish it from passive loss phenomena, and confer significance to processes that involve it. Axon degeneration has prominent roles in development, upon lesions and in disease. In development, it couples the progressive specification of neurons and circuits to the removal of defined axon branches. Competence might involve transcriptional switches, and local triggering can involve axon guidance molecules and synaptic activity patterns. Lesion-induced Wallerian degeneration is inhibited in the presence of Wld(S) fusion protein in neurons; it involves early local, and later, distal degeneration. It has recently become clear that like in other settings, axon degeneration in disease is a rapid and specific process, which should not be confused with a variety of disease-related pathologies. Elucidating the specific mechanisms that initiate axon degeneration should open up new avenues to investigate principles of circuit assembly and plasticity, to uncover mechanisms of disease progression, and to identify ways of protecting synapses and axons in disease.

  4. Axonal interferon responses and alphaherpesvirus neuroinvasion

    Science.gov (United States)

    Song, Ren

    Infection by alphaherpesviruses, including herpes simplex virus (HSV) and pseudorabies virus (PRV), typically begins at a peripheral epithelial surface and continues into the peripheral nervous system (PNS) that innervates this tissue. Inflammatory responses are induced at the infected peripheral site prior to viral invasion of the PNS. PNS neurons are highly polarized cells with long axonal processes that connect to distant targets. When the peripheral tissue is first infected, only the innervating axons are exposed to this inflammatory milieu, which include type I interferon (e.g. IFNbeta) and type II interferon (i.e. IFNgamma). IFNbeta can be produced by all types of cells, while IFNgamma is secreted by some specific types of immune cells. And both types of IFN induce antiviral responses in surrounding cells that express the IFN receptors. The fundamental question is how do PNS neurons respond to the inflammatory milieu experienced only by their axons. Axons must act as potential front-line barriers to prevent PNS infection and damage. Using compartmented cultures that physically separate neuron axons from cell bodies, I found that pretreating isolated axons with IFNbeta or IFNgamma significantly diminished the number of HSV-1 and PRV particles moving from axons to the cell bodies in an IFN receptor-dependent manner. Furthermore, I found the responses in axons are activated differentially by the two types of IFNs. The response to IFNbeta is a rapid, axon-only response, while the response to IFNgamma involves long distance signaling to the PNS cell body. For example, exposing axons to IFNbeta induced STAT1 phosphorylation (p-STAT1) only in axons, while exposure of axons to IFNgamma induced p-STAT1 accumulation in distant cell body nuclei. Blocking transcription in cell bodies eliminated IFNgamma-, but not IFNbeta-mediated antiviral effects. Proteomic analysis of IFNbeta- or IFNgamma-treated axons identified several differentially regulated proteins. Therefore

  5. Slit and Netrin-1 guide cranial motor axon pathfinding via Rho-kinase, myosin light chain kinase and myosin II

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    Drescher Uwe

    2010-06-01

    Full Text Available Abstract Background In the developing hindbrain, cranial motor axon guidance depends on diffusible repellent factors produced by the floor plate. Our previous studies have suggested that candidate molecules for mediating this effect are Slits, Netrin-1 and Semaphorin3A (Sema3A. It is unknown to what extent these factors contribute to floor plate-derived chemorepulsion of motor axons, and the downstream signalling pathways are largely unclear. Results In this study, we have used a combination of in vitro and in vivo approaches to identify the components of floor plate chemorepulsion and their downstream signalling pathways. Using in vitro motor axon deflection assays, we demonstrate that Slits and Netrin-1, but not Sema3A, contribute to floor plate repulsion. We also find that the axon pathways of dorsally projecting branchiomotor neurons are disrupted in Netrin-1 mutant mice and in chick embryos expressing dominant-negative Unc5a receptors, indicating an in vivo role for Netrin-1. We further demonstrate that Slit and Netrin-1 signalling are mediated by Rho-kinase (ROCK and myosin light chain kinase (MLCK, which regulate myosin II activity, controlling actin retrograde flow in the growth cone. We show that MLCK, ROCK and myosin II are required for Slit and Netrin-1-mediated growth cone collapse of cranial motor axons. Inhibition of these molecules in explant cultures, or genetic manipulation of RhoA or myosin II function in vivo causes characteristic cranial motor axon pathfinding errors, including the inability to exit the midline, and loss of turning towards exit points. Conclusions Our findings suggest that both Slits and Netrin-1 contribute to floor plate-derived chemorepulsion of cranial motor axons. They further indicate that RhoA/ROCK, MLCK and myosin II are components of Slit and Netrin-1 signalling pathways, and suggest that these pathways are of key importance in cranial motor axon navigation.

  6. N-Cadherin and Integrins: Two Receptor Systems That Mediate Neuronal Process Outgrowth on Astrocyte Surfaces

    OpenAIRE

    Tomaselli, Kevin J.; Neugebauer, Karla M; Bixby, John L.; Lilien, Jack; Reichardt, Louis F.

    2008-01-01

    Receptor-mediated interactions between neurons and astroglia are likely to play a crucial role in the growth and guidance of CNS axons. Using antibodies to neuronal cell surface proteins, we identified two receptor systems mediating neurite outgrowth on cultured astrocytes. N-cadherin, a Ca2+-dependent cell adhesion molecule, functions prominently in the outgrowth of neurites on astrocytes by E8 and E14 chick ciliary ganglion (CC) neurons. β1-class integrin ECM receptor heterodimers function ...

  7. Computing along the axon

    Institute of Scientific and Technical Information of China (English)

    Chen Haiming; Tseren-Onolt Ishdorj; Gheorghe Pǎun

    2007-01-01

    A special form of spiking neural P systems, called axon P systems, corresponding to the activity of Ranvier nodes of neuron axon, is considered and a class of SN-like P systems where the computation is done along the axon is introduced and their language generative power is investigated.

  8. Dscam1 Forms a Complex with Robo1 and the N-Terminal Fragment of Slit to Promote the Growth of Longitudinal Axons

    Science.gov (United States)

    Alavi, Maryam; Song, Minmin; Gillis, Taylor; Bousum, Adam; Miller, Amanda; Kidd, Thomas

    2016-01-01

    The Slit protein is a major midline repellent for central nervous system (CNS) axons. In vivo, Slit is proteolytically cleaved into N- and C-terminal fragments, but the biological significance of this is unknown. Analysis in the Drosophila ventral nerve cord of a slit allele (slit-UC) that cannot be cleaved revealed that midline repulsion is still present but longitudinal axon guidance is disrupted, particularly across segment boundaries. Double mutants for the Slit receptors Dscam1 and robo1 strongly resemble the slit-UC phenotype, suggesting they cooperate in longitudinal axon guidance, and through biochemical approaches, we found that Dscam1 and Robo1 form a complex dependent on Slit-N. In contrast, Robo1 binding alone shows a preference for full-length Slit, whereas Dscam1 only binds Slit-N. Using a variety of transgenes, we demonstrated that Dscam1 appears to modify the output of Robo/Slit complexes so that signaling is no longer repulsive. Our data suggest that the complex is promoting longitudinal axon growth across the segment boundary. The ability of Dscam1 to modify the output of other receptors in a ligand-dependent fashion may be a general principle for Dscam proteins. PMID:27654876

  9. Integration of shallow gradients of Shh and Netrin-1 guides commissural axons.

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    Tyler F W Sloan

    2015-03-01

    Full Text Available During nervous system development, gradients of Sonic Hedgehog (Shh and Netrin-1 attract growth cones of commissural axons toward the floor plate of the embryonic spinal cord. Mice defective for either Shh or Netrin-1 signaling have commissural axon guidance defects, suggesting that both Shh and Netrin-1 are required for correct axon guidance. However, how Shh and Netrin-1 collaborate to guide axons is not known. We first quantified the steepness of the Shh gradient in the spinal cord and found that it is mostly very shallow. We then developed an in vitro microfluidic guidance assay to simulate these shallow gradients. We found that axons of dissociated commissural neurons respond to steep but not shallow gradients of Shh or Netrin-1. However, when we presented axons with combined Shh and Netrin-1 gradients, they had heightened sensitivity to the guidance cues, turning in response to shallower gradients that were unable to guide axons when only one cue was present. Furthermore, these shallow gradients polarized growth cone Src-family kinase (SFK activity only when Shh and Netrin-1 were combined, indicating that SFKs can integrate the two guidance cues. Together, our results indicate that Shh and Netrin-1 synergize to enable growth cones to sense shallow gradients in regions of the spinal cord where the steepness of a single guidance cue is insufficient to guide axons, and we identify a novel type of synergy that occurs when the steepness (and not the concentration of a guidance cue is limiting.

  10. Chronic excitotoxin-induced axon degeneration in a compartmented neuronal culture model

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    Katherine A Hosie

    2012-02-01

    Full Text Available Glutamate excitotoxicity is a major pathogenic process implicated in many neurodegenerative conditions, including AD (Alzheimer's disease and following traumatic brain injury. Occurring predominantly from over-stimulation of ionotropic glutamate receptors located along dendrites, excitotoxic axonal degeneration may also occur in white matter tracts. Recent identification of axonal glutamate receptor subunits within axonal nanocomplexes raises the possibility of direct excitotoxic effects on axons. Individual neuronal responses to excitotoxicity are highly dependent on the complement of glutamate receptors expressed by the cell, and the localization of the functional receptors. To enable isolation of distal axons and targeted excitotoxicity, murine cortical neuron cultures were prepared in compartmented microfluidic devices, such that distal axons were isolated from neuronal cell bodies. Within the compartmented culture system, cortical neurons developed to relative maturity at 11 DIV (days in vitro as demonstrated by the formation of dendritic spines and clustering of the presynaptic protein synaptophysin. The isolated distal axons retained growth cone structures in the absence of synaptic targets, and expressed glutamate receptor subunits. Glutamate treatment (100 μM to the cell body chamber resulted in widespread degeneration within this chamber and degeneration of distal axons in the other chamber. Glutamate application to the distal axon chamber triggered a lesser degree of axonal degeneration without degenerative changes in the untreated somal chamber. These data indicate that in addition to current mechanisms of indirect axonal excitotoxicity, the distal axon may be a primary target for excitotoxicity in neurodegenerative conditions.

  11. Mirror movement-like defects in startle behavior of zebrafish dcc mutants are caused by aberrant midline guidance of identified descending hindbrain neurons.

    Science.gov (United States)

    Jain, Roshan A; Bell, Hannah; Lim, Amy; Chien, Chi-Bin; Granato, Michael

    2014-02-19

    Mirror movements are involuntary movements on one side of the body that occur simultaneously with intentional movements on the contralateral side. Humans with heterozygous mutations in the axon guidance receptor DCC display such mirror movements, where unilateral stimulation results in inappropriate bilateral motor output. Currently, it is unclear whether mirror movements are caused by incomplete midline crossing and reduced commissural connectivity of DCC-dependent descending pathways or by aberrant ectopic ipsilateral axonal projections of normally commissural neurons. Here, we show that in response to unilateral tactile stimuli, zebrafish dcc mutant larvae perform involuntary turns on the inappropriate body side. We show that these mirror movement-like deficits are associated with axonal guidance defects of two identified groups of commissural reticulospinal hindbrain neurons. Moreover, we demonstrate that in dcc mutants, axons of these identified neurons frequently fail to cross the midline and instead project ipsilaterally. Whereas laser ablation of these neurons in wild-type animals does not affect turning movements, their ablation in dcc mutants restores turning movements. Thus, our results demonstrate that in dcc mutants, turns on the inappropriate side of the body are caused by aberrant ipsilateral axonal projections, and suggest that aberrant ipsilateral connectivity of a very small number of descending axons is sufficient to induce incorrect movement patterns.

  12. Coordinated motor neuron axon growth and neuromuscular synaptogenesis are promoted by CPG15 in vivo.

    Science.gov (United States)

    Javaherian, Ashkan; Cline, Hollis T

    2005-02-17

    We have used in vivo time-lapse two-photon imaging of single motor neuron axons labeled with GFP combined with labeling of presynaptic vesicle clusters and postsynaptic acetylcholine receptors in Xenopus laevis tadpoles to determine the dynamic rearrangement of individual axon branches and synaptogenesis during motor axon arbor development. Control GFP-labeled axons are highly dynamic during the period when axon arbors are elaborating. Axon branches emerge from sites of synaptic vesicle clusters. These data indicate that motor neuron axon elaboration and synaptogenesis are concurrent and iterative. We tested the role of Candidate Plasticity Gene 15 (CPG15, also known as Neuritin), an activity-regulated gene that is expressed in the developing motor neurons in this process. CPG15 expression enhances the development of motor neuron axon arbors by promoting neuromuscular synaptogenesis and by increasing the addition of new axon branches. PMID:15721237

  13. Actin turnover is required to prevent axon retraction driven by endogenous actomyosin contractility

    OpenAIRE

    Gallo, Gianluca; Yee, Hal F.; Letourneau, Paul C.

    2002-01-01

    Growth cone motility and guidance depend on the dynamic reorganization of filamentous actin (F-actin). In the growth cone, F-actin undergoes turnover, which is the exchange of actin subunits from existing filaments. However, the function of F-actin turnover is not clear. We used jasplakinolide (jasp), a cell-permeable macrocyclic peptide that inhibits F-actin turnover, to study the role of F-actin turnover in axon extension. Treatment with jasp caused axon retraction, demonstrating that axon ...

  14. Corticostriatal combinatorics: the implications of corticostriatal axonal arborizations.

    Science.gov (United States)

    Zheng, T; Wilson, C J

    2002-02-01

    The complete striatal axonal arborizations of 16 juxtacellularly stained cortical pyramidal cells were analyzed. Corticostriatal neurons were located in the medial agranular or anterior cingulate cortex of rats. All axons were of the extended type and formed synaptic contacts in both the striosomal and matrix compartments as determined by counterstaining for the mu-opiate receptor. Six axonal arborizations were from collaterals of brain stem-projecting cells and the other 10 from bilaterally projecting cells with no brain stem projections. The distribution of synaptic boutons along the axons were convolved with the average dendritic tree volume of spiny projection neurons to obtain an axonal innervation volume and innervation density map for each axon. Innervation volumes varied widely, with single axons occupying between 0.4 and 14.2% of the striatum (average = 4%). The total number of boutons formed by individual axons ranged from 25 to 2,900 (average = 879). Within the innervation volume, the density of innervation was extremely sparse but inhomogeneous. The pattern of innervation resembled matrisomes, as defined by bulk labeling and functional mapping experiments, superimposed on a low background innervation. Using this sample as representative of all corticostriatal axons, the total number of corticostriatal neurons was estimated to be 17 million, about 10 times the number of striatal projection neurons.

  15. Determinants of axonal regeneration

    OpenAIRE

    Frisén, J

    1997-01-01

    Axons often regrow to their targets and lost functions may be restored after an injury in the peripheral nervous system. In contrast, axonal regeneration is generally very limited after injuries in the central nervous system, and functional impairment is usually permanent. The regenerative capacity depends on intrinsic neuronal factors as weil as the interaction of neurons with other cells. Glial cells may, in different situations, either support or inhibit axo...

  16. The MADD-3 LAMMER Kinase Interacts with a p38 MAP Kinase Pathway to Regulate the Display of the EVA-1 Guidance Receptor in Caenorhabditis elegans.

    Directory of Open Access Journals (Sweden)

    Serena A D'Souza

    2016-04-01

    Full Text Available The proper display of transmembrane receptors on the leading edge of migrating cells and cell extensions is essential for their response to guidance cues. We previously discovered that MADD-4, which is an ADAMTSL secreted by motor neurons in Caenorhabditis elegans, interacts with an UNC-40/EVA-1 co-receptor complex on muscles to attract plasma membrane extensions called muscle arms. In nematodes, the muscle arm termini harbor the post-synaptic elements of the neuromuscular junction. Through a forward genetic screen for mutants with disrupted muscle arm extension, we discovered that a LAMMER kinase, which we call MADD-3, is required for the proper display of the EVA-1 receptor on the muscle's plasma membrane. Without MADD-3, EVA-1 levels decrease concomitantly with a reduction of the late-endosomal marker RAB-7. Through a genetic suppressor screen, we found that the levels of EVA-1 and RAB-7 can be restored in madd-3 mutants by eliminating the function of a p38 MAP kinase pathway. We also found that EVA-1 and RAB-7 will accumulate in madd-3 mutants upon disrupting CUP-5, which is a mucolipin ortholog required for proper lysosome function. Together, our data suggests that the MADD-3 LAMMER kinase antagonizes the p38-mediated endosomal trafficking of EVA-1 to the lysosome. In this way, MADD-3 ensures that sufficient levels of EVA-1 are present to guide muscle arm extension towards the source of the MADD-4 guidance cue.

  17. The MADD-3 LAMMER Kinase Interacts with a p38 MAP Kinase Pathway to Regulate the Display of the EVA-1 Guidance Receptor in Caenorhabditis elegans

    Science.gov (United States)

    D’Souza, Serena A.; Rajendran, Luckshika; Bagg, Rachel; van Pel, Derek M.; Moshiri, Houtan; Roy, Peter J.

    2016-01-01

    The proper display of transmembrane receptors on the leading edge of migrating cells and cell extensions is essential for their response to guidance cues. We previously discovered that MADD-4, which is an ADAMTSL secreted by motor neurons in Caenorhabditis elegans, interacts with an UNC-40/EVA-1 co-receptor complex on muscles to attract plasma membrane extensions called muscle arms. In nematodes, the muscle arm termini harbor the post-synaptic elements of the neuromuscular junction. Through a forward genetic screen for mutants with disrupted muscle arm extension, we discovered that a LAMMER kinase, which we call MADD-3, is required for the proper display of the EVA-1 receptor on the muscle’s plasma membrane. Without MADD-3, EVA-1 levels decrease concomitantly with a reduction of the late-endosomal marker RAB-7. Through a genetic suppressor screen, we found that the levels of EVA-1 and RAB-7 can be restored in madd-3 mutants by eliminating the function of a p38 MAP kinase pathway. We also found that EVA-1 and RAB-7 will accumulate in madd-3 mutants upon disrupting CUP-5, which is a mucolipin ortholog required for proper lysosome function. Together, our data suggests that the MADD-3 LAMMER kinase antagonizes the p38-mediated endosomal trafficking of EVA-1 to the lysosome. In this way, MADD-3 ensures that sufficient levels of EVA-1 are present to guide muscle arm extension towards the source of the MADD-4 guidance cue. PMID:27123983

  18. The MADD-3 LAMMER Kinase Interacts with a p38 MAP Kinase Pathway to Regulate the Display of the EVA-1 Guidance Receptor in Caenorhabditis elegans.

    Science.gov (United States)

    D'Souza, Serena A; Rajendran, Luckshika; Bagg, Rachel; Barbier, Louis; van Pel, Derek M; Moshiri, Houtan; Roy, Peter J

    2016-04-01

    The proper display of transmembrane receptors on the leading edge of migrating cells and cell extensions is essential for their response to guidance cues. We previously discovered that MADD-4, which is an ADAMTSL secreted by motor neurons in Caenorhabditis elegans, interacts with an UNC-40/EVA-1 co-receptor complex on muscles to attract plasma membrane extensions called muscle arms. In nematodes, the muscle arm termini harbor the post-synaptic elements of the neuromuscular junction. Through a forward genetic screen for mutants with disrupted muscle arm extension, we discovered that a LAMMER kinase, which we call MADD-3, is required for the proper display of the EVA-1 receptor on the muscle's plasma membrane. Without MADD-3, EVA-1 levels decrease concomitantly with a reduction of the late-endosomal marker RAB-7. Through a genetic suppressor screen, we found that the levels of EVA-1 and RAB-7 can be restored in madd-3 mutants by eliminating the function of a p38 MAP kinase pathway. We also found that EVA-1 and RAB-7 will accumulate in madd-3 mutants upon disrupting CUP-5, which is a mucolipin ortholog required for proper lysosome function. Together, our data suggests that the MADD-3 LAMMER kinase antagonizes the p38-mediated endosomal trafficking of EVA-1 to the lysosome. In this way, MADD-3 ensures that sufficient levels of EVA-1 are present to guide muscle arm extension towards the source of the MADD-4 guidance cue.

  19. Axonal PPARγ promotes neuronal regeneration after injury.

    Science.gov (United States)

    Lezana, Juan Pablo; Dagan, Shachar Y; Robinson, Ari; Goldstein, Ronald S; Fainzilber, Mike; Bronfman, Francisca C; Bronfman, Miguel

    2016-06-01

    PPARγ is a ligand-activated nuclear receptor best known for its involvement in adipogenesis and glucose homeostasis. PPARγ activity has also been associated with neuroprotection in different neurological disorders, but the mechanisms involved in PPARγ effects in the nervous system are still unknown. Here we describe a new functional role for PPARγ in neuronal responses to injury. We found both PPAR transcripts and protein within sensory axons and observed an increase in PPARγ protein levels after sciatic nerve crush. This was correlated with increased retrograde transport of PPARγ after injury, increased association of PPARγ with the molecular motor dynein, and increased nuclear accumulation of PPARγ in cell bodies of sensory neurons. Furthermore, PPARγ antagonists attenuated the response of sensory neurons to sciatic nerve injury, and inhibited axonal growth of both sensory and cortical neurons in culture. Thus, axonal PPARγ is involved in neuronal injury responses required for axonal regeneration. Since PPARγ is a major molecular target of the thiazolidinedione (TZD) class of drugs used in the treatment of type II diabetes, several pharmaceutical agents with acceptable safety profiles in humans are available. Our findings provide motivation and rationale for the evaluation of such agents for efficacy in central and peripheral nerve injuries. PMID:26446277

  20. Brain gangliosides in axon-myelin stability and axon regeneration

    OpenAIRE

    Schnaar, Ronald L.

    2009-01-01

    Gangliosides, sialic acid-bearing glycosphingolipids, are expressed at high abundance and complexity in the brain. Altered ganglioside expression results in neural disorders, including seizures and axon degeneration. Brain gangliosides function, in part, by interacting with a ganglioside-binding lectin, myelin-associated glycoprotein (MAG). MAG, on the innermost wrap of the myelin sheath, binds to gangliosides GD1a and GT1b on axons. MAG-ganglioside binding ensures optimal axon-myelin cell-ce...

  1. Analysis of axon tract formation in the zebrafish brain: the role of territories of gene expression and their boundaries.

    Science.gov (United States)

    Wilson, S W; Brennan, C; Macdonald, R; Brand, M; Holder, N

    1997-11-01

    Mutant analysis in the zebrafish is revealing the genes that are expressed in the early neuroepithelium and that regulate factors responsible for the guidance of commissural axons. We review work on the developing zebrafish brain illustrating the way in which territories of regulatory gene expression influence the formation and positioning of axon pathways. PMID:9321679

  2. Involvement of SARA in Axon and Dendrite Growth.

    Science.gov (United States)

    Arias, Cristina Isabel; Siri, Sebastián Omar; Conde, Cecilia

    2015-01-01

    SARA (Smad Anchor for Receptor Activation) plays a crucial role in Rab5-mediated endocytosis in cell lines localizing to early endosomes where it regulates morphology and function. Here, we analyzed the role of SARA during neuronal development and tested whether it functions as a regulator of endocytic trafficking of selected axonal and membrane proteins. Suppression of SARA perturbs the appearance of juxtanuclear endocytic recycling compartments and the neurons show long axons with large growth cones. Furthermore, surface distribution of the cell adhesion molecule L1 in axons and the fusion of vesicles containing transferring receptor (TfR) in dendrites were increased in neurons where SARA was silenced. Conversely, SARA overexpression generated large early endosomes and reduced neurite outgrowth. Taken together, our findings suggest a significant contribution of SARA to key aspects of neuronal development, including neurite formation. PMID:26405814

  3. Axon Branch-Specific Semaphorin-1a Signaling in Drosophila Mushroom Body Development

    Science.gov (United States)

    Zwarts, Liesbeth; Goossens, Tim; Clements, Jason; Kang, Yuan Y.; Callaerts, Patrick

    2016-01-01

    Correct wiring of the mushroom body (MB) neuropil in the Drosophila brain involves appropriate positioning of different axonal lobes, as well as the sister branches that develop from individual axons. This positioning requires the integration of various guidance cues provided by different cell types, which help the axons find their final positions within the neuropil. Semaphorins are well-known for their conserved roles in neuronal development and axon guidance. We investigated the role of Sema-1a in MB development more closely. We show that Sema-1a is expressed in the MBs as well as surrounding structures, including the glial transient interhemispheric fibrous ring, throughout development. By loss- and gain-of-function experiments, we show that the MB axons display lobe and sister branch-specific Sema-1a signaling, which controls different aspects of axon outgrowth and guidance. Furthermore, we demonstrate that these effects are modulated by the integration of MB intrinsic and extrinsic Sema-1a signaling pathways involving PlexA and PlexB. Finally, we also show a role for neuronal- glial interaction in Sema-1a dependent β-lobe outgrowth. PMID:27656129

  4. Diverse roles for Wnt7a in ventral midbrain neurogenesis and dopaminergic axon morphogenesis.

    Science.gov (United States)

    Fernando, Chathurini V; Kele, Julianna; Bye, Christopher R; Niclis, Jonathan C; Alsanie, Walaa; Blakely, Brette D; Stenman, Jan; Turner, Brad J; Parish, Clare L

    2014-09-01

    During development of the central nervous system, trophic, together with genetic, cues dictate the balance between cellular proliferation and differentiation. Subsequent to the birth of new neurons, additional intrinsic and extrinsic signals regulate the connectivity of these cells. While a number of regulators of ventral midbrain (VM) neurogenesis and dopaminergic (DA) axon guidance are known, we identify a number of novel roles for the secreted glycoprotein, Wnt7a, in this context. We demonstrate a temporal and spatial expression of Wnt7a in the VM, indicative of roles in neurogenesis, differentiation, and axonal growth and guidance. In primary VM cultures, and validated in Wnt7a-deficient mice, we show that the early expression within the VM is important for regulating VM progenitor proliferation, cell cycle progression, and cell survival, thereby dictating the number of midbrain Nurr1 precursors and DA neurons. During early development of the midbrain DA pathways, Wnt7a promotes axonal elongation and repels DA neurites out of the midbrain. Later, Wnt7a expression in the VM midline suggests a role in preventing axonal crossing while expression in regions flanking the medial forebrain bundle (thalamus and hypothalamus) ensured appropriate trajectory of DA axons en route to their forebrain targets. We show that the effects of Wnt7a in VM development are mediated, at least in part, by the β-catenin/canonical pathways. Together, these findings identify Wnt7a as a new regulator of VM neurogenesis and DA axon growth and guidance.

  5. The genetics of axonal transport and axonal transport disorders.

    Directory of Open Access Journals (Sweden)

    Jason E Duncan

    2006-09-01

    Full Text Available Neurons are specialized cells with a complex architecture that includes elaborate dendritic branches and a long, narrow axon that extends from the cell body to the synaptic terminal. The organized transport of essential biological materials throughout the neuron is required to support its growth, function, and viability. In this review, we focus on insights that have emerged from the genetic analysis of long-distance axonal transport between the cell body and the synaptic terminal. We also discuss recent genetic evidence that supports the hypothesis that disruptions in axonal transport may cause or dramatically contribute to neurodegenerative diseases.

  6. Thiazolidinediones promote axonal growth through the activation of the JNK pathway.

    Directory of Open Access Journals (Sweden)

    Rodrigo A Quintanilla

    Full Text Available The axon is a neuronal process involved in protein transport, synaptic plasticity, and neural regeneration. It has been suggested that their structure and function are profoundly impaired in neurodegenerative diseases. Previous evidence suggest that Peroxisome Proliferator-Activated Receptors-γ (PPARγ promote neuronal differentiation on various neuronal cell types. In addition, we demonstrated that activation of PPARγby thiazolidinediones (TZDs drugs that selectively activate PPARγ prevent neurite loss and axonal damage induced by amyloid-β (Aβ. However, the potential role of TZDs in axonal elongation and neuronal polarity has not been explored. We report here that the activation of PPARγ by TZDs promoted axon elongation in primary hippocampal neurons. Treatments with different TZDs significantly increased axonal growth and branching area, but no significant effects were observed in neurite elongation compared to untreated neurons. Treatment with PPARγ antagonist (GW 9662 prevented TZDs-induced axonal growth. Recently, it has been suggested that the c-Jun N-terminal kinase (JNK plays an important role regulating axonal growth and neuronal polarity. Interestingly, in our studies, treatment with TZDs induced activation of the JNK pathway, and the pharmacological blockage of this pathway prevented axon elongation induced by TZDs. Altogether, these results indicate that activation of JNK induced by PPARγactivators stimulates axonal growth and accelerates neuronal polarity. These novel findings may contribute to the understanding of the effects of PPARγ on neuronal differentiation and validate the use of PPARγ activators as therapeutic agents in neurodegenerative diseases.

  7. Traction Force and Tension Fluctuations During Axon Growth

    Directory of Open Access Journals (Sweden)

    Jamison ePolackwich

    2015-10-01

    Full Text Available Actively generated mechanical forces play a central role in axon growthand guidance, but the mechanisms that underly force generation andregulation in growing axons remain poorly understood. We reportmeasurements of the dynamics of traction stresses from growth cones ofactively advancing axons from postnatal rat DRG neurons. By tracking themovement of the growth cone and analyzing the traction stress field froma reference frame that moves with it, we are able to show that there isa clear and consistent average stress field that underlies the complexspatial stresses present at any one time. The average stress field hasstrong maxima on the sides of the growth cone, directed inward towardthe growth cone neck. This pattern represents a contractile stresscontained within the growth cone, and a net force that is balanced bythe axon tension. Using high time-resolution measurements of the growthcone traction stresses, we show that the stress field is composed offluctuating local stress peaks, with a large number peaks that live fora short time, a population of peaks whose lifetime distribution followsan exponential decay, and a small number of very long-lived peaks. Weshow that the high time-resolution data also reveal that the tensionappears to vary randomly over short time scales, roughly consistent withthe lifetime of the stress peaks, suggesting that the tensionfluctuations originate from stochastic adhesion dynamics.

  8. Distinct roles of neuropilin 1 signaling for radial and tangential extension of callosal axons.

    Science.gov (United States)

    Hatanaka, Yumiko; Matsumoto, Tomoko; Yanagawa, Yuchio; Fujisawa, Hajime; Murakami, Fujio; Masu, Masayuki

    2009-05-20

    Cortical excitatory neurons migrate from their origin in the ventricular zone (VZ) toward the pial surface. During migration, these neurons exhibit a stellate shape in the intermediate zone (IZ), transform into bipolar cells, and then initiate radial migration, extending a trailing process, which may lead to an axon. Here we examined the role of neuropilin 1 (NRP1) in these developmental events. Both NRP1 mRNA and protein were highly expressed in the IZ, where stellate-shaped cells were located. DiI labeling experiments showed that neuronal migration occurred normally in Nrp1 mutant mice up to embryonic day (E) 14.5, the latest day to which the mutant survives, with only subtle axonal defasciculation. However, interference with Nrp1 signaling at a later stage caused pathfinding errors: when a dominant negative form of Nrp1 was electroporated into the cortical VZ cells at E12.5 or E15.5 and examined perinatally, guidance errors were found in tangential axonal extension toward the midline. In contrast, no significant effect was noted on the migration of cortical excitatory neurons. These findings indicate that NRP1 plays an important role in the guidance of callosal axons originating from cortical excitatory neurons but does not support a role in their migration. Moreover, insofar as radial axonal extension within the cortical plate was unaffected, the present findings imply that molecular mechanisms for the axonal extension of excitatory neurons within the cortical plate are distinct from those in the white matter. PMID:19296474

  9. RIPK1 mediates axonal degeneration by promoting inflammation and necroptosis in ALS.

    Science.gov (United States)

    Ito, Yasushi; Ofengeim, Dimitry; Najafov, Ayaz; Das, Sudeshna; Saberi, Shahram; Li, Ying; Hitomi, Junichi; Zhu, Hong; Chen, Hongbo; Mayo, Lior; Geng, Jiefei; Amin, Palak; DeWitt, Judy Park; Mookhtiar, Adnan Kasim; Florez, Marcus; Ouchida, Amanda Tomie; Fan, Jian-bing; Pasparakis, Manolis; Kelliher, Michelle A; Ravits, John; Yuan, Junying

    2016-08-01

    Mutations in the optineurin (OPTN) gene have been implicated in both familial and sporadic amyotrophic lateral sclerosis (ALS). However, the role of this protein in the central nervous system (CNS) and how it may contribute to ALS pathology are unclear. Here, we found that optineurin actively suppressed receptor-interacting kinase 1 (RIPK1)-dependent signaling by regulating its turnover. Loss of OPTN led to progressive dysmyelination and axonal degeneration through engagement of necroptotic machinery in the CNS, including RIPK1, RIPK3, and mixed lineage kinase domain-like protein (MLKL). Furthermore, RIPK1- and RIPK3-mediated axonal pathology was commonly observed in SOD1(G93A) transgenic mice and pathological samples from human ALS patients. Thus, RIPK1 and RIPK3 play a critical role in mediating progressive axonal degeneration. Furthermore, inhibiting RIPK1 kinase may provide an axonal protective strategy for the treatment of ALS and other human degenerative diseases characterized by axonal degeneration. PMID:27493188

  10. A multi-component model of the developing retinocollicular pathway incorporating axonal and synaptic growth.

    Directory of Open Access Journals (Sweden)

    Keith B Godfrey

    2009-12-01

    Full Text Available During development, neurons extend axons to different brain areas and produce stereotypical patterns of connections. The mechanisms underlying this process have been intensively studied in the visual system, where retinal neurons form retinotopic maps in the thalamus and superior colliculus. The mechanisms active in map formation include molecular guidance cues, trophic factor release, spontaneous neural activity, spike-timing dependent plasticity (STDP, synapse creation and retraction, and axon growth, branching and retraction. To investigate how these mechanisms interact, a multi-component model of the developing retinocollicular pathway was produced based on phenomenological approximations of each of these mechanisms. Core assumptions of the model were that the probabilities of axonal branching and synaptic growth are highest where the combined influences of chemoaffinity and trophic factor cues are highest, and that activity-dependent release of trophic factors acts to stabilize synapses. Based on these behaviors, model axons produced morphologically realistic growth patterns and projected to retinotopically correct locations in the colliculus. Findings of the model include that STDP, gradient detection by axonal growth cones and lateral connectivity among collicular neurons were not necessary for refinement, and that the instructive cues for axonal growth appear to be mediated first by molecular guidance and then by neural activity. Although complex, the model appears to be insensitive to variations in how the component developmental mechanisms are implemented. Activity, molecular guidance and the growth and retraction of axons and synapses are common features of neural development, and the findings of this study may have relevance beyond organization in the retinocollicular pathway.

  11. Axon density and axon orientation dispersion in children born preterm

    NARCIS (Netherlands)

    Kelly, Claire E.; Thompson, Deanne K.; Chen, Jian; Leemans, Alexander; Adamson, Christopher L.; Inder, Terrie E.; Cheong, Jeanie L Y; Doyle, Lex W.; Anderson, Peter J.

    2016-01-01

    Background Very preterm birth (VPT, <32 weeks' gestation) is associated with altered white matter fractional anisotropy (FA), the biological basis of which is uncertain but may relate to changes in axon density and/or dispersion, which can be measured using Neurite Orientation Dispersion and Density

  12. Negative regulation of glial engulfment activity by Draper terminates glial responses to axon injury

    OpenAIRE

    Logan, Mary A.; Hackett, Rachel; Doherty, Johnna; Sheehan, Amy; Speese, Sean D.; Freeman, Marc R

    2012-01-01

    Neuronal injury elicits potent cellular responses from glia, but molecular pathways modulating glial activation, phagocytic function, and termination of reactive responses remain poorly defined. Here we show that positive or negative regulation of glial reponses to axon injury are molecularly encoded by unique isoforms of the Drosophila engulfment receptor Draper. Draper-I promotes engulfment of axonal debris through an immunoreceptor tyrosine-based activation motif (ITAM). In contrast, Drape...

  13. Outsourcing CREB translation to axons to survive

    OpenAIRE

    Lin, Andrew C; Holt, Christine E.

    2008-01-01

    Nerve growth factor induces sensory neuron survival via retrograde signalling from the axon to the cell body. Local translation of the transcription factor CREB in the axon, followed by its transport to the nucleus, is involved in this process.

  14. Axon damage and repair in multiple sclerosis.

    OpenAIRE

    Perry, V.H.; Anthony, D. C.

    1999-01-01

    It is well known that within long-standing multiple sclerosis (MS) lesions there is axonal loss but whether it is an early or late event has been more difficult to establish. The use of immunocytochemical methods that reveal axonal end-bulbs is a valuable approach to investigating acute axonal injury in human pathological material. The application of these techniques to multiple sclerosis tissue reveals evidence of axonal injury in acute lesions; the distribution of the end-bulbs in acute and...

  15. Axonal change in minor head injury.

    Science.gov (United States)

    Povlishock, J T; Becker, D P; Cheng, C L; Vaughan, G W

    1983-05-01

    Anterograde axonal transport of horseradish peroxidase (HRP) in selected cerebral and cerebellar efferents was studied in cats subjected to minor head injury. After trauma, the animals were allowed to survive from one to 24 hours, when they were perfused with aldehydes and processed for the light and electron microscopic visualization of the peroxidase reaction product. By light microscopy, the brain injury elicited an initial intra-axonal peroxidase pooling. With longer post-traumatic survival, HRP pooling increased in size, demonstrated frequent lobulation, and ultimately formed large ball- or club-like swellings which suggested frank axonal separation from the distal axonal segment. Ultrastructural examination revealed that the initial intra-axonal peroxidase pooling was associated with organelle accumulation which occurred without any other form of axonal change or related parenchymal or vascular damage. This accumulation of organelles increased with time and was associated with conspicuous axonal swelling. Ultimately these organelle-laden swellings lost continuity with the distal axonal segment and the axonal swelling was either completely invested by a thin myelin sheath or protruded without myelin investment into the brain parenchyma. This study suggests that axonal change is a consistent feature of minor head injury. Since these axonal changes occurred without any evidence of focal parenchymal or vascular damage, minor brain injury may ultimately disrupt axons without physically shearing or tearing them. PMID:6188807

  16. Amphioxus (Branchiostoma floridae has orthologs of vertebrate odorant receptors

    Directory of Open Access Journals (Sweden)

    Taylor John S

    2009-10-01

    Full Text Available Abstract Background A common feature of chemosensory systems is the involvement of G protein-coupled receptors (GPCRs in the detection of environmental stimuli. Several lineages of GPCRs are involved in vertebrate olfaction, including trace amine-associated receptors, type 1 and 2 vomeronasal receptors and odorant receptors (ORs. Gene duplication and gene loss in different vertebrate lineages have lead to an enormous amount of variation in OR gene repertoire among species; some fish have fewer than 100 OR genes, while some mammals possess more than 1000. Fascinating features of the vertebrate olfactory system include allelic exclusion, where each olfactory neuron expresses only a single OR gene, and axonal guidance where neurons expressing the same receptor project axons to common glomerulae. By identifying homologous ORs in vertebrate and in non-vertebrate chordates, we hope to expose ancestral features of the chordate olfactory system that will help us to better understand the evolution of the receptors themselves and of the cellular components of the olfactory system. Results We have identified 50 full-length and 11 partial ORs in Branchiostoma floridae. No ORs were identified in Ciona intestinalis. Phylogenetic analysis places the B. floridae OR genes in a monophyletic clade with the vertebrate ORs. The majority of OR genes in amphioxus are intronless and many are also tandemly arrayed in the genome. By exposing conserved amino acid motifs and testing the ability of those motifs to discriminate between ORs and non-OR GPCRs, we identified three OR-specific amino acid motifs common in cephalochordate, fish and mammalian and ORs. Conclusion Here, we show that amphioxus has orthologs of vertebrate ORs. This conclusion demonstrates that the receptors, and perhaps other components of vertebrate olfaction, evolved at least 550 million years ago. We have also identified highly conserved amino acid motifs that may be important for maintaining

  17. Differential subcellular recruitment of monoacylglycerol lipase generates spatial specificity of 2-arachidonoyl glycerol signaling during axonal pathfinding

    Science.gov (United States)

    Keimpema, Erik; Barabas, Klaudia; Morozov, Yury M.; Tortoriello, Giuseppe; Torii, Masaaki; Cameron, Gary; Yanagawa, Yuchio; Watanabe, Masahiko; Mackie, Ken; Harkany, Tibor

    2010-01-01

    Endocannabinoids, particularly 2-arachidonoyl glycerol (2-AG), impact the directional turning and motility of a developing axon by activating CB1 cannabinoid receptors (CB1Rs) in its growth cone. Recent findings posit that sn-1-diacylglycerol lipases (DAGLα/β) synthesize 2-AG in the motile axon segment of developing pyramidal cells. Coincident axonal targeting of CB1Rs and DAGLs prompts the hypothesis that autocrine 2-AG signaling facilitates axonal outgrowth. However, DAGLs alone are insufficient to account for the spatial specificity and dynamics of 2-AG signaling. Therefore, we hypothesized that local 2-AG degradation by monoacylglycerol lipase (MGL) must play a role. We determined how subcellular recruitment of MGL is temporally and spatially restricted to establish 2-AG’s signaling competence during axonal growth. MGL is expressed in central and peripheral axons of the fetal nervous system by embryonic day 12.5. MGL coexists with DAGLα and CB1Rs in corticofugal axons of pyramidal cells. Here, MGL and DAGLα undergo differential axonal targeting with MGL being excluded from the motile neurite tip. Thus, spatially-confined MGL activity generates a 2-AG-sensing microdomain and configures 2-AG signaling to promote axonal growth. Once synaptogenesis commences, MGL disperses in stationary growth cones. MGL’s axonal polarity is maintained by differential proteasomal degradation since inhibiting the ubiquitin proteasome system also induces axonal MGL redistribution. Since MGL inactivation drives a CB1R-dependent axonal growth response we conclude that 2-AG may act as a focal protrusive signal for developing neurons and whose regulated metabolism is critical for attaining correct axonal complexity. PMID:20962221

  18. Abundant expression of guidance and synaptogenic molecules in the injured spinal cord.

    Directory of Open Access Journals (Sweden)

    Anne Jacobi

    Full Text Available BACKGROUND: Spinal interneurons have emerged as crucial targets of supraspinal input during post-injury axonal remodelling. For example, lesioned corticospinal projections use propriospinal neurons as relay stations to form intraspinal detour circuits that circumvent the lesion site and contribute to functional recovery. While a number of the molecules that determine the formation of neuronal circuits in the developing nervous system have been identified, it is much less understood which of these cues are also expressed in the injured spinal cord and can thus guide growing collaterals and initiate synaptogenesis during circuit remodelling. METHODOLOGY/PRINCIPAL FINDINGS: To address this question we characterized the expression profile of a number of guidance and synaptogenic molecules in the cervical spinal cord of healthy and spinal cord-injured mice by in situ hybridization. To assign the expression of these molecules to distinct populations of interneurons we labeled short and long propriospinal neurons by retrograde tracing and glycinergic neurons using a transgenically expressed fluorescent protein. Interestingly, we found that most of the molecules studied including members of slit-, semaphorin-, synCAM-, neuroligin- and ephrin- families as well as their receptors are also present in the adult CNS. While many of these molecules were abundantly expressed in all interneurons examined, some molecules including slits, semaphorin 7a, synCAM4 and neuroligin 1 showed preferential expression in propriospinal interneurons. Overall the expression pattern of guidance and synaptogenic molecules in the cervical spinal cord appeared to be stable over time and was not substantially altered following a midthoracic spinal cord injury. CONCLUSIONS: Taken together, our study indicates that many of the guidance and synaptogenic cues that regulate neuronal circuit formation in development are also present in the adult CNS and therefore likely contribute to the

  19. Human intraretinal myelination: Axon diameters and axon/myelin thickness ratios

    Science.gov (United States)

    FitzGibbon, Thomas; Nestorovski, Zoran

    2013-01-01

    Purpose: Human intraretinal myelination of ganglion cell axons occurs in about 1% of the population. We examined myelin thickness and axon diameter in human retinal specimens containing myelinated retinal ganglion cell axons. Materials and Methods: Two eyes containing myelinated patches were prepared for electron microscopy. Two areas were examined in one retina and five in the second retina. Measurements were compared to normal retinal and optic nerve samples and the rabbit retina, which normally contains myelinated axons. Measurements were made using a graphics tablet. Results: Mean axon diameter of myelinated axons at all locations were significantly larger than unmyelinated axons (P ≤ 0.01). Myelinated axons within the patches were significantly larger than axons within the optic nerve (P < 0.01). The relationship between axon diameter/fiber diameter (the G-ratio) seen in the retinal sites differed from that in the nerve. G-ratios were higher and myelin thickness was positively correlated to axon diameter (P < 0.01) in the retina but negatively correlated to axon diameter in the nerve (P < 0.001). Conclusion: Intraretinally myelinated axons are larger than non-myelinated axons from the same population and suggests that glial cells can induce diameter changes in retinal axons that are not normally myelinated. This effect is more dramatic on intraretinal axons compared with the normal transition zone as axons enter the optic nerve and these changes are abnormal. Whether intraretinal myelin alters axonal conduction velocity or blocks axonal conduction remains to be clarified and these issues may have different clinical outcomes. PMID:24212308

  20. Differential expression of axon-sorting molecules in mouse olfactory sensory neurons.

    Science.gov (United States)

    Ihara, Naoki; Nakashima, Ai; Hoshina, Naosuke; Ikegaya, Yuji; Takeuchi, Haruki

    2016-08-01

    In the mouse olfactory system, the axons of olfactory sensory neurons that express the same type of odorant receptor (OR) converge to a specific set of glomeruli in the olfactory bulb (OB). It is widely accepted that expressed OR molecules instruct glomerular segregation by regulating the expression of axon-sorting molecules. Although the relationship between the expression of axon-sorting molecules and OR types has been analyzed in detail, those between the expressions of axon-sorting molecules remain to be elucidated. Here we collected the expression profiles of four axon-sorting molecules from a large number of glomeruli in the OB. These molecules demonstrated position-independent mosaic expressions, but their patterns were not identical in the OB. Comparing their expressions identified positive and negative correlations between several pairs of genes even though they showed various expressions. Furthermore, the principal component analysis revealed that the factor loadings in the principal component 1, which explain the largest amount of variation, were most likely to reflect the degree of the cyclic nucleotide-gated (CNG) channel dependence on the expression of axon-sorting molecules. Thus, neural activity generated through the CNG channel is a major component in the generation of a wide variety of expressions of axon-sorting molecules in glomerular segregation. PMID:27207328

  1. Missed connections: photoreceptor axon seeks target neuron for synaptogenesis.

    Science.gov (United States)

    Astigarraga, Sergio; Hofmeyer, Kerstin; Treisman, Jessica E

    2010-08-01

    Extending axons must choose the appropriate synaptic target cells in order to assemble functional neural circuitry. The axons of the Drosophila color-sensitive photoreceptors R7 and R8 project as a single fascicle from each ommatidium, but their terminals are segregated into distinct layers within their target region. Recent studies have begun to reveal the molecular mechanisms that establish this projection pattern. Both homophilic adhesion molecules and specific ligand-receptor interactions make important contributions to stabilizing R7 and R8 terminals in the appropriate target layers. These cell recognition molecules are regulated by the same transcription factors that control R7 and R8 cell fates. Autocrine and repulsive signaling mechanisms prevent photoreceptor terminals from encroaching on their neighbors, preserving the spatial resolution of visual information. PMID:20434326

  2. Inhibitory effects of draxin on axonal outgrowth and migration of precerebellar neurons.

    Science.gov (United States)

    Riyadh, M Asrafuzzaman; Shinmyo, Yohei; Ohta, Kunimasa; Tanaka, Hideaki

    2014-06-20

    The rhombic lip, a dorsal stripe of the neuroepithelium lining the edge of the fourth ventricle, is the site of origin of precerebellar neurons (PCN), which migrate tangentially towards the floor plate. After reaching the floor plate, they project their axons to the cerebellum. Although previous studies have shown that the guidance molecules Netrin/DCC and Slit/Robo have critical roles in PCN migration, the molecular mechanisms underlying this process remain poorly understood. Here, we report that draxin, a repulsive axon guidance protein, is involved in PCN development. We found that draxin is expressed in the rhombic lip and migratory stream of some PCN in the developing hindbrain of mice. In addition, draxin inhibited neurite outgrowth and nuclei migration from rhombic lip explants. These results suggest that draxin functions as a repulsive guidance cue for PCN migration. However, we observed no significant differences in PCN distribution between draxin(-/-) and wild type embryos. Thus, draxin and other axon guidance cues may have redundant roles in PCN migration.

  3. Perturbations of microRNA function in mouse dicer mutants produce retinal defects and lead to aberrant axon pathfinding at the optic chiasm.

    Directory of Open Access Journals (Sweden)

    Rita Pinter

    Full Text Available BACKGROUND: During development axons encounter a variety of choice points where they have to make appropriate pathfinding decisions. The optic chiasm is a major decision point for retinal ganglion cell (RGC axons en route to their target in order to ensure the correct wiring of the visual system. MicroRNAs (miRNAs belong to the class of small non-coding RNA molecules and have been identified as important regulators of a variety of processes during embryonic development. However, their involvement in axon guidance decisions is less clear. METHODOLOGY/PRINCIPAL FINDINGS: We report here that the early loss of Dicer, an essential protein for the maturation of miRNAs, in all cells of the forming retina and optic chiasm leads to severe phenotypes of RGC axon pathfinding at the midline. Using a conditional deletion approach in mice, we find in homozygous Dicer mutants a marked increase of ipsilateral projections, RGC axons extending outside the optic chiasm, the formation of a secondary optic tract and a substantial number of RGC axons projecting aberrantly into the contralateral eye. In addition, the mutant mice display a microphthalmia phenotype. CONCLUSIONS: Our work demonstrates an important role of Dicer controlling the extension of RGC axons to the brain proper. It indicates that miRNAs are essential regulatory elements for mechanisms that ensure correct axon guidance decisions at the midline and thus have a central function in the establishment of circuitry during the development of the nervous system.

  4. Fast and reliable identification of axons, axon initial segments and dendrites with local field potential recording

    Directory of Open Access Journals (Sweden)

    Anders Victor ePetersen

    2015-10-01

    Full Text Available The axon initial segment (AIS is an essential neuronal compartment. It is usually where action potentials are initiated. Recent studies demonstrated that the AIS is a plastic structure that can be regulated by neuronal activity and by the activation of metabotropic receptors. Studying the AIS in live tissue can be difficult because its identification is not always reliable. Here we provide a new technique allowing a fast and reliable identification of the AIS in live brain slice preparations. By simultaneous recoding of extracellular local field potentials and whole-cell patch-clamp recording of neurons, we can detect sinks caused by inward currents flowing across the membrane. We determine the location of the AIS by comparing the timing of these events with the action potential. We demonstrate that this method allows the unequivocal identification of the AIS of different types of neurons from the brain.

  5. Zebrafish foxP2 zinc finger nuclease mutant has normal axon pathfinding.

    Directory of Open Access Journals (Sweden)

    Lingyan Xing

    Full Text Available foxP2, a forkhead-domain transcription factor, is critical for speech and language development in humans, but its role in the establishment of CNS connectivity is unclear. While in vitro studies have identified axon guidance molecules as targets of foxP2 regulation, and cell culture assays suggest a role for foxP2 in neurite outgrowth, in vivo studies have been lacking regarding a role for foxP2 in axon pathfinding. We used a modified zinc finger nuclease methodology to generate mutations in the zebrafish foxP2 gene. Using PCR-based high resolution melt curve analysis (HRMA of G0 founder animals, we screened and identified three mutants carrying nonsense mutations in the 2(nd coding exon: a 17 base-pair (bp deletion, an 8bp deletion, and a 4bp insertion. Sequence analysis of cDNA confirmed that these were frameshift mutations with predicted early protein truncations. Homozygous mutant fish were viable and fertile, with unchanged body morphology, and no apparent differences in CNS apoptosis, proliferation, or patterning at embryonic stages. There was a reduction in expression of the known foxP2 target gene cntnap2 that was rescued by injection of wild-type foxP2 transcript. When we examined axon pathfinding using a pan-axonal marker or transgenic lines, including a foxP2-neuron-specific enhancer, we did not observe any axon guidance errors. Our findings suggest that foxP2 is not necessary for axon pathfinding during development.

  6. AxonSeg: Open Source Software for Axon and Myelin Segmentation and Morphometric Analysis.

    Science.gov (United States)

    Zaimi, Aldo; Duval, Tanguy; Gasecka, Alicja; Côté, Daniel; Stikov, Nikola; Cohen-Adad, Julien

    2016-01-01

    Segmenting axon and myelin from microscopic images is relevant for studying the peripheral and central nervous system and for validating new MRI techniques that aim at quantifying tissue microstructure. While several software packages have been proposed, their interface is sometimes limited and/or they are designed to work with a specific modality (e.g., scanning electron microscopy (SEM) only). Here we introduce AxonSeg, which allows to perform automatic axon and myelin segmentation on histology images, and to extract relevant morphometric information, such as axon diameter distribution, axon density and the myelin g-ratio. AxonSeg includes a simple and intuitive MATLAB-based graphical user interface (GUI) and can easily be adapted to a variety of imaging modalities. The main steps of AxonSeg consist of: (i) image pre-processing; (ii) pre-segmentation of axons over a cropped image and discriminant analysis (DA) to select the best parameters based on axon shape and intensity information; (iii) automatic axon and myelin segmentation over the full image; and (iv) atlas-based statistics to extract morphometric information. Segmentation results from standard optical microscopy (OM), SEM and coherent anti-Stokes Raman scattering (CARS) microscopy are presented, along with validation against manual segmentations. Being fully-automatic after a quick manual intervention on a cropped image, we believe AxonSeg will be useful to researchers interested in large throughput histology. AxonSeg is open source and freely available at: https://github.com/neuropoly/axonseg. PMID:27594833

  7. The Formin DAAM Functions as Molecular Effector of the Planar Cell Polarity Pathway during Axonal Development in Drosophila.

    Science.gov (United States)

    Gombos, Rita; Migh, Ede; Antal, Otilia; Mukherjee, Anindita; Jenny, Andreas; Mihály, József

    2015-07-15

    Recent studies established that the planar cell polarity (PCP) pathway is critical for various aspects of nervous system development and function, including axonal guidance. Although it seems clear that PCP signaling regulates actin dynamics, the mechanisms through which this occurs remain elusive. Here, we establish a functional link between the PCP system and one specific actin regulator, the formin DAAM, which has previously been shown to be required for embryonic axonal morphogenesis and filopodia formation in the growth cone. We show that dDAAM also plays a pivotal role during axonal growth and guidance in the adult Drosophila mushroom body, a brain center for learning and memory. By using a combination of genetic and biochemical assays, we demonstrate that Wnt5 and the PCP signaling proteins Frizzled, Strabismus, and Dishevelled act in concert with the small GTPase Rac1 to activate the actin assembly functions of dDAAM essential for correct targeting of mushroom body axons. Collectively, these data suggest that dDAAM is used as a major molecular effector of the PCP guidance pathway. By uncovering a signaling system from the Wnt5 guidance cue to an actin assembly factor, we propose that the Wnt5/PCP navigation system is linked by dDAAM to the regulation of the growth cone actin cytoskeleton, and thereby growth cone behavior, in a direct way.

  8. GABA increases electrical excitability in a subset of human unmyelinated peripheral axons.

    Directory of Open Access Journals (Sweden)

    Richard W Carr

    Full Text Available BACKGROUND: A proportion of small diameter primary sensory neurones innervating human skin are chemosensitive. They respond in a receptor dependent manner to chemical mediators of inflammation as well as naturally occurring algogens, thermogens and pruritogens. The neurotransmitter GABA is interesting in this respect because in animal models of neuropathic pain GABA pre-synaptically regulates nociceptive input to the spinal cord. However, the effect of GABA on human peripheral unmyelinated axons has not been established. METHODOLOGY/PRINCIPAL FINDINGS: Electrical stimulation was used to assess the effect of GABA on the electrical excitability of unmyelinated axons in isolated fascicles of human sural nerve. GABA (0.1-100 microM increased electrical excitability in a subset (ca. 40% of C-fibres in human sural nerve fascicles suggesting that axonal GABA sensitivity is selectively restricted to a sub-population of human unmyelinated axons. The effects of GABA were mediated by GABA(A receptors, being mimicked by bath application of the GABA(A agonist muscimol (0.1-30 microM while the GABA(B agonist baclofen (10-30 microM was without effect. Increases in excitability produced by GABA (10-30 microM were blocked by the GABA(A antagonists gabazine (10-20 microM, bicuculline (10-20 microM and picrotoxin (10-20 microM. CONCLUSIONS/SIGNIFICANCE: Functional GABA(A receptors are present on a subset of unmyelinated primary afferents in humans and their activation depolarizes these axons, an effect likely due to an elevated intra-axonal chloride concentration. GABA(A receptor modulation may therefore regulate segmental and peripheral components of nociception.

  9. Neurofilament spacing, phosphorylation, and axon diameter in regenerating and uninjured lamprey axons.

    Science.gov (United States)

    Pijak, D S; Hall, G F; Tenicki, P J; Boulos, A S; Lurie, D I; Selzer, M E

    1996-05-13

    It has been postulated that phosphorylation of the carboxy terminus sidearms of neurofilaments (NFs) increases axon diameter through repulsive electrostatic forces that increase sidearm extension and interfilament spacing. To evaluate this hypothesis, the relationships among NF phosphorylation, NF spacing, and axon diameter were examined in uninjured and spinal cord-transected larval sea lampreys (Petromyzon marinus). In untransected animals, axon diameters in the spinal cord varied from 0.5 to 50 microns. Antibodies specific for highly phosphorylated NFs labeled only large axons (> 10 microns), whereas antibodies for lightly phosphorylated NFs labeled medium-sized and small axons more darkly than large axons. For most axons in untransected animals, diameter was inversely related to NF packing density, but the interfilament distances of the largest axons were only 1.5 times those of the smallest axons. In addition, the lightly phosphorylated NFs of the small axons in the dorsal columns were widely spaced, suggesting that phosphorylation of NFs does not rigidly determine their spacing and that NF spacing does not rigidly determine axon diameter. Regenerating neurites of giant reticulospinal axons (GRAs) have diameters only 5-10% of those of their parent axons. If axon caliber is controlled by NF phosphorylation via mutual electrostatic repulsion, then NFs in the slender regenerating neurites should be lightly phosphorylated and densely packed (similar to NFs in uninjured small caliber axons), whereas NFs in the parent GRAs should be highly phosphorylated and loosely packed. However, although linear density of NFs (the number of NFs per micrometer) in these slender regenerating neurites was twice that in their parent axons, they were highly phosphorylated. Following sectioning of these same axons close to the cell body, axon-like neurites regenerated ectopically from dendritic tips. These ectopically regenerating neurites had NF linear densities 2.5 times those of

  10. Effects of medium flow on axon growth with or without nerve growth factor.

    Science.gov (United States)

    Kumamoto, Junichi; Kitahata, Hiroyuki; Goto, Makiko; Nagayama, Masaharu; Denda, Mitsuhiro

    2015-09-11

    Axon growth is a crucial process in regeneration of damaged nerves. On the other hand, elongation of nerve fibers in the epidermis has been observed in skin of atopic dermatitis patients. Thus, regulation of nerve fiber extension might be an effective strategy to accelerate nerve regeneration and/or to reduce itching in pruritus dermatosis. We previously demonstrated that neurons and epidermal keratinocytes similarly contain multiple receptors that are activated by various environmental factors, and in particular, keratinocytes are influenced by shear stress. Thus, in the present study, we evaluated the effects of micro-flow of the medium on axon growth in the presence or absence of nerve growth factor (NGF), using cultured dorsal-root-ganglion (DRG) cells. The apparatus, AXIS™, consists of two chambers connected by a set of microgrooves, through which signaling molecules and axons, but not living cells, can pass. When DRG cells were present in chamber 1, NGF was present in chamber 2, and micro-flow was directed from chamber 1 to chamber 2, axon growth was significantly increased compared with other conditions. Acceleration of axon growth in the direction of the micro-flow was also observed in the absence of NGF. These results suggest that local micro-flow might significantly influence axon growth. PMID:26212442

  11. Cable energy function of cortical axons.

    Science.gov (United States)

    Ju, Huiwen; Hines, Michael L; Yu, Yuguo

    2016-01-01

    Accurate estimation of action potential (AP)-related metabolic cost is essential for understanding energetic constraints on brain connections and signaling processes. Most previous energy estimates of the AP were obtained using the Na(+)-counting method, which seriously limits accurate assessment of metabolic cost of ionic currents that underlie AP conduction along the axon. Here, we first derive a full cable energy function for cortical axons based on classic Hodgkin-Huxley (HH) neuronal equations and then apply the cable energy function to precisely estimate the energy consumption of AP conduction along axons with different geometric shapes. Our analytical approach predicts an inhomogeneous distribution of metabolic cost along an axon with either uniformly or nonuniformly distributed ion channels. The results show that the Na(+)-counting method severely underestimates energy cost in the cable model by 20-70%. AP propagation along axons that differ in length may require over 15% more energy per unit of axon area than that required by a point model. However, actual energy cost can vary greatly depending on axonal branching complexity, ion channel density distributions, and AP conduction states. We also infer that the metabolic rate (i.e. energy consumption rate) of cortical axonal branches as a function of spatial volume exhibits a 3/4 power law relationship. PMID:27439954

  12. Neuronal Development: SAD Kinases Make Happy Axons

    OpenAIRE

    Xing, Lei; Newbern, Jason M.; Snider, William D

    2013-01-01

    The polarity proteins LKB1 and SAD-A/B are key regulators of axon specification in the developing cerebral cortex. Recent studies now show that this mechanism cannot be generalized to other classes of neurons: instead, SAD-A/B functions downstream of neurotrophin signaling in sensory neurons to mediate a later stage of axon development — arborization in the target field.

  13. Axon reflexes in human cold exposed fingers

    NARCIS (Netherlands)

    Daanen, H.A.M.; Ducharme, M.B.

    2000-01-01

    Exposure of fingers to severe cold induces cold induced vasodilation (CIVD). The mechanism of CIVD is still debated. The original theory states that an axon reflex causes CIVD. To test this hypothesis, axon reflexes were evoked by electrical stimulation of the middle fingers of hands immersed in wat

  14. Cable energy function of cortical axons.

    Science.gov (United States)

    Ju, Huiwen; Hines, Michael L; Yu, Yuguo

    2016-01-01

    Accurate estimation of action potential (AP)-related metabolic cost is essential for understanding energetic constraints on brain connections and signaling processes. Most previous energy estimates of the AP were obtained using the Na(+)-counting method, which seriously limits accurate assessment of metabolic cost of ionic currents that underlie AP conduction along the axon. Here, we first derive a full cable energy function for cortical axons based on classic Hodgkin-Huxley (HH) neuronal equations and then apply the cable energy function to precisely estimate the energy consumption of AP conduction along axons with different geometric shapes. Our analytical approach predicts an inhomogeneous distribution of metabolic cost along an axon with either uniformly or nonuniformly distributed ion channels. The results show that the Na(+)-counting method severely underestimates energy cost in the cable model by 20-70%. AP propagation along axons that differ in length may require over 15% more energy per unit of axon area than that required by a point model. However, actual energy cost can vary greatly depending on axonal branching complexity, ion channel density distributions, and AP conduction states. We also infer that the metabolic rate (i.e. energy consumption rate) of cortical axonal branches as a function of spatial volume exhibits a 3/4 power law relationship.

  15. Cable energy function of cortical axons

    Science.gov (United States)

    Ju, Huiwen; Hines, Michael L.; Yu, Yuguo

    2016-01-01

    Accurate estimation of action potential (AP)-related metabolic cost is essential for understanding energetic constraints on brain connections and signaling processes. Most previous energy estimates of the AP were obtained using the Na+-counting method, which seriously limits accurate assessment of metabolic cost of ionic currents that underlie AP conduction along the axon. Here, we first derive a full cable energy function for cortical axons based on classic Hodgkin-Huxley (HH) neuronal equations and then apply the cable energy function to precisely estimate the energy consumption of AP conduction along axons with different geometric shapes. Our analytical approach predicts an inhomogeneous distribution of metabolic cost along an axon with either uniformly or nonuniformly distributed ion channels. The results show that the Na+-counting method severely underestimates energy cost in the cable model by 20–70%. AP propagation along axons that differ in length may require over 15% more energy per unit of axon area than that required by a point model. However, actual energy cost can vary greatly depending on axonal branching complexity, ion channel density distributions, and AP conduction states. We also infer that the metabolic rate (i.e. energy consumption rate) of cortical axonal branches as a function of spatial volume exhibits a 3/4 power law relationship. PMID:27439954

  16. Effect of Long-Term Cannabis Use on Axonal Fibre Connectivity

    Science.gov (United States)

    Zalesky, Andrew; Solowij, Nadia; Yucel, Murat; Lubman, Dan I.; Takagi, Michael; Harding, Ian H.; Lorenzetti, Valentina; Wang, Ruopeng; Searle, Karissa; Pantelis, Christos; Seal, Marc

    2012-01-01

    Cannabis use typically begins during adolescence and early adulthood, a period when cannabinoid receptors are still abundant in white matter pathways across the brain. However, few studies to date have explored the impact of regular cannabis use on white matter structure, with no previous studies examining its impact on axonal connectivity. The…

  17. The challenges of axon survival: introduction to the special issue on axonal degeneration.

    Science.gov (United States)

    Coleman, Michael P

    2013-08-01

    Early axon loss is a common feature of many neurodegenerative disorders. It renders neurons functionally inactive, or less active if axon branches are lost, in a manner that is often irreversible. In the CNS, there is no long-range axon regeneration and even peripheral nerve axons are unlikely to reinnervate their targets while the cause of the problem persists. In most disorders, axon degeneration precedes cell death so it is not simply a consequence of it, and it is now clear that axons have at least one degeneration mechanism that differs from that of the soma. It is important to understand these degeneration mechanisms and their contribution to axon loss in neurodegenerative disorders. In this way, it should become possible to prevent axon loss as well as cell death. This special edition considers the roles and mechanisms of axon degeneration in amyotrophic lateral sclerosis, Charcot-Marie-Tooth disease, hereditary spastic paraplegia, ischemic injury, traumatic brain injury, Alzheimer's disease, glaucoma, Huntington's disease and Parkinson's disease. Using examples from these and other disorders, this introduction considers some of the reasons for axon vulnerability. It also illustrates how molecular genetics and studies of Wallerian degeneration have contributed to our understanding of axon degeneration mechanisms. PMID:23769907

  18. Sugar Antennae for Guidance Signals: Syndecans and Glypicans Integrate Directional Cues for Navigating Neurons

    OpenAIRE

    Christa Rhiner; Hengartner, Michael O.

    2006-01-01

    Attractive and repulsive signals guide migrating nerve cells in all directions when the nervous system starts to form. The neurons extend thin processes, axons, that connect over wide distances with other brain cells to form a complicated neuronal network. One of the most fascinating questions in neuroscience is how the correct wiring of billions of nerve cells in our brain is controlled. Several protein families are known to serve as guidance cues for navigating neurons and axons. Neverthele...

  19. Dynamics of mitochondrial transport in axons

    Directory of Open Access Journals (Sweden)

    Robert Francis Niescier

    2016-05-01

    Full Text Available The polarized structure and long neurites of neurons pose a unique challenge for proper mitochondrial distribution. It is widely accepted that mitochondria move from the cell body to axon ends and vice versa; however, we have found that mitochondria originating from the axon ends moving in the retrograde direction never reach to the cell body, and only a limited number of mitochondria moving in the anterograde direction from the cell body arrive at the axon ends of mouse hippocampal neurons. Furthermore, we have derived a mathematical formula using the Fokker-Planck equation to characterize features of mitochondrial transport, and the equation could determine altered mitochondrial transport in axons overexpressing parkin. Our analysis will provide new insights into the dynamics of mitochondrial transport in axons of normal and unhealthy neurons.

  20. Dynamics of Mitochondrial Transport in Axons.

    Science.gov (United States)

    Niescier, Robert F; Kwak, Sang Kyu; Joo, Se Hun; Chang, Karen T; Min, Kyung-Tai

    2016-01-01

    The polarized structure and long neurites of neurons pose a unique challenge for proper mitochondrial distribution. It is widely accepted that mitochondria move from the cell body to axon ends and vice versa; however, we have found that mitochondria originating from the axon ends moving in the retrograde direction never reach to the cell body, and only a limited number of mitochondria moving in the anterograde direction from the cell body arrive at the axon ends of mouse hippocampal neurons. Furthermore, we have derived a mathematical formula using the Fokker-Planck equation to characterize features of mitochondrial transport, and the equation could determine altered mitochondrial transport in axons overexpressing parkin. Our analysis will provide new insights into the dynamics of mitochondrial transport in axons of normal and unhealthy neurons. PMID:27242435

  1. PACAP enhances axon outgrowth in cultured hippocampal neurons to a comparable extent as BDNF.

    Directory of Open Access Journals (Sweden)

    Katsuya Ogata

    Full Text Available Pituitary adenylate cyclase-activating polypeptide (PACAP exerts neurotrophic activities including modulation of synaptic plasticity and memory, hippocampal neurogenesis, and neuroprotection, most of which are shared with brain-derived neurotrophic factor (BDNF. Therefore, the aim of this study was to compare morphological effects of PACAP and BDNF on primary cultured hippocampal neurons. At days in vitro (DIV 3, PACAP increased neurite length and number to similar levels by BDNF, but vasoactive intestinal polypeptide showed much lower effects. In addition, PACAP increased axon, but not dendrite, length, and soma size at DIV 3 similarly to BDNF. The PACAP antagonist PACAP6-38 completely blocked the PACAP-induced increase in axon, but not dendrite, length. Interestingly, the BDNF-induced increase in axon length was also inhibited by PACAP6-38, suggesting a mechanism involving PACAP signaling. K252a, a TrkB receptor inhibitor, inhibited axon outgrowth induced by PACAP and BDNF without affecting dendrite length. These results indicate that in primary cultured hippocampal neurons, PACAP shows morphological actions via its cognate receptor PAC1, stimulating neurite length and number, and soma size to a comparable extent as BDNF, and that the increase in total neurite length is ascribed to axon outgrowth.

  2. 急性肺损伤大鼠肺组织神经导向因子Slit2及Robo4的表达%Expression of axon guidance cues Slit2 and Robo4 in lung tissue of rat with acute lung injury

    Institute of Scientific and Technical Information of China (English)

    李霖; 卿国忠; 杨靖; 唐卓; 彭正良; 张克娜; 丁灿

    2014-01-01

    .09) vs.(0.50±0.05),F=0.498,P>0.05,(0.55±0.06) vs.(0.56±0.07),F=0.073,P>0.05].结论 对照组大鼠肺组织可表达Slit2及Robo4,盲肠结扎穿孔致ALI大鼠肺组织Slit2表达下降,这可能与ALI发病有关.%Objective To observe the expression of axon guidance cues Slit2 and Robo4 in lung tissue of rat with acute lung injury (ALI) and explore the function of Slit2 and Robo4 in ALI.Methods Forty-eight Sprague-Dawley rats were randomly (random number) divided into control group (n =24) and ALl group (n =24).ALI model was reproduced by cecum ligation and puncture (CLP).The control group only experienced a simulated operation without CLP.Both groups were further divided into 3 subgroups with 8 rats in each subgroup:12 h,24 h,and 48 h subgroups.artery blood gas analysis,lung tissue wet/dry weight (W/D) ratio,lung histopathologic changes,pulmonary microvascular permeability were observed.The serum tumor nocrosis factor-α (TNF-α) was measured with enzyme linked immunosorbent assay (ELISA).The expression of Slit2 and Robo4 mRNA were detected by reverse transcription-polymerase chain reaction (RT-PCR).The expression of Slit2 and Robo4 protein in lung tissues was assessed by immunohistochemistry.Date were analyzed by one-way ANOVA with SPSS version 13.0 software.Statistical significance was established at a P value of less than 0.05.Results Compared with the control group,in ALI rats at different time points,partial pressure of oxygen in arterial blood (PaO2) decreased significantly,lung W/D weight ratio and pulmonary microvascular permeability,the serum TNF-α increased significantly (all P < 0.05),histopathology of lung revealed signs of injury.The expression of Slit2 mRNA in lung tissues was decreased markedly after CLP compared with control group [(0.56±0.13) vs.(0.87±0.05),F=41.39,P<0.05,(0.42±0.10) vs.(0.85±0.07),F=93.54,P<0.05,(0.26±0.08) vs.(0.89 ±0.09),F=227.05,P<0.05].but there were no significant difference in expression of Robo4 mRNA in

  3. Bazooka mediates secondary axon morphology in Drosophila brain lineages

    Directory of Open Access Journals (Sweden)

    Hartenstein Volker

    2011-04-01

    Full Text Available Abstract In the Drosophila brain, neural lineages project bundled axon tracts into a central neuropile. Each lineage exhibits a stereotypical branching pattern and trajectory, which distinguish it from other lineages. In this study, we used a multilineage approach to explore the neural function of the Par-complex member Par3/Bazooka in vivo. Drosophila bazooka is expressed in post-mitotic neurons of the larval brain and localizes within neurons in a lineage-dependent manner. The fact that multiple GAL4 drivers have been mapped to several lineages of the Drosophila brain enables investigation of the role of Bazooka from larval to adult stages Bazooka loss-of-function (LOF clones had abnormal morphologies, including aberrant pathway choice of ventral projection neurons in the BAla1 lineage, ectopic branching in the DALv2 and BAmv1 lineages, and excess BLD5 lineage axon projections in the optic medulla. Exogenous expression of Bazooka protein in BAla1 neurons rescued defective guidance, supporting an intrinsic requirement for Bazooka in the post-mitotic neuron. Elimination of the Par-complex member Par6 recapitulated Bazooka phenotypes in some but not all lineages, suggesting that the Par complex functions in a lineage-dependent manner, and that Bazooka may act independently in some lineages. Importantly, this study highlights the potential of using a multilineage approach when studying gene function during neural development in Drosophila.

  4. Bazooka mediates secondary axon morphology in Drosophila brain lineages.

    Science.gov (United States)

    Spindler, Shana R; Hartenstein, Volker

    2011-01-01

    In the Drosophila brain, neural lineages project bundled axon tracts into a central neuropile. Each lineage exhibits a stereotypical branching pattern and trajectory, which distinguish it from other lineages. In this study, we used a multilineage approach to explore the neural function of the Par-complex member Par3/Bazooka in vivo. Drosophila bazooka is expressed in post-mitotic neurons of the larval brain and localizes within neurons in a lineage-dependent manner. The fact that multiple GAL4 drivers have been mapped to several lineages of the Drosophila brain enables investigation of the role of Bazooka from larval to adult stages Bazooka loss-of-function (LOF) clones had abnormal morphologies, including aberrant pathway choice of ventral projection neurons in the BAla1 lineage, ectopic branching in the DALv2 and BAmv1 lineages, and excess BLD5 lineage axon projections in the optic medulla. Exogenous expression of Bazooka protein in BAla1 neurons rescued defective guidance, supporting an intrinsic requirement for Bazooka in the post-mitotic neuron. Elimination of the Par-complex member Par6 recapitulated Bazooka phenotypes in some but not all lineages, suggesting that the Par complex functions in a lineage-dependent manner, and that Bazooka may act independently in some lineages. Importantly, this study highlights the potential of using a multilineage approach when studying gene function during neural development in Drosophila. PMID:21524279

  5. Sugar Antennae for Guidance Signals: Syndecans and Glypicans Integrate Directional Cues for Navigating Neurons

    Directory of Open Access Journals (Sweden)

    Christa Rhiner

    2006-01-01

    Full Text Available Attractive and repulsive signals guide migrating nerve cells in all directions when the nervous system starts to form. The neurons extend thin processes, axons, that connect over wide distances with other brain cells to form a complicated neuronal network. One of the most fascinating questions in neuroscience is how the correct wiring of billions of nerve cells in our brain is controlled. Several protein families are known to serve as guidance cues for navigating neurons and axons. Nevertheless, the combinatorial potential of these proteins seems to be insufficient to sculpt the entire neuronal network and the appropriate formation of connections. Recently, heparan sulfate proteoglycans (HSPGs, which are present on the cell surface of neurons and in the extracellular matrix through which neurons and axons migrate, have been found to play a role in regulating cell migration and axon guidance. Intriguingly, the large number of distinct modifications that can be put onto the sugar side chains of these PGs would in principle allow for an enormous diversity of HSPGs, which could help in regulating the vast number of guidance choices taken by individual neurons. In this review, we will focus on the role of the cell surface HSPGs syndecan and glypican and specific HS modifications in promoting neuronal migration, axon guidance, and synapse formation.

  6. TRIM-9 functions in the UNC-6/UNC-40 pathway to regulate ventral guidance

    Institute of Scientific and Technical Information of China (English)

    Song Song; Qinglan Ge; Jinbo Wang; Haiyang Chen; Sanyuan Tang; Junfeng Bi; Xia Li; Qi Xie; Xun Huang

    2011-01-01

    TRIpartite Motif (TRIM) family proteins are ring finger domain-containing, multi-domain proteins implicated in many biological processes.Members of the TRIM-9/C-I subfamily of TRIM proteins, including TRIM-9, MIDI and MID2, have neuronal functions and are associated with neurological diseases. To explore whether the functions of C-I TRIM proteins are conserved in invertebrates, we analyzed Caenorhabditis elegans and Drosophila trim-9 mutants. C. elegans trim-9 mutants exhibit defects in the ventral guidance of hermaphrodite specific neuron (HSN) and the touch neuron AVM. Further genetic analyses indicate that TRIM-9 participates in the UNC-6-UNC-40 attraction pathway.Asymmetric distribution of UNC-40 during HSN development is normal in trim-9 mutants. However, the asymmetric localization of MIG-10,a downstream effector of UNC-40, is abolished in trim-9 mutants. These results suggest that TRIM-9 functions upstream of MIG-1 0 in the UNC40 pathway. Moreover, we showed that TRIM-9 exhibits E3 ubiquitin ligase activity in vitro and this activity is important for TRIM-9 function in vivo. Additionally, we found that Drosophila trim-9 is required for the midline attraction of a group of sensory neuron axons. Over-expression of the Netrin/UNC-6 receptor Frazzled suppresses the guidance defects in trim-9 mutants. Our study reveals an evolutionarily conserved function of TRIM-9 in the UNC-40/Frazzled-mediated UNC-6/Netrin attraction pathway.

  7. Unc-51/ATG1 controls axonal and dendritic development via kinesin-mediated vesicle transport in the Drosophila brain.

    Directory of Open Access Journals (Sweden)

    Hiroaki Mochizuki

    Full Text Available BACKGROUND: Members of the evolutionary conserved Ser/Thr kinase Unc-51 family are key regulatory proteins that control neural development in both vertebrates and invertebrates. Previous studies have suggested diverse functions for the Unc-51 protein, including axonal elongation, growth cone guidance, and synaptic vesicle transport. METHODOLOGY/PRINCIPAL FINDINGS: In this work, we have investigated the functional significance of Unc-51-mediated vesicle transport in the development of complex brain structures in Drosophila. We show that Unc-51 preferentially accumulates in newly elongating axons of the mushroom body, a center of olfactory learning in flies. Mutations in unc-51 cause disintegration of the core of the developing mushroom body, with mislocalization of Fasciclin II (Fas II, an IgG-family cell adhesion molecule important for axonal guidance and fasciculation. In unc-51 mutants, Fas II accumulates in the cell bodies, calyx, and the proximal peduncle. Furthermore, we show that mutations in unc-51 cause aberrant overshooting of dendrites in the mushroom body and the antennal lobe. Loss of unc-51 function leads to marked accumulation of Rab5 and Golgi components, whereas the localization of dendrite-specific proteins, such as Down syndrome cell adhesion molecule (DSCAM and No distributive disjunction (Nod, remains unaltered. Genetic analyses of kinesin light chain (Klc and unc-51 double heterozygotes suggest the importance of kinesin-mediated membrane transport for axonal and dendritic development. Moreover, our data demonstrate that loss of Klc activity causes similar axonal and dendritic defects in mushroom body neurons, recapitulating the salient feature of the developmental abnormalities caused by unc-51 mutations. CONCLUSIONS/SIGNIFICANCE: Unc-51 plays pivotal roles in the axonal and dendritic development of the Drosophila brain. Unc-51-mediated membrane vesicle transport is important in targeted localization of guidance molecules

  8. Transient axonal glycoprotein-1 induces apoptosis-related gene expression without triggering apoptosis in U251 glioma cells

    Institute of Scientific and Technical Information of China (English)

    Haigang Chang; Xiaodan Jiang; Shanshan Song; Zhongcan Chen; Yaxiao Wang; Lujun Yang; Mouxuan Du; Yiquan Ke; Ruxiang Xu; Baozhe Jin

    2014-01-01

    Previous studies show that transient axonal glycoprotein-1, a ligand of amyloid precursor pro-tein, increases the secretion of amyloid precursor protein intracellular domain and is involved in apoptosis in Alzheimer’s disease. In this study, we examined the effects of transient axonal glyco-protein-1 on U251 glioma cells. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay showed that transient axonal glycoprotein-1 did not inhibit the proliferation of U251 cells, but promoted cell viability. The terminal deoxynucleotidyl transferase dUTP nick end labeling assay showed that transient axonal glycoprotein-1 did not induce U251 cell apoptosis. Real-time PCR revealed that transient axonal glycoprotein-1 substantially upregulated levels of amyloid precursor protein intracellular C-terminal domain, and p53 and epidermal growth factor recep-tor mRNA expression. Thus, transient axonal glycoprotein-1 increased apoptosis-related gene expression in U251 cells without inducing apoptosis. Instead, transient axonal glycoprotein-1 promoted the proliferation of these glioma cells.

  9. Genetics Home Reference: giant axonal neuropathy

    Science.gov (United States)

    ... in giant axonal neuropathy: new insights into disease mechanisms. Muscle Nerve. 2012 Aug;46(2):246-56. ... with a qualified healthcare professional . About Genetics Home Reference Site Map Contact Us Selection Criteria for Links ...

  10. Synapse formation between isolated axons requires presynaptic soma and redistribution of postsynaptic AChRs.

    Science.gov (United States)

    Meems, Ryanne; Munno, David; van Minnen, Jan; Syed, Naweed I

    2003-05-01

    The involvement of neuronal protein synthetic machinery and extrinsic trophic factors during synapse formation is poorly understood. Here we determine the roles of these processes by reconstructing synapses between the axons severed from identified Lymnaea neurons in cell culture, either in the presence or absence of trophic factors. We demonstrate that, although synapses are maintained between isolated pre- and postsynaptic axons for several days, the presynaptic, but not the postsynaptic, cell body, however, is required for new synapse formation between soma-axon pairs. The formation of cholinergic synapses between presynaptic soma and postsynaptic axon requires gene transcription and protein synthesis solely in the presynaptic neuron. We show that this synaptogenesis is contingent on extrinsic trophic factors present in brain conditioned medium (CM). The CM-induced excitatory synapse formation is mediated through receptor tyrosine kinases. We further demonstrate that, although the postsynaptic axon does not require new protein synthesis for synapse formation, its contact with the presynaptic cell in CM, but not in defined medium (no trophic factors), differentially alters its responsiveness to exogenously applied acetylcholine at synaptic compared with extrasynaptic sites. Together, these data suggest a synergetic action of cell-cell signaling and trophic factors to bring about specific changes in both pre- and postsynaptic neurons during synapse formation.

  11. Frizzled-3a and slit2 genetically interact to modulate midline axon crossing in the telencephalon.

    Science.gov (United States)

    Hofmeister, Wolfgang; Devine, Christine A; Rothnagel, Joseph A; Key, Brian

    2012-07-01

    The anterior commissure forms the first axon connections between the two sides of the embryonic telencephalon. We investigated the role of the transmembrane receptor Frizzled-3a in the development of this commissure using zebrafish as an experimental model. Knock down of Frizzled-3a resulted in complete loss of the anterior commissure. This defect was accompanied by a loss of the glial bridge, expansion of the slit2 expression domain and perturbation of the midline telencephalic-diencephalic boundary. Blocking Slit2 activity following knock down of Frizzled-3a effectively rescued the anterior commissure defect which suggested that Frizzled-3a was indirectly controlling the growth of axons across the rostral midline. We have shown here that Frizzled-3a is essential for normal development of the commissural plate and that loss-of-function causes Slit2-dependent defects in axon midline crossing in the embryonic vertebrate forebrain. These data supports a model whereby Wnt signaling through Frizzled-3a attenuates expression of Slit2 in the rostral midline of the forebrain. The absence of Slit2 facilitates the formation of a midline bridge of glial cells which is used as a substrate for commissural axons. In the absence of this platform of glia, commissural axons fail to cross the rostral midline of the forebrain.

  12. Developmental guidance of embryonic corneal innervation: roles of Semaphorin3A and Slit2.

    Science.gov (United States)

    Kubilus, James K; Linsenmayer, Thomas F

    2010-08-01

    The cornea is one of the most densely innervated structures of the body. In the developing chicken embryo, nerves from the ophthalmic trigeminal ganglion (OTG) innervate the cornea in a series of spatially and temporally regulated events. However, little is known concerning the signals that regulate these events. Here we have examined the involvement of the axon guidance molecules Semaphorin3A and Slit2, and their respective receptors, Neuropilin-1 and Robo2. Expression analyses of early corneas suggest an involvement of both Semaphorin3A and Slit2 in preventing nerves from entering the corneal stroma until the proper time (i.e., they serve as negative regulators), and analyses of their receptors support this conclusion. At later stages of development the expression of Semaphorin3A is again consistent with its serving as a negative regulator-this time for nerves entering the corneal epithelium. However, expression analyses of Robo2 at this stage raised the possibility that Slit2 had switched from a negative regulator to a positive regulator. In support of such a switch, functional analyses-by addition of recombinant Slit2 protein or immunoneutralization with a Slit2 antibody-showed that at an early stage Slit2 negatively regulates the outgrowth of nerves from the OTG, whereas at the later stage it positively regulated the growth of nerves by increasing nerve branching within the corneal epithelium.

  13. The Netrin receptor Neogenin is required for neural tube formation and somitogenesis in zebrafish.

    Science.gov (United States)

    Mawdsley, David J; Cooper, Helen M; Hogan, Benjamin M; Cody, Stephen H; Lieschke, Graham J; Heath, Joan K

    2004-05-01

    The Netrin receptor Deleted in colon cancer (Dcc) has been shown to play a pivotal role in the guidance of nascent axons towards the ventral midline in the developing nervous systems of both vertebrates and invertebrates. In contrast, the function during embryogenesis of a second Dcc-like Netrin receptor Neogenin has not yet been defined. We used antisense morpholino oligonucleotides to knockdown Neogenin activity in zebrafish embryos and demonstrate that Neogenin plays an important role in neural tube formation and somitogenesis. In Neogenin knockdown embryos, cavitation within the neural rod failed to occur, producing a neural tube lacking a lumen. Somite formation was also defective, implicating Neogenin in the migration events underlying convergent extension during gastrulation. These observations suggest a role for Neogenin in determining cell polarity or migrational directionality of both neuroectodermal and mesodermal cells during early embryonic development.

  14. Co-culture of oligodendrocytes and neurons can be used to assess drugs for axon regeneration in the central nervous system.

    Science.gov (United States)

    Gang, Lin; Yao, Yu-Chen; Liu, Ying-Fu; Li, Yi-Peng; Yang, Kai; Lu, Lei; Cheng, Yuan-Chi; Chen, Xu-Yi; Tu, Yue

    2015-10-01

    We present a novel in vitro model in which to investigate the efficacy of experimental drugs for the promotion of axon regeneration in the central nervous system. We co-cultured rat hippocampal neurons and cerebral cortical oligodendrocytes, and tested the co-culture system using a Nogo-66 receptor antagonist peptide (NEP1-40), which promotes axonal growth. Primary cultured oligodendrocytes suppressed axonal growth in the rat hippocampus, but NEP1-40 stimulated axonal growth in the co-culture system. Our results confirm the validity of the neuron-oligodendrocyte co-culture system as an assay for the evaluation of drugs for axon regeneration in the central nervous system.

  15. Co-culture of oligodendrocytes and neurons can be used to assess drugs for axon regeneration in the central nervous system

    Directory of Open Access Journals (Sweden)

    Lin Gang

    2015-01-01

    Full Text Available We present a novel in vitro model in which to investigate the efficacy of experimental drugs for the promotion of axon regeneration in the central nervous system. We co-cultured rat hippocampal neurons and cerebral cortical oligodendrocytes, and tested the co-culture system using a Nogo-66 receptor antagonist peptide (NEP1-40, which promotes axonal growth. Primary cultured oligodendrocytes suppressed axonal growth in the rat hippocampus, but NEP1-40 stimulated axonal growth in the co-culture system. Our results confirm the validity of the neuron-oligodendrocyte co-culture system as an assay for the evaluation of drugs for axon regeneration in the central nervous system.

  16. Graphical Turbulence Guidance - Composite

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Forecast turbulence hazards identified by the Graphical Turbulence Guidance algorithm. The Graphical Turbulence Guidance product depicts mid-level and upper-level...

  17. receptores

    Directory of Open Access Journals (Sweden)

    Salete Regina Daronco Benetti

    2006-01-01

    Full Text Available Se trata de un estudio etnográfico, que tuvo lo objetivo de interpretar el sistema de conocimiento y del significado atribuidos a la sangre referente a la transfusión sanguínea por los donadores y receptores de un banco de sangre. Para la colecta de las informaciones se observaron los participantes y la entrevista etnográfica se realizó el análisis de dominio, taxonómicos y temáticos. Los dominios culturales fueron: la sangre es vida: fuente de vida y alimento valioso; creencias religiosas: fuentes simbólicas de apoyos; donación sanguínea: un gesto colaborador que exige cuidarse, gratifica y trae felicidad; donación sanguínea: fuente simbólica de inseguridad; estar enfermo es una condición para realizar transfusión sanguínea; transfusión sanguínea: esperanza de vida; Creencias populares: transfusión sanguínea como riesgo para la salud; donadores de sangre: personas benditas; donar y recibir sangre: como significado de felicidad. Temática: “líquido precioso que origina, sostiene, modifica la vida, provoca miedo e inseguridad”.

  18. Microfluidic device for unidirectional axon growth

    Science.gov (United States)

    Malishev, E.; Pimashkin, A.; Gladkov, A.; Pigareva, Y.; Bukatin, A.; Kazantsev, V.; Mukhina, I.; Dubina, M.

    2015-11-01

    In order to better understand the communication and connectivity development of neuron networks, we designed microfluidic devices with several chambers for growing dissociated neuronal cultures from mice fetal hippocampus (E18). The chambers were connected with microchannels providing unidirectional axonal growth between “Source” and “Target” neural sub-networks. Experiments were performed in a hippocampal cultures plated in a poly-dimethylsiloxane (PDMS) microfluidic chip, aligned with a 60 microelectrode array (MEA). Axonal growth through microchannels was observed with brightfield, phase-contrast and fluorescence microscopy, and after 7 days in vitro electrical activity was recorded. Visual inspection and spike propagation analysis showed the predominant axonal growth in microchannels in a direction from “Source” to “Target”.

  19. Diverse modes of axon elaboration in the developing neocortex.

    Directory of Open Access Journals (Sweden)

    2005-08-01

    Full Text Available The development of axonal arbors is a critical step in the establishment of precise neural circuits, but relatively little is known about the mechanisms of axonal elaboration in the neocortex. We used in vivo two-photon time-lapse microscopy to image axons in the neocortex of green fluorescent protein-transgenic mice over the first 3 wk of postnatal development. This period spans the elaboration of thalamocortical (TC and Cajal-Retzius (CR axons and cortical synaptogenesis. Layer 1 collaterals of TC and CR axons were imaged repeatedly over time scales ranging from minutes up to days, and their growth and pruning were analyzed. The structure and dynamics of TC and CR axons differed profoundly. Branches of TC axons terminated in small, bulbous growth cones, while CR axon branch tips had large growth cones with numerous long filopodia. TC axons grew rapidly in straight paths, with frequent interstitial branch additions, while CR axons grew more slowly along tortuous paths. For both types of axon, new branches appeared at interstitial sites along the axon shaft and did not involve growth cone splitting. Pruning occurred via retraction of small axon branches (tens of microns, at both CR and TC axons or degeneration of large portions of the arbor (hundreds of microns, for TC axons only. The balance between growth and retraction favored overall growth, but only by a slight margin. Given the identical layer 1 territory upon which CR and TC axons grow, the differences in their structure and dynamics likely reflect distinct intrinsic growth programs for axons of long projection neurons versus local interneurons.

  20. Automated Axon Counting in Rodent Optic Nerve Sections with AxonJ

    Science.gov (United States)

    Zarei, Kasra; Scheetz, Todd E.; Christopher, Mark; Miller, Kathy; Hedberg-Buenz, Adam; Tandon, Anamika; Anderson, Michael G.; Fingert, John H.; Abràmoff, Michael David

    2016-05-01

    We have developed a publicly available tool, AxonJ, which quantifies the axons in optic nerve sections of rodents stained with paraphenylenediamine (PPD). In this study, we compare AxonJ’s performance to human experts on 100x and 40x images of optic nerve sections obtained from multiple strains of mice, including mice with defects relevant to glaucoma. AxonJ produced reliable axon counts with high sensitivity of 0.959 and high precision of 0.907, high repeatability of 0.95 when compared to a gold-standard of manual assessments and high correlation of 0.882 to the glaucoma damage staging of a previously published dataset. AxonJ allows analyses that are quantitative, consistent, fully-automated, parameter-free, and rapid on whole optic nerve sections at 40x. As a freely available ImageJ plugin that requires no highly specialized equipment to utilize, AxonJ represents a powerful new community resource augmenting studies of the optic nerve using mice.

  1. Influences of olfactory ensheathing cells transplantation on axonal regeneration in spinal cord of adult rats

    Institute of Scientific and Technical Information of China (English)

    沈慧勇; 唐勇; 吴燕峰; 陈燕涛; 程志安

    2002-01-01

    To observe whether olfactory ensheathing cells could be used to promote axonal regeneration in a spontaneously nonregenerating system. Methods: After laminectomy at the lower thoracic level, the spinal cords of adult rats were exposed and completely transected at T10. A suspension of ensheathing cells was injected into the lesion site in 12 adult rats, and control D/F-12 (1∶1 mixture of DMEM and Hams F-12) was injected in 12 adult rats. Six weeks and ten weeks after cell transplantation, the rats were evaluated by climbing test and motor evoked potentials (MEPs) monitoring. The samples were procured and studied with histologicl and immunohistochemical methods. Results: At the 6th week after cell transplantation, all the rats in both the transplanted and control groups were paraplegic and the MEPs could not be recorded. At the 10th week after cell transplantation, of 7 rats in the control group, 2 rats had muscles contraction of the lower extremities, 2 rats had hips and/or knees active movement; and 5 rats MEPs could be recorded in the hind limbs in the transplanted group (n=7). None of the rats in the control group had functional improvement and no MEPs recorded (n=7). Numerous regenerating axons were observed through the transplantation and continued to regenerate into the denervated host tract. Cell labelling using anti-Myelin Basic Protein (MBP) and anti-Nerve Growth Factor Receptor (anti-NGFR) indicated that the regenerated axons were derived from the appropriate neuronal source and that donor cells migrated into the denervated host tract. But axonal degeneration existed and regenerating axons were not observed within the spinal cords of the adult rats with only D/F-12 injection. Conclusions: The axonal regeneration in the transected adult rat spinal cord is possible after ensheathing cells transplantation.

  2. Drosophila cortex and neuropile glia influence secondary axon tract growth, pathfinding, and fasciculation in the developing larval brain

    OpenAIRE

    Spindler, Shana R; Ortiz, Irma; Fung, Siaumin; Takashima, Shigeo; Hartenstein, Volker

    2009-01-01

    Glial cells play important roles in the developing brain during axon fasciculation, growth cone guidance, and neuron survival. In the Drosophila brain, three main classes of glia have been identified including surface, cortex, and neuropile glia. While surface glia ensheaths the brain and is involved in the formation of the blood-brain-barrier and the control of neuroblast proliferation, the range of functions for cortex and neuropile glia is less well understood. In this study, we use the ni...

  3. Outer Electrospun Polycaprolactone Shell Induces Massive Foreign Body Reaction and Impairs Axonal Regeneration through 3D Multichannel Chitosan Nerve Guides

    OpenAIRE

    Sven Duda; Lutz Dreyer; Peter Behrens; Soenke Wienecke; Tanmay Chakradeo; Birgit Glasmacher; Kirsten Haastert-Talini

    2014-01-01

    We report on the performance of composite nerve grafts with an inner 3D multichannel porous chitosan core and an outer electrospun polycaprolactone shell. The inner chitosan core provided multiple guidance channels for regrowing axons. To analyze the in vivo properties of the bare chitosan cores, we separately implanted them into an epineural sheath. The effects of both graft types on structural and functional regeneration across a 10 mm rat sciatic nerve gap were compared to autologous nerv...

  4. Nogo-A is involved in secondary axonal degeneration of thalamus in hypertensive rats with focal cortical infarction.

    Science.gov (United States)

    Wang, Fang; Liang, Zhijian; Hou, Qinghua; Xing, Shihui; Ling, Li; He, Meixia; Pei, Zhong; Zeng, Jinsheng

    2007-05-01

    We investigate whether Nogo-A is involved in the secondary axonal degeneration in the thalamus after distal middle cerebral artery occlusion (MCAO) in stroke-prone renovascular hypertensive rats (RHRSP). The expression of Nogo-A in ipsilateral ventroposterior nucleus (VPN) of the thalamus in RHRSP was observed at 1, 2 and 4 weeks after distal MCAO. In addition, intracerebroventricular infusion of NEP1-40, a Nogo-66 receptor (NgR) antagonist peptide, was administered starting 24 h after MCAO and continued for 1, 2 and 4 weeks, respectively. Axonal damage and regeneration were evaluated by analysis of the immunoreactivity (IR) of amyloid betaA4 precursor protein (APP), growth associated protein 43 (GAP-43) and microtubule associated protein 2 (MAP-2) in ipsilateral VPN of the thalamus at 1, 2 and 4 weeks after distal MCAO. Following ischemia, the expression of Nogo-A in oligodendrocytes increased persistently and its localization became redistributed around damaged axons and dendrites. Administration of NEP1-40 downregulated the expression of Nogo-A, reduced axonal injury and enhanced axonal regeneration. Our data suggest that Nogo-A is involved in secondary axonal degeneration and that inhibition of Nogo-A can reduce neuronal damage in the thalamus after distal MCAO.

  5. Morphometry of Axons in Optic Nerves of Siamese's Twins

    Institute of Scientific and Technical Information of China (English)

    Xinzu Gu; Zhenping Zhang; Qi Lin; Jiongji Liang; Wenyu Lu; Xiulan Ye; A A Sadun

    2002-01-01

    Purpose: To observe the development of optic nerve, we examined four optic nerves from Siameses Twins by absolute counts of axons.Methods: Mean axon diameter, mean axon density, totally axonal population and optic nerve area were noted for each optic nerve. The mean axon diameter and the mean axon density were compared between paraxial (inner sectors)and cortical (outer sectors)areas of the nerves.Results: More myelinated axons were seen in the inner sectors as compared to the outer sectors(average 11 axons/1 000 μm2 in inner sectors and 34 axons/l 000 μm2 in outer sectors( P=0. 036) . The myelinated fibers were also smaller(63 microns) in the outer sectors as compared to the inner sectors(72 microns) ( P = 0. 001 ). The average cross sectors area for the four 40 week stage optical nerves of Siamese Twins was 3.32 × 103 as compared to 1 million axons for 32-week-old normals.Conclusion: Our finding of fewer axonal number and small myelinated fibers in the Siamese Twins suggests hypoplasia. Myelination was more abnormal in the paraxial optic nerve than that in the peripheral sectors, suggesting anomalous development of optic nerve peripherally and delayed developnent centrally. Axonal density is higher in inner sectors than that in outer sectors, suggesting delayed development of the outer nerve sector.

  6. Patterns of growth, axonal extension and axonal arborization of neuronal lineages in the developing Drosophila brain

    OpenAIRE

    Larsen, Camilla; Shy, Diana; Spindler, Shana R; Fung, Siaumin; Pereanu, Wayne; Younossi -Hartenstein, Amelia; Hartenstein, Volker

    2009-01-01

    The Drosophila central brain is composed of approximately 100 paired lineages, with most lineages comprising 100–150 neurons. Most lineages have a number of important characteristics in common. Typically, neurons of a lineage stay together as a coherent cluster and project their axons into a coherent bundle visible from late embryo to adult. Neurons born during the embryonic period form the primary axon tracts (PATs) that follow stereotyped pathways in the neuropile. Apoptotic cell death remo...

  7. Uncoupling nicotine mediated motoneuron axonal pathfinding errors and muscle degeneration in zebrafish

    International Nuclear Information System (INIS)

    Zebrafish embryos offer a unique opportunity to investigate the mechanisms by which nicotine exposure impacts early vertebrate development. Embryos exposed to nicotine become functionally paralyzed by 42 hpf suggesting that the neuromuscular system is compromised in exposed embryos. We previously demonstrated that secondary spinal motoneurons in nicotine-exposed embryos were delayed in development and that their axons made pathfinding errors (Svoboda, K.R., Vijayaraghaven, S., Tanguay, R.L., 2002. Nicotinic receptors mediate changes in spinal motoneuron development and axonal pathfinding in embryonic zebrafish exposed to nicotine. J. Neurosci. 22, 10731-10741). In that study, we did not consider the potential role that altered skeletal muscle development caused by nicotine exposure could play in contributing to the errors in spinal motoneuron axon pathfinding. In this study, we show that an alteration in skeletal muscle development occurs in tandem with alterations in spinal motoneuron development upon exposure to nicotine. The alteration in the muscle involves the binding of nicotine to the muscle-specific AChRs. The nicotine-induced alteration in muscle development does not occur in the zebrafish mutant (sofa potato, [sop]), which lacks muscle-specific AChRs. Even though muscle development is unaffected by nicotine exposure in sop mutants, motoneuron axonal pathfinding errors still occur in these mutants, indicating a direct effect of nicotine exposure on nervous system development.

  8. Accelerated remyelination during inflammatory demyelination prevents axonal loss and improves functional recovery

    Science.gov (United States)

    Mei, Feng; Lehmann-Horn, Klaus; Shen, Yun-An A; Rankin, Kelsey A; Stebbins, Karin J; Lorrain, Daniel S; Pekarek, Kara; A Sagan, Sharon; Xiao, Lan; Teuscher, Cory; von Büdingen, H-Christian; Wess, Jürgen; Lawrence, J Josh; Green, Ari J; Fancy, Stephen PJ; Zamvil, Scott S; Chan, Jonah R

    2016-01-01

    Demyelination in MS disrupts nerve signals and contributes to axon degeneration. While remyelination promises to restore lost function, it remains unclear whether remyelination will prevent axonal loss. Inflammatory demyelination is accompanied by significant neuronal loss in the experimental autoimmune encephalomyelitis (EAE) mouse model and evidence for remyelination in this model is complicated by ongoing inflammation, degeneration and possible remyelination. Demonstrating the functional significance of remyelination necessitates selectively altering the timing of remyelination relative to inflammation and degeneration. We demonstrate accelerated remyelination after EAE induction by direct lineage analysis and hypothesize that newly formed myelin remains stable at the height of inflammation due in part to the absence of MOG expression in immature myelin. Oligodendroglial-specific genetic ablation of the M1 muscarinic receptor, a potent negative regulator of oligodendrocyte differentiation and myelination, results in accelerated remyelination, preventing axonal loss and improving functional recovery. Together our findings demonstrate that accelerated remyelination supports axonal integrity and neuronal function after inflammatory demyelination. DOI: http://dx.doi.org/10.7554/eLife.18246.001 PMID:27671734

  9. AxonQuant: A Microfluidic Chamber Culture-Coupled Algorithm That Allows High-Throughput Quantification of Axonal Damage

    Directory of Open Access Journals (Sweden)

    Yang Li

    2014-02-01

    Full Text Available Published methods for imaging and quantitatively analyzing morphological changes in neuronal axons have serious limitations because of their small sample sizes, and their time-consuming and nonobjective nature. Here we present an improved microfluidic chamber design suitable for fast and high-throughput imaging of neuronal axons. We developed the AxonQuant algorithm, which is suitable for automatic processing of axonal imaging data. This microfluidic chamber-coupled algorithm allows calculation of an ‘axonal continuity index' that quantitatively measures axonal health status in a manner independent of neuronal or axonal density. This method allows quantitative analysis of axonal morphology in an automatic and nonbiased manner. Our method will facilitate large-scale high-throughput screening for genes or therapeutic compounds for neurodegenerative diseases involving axonal damage. When combined with imaging technologies utilizing different gene markers, this method will provide new insights into the mechanistic basis for axon degeneration. Our microfluidic chamber culture-coupled AxonQuant algorithm will be widely useful for studying axonal biology and neurodegenerative disorders. © 2014 S. Karger AG, Basel

  10. Mislocalization of neuronal mitochondria reveals regulation of Wallerian degeneration and NMNAT/WLDS-mediated axon protection independent of axonal mitochondria

    OpenAIRE

    Kitay, Brandon M.; McCormack, Ryan; Wang, Yunfang; Tsoulfas, Pantelis; Zhai, R. Grace

    2013-01-01

    Axon degeneration is a common and often early feature of neurodegeneration that correlates with the clinical manifestations and progression of neurological disease. Nicotinamide mononucleotide adenylytransferase (NMNAT) is a neuroprotective factor that delays axon degeneration following injury and in models of neurodegenerative diseases suggesting a converging molecular pathway of axon self-destruction. The underlying mechanisms have been under intense investigation and recent reports suggest...

  11. The short coiled-coil domain-containing protein UNC-69 cooperates with UNC-76 to regulate axonal outgrowth and normal presynaptic organization in Caenorhabditis elegans

    Directory of Open Access Journals (Sweden)

    Tsung Nancy

    2006-05-01

    Full Text Available Abstract Background The nematode Caenorhabditis elegans has been used extensively to identify the genetic requirements for proper nervous system development and function. Key to this process is the direction of vesicles to the growing axons and dendrites, which is required for growth-cone extension and synapse formation in the developing neurons. The contribution and mechanism of membrane traffic in neuronal development are not fully understood, however. Results We show that the C. elegans gene unc-69 is required for axon outgrowth, guidance, fasciculation and normal presynaptic organization. We identify UNC-69 as an evolutionarily conserved 108-amino-acid protein with a short coiled-coil domain. UNC-69 interacts physically with UNC-76, mutations in which produce similar defects to loss of unc-69 function. In addition, a weak reduction-of-function allele, unc-69(ju69, preferentially causes mislocalization of the synaptic vesicle marker synaptobrevin. UNC-69 and UNC-76 colocalize as puncta in neuronal processes and cooperate to regulate axon extension and synapse formation. The chicken UNC-69 homolog is highly expressed in the developing central nervous system, and its inactivation by RNA interference leads to axon guidance defects. Conclusion We have identified a novel protein complex, composed of UNC-69 and UNC-76, which promotes axonal growth and normal presynaptic organization in C. elegans. As both proteins are conserved through evolution, we suggest that the mammalian homologs of UNC-69 and UNC-76 (SCOCO and FEZ, respectively may function similarly.

  12. Acute ethanol exposure inhibits silencing of cerebellar Golgi cell firing induced by granule cell axon input

    Directory of Open Access Journals (Sweden)

    Paolo eBotta

    2014-02-01

    Full Text Available Golgi cells (GoCs are specialized interneurons that provide inhibitory input to granule cells in the cerebellar cortex. GoCs are pacemaker neurons that spontaneously fire action potentials, triggering spontaneous inhibitory postsynaptic currents in granule cells and also contributing to the generation tonic GABAA receptor-mediated currents in granule cells. In turn, granule cell axons provide feedback glutamatergic input to GoCs. It has been shown that high frequency stimulation of granule cell axons induces a transient pause in GoC firing in a type 2-metabotropic glutamate receptor (mGluR2-dependent manner. Here, we investigated the effect ethanol on the pause of GoC firing induced by high frequency stimulation of granule cell axons. GoC electrophysiological recordings were performed in parasagittal cerebellar vermis slices from postnatal day 23 to 26 rats. Loose-patch cell-attached recordings revealed that ethanol (40 mM reversibly decreases the pause duration. An antagonist of mGluR2 reduced the pause duration but did not affect the effect of ethanol. Whole-cell voltage-clamp recordings showed that currents evoked by an mGluR2 agonist were not significantly affected by ethanol. Perforated-patch experiments in which hyperpolarizing and depolarizing currents were injected into GoCs demonstrated that there is an inverse relationship between spontaneous firing and pause duration. Slight inhibition of the Na+/K+ pump mimicked the effect of ethanol on pause duration. In conclusion, ethanol reduces the granule cell axon-mediated feedback mechanism by reducing the input responsiveness of GoCs. This would result in a transient increase of GABAA receptor-mediated inhibition of granule cells, limiting information flow at the input stage of the cerebellar cortex.

  13. Slit2 involvement in glioma cell migration is mediated by Robo1 receptor.

    Science.gov (United States)

    Mertsch, Sonja; Schmitz, Nicole; Jeibmann, Astrid; Geng, Jian-Guo; Paulus, Werner; Senner, Volker

    2008-03-01

    Slit and Robo proteins are evolutionarily conserved molecules whose interaction underlies axon guidance and neuronal precursor cell migration. During development secreted Slit proteins mediate chemorepulsive signals on cells expressing Robo receptors. Because similar molecular mechanisms may be utilized in glioma cell invasion and neuroblast migration, we studied the expression of Slit2 and its transmembrane receptor Robo1 as well as their functional role in migration in glioma cells. qRT-PCR and immunohistochemistry of human specimens revealed that Slit2 was distinctly expressed by non-neoplastic neurons, but at only very low levels in fibrillary astrocytoma and glioblastoma. Robo1 also was mainly restricted to neurons in the normal brain, whereas astrocytic tumor cells in situ as well as glioblastoma cell lines overexpressed Robo1 at mRNA and protein levels. Recombinant human Slit2 in a concentration of 0.45 nM was repulsive for glioma cell lines in a modified Boyden chamber assay. RNAi-mediated knockdown of Robo1 in glioma cell lines neutralized the repulsive effect of Slit2, demonstrating that Robo1 served as the major Slit2 receptor. Our findings suggest that a chemorepulsive effect mediated by interaction of Slit2 and Robo1 participates in glioma cell guidance in the brain.

  14. Dynamic Axonal Translation in Developing and Mature Visual Circuits.

    Science.gov (United States)

    Shigeoka, Toshiaki; Jung, Hosung; Jung, Jane; Turner-Bridger, Benita; Ohk, Jiyeon; Lin, Julie Qiaojin; Amieux, Paul S; Holt, Christine E

    2016-06-30

    Local mRNA translation mediates the adaptive responses of axons to extrinsic signals, but direct evidence that it occurs in mammalian CNS axons in vivo is scant. We developed an axon-TRAP-RiboTag approach in mouse that allows deep-sequencing analysis of ribosome-bound mRNAs in the retinal ganglion cell axons of the developing and adult retinotectal projection in vivo. The embryonic-to-postnatal axonal translatome comprises an evolving subset of enriched genes with axon-specific roles, suggesting distinct steps in axon wiring, such as elongation, pruning, and synaptogenesis. Adult axons, remarkably, have a complex translatome with strong links to axon survival, neurotransmission, and neurodegenerative disease. Translationally co-regulated mRNA subsets share common upstream regulators, and sequence elements generated by alternative splicing promote axonal mRNA translation. Our results indicate that intricate regulation of compartment-specific mRNA translation in mammalian CNS axons supports the formation and maintenance of neural circuits in vivo. PMID:27321671

  15. Motor and dorsal root ganglion axons serve as choice points for the ipsilateral turning of dI3 axons.

    Science.gov (United States)

    Avraham, Oshri; Hadas, Yoav; Vald, Lilach; Hong, Seulgi; Song, Mi-Ryoung; Klar, Avihu

    2010-11-17

    The axons of the spinal intersegmental interneurons are projected longitudinally along various funiculi arrayed along the dorsal-ventral axis of the spinal cord. The roof plate and the floor plate have a profound role in patterning their initial axonal trajectory. However, other positional cues may guide the final architecture of interneuron tracks in the spinal cord. To gain more insight into the organization of specific axonal tracks in the spinal cord, we focused on the trajectory pattern of a genetically defined neuronal population, dI3 neurons, in the chick spinal cord. Exploitation of newly characterized enhancer elements allowed specific labeling of dI3 neurons and axons. dI3 axons are projected ipsilaterally along two longitudinal fascicules at the ventral lateral funiculus (VLF) and the dorsal funiculus (DF). dI3 axons change their trajectory plane from the transverse to the longitudinal axis at two novel checkpoints. The axons that elongate at the DF turn at the dorsal root entry zone, along the axons of the dorsal root ganglion (DRG) neurons, and the axons that elongate at the VLF turn along the axons of motor neurons. Loss and gain of function of the Lim-HD protein Isl1 demonstrate that Isl1 is not required for dI3 cell fate. However, Isl1 is sufficient to impose ipsilateral turning along the motor axons when expressed ectopically in the commissural dI1 neurons. The axonal patterning of dI3 neurons, revealed in this study, highlights the role of established axonal cues-the DRG and motor axons-as intermediate guidepost cues for dI3 axons.

  16. Axon Membrane Skeleton Structure is Optimized for Coordinated Sodium Propagation

    CERN Document Server

    Zhang, Yihao; Li, He; Tzingounis, Anastasios V; Lykotrafitis, George

    2016-01-01

    Axons transmit action potentials with high fidelity and minimal jitter. This unique capability is likely the result of the spatiotemporal arrangement of sodium channels along the axon. Super-resolution microscopy recently revealed that the axon membrane skeleton is structured as a series of actin rings connected by spectrin filaments that are held under entropic tension. Sodium channels also exhibit a periodic distribution pattern, as they bind to ankyrin G, which associates with spectrin. Here, we elucidate the relationship between the axon membrane skeleton structure and the function of the axon. By combining cytoskeletal dynamics and continuum diffusion modeling, we show that spectrin filaments under tension minimize the thermal fluctuations of sodium channels and prevent overlap of neighboring channel trajectories. Importantly, this axon skeletal arrangement allows for a highly reproducible band-like activation of sodium channels leading to coordinated sodium propagation along the axon.

  17. The influence of electrospun fibre size on Schwann cell behaviour and axonal outgrowth

    Energy Technology Data Exchange (ETDEWEB)

    Gnavi, S., E-mail: sara.gnavi@unito.it [Department of Clinical and Biological Sciences, University of Torino, Orbassano 10043 (Italy); Neuroscience Institute of the Cavalieri-Ottolenghi Foundation, University of Torino, Orbassano 10043 (Italy); Fornasari, B.E., E-mail: benedettaelena.fornasari@unito.it [Department of Clinical and Biological Sciences, University of Torino, Orbassano 10043 (Italy); Neuroscience Institute of the Cavalieri-Ottolenghi Foundation, University of Torino, Orbassano 10043 (Italy); Tonda-Turo, C., E-mail: chiara.tondaturo@polito.it [Politecnico di Torino, Department of Mechanical and Aerospace Engineering, Politecnico of Torino, Torino 10100 (Italy); Ciardelli, G., E-mail: gianluca.ciardelli@polito.it [Politecnico di Torino, Department of Mechanical and Aerospace Engineering, Politecnico of Torino, Torino 10100 (Italy); CNR-IPCF UOS, Pisa 56124 (Italy); Zanetti, M., E-mail: marco.zanetti@unito.it [Nanostructured Interfaces and Surfaces, Department of Chemistry, University of Torino, Torino 10100 (Italy); Geuna, S., E-mail: stefano.geuna@unito.it [Department of Clinical and Biological Sciences, University of Torino, Orbassano 10043 (Italy); Neuroscience Institute of the Cavalieri-Ottolenghi Foundation, University of Torino, Orbassano 10043 (Italy); Perroteau, I., E-mail: isabelle.perroteau@unito.it [Department of Clinical and Biological Sciences, University of Torino, Orbassano 10043 (Italy)

    2015-03-01

    Fibrous substrates functioning as temporary extracellular matrices can be prepared easily by electrospinning, yielding fibrous matrices suitable as internal fillers for nerve guidance channels. In this study, gelatin micro- or nano-fibres were prepared by electrospinning by tuning the gelatin concentration and solution flow rate. The effect of gelatin fibre diameter on cell adhesion and proliferation was tested in vitro using explant cultures of Schwann cells (SC) and dorsal root ganglia (DRG). Cell adhesion was assessed by quantifying the cell spreading area, actin cytoskeleton organization and focal adhesion complex formation. Nano-fibres promoted cell spreading and actin cytoskeleton organization, increasing cellular adhesion and the proliferation rate. However, both migration rate and motility, quantified by transwell and time lapse assays respectively, were greater in cells cultured on micro-fibres. Finally, there was more DRG axon outgrowth on micro-fibres. These data suggest that the topography of electrospun gelatin fibres can be adjusted to modulate SC and axon organization and that both nano- and micro-fibres are promising fillers for the design of devices for peripheral nerve repair. - Highlights: • Electrospinning used to produce gelatin nano- and micro-fibre matrices. • Nano-fibre matrices promote Schwann cell organization and increase proliferation rate. • Micro-fibre matrices promote Schwann cell migration. • Micro-fibre matrices promote axonal outgrowth.

  18. The influence of electrospun fibre size on Schwann cell behaviour and axonal outgrowth

    International Nuclear Information System (INIS)

    Fibrous substrates functioning as temporary extracellular matrices can be prepared easily by electrospinning, yielding fibrous matrices suitable as internal fillers for nerve guidance channels. In this study, gelatin micro- or nano-fibres were prepared by electrospinning by tuning the gelatin concentration and solution flow rate. The effect of gelatin fibre diameter on cell adhesion and proliferation was tested in vitro using explant cultures of Schwann cells (SC) and dorsal root ganglia (DRG). Cell adhesion was assessed by quantifying the cell spreading area, actin cytoskeleton organization and focal adhesion complex formation. Nano-fibres promoted cell spreading and actin cytoskeleton organization, increasing cellular adhesion and the proliferation rate. However, both migration rate and motility, quantified by transwell and time lapse assays respectively, were greater in cells cultured on micro-fibres. Finally, there was more DRG axon outgrowth on micro-fibres. These data suggest that the topography of electrospun gelatin fibres can be adjusted to modulate SC and axon organization and that both nano- and micro-fibres are promising fillers for the design of devices for peripheral nerve repair. - Highlights: • Electrospinning used to produce gelatin nano- and micro-fibre matrices. • Nano-fibre matrices promote Schwann cell organization and increase proliferation rate. • Micro-fibre matrices promote Schwann cell migration. • Micro-fibre matrices promote axonal outgrowth

  19. Axons of sacral preganglionic neurons in the cat: II. Axon collaterals.

    Science.gov (United States)

    Morgan, C W

    2001-01-01

    Axon collaterals were identified in 21 of 24 preganglionic neurons in the lateral band of the sacral parasympathetic nucleus of the cat. Following the intracellular injection of HRP or neurobiotin the axons from 20 of these neurons were followed and 53 primary axon collaterals were found to originate from unmyelinated segments and from nodes of Ranvier. Detailed mapping done in the five best labeled cells showed bilateral axon collaterals distributions up to 25,000 microm in length with 950 varicosities and unilateral distributions up to 12,561 microm with 491 varicosities. The axon collaterals appeared to be unmyelinated, which was confirmed at EM, and were small in diameter (average 0.3 microm). Varicosities were located mostly in laminae I, V, VII, VIII and X and in the lateral funiculi. Most varicosities were not in contact with visible structures but some were seen in close apposition to Nissl stained somata and proximal dendrites. Varicosities had average minor diameters of 1.3 microm and major diameters of 2.3 microm. Most were boutons en passant while 10-20% were boutons termineaux. EM revealed axodendritic and axoaxonic synapses formed by varicosities and by the axons between varicosities. It is estimated that the most extensive of these axon collaterals systems may contact over 200 spinal neurons in multiple locations. These data lead to the conclusion that sacral preganglionic neurons have multiple functions within the spinal cord in addition to serving their target organ. As most preganglionic neurons in this location innervate the urinary bladder, it is possible that bladder preganglionic neurons have multiple functions.

  20. Corporate information management guidance

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1997-08-01

    At the request of the Department of Energy`s (DOE) Information Management (IM) Council, IM representatives from nearly all Headquarters (HQ) organizations have been meeting over the past year as the Corporate Guidance Group (CGG) to develop useful and sound corporate information management (IM) guidance. The ability of the Department`s IM community to develop such unified guidance continues to be critical to the success of future Departmental IM planning processes and the establishment of a well-coordinated IM environment between Headquarters and field organizations. This report, with 26 specific corporate IM guidance items documented and unanimously agreed to, as well as 12 items recommended for further development and 3 items deferred for future consideration, represents a highly successful effort by the IM community. The effort has proven that the diverse DOE organizations can put aside individual preferences and work together towards a common and mutually beneficial goal. In examining most areas and issues associated with information management in the Department, they have developed specific, far-reaching, and useful guidance. The IM representatives recommend that the documented guidance items provided in this report and approved by the DOE IM Council be followed by all IM organizations. The representatives also strongly recommend that the guidance process developed by the CGG be the single process for developing corporate IM guidance.

  1. Drosophila cortex and neuropile glia influence secondary axon tract growth, pathfinding, and fasciculation in the developing larval brain.

    Science.gov (United States)

    Spindler, Shana R; Ortiz, Irma; Fung, Siaumin; Takashima, Shigeo; Hartenstein, Volker

    2009-10-15

    Glial cells play important roles in the developing brain during axon fasciculation, growth cone guidance, and neuron survival. In the Drosophila brain, three main classes of glia have been identified including surface, cortex, and neuropile glia. While surface glia ensheaths the brain and is involved in the formation of the blood-brain-barrier and the control of neuroblast proliferation, the range of functions for cortex and neuropile glia is less well understood. In this study, we use the nirvana2-GAL4 driver to visualize the association of cortex and neuropile glia with axon tracts formed by different brain lineages and selectively eliminate these glial populations via induced apoptosis. The larval central brain consists of approximately 100 lineages. Each lineage forms a cohesive axon bundle, the secondary axon tract (SAT). While entering and traversing the brain neuropile, SATs interact in a characteristic way with glial cells. Some SATs are completely invested with glial processes; others show no particular association with glia, and most fall somewhere in between these extremes. Our results demonstrate that the elimination of glia results in abnormalities in SAT fasciculation and trajectory. The most prevalent phenotype is truncation or misguidance of axon tracts, or abnormal fasciculation of tracts that normally form separate pathways. Importantly, the degree of glial association with a given lineage is positively correlated with the severity of the phenotype resulting from glial ablation. Previous studies have focused on the embryonic nerve cord or adult-specific compartments to establish the role of glia. Our study provides, for the first time, an analysis of glial function in the brain during axon formation and growth in larval development. PMID:19646433

  2. Increased Cx32 expression in spinal cord TrkB oligodendrocytes following peripheral axon injury.

    Science.gov (United States)

    Coulibaly, Aminata P; Isaacson, Lori G

    2016-08-01

    Following injury to motor axons in the periphery, retrograde influences from the injury site lead to glial cell plasticity in the vicinity of the injured neurons. Following the transection of peripherally located preganglionic axons of the cervical sympathetic trunk (CST), a population of oligodendrocyte (OL) lineage cells expressing full length TrkB, the cognate receptor for brain derived neurotrophic factor (BDNF), is significantly increased in number in the spinal cord. Such robust plasticity in OL lineage cells in the spinal cord following peripheral axon transection led to the hypothesis that the gap junction communication protein connexin 32 (Cx32), which is specific to OL lineage cells, was influenced by the injury. Following CST transection, Cx32 expression in the spinal cord intermediolateral cell column (IML), the location of the parent cell bodies, was significantly increased. The increased Cx32 expression was localized specifically to TrkB OLs in the IML, rather than other cell types in the OL cell lineage, with the population of Cx32/TrkB cells increased by 59%. Cx32 expression in association with OPCs was significantly decreased at one week following the injury. The results of this study provide evidence that peripheral axon injury can differentially affect the gap junction protein expression in OL lineage cells in the adult rat spinal cord. We conclude that the retrograde influences originating from the peripheral injury site elicit dramatic changes in the CNS expression of Cx32, which in turn may mediate the plasticity of OL lineage cells observed in the spinal cord following peripheral axon injury. PMID:27246301

  3. Expression of a retinoic acid receptor (RAR)-like protein in the embryonic and adult nervous system of a protostome species.

    Science.gov (United States)

    Carter, Christopher J; Rand, Christopher; Mohammad, Imtiaz; Lepp, Amanda; Vesprini, Nicholas; Wiebe, Olivia; Carlone, Robert; Spencer, Gaynor E

    2015-01-01

    The vitamin A metabolite, retinoic acid, is an important molecule in nervous system development and regeneration in vertebrates. Retinoic acid signaling in vertebrates is mediated by two classes of nuclear receptors, the retinoid X receptors (RXRs) and the retinoic acid receptors (RARs). Recently, evidence has emerged to suggest that many effects of retinoic acid are conserved between vertebrate and invertebrate nervous systems, even though the RARs were previously thought to be a vertebrate innovation and to not exist in non-chordates. We have cloned a full-length putative RAR from the CNS of the mollusc Lymnaea stagnalis (LymRAR). Immunoreactivity for the RAR protein was found in axons of adult neurons in the central nervous system and in growth cones of regenerating neurons in vitro. A vertebrate RAR antagonist blocked growth cone turning induced by exogenous all-trans retinoic acid, possibly suggesting a role for this receptor in axon guidance. We also provide immunostaining evidence for the presence of RAR protein in the developing, embryonic CNS, where it is also found in axonal processes. Using qPCR, we determined that LymRAR mRNA is detectable in the early veliger stage embryo and that mRNA levels increase significantly during embryonic development. Putative disruption of retinoid signaling in Lymnaea embryos using vertebrate RAR antagonists resulted in abnormal eye and shell development and in some instances completely halted development, resembling the effects of all-trans retinoic acid. This study provides evidence for RAR functioning in a protostome species. PMID:25504929

  4. Axonal loss and neuroprotection in optic neuropathies.

    Science.gov (United States)

    Levin, Leonard A

    2007-06-01

    Most optic neuropathies do not have effective treatments. Examples are ischemic optic neuropathy, Leber hereditary optic neuropathy, optic neuritis, and traumatic optic neuropathy. In some cases, the pathophysiology of the optic nerve injury is not fully understood. For example, while the demyelinative aspects of optic neuritis have been studied, the mechanism by which the axonal loss occurs is less apparent. In other cases, although the pathophysiology of the optic neuropathy may be understood, there is difficulty treating the disease, for example, with traumatic optic neuropathy. In response to this therapeutic dearth, the concept of neuroprotection has arisen. Neuroprotection is a therapeutic paradigm for preventing death of neurons from injury and maintaining function. In optic neuropathies, the corresponding neuron is the retinal ganglion cell. These cells are unable to divide, and optic neuropathies irrevocably result in their death; therefore, the primary target of neuroprotection are retinal ganglion cells and their axons. This review emphasizes that most optic neuropathies are axonal and thus good targets for neuroprotection. PMID:17508035

  5. Synaptic Democracy and Vesicular Transport in Axons

    Science.gov (United States)

    Bressloff, Paul C.; Levien, Ethan

    2015-04-01

    Synaptic democracy concerns the general problem of how regions of an axon or dendrite far from the cell body (soma) of a neuron can play an effective role in neuronal function. For example, stimulated synapses far from the soma are unlikely to influence the firing of a neuron unless some sort of active dendritic processing occurs. Analogously, the motor-driven transport of newly synthesized proteins from the soma to presynaptic targets along the axon tends to favor the delivery of resources to proximal synapses. Both of these phenomena reflect fundamental limitations of transport processes based on a localized source. In this Letter, we show that a more democratic distribution of proteins along an axon can be achieved by making the transport process less efficient. This involves two components: bidirectional or "stop-and-go" motor transport (which can be modeled in terms of advection-diffusion), and reversible interactions between motor-cargo complexes and synaptic targets. Both of these features have recently been observed experimentally. Our model suggests that, just as in human societies, there needs to be a balance between "efficiency" and "equality".

  6. MRI of the diffuse axonal injury

    Energy Technology Data Exchange (ETDEWEB)

    Joo, Yang Gu; Woo, Young Hoon; Suh, Soo Jhi [Keimyung University School of Medicine, Daegu (Korea, Republic of)

    1992-01-15

    CT has facilitated early recognition and treatment of focal brain injuries in patients with head trauma. However, CT shows relatively low sensitivity in identifying non hemorrhage contusion and injuries of white matter. MR is known to be superior to CT in detection of white matter injuries, such as diffuse axonal injury. MR imaging in 14 cases of diffuse axonal injury on 2.0T was studied. The corpus callosum, especially the body portion, was the most commonly involved site. The lesions ranged from 5 to 20mm in size with ovoid to elliptical shape. T2WI was the most sensitive pulse sequence in detecting lesions such as white matter degeneration, hemorrhagic and non hemorrhagic contusion. The lesions were nonspecific as high and low signal intensities on T2WI and T1WI respectively. CT showed white matter abnormality in only 1 case of 14 cases. We propose MR imaging as the primary imaging procedure for the detection of diffuse axonal injury because of its multiplanar capabilities and higher sensitivity.

  7. Semaphorin 3C Released from a Biocompatible Hydrogel Guides and Promotes Axonal Growth of Rodent and Human Dopaminergic Neurons.

    Science.gov (United States)

    Carballo-Molina, Oscar A; Sánchez-Navarro, Andrea; López-Ornelas, Adolfo; Lara-Rodarte, Rolando; Salazar, Patricia; Campos-Romo, Aurelio; Ramos-Mejía, Verónica; Velasco, Iván

    2016-06-01

    Cell therapy in experimental models of Parkinson's disease replaces the lost dopamine neurons (DAN), but we still need improved methods to guide dopaminergic axons (DAx) of grafted neurons to make proper connections. The protein Semaphorin 3C (Sema3C) attracts DAN axons and enhances their growth. In this work, we show that the hydrogel PuraMatrix, a self-assembling peptide-based matrix, incorporates Sema3C and releases it steadily during 4 weeks. We also tested if hydrogel-delivered Sema3C attracts DAx using a system of rat midbrain explants embedded in collagen gels. We show that Sema3C released by this hydrogel attracts DAx, in a similar way to pretectum, which is known to attract growing DAN axons. We assessed the effect of Sema3C on the growth of DAx using microfluidic devices. DAN from rat midbrain or those differentiated from human embryonic stem cells showed enhanced axonal extension when exposed to hydrogel-released Sema3C, similar to soluble Sema3C. Notably, DAN of human origin express the cognate Sema3C receptors, Neuropilin1 and Neuropilin2. These results show that PuraMatrix is able to incorporate and release Sema3C, and such delivery guides and promotes the axonal growth of DAN. This biocompatible hydrogel might be useful as a Sema3C carrier for in vivo studies in parkinsonian animal models. PMID:27174503

  8. Focal axonal swellings and associated ultrastructural changes attenuate conduction velocity in central nervous system axons: a computer modeling study.

    Science.gov (United States)

    Kolaric, Katarina V; Thomson, Gemma; Edgar, Julia M; Brown, Angus M

    2013-08-01

    The constancy of action potential conduction in the central nervous system (CNS) relies on uniform axon diameter coupled with fidelity of the overlying myelin providing high-resistance, low capacitance insulation. Whereas the effects of demyelination on conduction have been extensively studied/modeled, equivalent studies on the repercussions for conduction of axon swelling, a common early pathological feature of (potentially reversible) axonal injury, are lacking. The recent description of experimentally acquired morphological and electrical properties of small CNS axons and oligodendrocytes prompted us to incorporate these data into a computer model, with the aim of simulating the effects of focal axon swelling on action potential conduction. A single swelling on an otherwise intact axon, as occurs in optic nerve axons of Cnp1 null mice caused a small decrease in conduction velocity. The presence of single swellings on multiple contiguous internodal regions (INR), as likely occurs in advanced disease, caused qualitatively similar results, except the dimensions of the swellings required to produce equivalent attenuation of conduction were significantly decreased. Our simulations of the consequences of metabolic insult to axons, namely, the appearance of multiple swollen regions, accompanied by perturbation of overlying myelin and increased axolemmal permeability, contained within a single INR, revealed that conduction block occurred when the dimensions of the simulated swellings were within the limits of those measured experimentally, suggesting that multiple swellings on a single axon could contribute to axonal dysfunction, and that increased axolemmal permeability is the decisive factor that promotes conduction block. PMID:24303138

  9. Early ultrastructural defects of axons and axon-glia junctions in mice lacking expression of Cnp1.

    Science.gov (United States)

    Edgar, Julia M; McLaughlin, Mark; Werner, Hauke B; McCulloch, Mailis C; Barrie, Jennifer A; Brown, Angus; Faichney, Andrew Blyth; Snaidero, Nicolas; Nave, Klaus-Armin; Griffiths, Ian R

    2009-12-01

    Most axons in the central nervous system (CNS) are surrounded by a multilayered myelin sheath that promotes fast, saltatory conduction of electrical impulses. By insulating the axon, myelin also shields the axoplasm from the extracellular milieu. In the CNS, oligodendrocytes provide support for the long-term maintenance of myelinated axons, independent of the myelin sheath. Here, we use electron microscopy and morphometric analyses to examine the evolution of axonal and oligodendroglial changes in mice deficient in 2',3'-cyclic nucleotide 3'-phosphodiesterase (CNP) and in mice deficient in both CNP and proteolipid protein (PLP/DM20). We show that CNP is necessary for the formation of a normal inner tongue process of oligodendrocytes that myelinate small diameter axons. We also show that axonal degeneration in Cnp1 null mice is present very early in postnatal life. Importantly, compact myelin formed by transplanted Cnp1 null oligodendrocytes induces the same degenerative changes in shiverer axons that normally are dysmyelinated but structurally intact. Mice deficient in both CNP and PLP develop a more severe axonal phenotype than either single mutant, indicating that the two oligodendroglial proteins serve distinct functions in supporting the myelinated axon. These observations support a model in which the trophic functions of oligodendrocytes serve to offset the physical shielding of axons by myelin membranes. PMID:19459211

  10. Ameliorative Effects of p75NTR-ED-Fc on Axonal Regeneration and Functional Recovery in Spinal Cord-Injured Rats.

    Science.gov (United States)

    Wang, Yong-Tang; Lu, Xiu-Min; Zhu, Feng; Huang, Peng; Yu, Ying; Long, Zai-Yun; Wu, Ya-Min

    2015-12-01

    As a co-receptor of Nogo-66 receptor (NgR) and a critical receptor for paired immunoglobulin-like receptor (PirB), p75 neurotrophin receptor (p75NTR) mediates the inhibitory effects of myelin-associated inhibitors on axonal regeneration after spinal cord injury. Therefore, the p75NTR antagonist, such as recombinant p75NTR protein or its homogenates may block the inhibitory effects of myelin and promote the axonal regeneration and functional recovery. The purposes of this study are to subclone and express the extracellular domain gene of human p75NTR with IgG-Fc (hp75NTR-ED-Fc) in prokaryotic expression system and investigate the effects of the recombinant protein on axonal regeneration and functional recovery in spinal cord-injured rats. The hp75NTR-ED-Fc coding sequence was amplified from pcDNA-hp75NTR-ED-Fc by polymerase chain reaction (PCR) and subcloned into vector pET32a (+), then the effects of the purified recombinant protein on neurite outgrowth of dorsal root ganglion (DRG) neurons cultured with myelin-associated glycoprotein (MAG) were determined, and the effects of the fusion protein on axonal regeneration, functional recovery, and its possible mechanisms in spinal cord-injured rats were further investigated. The results indicated that the purified infusion protein could promote neurite outgrowth of DRG neurons, promote axonal regeneration and functional recovery, and decrease RhoA activation in spinal cord-injured rats. Taken together, the findings revealed that p75NTR still may be a potential and novel target for therapeutic intervention for spinal cord injury and that the hp75NTR-ED-Fc fusion protein treatment enhances functional recovery by limiting tissue loss and stimulating axonal growth in spinal cord-injured rats, which may result from decreasing the activation of RhoA.

  11. Dynamics of axon fasciculation in the presence of neuronal turnover

    CERN Document Server

    Chaudhuri, Debasish; Mohanty, P K; Zapotocky, Martin

    2008-01-01

    We formulate and characterize a model aiming to describe the formation of fascicles of axons mediated by contact axon-axon interactions. The growing axons are represented as interacting directed random walks in two spatial dimensions. To mimic axonal turnover in the mammalian olfactory system, the random walkers are injected and removed at specified rates. In the dynamical steady state, the position-dependent distribution of fascicle sizes obeys a scaling law. We identify several distinct time scales that emerge from the dynamics, are sensitive functions of the microscopic parameters of the model, and can exceed the average axonal lifetime by orders of magnitude. We discuss our findings in terms of an analytically tractable, effective model of fascicle dynamics.

  12. Laser Guidance Analysis Facility

    Data.gov (United States)

    Federal Laboratory Consortium — This facility, which provides for real time, closed loop evaluation of semi-active laser guidance hardware, has and continues to be instrumental in the development...

  13. Action potentials reliably invade axonal arbors of rat neocortical neurons

    OpenAIRE

    Cox, Charles L.; Denk, Winfried; Tank, David W.; Svoboda, Karel

    2000-01-01

    Neocortical pyramidal neurons have extensive axonal arborizations that make thousands of synapses. Action potentials can invade these arbors and cause calcium influx that is required for neurotransmitter release and excitation of postsynaptic targets. Thus, the regulation of action potential invasion in axonal branches might shape the spread of excitation in cortical neural networks. To measure the reliability and extent of action potential invasion into axonal arbors, we have used two-photon...

  14. Myelin sheath survival after guanethidine-induced axonal degeneration

    OpenAIRE

    1992-01-01

    Membrane-membrane interactions between axons and Schwann cells are required for initial myelin formation in the peripheral nervous system. However, recent studies of double myelination in sympathetic nerve have indicated that myelin sheaths continue to exist after complete loss of axonal contact (Kidd, G. J., and J. W. Heath. 1988. J. Neurocytol. 17:245-261). This suggests that myelin maintenance may be regulated either by diffusible axonal factors or by nonaxonal mechanisms. To test these hy...

  15. Axon Regeneration in the Peripheral and Central Nervous Systems

    OpenAIRE

    Huebner, Eric A.; Strittmatter, Stephen M

    2009-01-01

    Axon regeneration in the mature mammalian central nervous system (CNS) is extremely limited after injury. Consequently, functional deficits persist after spinal cord injury (SCI), traumatic brain injury, stroke, and related conditions that involve axonal disconnection. This situation differs from that in the mammalian peripheral nervous system (PNS), where long- distance axon regeneration and substantial functional recovery can occur in the adult. Both extracellular molecules and the intrinsi...

  16. Axonal autophagy during regeneration of the rat sciatic nerve

    Institute of Scientific and Technical Information of China (English)

    Kangrong Lu; Zhongxian Piao; Zhenxi Liu; Weiwang Gu; Wanshan Wang; Nngjie Piao

    2008-01-01

    BACKGROUND: The removal of degenerated axonal debris during Wallerian degeneration is very important for nerve regeneration. However, the mechanism by which debris is removed is not been completely understood. Considerable controversy remains as to the clearance pathway and cells that are involved. OBJECTIVE: To investigate axonal autophagy during removal of degenerated axonal debris by transecting the sciatic nerve in a rat Wallerian degeneration model.DESIGN, TIME AND SETTING: Experimental neuropathological analysis. The experiment was conducted at the Laboratory Animal Service Center of the Southern Medical University between January and June 2005. MATERIALS: Fifty-four adult, Wistar rats of either sex, weighing 180-250 g, were obtained from the Laboratory Animal Service Center of the Southern Medical University. Animals were randomly divided into nine groups of six rats. METHODS: Wallerian degeneration was induced by transecting the rat sciatic nerve, and tissue samples from the distal stump were obtained 0.2, 0.4, 1, 2, 3, 4, 7, 10, and 15 days post-transection. Ultrathin sections were prepared for electron microscopy to study ultrastructure and enzyme cytochemistry staining. MAIN OUTCOME MEASURES: Ultrastructure (axon body, autophagic body, and cystoskeleton) of axons and myelin sheaths observed with electron microscopy; acidic phosphatase activity detected by Gomori staining using electron microscopy. RESULTS: The major changes of degenerating axons after transection were axoplasm swelling and separation of axons from their myelin sheath between five hours and two days post-transection. At four days post-transection, the axoplasm condensed and axons were completely separated from the myelin sheath, forming dissociative axon bodies. Vacuoles of different sizes formed in axons during the early phase after lesion. Larger dissociative axon bodies were formed when the axons were completely separated from the myelin sheath during a late phase. The axolemma

  17. Differences in excitability properties of FDI and ADM motor axons.

    Science.gov (United States)

    Bae, Jong Seok; Sawai, Setsu; Misawa, Sonoko; Kanai, Kazuaki; Isose, Sagiri; Kuwabara, Satoshi

    2009-03-01

    The first dorsal interosseous (FDI) and abductor digiti minimi (ADM) muscles are innervated by the same ulnar nerve, but studies have shown that the former is much more severely affected in amyotrophic lateral sclerosis. In this study, threshold tracking was used to investigate whether membrane properties differ between FDI and ADM motor axons. In 12 normal subjects, compound muscle action potentials were recorded from FDI and ADM after ulnar nerve stimulation at the wrist. The strength-duration time constant was significantly longer in the FDI axons than in the ADM axons, and latent addition studies showed greater threshold changes at the conditioning-test stimulus of 0.2 ms in FDI than in ADM axons. These findings suggest that nodal persistent sodium conductances are more prominent in FDI axons than in ADM axons, and therefore excitability is physiologically higher in FDI axons. Even in the same nerve at the same sites, membrane properties of FDI and ADM motor axons differ significantly, and thus their axonal/neuronal responses to disease may also differ.

  18. Present status of studies on diffuse axonal injury

    Institute of Scientific and Technical Information of China (English)

    Jie Ma; Chonggong Zhang; Yi Li

    2006-01-01

    OBJECTIVE: To explain the present status of study on diffuse axonal injury,investigate its pathogenesis and pathophysiological changes ,and suggest principles for the diagnosis and treatment.DATA SOURCES: Articles about diffuse axonal injury published in English from January 1994 to October 2006 were searched in Pubmed database using the keywords of "diffuse axonal injury,pathogenesis,therapy".STUDY SELECTION: The collected articles were primarily screened to select those associated with diffuse axonal injury,the obviously irrelated articles were excluded,and the rest ones were retrieved manually,and the full-texes were searched.DATA EXTRACTION: Totally 98 articles were collected,41 of them were involved.and the other 57 were excluded.DATA SYNTHESIS: Diffuse axonal injury is mainly caused by acceleratory or deceleratory injury,and its pathophysiological change is a progressive duration,local axonal injury finally develops to axonal breakage,mainly includes inactivation of natrium channel,intracellular Ca2+ overloading,activation of calcium protease,caspase etc.,and mitochondrial injury.At present,there is still lack of effective therapeutic methods for diffuse axonal injury,so we should actively explore more effective methods to relieve the pain of patients and improve their prognosis.CONCLUSION: At present,diffuse axonal injury has not attracted enough attentions in China,the mechanisms for its diagnosis and attack are still unclear,and the treatments are mainly aiming at the symptoms.

  19. Patterns of growth, axonal extension and axonal arborization of neuronal lineages in the developing Drosophila brain.

    Science.gov (United States)

    Larsen, Camilla; Shy, Diana; Spindler, Shana R; Fung, Siaumin; Pereanu, Wayne; Younossi-Hartenstein, Amelia; Hartenstein, Volker

    2009-11-15

    The Drosophila central brain is composed of approximately 100 paired lineages, with most lineages comprising 100-150 neurons. Most lineages have a number of important characteristics in common. Typically, neurons of a lineage stay together as a coherent cluster and project their axons into a coherent bundle visible from late embryo to adult. Neurons born during the embryonic period form the primary axon tracts (PATs) that follow stereotyped pathways in the neuropile. Apoptotic cell death removes an average of 30-40% of primary neurons around the time of hatching. Secondary neurons generated during the larval period form secondary axon tracts (SATs) that typically fasciculate with their corresponding primary axon tract. SATs develop into the long fascicles that interconnect the different compartments of the adult brain. Structurally, we distinguish between three types of lineages: PD lineages, characterized by distinct, spatially separate proximal and distal arborizations; C lineages with arborizations distributed continuously along the entire length of their tract; D lineages that lack proximal arborizations. Arborizations of many lineages, in particular those of the PD type, are restricted to distinct neuropile compartments. We propose that compartments are "scaffolded" by individual lineages, or small groups thereof. Thereby, the relatively small number of primary neurons of each primary lineage set up the compartment map in the late embryo. Compartments grow during the larval period simply by an increase in arbor volume of primary neurons. Arbors of secondary neurons form within or adjacent to the larval compartments, resulting in smaller compartment subdivisions and additional, adult specific compartments. PMID:19538956

  20. Focal axonal swellings and associated ultrastructural changes attenuate conduction velocity in central nervous system axons: a computer modeling study

    OpenAIRE

    Kolaric, Katarina V; Thomson, Gemma; Edgar, Julia M; Brown, Angus M.

    2013-01-01

    The constancy of action potential conduction in the central nervous system (CNS) relies on uniform axon diameter coupled with fidelity of the overlying myelin providing high-resistance, low capacitance insulation. Whereas the effects of demyelination on conduction have been extensively studied/modeled, equivalent studies on the repercussions for conduction of axon swelling, a common early pathological feature of (potentially reversible) axonal injury, are lacking. The recent description of ex...

  1. β-Arrestin-Dependent Dopaminergic Regulation of Calcium Channel Activity in the Axon Initial Segment.

    Science.gov (United States)

    Yang, Sungchil; Ben-Shalom, Roy; Ahn, Misol; Liptak, Alayna T; van Rijn, Richard M; Whistler, Jennifer L; Bender, Kevin J

    2016-08-01

    G-protein-coupled receptors (GPCRs) initiate a variety of signaling cascades, depending on effector coupling. β-arrestins, which were initially characterized by their ability to "arrest" GPCR signaling by uncoupling receptor and G protein, have recently emerged as important signaling effectors for GPCRs. β-arrestins engage signaling pathways that are distinct from those mediated by G protein. As such, arrestin-dependent signaling can play a unique role in regulating cell function, but whether neuromodulatory GPCRs utilize β-arrestin-dependent signaling to regulate neuronal excitability remains unclear. Here, we find that D3 dopamine receptors (D3R) regulate axon initial segment (AIS) excitability through β-arrestin-dependent signaling, modifying CaV3 voltage dependence to suppress high-frequency action potential generation. This non-canonical D3R signaling thereby gates AIS excitability via pathways distinct from classical GPCR signaling pathways.

  2. My view on occupation guidance

    Institute of Scientific and Technical Information of China (English)

    2012-01-01

    Occupation instruction needs to the support of theories,in the case of the occupation guidance theory is not very developed in our country,It has very important sense that absorbing and drawing lessons from the advanced occupation guidance theory,and targeting guidance to occupation guidance work,.

  3. Rabies Virus Hijacks and accelerates the p75NTR retrograde axonal transport machinery.

    Science.gov (United States)

    Gluska, Shani; Zahavi, Eitan Erez; Chein, Michael; Gradus, Tal; Bauer, Anja; Finke, Stefan; Perlson, Eran

    2014-08-01

    Rabies virus (RABV) is a neurotropic virus that depends on long distance axonal transport in order to reach the central nervous system (CNS). The strategy RABV uses to hijack the cellular transport machinery is still not clear. It is thought that RABV interacts with membrane receptors in order to internalize and exploit the endosomal trafficking pathway, yet this has never been demonstrated directly. The p75 Nerve Growth Factor (NGF) receptor (p75NTR) binds RABV Glycoprotein (RABV-G) with high affinity. However, as p75NTR is not essential for RABV infection, the specific role of this interaction remains in question. Here we used live cell imaging to track RABV entry at nerve terminals and studied its retrograde transport along the axon with and without the p75NTR receptor. First, we found that NGF, an endogenous p75NTR ligand, and RABV, are localized in corresponding domains along nerve tips. RABV and NGF were internalized at similar time frames, suggesting comparable entry machineries. Next, we demonstrated that RABV could internalize together with p75NTR. Characterizing RABV retrograde movement along the axon, we showed the virus is transported in acidic compartments, mostly with p75NTR. Interestingly, RABV is transported faster than NGF, suggesting that RABV not only hijacks the transport machinery but can also manipulate it. Co-transport of RABV and NGF identified two modes of transport, slow and fast, that may represent a differential control of the trafficking machinery by RABV. Finally, we determined that p75NTR-dependent transport of RABV is faster and more directed than p75NTR-independent RABV transport. This fast route to the neuronal cell body is characterized by both an increase in instantaneous velocities and fewer, shorter stops en route. Hence, RABV may employ p75NTR-dependent transport as a fast mechanism to facilitate movement to the CNS.

  4. Inhibiting poly(ADP-ribosylation) improves axon regeneration

    Science.gov (United States)

    Byrne, Alexandra B; McWhirter, Rebecca D; Sekine, Yuichi; Strittmatter, Stephen M; Miller, David M; Hammarlund, Marc

    2016-01-01

    The ability of a neuron to regenerate its axon after injury depends in part on its intrinsic regenerative potential. Here, we identify novel intrinsic regulators of axon regeneration: poly(ADP-ribose) glycohodrolases (PARGs) and poly(ADP-ribose) polymerases (PARPs). PARGs, which remove poly(ADP-ribose) from proteins, act in injured C. elegans GABA motor neurons to enhance axon regeneration. PARG expression is regulated by DLK signaling, and PARGs mediate DLK function in enhancing axon regeneration. Conversely, PARPs, which add poly(ADP-ribose) to proteins, inhibit axon regeneration of both C. elegans GABA neurons and mammalian cortical neurons. Furthermore, chemical PARP inhibitors improve axon regeneration when administered after injury. Our results indicate that regulation of poly(ADP-ribose) levels is a critical function of the DLK regeneration pathway, that poly-(ADP ribosylation) inhibits axon regeneration across species, and that chemical inhibition of PARPs can elicit axon regeneration. DOI: http://dx.doi.org/10.7554/eLife.12734.001

  5. New insights into mRNA trafficking in axons

    NARCIS (Netherlands)

    Gumy, Laura; Katrukha, Eugene; Kapitein, Lukas; Hoogenraad, Casper

    2014-01-01

    In recent years, it has been demonstrated that mRNAs localize to axons of young and mature central and peripheral nervous system neurons in culture and in vivo. Increasing evidence is supporting a fundamental role for the local translation of these mRNAs in neuronal function by regulating axon growt

  6. Spontaneous axonal regeneration in rodent spinal cord after ischemic injury

    DEFF Research Database (Denmark)

    von Euler, Mia; Janson, A M; Larsen, Jytte Overgaard;

    2002-01-01

    Here we present evidence for spontaneous and long-lasting regeneration of CNS axons after spinal cord lesions in adult rats. The length of 200 kD neurofilament (NF)-immunolabeled axons was estimated after photochemically induced ischemic spinal cord lesions using a stereological tool. The total l...

  7. CHD7, the gene mutated in CHARGE syndrome, regulates genes involved in neural crest cell guidance.

    Science.gov (United States)

    Schulz, Yvonne; Wehner, Peter; Opitz, Lennart; Salinas-Riester, Gabriela; Bongers, Ernie M H F; van Ravenswaaij-Arts, Conny M A; Wincent, Josephine; Schoumans, Jacqueline; Kohlhase, Jürgen; Borchers, Annette; Pauli, Silke

    2014-08-01

    Heterozygous loss of function mutations in CHD7 (chromodomain helicase DNA-binding protein 7) lead to CHARGE syndrome, a complex developmental disorder affecting craniofacial structures, cranial nerves and several organ systems. Recently, it was demonstrated that CHD7 is essential for the formation of multipotent migratory neural crest cells, which migrate from the neural tube to many regions of the embryo, where they differentiate into various tissues including craniofacial and heart structures. So far, only few CHD7 target genes involved in neural crest cell development have been identified and the role of CHD7 in neural crest cell guidance and the regulation of mesenchymal-epithelial transition are unknown. Therefore, we undertook a genome-wide microarray expression analysis on wild-type and CHD7 deficient (Chd7 (Whi/+) and Chd7 (Whi/Whi)) mouse embryos at day 9.5, a time point of neural crest cell migration. We identified 98 differentially expressed genes between wild-type and Chd7 (Whi/Whi) embryos. Interestingly, many misregulated genes are involved in neural crest cell and axon guidance such as semaphorins and ephrin receptors. By performing knockdown experiments for Chd7 in Xenopus laevis embryos, we found abnormalities in the expression pattern of Sema3a, a protein involved in the pathogenesis of Kallmann syndrome, in vivo. In addition, we detected non-synonymous SEMA3A variations in 3 out of 45 CHD7-negative CHARGE patients. In summary, we discovered for the first time that Chd7 regulates genes involved in neural crest cell guidance, demonstrating a new aspect in the pathogenesis of CHARGE syndrome. Furthermore, we showed for Sema3a a conserved regulatory mechanism across different species, highlighting its significance during development. Although we postulated that the non-synonymous SEMA3A variants which we found in CHD7-negative CHARGE patients alone are not sufficient to produce the phenotype, we suggest an important modifier role for SEMA3A in the

  8. Non-Cell-Autonomous Regulation of Retrograde Motoneuronal Axonal Transport in an SBMA Mouse Model

    Science.gov (United States)

    Halievski, Katherine; Kemp, Michael Q.; Breedlove, S. Marc; Miller, Kyle E.

    2016-01-01

    Abstract Defects in axonal transport are seen in motoneuronal diseases, but how that impairment comes about is not well understood. In spinal bulbar muscular atrophy (SBMA), a disorder linked to a CAG/polyglutamine repeat expansion in the androgen receptor (AR) gene, the disease-causing AR disrupts axonal transport by acting in both a cell-autonomous fashion in the motoneurons themselves, and in a non-cell-autonomous fashion in muscle. The non-cell-autonomous mechanism is suggested by data from a unique “myogenic” transgenic (TG) mouse model in which an AR transgene expressed exclusively in skeletal muscle fibers triggers an androgen-dependent SBMA phenotype, including defects in retrograde transport. However, motoneurons in this TG model retain the endogenous AR gene, leaving open the possibility that impairments in transport in this model also depend on ARs in the motoneurons themselves. To test whether non-cell-autonomous mechanisms alone can perturb retrograde transport, we generated male TG mice in which the endogenous AR allele has the testicular feminization mutation (Tfm) and, consequently, is nonfunctional. Males carrying the Tfm allele alone show no deficits in motor function or axonal transport, with or without testosterone treatment. However, when Tfm males carrying the myogenic transgene (Tfm/TG) are treated with testosterone, they develop impaired motor function and defects in retrograde transport, having fewer retrogradely labeled motoneurons and deficits in endosomal flux based on time-lapse video microscopy of living axons. These findings demonstrate that non-cell-autonomous disease mechanisms originating in muscle are sufficient to induce defects in retrograde transport in motoneurons. PMID:27517091

  9. Functional Impact of Corticotropin-Releasing Factor Exposure on Tau Phosphorylation and Axon Transport.

    Directory of Open Access Journals (Sweden)

    Michelle H Le

    Full Text Available Stress exposure or increased levels of corticotropin-releasing factor (CRF induce hippocampal tau phosphorylation (tau-P in rodent models, a process that is dependent on the type-1 CRF receptor (CRFR1. Although these preclinical studies on stress-induced tau-P provide mechanistic insight for epidemiological work that identifies stress as a risk factor for Alzheimer's disease (AD, the actual impact of stress-induced tau-P on neuronal function remains unclear. To determine the functional consequences of stress-induced tau-P, we developed a novel mouse neuronal cell culture system to explore the impact of acute (0.5hr and chronic (2hr CRF treatment on tau-P and integral cell processes such as axon transport. Consistent with in vivo reports, we found that chronic CRF treatment increased tau-P levels and caused globular accumulations of phosphorylated tau in dendritic and axonal processes. Furthermore, while both acute and chronic CRF treatment led to significant reduction in CREB activation and axon transport of brain-derived neurotrophic factor (BDNF, this was not the case with mitochondrial transport. Acute CRF treatment caused increased mitochondrial velocity and distance traveled in neurons, while chronic CRF treatment modestly decreased mitochondrial velocity and greatly increased distance traveled. These results suggest that transport of cellular energetics may take priority over growth factors during stress. Tau-P was required for these changes, as co-treatment of CRF with a GSK kinase inhibitor prevented CRF-induced tau-P and all axon transport changes. Collectively, our results provide mechanistic insight into the consequences of stress peptide-induced tau-P and provide an explanation for how chronic stress via CRF may lead to neuronal vulnerability in AD.

  10. Attenuated traumatic axonal injury and improved functional outcome after traumatic brain injury in mice lacking Sarm1.

    Science.gov (United States)

    Henninger, Nils; Bouley, James; Sikoglu, Elif M; An, Jiyan; Moore, Constance M; King, Jean A; Bowser, Robert; Freeman, Marc R; Brown, Robert H

    2016-04-01

    Axonal degeneration is a critical, early event in many acute and chronic neurological disorders. It has been consistently observed after traumatic brain injury, but whether axon degeneration is a driver of traumatic brain injury remains unclear. Molecular pathways underlying the pathology of traumatic brain injury have not been defined, and there is no efficacious treatment for traumatic brain injury. Here we show that mice lacking the mouse Toll receptor adaptor Sarm1 (sterile α/Armadillo/Toll-Interleukin receptor homology domain protein) gene, a key mediator of Wallerian degeneration, demonstrate multiple improved traumatic brain injury-associated phenotypes after injury in a closed-head mild traumatic brain injury model. Sarm1(-/-) mice developed fewer β-amyloid precursor protein aggregates in axons of the corpus callosum after traumatic brain injury as compared to Sarm1(+/+) mice. Furthermore, mice lacking Sarm1 had reduced plasma concentrations of the phophorylated axonal neurofilament subunit H, indicating that axonal integrity is maintained after traumatic brain injury. Strikingly, whereas wild-type mice exibited a number of behavioural deficits after traumatic brain injury, we observed a strong, early preservation of neurological function in Sarm1(-/-) animals. Finally, using in vivo proton magnetic resonance spectroscopy we found tissue signatures consistent with substantially preserved neuronal energy metabolism in Sarm1(-/-) mice compared to controls immediately following traumatic brain injury. Our results indicate that the SARM1-mediated prodegenerative pathway promotes pathogenesis in traumatic brain injury and suggest that anti-SARM1 therapeutics are a viable approach for preserving neurological function after traumatic brain injury. PMID:26912636

  11. Attenuated traumatic axonal injury and improved functional outcome after traumatic brain injury in mice lacking Sarm1.

    Science.gov (United States)

    Henninger, Nils; Bouley, James; Sikoglu, Elif M; An, Jiyan; Moore, Constance M; King, Jean A; Bowser, Robert; Freeman, Marc R; Brown, Robert H

    2016-04-01

    Axonal degeneration is a critical, early event in many acute and chronic neurological disorders. It has been consistently observed after traumatic brain injury, but whether axon degeneration is a driver of traumatic brain injury remains unclear. Molecular pathways underlying the pathology of traumatic brain injury have not been defined, and there is no efficacious treatment for traumatic brain injury. Here we show that mice lacking the mouse Toll receptor adaptor Sarm1 (sterile α/Armadillo/Toll-Interleukin receptor homology domain protein) gene, a key mediator of Wallerian degeneration, demonstrate multiple improved traumatic brain injury-associated phenotypes after injury in a closed-head mild traumatic brain injury model. Sarm1(-/-) mice developed fewer β-amyloid precursor protein aggregates in axons of the corpus callosum after traumatic brain injury as compared to Sarm1(+/+) mice. Furthermore, mice lacking Sarm1 had reduced plasma concentrations of the phophorylated axonal neurofilament subunit H, indicating that axonal integrity is maintained after traumatic brain injury. Strikingly, whereas wild-type mice exibited a number of behavioural deficits after traumatic brain injury, we observed a strong, early preservation of neurological function in Sarm1(-/-) animals. Finally, using in vivo proton magnetic resonance spectroscopy we found tissue signatures consistent with substantially preserved neuronal energy metabolism in Sarm1(-/-) mice compared to controls immediately following traumatic brain injury. Our results indicate that the SARM1-mediated prodegenerative pathway promotes pathogenesis in traumatic brain injury and suggest that anti-SARM1 therapeutics are a viable approach for preserving neurological function after traumatic brain injury.

  12. SnoN facilitates axonal regeneration after spinal cord injury.

    Directory of Open Access Journals (Sweden)

    Jiun L Do

    Full Text Available Adult CNS neurons exhibit a reduced capacity for growth compared to developing neurons, due in part to downregulation of growth-associated genes as development is completed. We tested the hypothesis that SnoN, an embryonically regulated transcription factor that specifies growth of the axonal compartment, can enhance growth in injured adult neurons. In vitro, SnoN overexpression in dissociated adult DRG neuronal cultures significantly enhanced neurite outgrowth. Moreover, TGF-β1, a negative regulator of SnoN, inhibited neurite outgrowth, and SnoN over-expression overcame this inhibition. We then examined whether SnoN influenced axonal regeneration in vivo: indeed, expression of a mutant form of SnoN resistant to degradation significantly enhanced axonal regeneration following cervical spinal cord injury, despite peri-lesional upregulation of TGF-β1. Thus, a developmental mechanism that specifies extension of the axonal compartment also promotes axonal regeneration after adult CNS injury.

  13. A paradigm shift in EPH receptor interaction: biological relevance of EPHB6 interaction with EPHA2 and EPHB2 in breast carcinoma cell lines.

    Science.gov (United States)

    Fox, Brian P; Kandpal, Raj P

    2011-01-01

    EPH receptors are the largest known family of receptor tyrosine kinases characterized in humans. These proteins are involved in axon guidance, tissue organization, synaptic plasticity, vascular development and the progression of various diseases including cancer. The varied biological effects of EPH receptors are mediated in part by the expression of these proteins and their intracellular binding proteins. The ability of EPH molecules to form heterodimers within their own class has been suggested, although not exhaustively characterized. We have clarified this phenomenon by showing that EPHB6, a kinase-deficient receptor, can interact with EPHB2 in mammalian cells, and more significantly EPHB6 interacts with EPHA2. However, EPHB6 does not interact with another kinase-deficient receptor, EPHA10. The interaction between EPHB6 and EPHA2 is the first demonstration of an A-type receptor interacting with a B-type receptor. Furthermore, we correlated relative expression of EPHB6, EPHB2 and EPHA2 with non-invasive and invasive phenotypes of breast tumor cell lines. Our results indicate that tumor invasiveness-suppressing activity of EPHB6 is mediated by its ability to sequester other kinase-sufficient and oncogenic EPH receptors. These observations suggest that cellular phenotypes may, in part, be attributed to a combinatorial expression of EPH receptors and heteromeric interactions among the same class, as well as between two classes, of EPH receptors. Our results also suggest that EPHA10 may transduce signals by interacting with other kinase-sufficient receptors in a similar manner. PMID:21737611

  14. Brain injury tolerance limit based on computation of axonal strain.

    Science.gov (United States)

    Sahoo, Debasis; Deck, Caroline; Willinger, Rémy

    2016-07-01

    Traumatic brain injury (TBI) is the leading cause of death and permanent impairment over the last decades. In both the severe and mild TBIs, diffuse axonal injury (DAI) is the most common pathology and leads to axonal degeneration. Computation of axonal strain by using finite element head model in numerical simulation can enlighten the DAI mechanism and help to establish advanced head injury criteria. The main objective of this study is to develop a brain injury criterion based on computation of axonal strain. To achieve the objective a state-of-the-art finite element head model with enhanced brain and skull material laws, was used for numerical computation of real world head trauma. The implementation of new medical imaging data such as, fractional anisotropy and axonal fiber orientation from Diffusion Tensor Imaging (DTI) of 12 healthy patients into the finite element brain model was performed to improve the brain constitutive material law with more efficient heterogeneous anisotropic visco hyper-elastic material law. The brain behavior has been validated in terms of brain deformation against Hardy et al. (2001), Hardy et al. (2007), and in terms of brain pressure against Nahum et al. (1977) and Trosseille et al. (1992) experiments. Verification of model stability has been conducted as well. Further, 109 well-documented TBI cases were simulated and axonal strain computed to derive brain injury tolerance curve. Based on an in-depth statistical analysis of different intra-cerebral parameters (brain axonal strain rate, axonal strain, first principal strain, Von Mises strain, first principal stress, Von Mises stress, CSDM (0.10), CSDM (0.15) and CSDM (0.25)), it was shown that axonal strain was the most appropriate candidate parameter to predict DAI. The proposed brain injury tolerance limit for a 50% risk of DAI has been established at 14.65% of axonal strain. This study provides a key step for a realistic novel injury metric for DAI. PMID:27038501

  15. A nerve guidance conduit with topographical and biochemical cues: potential application using human neural stem cells

    Science.gov (United States)

    Jenkins, Phillip M.; Laughter, Melissa R.; Lee, David J.; Lee, Young M.; Freed, Curt R.; Park, Daewon

    2015-06-01

    Despite major advances in the pathophysiological understanding of peripheral nerve damage, the treatment of nerve injuries still remains an unmet medical need. Nerve guidance conduits present a promising treatment option by providing a growth-permissive environment that 1) promotes neuronal cell survival and axon growth and 2) directs axonal extension. To this end, we designed an electrospun nerve guidance conduit using a blend of polyurea and poly-caprolactone with both biochemical and topographical cues. Biochemical cues were integrated into the conduit by functionalizing the polyurea with RGD to improve cell attachment. Topographical cues that resemble natural nerve tissue were incorporated by introducing intraluminal microchannels aligned with nanofibers. We determined that electrospinning the polymer solution across a two electrode system with dissolvable sucrose fibers produced a polymer conduit with the appropriate biomimetic properties. Human neural stem cells were cultured on the conduit to evaluate its ability to promote neuronal growth and axonal extension. The nerve guidance conduit was shown to enhance cell survival, migration, and guide neurite extension.

  16. Clinical features of diffuse axonal injury

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Objective: To analyze the mechanism of diffuse axonal injury (DAI) and study the relationship between DAI and brain concussion, brain contusion, and primary brain stem injury.Methods: The clinical data and iconographic characteristics of 56 patients with DAI were analyzed retrospectively.Results: Traffic accidents were the main cause of DAI. Among the 56 cases, 34 were injured for at least twice, and 71.43% of the patients were complicated with contusion.Conclusions: It is considered that DAI is a common pattern of primary brain injury, which is often underestimated. And DAI includes cerebral concussion and primary brain injury, and is often complicated by cerebral cortex contusion. Therefore, it is very simple and practical to divide primary brain injuries into local and diffuse injuries.

  17. Regulatory guidance document

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1994-05-01

    The Office of Civilian Radioactive Waste Management (OCRWM) Program Management System Manual requires preparation of the OCRWM Regulatory Guidance Document (RGD) that addresses licensing, environmental compliance, and safety and health compliance. The document provides: regulatory compliance policy; guidance to OCRWM organizational elements to ensure a consistent approach when complying with regulatory requirements; strategies to achieve policy objectives; organizational responsibilities for regulatory compliance; guidance with regard to Program compliance oversight; and guidance on the contents of a project-level Regulatory Compliance Plan. The scope of the RGD includes site suitability evaluation, licensing, environmental compliance, and safety and health compliance, in accordance with the direction provided by Section 4.6.3 of the PMS Manual. Site suitability evaluation and regulatory compliance during site characterization are significant activities, particularly with regard to the YW MSA. OCRWM`s evaluation of whether the Yucca Mountain site is suitable for repository development must precede its submittal of a license application to the Nuclear Regulatory Commission (NRC). Accordingly, site suitability evaluation is discussed in Chapter 4, and the general statements of policy regarding site suitability evaluation are discussed in Section 2.1. Although much of the data and analyses may initially be similar, the licensing process is discussed separately in Chapter 5. Environmental compliance is discussed in Chapter 6. Safety and Health compliance is discussed in Chapter 7.

  18. PIV Logon Configuration Guidance

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Glen Alan [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2016-03-04

    This document details the configurations and enhancements implemented to support the usage of federal Personal Identity Verification (PIV) Card for logon on unclassified networks. The guidance is a reference implementation of the configurations and enhancements deployed at the Los Alamos National Laboratory (LANL) by Network and Infrastructure Engineering – Core Services (NIE-CS).

  19. The Counseling & Guidance Curriculum.

    Science.gov (United States)

    Ediger, Marlow

    Counseling and guidance services are vital in any school curriculum. Counselors may themselves be dealing with students of diverse abilities and handicaps. Counselors may have to work with students affected by drug addiction, fetal alcohol syndrome, homelessness, poverty, Acquired Immune Deficiency Syndrome (AIDS) and divorce. Students may present…

  20. Regulatory guidance document

    International Nuclear Information System (INIS)

    The Office of Civilian Radioactive Waste Management (OCRWM) Program Management System Manual requires preparation of the OCRWM Regulatory Guidance Document (RGD) that addresses licensing, environmental compliance, and safety and health compliance. The document provides: regulatory compliance policy; guidance to OCRWM organizational elements to ensure a consistent approach when complying with regulatory requirements; strategies to achieve policy objectives; organizational responsibilities for regulatory compliance; guidance with regard to Program compliance oversight; and guidance on the contents of a project-level Regulatory Compliance Plan. The scope of the RGD includes site suitability evaluation, licensing, environmental compliance, and safety and health compliance, in accordance with the direction provided by Section 4.6.3 of the PMS Manual. Site suitability evaluation and regulatory compliance during site characterization are significant activities, particularly with regard to the YW MSA. OCRWM's evaluation of whether the Yucca Mountain site is suitable for repository development must precede its submittal of a license application to the Nuclear Regulatory Commission (NRC). Accordingly, site suitability evaluation is discussed in Chapter 4, and the general statements of policy regarding site suitability evaluation are discussed in Section 2.1. Although much of the data and analyses may initially be similar, the licensing process is discussed separately in Chapter 5. Environmental compliance is discussed in Chapter 6. Safety and Health compliance is discussed in Chapter 7

  1. Career guidance on the move

    DEFF Research Database (Denmark)

    Thomsen, Rie

    2013-01-01

    This article is about how the notion of place can be used in an analysis of career guidance practices and their development. It is about how a focus on the context of career guidance can develop an awareness of the place where guidance is practiced and support the development of career guidance...... in new places. In this article I introduce an analytical perspective on place; I give the example of the guidance café a practice development that took place into serious consideration because it was an attempt to develop career guidance practice through relocating it....

  2. The Wnt Frizzled Receptor MOM-5 Regulates the UNC-5 Netrin Receptor through Small GTPase-Dependent Signaling to Determine the Polarity of Migrating Cells.

    Directory of Open Access Journals (Sweden)

    Naomi Levy-Strumpf

    2015-08-01

    Full Text Available Wnt and Netrin signaling regulate diverse essential functions. Using a genetic approach combined with temporal gene expression analysis, we found a regulatory link between the Wnt receptor MOM-5/Frizzled and the UNC-6/Netrin receptor UNC-5. These two receptors play key roles in guiding cell and axon migrations, including the migration of the C. elegans Distal Tip Cells (DTCs. DTCs migrate post-embryonically in three sequential phases: in the first phase along the Antero-Posterior (A/P axis, in the second, along the Dorso-Ventral (D/V axis, and in the third, along the A/P axis. Loss of MOM-5/Frizzled function causes third phase A/P polarity reversals of the migrating DTCs. We show that an over-expression of UNC-5 causes similar DTC A/P polarity reversals and that unc-5 deficits markedly suppress the A/P polarity reversals caused by mutations in mom-5/frizzled. This implicates MOM-5/Frizzled as a negative regulator of unc-5. We provide further evidence that small GTPases mediate MOM-5's regulation of unc-5 such that one outcome of impaired function of small GTPases like CED-10/Rac and MIG-2/RhoG is an increase in unc-5 function. The work presented here demonstrates the existence of cross talk between components of the Netrin and Wnt signaling pathways and provides further insights into the way guidance signaling mechanisms are integrated to orchestrate directed cell migration.

  3. Inhibition of TLR4 Signalling-Induced Inflammation Attenuates Secondary Injury after Diffuse Axonal Injury in Rats

    Science.gov (United States)

    Zhao, Yonglin; Zhang, Ming; Zhao, Junjie; Ma, Xudong; Huang, Tingqin; Pang, Honggang

    2016-01-01

    Increasing evidence suggests that secondary injury after diffuse axonal injury (DAI) damages more axons than the initial insult, but the underlying mechanisms of this phenomenon are not fully understood. Recent studies show that toll-like receptor 4 (TLR4) plays a critical role in promoting adaptive immune responses and have been shown to be associated with brain damage. The purpose of this study was to investigate the role of the TLR4 signalling pathway in secondary axonal injury in the cortices of DAI rats. TLR4 was mainly localized in microglial cells and neurons, and the levels of TLR4 downstream signalling molecules, including TLR4, myeloid differentiation primary response gene 88, toll/IR-1-(TIR-) domain-containing adaptor protein inducing interferon-beta, interferon regulatory factor 3, interferon β, nuclear factor κB (NF-κB) p65, and phospho-NF-κB p65, significantly increased and peaked at 1 d after DAI. Inhibition of TLR4 by TAK-242 attenuated apoptosis, neuronal and axonal injury, and glial responses. The neuroprotective effects of TLR4 inhibition were associated with decreases in the levels of TLR4 downstream signalling molecules and inflammatory factors, including interleukin-1β, interleukin-6, and tumour necrosis factor-α. These results suggest that the TLR4 signalling pathway plays an important role in secondary injury and may be an important therapeutic target following DAI.

  4. Intra-axonal myosin and actin in nerve regeneration.

    Science.gov (United States)

    McQuarrie, Irvine G; Lund, Linda M

    2009-10-01

    A focused review of sciatic nerve regeneration in the rat model, based on research conducted by the authors, is presented. We examine structural proteins carried distally in the axon by energy-requiring motor enzymes, using protein chemistry and molecular biology techniques in combination with immunohistochemistry. Relevant findings from other laboratories are cited and discussed. The general conclusion is that relatively large amounts of actin and tubulin are required to construct a regenerating axon and that these materials mainly originate in the parent axon. The motor enzymes that carry these proteins forward as macromolecules include kinesin and dynein but probably also include myosin. PMID:19927086

  5. High copy arrays containing a sequence upstream of mec-3 alter cell migration and axonal morphology in C. elegans

    Directory of Open Access Journals (Sweden)

    Patchen Brandi

    2001-01-01

    Full Text Available Abstract Background The Caenorhabditis elegans gene mec-3 encodes a LIM-homeodomain protein that is a master regulator of touch receptor neuron genes. Two of the touch neurons, the ALM neurons, are generated in the anterior of the animal and then migrate to near the middle of the animal. In animals transformed with a sequence upstream of mec-3, the ALM touch receptor neurons failed to migrate to their normal positions and sometimes migrated in the wrong direction, and the PLM touch receptor neurons showed axonal defects. Here we characterize this effect and identify the sequence causing the cell migration and axonal defects. Results The ALM migration defect did not result from RNA interference (RNAi, nonspecific effects of carrying a transgenic array, expression of GFP, or the marker gene used to make the transformants. Instead, the ALM migration defect resulted from transgenic arrays containing many copies of a specific 104 bp DNA sequence. Transgenic arrays containing this sequence did not affect all cell migrations. Conclusions The mec-3 upstream sequence appeared to be sequestering (titrating out a specific DNA-binding factor that is required for the ALMs to migrate correctly. Because titration of this factor could reverse the direction of ALM migrations, it may be part of a program that specifies both the direction and extent of ALM migrations. mec-3 is a master regulator of touch receptor neuron genes, so the factor or factors that bind this sequence may also be involved in specifying the fate of touch receptor neurons.

  6. New Interpretations of Guidance Role

    Science.gov (United States)

    Kerlan, Julius H.; Ryan, Charles W.

    1972-01-01

    A panoramic view of Guidance Division general sessions and workshops covering some exemplary career guidance programs, as well as such topics as career choice, leadership, evaluation, and program development and management. Presented at the Guidance division session of the American Vocational Association 1971 annual meeting. (Editor/MU)

  7. Environmental guidance regulatory bulletin

    International Nuclear Information System (INIS)

    This document describes the background on expanding public participation in the Resource Conservation and Recovery Act and DOE's response. The bulletin also describes the changes made by the final rule to existing regulations, guidance provided by EPA in the preamble and in the revised RCRA Public Participation Manual, the relationship between public participation and environmental justice, and DOE's recent public participation and environmental justice initiatives

  8. Differential effects of human L1CAM mutations on complementing guidance and synaptic defects in Drosophila melanogaster.

    Directory of Open Access Journals (Sweden)

    Sirisha Kudumala

    Full Text Available A large number of different pathological L1CAM mutations have been identified that result in a broad spectrum of neurological and non-neurological phenotypes. While many of these mutations have been characterized for their effects on homophilic and heterophilic interactions, as well as expression levels in vitro, there are only few studies on their biological consequences in vivo. The single L1-type CAM gene in Drosophila, neuroglian (nrg, has distinct functions during axon guidance and synapse formation and the phenotypes of nrg mutants can be rescued by the expression of human L1CAM. We previously showed that the highly conserved intracellular FIGQY Ankyrin-binding motif is required for L1CAM-mediated synapse formation, but not for neurite outgrowth or axon guidance of the Drosophila giant fiber (GF neuron. Here, we use the GF as a model neuron to characterize the pathogenic L120V, Y1070C, C264Y, H210Q, E309K and R184Q extracellular L1CAM missense mutations and a L1CAM protein with a disrupted ezrin-moesin-radixin (ERM binding site to investigate the signaling requirements for neuronal development. We report that different L1CAM mutations have distinct effects on axon guidance and synapse formation. Furthermore, L1CAM homophilic binding and signaling via the ERM motif is essential for axon guidance in Drosophila. In addition, the human pathological H210Q, R184Q and Y1070C, but not the E309K and L120V L1CAM mutations affect outside-in signaling via the FIGQY Ankyrin binding domain which is required for synapse formation. Thus, the pathological phenotypes observed in humans are likely to be caused by the disruption of signaling required for both, guidance and synaptogenesis.

  9. Axon diameter mapping in crossing fibers with diffusion MRI

    DEFF Research Database (Denmark)

    Zhang, Hui; Dyrby, Tim B; Alexander, Daniel C

    2011-01-01

    tissue than measures derived from diffusion tensor imaging. Most existing techniques for axon diameter mapping assume a single axon orientation in the tissue model, which limits their application to only the most coherently oriented brain white matter, such as the corpus callosum, where the single...... orientation assumption is a reasonable one. However, fiber crossings and other complex configurations are widespread in the brain. In such areas, the existing techniques will fail to provide useful axon diameter indices for any of the individual fiber populations. We propose a novel crossing fiber tissue...... of the technique by establishing reasonable axon diameter indices in the crossing region at the interface of the cingulum and the corpus callosum....

  10. Internodal function in normal and regenerated mammalian axons

    DEFF Research Database (Denmark)

    Moldovan, M; Krarup, C

    2007-01-01

    human nerves. CONCLUSION: The data suggest that persistently shorter regenerated internodes lead to increased Na+/K+-pump activity in response to increased Na+ entry during conduction. This may impair axonal function during prolonged repetitive activity and drain the energy reserves of the axons.......AIM: Following Wallerian degeneration, peripheral myelinated axons have the ability to regenerate and, given a proper pathway, establish functional connections with targets. In spite of this capacity, the clinical outcome of nerve regeneration remains unsatisfactory. Early studies have found...... that regenerated internodes remain persistently short though this abnormality did not seem to influence recovery in conduction. It remains unclear to which extent abnormalities in axonal function itself may contribute to the poor outcome of nerve regeneration. METHODS: We review experimental evidence indicating...

  11. Structural plasticity of axon terminals in the adult.

    Science.gov (United States)

    Gogolla, Nadine; Galimberti, Ivan; Caroni, Pico

    2007-10-01

    There is now conclusive evidence for widespread ongoing structural plasticity of presynaptic boutons and axon side-branches in the adult brain. The plasticity complements that of postsynaptic spines, but axonal plasticity samples larger volumes of neuropil, and has a larger impact on circuit remodeling. Axons from distinct neurons exhibit unique ratios of stable (t1/2>9 months) and dynamic (t1/2 5-20 days) boutons, which persist as spatially intermingled subgroups along terminal arbors. In addition, phases of side-branch dynamics mediate larger scale remodeling guided by synaptogenesis. The plasticity is most pronounced during critical periods; its patterns and outcome are controlled by Hebbian mechanisms and intrinsic neuronal factors. Novel experience, skill learning, life-style, and age can persistently modify local circuit structure through axonal structural plasticity.

  12. Neurons in the lateral part of the lumbar spinal cord show distinct novel axon trajectories and are excited by short propriospinal ascending inputs.

    Science.gov (United States)

    Antal, Zs; Luz, L L; Safronov, B V; Antal, M; Szücs, Peter

    2016-05-01

    The role of spinal dorsal horn propriospinal connections in nociceptive processing is not yet established. Recently described, rostrocaudally oriented axon collaterals of lamina I projection and local-circuit neurons (PNs and LCNs) running in the dorsolateral funiculus (DLF) may serve as the anatomical substrate for intersegmental processing. Putative targets of these axons include lateral dendrites of superficial dorsal horn neurons, including PNs, and also neurons in the lateral spinal nucleus (LSN) that are thought to be important integrator units receiving, among others, visceral sensory information. Here we used an intact spinal cord preparation to study intersegmental connections within the lateral part of the superficial dorsal horn. We detected brief monosynaptic and prolonged polysynaptic excitation of lamina I and LSN neurons when stimulating individual dorsal horn neurons located caudally, even in neighboring spinal cord segments. These connections, however, were infrequent. We also revealed that some projection neurons outside the dorsal grey matter and in the LSN have distinct, previously undescribed course of their projection axon. Our findings indicate that axon collaterals of lamina I PNs and LCNs in the DLF rarely form functional connections with other lamina I and LSN neurons and that the majority of their targets are on other elements of the dorsal horn. The unique axon trajectories of neurons in the dorsolateral aspect of the spinal cord, including the LSN do not fit our present understanding of midline axon guidance and suggest that their function and development differ from the neurons inside lamina I. These findings emphasize the importance of understanding the connectivity matrix of the superficial dorsal horn in order to decipher spinal sensory information processing. PMID:25912439

  13. Role of ERK1/2 MAPK signaling in the maintenance of myelin and axonal integrity in the adult CNS.

    Science.gov (United States)

    Ishii, Akihiro; Furusho, Miki; Dupree, Jeffrey L; Bansal, Rashmi

    2014-11-26

    Oligodendrocytes form myelin during postnatal development and then maintain a functional myelin sheath throughout adult life. While many regulators of developmental myelination have been identified, the signal transduction mechanisms that regulate oligodendrocyte functions in adulthood are not well understood. The extracellular signal-regulated kinases-1 and -2 (ERK1/2), downstream mediators of mitogen-activated protein kinases (MAPKs), have emerged as prominent regulators of myelin formation. Here, we investigated whether these signaling molecules are also required for myelin maintenance in the adult CNS. Inducible conditional ablation of Erk1/2 in oligodendrocytes of the adult CNS resulted in a downregulation of myelin gene expression. Although myelin thickness was reduced and some axons were demyelinated, the majority of axons were wrapped by intact myelin sheaths that appeared structurally normal. However, late onset of progressive axonal degeneration, accompanied by astrogliosis, microglial activation, partial loss of oligodendrocytes, and functional impairment, occurred in the adult mice lacking ERK1/2 activity. Conditional ablation of Fibroblast Growth Factor receptors-1 and -2 (FGFR1/2) in oligodendrocytes also resulted in downregulation of myelin gene expression and development of axonal degeneration as the mice aged. Further, the level of the key transcription factor myelin gene regulatory factor (Myrf) was downregulated or upregulated in mice with genetic loss or gain of ERK1/2 function, respectively. Together, our studies demonstrate that ERK1/2-MAPK signaling is required for the long-term maintenance of myelin and axonal integrity in the adult CNS and suggest that FGFR1/2 and Myrf may, in part, contribute to signaling upstream and downstream of ERK1/2 in maintaining these oligodendrocyte functions during adulthood. PMID:25429144

  14. Changes in prefrontal axons may disrupt the network in autism

    OpenAIRE

    Zikopoulos, Basilis; Barbas, Helen

    2010-01-01

    Neural communication is disrupted in autism by unknown mechanisms. Here we examined whether in autism there are changes in axons, which are the conduit for neural communication. We investigated single axons and their ultrastructure in the white matter of post-mortem human brain tissue below the anterior cingulate cortex (ACC), orbitofrontal (OFC), and lateral (LPFC) prefrontal cortices, which are associated with attention, social interactions, and emotions and have been consistently implicate...

  15. Axonal neuropathy associated with monoclonal gammopathy of undetermined significance

    OpenAIRE

    GORSON, K.; Ropper, A.

    1997-01-01

    OBJECTIVE—The neuropathy associated with monoclonal gammopathy of undetermined significance (MGUS) is typically a predominantly demyelinating process that may have additional features of axonal degeneration. Sixteen patients with MGUS and a pure or predominantly axonal neuropathy are reported and compared with 20 consecutive patients with demyelinating neuropathy and MGUS who were seen during the same period.
METHODS—Retrospective review of a consecutive series of patients w...

  16. 6-Sulphated chondroitins have a positive influence on axonal regeneration.

    Directory of Open Access Journals (Sweden)

    Rachel Lin

    Full Text Available Chondroitin sulphate proteoglycans (CSPGs upregulated in the glial scar inhibit axon regeneration via their sulphated glycosaminoglycans (GAGs. Chondroitin 6-sulphotransferase-1 (C6ST-1 is upregulated after injury leading to an increase in 6-sulphated GAG. In this study, we ask if this increase in 6-sulphated GAG is responsible for the increased inhibition within the glial scar, or whether it represents a partial reversion to the permissive embryonic state dominated by 6-sulphated glycosaminoglycans (GAGs. Using C6ST-1 knockout mice (KO, we studied post-injury changes in chondroitin sulphotransferase (CSST expression and the effect of chondroitin 6-sulphates on both central and peripheral axon regeneration. After CNS injury, wild-type animals (WT showed an increase in mRNA for C6ST-1, C6ST-2 and C4ST-1, but KO did not upregulate any CSSTs. After PNS injury, while WT upregulated C6ST-1, KO showed an upregulation of C6ST-2. We examined regeneration of nigrostriatal axons, which demonstrate mild spontaneous axon regeneration in the WT. KO showed many fewer regenerating axons and more axonal retraction than WT. However, in the PNS, repair of the median and ulnar nerves led to similar and normal levels of axon regeneration in both WT and KO. Functional tests on plasticity after the repair also showed no evidence of enhanced plasticity in the KO. Our results suggest that the upregulation of 6-sulphated GAG after injury makes the extracellular matrix more permissive for axon regeneration, and that the balance of different CSs in the microenvironment around the lesion site is an important factor in determining the outcome of nervous system injury.

  17. Axonal maintenance, glia, exosomes, and heat shock proteins

    OpenAIRE

    Michael Tytell; Lasek, Raymond J.; Harold Gainer

    2016-01-01

    Of all cellular specializations, the axon is especially distinctive because it is a narrow cylinder of specialized cytoplasm called axoplasm with a length that may be orders of magnitude greater than the diameter of the cell body from which it originates. Thus, the volume of axoplasm can be much greater than the cytoplasm in the cell body. This fact raises a logistical problem with regard to axonal maintenance. Many of the components of axoplasm, such as soluble proteins and cytoskeleton, are...

  18. In vivo testing of a 3D bifurcating microchannel scaffold inducing separation of regenerating axon bundles in peripheral nerves

    Science.gov (United States)

    Stoyanova, Irina I.; van Wezel, Richard J. A.; Rutten, Wim L. C.

    2013-12-01

    Artificial nerve guidance channels enhance the regenerative effectiveness in an injured peripheral nerve but the existing design so far has been limited to basic straight tubes simply guiding the growth to bridge the gap. Hence, one of the goals in development of more effective neuroprostheses is to create bidirectional highly selective neuro-electronic interface between a prosthetic device and the severed nerve. A step towards improving selectivity for both recording and stimulation have been made with some recent in vitro studies which showed that three-dimensional (3D) bifurcating microchannels can separate neurites growing on a planar surface and bring them into contact with individual electrodes. Since the growing axons in vivo have the innate tendency to group in bundles surrounded by connective tissue, one of the big challenges in neuro-prosthetic interface design is how to overcome it. Therefore, we performed experiments with 3D bifurcating guidance scaffolds implanted in the sciatic nerve of rats to test if this new channel architecture could trigger separation pattern of ingrowth also in vivo. Our results showed that this new method enabled the re-growth of neurites into channels with gradually diminished width (80, 40 and 20 µm) and facilitated the separation of the axonal bundles with 91% success. It seems that the 3D bifurcating scaffold might contribute towards conveying detailed neural control and sensory feedback to users of prosthetic devices, and thus could improve the quality of their daily life.

  19. Axon-glia interaction and membrane traffic in myelin formation

    Directory of Open Access Journals (Sweden)

    Robin eWhite

    2014-01-01

    Full Text Available In vertebrate nervous systems myelination of neuronal axons has evolved to increase conduction velocity of electrical impulses with minimal space and energy requirements. Myelin is formed by specialised glial cells which ensheath axons with a lipid-rich insulating membrane. Myelination is a multi-step process initiated by axon-glia recognition triggering glial polarisation followed by targeted myelin membrane expansion and compaction. Thereby, a myelin sheath of complex subdomain structure is established. Continuous communication between neurons and glial cells is essential for myelin maintenance and axonal integrity. A diverse group of diseases, from multiple sclerosis to schizophrenia, have been linked to malfunction of myelinating cells reflecting the physiological importance of the axon-glial unit. This review describes the mechanisms of axonal signal integration by oligodendrocytes emphasising the central role of the Src-family kinase Fyn during CNS myelination. Furthermore, we discuss myelin membrane trafficking with particular focus on endocytic recycling and the control of PLP (proteolipid protein transport by SNARE proteins. Finally, PLP mistrafficking is considered in the context of myelin diseases.

  20. Quantitative measurements and modeling of cargo–motor interactions during fast transport in the living axon

    International Nuclear Information System (INIS)

    The kinesins have long been known to drive microtubule-based transport of sub-cellular components, yet the mechanisms of their attachment to cargo remain a mystery. Several different cargo-receptors have been proposed based on their in vitro binding affinities to kinesin-1. Only two of these—phosphatidyl inositol, a negatively charged lipid, and the carboxyl terminus of the amyloid precursor protein (APP-C), a trans-membrane protein—have been reported to mediate motility in living systems. A major question is how these many different cargo, receptors and motors interact to produce the complex choreography of vesicular transport within living cells. Here we describe an experimental assay that identifies cargo–motor receptors by their ability to recruit active motors and drive transport of exogenous cargo towards the synapse in living axons. Cargo is engineered by derivatizing the surface of polystyrene fluorescent nanospheres (100 nm diameter) with charged residues or with synthetic peptides derived from candidate motor receptor proteins, all designed to display a terminal COOH group. After injection into the squid giant axon, particle movements are imaged by laser-scanning confocal time-lapse microscopy. In this report we compare the motility of negatively charged beads with APP-C beads in the presence of glycine-conjugated non-motile beads using new strategies to measure bead movements. The ensuing quantitative analysis of time-lapse digital sequences reveals detailed information about bead movements: instantaneous and maximum velocities, run lengths, pause frequencies and pause durations. These measurements provide parameters for a mathematical model that predicts the spatiotemporal evolution of distribution of the two different types of bead cargo in the axon. The results reveal that negatively charged beads differ from APP-C beads in velocity and dispersion, and predict that at long time points APP-C will achieve greater progress towards the presynaptic

  1. Axon Regeneration Is Regulated by Ets-C/EBP Transcription Complexes Generated by Activation of the cAMP/Ca2+ Signaling Pathways.

    Science.gov (United States)

    Li, Chun; Hisamoto, Naoki; Matsumoto, Kunihiro

    2015-10-01

    The ability of specific neurons to regenerate their axons after injury is governed by cell-intrinsic regeneration pathways. In Caenorhabditis elegans, the JNK and p38 MAPK pathways are important for axon regeneration. Axonal injury induces expression of the svh-2 gene encoding a receptor tyrosine kinase, stimulation of which by the SVH-1 growth factor leads to activation of the JNK pathway. Here, we identify ETS-4 and CEBP-1, related to mammalian Ets and C/EBP, respectively, as transcriptional activators of svh-2 expression following axon injury. ETS-4 and CEBP-1 function downstream of the cAMP and Ca2+-p38 MAPK pathways, respectively. We show that PKA-dependent phosphorylation of ETS-4 promotes its complex formation with CEBP-1. Furthermore, activation of both cAMP and Ca2+ signaling is required for activation of svh-2 expression. Thus, the cAMP/Ca2+ signaling pathways cooperatively activate the JNK pathway, which then promotes axon regeneration.

  2. Axon Regeneration Is Regulated by Ets-C/EBP Transcription Complexes Generated by Activation of the cAMP/Ca2+ Signaling Pathways.

    Directory of Open Access Journals (Sweden)

    Chun Li

    2015-10-01

    Full Text Available The ability of specific neurons to regenerate their axons after injury is governed by cell-intrinsic regeneration pathways. In Caenorhabditis elegans, the JNK and p38 MAPK pathways are important for axon regeneration. Axonal injury induces expression of the svh-2 gene encoding a receptor tyrosine kinase, stimulation of which by the SVH-1 growth factor leads to activation of the JNK pathway. Here, we identify ETS-4 and CEBP-1, related to mammalian Ets and C/EBP, respectively, as transcriptional activators of svh-2 expression following axon injury. ETS-4 and CEBP-1 function downstream of the cAMP and Ca2+-p38 MAPK pathways, respectively. We show that PKA-dependent phosphorylation of ETS-4 promotes its complex formation with CEBP-1. Furthermore, activation of both cAMP and Ca2+ signaling is required for activation of svh-2 expression. Thus, the cAMP/Ca2+ signaling pathways cooperatively activate the JNK pathway, which then promotes axon regeneration.

  3. Ultrastructural observation of effect of moderate hypothermia on axonal damage in an animal model of diffuse axonal injury

    Institute of Scientific and Technical Information of China (English)

    孙晓川; 唐文渊; 郑履平

    2002-01-01

    Objective: To investigate the effect of moderate hypothermia on responses of axonal cytoskeleton to axonal injury in the acute stage of injury. Methods: Of fifteen adult guinea pigs, twelve animals were subjected to stretch injury to the right optic nerves and divided into the normothermic group (n=6) in which the animal's core temperature was maintained at 36.0-37.5℃ and the hypothermia group (n=6) in which the core temperature was reduced to 32.0-32.5℃ after stretch injury. Remaining three animals sustained no injury to the right optic nerves and served as control group. Half of injured animals (n=3) of either normothermic group or hypothermic group were killed at either 2 hours or 4 hours after injury. The ultrastructural changes of axonal cytoskeleton of the right optic nerve fibers from the animals were examined under a transmission electron microscope and analyzed by quantitative analysis with a computer image analysis system. Results: At 2 hours after stretch injury, there was a significant reduction in the mean number of microtubules (P<0.001), and a significant increase in the mean intermicrotubule spacing (P<0.05 or P<0.01) in axons of all sizes in normothermic animals. The mean number of neurofilaments also decreased statistically (P<0.01) in large and medium subgroups of axons in the same experimental group at 2 hours. By 4 hours, the large subgroup of axons in normothermic animals still demonstrated a significant decline in the mean number of microtubules (P<0.01) and an increase in the mean intermicrotubule spacing (P<0.05), while the medium and small subgroups of axons displayed a significant increase in the mean number of neurofilaments (P<0.05) and reduction in the mean interneurofilament spacing (P<0.05). On the contrary, either the mean number of microtubules and the mean intermicrotubule spacing, or the mean number of neurofilaments and interneurofilament spacing in axons of all sizes in hypothermic stretch-injured animals was not

  4. Guidance of Nonlinear Systems

    Science.gov (United States)

    Meyer, George

    1997-01-01

    The paper describes a method for guiding a dynamic system through a given set of points. The paradigm is a fully automatic aircraft subject to air traffic control (ATC). The ATC provides a sequence of way points through which the aircraft trajectory must pass. The way points typically specify time, position, and velocity. The guidance problem is to synthesize a system state trajectory which satisfies both the ATC and aircraft constraints. Complications arise because the controlled process is multi-dimensional, multi-axis, nonlinear, highly coupled, and the state space is not flat. In addition, there is a multitude of possible operating modes, which may number in the hundreds. Each such mode defines a distinct state space model of the process by specifying the state space coordinatization, the partition of the controls into active controls and configuration controls, and the output map. Furthermore, mode transitions must be smooth. The guidance algorithm is based on the inversion of the pure feedback approximations, which is followed by iterative corrections for the effects of zero dynamics. The paper describes the structure and modules of the algorithm, and the performance is illustrated by several example aircraft maneuvers.

  5. Targeted GAS6 delivery to the CNS protects axons from damage during experimental autoimmune encephalomyelitis.

    Science.gov (United States)

    Gruber, Ross C; Ray, Alex K; Johndrow, Christopher T; Guzik, Hillary; Burek, Dominika; de Frutos, Pablo García; Shafit-Zagardo, Bridget

    2014-12-01

    Growth arrest-specific protein 6 (GAS6) is a soluble agonist of the TYRO3, AXL, MERTK (TAM) family of receptor tyrosine kinases identified to have anti-inflammatory, neuroprotective, and promyelinating properties. During experimental autoimmune encephalomyelitis (EAE), wild-type (WT) mice demonstrate a significant induction of Gas6, Axl, and Mertk but not Pros1 or Tyro3 mRNA. We tested the hypothesis that intracerebroventricular delivery of GAS6 directly into the CNS of WT mice during myelin oligodendrocyte glycoprotein (MOG)-induced EAE would improve the clinical course of disease relative to artificial CSF (ACSF)-treated mice. GAS6 did not delay disease onset, but significantly reduced the clinical scores during peak and chronic EAE. Mice receiving GAS6 for 28 d had preserved SMI31(+) neurofilament immunoreactivity, significantly fewer SMI32(+) axonal swellings and spheroids and less demyelination relative to ACSF-treated mice. Alternate-day subcutaneous IFNβ injection did not enhance GAS6 treatment effectiveness. Gas6(-/-) mice sensitized with MOG35-55 peptide exhibit higher clinical scores during late peak to early chronic disease, with significantly increased SMI32(+) axonal swellings and Iba1(+) microglia/macrophages, enhanced expression of several proinflammatory mRNA molecules, and decreased expression of early oligodendrocyte maturation markers relative to WT mouse spinal cords with scores for 8 consecutive days. During acute EAE, flow cytometry showed significantly more macrophages but not T-cell infiltrates in Gas6(-/-) spinal cords than WT spinal cords. Our data are consistent with GAS6 being protective during EAE by dampening the inflammatory response, thereby preserving axonal integrity and myelination. PMID:25471571

  6. Non-cable vehicle guidance

    Energy Technology Data Exchange (ETDEWEB)

    Daugela, G.C.; Willott, A.M.; Chopiuk, R.G.; Thornton, S.E.

    1988-06-01

    The purpose is to determine the most promising driverless mine vehicle guidance systems that are not dependent on buried cables, and to plan their development. The project is presented in two phases: a preliminary study and literature review to determine whether suitable technologies exist to justify further work; and an in-depth assessment and selection of technologies for vehicle guidance. A large number of guidance elements are involved in a completely automated vehicle. The technologies that hold the best potential for development of guidance systems for mine vehicles are ultrasonics, radar, lasers, dead reckoning, and guidance algorithms. The best approach to adaptation of these technologies is on a step by step basis. Guidance modules that are complete in themselves and are designed to be integrated with other modules can provide short term benefits. Two modules are selected for development: the dragline operations monitor and automated machine control for optimized mining (AMCOM). 99 refs., 20 figs., 40 tabs.

  7. Regulation of Microtubule Dynamics in Axon Regeneration: Insights from C. elegans [version 1; referees: 3 approved

    Directory of Open Access Journals (Sweden)

    Ngang Heok Tang

    2016-04-01

    Full Text Available The capacity of an axon to regenerate is regulated by its external environment and by cell-intrinsic factors. Studies in a variety of organisms suggest that alterations in axonal microtubule (MT dynamics have potent effects on axon regeneration. We review recent findings on the regulation of MT dynamics during axon regeneration, focusing on the nematode Caenorhabditis elegans. In C. elegans the dual leucine zipper kinase (DLK promotes axon regeneration, whereas the exchange factor for Arf6 (EFA-6 inhibits axon regeneration. Both DLK and EFA-6 respond to injury and control axon regeneration in part via MT dynamics. How the DLK and EFA-6 pathways are related is a topic of active investigation, as is the mechanism by which EFA-6 responds to axonal injury. We evaluate potential candidates, such as the MT affinity-regulating kinase PAR-1/MARK, in regulation of EFA-6 and axonal MT dynamics in regeneration.

  8. Developmental guidance of the retroflex tract at its bending point involves Robo1-Slit2-mediated floor plate repulsion.

    Science.gov (United States)

    Moreno-Bravo, Juan A; Martinez-Lopez, Jesus E; Madrigal, M Pilar; Kim, Minkyung; Mastick, Grant S; Lopez-Bendito, Guillermina; Martinez, Salvador; Puelles, Eduardo

    2016-01-01

    The retroflex tract contains medial habenula efferents that target the hindbrain interpeduncular complex and surrounding areas. This tract displays a singular course. Initially, habenular axons extend ventralwards in front of the pretectum until they reach the basal plate. Next, they avoid crossing the local floor plate, sharply changing course caudalwards (the retroflexion alluded by the tract name) and navigate strictly antero-posteriorly across basal pretectum, midbrain and isthmus. Once they reach rhombomere 1, the habenular axons criss-cross the floor plate several times within the interpeduncular nuclear complex as they innervate it. Here we described the timing and details of growth phenomena as these axons navigate to their target. The first dorsoventral course apparently obeys Ntn1 attraction. We checked the role of local floor plate signaling in the decision to avoid the thalamic floor plate and bend caudalwards. Analyzing the altered floor and basal plates of Gli2 knockout mice, we found a contralateral projection of most habenular axons, plus ulterior bizarre navigation rostralwards. This crossing phenotype was due to a reduced expression of Slit repulsive cues, suggesting involvement of the floor-derived Robo-Slit system in the normal guidance of this tract. Using Slit and Robo mutant mice, open neural tube and co-culture assays, we determined that Robo1-Slit2 interaction is specifically required for impeding that medial habenular axons cross the thalamic floor plate. This pathfinding mechanism is essential to establish the functionally important habenulo-interpeduncular connection.

  9. A novel technique using hydrophilic polymers to promote axonal fusion

    Institute of Scientific and Technical Information of China (English)

    Ravinder Bamba; D Colton Riley; Nathaniel D Kelm; Mark D Does; Richard D Dortch; Wesley P hTayer

    2016-01-01

    The management of traumatic peripheral nerve injury remains a considerable concern for clinicians. With minimal innovations in surgical technique and a limited number of specialists trained to treat peripheral nerve injury, outcomes of surgical intervention have been unpredictable. The inability to manipulate the pathophysiology of nerve injury (i.e., Wallerian degeneration) has left scientists and clinicians depending on the slow and lengthy process of axonal regeneration (~1 mm/day). When axons are severed, the endings undergo calcium-mediated plasmalemmal sealing, which limits the ability of the axon to be primarily re-paired. Polythethylene glycol (PEG) in combination with a bioengineered process overcomes the inability to fuse axons. The mechanism for PEG axonal fusion is not clearly understood, but multiple studies have shown that a providing a calcium-free environment is essential to the process known as PEG fusion. The proposed mechanism is PEG-induced lipid bilayer fusion by removing the hydration barrier surrounding the axolemma and reducing the activation energy required for membrane fusion to occur. This review highlights PEG fusion, its past and current studies, and future directions in PEG fusion.

  10. Subtypes of GABAergic neurons project axons in the neocortex

    Directory of Open Access Journals (Sweden)

    Shigeyoshi Higo

    2009-11-01

    Full Text Available γ-aminobutyric acid (GABAergic neurons in the neocortex have been regarded as interneurons and speculated to modulate the activity of neurons locally. Recently, however, several experiments revealed that neuronal nitric oxide synthase (nNOS-positive GABAergic neurons project cortico-cortically with long axons. In this study, we illustrate Golgi-like images of the nNOS-positive GABAergic neurons using a nicotinamide adenine dinucleotide phosphate diaphorase (NADPH-d reaction and follow the emanating axon branches in cat brain sections. These axon branches projected cortico-cortically with other non-labeled arcuate fibers, contra-laterally via the corpus callosum and anterior commissure. The labeled fibers were not limited to the neocortex but found also in the fimbria of the hippocampus. In order to have additional information on these GABAergic neuron projections, we investigated green fluorescent protein (GFP-labeled GABAergic neurons in GAD67-Cre knock-in / GFP Cre-reporter mice. GFP-labeled axons emanate densely, especially in the fimbria, a small number in the anterior commissure, and very sparsely in the corpus callosum. These two different approaches confirm that not only nNOS-positive GABAergic neurons but also other subtypes of GABAergic neurons project long axons in the cerebral cortex and are in a position to be involved in information processing.

  11. Functional complexity of the axonal growth cone: a proteomic analysis.

    Directory of Open Access Journals (Sweden)

    Adriana Estrada-Bernal

    Full Text Available The growth cone, the tip of the emerging neurite, plays a crucial role in establishing the wiring of the developing nervous system. We performed an extensive proteomic analysis of axonal growth cones isolated from the brains of fetal Sprague-Dawley rats. Approximately 2000 proteins were identified at ≥ 99% confidence level. Using informatics, including functional annotation cluster and KEGG pathway analysis, we found great diversity of proteins involved in axonal pathfinding, cytoskeletal remodeling, vesicular traffic and carbohydrate metabolism, as expected. We also found a large and complex array of proteins involved in translation, protein folding, posttranslational processing, and proteasome/ubiquitination-dependent degradation. Immunofluorescence studies performed on hippocampal neurons in culture confirmed the presence in the axonal growth cone of proteins representative of these processes. These analyses also provide evidence for rough endoplasmic reticulum and reveal a reticular structure equipped with Golgi-like functions in the axonal growth cone. Furthermore, Western blot revealed the growth cone enrichment, relative to fetal brain homogenate, of some of the proteins involved in protein synthesis, folding and catabolism. Our study provides a resource for further research and amplifies the relatively recently developed concept that the axonal growth cone is equipped with proteins capable of performing a highly diverse range of functions.

  12. Steerable-filter based quantification of axonal populations at the developing optic chiasm reveal significant defects in Slit2−/− as well as Slit1−/−Slit2−/− embryos

    Directory of Open Access Journals (Sweden)

    Down Matthew

    2013-01-01

    Full Text Available Abstract Background Previous studies have suggested that the axon guidance proteins Slit1 and Slit2 co-operate to establish the optic chiasm in its correct position at the ventral diencephalic midline. This is based on the observation that, although both Slit1 and Slit2 are expressed around the ventral midline, mice defective in either gene alone exhibit few or no axon guidance defects at the optic chiasm whereas embryos lacking both Slit1 and Slit2 develop a large additional chiasm anterior to the chiasm’s normal position. Here we used steerable-filters to quantify key properties of the population of axons at the chiasm in wild-type, Slit1−/−, Slit2−/− and Slit1−/−Slit2−/− embryos. Results We applied the steerable-filter algorithm successfully to images of embryonic retinal axons labelled from a single eye shortly after they have crossed the midline. We combined data from multiple embryos of the same genotype and made statistical comparisons of axonal distributions, orientations and curvatures between genotype groups. We compared data from the analysis of axons with data on the expression of Slit1 and Slit2. The results showed a misorientation and a corresponding anterior shift in the position of many axons at the chiasm of both Slit2−/− and Slit1−/−Slit2−/− mutants. There were very few axon defects at the chiasm of Slit1−/− mutants. Conclusions We found defects of the chiasms of Slit1−/−Slit2−/− and Slit1−/− mutants similar to those reported previously. In addition, we discovered previously unreported defects resulting from loss of Slit2 alone. This indicates the value of a quantitative approach to complex pathway analysis and shows that Slit2 can act alone to control aspects of retinal axon routing across the ventral diencephalic midline.

  13. Immunofluorescence laser confocal expression and localization study of rat nerve growth guidance cues Netrin-1 and Slit2 after spinal cord injury

    Institute of Scientific and Technical Information of China (English)

    LU Yao-jun; XU Nan-wei; YANG Wen-qiang

    2008-01-01

    To observe the expression and distribution of adult rat axon guidance cues Netrin-1 and Slit2 at different time points after spinal cord injury and to investigate the guidance mechanism of regenerated axons.Methods:Twenty adult Sprague Dawley(SD)rats were divided randomly into five groups with 4 in each.Four groups of them were used to make Allen's spinal cord punch models and we took materials randomly from one of them on the 2nd,4th,7th and 14th day respectively after operation.The left one group was taken as the control group.Immunofluorescence laser confocal scan was used to examine the co-expression and localization of Netrin-1 and Slit2 proteins in the injured site of the spinal cord.Results:Within two weeks after SCI,the expression of Netrin-1 and Slit2 proteins increased temporarily and there was co-expression of them on the neuron plasma membrane.Conclusions:Synchronous high expression and co-expression of axon attractant Netrin-1 and repellent Slit2 are found in the adult rat injured spinal cord in the damaged local and vicinity parts,and probably,they act as the key regulators of axon guidance regeneration.

  14. Neurofilament proteins in axonal regeneration and neurodegenerative diseases

    Institute of Scientific and Technical Information of China (English)

    Haitao Wang; Minfei Wu; Chuanjun Zhan; Enyuan Ma; Maoguang Yang; Xiaoyu Yang; Yingpu Li

    2012-01-01

    Neurofilament protein is a component of the mature neuronal cytoskeleton, and it interacts with the zygosome, which is mediated by neurofilament-related proteins. Neurofilament protein regulates enzyme function and the structure of linker proteins. In addition, neurofilament gene expression plays an important role in nervous system development. Previous studies have shown that neurofilament gene transcriptional regulation is crucial for neurofilament protein expression, especially in axonal regeneration and degenerative diseases. Post-transcriptional regulation increased neurofilament protein gene transcription during axonal regeneration, ultimately resulting in a pattern of neurofilament protein expression. An expression imbalance of post-transcriptional regulatory proteins and other disorders could lead to amyotrophic lateral sclerosis or other neurodegenerative diseases. These findings indicated that after transcription, neurofilament protein regulated expression of related proteins and promoted regeneration of damaged axons, suggesting that regulation disorders could lead to neurodegenerative diseases.

  15. Discussing Diverse Perspectives on Guidance

    Science.gov (United States)

    Gonzalez-Mena, Janet; Shareef, Intisar

    2005-01-01

    Ideas about discipline and guidance get extremely complex when they intersect with culture and oppression. Some groups of people who are targets of racism have to protect their children from the oppressive practices of racist individuals and institutions. Their methods of guidance and discipline may be different from those of groups for whom…

  16. Motoneuron axon pathfinding errors in zebrafish: Differential effects related to concentration and timing of nicotine exposure

    Energy Technology Data Exchange (ETDEWEB)

    Menelaou, Evdokia; Paul, Latoya T. [Department of Biological Sciences, Louisiana State University, Baton Rouge, LA 70803 (United States); Perera, Surangi N. [Joseph J. Zilber School of Public Health, University of Wisconsin — Milwaukee, Milwaukee, WI 53205 (United States); Svoboda, Kurt R., E-mail: svobodak@uwm.edu [Department of Biological Sciences, Louisiana State University, Baton Rouge, LA 70803 (United States); Joseph J. Zilber School of Public Health, University of Wisconsin — Milwaukee, Milwaukee, WI 53205 (United States)

    2015-04-01

    Nicotine exposure during embryonic stages of development can affect many neurodevelopmental processes. In the developing zebrafish, exposure to nicotine was reported to cause axonal pathfinding errors in the later born secondary motoneurons (SMNs). These alterations in SMN axon morphology coincided with muscle degeneration at high nicotine concentrations (15–30 μM). Previous work showed that the paralytic mutant zebrafish known as sofa potato exhibited nicotine-induced effects onto SMN axons at these high concentrations but in the absence of any muscle deficits, indicating that pathfinding errors could occur independent of muscle effects. In this study, we used varying concentrations of nicotine at different developmental windows of exposure to specifically isolate its effects onto subpopulations of motoneuron axons. We found that nicotine exposure can affect SMN axon morphology in a dose-dependent manner. At low concentrations of nicotine, SMN axons exhibited pathfinding errors, in the absence of any nicotine-induced muscle abnormalities. Moreover, the nicotine exposure paradigms used affected the 3 subpopulations of SMN axons differently, but the dorsal projecting SMN axons were primarily affected. We then identified morphologically distinct pathfinding errors that best described the nicotine-induced effects on dorsal projecting SMN axons. To test whether SMN pathfinding was potentially influenced by alterations in the early born primary motoneuron (PMN), we performed dual labeling studies, where both PMN and SMN axons were simultaneously labeled with antibodies. We show that only a subset of the SMN axon pathfinding errors coincided with abnormal PMN axonal targeting in nicotine-exposed zebrafish. We conclude that nicotine exposure can exert differential effects depending on the levels of nicotine and developmental exposure window. - Highlights: • Embryonic nicotine exposure can specifically affect secondary motoneuron axons in a dose-dependent manner.

  17. Guidance at the educational marketplace

    DEFF Research Database (Denmark)

    Lystbæk, Christian Tang

    in educational policies and institutions. As educational systems have expanded and, further, have been restructured with the expansion of choice opportunities since the 1980s, guidance has become prioritized as a form of counseling or coaching, which can support students. Thus, guidance has become an important...... institution of power in terms of choice opportunities and ´self-develoåment practices” in educational systems, the paper will discuss how the relationship between guidance and consumerism can be conceptualized in order to evaluate (and critically discuss) the consequences of the expansion of consumerism......The paper presents a conceptual framework for the relationship between guidance and consumerism, which can be applied in evaluating (and critically discussing) the consequences of this development for students, institutions and professionals. Guidance has moved from the margins to the center...

  18. Axon-glial interactions in the central nervous system

    OpenAIRE

    Butt, Arthur; Bay, Virginia

    2011-01-01

    Axon-glial interactions are critical for brain information transmission and processing. In the CNS, this is a function of the major types of glia – astrocytes, oligodendrocytes and novel NG2-glia. This special issue of the Journal of Anatomy comprises contributions arising from a symposium entitled ‘Axon-glial interactions in the CNS’, held at the University of Portsmouth, UK in July 2010. The aim of the special issue is to bring together an international group of experts to demonstrate the c...

  19. Giant Axonal Neuropathy Among Two Siblings - A Case Report

    Directory of Open Access Journals (Sweden)

    John Jhon. K

    2001-01-01

    Full Text Available Giant axonal neuropathy is a rate disorder with an autosomal recessive inheritance. It should be differentiated from toxic neuropathies, and hereditary degenerative disorders of nervous system like Friedreich′s ataxia and HMSN. Thick curly hair, though may not be present always is a useful clinical clue to identify cases. Prognosis is generally poor though course of the illness is variable. We report here a clinically and hisopathologically characteristic familial case of giant axonal neuropathy, which occurred in a 17-year-old boy, and his 21-year-old sister.

  20. RH Packaging Program Guidance

    Energy Technology Data Exchange (ETDEWEB)

    Washington TRU Solutions LLC

    2006-11-07

    The purpose of this program guidance document is to provide the technical requirements for use, operation, inspection, and maintenance of the RH-TRU 72-B Waste Shipping Package and directly related components. This document complies with the requirements as specified in the RH-TRU 72-B Safety Analysis Report for Packaging (SARP), and Nuclear Regulatory Commission (NRC) Certificate of Compliance (C of C) 9212. If there is a conflict between this document and the SARP and/or C of C, the C of C shall govern. The C of C states: "...each package must be prepared for shipment and operated in accordance with the procedures described in Chapter 7.0, Operating Procedures, of the application." It further states: "...each package must be tested and maintained in accordance with the procedures described in Chapter 8.0, Acceptance Tests and Maintenance Program of the Application." Chapter 9.0 of the SARP tasks the Waste Isolation Pilot Plant (WIPP) Management and Operating (M&O) Contractor with assuring the packaging is used in accordance with the requirements of the C of C. Because the packaging is NRC-approved, users need to be familiar with 10 Code of Federal Regulations (CFR) §71.8, "Deliberate Misconduct." Any time a user suspects or has indications that the conditions of approval in the C of C were not met, the U.S. Department of Energy (DOE) Carlsbad Field Office (CBFO) shall be notified immediately. CBFO will evaluate the issue and notify the NRC if required. In accordance with 10 CFR Part 71, "Packaging and Transportation of Radioactive Material," certificate holders, packaging users, and contractors or subcontractors who use, design, fabricate, test, maintain, or modify the packaging shall post copies of (1) 10 CFR Part 21, "Reporting of Defects and Noncompliance," regulations, (2) Section 206 of the Energy Reorganization Act of 1974, and (3) NRC Form 3, Notice to Employees. These documents must be posted in a conspicuous location where the activities subject to

  1. RH Packaging Program Guidance

    Energy Technology Data Exchange (ETDEWEB)

    Washington TRU Solutions LLC

    2008-01-12

    The purpose of this program guidance document is to provide the technical requirements for use, operation, inspection, and maintenance of the RH-TRU 72-B Waste Shipping Package (also known as the "RH-TRU 72-B cask") and directly related components. This document complies with the requirements as specified in the RH-TRU 72-B Safety Analysis Report for Packaging (SARP), and Nuclear Regulatory Commission (NRC) Certificate of Compliance (C of C) 9212. If there is a conflict between this document and the SARP and/or C of C, the C of C shall govern. The C of C states: "...each package must be prepared for shipment and operated in accordance with the procedures described in Chapter 7.0, Operating Procedures, of the application." It further states: "...each package must be tested and maintained in accordance with the procedures described in Chapter 8.0, Acceptance Tests and Maintenance Program of the Application." Chapter 9.0 of the SARP tasks the Waste Isolation Pilot Plant (WIPP) Management and Operating (M&O) Contractor with assuring the packaging is used in accordance with the requirements of the C of C. Because the packaging is NRC-approved, users need to be familiar with Title 10 Code of Federal Regulations (CFR) §71.8, "Deliberate Misconduct." Any time a user suspects or has indications that the conditions of approval in the C of C were not met, the U.S. Department of Energy (DOE) Carlsbad Field Office (CBFO) shall be notified immediately. The CBFO will evaluate the issue and notify the NRC if required.In accordance with 10 CFR Part 71, "Packaging and Transportation of Radioactive Material," certificate holders, packaging users, and contractors or subcontractors who use, design, fabricate, test, maintain, or modify the packaging shall post copies of (1) 10 CFR Part 21, "Reporting of Defects and Noncompliance," regulations, (2) Section 206 of the Energy Reorganization Act of 1974, and (3) NRC Form 3, Notice to Employees. These documents must be posted in a

  2. Networks of Polarized Actin Filaments in the Axon Initial Segment Provide a Mechanism for Sorting Axonal and Dendritic Proteins

    Directory of Open Access Journals (Sweden)

    Kaori Watanabe

    2012-12-01

    Full Text Available Trafficking of proteins specifically to the axonal or somatodendritic membrane allows neurons to establish and maintain polarized compartments with distinct morphology and function. Diverse evidence suggests that an actin-dependent vesicle filter within the axon initial segment (AIS plays a critical role in polarized trafficking; however, no distinctive actin-based structures capable of comprising such a filter have been found within the AIS. Here, using correlative light and scanning electron microscopy, we visualized networks of actin filaments several microns wide within the AIS of cortical neurons in culture. Individual filaments within these patches are predominantly oriented with their plus ends facing toward the cell body, consistent with models of filter selectivity. Vesicles carrying dendritic proteins are much more likely to stop in regions occupied by the actin patches than in other regions, indicating that the patches likely prevent movement of dendritic proteins to the axon and thereby act as a vesicle filter.

  3. Neuroinflammation triggered by β-glucan/dectin-1 signaling enables CNS axon regeneration.

    Science.gov (United States)

    Baldwin, Katherine T; Carbajal, Kevin S; Segal, Benjamin M; Giger, Roman J

    2015-02-24

    Innate immunity can facilitate nervous system regeneration, yet the underlying cellular and molecular mechanisms are not well understood. Here we show that intraocular injection of lipopolysaccharide (LPS), a bacterial cell wall component, or the fungal cell wall extract zymosan both lead to rapid and comparable intravitreal accumulation of blood-derived myeloid cells. However, when combined with retro-orbital optic nerve crush injury, lengthy growth of severed retinal ganglion cell (RGC) axons occurs only in zymosan-injected mice, and not in LPS-injected mice. In mice deficient for the pattern recognition receptor dectin-1 but not Toll-like receptor-2 (TLR2), zymosan-mediated RGC regeneration is greatly reduced. The combined loss of dectin-1 and TLR2 completely blocks the proregenerative effects of zymosan. In the retina, dectin-1 is expressed by microglia and dendritic cells, but not by RGCs. Dectin-1 is also present on blood-derived myeloid cells that accumulate in the vitreous. Intraocular injection of the dectin-1 ligand curdlan [a particulate form of β(1, 3)-glucan] promotes optic nerve regeneration comparable to zymosan in WT mice, but not in dectin-1(-/-) mice. Particulate β(1, 3)-glucan leads to increased Erk1/2 MAP-kinase signaling and cAMP response element-binding protein (CREB) activation in myeloid cells in vivo. Loss of the dectin-1 downstream effector caspase recruitment domain 9 (CARD9) blocks CREB activation and attenuates the axon-regenerative effects of β(1, 3)-glucan. Studies with dectin-1(-/-)/WT reciprocal bone marrow chimeric mice revealed a requirement for dectin-1 in both retina-resident immune cells and bone marrow-derived cells for β(1, 3)-glucan-elicited optic nerve regeneration. Collectively, these studies identify a molecular framework of how innate immunity enables repair of injured central nervous system neurons. PMID:25675510

  4. Membrane potential dynamics of axons in cultured hippocampal neurons probed by second-harmonic-generation imaging

    Science.gov (United States)

    Nuriya, Mutsuo; Yasui, Masato

    2010-03-01

    The electrical properties of axons critically influence the nature of communication between neurons. However, due to their small size, direct measurement of membrane potential dynamics in intact and complex mammalian axons has been a challenge. Furthermore, quantitative optical measurements of axonal membrane potential dynamics have not been available. To characterize the basic principles of somatic voltage signal propagation in intact axonal arbors, second-harmonic-generation (SHG) imaging is applied to cultured mouse hippocampal neurons. When FM4-64 is applied extracellularly to dissociated neurons, whole axonal arbors are visualized by SHG imaging. Upon action potential generation by somatic current injection, nonattenuating action potentials are recorded in intact axonal arbors. Interestingly, however, both current- and voltage-clamp recordings suggest that nonregenerative subthreshold somatic voltage changes at the soma are poorly conveyed to these axonal sites. These results reveal the nature of membrane potential dynamics of cultured hippocampal neurons, and further show the possibility of SHG imaging in physiological investigations of axons.

  5. Abnormal growth of the corticospinal axons into the lumbar spinal cord of the hyt/hyt mouse with congenital hypothyroidism.

    Science.gov (United States)

    Hsu, Jung-Yu C; Stein, Stuart A; Xu, Xiao-Ming

    2008-11-01

    Thyroid hormone deficiency may cause severe neurological disorders resulting from developmental deficits of the central nervous system. The mutant hyt/hyt mouse, characterized by fetal-onset, life-long hypothyroidism resulting from a point mutation of the thyroid-stimulating hormone receptor of the thyroid gland, displays a variety of abnormalities in motor behavior that are likely associated with dysfunctions of specific brain regions and a defective corticospinal tract (CST). To test the hypothesis that fetal and neonatal hypothyroidism cause abnormal CST development, the growth of the CST was investigated in hypothyroid hyt/hyt mice and their euthyroid progenitors, the BALB/cByJ mice. Anterograde labeling with biotinylated dextran amine demonstrated a decrease in the number of CST axons in the hyt/hyt mouse at the first lumbar level at postnatal day (P) 10. After retrograde tracing with fast blue (FB), fewer FB-labeled neurons were found in the motor cortex, the red nucleus, and the lateral vestibular nucleus of the hyt/hyt mouse. At the fourth lumbar level, the hyt/hyt mouse also showed smaller CST cross-sectional areas and significantly lower numbers of unmyelinated axons, myelinated axons, and growth cones within the CST during postnatal development. At P10, the hyt/hyt mouse demonstrated significantly lower immunoreactivity of embryonic neural cell adhesion molecule in the CST at the seventh cervical level, whereas the expression of growth-associated protein 43 remained unchanged. Our study demonstrated an abnormal development of the CST in the hyt/hyt mouse, manifested by reduced axon quantity and retarded growth pattern at the lumbar spinal cord. PMID:18543337

  6. Axon diameter and intra-axonal volume fraction of the corticospinal tract in idiopathic normal pressure hydrocephalus measured by q-space imaging.

    Directory of Open Access Journals (Sweden)

    Kouhei Kamiya

    Full Text Available PURPOSE: Previous studies suggest that compression and stretching of the corticospinal tract (CST potentially cause treatable gait disturbance in patients with idiopathic normal pressure hydrocephalus (iNPH. Measurement of axon diameter with diffusion MRI has recently been used to investigate microstructural alterations in neurological diseases. In this study, we investigated alterations in the axon diameter and intra-axonal fraction of the CST in iNPH by q-space imaging (QSI analysis. METHODS: Nineteen patients with iNPH and 10 age-matched controls were recruited. QSI data were obtained with a 3-T system by using a single-shot echo planar imaging sequence with the diffusion gradient applied parallel to the antero-posterior axis. By using a two-component low-q fit model, the root mean square displacements of intra-axonal space ( =  axon diameter and intra-axonal volume fraction of the CST were calculated at the levels of the internal capsule and body of the lateral ventricle, respectively. RESULTS: Wilcoxon's rank-sum test revealed a significant increase in CST intra-axonal volume fraction at the paraventricular level in patients (p<0.001, whereas no significant difference was observed in the axon diameter. At the level of the internal capsule, neither axon diameter nor intra-axonal volume fraction differed significantly between the two groups. CONCLUSION: Our results suggest that in patients with iNPH, the CST does not undergo irreversible axonal damage but is rather compressed and/or stretched owing to pressure from the enlarged ventricle. These analyses of axon diameter and intra-axonal fraction yield insights into microstructural alterations of the CST in iNPH.

  7. The axonal repellent Slit2 inhibits pericyte migration: potential implications in angiogenesis.

    Science.gov (United States)

    Guijarro-Muñoz, I; Cuesta, A M; Alvarez-Cienfuegos, A; Geng, J G; Alvarez-Vallina, L; Sanz, L

    2012-02-15

    The Slit family of secreted proteins acts through the Roundabout (Robo) receptors to repel axonal migration during central nervous system development. Emerging evidence shows that Slit/Robo interactions also play a role in angiogenesis. The effect of Robo signaling on endothelial cells has been shown to be context-dependent. However, the role of Slit/Robo in pericytes has been largely unexplored. The aim of this study was to determine the effect of Slit2 on primary human pericytes and to address the underlying mechanisms, including the receptors potentially implicated. We demonstrate that both Robo1 and Robo4 are expressed by human pericytes. In the presence of their ligand Slit2, spontaneous and PDGF-induced migration of pericytes was impaired. This antimigratory activity of Slit-2 correlated with the inhibition of actin-based protrusive structures. Interestingly, human pericyte interaction with immobilized Slit2 was inhibited in the presence of anti-Robo1 and anti-Robo4 blocking antibodies, suggesting the implication of both receptors. These results add new insights into the role of Slit proteins during the angiogenic process that relies on the directional migration not only of endothelial cells but also of pericytes.

  8. Differential Axonal Projection of Mitral and Tufted Cells in the Mouse Main Olfactory System

    Directory of Open Access Journals (Sweden)

    Shin Nagayama

    2010-09-01

    Full Text Available In the past decade, much has been elucidated regarding the functional organization of the axonal connection of olfactory sensory neurons to olfactory bulb (OB glomeruli. However, the manner in which projection neurons of the OB process odorant input and send this information to higher brain centers remains unclear. Here, we report long-range, large-scale tracing of the axonal projection patterns of OB neurons using two-photon microscopy. Tracer injection into a single glomerulus demonstrated widely distributed mitral/tufted cell axonal projections on the lateroventral surface of the mouse brain, including the anterior/posterior piriform cortex (PC and olfactory tubercle (OT. We noted two distinct groups of labeled axons: PC-orienting axons and OT-orienting axons. Each group occupied distinct parts of the lateral olfactory tract. PC-orienting axons projected axon collaterals to a wide area of the PC but only a few collaterals to the OT. OT-orienting axons densely projected axon collaterals primarily to the anterolateral OT (alOT. Different colored dye injections into the superficial and deep portions of the OB external plexiform layer revealed that the PC-orienting axon populations originated in presumed mitral cells and the OT-orienting axons in presumed tufted cells. These data suggest that although mitral and tufted cells receive similar odor signals from a shared glomerulus, they process the odor information in different ways and send their output to different higher brain centers via the PC and alOT.

  9. Spectrins in axonal cytoskeletons: Dynamics revealed by extensions and fluctuations

    Science.gov (United States)

    Lai, Lipeng; Cao, Jianshu

    2014-07-01

    The macroscopic properties, the properties of individual components, and how those components interact with each other are three important aspects of a composited structure. An understanding of the interplay between them is essential in the study of complex systems. Using axonal cytoskeleton as an example system, here we perform a theoretical study of slender structures that can be coarse-grained as a simple smooth three-dimensional curve. We first present a generic model for such systems based on the fundamental theorem of curves. We use this generic model to demonstrate the applicability of the well-known worm-like chain (WLC) model to the network level and investigate the situation when the system is stretched by strong forces (weakly bending limit). We specifically studied recent experimental observations that revealed the hitherto unknown periodic cytoskeleton structure of axons and measured the longitudinal fluctuations. Instead of focusing on single molecules, we apply analytical results from the WLC model to both single molecule and network levels and focus on the relations between extensions and fluctuations. We show how this approach introduces constraints to possible local dynamics of the spectrin tetramers in the axonal cytoskeleton and finally suggests simple but self-consistent dynamics of spectrins in which the spectrins in one spatial period of axons fluctuate in-sync.

  10. Life-or-death decisions upon axonal damage.

    Science.gov (United States)

    Roselli, Francesco; Caroni, Pico

    2012-02-01

    In this issue of Neuron, Hu et al. (2012) report that upon axonal damage, CHOP and XBP1 unfolded protein response pathways are not recruited equally and have opposite effects on neuronal survival. XBP1 pathway boosting may represent a valuable neuroprotective strategy.

  11. IFNgamma enhances microglial reactions to hippocampal axonal degeneration

    DEFF Research Database (Denmark)

    Jensen, M B; Hegelund, I V; Lomholt, N D;

    2000-01-01

    periods. Message for the immune cytokine interferon-gamma (IFNgamma) was undetectable, and glial reactivity to axonal lesions occurred as normal in IFNgamma-deficient mice. Microglial responses to lesion-induced neuronal injury were markedly enhanced in myelin basic protein promoter-driven transgenic mice...

  12. PTEN inhibition and axon regeneration and neural repair

    Institute of Scientific and Technical Information of China (English)

    Yosuke Ohtake; Umar Hayat; Shuxin Li

    2015-01-01

    The intrinsic growth ability of all the neurons declines during development although some may grow better than others. Numerous intracellular signaling proteins and transcription factors have been shown to regulate the intrinsic growth capacity in mature neurons. Among them, PI3 kinase/Akt pathway is important for controlling axon elongation. As a negative regulator of this pathway, the tumor suppressor phosphatase and tensin homolog (PTEN) appears critical to con-trol the regenerative ability of young and adult neurons. This review will focus on recent research progress in axon regeneration and neural repair by PTEN inhibition and therapeutic potential of blocking this phosphatase for neurological disorders. Inhibition of PTEN by deletion in con-ditional knockout mice, knockdown by short-hairpin RNA, or blockade by pharmacological approaches, including administration of selective PTEN antagonist peptides, stimulates various degrees of axon regrowth in juvenile or adult rodents with central nervous system injuries. Im-portantly, post-injury PTEN suppression could enhance axonal growth and functional recovery in adult central nervous system after injury.

  13. CAREER GUIDANCE EXPERIENCE ABROAD

    Directory of Open Access Journals (Sweden)

    Sergey N. Tolstoguzov

    2015-01-01

    Full Text Available The aim of this paper is to describe the experience of careeroriented activities carried out with students of schools in developed and developing countries. Career Guidance in Russia, despite the vast experience of its implementation, is experiencing serious difficulties. In this regard, it is important to take into account the international experience career-oriented activities, such as in the developed countries of North America and the European Union as well as in several Asian countries with rapidly growing economies and a large demographic potential, taking into account the best variants for the Russian education system. Methods. The experience of career-oriented work undertaken with pupils of the USA, Canada, Israel, France, UK, Germany, Denmark, Sweden, Japan, Singapore, China and India is shown on the basis of the comparative analysis of different publications and information sources. The author has made an attempt to generalize the principles of psycho-pedagogical and administrative assistance in professional self-determination of senior pupils abroad. Scientific novelty. The approaches to career-oriented activities in countries with different levels of economic development are compared for the first time. Some principles are revealed. Firstly, the higher the income level per capita in the country, the greater attention is given to vocational guidance. The politics in the developed countries is based on interests of the individual: children’s acquaintance with the world of professions begins already at younger school and the moment of definitive selfdetermination is postponed till the end of their senior stage of education; the possibility of direction change of professional preparation in case of detection of discrepancy of qualities of the pupil to originally selected profile is provided. Career-oriented activity in developing countries, on the contrary, is rigidly coordinated to requirements of economy and a labour market

  14. Response to work activity guidance

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This memorandum is concerning the request from the FY95 Platte-Kansas Rivers Ecosystem Work Activity Guidance for refuge managers to review the purposes of refuges...

  15. The recombination activation gene 1 (Rag1 is expressed in a subset of zebrafish olfactory neurons but is not essential for axon targeting or amino acid detection

    Directory of Open Access Journals (Sweden)

    Friedrich Rainer W

    2005-07-01

    Full Text Available Abstract Background Rag1 (Recombination activation gene-1 mediates genomic rearrangement and is essential for adaptive immunity in vertebrates. This gene is also expressed in the olfactory epithelium, but its function there is unknown. Results Using a transgenic zebrafish line and immunofluorescence, we show that Rag1 is expressed and translated in a subset of olfactory sensory neurons (OSNs. Neurons expressing GFP under the Rag1 promoter project their axons to the lateral region of the olfactory bulb only, and axons with the highest levels of GFP terminate in a single glomerular structure. A subset of GFP-expressing neurons contain Gαo, a marker for microvillous neurons. None of the GFP-positive neurons express Gαolf, Gαq or the olfactory marker protein OMP. Depletion of RAG1, by morpholino-mediated knockdown or mutation, did not affect axon targeting. Calcium imaging indicates that amino acids evoke chemotopically organized glomerular activity patterns in a Rag1 mutant. Conclusion Rag1 expression is restricted to a subpopulation of zebrafish olfactory neurons projecting to the lateral olfactory bulb. RAG1 catalytic activity is not essential for axon targeting, nor is it likely to be required for regulation of odorant receptor expression or the response of OSNs to amino acids.

  16. Outer Electrospun Polycaprolactone Shell Induces Massive Foreign Body Reaction and Impairs Axonal Regeneration through 3D Multichannel Chitosan Nerve Guides

    Directory of Open Access Journals (Sweden)

    Sven Duda

    2014-01-01

    Full Text Available We report on the performance of composite nerve grafts with an inner 3D multichannel porous chitosan core and an outer electrospun polycaprolactone shell. The inner chitosan core provided multiple guidance channels for regrowing axons. To analyze the in vivo properties of the bare chitosan cores, we separately implanted them into an epineural sheath. The effects of both graft types on structural and functional regeneration across a 10 mm rat sciatic nerve gap were compared to autologous nerve transplantation (ANT. The mechanical biomaterial properties and the immunological impact of the grafts were assessed with histological techniques before and after transplantation in vivo. Furthermore during a 13-week examination period functional tests and electrophysiological recordings were performed and supplemented by nerve morphometry. The sheathing of the chitosan core with a polycaprolactone shell induced massive foreign body reaction and impairment of nerve regeneration. Although the isolated novel chitosan core did allow regeneration of axons in a similar size distribution as the ANT, the ANT was superior in terms of functional regeneration. We conclude that an outer polycaprolactone shell should not be used for the purpose of bioartificial nerve grafting, while 3D multichannel porous chitosan cores could be candidate scaffolds for structured nerve grafts.

  17. Outer Electrospun Polycaprolactone Shell Induces Massive Foreign Body Reaction and Impairs Axonal Regeneration through 3D Multichannel Chitosan Nerve Guides

    Science.gov (United States)

    Behrens, Peter; Wienecke, Soenke; Chakradeo, Tanmay; Glasmacher, Birgit

    2014-01-01

    We report on the performance of composite nerve grafts with an inner 3D multichannel porous chitosan core and an outer electrospun polycaprolactone shell. The inner chitosan core provided multiple guidance channels for regrowing axons. To analyze the in vivo properties of the bare chitosan cores, we separately implanted them into an epineural sheath. The effects of both graft types on structural and functional regeneration across a 10 mm rat sciatic nerve gap were compared to autologous nerve transplantation (ANT). The mechanical biomaterial properties and the immunological impact of the grafts were assessed with histological techniques before and after transplantation in vivo. Furthermore during a 13-week examination period functional tests and electrophysiological recordings were performed and supplemented by nerve morphometry. The sheathing of the chitosan core with a polycaprolactone shell induced massive foreign body reaction and impairment of nerve regeneration. Although the isolated novel chitosan core did allow regeneration of axons in a similar size distribution as the ANT, the ANT was superior in terms of functional regeneration. We conclude that an outer polycaprolactone shell should not be used for the purpose of bioartificial nerve grafting, while 3D multichannel porous chitosan cores could be candidate scaffolds for structured nerve grafts. PMID:24818158

  18. Guidance Systems of Fighter Aircraft

    Directory of Open Access Journals (Sweden)

    K.N. Rajanikanth

    2005-07-01

    Full Text Available Mission performance of a fighter aircraft is crucial for survival and strike capabilities in todays' aerial warfare scenario. The guidance functions of such an aircraft play a vital role inmeeting the requirements and accomplishing the mission success. This paper presents the requirements of precision guidance for various missions of a fighter aircraft. The concept ofguidance system as a pilot-in-loop system is pivotal in understanding and designing such a system. Methodologies of designing such a system are described.

  19. Axonal regeneration and development of de novo axons from distal dendrites of adult feline commissural interneurons after a proximal axotomy

    DEFF Research Database (Denmark)

    Fenrich, Keith K; Skelton, Nicole; MacDermid, Victoria E;

    2007-01-01

    the soma or a very proximal dendrite. L-ALPs were devoid of MAP2a/b immunoreactivity. Some of these L-ALPs projected through the lesion and formed bouton-like swellings. These results suggest that proximally axotomized spinal interneurons have the potential to form new connections via de novo axons...

  20. White matter involvement after TBI: Clues to axon and myelin repair capacity.

    Science.gov (United States)

    Armstrong, Regina C; Mierzwa, Amanda J; Marion, Christina M; Sullivan, Genevieve M

    2016-01-01

    Impact-acceleration forces to the head cause traumatic brain injury (TBI) with damage in white matter tracts comprised of long axons traversing the brain. White matter injury after TBI involves both traumatic axonal injury (TAI) and myelin pathology that evolves throughout the post-injury time course. The axon response to initial mechanical forces and secondary insults follows the process of Wallerian degeneration, which initiates as a potentially reversible phase of intra-axonal damage and proceeds to an irreversible phase of axon fragmentation. Distal to sites of axon disconnection, myelin sheaths remain for prolonged periods, which may activate neuroinflammation and inhibit axon regeneration. In addition to TAI, TBI can cause demyelination of intact axons. These evolving features of axon and myelin pathology also represent opportunities for repair. In experimental TBI, demyelinated axons exhibit remyelination, which can serve to both protect axons and facilitate recovery of function. Myelin remodeling may also contribute to neuroplasticity. Efficient clearance of myelin debris is a potential target to attenuate the progression of chronic pathology. During the early phase of Wallerian degeneration, interventions that prevent the transition from reversible damage to axon disconnection warrant the highest priority, based on the poor regenerative capacity of axons in the CNS. Clinical evaluation of TBI will need to address the challenge of accurately detecting the extent and stage of axon damage. Distinguishing the complex white matter changes associated with axons and myelin is necessary for interpreting advanced neuroimaging approaches and for identifying a broader range of therapeutic opportunities to improve outcome after TBI. PMID:25697845

  1. IH activity is increased in populations of slow versus fast motor axons of the rat.

    Directory of Open Access Journals (Sweden)

    Chad eLorenz

    2014-09-01

    Full Text Available Much is known about the electrophysiological variation in motoneuron somata across different motor units. However comparatively less is known about electrophysiological variation in motor axons and how this could impact function or electrodiagnosis in healthy or diseased states. We performed nerve excitability testing on two groups of motor axons in Sprague-Dawley rats that are known to differ significantly in their chronic daily activity patterns and in the relative proportion of motor unit types: one group innervating the soleus (slow motor axons and the other group innervating the tibialis anterior (fast motor axons muscles. We found that slow motor axons have significantly larger accommodation compared to fast motor axons upon application of a 100 ms hyperpolarizing conditioning stimulus that is 40% of axon threshold (Z = 3.24, p = 0.001 or 20% of axon threshold (Z = 2.67, p = 0.008. Slow motor axons had larger accommodation to hyperpolarizing currents in the current-threshold measurement (-80% Z = 3.07, p = 0.002; -90% Z = 2.98, p = 0.003. In addition, we found that slow motor axons have a significantly smaller rheobase than fast motor axons (Z = -1.99, p = 0.047 accompanied by a lower threshold in stimulus-response curves. The results provide evidence that slow motor axons have greater activity of the hyperpolarization-activated inwardly rectifying cation conductance (IH than fast motor axons. It is possible that this difference between fast and slow axons is caused by an adaptation to their chronic differences in daily activity patterns, and that this adaptation might have a functional effect on the motor unit. Moreover, these findings indicate that slow and fast motor axons may react differently to pathological conditions.

  2. FMRP-Mediated Axonal Delivery of miR-181d Regulates Axon Elongation by Locally Targeting Map1b and Calm1

    Directory of Open Access Journals (Sweden)

    Bin Wang

    2015-12-01

    Full Text Available Subcellular targeting and local translation of mRNAs are critical for axon development. However, the precise local control of mRNA translation requires investigation. We report that the Fmr1-encoded protein, FMRP-mediated axonal delivery of miR-181d negatively regulates axon elongation by locally targeting the transcripts of MAP1B (Map1b and calmodulin (Calm1 in primary sensory neurons. miR-181d affected the local synthesis of MAP1B and calmodulin in axons. FMRP was associated with miR-181d, Map1b, and Calm1. Both FMRP deficiency in Fmr1I304N mice and Fmr1 knockdown impeded the axonal delivery of miR-181d, Map1b, and Calm1 and reduced the protein levels of MAP1B and calmodulin in axons. Furthermore, nerve growth factor (NGF induced Map1b and Calm1 release from FMRP and miR-181d-repressing granules, thereby promoting axon elongation. Both miR-181d overexpression and FMRP knockdown impaired NGF-induced axon elongation. Our study reveals a mechanism for the local regulation of translation by miR-181d and FMRP during axon development.

  3. Alterations of mitochondrial dynamics allow retrograde propagation of locally initiated axonal insults.

    Science.gov (United States)

    Lassus, Benjamin; Magifico, Sebastien; Pignon, Sandra; Belenguer, Pascale; Miquel, Marie-Christine; Peyrin, Jean-Michel

    2016-01-01

    In chronic neurodegenerative syndromes, neurons progressively die through a generalized retraction pattern triggering retrograde axonal degeneration toward the cell bodies, which molecular mechanisms remain elusive. Recent observations suggest that direct activation of pro-apoptotic signaling in axons triggers local degenerative events associated with early alteration of axonal mitochondrial dynamics. This raises the question of the role of mitochondrial dynamics on both axonal vulnerability stress and their implication in the spreading of damages toward unchallenged parts of the neuron. Here, using microfluidic chambers, we assessed the consequences of interfering with OPA1 and DRP1 proteins on axonal degeneration induced by local application of rotenone. We found that pharmacological inhibition of mitochondrial fission prevented axonal damage induced by rotenone, in low glucose conditions. While alteration of mitochondrial dynamics per se did not lead to spontaneous axonal degeneration, it dramatically enhanced axonal vulnerability to rotenone, which had no effect in normal glucose conditions, and promoted retrograde spreading of axonal degeneration toward the cell body. Altogether, our results suggest a mitochondrial priming effect in axons as a key process of axonal degeneration. In the context of neurodegenerative diseases, like Parkinson's and Alzheimer's, mitochondria fragmentation could hasten neuronal death and initiate spatial dispersion of locally induced degenerative events. PMID:27604820

  4. Changes in microtubule stability and density in myelin-deficient shiverer mouse CNS axons

    Science.gov (United States)

    Kirkpatrick, L. L.; Witt, A. S.; Payne, H. R.; Shine, H. D.; Brady, S. T.

    2001-01-01

    Altered axon-Schwann cell interactions in PNS myelin-deficient Trembler mice result in changed axonal transport rates, neurofilament and microtubule-associated protein phosphorylation, neurofilament density, and microtubule stability. To determine whether PNS and CNS myelination have equivalent effects on axons, neurofilaments, and microtubules in CNS, myelin-deficient shiverer axons were examined. The genetic defect in shiverer is a deletion in the myelin basic protein (MBP) gene, an essential component of CNS myelin. As a result, shiverer mice have little or no compact CNS myelin. Slow axonal transport rates in shiverer CNS axons were significantly increased, in contrast to the slowing in demyelinated PNS nerves. Even more striking were substantial changes in the composition and properties of microtubules in shiverer CNS axons. The density of axonal microtubules is increased, reflecting increased expression of tubulin in shiverer, and the stability of microtubules is drastically reduced in shiverer axons. Shiverer transgenic mice with two copies of a wild-type myelin basic protein transgene have an intermediate level of compact myelin, making it possible to determine whether the actual level of compact myelin is an important regulator of axonal microtubules. Both increased microtubule density and reduced microtubule stability were still observed in transgenic mouse nerves, indicating that signals beyond synaptogenesis and the mere presence of compact myelin are required for normal regulation of the axonal microtubule cytoskeleton.

  5. Hierarchical patterning of multifunctional conducting polymer nanoparticles as a bionic platform for topographic contact guidance.

    Science.gov (United States)

    Ho, Dominic; Zou, Jianli; Chen, Xianjue; Munshi, Alaa; Smith, Nicole M; Agarwal, Vipul; Hodgetts, Stuart I; Plant, Giles W; Bakker, Anthony J; Harvey, Alan R; Luzinov, Igor; Iyer, K Swaminathan

    2015-02-24

    The use of programmed electrical signals to influence biological events has been a widely accepted clinical methodology for neurostimulation. An optimal biocompatible platform for neural activation efficiently transfers electrical signals across the electrode-cell interface and also incorporates large-area neural guidance conduits. Inherently conducting polymers (ICPs) have emerged as frontrunners as soft biocompatible alternatives to traditionally used metal electrodes, which are highly invasive and elicit tissue damage over long-term implantation. However, fabrication techniques for the ICPs suffer a major bottleneck, which limits their usability and medical translation. Herein, we report that these limitations can be overcome using colloidal chemistry to fabricate multimodal conducting polymer nanoparticles. Furthermore, we demonstrate that these polymer nanoparticles can be precisely assembled into large-area linear conduits using surface chemistry. Finally, we validate that this platform can act as guidance conduits for neurostimulation, whereby the presence of electrical current induces remarkable dendritic axonal sprouting of cells.

  6. Regulation of neuronal axon specification by glia-neuron gap junctions in C. elegans

    Science.gov (United States)

    Meng, Lingfeng; Zhang, Albert; Jin, Yishi; Yan, Dong

    2016-01-01

    Axon specification is a critical step in neuronal development, and the function of glial cells in this process is not fully understood. Here, we show that C. elegans GLR glial cells regulate axon specification of their nearby GABAergic RME neurons through GLR-RME gap junctions. Disruption of GLR-RME gap junctions causes misaccumulation of axonal markers in non-axonal neurites of RME neurons and converts microtubules in those neurites to form an axon-like assembly. We further uncover that GLR-RME gap junctions regulate RME axon specification through activation of the CDK-5 pathway in a calcium-dependent manner, involving a calpain clp-4. Therefore, our study reveals the function of glia-neuron gap junctions in neuronal axon specification and shows that calcium originated from glial cells can regulate neuronal intracellular pathways through gap junctions. DOI: http://dx.doi.org/10.7554/eLife.19510.001 PMID:27767956

  7. Interplay between kinesin-1 and cortical dynein during axonal outgrowth and microtubule organization in Drosophila neurons.

    Science.gov (United States)

    del Castillo, Urko; Winding, Michael; Lu, Wen; Gelfand, Vladimir I

    2015-12-28

    In this study, we investigated how microtubule motors organize microtubules in Drosophila neurons. We showed that, during the initial stages of axon outgrowth, microtubules display mixed polarity and minus-end-out microtubules push the tip of the axon, consistent with kinesin-1 driving outgrowth by sliding antiparallel microtubules. At later stages, the microtubule orientation in the axon switches from mixed to uniform polarity with plus-end-out. Dynein knockdown prevents this rearrangement and results in microtubules of mixed orientation in axons and accumulation of microtubule minus-ends at axon tips. Microtubule reorganization requires recruitment of dynein to the actin cortex, as actin depolymerization phenocopies dynein depletion, and direct recruitment of dynein to the membrane bypasses the actin requirement. Our results show that cortical dynein slides 'minus-end-out' microtubules from the axon, generating uniform microtubule arrays. We speculate that differences in microtubule orientation between axons and dendrites could be dictated by differential activity of cortical dynein.

  8. Quality in career guidance: The Danish case

    DEFF Research Database (Denmark)

    Plant, Peter

    2011-01-01

    Quality assurance systems are introduced in career guidance to monitor, control and develop guidance interventions. The Danish case represents at centrally driven, top-down approach......Quality assurance systems are introduced in career guidance to monitor, control and develop guidance interventions. The Danish case represents at centrally driven, top-down approach...

  9. Diet and energy-sensing inputs affect TorC1-mediated axon misrouting but not TorC2-directed synapse growth in a Drosophila model of tuberous sclerosis.

    Directory of Open Access Journals (Sweden)

    Brian Dimitroff

    Full Text Available The Target of Rapamycin (TOR growth regulatory system is influenced by a number of different inputs, including growth factor signaling, nutrient availability, and cellular energy levels. While the effects of TOR on cell and organismal growth have been well characterized, this pathway also has profound effects on neural development and behavior. Hyperactivation of the TOR pathway by mutations in the upstream TOR inhibitors TSC1 (tuberous sclerosis complex 1 or TSC2 promotes benign tumors and neurological and behavioral deficits, a syndrome known as tuberous sclerosis (TS. In Drosophila, neuron-specific overexpression of Rheb, the direct downstream target inhibited by Tsc1/Tsc2, produced significant synapse overgrowth, axon misrouting, and phototaxis deficits. To understand how misregulation of Tor signaling affects neural and behavioral development, we examined the influence of growth factor, nutrient, and energy sensing inputs on these neurodevelopmental phenotypes. Neural expression of Pi3K, a principal mediator of growth factor inputs to Tor, caused synapse overgrowth similar to Rheb, but did not disrupt axon guidance or phototaxis. Dietary restriction rescued Rheb-mediated behavioral and axon guidance deficits, as did overexpression of AMPK, a component of the cellular energy sensing pathway, but neither was able to rescue synapse overgrowth. While axon guidance and behavioral phenotypes were affected by altering the function of a Tor complex 1 (TorC1 component, Raptor, or a TORC1 downstream element (S6k, synapse overgrowth was only suppressed by reducing the function of Tor complex 2 (TorC2 components (Rictor, Sin1. These findings demonstrate that different inputs to Tor signaling have distinct activities in nervous system development, and that Tor provides an important connection between nutrient-energy sensing systems and patterning of the nervous system.

  10. Axonal transport of cadmium in the olfactory nerve of the pike

    International Nuclear Information System (INIS)

    109Cd2+ was applied in the olfactory chambers of pikes (Esox lucius) and the dynamics of the axoplasmic flow of the metal was determined in the olfactory nerves by gamma spectrometry and autoradiography. The results showed that the 109Cd2+ is transported at a constant rate along the olfactory nerves. The profile of the 109Cd2+ in the nerves showed a wave front of transported metal followed by a saddle region. When the nasal chambers were washed 2 hr after application of the 109Cd2+ well-defined transport peaks for the metal were seen in the olfactory axons. The maximal velocity for the transport of 109Cd2+, which corresponds to the movement of the wave front, was 2.38±0.10 mm/hr (mean±S.E.) at the experimental temperature (10 deg. C). The average velocity for the transport of the 109Cd2+, which corresponds to the peak apex movement of the wave, was 2.18±0.05 mm/hr (mean ±S.E.) at 10 deg. C. The tranported 109Cd2+ was strongly accumulated in the anterior parts of the olfactory bulbs, whereas in other brain areas the levels of the metal remained low. Autoradiography of a pike exposed to 109Cd2+ via the water showed a strong labelling in the receptor-cell-containing olfactory rosettes, whereas other structures in the olfactory chambers were only weakly labelled. The accumulation and axonal transport in the olfactory neurons may be noxious and constitute an important component in the toxicology of cadmium in fish, and this may apply also to some other heavy metals. (author)

  11. Quantitative study of NPY-expressing GABAergic neurons and axons in rat spinal dorsal horn.

    Science.gov (United States)

    Polgár, Erika; Sardella, Thomas C P; Watanabe, Masahiko; Todd, Andrew J

    2011-04-15

    Between 25-40% of neurons in laminae I-III are GABAergic, and some of these express neuropeptide Y (NPY). We previously reported that NPY-immunoreactive axons form numerous synapses on lamina III projection neurons that possess the neurokinin 1 receptor (NK1r). The aims of this study were to determine the proportion of neurons and GABAergic boutons in this region that contain NPY, and to look for evidence that they selectively innervate different neuronal populations. We found that 4-6% of neurons in laminae I-III were NPY-immunoreactive and based on the proportions of neurons that are GABAergic, we estimate that NPY is expressed by 18% of inhibitory interneurons in laminae I-II and 9% of those in lamina III. GABAergic boutons were identified by the presence of the vesicular GABA transporter (VGAT) and NPY was found in 13-15% of VGAT-immunoreactive boutons in laminae I-II, and 5% of those in lamina III. For both the lamina III NK1r-immunoreactive projection neurons and protein kinase Cγ (PKCγ)-immunoreactive interneurons in lamina II, we found that around one-third of the VGAT boutons that contacted them were NPY-immunoreactive. However, based on differences in the sizes of these boutons and the strength of their NPY-immunoreactivity, we conclude that these originate from different populations of interneurons. Only 6% of VGAT boutons presynaptic to large lamina I projection neurons that lacked NK1rs contained NPY. These results show that NPY-containing neurons make up a considerable proportion of the inhibitory interneurons in laminae I-III, and that their axons preferentially target certain classes of dorsal horn neuron.

  12. Enrichment of GABARAP relative to LC3 in the axonal initial segments of neurons.

    Directory of Open Access Journals (Sweden)

    Masato Koike

    Full Text Available GABAA receptor-associated protein (GABARAP was initially identified as a protein that interacts with GABAA receptor. Although LC3 (microtubule-associated protein 1 light chain 3, a GABARAP homolog, has been localized in the dendrites and cell bodies of neurons under normal conditions, the subcellular distribution of GABARAP in neurons remains unclear. Subcellular fractionation indicated that endogenous GABARAP was localized to the microsome-enriched and synaptic vesicle-enriched fractions of mouse brain as GABARAP-I, an unlipidated form. To investigate the distribution of GABARAP in neurons, we generated GFP-GABARAP transgenic mice. Immunohistochemistry in these transgenic mice showed that positive signals for GFP-GABARAP were widely distributed in neurons in various brain regions, including the hippocampus and cerebellum. Interestingly, intense diffuse and/or fibrillary expression of GFP-GABARAP was detected along the axonal initial segments (AIS of hippocampal pyramidal neurons and cerebellar Purkinje cells, in addition to the cell bodies and dendrites of these neurons. In contrast, only slight amounts of LC3 were detected along the AIS of these neurons, while diffuse and/or fibrillary staining for LC3 was mainly detected in their cell bodies and dendrites. These results indicated that, compared with LC3, GABARAP is enriched in the AIS, in addition to the cell bodies and dendrites, of these hippocampal pyramidal neurons and cerebellar Purkinje cells.

  13. Antiretroviral Therapy-Associated Acute Motor and Sensory Axonal Neuropathy

    Directory of Open Access Journals (Sweden)

    Kimberly N. Capers

    2011-01-01

    Full Text Available Guillain-Barré syndrome (GBS has been reported in HIV-infected patients in association with the immune reconstitution syndrome whose symptoms can be mimicked by highly active antiretroviral therapy (HAART-mediated mitochondrial toxicity. We report a case of a 17-year-old, HIV-infected patient on HAART with a normal CD4 count and undetectable viral load, presenting with acute lower extremity weakness associated with lactatemia. Electromyography/nerve conduction studies revealed absent sensory potentials and decreased compound muscle action potentials, consistent with a diagnosis of acute motor and sensory axonal neuropathy. Lactatemia resolved following cessation of HAART; however, neurological deficits minimally improved over several months in spite of immune modulatory therapy. This case highlights the potential association between HAART, mitochondrial toxicity and acute axonal neuropathies in HIV-infected patients, distinct from the immune reconstitution syndrome.

  14. 78 FR 56752 - Interim Staff Guidance Specific Environmental Guidance for Integral Pressurized Water Reactors...

    Science.gov (United States)

    2013-09-13

    ... COMMISSION Interim Staff Guidance Specific Environmental Guidance for Integral Pressurized Water Reactors... and operate integral pressurized water reactors (iPWR). This guidance applies to environmental reviews... Environmental Guidance for iPWR Reviews.'' The purpose of this ISG is to clarify the NRC guidance...

  15. Estimating neuronal connectivity from axonal and dendritic density fields

    Directory of Open Access Journals (Sweden)

    Jaap evan Pelt

    2013-11-01

    Full Text Available Neurons innervate space by extending axonal and dendritic arborizations. When axons and dendrites come in close proximity of each other, synapses between neurons can be formed. Neurons vary greatly in their morphologies and synaptic connections with other neurons. The size and shape of the arborizations determine the way neurons innervate space. A neuron may therefore be characterized by the spatial distribution of its axonal and dendritic 'mass'. A population mean 'mass' density field of a particular neuron type can be obtained by averaging over the individual variations in neuron geometries. Connectivity in terms of candidate synaptic contacts between neurons can be determined directly on the basis of their arborizations but also indirectly on the basis of their density fields. To decide when a candidate synapse can be formed, we previously developed a criterion defining that axonal and dendritic line pieces should cross in 3D and have an orthogonal distance less than a threshold value. In this paper, we developed new methodology for applying this criterion to density fields. We show that estimates of the number of contacts between neuron pairs calculated from their density fields are fully consistent with the number of contacts calculated from the actual arborizations. However, the estimation of the connection probability and the expected number of contacts per connection cannot be calculated directly from density fields, because density fields do not carry anymore the correlative structure in the spatial distribution of synaptic contacts. Alternatively, these two connectivity measures can be estimated from the expected number of contacts by using empirical mapping functions. The neurons used for the validation studies were generated by our neuron simulator NETMORPH. An example is given of the estimation of average connectivity and Euclidean pre- and postsynaptic distance distributions in a network of neurons represented by their population

  16. Bazooka mediates secondary axon morphology in Drosophila brain lineages

    OpenAIRE

    Hartenstein Volker; Spindler Shana R

    2011-01-01

    Abstract In the Drosophila brain, neural lineages project bundled axon tracts into a central neuropile. Each lineage exhibits a stereotypical branching pattern and trajectory, which distinguish it from other lineages. In this study, we used a multilineage approach to explore the neural function of the Par-complex member Par3/Bazooka in vivo. Drosophila bazooka is expressed in post-mitotic neurons of the larval brain and localizes within neurons in a lineage-dependent manner. The fact that mul...

  17. Tau phosphorylation affects its axonal transport and degradation

    OpenAIRE

    Rodríguez-Martín, Teresa; Cuchillo-Ibáñez, Inmaculada; Noble, Wendy; Nyenya, Fanon; Anderton, Brian H; Hanger, Diane P.

    2013-01-01

    Phosphorylated forms of microtubule-associated protein tau accumulate in neurofibrillary tangles in Alzheimer's disease. To investigate the effects of specific phosphorylated tau residues on its function, wild type or phosphomutant tau was expressed in cells. Elevated tau phosphorylation decreased its microtubule binding and bundling, and increased the number of motile tau particles, without affecting axonal transport kinetics. In contrast, reducing tau phosphorylation enhanced the amount of ...

  18. Adult motor axons preferentially reinnervate predegenerated muscle nerve

    OpenAIRE

    M. Abdullah; O'Daly, A.; A Vyas; Rohde, C.; Brushart, T.M.

    2013-01-01

    Preferential motor reinnervation (PMR) is the tendency for motor axons regenerating after repair of mixed nerve to reinnervate muscle nerve and/or muscle rather than cutaneous nerve or skin. PMR may occur in response to the peripheral nerve pathway alone in juvenile rats (Brushart, 1993; Redett et al., 2005), yet the ability to identify and respond to specific pathway markers is reportedly lost in adults (Uschold et al., 2007). The experiments reported here evaluate the relative roles of path...

  19. Regeneración axonal posterior a lesiones traumáticas de médula espinal: Papel crítico de galectina-1

    Directory of Open Access Journals (Sweden)

    Héctor R Quintá

    2014-08-01

    Full Text Available Al producirse una lesión de médula espinal (LME, un sinnúmero de proteínas inhibidoras de la regeneración axonal ocupan el sitio de lesión en forma secuencial. La primer proteína en llegar al mismo se conoce como semaforina 3A (Sema3A, siendo además una de las más potentes por su acción de inhibir la regeneración axonal. A nivel mecanístico la unión de esta proteína al complejo-receptor neuronal neuropilin-1 (NRP-1/PlexinA4 evita que se produzca regeneración axonal. En este trabajo de revisión se discutirá la acción de galectin-1 (Gal-1, una proteína endógena de unión a glicanos, que selectivamente se une al complejo-receptor NRP-1/PlexinA4 de las neuronas lesionadas a través de un mecanismo dependiente de interacciones lectina-glicano, interrumpiendo la señalización generada por Sema3A y permitiendo de esta manera la regeneración axonal y recuperación locomotora luego de producirse la LME. Mientras ambas formas de Gal-1 (monomérica y dimérica contribuyen a la inactivación de la microglia, solo la forma dimérica de Gal-1 es capaz de unirse al complejo-receptor NRP-1/PlexinA4 y promover regeneración axonal. Por lo tanto, Gal-1 dimérica produce recuperación de las lesiones espinales interfiriendo en la señalización de Sema3A a través de la unión al complejo-receptor NRP-1/PlexinA4, sugiriendo el uso de esta lectina en su forma dimérica para el tratamiento de pacientes con LME.

  20. Axonal Transport Impairment in Chemotherapy-Induced Peripheral Neuropathy

    Directory of Open Access Journals (Sweden)

    Gabriella Nicolini

    2015-08-01

    Full Text Available Chemotherapy-Induced Peripheral Neuropathy (CIPN is a dose-limiting side effect of several antineoplastic drugs which significantly reduces patients’ quality of life. Although different molecular mechanisms have been investigated, CIPN pathobiology has not been clarified yet. It has largely been recognized that Dorsal Root Ganglia are the main targets of chemotherapy and that the longest nerves are the most damaged, together with fast axonal transport. Indeed, this bidirectional cargo-specific transport has a pivotal role in neuronal function and its impairment is involved in several neurodegenerative and neurodevelopmental diseases. Literature data demonstrate that, despite different mechanisms of action, all antineoplastic agents impair the axonal trafficking to some extent and the severity of the neuropathy correlates with the degree of damage on this bidirectional transport. In this paper, we will examine the effect of the main old and new chemotherapeutic drug categories on axonal transport, with the aim of clarifying their potential mechanisms of action, and, if possible, of identifying neuroprotective strategies, based on the knowledge of the alterations induced by each drugs.

  1. EEG functional connectivity, axon delays and white matter disease

    Science.gov (United States)

    Nunez, Paul L.; Srinivasan, Ramesh; Fields, R. Douglas

    2016-01-01

    Objective Both structural and functional brain connectivities are closely linked to white matter disease. We discuss several such links of potential interest to neurologists, neurosurgeons, radiologists, and non-clinical neuroscientists. Methods Treatment of brains as genuine complex systems suggests major emphasis on the multi-scale nature of brain connectivity and dynamic behavior. Cross-scale interactions of local, regional, and global networks are apparently responsible for much of EEG's oscillatory behaviors. Finite axon propagation speed, often assumed to be infinite in local network models, is central to our conceptual framework. Results Myelin controls axon speed, and the synchrony of impulse traffic between distant cortical regions appears to be critical for optimal mental performance and learning. Results Several experiments suggest that axon conduction speed is plastic, thereby altering the regional and global white matter connections that facilitate binding of remote local networks. Conclusions Combined EEG and high resolution EEG can provide distinct multi-scale estimates of functional connectivity in both healthy and diseased brains with measures like frequency and phase spectra, covariance, and coherence. Significance White matter disease may profoundly disrupt normal EEG coherence patterns, but currently these kinds of studies are rare in scientific labs and essentially missing from clinical environments. PMID:24815984

  2. Dysregulated axonal RNA translation in amyotrophic lateral sclerosis.

    Science.gov (United States)

    Yasuda, Kyota; Mili, Stavroula

    2016-09-01

    Amyotrophic lateral sclerosis (ALS) is an adult-onset motor neuron disease that has been associated with a diverse array of genetic changes. Prominent among these are mutations in RNA-binding proteins (RBPs) or repeat expansions that give rise to toxic RNA species. RBPs are additionally central components of pathologic aggregates that constitute a disease hallmark, suggesting that dysregulation of RNA metabolism underlies disease progression. In the context of neuronal physiology, transport of RNAs and localized RNA translation in axons are fundamental to neuronal survival and function. Several lines of evidence suggest that axonal RNA translation is a central process perturbed by various pathogenic events associated with ALS. Dysregulated translation of specific RNA groups could underlie feedback effects that connect and reinforce disease manifestations. Among such candidates are RNAs encoding proteins involved in the regulation of microtubule dynamics. Further understanding of axonally dysregulated RNA targets and of the feedback mechanisms they induce could provide useful therapeutic insights. WIREs RNA 2016, 7:589-603. doi: 10.1002/wrna.1352 For further resources related to this article, please visit the WIREs website. PMID:27038103

  3. Axon clinical chemistry analyzer evaluated according to ECCLS protocol.

    Science.gov (United States)

    Brenna, S; Prencipe, L

    1992-10-01

    We assessed the analytical performance of the Axon system (Bayer Diagnostici), according to the European Committee for Clinical Laboratory Standards guidelines, for assay of 12 analytes: cholesterol, creatinine, glucose, total protein, urea, uric acid, alkaline phosphatase, alpha-amylase, aspartate aminotransferase, creatine kinase, sodium, and potassium. The field evaluation lasted approximately 5 months and involved the collection of approximately 10,000 data points with the Axon. The following results were obtained: The highest CVs for controls and human sera at different concentration/activity values were 2.2% for within-run imprecision (n = 60; 3 days, pooled estimate) and 3.5% for the between-day imprecision (n = 20 days). Close correlation was found with results for patients' specimens assayed with comparative instruments (Hitachi 717 for substrates and enzymes, Beckman Synchron EL/E4A for electrolytes). No drift was observed during 8 h of operation. The linearity range was broad, sometimes exceeding the manufacturer's claims. No sample-, reagent-, or cuvette-related carryover was found. Measurement of control sera gave results within +/- 5% of the assigned values. We conclude that good reliability and practicability make the Axon system suitable for laboratories with various needs.

  4. Retinal glia promote dorsal root ganglion axon regeneration.

    Directory of Open Access Journals (Sweden)

    Barbara Lorber

    Full Text Available Axon regeneration in the adult central nervous system (CNS is limited by several factors including a lack of neurotrophic support. Recent studies have shown that glia from the adult rat CNS, specifically retinal astrocytes and Müller glia, can promote regeneration of retinal ganglion cell axons. In the present study we investigated whether retinal glia also exert a growth promoting effect outside the visual system. We found that retinal glial conditioned medium significantly enhanced neurite growth and branching of adult rat dorsal root ganglion neurons (DRG in culture. Furthermore, transplantation of retinal glia significantly enhanced regeneration of DRG axons past the dorsal root entry zone after root crush in adult rats. To identify the factors that mediate the growth promoting effects of retinal glia, mass spectrometric analysis of retinal glial conditioned medium was performed. Apolipoprotein E and secreted protein acidic and rich in cysteine (SPARC were found to be present in high abundance, a finding further confirmed by western blotting. Inhibition of Apolipoprotein E and SPARC significantly reduced the neuritogenic effects of retinal glial conditioned medium on DRG in culture, suggesting that Apolipoprotein E and SPARC are the major mediators of this regenerative response.

  5. Axonal Dysfunction Precedes Motor Neuronal Death in Amyotrophic Lateral Sclerosis.

    Directory of Open Access Journals (Sweden)

    Yuta Iwai

    Full Text Available Wide-spread fasciculations are a characteristic feature in amyotrophic lateral sclerosis (ALS, suggesting motor axonal hyperexcitability. Previous excitability studies have shown increased nodal persistent sodium conductances and decreased potassium currents in motor axons of ALS patients, both of the changes inducing hyperexcitability. Altered axonal excitability potentially contributes to motor neuron death in ALS, but the relationship of the extent of motor neuronal death and abnormal excitability has not been fully elucidated. We performed multiple nerve excitability measurements in the median nerve at the wrist of 140 ALS patients and analyzed the relationship of compound muscle action potential (CMAP amplitude (index of motor neuronal loss and excitability indices, such as strength-duration time constant, threshold electrotonus, recovery cycle and current-threshold relationships. Compared to age-matched normal controls (n = 44, ALS patients (n = 140 had longer strength-duration time constant (SDTC: a measure of nodal persistent sodium current; p 5mV. Regression analyses showed that SDTC (R = -0.22 and depolarizing threshold electrotonus (R = -0.22 increased with CMAP decline. These findings suggest that motor nerve hyperexcitability occurs in the early stage of the disease, and precedes motor neuronal loss in ALS. Modulation of altered ion channel function could be a treatment option for ALS.

  6. Axonal Dysfunction Precedes Motor Neuronal Death in Amyotrophic Lateral Sclerosis.

    Science.gov (United States)

    Iwai, Yuta; Shibuya, Kazumoto; Misawa, Sonoko; Sekiguchi, Yukari; Watanabe, Keisuke; Amino, Hiroshi; Kuwabara, Satoshi

    2016-01-01

    Wide-spread fasciculations are a characteristic feature in amyotrophic lateral sclerosis (ALS), suggesting motor axonal hyperexcitability. Previous excitability studies have shown increased nodal persistent sodium conductances and decreased potassium currents in motor axons of ALS patients, both of the changes inducing hyperexcitability. Altered axonal excitability potentially contributes to motor neuron death in ALS, but the relationship of the extent of motor neuronal death and abnormal excitability has not been fully elucidated. We performed multiple nerve excitability measurements in the median nerve at the wrist of 140 ALS patients and analyzed the relationship of compound muscle action potential (CMAP) amplitude (index of motor neuronal loss) and excitability indices, such as strength-duration time constant, threshold electrotonus, recovery cycle and current-threshold relationships. Compared to age-matched normal controls (n = 44), ALS patients (n = 140) had longer strength-duration time constant (SDTC: a measure of nodal persistent sodium current; p CMAP (> 5mV). Regression analyses showed that SDTC (R = -0.22) and depolarizing threshold electrotonus (R = -0.22) increased with CMAP decline. These findings suggest that motor nerve hyperexcitability occurs in the early stage of the disease, and precedes motor neuronal loss in ALS. Modulation of altered ion channel function could be a treatment option for ALS. PMID:27383069

  7. Sensory axon-derived neuregulin-1 is required for axoglial signaling and normal sensory function but not for long-term axon maintenance

    DEFF Research Database (Denmark)

    Fricker, F.R.; Zhu, N.; Tsantoulas, C.;

    2009-01-01

    " pockets. The total number of axons in the sural nerve was unchanged, but a greater proportion was unmyelinated. In addition, we observed large-diameter axons that were in a 1:1 relationship with Schwann cells, surrounded by a basal lamina but not myelinated. There was no evidence of DRG or Schwann cell...

  8. In vivo study of novel nanofibrous intra-luminal guidance channels to promote nerve regeneration

    Science.gov (United States)

    Koh, H. S.; Yong, T.; Teo, W. E.; Chan, C. K.; Puhaindran, M. E.; Tan, T. C.; Lim, A.; Lim, B. H.; Ramakrishna, S.

    2010-08-01

    A novel nanofibrous construct for promoting peripheral nerve repair was fabricated and tested in a rat sciatic nerve defect model. The conduit is made out of bilayered nanofibrous membranes with the nanofibers longitudinally aligned in the lumen and randomly oriented on the outer surface. The intra-luminal guidance channel is made out of aligned nanofibrous yarns. In addition, biomolecules such as laminin and nerve growth factor were incorporated in the nanofibrous nerve construct to determine their efficacy in in vivo nerve regeneration. Muscle reinnervation, withdrawal reflex latency, histological, axon density and electrophysiology tests were carried out to compare the efficacy of nanofibrous constructs with an autograft. Our study showed mixed results when comparing the artificial constructs with an autograft. In some cases, the nanofibrous conduit with aligned nanofibrous yarn as an intra-luminal guidance channel performs better than the autograft in muscle reinnervation and withdrawal reflex latency tests. However, the axon density count is highest in the autograft at mid-graft. Functional recovery was improved with the use of the nerve construct which suggested that this nerve implant has the potential for clinical usage in reconstructing peripheral nerve defects.

  9. Agent Based Individual Traffic guidance

    DEFF Research Database (Denmark)

    Wanscher, Jørgen Bundgaard

    2004-01-01

    can be obtained through cellular phone tracking or GPS systems. This information can then be used to provide individual traffic guidance as opposed to the mass information systems of today -- dynamic roadsigns and trafficradio. The goal is to achieve better usage of road and time. The main topic......When working with traffic planning or guidance it is common practice to view the vehicles as a combined mass. >From this models are employed to specify the vehicle supply and demand for each region. As the models are complex and the calculations are equally demanding the regions and the detail...

  10. Intra-axonal protein synthesis - a new target for neural repair?

    Institute of Scientific and Technical Information of China (English)

    Jeffery L Twiss; Ashley L Kalinski; Rahul Sachdeva; John D Houle

    2016-01-01

    Although initially argued to be a feature of immature neurons with incomplete polarization, there is clear evidence that neurons in the peripheral nervous system retain the capacity for intra-axonal protein synthe-sis well into adulthood. This localized protein synthesis has been shown to contribute to injury signaling and axon regeneration in peripheral nerves. Recent works point to potential for protein synthesis in axons of the vertebrate central nervous system. mRNAs and protein synthesis machinery have now been docu-mented in lamprey, mouse, and rat spinal cord axons. Intra-axonal protein synthesis appears to be activated in adult vertebrate spinal cord axons when they are regeneration-competent. Rat spinal cord axons regen-erating into a peripheral nerve graft contain mRNAs and markers of activated translational machinery. Indeed, levels of some growth-associated mRNAs in these spinal cord axons are comparable to the regen-erating sciatic nerve. Markers of active translation tend to decrease when these axons stop growing, but can be reactivated by a second axotomy. These emerging observations raise the possibility that mRNA transport into and translation within axons could be targeted to facilitate regeneration in both the peripheral and central nervous systems.

  11. Irregular geometries in normal unmyelinated axons: a 3D serial EM analysis.

    Science.gov (United States)

    Greenberg, M M; Leitao, C; Trogadis, J; Stevens, J K

    1990-12-01

    Axons have generally been represented as straight cylinders. It is not at all uncommon for anatomists to take single cross-sections of an axonal bundle, and from the axonal diameter compute expected conduction velocities. This assumes that each cross-section represents a slice through a perfect cylinder. We have examined the three-dimensional geometry of 98 central and peripheral unmyelinated axons, using computer-assisted serial electron microscopy. These reconstructions reveal that virtually all unmyelinated axons have highly irregular axial shapes consisting of periodic varicosities. The varicosities were, without exception, filled with membranous organelles frequently including mitochondria, and have obligatory volumes similar to that described in other neurites. The mitochondria make contact with microtubules, while the other membraneous organelles were frequently found free floating in the cytoplasm. We conclude that unmyelinated axons are fundamentally varicose structures created by the presence of organelles, and that an axon's calibre is dynamic in both space and time. These irregular axonal geometries raise serious doubts about standard two dimensional morphometric analysis and suggest that electrical properties may be more heterogeneous than expected from single section data. These results also suggest that the total number of microtubules contained in an axon, rather than its single section diameter, may prove to be a more accurate predictor of properties such as conduction velocity. Finally, these results offer an explanation for a number of pathological changes that have been described in unmyelinated axons. PMID:2292722

  12. Soluble axoplasm enriched from injured CNS axons reveals the early modulation of the actin cytoskeleton.

    Directory of Open Access Journals (Sweden)

    Patrick Garland

    Full Text Available Axon injury and degeneration is a common consequence of diverse neurological conditions including multiple sclerosis, traumatic brain injury and spinal cord injury. The molecular events underlying axon degeneration are poorly understood. We have developed a novel method to enrich for axoplasm from rodent optic nerve and characterised the early events in Wallerian degeneration using an unbiased proteomics screen. Our detergent-free method draws axoplasm into a dehydrated hydrogel of the polymer poly(2-hydroxyethyl methacrylate, which is then recovered using centrifugation. This technique is able to recover axonal proteins and significantly deplete glial contamination as confirmed by immunoblotting. We have used iTRAQ to compare axoplasm-enriched samples from naïve vs injured optic nerves, which has revealed a pronounced modulation of proteins associated with the actin cytoskeleton. To confirm the modulation of the actin cytoskeleton in injured axons we focused on the RhoA pathway. Western blotting revealed an augmentation of RhoA and phosphorylated cofilin in axoplasm-enriched samples from injured optic nerve. To investigate the localisation of these components of the RhoA pathway in injured axons we transected axons of primary hippocampal neurons in vitro. We observed an early modulation of filamentous actin with a concomitant redistribution of phosphorylated cofilin in injured axons. At later time-points, RhoA is found to accumulate in axonal swellings and also colocalises with filamentous actin. The actin cytoskeleton is a known sensor of cell viability across multiple eukaryotes, and our results suggest a similar role for the actin cytoskeleton following axon injury. In agreement with other reports, our data also highlights the role of the RhoA pathway in axon degeneration. These findings highlight a previously unexplored area of axon biology, which may open novel avenues to prevent axon degeneration. Our method for isolating CNS axoplasm

  13. Guidance for evidence-informed policies about health systems: rationale for and challenges of guidance development.

    Science.gov (United States)

    Bosch-Capblanch, Xavier; Lavis, John N; Lewin, Simon; Atun, Rifat; Røttingen, John-Arne; Dröschel, Daniel; Beck, Lise; Abalos, Edgardo; El-Jardali, Fadi; Gilson, Lucy; Oliver, Sandy; Wyss, Kaspar; Tugwell, Peter; Kulier, Regina; Pang, Tikki; Haines, Andy

    2012-01-01

    In the first paper in a three-part series on health systems guidance, Xavier Bosch-Capblanch and colleagues examine how guidance is currently formulated in low- and middle-income countries, and the challenges to developing such guidance.

  14. Evidence that the EphA2 receptor exacerbates ischemic brain injury.

    Directory of Open Access Journals (Sweden)

    John Thundyil

    Full Text Available Ephrin (Eph signaling within the central nervous system is known to modulate axon guidance, synaptic plasticity, and to promote long-term potentiation. We investigated the potential involvement of EphA2 receptors in ischemic stroke-induced brain inflammation in a mouse model of focal stroke. Cerebral ischemia was induced in male C57Bl6/J wild-type (WT and EphA2-deficient (EphA2(-/- mice by middle cerebral artery occlusion (MCAO; 60 min, followed by reperfusion (24 or 72 h. Brain infarction was measured using triphenyltetrazolium chloride staining. Neurological deficit scores and brain infarct volumes were significantly less in EphA2(-/- mice compared with WT controls. This protection by EphA2 deletion was associated with a comparative decrease in brain edema, blood-brain barrier damage, MMP-9 expression and leukocyte infiltration, and higher expression levels of the tight junction protein, zona occludens-1. Moreover, EphA2(-/- brains had significantly lower levels of the pro-apoptotic proteins, cleaved caspase-3 and BAX, and higher levels of the anti-apoptotic protein, Bcl-2 as compared to WT group. We confirmed that isolated WT cortical neurons express the EphA2 receptor and its ligands (ephrin-A1-A3. Furthermore, expression of all four proteins was increased in WT primary cortical neurons following 24 h of glucose deprivation, and in the brains of WT mice following stroke. Glucose deprivation induced less cell death in primary neurons from EphA2(-/- compared with WT mice. In conclusion, our data provide the first evidence that the EphA2 receptor directly contributes to blood-brain barrier damage and neuronal death following ischemic stroke.

  15. MeCP2 deficiency disrupts axonal guidance, fasciculation, and targeting by altering Semaphorin 3F function

    NARCIS (Netherlands)

    Degano, Alicia L.; Pasterkamp, R. Jeroen; Ronnett, Gabriele V.

    2009-01-01

    Rett syndrome (RTT) is an autism spectrum disorder that results from mutations in the transcriptional regulator methyl-CpG binding protein 2 (MECP2). In the present work, we demonstrate that MeCP2 deficiency disrupts the establishment of neural connections before synaptogenesis. Using both in vitro

  16. Teacher Guidance of Knowledge Construction

    Science.gov (United States)

    Schwarz, Baruch; Dreyfus, Tommy; Hadas, Nurit; Hershkowitz, Rina

    2004-01-01

    This paper focuses on how teachers guide construction of knowledge in classrooms. We suggest that guidance hinges on the kind of dialogue teachers choose to engage students in. We propose several classroom dialogue types relevant for the construction of knowledge and suggest that critical dialogue is particularly effective for knowledge…

  17. DOE Waste Treatability Group Guidance

    International Nuclear Information System (INIS)

    This guidance presents a method and definitions for aggregating U.S. Department of Energy (DOE) waste into streams and treatability groups based on characteristic parameters that influence waste management technology needs. Adaptable to all DOE waste types (i.e., radioactive waste, hazardous waste, mixed waste, sanitary waste), the guidance establishes categories and definitions that reflect variations within the radiological, matrix (e.g., bulk physical/chemical form), and regulated contaminant characteristics of DOE waste. Beginning at the waste container level, the guidance presents a logical approach to implementing the characteristic parameter categories as part of the basis for defining waste streams and as the sole basis for assigning streams to treatability groups. Implementation of this guidance at each DOE site will facilitate the development of technically defined, site-specific waste stream data sets to support waste management planning and reporting activities. Consistent implementation at all of the sites will enable aggregation of the site-specific waste stream data sets into comparable national data sets to support these activities at a DOE complex-wide level

  18. DOE Waste Treatability Group Guidance

    Energy Technology Data Exchange (ETDEWEB)

    Kirkpatrick, T.D.

    1995-01-01

    This guidance presents a method and definitions for aggregating U.S. Department of Energy (DOE) waste into streams and treatability groups based on characteristic parameters that influence waste management technology needs. Adaptable to all DOE waste types (i.e., radioactive waste, hazardous waste, mixed waste, sanitary waste), the guidance establishes categories and definitions that reflect variations within the radiological, matrix (e.g., bulk physical/chemical form), and regulated contaminant characteristics of DOE waste. Beginning at the waste container level, the guidance presents a logical approach to implementing the characteristic parameter categories as part of the basis for defining waste streams and as the sole basis for assigning streams to treatability groups. Implementation of this guidance at each DOE site will facilitate the development of technically defined, site-specific waste stream data sets to support waste management planning and reporting activities. Consistent implementation at all of the sites will enable aggregation of the site-specific waste stream data sets into comparable national data sets to support these activities at a DOE complex-wide level.

  19. Systematic policy and forward guidance

    OpenAIRE

    Plosser, Charles I.

    2014-01-01

    Money Marketeers of New York University, Inc., Down Town Association, March 25, 2014, New York, NY President Charles Plosser discusses the relationship between systematic policy and forward guidance. He explains how understanding both practices can provide insights into effective monetary policy in normal and unusual times, or in extreme conditions when policy is constrained by the zero lower bound on nominal interest rates.

  20. Transcriptomic and behavioural characterisation of a mouse model of burn pain identify the cholecystokinin 2 receptor as an analgesic target

    Science.gov (United States)

    Yin, Kathleen; Deuis, Jennifer R; Lewis, Richard J

    2016-01-01

    Burn injury is a cause of significant mortality and morbidity worldwide and is frequently associated with severe and long-lasting pain that remains difficult to manage throughout recovery. We characterised a mouse model of burn-induced pain using pharmacological and transcriptomic approaches. Mechanical allodynia elicited by burn injury was partially reversed by meloxicam (5 mg/kg), gabapentin (100 mg/kg) and oxycodone (3 and 10 mg/kg), while thermal allodynia and gait abnormalities were only significantly improved by amitriptyline (3 mg/kg) and oxycodone (10 mg/kg). The need for relatively high opioid doses to elicit analgesia suggested a degree of opioid resistance, similar to that shown clinically in burn patients. We thus assessed the gene expression changes in dorsal root ganglion neurons and pathophysiological mechanisms underpinning burn injury-induced pain using a transcriptomic approach. Burn injury was associated with significantly increased expression of genes associated with axon guidance, neuropeptide signalling, behavioural defence response and extracellular signalling, confirming a mixed neuropathic and inflammatory aetiology. Notably, among the pain-related genes that were upregulated post-injury was the cholecystokinin 2 receptor (Cckbr), a G protein-coupled receptor known as a pain target involved in reducing opioid effectiveness. Indeed, the clinically used cholecystokinin receptor antagonist proglumide (30 mg/kg) was effective at reversing mechanical allodynia, with additional analgesia evident in combination with low-dose oxycodone (1 mg/kg), including significant reversal of thermal allodynia. These findings highlight the complex pathophysiological mechanisms underpinning burn injury-induced pain and suggest that cholecystokinin-2 receptor antagonists may be useful clinically as adjuvants to decrease opioid requirements and improve analgesic management. PMID:27573516

  1. Transcriptomic and behavioural characterisation of a mouse model of burn pain identify the cholecystokinin 2 receptor as an analgesic target.

    Science.gov (United States)

    Yin, Kathleen; Deuis, Jennifer R; Lewis, Richard J; Vetter, Irina

    2016-01-01

    Burn injury is a cause of significant mortality and morbidity worldwide and is frequently associated with severe and long-lasting pain that remains difficult to manage throughout recovery. We characterised a mouse model of burn-induced pain using pharmacological and transcriptomic approaches. Mechanical allodynia elicited by burn injury was partially reversed by meloxicam (5 mg/kg), gabapentin (100 mg/kg) and oxycodone (3 and 10 mg/kg), while thermal allodynia and gait abnormalities were only significantly improved by amitriptyline (3 mg/kg) and oxycodone (10 mg/kg). The need for relatively high opioid doses to elicit analgesia suggested a degree of opioid resistance, similar to that shown clinically in burn patients. We thus assessed the gene expression changes in dorsal root ganglion neurons and pathophysiological mechanisms underpinning burn injury-induced pain using a transcriptomic approach. Burn injury was associated with significantly increased expression of genes associated with axon guidance, neuropeptide signalling, behavioural defence response and extracellular signalling, confirming a mixed neuropathic and inflammatory aetiology. Notably, among the pain-related genes that were upregulated post-injury was the cholecystokinin 2 receptor (Cckbr), a G protein-coupled receptor known as a pain target involved in reducing opioid effectiveness. Indeed, the clinically used cholecystokinin receptor antagonist proglumide (30 mg/kg) was effective at reversing mechanical allodynia, with additional analgesia evident in combination with low-dose oxycodone (1 mg/kg), including significant reversal of thermal allodynia. These findings highlight the complex pathophysiological mechanisms underpinning burn injury-induced pain and suggest that cholecystokinin-2 receptor antagonists may be useful clinically as adjuvants to decrease opioid requirements and improve analgesic management. PMID:27573516

  2. Coculture of elongated neuron axon with poly (D, L-lactide-co-glycolide) biomembrane in vitro

    Institute of Scientific and Technical Information of China (English)

    程飚; 陈峥嵘

    2004-01-01

    Objective: To elongate human nerve axon in culture and search for suitable support matrices for peripheral nervous system transplantation.Methods: Human embryo cortical neuronal cells,seeded on poly ( D, L-lactide-co-glycolide ) ( PLGA )membrane scaffolds, were elongated with a self-made neuro-axon extending device. The growth and morphological changes of neuron axons were observed to measure axolemmal permeability after elongation.Neurofilament protein was stained by immunohistochemical technique.Results: Human embryo neuron axon could be elongated and cultured on the PLGA membrane and retain their normal form and function.Conclusions: Three dimensional scaffolds with elongated neuron axon have the basic characteristics of artificial nerves, indicating a fundemental theory of nerve repair with elongated neuron axon.

  3. Disruption of Cnp1 uncouples oligodendroglial functions in axonal support and myelination.

    Science.gov (United States)

    Lappe-Siefke, Corinna; Goebbels, Sandra; Gravel, Michel; Nicksch, Eva; Lee, John; Braun, Peter E; Griffiths, Ian R; Nave, Klaus-Armin

    2003-03-01

    Myelination of axons by oligodendrocytes enables rapid impulse propagation in the central nervous system. But long-term interactions between axons and their myelin sheaths are poorly understood. Here we show that Cnp1, which encodes 2',3'-cyclic nucleotide phosphodiesterase in oligodendrocytes, is essential for axonal survival but not for myelin assembly. In the absence of glial cyclic nucleotide phosphodiesterase, mice developed axonal swellings and neurodegeneration throughout the brain, leading to hydrocephalus and premature death. But, in contrast to previously studied myelin mutants, the ultrastructure, periodicity and physical stability of myelin were not altered in these mice. Genetically, the chief function of glia in supporting axonal integrity can thus be completely uncoupled from its function in maintaining compact myelin. Oligodendrocyte dysfunction, such as that in multiple sclerosis lesions, may suffice to cause secondary axonal loss. PMID:12590258

  4. X11/Mint Genes Control Polarized Localization of Axonal Membrane Proteins in Vivo

    OpenAIRE

    Garrett G Gross; Lone, G. Mohiddin; Leung, Lok Kwan; Hartenstein, Volker; Guo, Ming

    2013-01-01

    Mislocalization of axonal proteins can result in misassembly and/or miswiring of neural circuits, causing disease. To date, only a handful of genes that control polarized localization of axonal membrane proteins have been identified. Here we report that Drosophila X11/Mint proteins are required for targeting several proteins, including human amyloid precursor protein (APP) and Drosophila APP-like protein (APPL), to axonal membranes and for their exclusion from dendrites of the mushroom body i...

  5. Directional specificity and patterning of sensory axons in trigeminal ganglion–whisker pad cocultures

    OpenAIRE

    Gunhan-Agar, Emine; Haeberle, Adam; Erzurumlu, Reha S.

    2000-01-01

    In the rodent trigeminal pathway, trigeminal axons invade the developing whisker pad from a caudal to rostral direction. We investigated directional specificity of embryonic day (E). 15 rat trigeminal axons within this peripheral target field using explant cocultures. E15 trigeminal axons readily grow into the same age whisker pad explants and form follicle-related patterns along a caudal to rostral direction. They also can grow into this target from its lateral aspects. In contrast, they are...

  6. Differential Effects of NGF and NT-3 on Embryonic Trigeminal Axon Growth Patterns

    OpenAIRE

    Ulupinar, Emel; Jacquin, Mark F.; Erzurumlu, Reha S.

    2000-01-01

    We examined the effects of neurotrophins nerve growth factor (NGF) and neurotrophin-3 (NT-3) on trigeminal axon growth patterns. Embryonic (E13–15) wholemount explants of the rat trigeminal pathway including the whisker pads, trigeminal ganglia, and brainstem were cultured in serum-free medium (SFM) or SFM supplemented with NGF or NT-3 for 3 days. Trigeminal axon growth patterns were analyzed with the use of lipophilic tracer DiI. In wholemount cultures grown in SFM, trigeminal axon projectio...

  7. N-Propionylmannosamine stimulates axonal elongation in a murine model of sciatic nerve injury

    Institute of Scientific and Technical Information of China (English)

    Christian Witzel; Werner Reutter; G Bjrn Stark; Georgios Koulaxouzidis

    2015-01-01

    Increasing evidence indicates that sialic acid plays an important role during nerve regeneration. Sialic acids can be modiifed in vitro as well as in vivo using metabolic oligosaccharide engineering of the N-acyl side chain. N-Propionylmannosamine (ManNProp) increases neurite outgrowth and accelerates the reestablishment of functional synapses in vitro. We investigated the inlfuence of systemic ManNProp application using a speciifc in vivo mouse model. Using mice expressing axonal lfuorescent proteins, we quantiifed the extension of regenerating axons, the number of regenerating axons, the number of arborising axons and the number of branches per axon 5 days after injury. Sciatic nerves from non-expressing mice were grafted into those expressing yellow lfuorescent protein. We began a twice-daily intraperitoneal application of either peracetylated ManNProp (200 mg/kg) or saline solution 5 days before injury, and continued it until nerve harvest (5 days after transection). ManNProp signiifcantly increased the mean distance of axonal regeneration (2.49 mm vs. 1.53 mm;P<0.005) and the number of arborizing axons (21%vs. 16%;P=0.008) 5 days after sciatic nerve grafting. ManNProp did not affect the number of regenerating axons or the number of branches per arborizing axon. The biochemical glycoen-gineering of the N-acyl side chain of sialic acid might be a promising approach for improving peripheral nerve regeneration.

  8. N-Propionylmannosamine stimulates axonal elongation in a murine model of sciatic nerve injury

    Directory of Open Access Journals (Sweden)

    Christian Witzel

    2015-01-01

    Full Text Available Increasing evidence indicates that sialic acid plays an important role during nerve regeneration. Sialic acids can be modified in vitro as well as in vivo using metabolic oligosaccharide engineering of the N-acyl side chain. N-Propionylmannosamine (ManNProp increases neurite outgrowth and accelerates the reestablishment of functional synapses in vitro. We investigated the influence of systemic ManNProp application using a specific in vivo mouse model. Using mice expressing axonal fluorescent proteins, we quantified the extension of regenerating axons, the number of regenerating axons, the number of arborising axons and the number of branches per axon 5 days after injury. Sciatic nerves from non-expressing mice were grafted into those expressing yellow fluorescent protein. We began a twice-daily intraperitoneal application of either peracetylated ManNProp (200 mg/kg or saline solution 5 days before injury, and continued it until nerve harvest (5 days after transection. ManNProp significantly increased the mean distance of axonal regeneration (2.49 mm vs. 1.53 mm; P < 0.005 and the number of arborizing axons (21% vs. 16% P = 0.008 5 days after sciatic nerve grafting. ManNProp did not affect the number of regenerating axons or the number of branches per arborizing axon. The biochemical glycoengineering of the N-acyl side chain of sialic acid might be a promising approach for improving peripheral nerve regeneration.

  9. NMNAT1 inhibits axon degeneration via blockade of SARM1-mediated NAD+ depletion

    Science.gov (United States)

    Sasaki, Yo; Nakagawa, Takashi; Mao, Xianrong; DiAntonio, Aaron; Milbrandt, Jeffrey

    2016-01-01

    Overexpression of the NAD+ biosynthetic enzyme NMNAT1 leads to preservation of injured axons. While increased NAD+ or decreased NMN levels are thought to be critical to this process, the mechanism(s) of this axon protection remain obscure. Using steady-state and flux analysis of NAD+ metabolites in healthy and injured mouse dorsal root ganglion axons, we find that rather than altering NAD+ synthesis, NMNAT1 instead blocks the injury-induced, SARM1-dependent NAD+ consumption that is central to axon degeneration. DOI: http://dx.doi.org/10.7554/eLife.19749.001 PMID:27735788

  10. Studying Axonal Regeneration by Laser Microsurgery and High-Resolution Videomicroscopy.

    Science.gov (United States)

    Xiao, Yan; López-Schier, Hernán

    2016-01-01

    Heterogeneous and unpredictable environmental insult, disease, or trauma can affect the integrity and function of neuronal circuits, leading to irreversible neural dysfunction. The peripheral nervous system can robustly regenerate axons after damage to recover the capacity to transmit sensory information to the brain. The mechanisms that allow axonal repair remain incompletely understood. Here we present a preparation in zebrafish that combines laser microsurgery of sensory axons and videomicroscopy of neurons in multicolor transgenic specimens. This simple protocol allows controlled damage of axons and dynamic high-resolution visualization and quantification of repair. PMID:27464814

  11. Engineering Guidance: A Human Resource Development.

    Science.gov (United States)

    Snarponis, Joseph M.; Prien, John D.

    1979-01-01

    Describes the role of The National Society of Professional Engineers (NSPE) in providing guidance activities for students. Discusses structional organization, goals, and guidance activities for engineering and technical and professional societies. (MA)

  12. Biomarker evidence of axonal injury in neuroasymptomatic HIV-1 patients.

    Directory of Open Access Journals (Sweden)

    Jan Jessen Krut

    Full Text Available Prevalence of neurocognitive impairment in HIV-1 infected patients is reported to be high. Whether this is a result of active HIV-related neurodegeneration is unclear. We examined axonal injury in HIV-1 patients by measuring the light subunit of neurofilament protein (NFL in CSF with a novel, sensitive method.With a cross-sectional design, CSF concentrations of neurofilament protein light (NFL (marker of neuronal injury, neopterin (intrathecal immunoactivation and CSF/Plasma albumin ratio (blood-brain barrier integrity were analyzed on CSF from 252 HIV-infected patients, subdivided into untreated neuroasymptomatics (n = 200, HIV-associated dementia (HAD (n = 14 and on combinations antiretroviral treatment (cART (n = 85, and healthy controls (n = 204. 46 HIV-infected patients were included in both treated and untreated groups, but sampled at different timepoints. Furthermore, 78 neuroasymptomatic patients were analyzed before and after treatment initiation.While HAD patients had the highest NFL concentrations, elevated CSF NFL was also found in 33% of untreated neuroasymptomatic patients, mainly in those with blood CD4+ cell counts below 250 cells/μL. CSF NFL concentrations in the untreated neuroasymptomatics and treated groups were equivalent to controls 18.5 and 3.9 years older, respectively. Neopterin correlated with NFL levels in untreated groups while the albumin ratio correlated with NFL in both untreated and treated groups.Increased CSF NFL indicates ongoing axonal injury in many neuroasymptomatic patients. Treatment decreases NFL, but treated patients retain higher levels than controls, indicating either continued virus-related injury or an aging-like effect of HIV infection. NFL correlates with neopterin and albumin ratio, suggesting an association between axonal injury, neuroinflammation and blood-brain barrier permeability. NFL appears to be a sensitive biomarker of subclinical and clinical brain injury in HIV and warrants further

  13. Excitability properties of motor axons in adults with cerebral palsy

    Directory of Open Access Journals (Sweden)

    Cliff S. Klein

    2015-06-01

    Full Text Available Cerebral Palsy (CP is a permanent disorder caused by a lesion to the developing brain that significantly impairs motor function. The neurophysiological mechanisms underlying motor impairment are not well understood. Specifically, few have addressed whether motoneuron or peripheral axon properties are altered in CP, even though disruption of descending inputs to the spinal cord may cause them to change. In the present study, we have compared nerve excitability properties in seven adults with CP and fourteen healthy controls using threshold tracking techniques by stimulating the median nerve at the wrist and recording the compound muscle action potential (CMAP over the abductor pollicis brevis. The excitability properties in the CP subjects were found to be abnormal. Early and late depolarizing and hyperpolarizing threshold electrotonus was significantly larger (i.e., fanning out, and resting current-threshold (I/V slope was smaller, in CP compared to control. In addition resting threshold and rheobase tended to be larger in CP. According to a modeling analysis of the data, an increase in leakage current under or through the myelin sheath, i.e., the Barrett-Barrett conductance (GBB, combined with a slight hyperpolarization of the resting membrane potential, best explained the group differences in excitability properties. There was a trend for those with greater impairment in gross motor function to have more abnormal axon properties. The findings indicate plasticity of motor axon properties far removed from the site of the lesion. We suspect that this plasticity is caused by disruption of descending inputs to the motoneurons at an early age around the time of their injury.

  14. Mechanisms of hyperpolarization in regenerated mature motor axons in cat

    DEFF Research Database (Denmark)

    Moldovan, Mihai; Krarup, Christian

    2004-01-01

    We found persistent abnormalities in the recovery of membrane excitability in long-term regenerated motor nerve fibres in the cat as indicated in the companion paper. These abnormalities could partly be explained by membrane hyperpolarization. To further investigate this possibility, we compared...... the changes in excitability in control nerves and long-term regenerated cat nerves (3-5 years after tibial nerve crush) during manoeuvres known to alter axonal membrane Na(+)-K(+) pump function: polarization, cooling to 20 degrees C, reperfusion after 10 min ischaemia, and up to 60 s of repetitive stimulation...

  15. Quality Assurance in University Guidance Services

    Science.gov (United States)

    Simon, Alexandra

    2014-01-01

    In Europe there is no common quality assurance framework for the delivery of guidance in higher education. Using a case study approach in four university career guidance services in England, France and Spain, this article aims to study how quality is implemented in university career guidance services in terms of strategy, standards and models,…

  16. Providing Career Guidance for Young Women.

    Science.gov (United States)

    Colby, Pamela G.

    This module is directed at personnel working or planning to work in the areas of guidance, counseling, placement and follow-through in junior and senior high school settings, grades 7-12. The module topic is career guidance for young women of junior and senior high school age, aand the focus will be on providing nonbiased career guidance which…

  17. The Self in Guidance: Assumptions and Challenges.

    Science.gov (United States)

    Edwards, Richard; Payne, John

    1997-01-01

    Examines the assumptions of "self" made in the professional and managerial discourses of guidance. Suggests that these assumptions obstruct the capacity of guidance workers to explain their own practices. Drawing on contemporary debates over identity, modernity, and postmodernity, argues for a more explicit debate about the self in guidance. (RJM)

  18. Guidance manual for constructed wetlands.

    OpenAIRE

    Ellis, John Bryan; Shutes, R. Brian E.; Revitt, D. Mike

    2003-01-01

    This Guidance Manual was produced to provide up to date information on the design, costs, construction, operation and maintenance of constructed wetlands used for the treatment of highway runoff. Information is provided on the different types of wetlands and their mode of operation, the design and planting of a wetland system and the retrofitting of treatment structures, the performance and costs of wetlands and their operation and maintenance requirements. The benefits of wetlands in encoura...

  19. Current materiality guidance for auditors

    OpenAIRE

    McKee, Thomas E.; Eilifsen, Aasmund

    2000-01-01

    Auditors have to make materiality judgments on every audit. This is a difficult process, as both quantitative and qualitative factors have to be evaluated. Additionally, there is no formal guidance for how to implement the materiality concepts discussed in the auditing standards. Although they are sometimes difficult to make, good materiality judgments are crucial for the conduct of a successful audit as poor judgments can result in an audit that is ineffective and/or inefficient. This report...

  20. Abnormal morphology of myelin and axon pathology in murine models of multiple sclerosis.

    Science.gov (United States)

    Bando, Yoshio; Nomura, Taichi; Bochimoto, Hiroki; Murakami, Koichi; Tanaka, Tatsuhide; Watanabe, Tsuyoshi; Yoshida, Shigetaka

    2015-02-01

    Demyelination and axonal damage are responsible for neurological deficits in multiple sclerosis (MS), an inflammatory demyelinating disease of the central nervous system. However, the pathology of axonal damage in MS is not fully understood. In this study, histological analysis of morphological changes of axonal organelles during demyelination in murine models was investigated by scanning electron microscopy (SEM) using an osmium-maceration method. In cuprizone-induced demyelination, SEM showed typical morphology of demyelination in the corpus callosum of mouse brain. In contrast, SEM displayed variations in ultrastructural abnormalities of myelin structures and axonal organelles in spinal cord white matter of experimental autoimmune encephalomyelitis (EAE) mice, an animal model of MS. Myelin detachment and excessive myelin formation were observed as typical morphological myelin abnormalities in EAE. In addition, well-developed axoplasmic reticulum-like structures and accumulated mitochondria were observed in tortuous degenerating/degenerated axons and the length of mitochondria in axons of EAE spinal cord was shorter compared with naïve spinal cord. Immunohistochemistry also revealed dysfunction of mitochondrial fusion/fission machinery in EAE spinal cord axons. Moreover, the number of Y-shaped mitochondria was significantly increased in axons of the EAE spinal cord. Axonal morphologies in myelin basic protein-deficient shiverer mice were similar to those in EAE. However, shiverer mice had "tortuous" (S-curve shaped mitochondria) and larger mitochondria compared with wild-type and EAE mice. Lastly, analysis of human MS patient autopsied brains also demonstrated abnormal myelin structures in demyelinating lesions. These results indicate that morphological abnormalities of myelin and axonal organelles play important role on the pathogenesis of axonal injury in demyelinating diseases.

  1. Bushen Yisui Capsule ameliorates axonal injury in experimental autoimmune encephalomyelitis

    Institute of Scientific and Technical Information of China (English)

    Ling Fang; Lei Wang; Qi Zheng; Tao Yang; Hui Zhao; Qiuxia Zhang; Kangning Li; Li Zhou; Haiyang Gong; Yongping Fan

    2013-01-01

    A preliminary clinical study by our group demonstrated Bushen Yisui Capsule (formerly cal ed Er-huang Formula) in combination with conventional therapy is an effective prescription for the treat-ment of multiple sclerosis. However, its effect on axonal injury during early multiple sclerosis re-mains unclear. In this study, a MOG 35-55-immunized C57BL/6 mouse model of experimental au-toimmune encephalomyelitis was intragastrical y administered Bushen Yisui Capsule. The results showed that Bushen Yisui Capsule effectively improved clinical symptoms and neurological function of experimental autoimmune encephalomyelitis. In addition, amyloid precursor protein expression was down-regulated and microtubule-associated protein 2 was up-regulated. Experimental findings indicate that the disease-preventive mechanism of Bushen Yisui Capsule in experimental autoim-mune encephalomyelitis was mediated by amelioration of axonal damage and promotion of rege-neration. But the effects of the high-dose Bushen Yisui Capsule group was not better than that of the medium-dose and low-dose Bushen Yisui Capsule group in preventing neurological dysfunction.

  2. An analysis of conductance changes in squid axon.

    Science.gov (United States)

    MULLINS, L J

    1959-05-20

    The membrane of the squid axon is considered on the basis of a pore model in which the distribution of the pore sizes strongly favors K(+) transfer when there is no potential. Electrical asymmetry causes non-penetrating ions on the membrane capacitor to exert a mechanical force on both membrane surfaces and this force results in a deformation of the membrane pore system such that it assumes a distribution of sizes favoring the ions exerting mechanical force. The ions involved appear to be Ca(++) on the outside of the membrane and isethionate(-), (i(-)) on the inside; as Ca(++) is equivalent in size to Na(+), the charged membrane is potentially able to transfer Na(+), when the ions deforming the membrane pore distribution are removed. A depolarization of the membrane leads to an opening of pores that will allow Na(+) penetration and a release of the membrane from deformation. The pores revert to the zero-potential pore size distribution hence the Na permeability change is a transient. Calculation shows that the potassium conductance vs. displacement of membrane potential curve for the squid axon and the "inactivation" function, h, can be obtained directly from the assumed membrane distortion without the introduction of arbitrary parameters. The sodium conductance, because it is a transient, requires assumptions about the time constants with which ions unblock pores at the outside and the inside of the membrane.

  3. An ex vivo laser-induced spinal cord injury model to assess mechanisms of axonal degeneration in real-time.

    Science.gov (United States)

    Okada, Starlyn L M; Stivers, Nicole S; Stys, Peter K; Stirling, David P

    2014-01-01

    Injured CNS axons fail to regenerate and often retract away from the injury site. Axons spared from the initial injury may later undergo secondary axonal degeneration. Lack of growth cone formation, regeneration, and loss of additional myelinated axonal projections within the spinal cord greatly limits neurological recovery following injury. To assess how central myelinated axons of the spinal cord respond to injury, we developed an ex vivo living spinal cord model utilizing transgenic mice that express yellow fluorescent protein in axons and a focal and highly reproducible laser-induced spinal cord injury to document the fate of axons and myelin (lipophilic fluorescent dye Nile Red) over time using two-photon excitation time-lapse microscopy. Dynamic processes such as acute axonal injury, axonal retraction, and myelin degeneration are best studied in real-time. However, the non-focal nature of contusion-based injuries and movement artifacts encountered during in vivo spinal cord imaging make differentiating primary and secondary axonal injury responses using high resolution microscopy challenging. The ex vivo spinal cord model described here mimics several aspects of clinically relevant contusion/compression-induced axonal pathologies including axonal swelling, spheroid formation, axonal transection, and peri-axonal swelling providing a useful model to study these dynamic processes in real-time. Major advantages of this model are excellent spatiotemporal resolution that allows differentiation between the primary insult that directly injures axons and secondary injury mechanisms; controlled infusion of reagents directly to the perfusate bathing the cord; precise alterations of the environmental milieu (e.g., calcium, sodium ions, known contributors to axonal injury, but near impossible to manipulate in vivo); and murine models also offer an advantage as they provide an opportunity to visualize and manipulate genetically identified cell populations and subcellular

  4. Optimum PN Guidance Law for Maneuvering Target

    Institute of Scientific and Technical Information of China (English)

    SUN Bao-cai; QI Zai-kang

    2007-01-01

    An optimum PN guidance law for maneuvering target is developed using optimal control theory. By estimating the target position and setting the cost function, the guidance law can be deduced even without knowing the missile lateral acceleration. Since the quadratic cost function can make a compromise between the miss distance andthe control constraint, the optimum guidance law obtained is more general. Also, introduced line of sight rate as the input, a practical form of this guidance law is derived. The simulation results show the effectiveness of the guidance laws.

  5. Serotonin axons of the neostriatum show a higher affinity for striatal than for ventral mesencephalic transplants: a quantitative study in adult and immature recipient rats.

    Science.gov (United States)

    Pierret, P; Vallée, A; Bosler, O; Dorais, M; Moukhles, H; Abbaszadeh, R; Lepage, Y; Doucet, G

    1998-07-01

    maintained, even though their growth capacity decreases irrespective of the target tissue considered. This experimental model may prove useful for the identification of the receptors and ligands that are responsible for target recognition by 5-HT axons and to test the possibility that the progressive decrease of axonal growth capacity from neonatal age to adulthood be related to a downregulation of such molecules.

  6. Inhibition of kinesin-5 improves regeneration of injured axons by a novel microtubule-based mechanism

    Institute of Scientific and Technical Information of China (English)

    Peter W. Baas; Andrew J. Matamoros

    2015-01-01

    Microtubules have been identiifed as a powerful target for augmenting regeneration of injured adult axons in the central nervous system. Drugs that stabilize microtubules have shown some promise, but there are concerns that abnormally stabilizing microtubules may have only limited beneifts for regeneration, while at the same time may be detrimental to the normal work that microtubules perform for the axon. Kinesin-5 (also called kif11 or Eg5), a molecular motor protein best known for its crucial role in mitosis, acts as a brake on microtubule movements by other motor proteins in the axon. Drugs that inhibit kinesin-5, originally developed to treat cancer, result in greater mobility of microtubules in the axon and an overall shift in the forces on the microtubule array. As a result, the axon grows faster, retracts less, and more readily enters environments that are inhibitory to axonal regeneration. Thus, drugs that inhibit kinesin-5 offer a novel microtubule-based means to boost axonal regeneration without the concerns that ac-company abnormal stabilization of the microtubule array. Even so, inhibiting kinesin-5 is not without its own caveats, such as potential problems with navigation of the regenerating axon to its target, as well as morphological effects on dendrites that could affect learning and memory if the drugs reach the brain.

  7. Axon-somatic back-propagation in detailed models of spinal alpha motoneurons

    Directory of Open Access Journals (Sweden)

    Pietro eBalbi

    2015-02-01

    Full Text Available Antidromic action potentials following distal stimulation of motor axons occasionally fail to invade the soma of alpha motoneurons in spinal cord, due to their passing through regions of high non-uniformity.Morphologically detailed conductance-based models of cat spinal alpha motoneurons have been developed, with the aim to reproduce and clarify some aspects of the electrophysiological behavior of the antidromic axon-somatic spike propagation. Fourteen 3D morphologically detailed somata and dendrites of cat spinal alpha motoneurons have been imported from an open-access web-based database of neuronal morphologies, NeuroMorpho.org, and instantiated in neurocomputational models. An axon hillock, an axonal initial segment and a myelinated axon are added to each model.By sweeping the diameter of the axonal initial segment (AIS and the axon hillock, as well as the maximal conductances of sodium channels at the AIS and at the soma, the developed models are able to show the relationships between different geometric and electrophysiological configurations and the voltage attenuation of the antidromically travelling wave.In particular, a greater than usually admitted sodium conductance at AIS is necessary and sufficient to overcome the dramatic voltage attenuation occurring during antidromic spike propagation both at the myelinated axon-AIS and at the AIS-soma transitions.

  8. The central role of mitochondria in axonal degeneration in multiple sclerosis.

    Science.gov (United States)

    Campbell, Graham R; Worrall, Joseph T; Mahad, Don J

    2014-12-01

    Neurodegeneration in multiple sclerosis (MS) is related to inflammation and demyelination. In acute MS lesions and experimental autoimmune encephalomyelitis focal immune attacks damage axons by injuring axonal mitochondria. In progressive MS, however, axonal damage occurs in chronically demyelinated regions, myelinated regions and also at the active edge of slowly expanding chronic lesions. How axonal energy failure occurs in progressive MS is incompletely understood. Recent studies show that oligodendrocytes supply lactate to myelinated axons as a metabolic substrate for mitochondria to generate ATP, a process which will be altered upon demyelination. In addition, a number of studies have identified mitochondrial abnormalities within neuronal cell bodies in progressive MS, leading to a deficiency of mitochondrial respiratory chain complexes or enzymes. Here, we summarise the mitochondrial abnormalities evident within neurons and discuss how these grey matter mitochondrial abnormalities may increase the vulnerability of axons to degeneration in progressive MS. Although neuronal mitochondrial abnormalities will culminate in axonal degeneration, understanding the different contributions of mitochondria to the degeneration of myelinated and demyelinated axons is an important step towards identifying potential therapeutic targets for progressive MS.

  9. C. elegans: a new model organism for studies of axon regeneration

    OpenAIRE

    Ghosh-Roy, Anindya; Chisholm, Andrew D.

    2010-01-01

    Axonal regeneration in C. elegans was first reported five years ago. Individual GFP-labeled axons can be severed using laser microsurgery and their regrowth followed in vivo. Several neuron types display robust regrowth after injury, including motor and sensory neurons. The small size and transparency of C. elegans make possible large-scale genetic and pharmacological screens for regeneration phenotypes.

  10. Distribution of neurofilaments in myelinated axons of the optic nerve of goldfish (Carassius auratus L.).

    Science.gov (United States)

    Matheson, D F; Diocee, M S; Roots, B I

    1980-11-01

    Neurofilaments were counted in myelinated axons of the optic nerve of goldfish which were acclimated to 5 degrees and 25 degrees C. The number of neurofilaments increases markedly with increasing axonal size; axons of less than 0.1 micrometer 2 in area contain between 25 and 60 neurofilaments, while in the larger axons of area greater than 1.0 micrometer 2 there are approximately 190. The densities of the neurofilaments in the small axons are noticeably higher than in the larger ones (507 and 160, respectively). A variety of fixation procedures i.e. osmium tetroxide (OsO4) in phosphate buffer, glutaraldehyde (4%) in phosphate buffer or in ethyleneglycol-bis-(beta-aminoethyl ether)-N,N'-tetraacetic acid (EGTA) and piperazine-N-N'-bis-(2-ethanesulphonic acid) (PIPES) and post-fixed with OsO4 had no effect on the numbers of neurofilaments relative to the size of axon. The anaesthetic MS-222 (tricaine methanesulphonate) likewise had no effect on the numbers of neurofilaments. It is proposed that temperature acclimation alters the axon diameter concomitant with an alteration in the number of neurofilaments to fit the new diameter of the axons. PMID:6253602

  11. N-docosahexaenoylethanolamine regulates Hedgehog signaling and promotes growth of cortical axons

    Directory of Open Access Journals (Sweden)

    Giorgi Kharebava

    2015-12-01

    Full Text Available Axonogenesis, a process for the establishment of neuron connectivity, is central to brain function. The role of metabolites derived from docosahexaenoic acid (DHA, 22:6n-3 that is specifically enriched in the brain, has not been addressed in axon development. In this study, we tested if synaptamide (N-docosahexaenoylethanolamine, an endogenous metabolite of DHA, affects axon growth in cultured cortical neurons. We found that synaptamide increased the average axon length, inhibited GLI family zinc finger 1 (GLI1 transcription and sonic hedgehog (Shh target gene expression while inducing cAMP elevation. Similar effects were produced by cyclopamine, a regulator of the Shh pathway. Conversely, Shh antagonized elevation of cAMP and blocked synaptamide-mediated increase in axon length. Activation of Shh pathway by a smoothened (SMO agonist (SAG or overexpression of SMO did not inhibit axon growth mediated by synaptamide or cyclopamine. Instead, adenylate cyclase inhibitor SQ22536 abolished synaptamide-mediated axon growth indicating requirement of cAMP elevation for this process. Our findings establish that synaptamide promotes axon growth while Shh antagonizes synaptamide-mediated cAMP elevation and axon growth by a SMO-independent, non-canonical pathway.

  12. Selective vulnerability and pruning of phasic motoneuron axons in motoneuron disease alleviated by CNTF.

    Science.gov (United States)

    Pun, San; Santos, Alexandre Ferrão; Saxena, Smita; Xu, Lan; Caroni, Pico

    2006-03-01

    Neurodegenerative diseases can have long preclinical phases and insidious progression patterns, but the mechanisms of disease progression are poorly understood. Because quantitative accounts of neuronal circuitry affected by disease have been lacking, it has remained unclear whether disease progression reflects processes of stochastic loss or temporally defined selective vulnerabilities of distinct synapses or axons. Here we derive a quantitative topographic map of muscle innervation in the hindlimb. We show that in two mouse models of motoneuron disease (G93A SOD1 and G85R SOD1), axons of fast-fatiguable motoneurons are affected synchronously, long before symptoms appear. Fast-fatigue-resistant motoneuron axons are affected at symptom-onset, whereas axons of slow motoneurons are resistant. Axonal vulnerability leads to synaptic vesicle stalling and accumulation of BC12a1-a, an anti-apoptotic protein. It is alleviated by ciliary neurotrophic factor and triggers proteasome-dependent pruning of peripheral axon branches. Thus, motoneuron disease involves predictable, selective vulnerability patterns by physiological subtypes of axons, episodes of abrupt pruning in the target region and compensation by resistant axons.

  13. CD8+ T cells cause disability and axon loss in a mouse model of multiple sclerosis.

    Directory of Open Access Journals (Sweden)

    Chandra Deb

    Full Text Available BACKGROUND: The objective of this study was to test the hypothesis that CD8+ T cells directly mediate motor disability and axon injury in the demyelinated central nervous system. We have previously observed that genetic deletion of the CD8+ T cell effector molecule perforin leads to preservation of motor function and preservation of spinal axons in chronically demyelinated mice. METHODOLOGY/PRINCIPAL FINDINGS: To determine if CD8+ T cells are necessary and sufficient to directly injure demyelinated axons, we adoptively transferred purified perforin-competent CD8+ spinal cord-infiltrating T cells into profoundly demyelinated but functionally preserved perforin-deficient host mice. Transfer of CD8+ spinal cord-infiltrating T cells rapidly and irreversibly impaired motor function, disrupted spinal cord motor conduction, and reduced the number of medium- and large-caliber spinal axons. Likewise, immunodepletion of CD8+ T cells from chronically demyelinated wildtype mice preserved motor function and limited axon loss without altering other disease parameters. CONCLUSIONS/SIGNIFICANCE: In multiple sclerosis patients, CD8+ T cells outnumber CD4+ T cells in active lesions and the number of CD8+ T cells correlates with the extent of ongoing axon injury and functional disability. Our findings suggest that CD8+ T cells may directly injure demyelinated axons and are therefore a viable therapeutic target to protect axons and motor function in patients with multiple sclerosis.

  14. A model of fasciculation and sorting in mixed populations of axons

    CERN Document Server

    Chaudhuri, Debasish; Zapotocky, Martin

    2010-01-01

    We extend a recently proposed model (Chaudhuri et al., EPL 87, 20003 (2009)), aiming to describe the formation of fascicles of axons during neural development. The growing axons are represented as paths of interacting directed random walkers in two spatial dimensions. To mimic turnover of axons, whole paths are removed and new walkers are injected with specified rates. In the simplest version of the model, we use strongly adhesive inter-axon interactions that are identical for all pairs of axons. We generalize the model to interactions of finite strengths and to multiple types of axons with type-specific interactions. The dynamic steady state is characterized by the position-dependent distribution of fascicle sizes. With distance in the direction of axon growth, the mean fascicle size and emergent time scales grow monotonically, while the degree of sorting of fascicles by axon type has a maximum at a finite distance. To understand the emergence of slow time scales, we develop an analytical framework to analyz...

  15. Fast and simplified mapping of mean axon diameter using temporal diffusion spectroscopy.

    Science.gov (United States)

    Xu, Junzhong; Li, Hua; Li, Ke; Harkins, Kevin D; Jiang, Xiaoyu; Xie, Jingping; Kang, Hakmook; Dortch, Richard D; Anderson, Adam W; Does, Mark D; Gore, John C

    2016-04-01

    Mapping axon diameter is of interest for the potential diagnosis and monitoring of various neuronal pathologies. Advanced diffusion-weighted MRI methods have been developed to measure mean axon diameters non-invasively, but suffer major drawbacks that prevent their direct translation into clinical practice, such as complex non-linear data fitting and, more importantly, long scanning times that are usually not tolerable for most human subjects. In the current study, temporal diffusion spectroscopy using oscillating diffusion gradients was used to measure mean axon diameters with high sensitivity to small axons in the central nervous system. Axon diameters have been found to be correlated with a novel metric, DDR⊥ (the rate of dispersion of the perpendicular diffusion coefficient with gradient frequency), which is a model-free quantity that does not require complex data analyses and can be obtained from two diffusion coefficient measurements in clinically relevant times with conventional MRI machines. A comprehensive investigation including computer simulations and animal experiments ex vivo showed that measurements of DDR⊥ agree closely with histological data. In humans in vivo, DDR⊥ was also found to correlate well with reported mean axon diameters in human corpus callosum, and the total scan time was only about 8 min. In conclusion, DDR⊥ may have potential to serve as a fast, simple and model-free approach to map the mean axon diameter of white matter in clinics for assessing axon diameter changes. PMID:27077155

  16. Blast overpressure induced axonal injury changes in rat brainstem and spinal cord

    Directory of Open Access Journals (Sweden)

    Srinivasu Kallakuri

    2015-01-01

    Full Text Available Introduction: Blast induced neurotrauma has been the signature wound in returning soldiers from the ongoing wars in Iraq and Afghanistan. Of importance is understanding the pathomechansim(s of blast overpressure (OP induced axonal injury. Although several recent animal models of blast injury indicate the neuronal and axonal injury in various brain regions, animal studies related to axonal injury in the white matter (WM tracts of cervical spinal cord are limited. Objective: The purpose of this study was to assess the extent of axonal injury in WM tracts of cervical spinal cord in male Sprague Dawley rats subjected to a single insult of blast OP. Materials and Methods: Sagittal brainstem sections and horizontal cervical spinal cord sections from blast and sham animals were stained by neurofilament light (NF-L chain and beta amyloid precursor protein immunocytochemistry and observed for axonal injury changes. Results: Observations from this preliminary study demonstrate axonal injury changes in the form of prominent swellings, retraction bulbs, and putative signs of membrane disruptions in the brainstem and cervical spinal cord WM tracts of rats subjected to blast OP. Conclusions: Prominent axonal injury changes following the blast OP exposure in brainstem and cervical spinal WM tracts underscores the need for careful evaluation of blast induced injury changes and associated symptoms. NF-L immunocytochemistry can be considered as an additional tool to assess the blast OP induced axonal injury.

  17. Transfer of vesicles from Schwann cell to axon: a novel mechanism of communication in the peripheral nervous system

    Directory of Open Access Journals (Sweden)

    María Alejandra eLopez-Verrilli

    2012-06-01

    Full Text Available Schwann cells (SCs are the glial component of the peripheral nervous system, with essential roles during development and maintenance of axons, as well as during regenerative processes after nerve injury. SCs increase conduction velocities by myelinating axons, regulate synaptic activity at presynaptic nerve terminals and are a source of trophic factors to neurons. Thus, development and maintenance of peripheral nerves are crucially dependent on local signalling between SCs and axons. In addition to the classic mechanisms of intercellular signalling, the possibility of communication through secreted vesicles has been poorly explored to date. Interesting recent findings suggest the occurrence of lateral transfer mediated by vesicles from glial cells to axons that could have important roles in axonal growth and axonal regeneration. Here, we review the role of vesicular transfer from SCs to axons and propose the benefits of this means in supporting neuronal and axonal maintenance and regeneration after nerve damage.

  18. The autophagy gene Wdr45/Wipi4 regulates learning and memory function and axonal homeostasis.

    Science.gov (United States)

    Zhao, Yan G; Sun, Le; Miao, Guangyan; Ji, Cuicui; Zhao, Hongyu; Sun, Huayu; Miao, Lin; Yoshii, Saori R; Mizushima, Noboru; Wang, Xiaoqun; Zhang, Hong

    2015-01-01

    WDR45/WIPI4, encoding a WD40 repeat-containing PtdIns(3)P binding protein, is essential for the basal autophagy pathway. Mutations in WDR45 cause the neurodegenerative disease β-propeller protein-associated neurodegeneration (BPAN), a subtype of NBIA. We generated CNS-specific Wdr45 knockout mice, which exhibit poor motor coordination, greatly impaired learning and memory, and extensive axon swelling with numerous axon spheroids. Autophagic flux is defective and SQSTM1 (sequestosome-1)/p62 and ubiquitin-positive protein aggregates accumulate in neurons and swollen axons. Nes-Wdr45(fl/Y) mice recapitulate some hallmarks of BPAN, including cognitive impairment and defective axonal homeostasis, providing a model for revealing the disease pathogenesis of BPAN and also for investigating the possible role of autophagy in axon maintenance.

  19. Serotonin spillover onto the axon initial segment of motoneurons induces central fatigue by inhibiting action potential initiation

    DEFF Research Database (Denmark)

    Cotel, Florence; Exley, Richard; Cragg, Stephanie;

    2013-01-01

    Motor fatigue induced by physical activity is an everyday experience characterized by a decreased capacity to generate motor force. Factors in both muscles and the central nervous system are involved. The central component of fatigue modulates the ability of motoneurons to activate muscle adequat......-HT during motor activity spills over from its release sites to the AIS of motoneurons. Here, activated 5-HT1A receptors inhibit firing and, thereby, muscle contraction. Hence, this is a cellular mechanism for central fatigue......Motor fatigue induced by physical activity is an everyday experience characterized by a decreased capacity to generate motor force. Factors in both muscles and the central nervous system are involved. The central component of fatigue modulates the ability of motoneurons to activate muscle......--as during motor exercise--activated 5-HT1A receptors that decreased motoneuronal excitability. Electrophysiological tests combined with pharmacology showed that focal activation of 5-HT1A receptors at the axon initial segment (AIS), but not on other motoneuronal compartments, inhibited the action potential...

  20. Matrix metalloproteinase 2 and membrane type 1 matrix metalloproteinase co-regulate axonal outgrowth of mouse retinal ganglion cells

    DEFF Research Database (Denmark)

    Gaublomme, Djoere; Buyens, Tom; De Groef, Lies;

    2014-01-01

    , we were able to show that broad-spectrum MMP inhibition reduces axon outgrowth of mouse retinal ganglion cells (RGCs), implicating MMPs as beneficial factors in axonal regeneration. Additional studies, using more specific MMP inhibitors and MMP-deficient mice, disclosed that both MMP-2 and MT1-MMP...... mouse retinal explants. Our data indicate MMP-2 and MT1-MMP as promising axonal outgrowth-promoting molecules and show a possible link between MMP-2 and β1-integrin in axon outgrowth....

  1. Interleukin (IL)-8 immunoreactivity of injured axons and surrounding oligodendrocytes in traumatic head injury.

    Science.gov (United States)

    Hayashi, Takahito; Ago, Kazutoshi; Nakamae, Takuma; Higo, Eri; Ogata, Mamoru

    2016-06-01

    Interleukin (IL)-8 has been suggested to be a positive regulator of myelination in the central nervous system, in addition to its principal role as a chemokine for neutrophils. Immunostaining for beta-amyloid precursor protein (AβPP) is an effective tool for detecting traumatic axonal injury, although AβPP immunoreactivity can also indicate axonal injury due to hypoxic causes. In this study, we examined IL-8 and AβPP immunoreactivity in sections of corpus callosum obtained from deceased patients with blunt head injury and from equivalent control tissue. AβPP immunoreactivity was detected in injured axons, such as axonal bulbs and varicose axons, in 24 of 44 head injury cases. These AβPP immunoreactive cases had survived for more than 3h. The AβPP immunostaining pattern can be classified into two types: traumatic (Pattern 1) and non-traumatic (Pattern 2) axonal injuries, which we described previously [Hayashi et al. Int. J. Legal Med. 129 (2015) 1085-1090]. Three of 44 control cases also showed AβPP immunoreactive injured axons as Pattern 2. In contrast, IL-8 immunoreactivity was detected in 7 AβPP immunoreactive and in 2 non-AβPP immunoreactive head injury cases, but was not detected in any of the 44 control cases, including the 3 AβPP immunoreactive control cases. The IL-8 immunoreactive cases had survived from 3 to 24 days, whereas those cases who survived less than 3 days (n=29) and who survived 90 days (n=1) were not IL-8 immunoreactive. Moreover, IL-8 was detected as Pattern 1 axons only. In addition, double immunofluorescence analysis showed that IL-8 is expressed by oligodendrocytes surrounding injured axons. In conclusion, our results suggest that immunohistochemical detection of IL-8 may be useful as a complementary diagnostic marker of traumatic axonal injury.

  2. Guidance on accidents involving radioactivity

    International Nuclear Information System (INIS)

    This annex contains advice to Health Authorities on their response to accidents involving radioactivity. The guidance is in six parts:-(1) planning the response required to nuclear accidents overseas, (2) planning the response required to UK nuclear accidents a) emergency plans for nuclear installations b) nuclear powered satellites, (3) the handling of casualties contaminated with radioactive substances, (4) background information for dealing with queries from the public in the event of an accident, (5) the national arrangements for incident involving radioactivity (NAIR), (6) administrative arrangements. (author)

  3. Dynamic Changes in Local Protein Synthetic Machinery in Regenerating Central Nervous System Axons after Spinal Cord Injury

    Science.gov (United States)

    Sachdeva, Rahul; Farrell, Kaitlin; McMullen, Mary-Katharine; Twiss, Jeffery L.; Houle, John D.

    2016-01-01

    Intra-axonal localization of mRNAs and protein synthesis machinery (PSM) endows neurons with the capacity to generate proteins locally, allowing precise spatiotemporal regulation of the axonal response to extracellular stimuli. A number of studies suggest that this local translation is a promising target to enhance the regenerative capacity of damaged axons. Using a model of central nervous system (CNS) axons regenerating into intraspinal peripheral nerve grafts (PNGs) we established that adult regenerating CNS axons contain several different mRNAs and protein synthetic machinery (PSM) components in vivo. After lower thoracic level spinal cord transection, ascending sensory axons regenerate into intraspinal PNGs but axon growth is stalled when they reach the distal end of the PNG (3 versus 7 weeks after grafting, resp.). By immunofluorescence with optical sectioning of axons by confocal microscopy, the total and phosphorylated forms of PSMs are significantly lower in stalled compared with actively regenerating axons. Reinjury of these stalled axons increased axonal localization of the PSM proteins, indicative of possible priming for a subcellular response to axotomy. These results suggest that axons downregulate protein synthetic capacity as they cease growing, yet they retain the ability to upregulate PSM after a second injury.

  4. Regional node-like membrane specializations in non-myelinated axons of rat retinal nerve fiber layer.

    Science.gov (United States)

    Hildebrand, C; Waxman, S G

    1983-01-01

    The axons in the nerve fiber layer (NFL) of the adult rat retina were examined by transmission electron microscopy. NFL axons range in size from 0.12 to about 2.0 microm, with a peak at 0.3-0.4 microm. In addition to conventional small mitochondria in the NFL axons contain some large ones, which are similar to astrocytic gliosomes. Two types of regional axon membrane specialization are found in the NFL. One of these represents portions of the initial axon segments of retinal ganglion cells. Apart from features typical for initial axon segments in general, a corona of lamelliform, villous or blunt glial processes is always present. The glial processes originate from MUller cells. The other regional axon membrane specialization consists of patches of an electron-dense subaxolemmal undercoating with associated tufts of Miller cell processes. These patches cover a varying but always limited proportion of the axon circumference and their longitudinal extent varies between 0.5 and 5.0 microm. They are clearly distinct from the initial axon segment and from the initial heminode in the optic nerve. Similar undercoated patches in the optic disc axons are apposed by astrocytic processes. It is concluded that rat NFL axons represent an example of central non-myelinated axons with distinct regional membrane specializations, which have some structural characteristics in common with nodes of Ranvier. PMID:24010160

  5. Serotonin spillover onto the axon initial segment of motoneurons induces central fatigue by inhibiting action potential initiation

    Science.gov (United States)

    Cotel, Florence; Exley, Richard; Cragg, Stephanie J.; Perrier, Jean-François

    2013-01-01

    Motor fatigue induced by physical activity is an everyday experience characterized by a decreased capacity to generate motor force. Factors in both muscles and the central nervous system are involved. The central component of fatigue modulates the ability of motoneurons to activate muscle adequately independently of the muscle physiology. Indirect evidence indicates that central fatigue is caused by serotonin (5-HT), but the cellular mechanisms are unknown. In a slice preparation from the spinal cord of the adult turtle, we found that prolonged stimulation of the raphe-spinal pathway—as during motor exercise—activated 5-HT1A receptors that decreased motoneuronal excitability. Electrophysiological tests combined with pharmacology showed that focal activation of 5-HT1A receptors at the axon initial segment (AIS), but not on other motoneuronal compartments, inhibited the action potential initiation by modulating a Na+ current. Immunohistochemical staining against 5-HT revealed a high-density innervation of 5-HT terminals on the somatodendritic membrane and a complete absence on the AIS. This observation raised the hypothesis that a 5-HT spillover activates receptors at this latter compartment. We tested it by measuring the level of extracellular 5-HT with cyclic voltammetry and found that prolonged stimulations of the raphe-spinal pathway increased the level of 5-HT to a concentration sufficient to activate 5-HT1A receptors. Together our results demonstrate that prolonged release of 5-HT during motor activity spills over from its release sites to the AIS of motoneurons. Here, activated 5-HT1A receptors inhibit firing and, thereby, muscle contraction. Hence, this is a cellular mechanism for central fatigue. PMID:23487756

  6. Neural signal registration and analysis of axons grown in microchannels

    Science.gov (United States)

    Pigareva, Y.; Malishev, E.; Gladkov, A.; Kolpakov, V.; Bukatin, A.; Mukhina, I.; Kazantsev, V.; Pimashkin, A.

    2016-08-01

    Registration of neuronal bioelectrical signals remains one of the main physical tools to study fundamental mechanisms of signal processing in the brain. Neurons generate spiking patterns which propagate through complex map of neural network connectivity. Extracellular recording of isolated axons grown in microchannels provides amplification of the signal for detailed study of spike propagation. In this study we used neuronal hippocampal cultures grown in microfluidic devices combined with microelectrode arrays to investigate a changes of electrical activity during neural network development. We found that after 5 days in vitro after culture plating the spiking activity appears first in microchannels and on the next 2-3 days appears on the electrodes of overall neural network. We conclude that such approach provides a convenient method to study neural signal processing and functional structure development on a single cell and network level of the neuronal culture.

  7. Diagnosis and treatment of diffuse axonal injury in 169 patients

    Institute of Scientific and Technical Information of China (English)

    YANG Jia-yong; YANG Zhen-jiu; FENG Cheng-xuan; LI Hong-wei; LI Wei-ping; ZHANG Jun; ZHANG Hong

    2005-01-01

    Objective: To evaluate current diagnosis and therapeutic effect and outcome of diffuse axonal injury (DAI) in 169 patients.Methods: The data of 169 DAI patients treated in the Second, Sixth, Eighth and Ninth Hospitals of Shenzhen and Shekou Hospital from January 2001 to January 2005 were collected. The imaging features, classification, GCS (Glasgow coma scale), treatment and outcome of the 169patients were retrospectively analyzed.Results: The simpler the imaging features, the closer the focus of DAI to the periphery of hemisphere and the higher the GCS score, the better the prognoses of DAI patients will be.Conclusions: The prognoses of DAI patients are closely related to the imaging features and classification,GCS and clinical treatment.

  8. Multimodal transition and stochastic antiresonance in squid giant axons

    CERN Document Server

    Borkowski, L S

    2010-01-01

    The experimental data of N. Takahashi, Y. Hanyu, T. Musha, R. Kubo, and G. Matsumoto, Physica D \\textbf{43}, 318 (1990), on the response of squid giant axons stimulated by periodic sequence of short current pulses is interpreted within the Hodgkin-Huxley model. The minimum of the firing rate as a function of the stimulus amplitude $I_0$ in the high-frequency regime is due to the multimodal transition. Below this singular point only odd multiples of the driving period remain and the system is highly sensitive to noise. The coefficient of variation has a maximum and the firing rate has a minimum as a function of the noise intensity which is an indication of the stochastic coherence antiresonance. The model calculations reproduce the frequency of occurrence of the most common modes in the vicinity of the transition. A linear relation of output frequency vs. $I_0$ for above the transition is also confirmed.

  9. Video Object Tracking in Neural Axons with Fluorescence Microscopy Images

    Directory of Open Access Journals (Sweden)

    Liang Yuan

    2014-01-01

    tracking. In this paper, we describe two automated tracking methods for analyzing neurofilament movement based on two different techniques: constrained particle filtering and tracking-by-detection. First, we introduce the constrained particle filtering approach. In this approach, the orientation and position of a particle are constrained by the axon’s shape such that fewer particles are necessary for tracking neurofilament movement than object tracking techniques based on generic particle filtering. Secondly, a tracking-by-detection approach to neurofilament tracking is presented. For this approach, the axon is decomposed into blocks, and the blocks encompassing the moving neurofilaments are detected by graph labeling using Markov random field. Finally, we compare two tracking methods by performing tracking experiments on real time-lapse image sequences of neurofilament movement, and the experimental results show that both methods demonstrate good performance in comparison with the existing approaches, and the tracking accuracy of the tracing-by-detection approach is slightly better between the two.

  10. The Role of Rab Proteins in Neuronal Cells and in the Trafficking of Neurotrophin Receptors

    Directory of Open Access Journals (Sweden)

    Cecilia Bucci

    2014-10-01

    Full Text Available Neurotrophins are a family of proteins that are important for neuronal development, neuronal survival and neuronal functions. Neurotrophins exert their role by binding to their receptors, the Trk family of receptor tyrosine kinases (TrkA, TrkB, and TrkC and p75NTR, a member of the tumor necrosis factor (TNF receptor superfamily. Binding of neurotrophins to receptors triggers a complex series of signal transduction events, which are able to induce neuronal differentiation but are also responsible for neuronal maintenance and neuronal functions. Rab proteins are small GTPases localized to the cytosolic surface of specific intracellular compartments and are involved in controlling vesicular transport. Rab proteins, acting as master regulators of the membrane trafficking network, play a central role in both trafficking and signaling pathways of neurotrophin receptors. Axonal transport represents the Achilles' heel of neurons, due to the long-range distance that molecules, organelles and, in particular, neurotrophin-receptor complexes have to cover. Indeed, alterations of axonal transport and, specifically, of axonal trafficking of neurotrophin receptors are responsible for several human neurodegenerative diseases, such as Huntington’s disease, Alzheimer’s disease, amyotrophic lateral sclerosis and some forms of Charcot-Marie-Tooth disease. In this review, we will discuss the link between Rab proteins and neurotrophin receptor trafficking and their influence on downstream signaling pathways.

  11. Developmental expression of the lipocalin Lazarillo and its role in axonal pathfinding in the grasshopper embryo.

    Science.gov (United States)

    Sánchez, D; Ganfornina, M D; Bastiani, M J

    1995-01-01

    This article describes the expression pattern and functional analysis of Lazarillo, a novel cell surface glycoprotein expressed in the embryonic grasshopper nervous system, and a member of the lipocalin family. Lazarillo is expressed by a subset of neuroblasts, ganglion mother cells and neurons of the central nervous system, by all sensory neurons of the peripheral nervous system, and by a subset of neurons of the enteric nervous system. It is also present in a few non neuronal cells associated mainly with the excretory system. A monoclonal antibody raised against Lazarillo perturbs the extent and direction of growth of identified commissural pioneer neurons. We propose that Lazarillo is the receptor for a midline morphogen involved in the outgrowth and guidance of these neurons.

  12. Flight Guidance System Requirements Specification

    Science.gov (United States)

    Miller, Steven P.; Tribble, Alan C.; Carlson, Timothy M.; Danielson, Eric J.

    2003-01-01

    This report describes a requirements specification written in the RSML-e language for the mode logic of a Flight Guidance System of a typical regional jet aircraft. This model was created as one of the first steps in a five-year project sponsored by the NASA Langley Research Center, Rockwell Collins Inc., and the Critical Systems Research Group of the University of Minnesota to develop new methods and tools to improve the safety of avionics designs. This model will be used to demonstrate the application of a variety of methods and techniques, including safety analysis of system and subsystem requirements, verification of key properties using theorem provers and model checkers, identification of potential sources mode confusion in system designs, partitioning of applications based on the criticality of system hazards, and autogeneration of avionics quality code. While this model is representative of the mode logic of a typical regional jet aircraft, it does not describe an actual or planned product. Several aspects of a full Flight Guidance System, such as recovery from failed sensors, have been omitted, and no claims are made regarding the accuracy or completeness of this specification.

  13. Diffuse axonal injury at ultra-high field MRI.

    Directory of Open Access Journals (Sweden)

    Christoph Moenninghoff

    Full Text Available Diffuse axonal injury (DAI is a specific type of traumatic brain injury caused by shearing forces leading to widespread tearing of axons and small vessels. Traumatic microbleeds (TMBs are regarded as a radiological marker for DAI. This study aims to compare DAI-associated TMBs at 3 Tesla (T and 7 T susceptibility weighted imaging (SWI to evaluate possible diagnostic benefits of ultra-high field (UHF MRI.10 study participants (4 male, 6 female, age range 20-74 years with known DAI were included. All MR exams were performed with a 3 T MR system (Magnetom Skyra and a 7 T MR research system (Magnetom 7 T, Siemens AG, Healthcare Sector, Erlangen, Germany each in combination with a 32-channel-receive coil. The average time interval between trauma and imaging was 22 months. Location and count of TMBs were independently evaluated by two neuroradiologists on 3 T and 7 T SWI images with similar and additionally increased spatial resolution at 7 T. Inter- and intraobserver reliability was assessed using the interclass correlation coefficient (ICC. Count and diameter of TMB were evaluated with Wilcoxon signed rank test.Susceptibility weighted imaging revealed a total of 485 TMBs (range 1-190, median 25 at 3 T, 584 TMBs (plus 20%, range 1-262, median 30.5 at 7 T with similar spatial resolution, and 684 TMBs (plus 41%, range 1-288, median 39.5 at 7 T with 10-times higher spatial resolution. Hemorrhagic DAI appeared significantly larger at 7 T compared to 3 T (p = 0.005. Inter- and intraobserver correlation regarding the counted TMB was high and almost equal 3 T and 7 T.7 T SWI improves the depiction of small hemorrhagic DAI compared to 3 T and may be supplementary to lower field strengths for diagnostic in inconclusive or medicolegal cases.

  14. Collective cell migration: guidance principles and hierarchies.

    Science.gov (United States)

    Haeger, Anna; Wolf, Katarina; Zegers, Mirjam M; Friedl, Peter

    2015-09-01

    Collective cell migration results from the establishment and maintenance of collective polarization, mechanocoupling, and cytoskeletal kinetics. The guidance of collective cell migration depends on a reciprocal process between cell-intrinsic multicellular organization with leader-follower cell behavior and results in mechanosensory integration of extracellular guidance cues. Important guidance mechanisms include chemotaxis, haptotaxis, durotaxis, and strain-induced mechanosensing to move cell groups along interfaces and paths of least resistance. Additional guidance mechanisms steering cell groups during specialized conditions comprise electrotaxis and passive drift. To form higher-order cell and tissue structures during morphogenesis and cancer invasion, these guidance principles act in parallel and are integrated for collective adaptation to and shaping of varying tissue environments. We review mechanochemical and electrical inputs and multiparameter signal integration underlying collective guidance, decision making, and outcome. PMID:26137890

  15. Optimal terminal guidance for exoatmospheric interception

    Institute of Scientific and Technical Information of China (English)

    Yu Wenbin; Chen Wanchun; Yang Liang; Liu Xiaoming; Zhou Hao

    2016-01-01

    In this study, two optimal terminal guidance (OTG) laws, one of which takes into account the final velocity vector constraint, are developed for exoatmospheric interception using optimal control theory. In exoatmospheric interception, because the proposed guidance laws give full consideration to the effect of gravity, they consume much less fuel than the traditional guidance laws while requiring a light computational load. In the development of the guidance laws, a unified optimal guidance problem is put forward, where the final velocity vector constraint can be consid-ered or neglected by properly adjusting a parameter in the cost function. To make this problem ana-lytically solvable, a linear model is used to approximate the gravity difference, the difference of the gravitational accelerations of the target and interceptor. Additionally, an example is provided to show that some achievements of this study can be used to significantly improve the fuel efficiency of the pulsed guidance employed by the interceptor whose divert thrust level is fixed.

  16. Health Service use of ionising radiations: Guidance

    International Nuclear Information System (INIS)

    This booklet gives outline guidance on the use of ionising radiations in the Health Service in the United Kingdom. Extensive reference is made to documents where more detailed information may be found. The guidance covers general advice on the medical use of ionising radiations, statutory requirements, and guidance on selected Health Service issues such as patient identification procedures, information management systems, deviations from prescribed radiation dose, imaging and radiotherapy. (57 references) (U.K.)

  17. The use of proteomic analysis to study trafficking defects in axons.

    Science.gov (United States)

    Fu, Xiaoqin; Brown, Kristy J; Rayavarapu, Sree; Nagaraju, Kanneboyina; Liu, Judy S

    2016-01-01

    Mutations in microtubule subunits and microtubule-associated proteins are the causes of many neurological disorders. These human conditions are usually associated with axonal tract defects or degeneration. The molecular mechanisms of these axonal dysfunction are still largely unknown. Conventional methods may not yield a complete analysis of downstream molecules related to axonal dysfunctions. Therefore, we devised a simple unbiased method to screen molecular motors and axonal molecules, which might be involved in axonal defects. We performed our analysis in the mouse with a targeted deletion in the doublecortin (Dcx) gene. Dcx is a microtubule-associated protein with direct effects on microtubule motors. Furthermore, the knockout of Dcx and its functionally redundant structurally similar paralog, doublecortin-like kinase 1 (Dclk1), in mouse results in thinner or absent axon tracts, including the corpus callosum and anterior commissures. We compared protein profiles of corpus callosum from Dcx knockout and wild-type mouse of P0-P2 using mass spectrometry. This strategy allowed us to identify novel candidates downstream of Dcx involved in axon transport.

  18. Effect of fetal spinal cord graft with different methods on axonal pathology after spinal cord contusion

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Objective: To investigate the effect of fetal spinal cord (FSC) graft with different methods on axonal pathology and neurological function recovery after spinal cord injury (SCI).   Methods: Forty Wistar rats were divided into 4 groups. In Group A, the spinal cord was injured and hemisected. In Group B, fetal spinal cord (FSC) was transferred into the injured site. In Group C, after having done as Group B, the upper and lower spinal nerve roots were anastomosed. And in Group D, after having done as Group B, the pedicled omentum was transferred into the hemisection cavity. At 6 weeks after operation, light and electronic microscopes were used to examine the axonal pathology. The neurological function was assessed with inclined plane tests in the open field. The number of axons was quantitated by a computer image analysis system.   Results: A greater loss of axons was observed in Group A than that of other groups at 6 weeks. The sequence of the reduced rate of the axons was as following, Group A>Group B>Group C>Group D (P<0.05). The remaining axons were paralleled with the significant improvement in neurological function recovery of the rats.   Conclusions: It indicates that FSC and pedicled omentum grafts after SCI can protect the axons and promote the neurological function recovery of the rats.

  19. The gene ten-1 contributes to axon regeneration accuracy following femtosecond laser axotomy in C. elegans

    Science.gov (United States)

    Stevens, Dylan T.; Mathew, Manoj; Goksör, Mattias; Pilon, Marc

    2012-10-01

    The precise cutting of axons in C. elegans using short laser pulses permits the investigation of parameters that may influence axonal regeneration. This study began by building and optimizing a femtosecond laser axotomy setup that we first used to monitor the effect of cutting axons near or far from the cell body of the PLM mechanosensory neurons in C. elegans. To assess regeneration, we developed a scoring system where the angle between the regenerating trajectory and its direct line to the target is measured; we called this measurement the "angle of regeneration". The results indicate that axons cut near the cell body regenerate better than those cut far from the cell body but nearer their target. The role of teneurins, which are transmembrane proteins with a large extracellular domain that are thought to regulate the remodelling of the extracellular matrix, has not yet been explored as a potential contributor to axon regeneration. We cut PLM axons in wild-type or ten-1 mutant worms, and measured the angle of regeneration 48 hours later, and the frequency of reconnection to the target. Our results show that functional ten-1 contributes to successful axon regeneration.

  20. Effects of axonal topology on the somatic modulation of synaptic outputs.

    Science.gov (United States)

    Sasaki, Takuya; Matsuki, Norio; Ikegaya, Yuji

    2012-02-22

    Depolarization of the neuronal soma augments synaptic output onto postsynaptic neurons via long-range, axonal cable properties. Here, we report that the range of this somatic influence is spatially restricted by not only axonal path length but also a branching-dependent decrease in axon diameter. Cell-attached recordings of action potentials (APs) from multiple axon branches of a rat hippocampal CA3 pyramidal cell revealed that an AP was broadened following a 20 mV depolarization of the soma and reverted to a normal width during propagation down the axon. The narrowing of the AP depended on the distance traveled by the AP and on the number of axon branch points through which the AP passed. These findings were confirmed by optical imaging of AP-induced calcium elevations in presynaptic boutons, suggesting that the somatic membrane potential modifies synaptic outputs near the soma but not long-projection outputs. Consistent with this prediction, whole-cell recordings from synaptically connected neurons revealed that depolarization of presynaptic CA3 pyramidal cells facilitated synaptic transmission to nearby CA3 pyramidal cells, but not to distant pyramidal cells in CA3 or CA1. Therefore, axonal geometry enables the differential modulation of synaptic output depending on target location.

  1. Serial Section Registration of Axonal Confocal Microscopy Datasets for Long-Range Neural Circuit Reconstruction

    Energy Technology Data Exchange (ETDEWEB)

    Hogrebe, Luke; Paiva, Antonio R.; Jurrus, Elizabeth R.; Christensen, Cameron; Bridge, Michael; Dai, Li; Pfeiffer, Rebecca; Hof, Patrick; Roysam, Badrinath; Korenberg, Julie; Tasdizen, Tolga

    2012-06-15

    In the context of long-range digital neural circuit reconstruction, this paper investigates an approach for registering axons across histological serial sections. Tracing distinctly labeled axons over large distances allows neuroscientists to study very explicit relationships between the brain's complex interconnects and, for example, diseases or aberrant development. Large scale histological analysis requires, however, that the tissue be cut into sections. In immunohistochemical studies thin sections are easily distorted due to the cutting, preparation, and slide mounting processes. In this work we target the registration of thin serial sections containing axons. Sections are first traced to extract axon centerlines, and these traces are used to define registration landmarks where they intersect section boundaries. The trace data also provides distinguishing information regarding an axon's size and orientation within a section. We propose the use of these features when pairing axons across sections in addition to utilizing the spatial relationships amongst the landmarks. The global rotation and translation of an unregistered section are accounted for using a random sample consensus (RANSAC) based technique. An iterative nonrigid refinement process using B-spline warping is then used to reconnect axons and produce the sought after connectivity information.

  2. Hybrid Guidance System for Relative Navigation Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Future NASA architectures and missions will involve many distributed platforms that must work together. This in turn requires guidance, navigation and control...

  3. Positioning and guidance of neurons on Au by directed assembly of proteins using Atomic Force Microscopy.

    Science.gov (United States)

    Staii, Cristian; Viesselmann, Chris; Ballweg, Jason; Williams, Justin; Dent, Erik; Coppersmith, Susan; Eriksson, Mark

    2009-03-01

    The specific interactions between neurons and guidance factors as well as the mechanism of axonal navigation toward a target in the developing brain are not well understood. To address this problem we present a new approach for controlling the adhesion, growth and interconnectivity of cortical neurons on Au surfaces. Specifically, we use AFM nanolithography to immobilize extracellular matrix proteins at well-defined locations on Au surfaces, and show that these protein patterns can confine neuronal cells and control their growth and interconnectivity. We will compare this method with other nanofabrication techniques and discuss its main advantages: 1) the procedure is carried out in aqueous solutions, so that the proteins retain their bioactivity, 2) a high degree of control over location and shape of the protein patterns can be achieved, and 3) the minimum protein feature size can be as small as 50nm.

  4. gamma-Diketone neuropathy: axon atrophy and the role of cytoskeletal protein adduction.

    Science.gov (United States)

    LoPachin, Richard M; DeCaprio, Anthony P

    2004-08-15

    Multifocal giant neurofilamentous axonal swellings and secondary distal degeneration have been historically considered the hallmark features of gamma-diketone neuropathy. Accordingly, research conducted over the past 25 years has been directed toward discerning mechanisms of axonal swelling. However, this neuropathological convention has been challenged by recent observations that swollen axons were an exclusive product of long-term 2.5-hexanedione (HD) intoxication at lower daily dose-rates (e.g., 175 mg/kg/day); that is, higher HD dose-rates (e.g., 400 mg/kg/day) produced neurological deficits in the absence of axonal swellings. The observation that neurological toxicity can be expressed without axonal swelling suggests that this lesion is not an important pathophysiological event. Instead, several research groups have now shown that axon atrophy is prevalent in nervous tissues of laboratory animals intoxicated over a wide range of HD dose-rates. The well-documented nerve conduction defects associated with axon atrophy, in conjunction with the temporal correspondence between this lesion and the onset of neurological deficits, strongly suggest that atrophy has pathophysiological significance. In this commentary, we present evidence that supports a pathognomonic role for axon atrophy in gamma-diketone neuropathy and suggests that the functional consequences of this lesion mediate the corresponding neurological toxicity. Previous research has demonstrated that HD interacts with proteins via formation of pyrrole adducts. We therefore discuss the possibility that this chemical process is essential to the mechanism of atrophy. Evidence presented in this review suggests that "distal axonopathy" is an inaccurate classification and future nosological schemes should be based on the apparent primacy of axon atrophy. PMID:15289087

  5. Adaptive Guidance based on Context Profile for Software Process Modeling

    Directory of Open Access Journals (Sweden)

    Hamid Khemissa

    2012-07-01

    Full Text Available This paper aims to define an adaptive guidance for software process modeling. The proposed guidance approach is based on development’s profile context (actor’s role in the process, actor’s qualification and related activities in progress. We introduce new guidance concepts through adaptive guidance meta-model (AGM allowing specific assistance interventions (corrective, constructive and automatic guidance. We illustrate our guidance approach using SPEM formalism extended with these new guidance concepts.

  6. Enzyme-instructed self-assembly of taxol promotes axonal branching

    Science.gov (United States)

    Mei, Bin; Miao, Qingqing; Tang, Anming; Liang, Gaolin

    2015-09-01

    Axonal branching is important for vertebrate neuron signaling. Taxol has a biphasic effect on axonal branching (i.e., high concentration inhibits axonal growth but low concentration restores it). To the best of our knowledge, low concentration of taxol to promote axonal branching has not been reported yet. Herein, we rationally designed a taxol derivative Fmoc-Phe-Phe-Lys(taxol)-Tyr(H2PO4)-OH (1) which could be subjected to alkaline phosphatase (ALP)-catalyzed self-assembly to form taxol nanofibers. We found that, at 10 μM, 1 has a microtubule (MT) condensation effect similar to that of taxol on mammalian cells but with more chronic toxicity than taxol on the cells. At a low concentration of 10 nM, 1 not only promoted neurite elongation as taxol did but also promoted axonal branching which was not achieved by using taxol. We propose that self-assembly of 1 along the MTs prohibited their lateral contacts and thus promoted axonal branching. Our strategy of enzyme-instructed self-assembly (EISA) of a taxol derivative provides a new tool for scientists to study the morphology of neurons, as well as their behaviours.Axonal branching is important for vertebrate neuron signaling. Taxol has a biphasic effect on axonal branching (i.e., high concentration inhibits axonal growth but low concentration restores it). To the best of our knowledge, low concentration of taxol to promote axonal branching has not been reported yet. Herein, we rationally designed a taxol derivative Fmoc-Phe-Phe-Lys(taxol)-Tyr(H2PO4)-OH (1) which could be subjected to alkaline phosphatase (ALP)-catalyzed self-assembly to form taxol nanofibers. We found that, at 10 μM, 1 has a microtubule (MT) condensation effect similar to that of taxol on mammalian cells but with more chronic toxicity than taxol on the cells. At a low concentration of 10 nM, 1 not only promoted neurite elongation as taxol did but also promoted axonal branching which was not achieved by using taxol. We propose that self-assembly of 1

  7. Clinical features and molecular modelling of novel MPZ mutations in demyelinating and axonal neuropathies

    OpenAIRE

    Mandich, Paola; Fossa, Paola; Capponi, Simona; Geroldi, Alessandro; Acquaviva, Massimo; Gulli, Rossella; Ciotti, Paola; MANGANELLI, FIORE; Grandis, Marina; Bellone, Emilia

    2009-01-01

    Mutations in the myelin protein zero (MPZ) gene have been associated with different Charcot–Marie–Tooth disease (CMT) phenotypes, including classical demyelinating CMT1B and the axonal form of the disease (CMT2). The MPZ role in the pathogenesis of both demyelinating and axonal inherited neuropathies was evaluated in the Italian population by screening a cohort of 214 patients with CMT1 or CMT2. A MPZ mutation frequency of 7.9% in demyelinating cases and of 4.8% in axonal cases was observed. ...

  8. [A case of acute motor sensory axonal polyneuropathy after Haemophilus influenzae infection].

    Science.gov (United States)

    Oda, M; Udaka, F; Kubori, T; Oka, N; Kameyama, M

    2000-08-01

    A 47-year-old woman developed consciousness disturbance, and experienced hallucinations while traveling abroad, and then went into critical condition. She was placed in the critical care unit, and had flaccid tetraparesis requiring mechanical ventilation. Haemophilus influenzae was cultured from the sputum. The level of protein of the cerebrospinal fluid was elevated to 114 mg/dl, nerve conduction study showed findings of pure axonal damage, and the sural nerve biopsy revealed severe axonal degeneration. She improved gradually by plasma exchange. The diagnosis of acute motor sensory axonal polyneuropathy (AMSAN) based on autoimmune mechanism was made. We speculate that H. influenzae infection may have elicited AMSAN in this case. PMID:11218707

  9. Axonal recovery after severe traumatic brain injury demonstrated in vivo by 1H MR spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Danielsen, E.R.; Thomsen, C. [Department of Neuroradiology, Section 3023, Rigshospitalet, Copenhagen (Denmark); Christensen, P.B. [Hammel Neurocentre, Department of Neurology, Aarhus University Hospital (Denmark); Arlien-Soeborg, P. [Department of Neurology, Rigshospitalet, Copenhagen (Denmark)

    2003-10-01

    Proton magnetic resonance spectroscopy (MRS) suggested almost complete axonal recovery 21 months after trauma in a patient with severe diffuse axonal injury. MRS while the patient was comatose showed evidence of severe diffuse axonal injury in occipitoparietal white matter, but occipital grey matter was relatively spared. At 21 months N-acetylaspartate was normal. At 33 months examination showed a Functional Independence Measure of 83 and a Rancho Los Amigos Scale of Cognitive Function of 7-8, a remarkable improvement considering all the initial findings, except those of MRS. (orig.)

  10. Hematopoietic progenitors express myelin basic protein and ensheath axons in Shiverer brain.

    Science.gov (United States)

    Goolsby, James; Makar, Tapas; Dhib-Jalbut, Suhayl; Bever, Christopher T; Pessac, Bernard; Trisler, David

    2013-04-15

    Oligodendroglia are cells of the central nervous system (CNS) that form myelin sheath, which insulates neuronal axons. Neuropathologies of the CNS include dysmyelination of axons in multiple sclerosis and CNS trauma. Cell replacement is a promising but largely untested therapy for dysmyelination. Shiverer mouse, a genetic mutant that does not synthesize full-length myelin basic protein (MBP), a critical prerequisite protein in CNS myelin sheath formation, provides an unequivocal model for determining the potential of stem cells to become oligodendroglia. We demonstrate that adult wild-type mouse bone marrow stem cells can express MBP and ensheath axons when transplanted into Shiverer brain.

  11. Diffuse axonal injury: detection of changes in anisotropy of water diffusion by diffusion-weighted imaging

    Energy Technology Data Exchange (ETDEWEB)

    Chan, J.H.M.; Tsui, E.Y.K.; Yuen, M.K. [Department of Diagnostic Radiology, Tuen Mun Hospital, Tsing Chung Koon Road, Tuen Mun, N.T., Hong Kong (China); Peh, W.C.G. [Department of Diagnostic Radiology, Singapore General Hospital (Singapore); Fong, D.; Fok, K.F.; Leung, K.M. [Department of Neurosurgery, Tuen Mun Hospital (Hong Kong); Fung, K.K.L. [Department of Optometry and Radiography, Hong Kong Polytechnic University (China)

    2003-01-01

    Myelinated axons of white matter demonstrate prominent directional differences in water diffusion. We performed diffusion-weighted imaging on ten patients with head injury to explore the feasibility of using water diffusion anisotropy for quantitating diffuse axonal injury. We showed significant decrease in diffusion anisotropy indices in areas with or without signal abnormality on T2 and T2*-weighted images. We conclude that the water diffusion anisotropy index a potentially useful, sensitive and quantitative way of diagnosing and assessing patients with diffuse axonal injury. (orig.)

  12. In vivo axonal transport deficits in a mouse model of fronto-temporal dementia

    Directory of Open Access Journals (Sweden)

    Tabassum Majid

    2014-01-01

    Discussion: In our study, we identified the presence of age-dependent axonal transport deficits beginning at 3 months of age in rTg4510 mice. We correlated these deficits at 3 months to the presence of hyperphosphorylated tau in the brain and the presence within the olfactory epithelium. We observed tau pathology not only in the soma of these neurons but also within the axons and processes of these neurons. Our characterization of axonal transport in this tauopathy model provides a functional time point that can be used for future therapeutic interventions.

  13. Local protein synthesis in neuronal axons: why and how we study

    OpenAIRE

    Kim, Eunjin; Jung, Hosung

    2015-01-01

    Adaptive brain function and synaptic plasticity rely on dynamic regulation of local proteome. One way for the neuron to introduce new proteins to the axon terminal is to transport those from the cell body, which had long been thought as the only source of axonal proteins. Another way, which is the topic of this review, is synthesizing proteins on site by local mRNA translation. Recent evidence indicates that the axon stores a reservoir of translationally silent mRNAs and regulates their expre...

  14. Agent Based Individual Traffic Guidance

    DEFF Research Database (Denmark)

    Wanscher, Jørgen

    This thesis investigates the possibilities in applying Operations Research (OR) to autonomous vehicular traffic. The explicit difference to most other research today is that we presume that an agent is present in every vehicle - hence Agent Based Individual Traffic guidance (ABIT). The next...... evolutionary step for the in-vehicle route planners is the introduction of two-way communication. We presume that the agent is capable of exactly this. Based on this presumption we discuss the possibilities and define a taxonomy and use this to discuss the ABIT system. Based on a set of scenarios we conclude...... that the system can be divided into two separate constituents. The immediate dispersion, which is used for small areas and quick response, and the individual alleviation, which considers the longer distance decision support. Both of these require intrinsicate models and cost functions which at the beginning...

  15. Evaluation of D1 and D2 Dopamine Receptor Segregation in the Developing Striatum Using BAC Transgenic Mice

    OpenAIRE

    Dominic Thibault; Fabien Loustalot; Fortin, Guillaume M.; Marie-Josée Bourque; Louis-Éric Trudeau

    2013-01-01

    The striatum is predominantly composed of medium spiny neurons (MSNs) that send their axons along two parallel pathways known as the direct and indirect pathways. MSNs from the direct pathway express high levels of D1 dopamine receptors, while MSNs from the indirect pathway express high levels of D2 dopamine receptors. There has been much debate over the extent of colocalization of these two major dopamine receptors in MSNs of adult animals. In addition, the ontogeny of the segregation proces...

  16. Axonal localization of neuritin/CPG15 mRNA in neuronal populations through distinct 5' and 3' UTR elements.

    Science.gov (United States)

    Merianda, Tanuja T; Gomes, Cynthia; Yoo, Soonmoon; Vuppalanchi, Deepika; Twiss, Jeffery L

    2013-08-21

    Many neuronal mRNAs are actively transported into distal axons. The 3' untranslated regions (UTRs) of axonal mRNAs often contain cues for their localization. The 3' UTR of neuritin mRNA was shown to be sufficient for localization into axons of hippocampal neurons. Here, we show that neuritin mRNA localizes into axons of rat sensory neurons, but this is predominantly driven by the 5' rather than 3' UTR. Neuritin mRNA shifts from cell body to axon predominantly after nerve crush injury, suggesting that it encodes a growth-associated protein. Consistent with this, overexpression of neuritin increases axon growth but only when its mRNA localizes into the axons. PMID:23966695

  17. 78 FR 37231 - Guidance for Industry; Guidance on Abbreviated New Drug Applications: Stability Testing of Drug...

    Science.gov (United States)

    2013-06-20

    ... HUMAN SERVICES Food and Drug Administration Guidance for Industry; Guidance on Abbreviated New Drug... Administration, HHS. ACTION: Notice. SUMMARY: The Food and Drug Administration (FDA or Agency) is announcing the...) review process more efficient. DATES: Submit either electronic or written comments on Agency guidances...

  18. Driving change : sustainable development action plans Guidance

    OpenAIRE

    Sustainable Development Commission

    2008-01-01

    This guidance builds upon the Sustainable Development Commission’s previous guidance, Getting Started (August 2005), which set out the basic elements that the Sustainable Development Commission would expect to see in a good Sustainable Development Action Plan. Publisher PDF Original published August 2005.

  19. Minimum variation guidance laws for interceptor missiles

    NARCIS (Netherlands)

    Weiss, M.; Shima, T.

    2014-01-01

    This paper introduces a new approach to guidance law design using linear quadratic optimal control theory, minimizing throughout the engagement the variation of the control input as well as the integral control effort. The guidance law is derived for arbitrary order missile dynamics and target maneu

  20. 75 FR 76079 - Sound Incentive Compensation Guidance

    Science.gov (United States)

    2010-12-07

    ... Office of Thrift Supervision Sound Incentive Compensation Guidance AGENCY: Office of Thrift Supervision... collection. Title of Proposal: Sound Incentive Compensation Guidance. OMB Number: 1550-0129. Form Number: N/A... compensation arrangements at a financial institution do not encourage employees to take excessive risks....

  1. 75 FR 53023 - Sound Incentive Compensation Guidance

    Science.gov (United States)

    2010-08-30

    ... Office of Thrift Supervision Sound Incentive Compensation Guidance AGENCY: Office of Thrift Supervision... collection. Title of Proposal: Sound Incentive Compensation Guidance. OMB Number: 1550-0129. Form Number: N/A... compensation arrangements at a financial institution do not encourage employees to take excessive risks....

  2. 75 FR 22679 - Sound Incentive Compensation Guidance

    Science.gov (United States)

    2010-04-29

    ... Office of Thrift Supervision Sound Incentive Compensation Guidance AGENCY: Office of Thrift Supervision... collection. Title of Proposal: Sound Incentive Compensation Guidance. OMB Number: 1550-0NEW. Form Number: N/A... compensation arrangements at a financial institution do not encourage employees to take excessive risks....

  3. Guidance for performing preliminary assessments under CERCLA

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1991-09-01

    EPA headquarters and a national site assessment workgroup produced this guidance for Regional, State, and contractor staff who manage or perform preliminary assessments (PAs). EPA has focused this guidance on the types of sites and site conditions most commonly encountered. The PA approach described in this guidance is generally applicable to a wide variety of sites. However, because of the variability among sites, the amount of information available, and the level of investigative effort required, it is not possible to provide guidance that is equally applicable to all sites. PA investigators should recognize this and be aware that variation from this guidance may be necessary for some sites, particularly for PAs performed at Federal facilities, PAs conducted under EPA`s Environmental Priorities Initiative (EPI), and PAs at sites that have previously been extensively investigated by EPA or others. The purpose of this guidance is to provide instructions for conducting a PA and reporting results. This guidance discusses the information required to evaluate a site and how to obtain it, how to score a site, and reporting requirements. This document also provides guidelines and instruction on PA evaluation, scoring, and the use of standard PA scoresheets. The overall goal of this guidance is to assist PA investigators in conducting high-quality assessments that result in correct site screening or further action recommendations on a nationally consistent basis.

  4. Career Guidance in the Elementary School

    Science.gov (United States)

    Leonard, George E.

    1971-01-01

    The purpose of this column is to discuss, describe and disseminate information regarding career guidance principles and practices in the elementary schools. Specifically the activities of the Developmental Career Guidance Projects in inner city Detroit are described. The activities emphasize action involvement of children while didactic learning…

  5. How Effective Is Central Bank Forward Guidance?

    NARCIS (Netherlands)

    Kool, C.J.M.; Thornton, D.L.

    2012-01-01

    In this paper, we use survey forecasts to investigate the impact of forward guidance on the predictability of future short- and long-term interest rates in four countries: New Zealand, Norway, Sweden, and the United States. New Zealand began providing forward guidance in 1997, Norway in 2005, and Sw

  6. 78 FR 57450 - State Rail Plan Guidance

    Science.gov (United States)

    2013-09-18

    ... authorized in the Act and available under the High-Speed Intercity Passenger Rail program. This guidance... qualifies States to receive grants for high-speed rail only. Response: Operational information about all... Federal Railroad Administration State Rail Plan Guidance AGENCY: Federal Railroad Administration...

  7. The axonal repellent, Slit2, inhibits directional migration of circulating neutrophils.

    Science.gov (United States)

    Tole, Soumitra; Mukovozov, Ilya M; Huang, Yi-Wei; Magalhaes, Marco A O; Yan, Ming; Crow, Min Rui; Liu, Guang Ying; Sun, Chun Xiang; Durocher, Yves; Glogauer, Michael; Robinson, Lisa A

    2009-12-01

    In inflammatory diseases, circulating neutrophils are recruited to sites of injury. Attractant signals are provided by many different chemotactic molecules, such that blockade of one may not prevent neutrophil recruitment effectively. The Slit family of secreted proteins and their transmembrane receptor, Robo, repel axonal migration during CNS development. Emerging evidence shows that by inhibiting the activation of Rho-family GTPases, Slit2/Robo also inhibit migration of other cell types toward a variety of chemotactic factors in vitro and in vivo. The role of Slit2 in inflammation, however, has been largely unexplored. We isolated primary neutrophils from human peripheral blood and mouse bone marrow and detected Robo-1 expression. Using video-microscopic live cell tracking, we found that Slit2 selectively impaired directional migration but not random movement of neutrophils toward fMLP. Slit2 also inhibited neutrophil migration toward other chemoattractants, namely C5a and IL-8. Slit2 inhibited neutrophil chemotaxis by preventing chemoattractant-induced actin barbed end formation and cell polarization. Slit2 mediated these effects by suppressing inducible activation of Cdc42 and Rac2 but did not impair activation of other major kinase pathways involved in neutrophil migration. We further tested the effects of Slit2 in vivo using mouse models of peritoneal inflammation induced by sodium periodate, C5a, and MIP-2. In all instances, Slit2 reduced neutrophil recruitment effectively (PSlit2 potently inhibits chemotaxis but not random motion of circulating neutrophils and point to Slit2 as a potential new therapeutic for preventing localized inflammation.

  8. Improving rehabilitation exercise performance through visual guidance.

    Science.gov (United States)

    Lam, Agnes W K; HajYasien, Ahmed; Kulic, Dana

    2014-01-01

    In current physical rehabilitation protocols, patients typically perform exercises without feedback or guidance following the initial demonstrations from the physiotherapist. This paper proposes a system providing continuous visual feedback and guidance to patients to improve quality of motion performance and adherence to instructions. The system consists of body-worn inertial measurement units which continuously measure the patient's pose. The measured pose is overlaid with the instructed motion on a visual display shown to the user during exercise performance. Two user studies were conducted with healthy participants to evaluate the usability of the visual guidance tool. Motion data was collected by the inertial measurement sensors and used to evaluate quality of motion, comparing user performance with and without visual feedback and with or without exercise guidance. The quantitative and qualitative results of the studies confirm that performing the exercises with the visual guidance tool promotes more consistent exercise performance and proper technique. PMID:25570311

  9. An Adaptive Weighted Differential Game Guidance Law

    Institute of Scientific and Technical Information of China (English)

    ZHANG Ping; FANG Yangwang; ZHANG Fengming; XIAO Bingsong; HU Shiguo; ZONG Shuning

    2012-01-01

    For intercepting modern high maneuverable targets,a novel adaptive weighted differential game guidance law based on the game theory of mixed strategy is proposed,combining two guidance laws which are derived from the perfect and imperfect information pattem,respectively.The weights vary according to the estimated error of the target's acceleration,the guidance law is generated by directly using the estimation of target's acceleration when the estimated error is small,and a differential game guidance law with adaptive penalty coefficient is implemented when the estimated error is large.The adaptive penalty coefficients are not constants and they can be adjusted with current target maneuverability.The superior homing performance of the new guidance law is verified by computer simulations.

  10. An adaptive guidance algorithm for aerospace vehicles

    Science.gov (United States)

    Bradt, J. E.; Hardtla, J. W.; Cramer, E. J.

    The specifications for proposed space transportation systems are placing more emphasis on developing reusable avionics subsystems which have the capability to respond to vehicle evolution and diverse missions while at the same time reducing the cost of ground support for mission planning, contingency response and verification and validation. An innovative approach to meeting these goals is to specify the guidance problem as a multi-point boundary value problen and solve that problem using modern control theory and nonlinear constrained optimization techniques. This approach has been implemented as Gamma Guidance (Hardtla, 1978) and has been successfully flown in the Inertial Upper Stage. The adaptive guidance algorithm described in this paper is a generalized formulation of Gamma Guidance. The basic equations are presented and then applied to four diverse aerospace vehicles to demonstrate the feasibility of using a reusable, explicit, adaptive guidance algorithm for diverse applications and vehicles.

  11. 75 FR 59268 - Draft Guidance for Industry: Acidified Foods; Availability

    Science.gov (United States)

    2010-09-27

    ... HUMAN SERVICES Food and Drug Administration Draft Guidance for Industry: Acidified Foods; Availability...) is announcing the availability of a draft guidance entitled ``Guidance for Industry: Acidified Foods... requests for single copies of the draft guidance entitled ``Guidance for Industry: Acidified Foods'' to...

  12. Chronic Exposure to Androgenic-Anabolic Steroids Exacerbates Axonal Injury and Microgliosis in the CHIMERA Mouse Model of Repetitive Concussion.

    Science.gov (United States)

    Namjoshi, Dhananjay R; Cheng, Wai Hang; Carr, Michael; Martens, Kris M; Zareyan, Shahab; Wilkinson, Anna; McInnes, Kurt A; Cripton, Peter A; Wellington, Cheryl L

    2016-01-01

    Concussion is a serious health concern. Concussion in athletes is of particular interest with respect to the relationship of concussion exposure to risk of chronic traumatic encephalopathy (CTE), a neurodegenerative condition associated with altered cognitive and psychiatric functions and profound tauopathy. However, much remains to be learned about factors other than cumulative exposure that could influence concussion pathogenesis. Approximately 20% of CTE cases report a history of substance use including androgenic-anabolic steroids (AAS). How acute, chronic, or historical AAS use may affect the vulnerability of the brain to concussion is unknown. We therefore tested whether antecedent AAS exposure in young, male C57Bl/6 mice affects acute behavioral and neuropathological responses to mild traumatic brain injury (TBI) induced with the CHIMERA (Closed Head Impact Model of Engineered Rotational Acceleration) platform. Male C57Bl/6 mice received either vehicle or a cocktail of three AAS (testosterone, nandrolone and 17α-methyltestosterone) from 8-16 weeks of age. At the end of the 7th week of treatment, mice underwent two closed-head TBI or sham procedures spaced 24 h apart using CHIMERA. Post-repetitive TBI (rTBI) behavior was assessed for 7 d followed by tissue collection. AAS treatment induced the expected physiological changes including increased body weight, testicular atrophy, aggression and downregulation of brain 5-HT1B receptor expression. rTBI induced behavioral deficits, widespread axonal injury and white matter microgliosis. While AAS treatment did not worsen post-rTBI behavioral changes, AAS-treated mice exhibited significantly exacerbated axonal injury and microgliosis, indicating that AAS exposure can alter neuronal and innate immune responses to concussive TBI. PMID:26784694

  13. Chronic Exposure to Androgenic-Anabolic Steroids Exacerbates Axonal Injury and Microgliosis in the CHIMERA Mouse Model of Repetitive Concussion.

    Directory of Open Access Journals (Sweden)

    Dhananjay R Namjoshi

    Full Text Available Concussion is a serious health concern. Concussion in athletes is of particular interest with respect to the relationship of concussion exposure to risk of chronic traumatic encephalopathy (CTE, a neurodegenerative condition associated with altered cognitive and psychiatric functions and profound tauopathy. However, much remains to be learned about factors other than cumulative exposure that could influence concussion pathogenesis. Approximately 20% of CTE cases report a history of substance use including androgenic-anabolic steroids (AAS. How acute, chronic, or historical AAS use may affect the vulnerability of the brain to concussion is unknown. We therefore tested whether antecedent AAS exposure in young, male C57Bl/6 mice affects acute behavioral and neuropathological responses to mild traumatic brain injury (TBI induced with the CHIMERA (Closed Head Impact Model of Engineered Rotational Acceleration platform. Male C57Bl/6 mice received either vehicle or a cocktail of three AAS (testosterone, nandrolone and 17α-methyltestosterone from 8-16 weeks of age. At the end of the 7th week of treatment, mice underwent two closed-head TBI or sham procedures spaced 24 h apart using CHIMERA. Post-repetitive TBI (rTBI behavior was assessed for 7 d followed by tissue collection. AAS treatment induced the expected physiological changes including increased body weight, testicular atrophy, aggression and downregulation of brain 5-HT1B receptor expression. rTBI induced behavioral deficits, widespread axonal injury and white matter microgliosis. While AAS treatment did not worsen post-rTBI behavioral changes, AAS-treated mice exhibited significantly exacerbated axonal injury and microgliosis, indicating that AAS exposure can alter neuronal and innate immune responses to concussive TBI.

  14. Axonal degeneration stimulates the formation of NG2+ cells and oligodendrocytes in the mouse

    DEFF Research Database (Denmark)

    Nielsen, Helle Hvilsted; Ladeby, Rune; Drøjdahl, Nina;

    2006-01-01

    Proliferation of the adult NG2-expressing oligodendrocyte precursor cells has traditionally been viewed as a remyelination response ensuing from destruction of myelin and oligodendrocytes, and not to the axonal pathology that is also a characteristic of demyelinating disease. To better understand...... the response of the NG2+ cells to the different components of demyelinating pathology, we investigated the response of adult NG2+ cells to axonal degeneration in the absence of primary myelin or oligodendrocyte pathology. Axonal degeneration was induced in the hippocampal dentate gyrus of adult mice...... by transection of the entorhino-dentate perforant path projection. The acutely induced degeneration of axons and terminals resulted in a prompt response of NG2+ cells, consisting of morphological transformation, cellular proliferation, and upregulation of NG2 expression days 2-3 after surgery. This was followed...

  15. Vertebrate Fidgetin Restrains Axonal Growth by Severing Labile Domains of Microtubules

    Directory of Open Access Journals (Sweden)

    Lanfranco Leo

    2015-09-01

    Full Text Available Individual microtubules (MTs in the axon consist of a stable domain that is highly acetylated and a labile domain that is not. Traditional MT-severing proteins preferentially cut the MT in the stable domain. In Drosophila, fidgetin behaves in this fashion, with targeted knockdown resulting in neurons with a higher fraction of acetylated (stable MT mass in their axons. Conversely, in a fidgetin knockout mouse, the fraction of MT mass that is acetylated is lower than in the control animal. When fidgetin is depleted from cultured rodent neurons, there is a 62% increase in axonal MT mass, all of which is labile. Concomitantly, there are more minor processes and a longer axon. Together with experimental data showing that vertebrate fidgetin targets unacetylated tubulin, these results indicate that vertebrate fidgetin (unlike its fly ortholog regulates neuronal development by tamping back the expansion of the labile domains of MTs.

  16. Mechanisms of sodium channel clustering and its influence on axonal impulse conduction.

    Science.gov (United States)

    Freeman, Sean A; Desmazières, Anne; Fricker, Desdemona; Lubetzki, Catherine; Sol-Foulon, Nathalie

    2016-02-01

    The efficient propagation of action potentials along nervous fibers is necessary for animals to interact with the environment with timeliness and precision. Myelination of axons is an essential step to ensure fast action potential propagation by saltatory conduction, a process that requires highly concentrated voltage-gated sodium channels at the nodes of Ranvier. Recent studies suggest that the clustering of sodium channels can influence axonal impulse conduction in both myelinated and unmyelinated fibers, which could have major implications in disease, particularly demyelinating pathology. This comprehensive review summarizes the mechanisms governing the clustering of sodium channels at the peripheral and central nervous system nodes and the specific roles of their clustering in influencing action potential conduction. We further highlight the classical biophysical parameters implicated in conduction timing, followed by a detailed discussion on how sodium channel clustering along unmyelinated axons can impact axonal impulse conduction in both physiological and pathological contexts. PMID:26514731

  17. Microtubule stabilization reduces scarring and causes axon regeneration after spinal cord injury

    NARCIS (Netherlands)

    F. Hellal (Farida); A. Hurtado (Andres); J. Ruschel (Jörg); K.C. Flynn (Kevin); C.J. Laskowski (Claudia); M. Umlauf (Martina); L.C. Kapitein (Lukas); D. Strikis (Dinara); V. Lemmon (Vance); J. Bixby (John); C.C. Hoogenraad (Casper); F. Bradke (Frank)

    2011-01-01

    textabstractHypertrophic scarring and poor intrinsic axon growth capacity constitute major obstacles for spinal cord repair. These processes are tightly regulated by microtubule dynamics. Here, moderate microtubule stabilization decreased scar formation after spinal cord injury in rodents through va

  18. Calcium-Activated Potassium Channels at Nodes of Ranvier Secure Axonal Spike Propagation

    Directory of Open Access Journals (Sweden)

    Jan Gründemann

    2015-09-01

    Full Text Available Functional connectivity between brain regions relies on long-range signaling by myelinated axons. This is secured by saltatory action potential propagation that depends fundamentally on sodium channel availability at nodes of Ranvier. Although various potassium channel types have been anatomically localized to myelinated axons in the brain, direct evidence for their functional recruitment in maintaining node excitability is scarce. Cerebellar Purkinje cells provide continuous input to their targets in the cerebellar nuclei, reliably transmitting axonal spikes over a wide range of rates, requiring a constantly available pool of nodal sodium channels. We show that the recruitment of calcium-activated potassium channels (IK, KCa3.1 by local, activity-dependent calcium (Ca2+ influx at nodes of Ranvier via a T-type voltage-gated Ca2+ current provides a powerful mechanism that likely opposes depolarizing block at the nodes and is thus pivotal to securing continuous axonal spike propagation in spontaneously firing Purkinje cells.

  19. Contrast and stability of the axon diameter index from microstructure imaging with diffusion MRI

    DEFF Research Database (Denmark)

    Dyrby, Tim B; Søgaard, Lise V; Hall, Matt G;

    2013-01-01

    (max) ) on a scanner influence the sensitivity to a range of axon diameters. Multishell high-angular-diffusion-imaging (HARDI) protocols for G(max) of 60, 140, 200, and 300 mT/m were optimized for the pulsed-gradient-spin-echo (PGSE) sequence. Data were acquired on a fixed monkey brain and Monte-Carlo simulations...... supported the results. Increasing G(max) reduces within-voxel variation of the axon diameter index and improves contrast beyond what is achievable with higher signal-to-noise ratio. Simulations reveal an upper bound on the axon diameter (∼10 μm) that pulsed-gradient-spin-echo measurements are sensitive to......(max) for enhancing contrast between axon diameter distributions and are, therefore, relevant in general for microstructure imaging methods and highlight the need for increased G(max) on future commercial systems. Magn Reson Med, 2012. © 2012 Wiley Periodicals, Inc....

  20. Axonal plasticity elicits long-term changes in oligodendroglia and myelinated fibers

    DEFF Research Database (Denmark)

    Drøjdahl, Nina; Nielsen, Helle Hvilsted; Gardi, Jonathan E;

    2010-01-01

    Axons are linked to induction of myelination during development and to the maintenance of myelin and myelinated tracts in the adult CNS. Currently, it is unknown whether and how axonal plasticity in adult CNS impacts the myelinating cells and their precursors. In this article, we report that newly...... formed axonal sprouts are able to induce a protracted myelination response in adult CNS. We show that newly formed axonal sprouts, induced by lesion of the entorhino-hippocampal perforant pathway, have the ability to induce a myelination response in stratum radiatum and lucidum CA3. The lesion resulted...... in significant recruitment of newly formed myelinating cells, documented by incorporation of the proliferation marker bromodeoxyuridine into chondroitin sulphate NG2 expressing cells in stratum radiatum and lucidum CA3 early after lesion, and the occurrence of a 28% increase in the number of oligodendrocytes...

  1. Calcium-dependent proteasome activation is required for axonal neurofilament degradation.

    Science.gov (United States)

    Park, Joo Youn; Jang, So Young; Shin, Yoon Kyung; Suh, Duk Joon; Park, Hwan Tae

    2013-12-25

    Even though many studies have identified roles of proteasomes in axonal degeneration, the molecular mechanisms by which axonal injury regulates proteasome activity are still unclear. In the present study, we found evidence indicating that extracellular calcium influx is an upstream regulator of proteasome activity during axonal degeneration in injured peripheral nerves. In degenerating axons, the increase in proteasome activity and the degradation of ubiquitinated proteins were significantly suppressed by extracellular calcium chelation. In addition, electron microscopic findings revealed selective inhibition of neurofilament degradation, but not microtubule depolymerization or mitochondrial swelling, by the inhibition of calpain and proteasomes. Taken together, our findings suggest that calcium increase and subsequent proteasome activation are an essential initiator of neurofilament degradation in Wallerian degeneration. PMID:25206662

  2. Calcium-dependent proteasome activation is required for axonal neurofilament degradation

    Institute of Scientific and Technical Information of China (English)

    Joo Youn Park; So Young Jang; Yoon Kyung Shin; Duk Joon Suh; Hwan Tae Park

    2013-01-01

    Even though many studies have identified roles of proteasomes in axonal degeneration, the mo-lecular mechanisms by which axonal injury regulates proteasome activity are stil unclear. In the present study, we found evidence indicating that extracellular calcium influx is an upstream regula-tor of proteasome activity during axonal degeneration in injured peripheral nerves. In degenerating axons, the increase in proteasome activity and the degradation of ubiquitinated proteins were sig-nificantly suppressed by extracellular calcium chelation. In addition, electron microscopic findings revealed selective inhibition of neurofilament degradation, but not microtubule depolymerization or mitochondrial swel ing, by the inhibition of calpain and proteasomes. Taken together, our findings suggest that calcium increase and subsequent proteasome activation are an essential initiator of neurofilament degradation in Wal erian degeneration.

  3. Lentiviral vectors express chondroitinase ABC in cortical projections and promote sprouting of injured corticospinal axons.

    Science.gov (United States)

    Zhao, Rong-Rong; Muir, Elizabeth M; Alves, João Nuno; Rickman, Hannah; Allan, Anna Y; Kwok, Jessica C; Roet, Kasper C D; Verhaagen, Joost; Schneider, Bernard L; Bensadoun, Jean-Charles; Ahmed, Sherif G; Yáñez-Muñoz, Rafael J; Keynes, Roger J; Fawcett, James W; Rogers, John H

    2011-09-30

    Several diseases and injuries of the central nervous system could potentially be treated by delivery of an enzyme, which might most effectively be achieved by gene therapy. In particular, the bacterial enzyme chondroitinase ABC is beneficial in animal models of spinal cord injury. We have adapted the chondroitinase gene so that it can direct secretion of active chondroitinase from mammalian cells, and inserted it into lentiviral vectors. When injected into adult rat brain, these vectors lead to extensive secretion of chondroitinase, both locally and from long-distance axon projections, with activity persisting for more than 4 weeks. In animals which received a simultaneous lesion of the corticospinal tract, the vector reduced axonal die-back and promoted sprouting and short-range regeneration of corticospinal axons. The same beneficial effects on damaged corticospinal axons were observed in animals which received the chondroitinase lentiviral vector directly into the vicinity of a spinal cord lesion.

  4. Chemokines and Chemokine Receptors in Multiple Sclerosis

    Directory of Open Access Journals (Sweden)

    Wenjing Cheng

    2014-01-01

    Full Text Available Multiple sclerosis is an autoimmune disease with classical traits of demyelination, axonal damage, and neurodegeneration. The migration of autoimmune T cells and macrophages from blood to central nervous system as well as the destruction of blood brain barrier are thought to be the major processes in the development of this disease. Chemokines, which are small peptide mediators, can attract pathogenic cells to the sites of inflammation. Each helper T cell subset expresses different chemokine receptors so as to exert their different functions in the pathogenesis of MS. Recently published results have shown that the levels of some chemokines and chemokine receptors are increased in blood and cerebrospinal fluid of MS patients. This review describes the advanced researches on the role of chemokines and chemokine receptors in the development of MS and discusses the potential therapy of this disease targeting the chemokine network.

  5. SNTF immunostaining reveals previously undetected axonal pathology in traumatic brain injury.

    Science.gov (United States)

    Johnson, Victoria E; Stewart, William; Weber, Maura T; Cullen, D Kacy; Siman, Robert; Smith, Douglas H

    2016-01-01

    Diffuse axonal injury (DAI) is a common feature of severe traumatic brain injury (TBI) and may also be a predominant pathology in mild TBI or "concussion". The rapid deformation of white matter at the instant of trauma can lead to mechanical failure and calcium-dependent proteolysis of the axonal cytoskeleton in association with axonal transport interruption. Recently, a proteolytic fragment of alpha-II spectrin, "SNTF", was detected in serum acutely following mild TBI in patients and was prognostic for poor clinical outcome. However, direct evidence that this fragment is a marker of DAI has yet to be demonstrated in either humans following TBI or in models of mild TBI. Here, we used immunohistochemistry (IHC) to examine for SNTF in brain tissue following both severe and mild TBI. Human severe TBI cases (survival <7d; n = 18) were compared to age-matched controls (n = 16) from the Glasgow TBI archive. We also examined brains from an established model of mild TBI at 6, 48 and 72 h post-injury versus shams. IHC specific for SNTF was compared to that of amyloid precursor protein (APP), the current standard for DAI diagnosis, and other known markers of axonal pathology including non-phosphorylated neurofilament-H (SMI-32), neurofilament-68 (NF-68) and compacted neurofilament-medium (RMO-14) using double and triple immunofluorescent labeling. Supporting its use as a biomarker of DAI, SNTF immunoreactive axons were observed at all time points following both human severe TBI and in the model of mild TBI. Interestingly, SNTF revealed a subpopulation of degenerating axons, undetected by the gold-standard marker of transport interruption, APP. While there was greater axonal co-localization between SNTF and APP after severe TBI in humans, a subset of SNTF positive axons displayed no APP accumulation. Notably, some co-localization was observed between SNTF and the less abundant neurofilament subtype markers. Other SNTF positive axons, however, did not co-localize with any

  6. Fisiopatología del síndrome de Guillain Barré axonal Physiopathology of axonal acute Guillain Barré syndrome

    OpenAIRE

    Juan Guillermo Montoya Ch.; Diana P. Martínez T.; Jaime Carrizosa Moog; Beatriz Aguirre L.

    2002-01-01

    Se describe la fisiopatología del síndrome de Guillain Barré axonal. Se consideran especialmente cinco aspectos: 1) Agentes etiológicos, específicamente el Campylobacter jejuni. 2) Susceptibilidad genética humana. 3) Mimetismo molecular entre lipopolisacáridos y lipoproteínas. 4) Mecanismo de acción de los anticuerpos antigangliósidos y 5) Hallazgos patológicos. The physiopathology of axonal acute Guillain Barré syndrome is described. Five aspects are considered, namely: 1) Etiologic agents e...

  7. Hydrogels as scaffolds and delivery systems to enhance axonal regeneration after injuries

    Directory of Open Access Journals (Sweden)

    Oscar A. Carballo-Molina

    2015-02-01

    Full Text Available Damage caused to neural tissue by disease or injury frequently produces a discontinuity in the nervous system. Such damage generates diverse alterations that are commonly permanent, due to the limited regeneration capacity of the adult nervous system, particularly the Central Nervous System (CNS. The cellular reaction to noxious stimulus leads to several events such as the formation of glial and fibrous scars, which inhibit axonal regeneration in both the CNS and the Peripheral Nervous System (PNS. Although in the PNS there is some degree of nerve regeneration, it is common that the growing axons reinnervate incorrect areas, causing mismatches. Providing a permissive substrate for axonal regeneration in combination with delivery systems for the release of molecules, which enhances axonal growth, could increase regeneration and the recovery of functions in the CNS or the PNS. Currently, there are no effective vehicles to supply growth factors or cells to the damaged/diseased nervous system. Hydrogels are polymers that are biodegradable, biocompatible and have the capacity to deliver a large range of molecules in situ. The inclusion of cultured neural cells into hydrogels forming three-dimensional structures allows the formation of synapses and neuronal survival. There is also evidence showing that hydrogels constitute an amenable substrate for axonal growth of endogenous or grafted cells, overcoming the presence of axonal regeneration inhibitory molecules, in both the central and peripheral nervous systems. Recent experiments suggest that hydrogels can carry and deliver several proteins relevant for improving neuronal survival and axonal growth. Although the use of hydrogels is appealing, its effectiveness is still a matter of discussion, and more results are needed to achieve consistent recovery using different parameters. This review also discusses areas of opportunity where hydrogels can be applied, in order to promote axonal regeneration of

  8. Skin incision induces expression of axonal regeneration-related genes in adult rat spinal sensory neurons

    OpenAIRE

    Hill, Caitlin E.; Harrison, Benjamin J; Rau, Kris K.; Hougland, M. Tyler; Bunge, Mary Bartlett; Lorne M. Mendell; Petruska, Jeffrey C.

    2010-01-01

    Skin incision and nerve injury both induce painful conditions. Incisional and post-surgical pain is believed to arise primarily from inflammation of tissue and the subsequent sensitization of peripheral and central neurons. The role of axonal regeneration-related processes in development of pain has only been considered when there has been injury to the peripheral nerve itself, even though tissue damage likely induces injury of resident axons. We sought to determine if skin incision would aff...

  9. Microtubules Have Opposite Orientation in Axons and Dendrites of Drosophila Neurons

    OpenAIRE

    Stone, Michelle C.; Roegiers, Fabrice; Rolls, Melissa M

    2008-01-01

    In vertebrate neurons, axons have a uniform arrangement of microtubules with plus ends distal to the cell body (plus-end-out), and dendrites have equal numbers of plus- and minus-end-out microtubules. To determine whether microtubule orientation is a conserved feature of axons and dendrites, we analyzed microtubule orientation in invertebrate neurons. Using microtubule plus end dynamics, we mapped microtubule orientation in Drosophila sensory neurons, interneurons, and motor neurons. As expec...

  10. Sustained axon-glial signaling induces Schwann cell hyperproliferation, Remak bundle myelination, and tumorigenesis

    OpenAIRE

    Gómez-Sánchez, José A.; López de Armentia, Mikel; Luján, Rafael; Kessaris, Nicoletta; Richardson, William D.; Cabedo, Hugo

    2009-01-01

    Type III neuregulins exposed on axon surfaces control myelination of the peripheral nervous system. It has been shown, for example, that threshold levels of type IIIβ1a neuregulin dictate not only the myelination fate of axons but also myelin thickness. Here we show that another neuregulin isoform, type III-β3, plays a distinct role in myelination. Neuronal overexpression of this isoform in mice stimulates Schwann cell proliferation and dramatically enlarges peripheral nerves and ganglia -whi...

  11. Axon-Schwann cell interactions during peripheral nerve regeneration in zebrafish larvae

    OpenAIRE

    Ceci, Maria Laura; Mardones-Krsulovic, Camila; SÁNCHEZ, MARIO; Valdivia, Leonardo E.; Allende, Miguel L

    2014-01-01

    Background Peripheral nerve injuries can severely affect the way that animals perceive signals from the surrounding environment. While damage to peripheral axons generally has a better outcome than injuries to central nervous system axons, it is currently unknown how neurons re-establish their target innervations to recover function after injury, and how accessory cells contribute to this task. Here we use a simple technique to create reproducible and localized injury in the posterior lateral...

  12. Purkinje cell axonal anatomy: quantifying morphometric changes in essential tremor versus control brains

    OpenAIRE

    Babij, Rachel; Lee, Michelle; Cortés, Etty; Vonsattel, Jean-Paul G.; Faust, Phyllis L.; Louis, Elan D.

    2013-01-01

    Growing clinical, neuro-imaging and post-mortem data have implicated the cerebellum as playing an important role in the pathogenesis of essential tremor. Aside from a modest reduction of Purkinje cells in some post-mortem studies, Purkinje cell axonal swellings (torpedoes) are present to a greater degree in essential tremor cases than controls. Yet a detailed study of more subtle morphometric changes in the Purkinje cell axonal compartment has not been undertaken. We performed a detailed morp...

  13. Wnt Signalling Promotes Actin Dynamics during Axon Remodelling through the Actin-Binding Protein Eps8.

    Directory of Open Access Journals (Sweden)

    Eleanna Stamatakou

    Full Text Available Upon arrival at their synaptic targets, axons slow down their growth and extensively remodel before the assembly of presynaptic boutons. Wnt proteins are target-derived secreted factors that promote axonal remodelling and synaptic assembly. In the developing spinal cord, Wnts secreted by motor neurons promote axonal remodelling of NT-3 responsive dorsal root ganglia neurons. Axon remodelling induced by Wnts is characterised by growth cone pausing and enlargement, processes that depend on the re-organisation of microtubules. However, the contribution of the actin cytoskeleton has remained unexplored. Here, we demonstrate that Wnt3a regulates the actin cytoskeleton by rapidly inducing F-actin accumulation in growth cones from rodent DRG neurons through the scaffold protein Dishevelled-1 (Dvl1 and the serine-threonine kinase Gsk3β. Importantly, these changes in actin cytoskeleton occurs before enlargement of the growth cones is evident. Time-lapse imaging shows that Wnt3a increases lamellar protrusion and filopodia velocity. In addition, pharmacological inhibition of actin assembly demonstrates that Wnt3a increases actin dynamics. Through a yeast-two hybrid screen, we identified the actin-binding protein Eps8 as a direct interactor of Dvl1, a scaffold protein crucial for the Wnt signalling pathway. Gain of function of Eps8 mimics Wnt-mediated axon remodelling, whereas Eps8 silencing blocks the axon remodelling activity of Wnt3a. Importantly, blockade of the Dvl1-Eps8 interaction completely abolishes Wnt3a-mediated axonal remodelling. These findings demonstrate a novel role for Wnt-Dvl1 signalling through Eps8 in the regulation of axonal remodeling.

  14. Axonal neuregulin 1 is a rate limiting but not essential factor for nerve remyelination

    OpenAIRE

    Fricker, Florence R.; Antunes-Martins, Ana; Galino, Jorge; Paramsothy, Remi; La Russa, Federica; Perkins, James; Goldberg, Rebecca; Brelstaff, Jack; Zhu, Ning; McMahon, Stephen B; Orengo, Christine; Garratt, Alistair N.; Birchmeier, Carmen; David L H Bennett

    2013-01-01

    Neuregulin 1 acts as an axonal signal that regulates multiple aspects of Schwann cell development including the survival and migration of Schwann cell precursors, the ensheathment of axons and subsequent elaboration of the myelin sheath. To examine the role of this factor in remyelination and repair following nerve injury, we ablated neuregulin 1 in the adult nervous system using a tamoxifen inducible Cre recombinase transgenic mouse system. The loss of neuregulin 1 impaired remyelination aft...

  15. Mild hypothermia for treatment of diffuse axonal injury: a quantitative analysis of diffusion tensor imaging

    OpenAIRE

    Jing, Guojie; Yao, Xiaoteng; Li, Yiyi; Xie, Yituan; Li, Wang#x2019;an; LIU, Kejun; Jing, Yingchao; Li, Baisheng; Lv, Yifan; Ma, Baoxin

    2014-01-01

    Fractional anisotropy values in diffusion tensor imaging can quantitatively reflect the consistency of nerve fibers after brain damage, where higher values generally indicate less damage to nerve fibers. Therefore, we hypothesized that diffusion tensor imaging could be used to evaluate the effect of mild hypothermia on diffuse axonal injury. A total of 102 patients with diffuse axonal injury were randomly divided into two groups: normothermic and mild hypothermic treatment groups. Patient's m...

  16. Topographic mapping of the axons of the femoral chordotonal organ neurons in the cricket Gryllus bimaculatus.

    Science.gov (United States)

    Nishino, H

    2000-01-01

    Central projections of the femoral chordotonal organ (FCO) neurons in the cricket Gryllus bimaculatus were investigated by selectively staining small numbers of axons. The FCOs in all legs consist of partly fused ventral and dorsal scoloparia in the proximal femur. The ventral scoloparium neurons can be reliably divided into two groups: the ventral group neurons (VG), which are arranged in a sequentially smaller manner distally, and dorsal group neurons (DG), which simply aggregate in the proximal region near the dorsal scoloparium. All axons of the FCO projected to the ipsilateral half of the respective thoracic ganglion. The VG axons possessed dorso-lateral branches in the motor association neuropile and antero-ventral branches dorso-lateral to the anterior ventral association centre. However, the more proximally the somata were situated, the more medially the main neurites terminated. The DG axons showed some variations: some axons of the distally located neurons possessed dorso-lateral branches and terminated on the boundary region of the mVAC, while the other axons terminated exclusively in the medical ventral association centre (mVAC), including the ventral part, which receives auditory sensory neuron projections. All axons of the dorsal scoloparium neurons projected exclusively into the dorsal part of the mVAC; however, the ventrally located neurons projected more ventrally than did the dorsally located neurons. The above characteristics were nearly identical in the pro- and metathoracic FCOs. These results suggest that the cricket FCO axons are roughly organized in a somatotopic map and are broadly differentiated in their function.

  17. Single rodent mesohabenular axons release glutamate and GABA

    Science.gov (United States)

    Root, David H.; Mejias-Aponte, Carlos; Zhang, Shiliang; Wang, Huiling; Hoffman, Alexander F.; Lupica, Carl R.; Morales, Marisela

    2016-01-01

    The lateral habenula (LHb) is involved in reward, aversion, addiction, and depression, through descending interactions with several brain structures, including the ventral tegmental area (VTA). VTA provides reciprocal inputs to LHb, but their actions are unclear. Here we show that the majority of rat and mouse VTA neurons innervating LHb co-express markers for both glutamate-signaling (vesicular glutamate transporter 2, VGluT2) and GABA-signaling (glutamate decarboxylase, GAD; and vesicular GABA transporter, VGaT). A single axon from these mesohabenular neurons co-expresses VGluT2-protein and VGaT-protein, and surprisingly establishes symmetric and asymmetric synapses on LHb neurons. In LHb slices, light activation of mesohabenular fibers expressing channelrhodopsin-2 (ChR2) driven by VGluT2 or VGaT promoters elicits release of both glutamate and GABA onto single LHb neurons. In vivo light-activation of mesohabenular terminals inhibits or excites LHb neurons. Our findings reveal an unanticipated type of VTA neuron that co-transmits glutamate and GABA, and provides the majority of mesohabenular inputs. PMID:25242304

  18. Bridging Physics and Biology Using Resistance and Axons

    Science.gov (United States)

    Dyer, Joshua M.

    2014-11-01

    When teaching physics, it is often difficult to get biology-oriented students to see the relevance of physics.1 A complaint often heard is that biology students are required to take physics for the Medical College Admission Test (MCAT) as part of a "weeding out" process, but that they don't feel like they need physics for biology. Despite this impression held by students, there have been calls for better physics education for future physicians and life scientists.2,3 Research is being performed to improve physics classes and labs by linking topics in biology and physics.4,5 Described here is a laboratory experiment covering the topics of resistance of materials and circuits/Kirchhoff's laws in a biology context with their direct application to neurons, axons, and electrical impulse transmission within animals. This experiment will also demonstrate the mechanism believed to cause multiple sclerosis. The apparatus was designed with low-cost and readily available materials in mind.

  19. Sodium movements in perfused squid giant axons. Passive fluxes.

    Science.gov (United States)

    Rojas, E; Canessa-Fischer, M

    1968-08-01

    Sodium movements in internally perfused giant axons from the squid Dosidicus gigas were studied with varying internal sodium concentrations and with fluoride as the internal anion. It was found that as the internal concentration of sodium was increased from 2 to 200 mM the resting sodium efflux increased from 0.09 to 34.0 pmoles/cm(2)sec and the average resting sodium influx increased from 42.9 to 64.5 pmoles/cm(2)sec but this last change was not statistically significant. When perfusing with a mixture of 500 mM K glutamate and 100 mM Na glutamate the resting efflux was 10 +/- 3 pmoles/cm(2)sec and 41 +/- 10 pmoles/cm(2)sec for sodium influx. Increasing the internal sodium concentration also increased both the extra influx and the extra efflux of sodium due to impulse propagation. At any given internal sodium concentration the net extra influx was about 5 pmoles/cm(2)impulse. This finding supports the notion that the inward current generated in a propagated action potential can be completely accounted for by movements of sodium. PMID:5672003

  20. 76 FR 63676 - Final Division of Safety Systems Interim Staff Guidance DSS-ISG-2010-01: Staff Guidance Regarding...

    Science.gov (United States)

    2011-10-13

    ... COMMISSION Final Division of Safety Systems Interim Staff Guidance DSS-ISG- 2010-01: Staff Guidance Regarding... final Division of Safety Systems Interim Staff Guidance, (DSS-ISG) DSS- ISG-2010-01, ``Staff Guidance... guidance to the NRC staff reviewer to address the increased complexity of recent spent fuel pool...

  1. Human bone marrow mesenchymal stem cell transplantation attenuates axonal injur y in stroke rats

    Institute of Scientific and Technical Information of China (English)

    Yi Xu; Shiwei Du; Xinguang Yu; Xiao Han; Jincai Hou; Hao Guo

    2014-01-01

    Previous studies have shown that transplantation of human bone marrow mesenchymal stem cells promotes neural functional recovery after stroke, but the neurorestorative mechanisms remain largely unknown. We hypothesized that functional recovery of myelinated axons may be one of underlying mechanisms. In this study, an ischemia/reperfusion rat model was established using the middle cerebral artery occlusion method. Rats were used to test the hypothesis that in-travenous transplantation of human bone marrow mesenchymal stem cells through the femoral vein could exert neuroprotective effects against cerebral ischemia via a mechanism associated with the ability to attenuate axonal injury. The results of behavioral tests, infarction volume analysis and immunohistochemistry showed that cerebral ischemia caused severe damage to the myelin sheath and axons. After rats were intravenously transplanted with human bone marrow mesenchymal stem cells, the levels of axon and myelin sheath-related proteins, including mi-crotubule-associated protein 2, myelin basic protein, and growth-associated protein 43, were elevated, infarct volume was decreased and neural function was improved in cerebral ischemic rats. These ifndings suggest that intravenously transplanted human bone marrow mesenchymal stem cells promote neural function. Possible mechanisms underlying these beneifcial effects in-clude resistance to demyelination after cerebral ischemia, prevention of axonal degeneration, and promotion of axonal regeneration.

  2. Enzyme-instructed self-assembly of taxol promotes axonal branching.

    Science.gov (United States)

    Mei, Bin; Miao, Qingqing; Tang, Anming; Liang, Gaolin

    2015-10-14

    Axonal branching is important for vertebrate neuron signaling. Taxol has a biphasic effect on axonal branching (i.e., high concentration inhibits axonal growth but low concentration restores it). To the best of our knowledge, low concentration of taxol to promote axonal branching has not been reported yet. Herein, we rationally designed a taxol derivative Fmoc-Phe-Phe-Lys(taxol)-Tyr(H2PO4)-OH (1) which could be subjected to alkaline phosphatase (ALP)-catalyzed self-assembly to form taxol nanofibers. We found that, at 10 μM, 1 has a microtubule (MT) condensation effect similar to that of taxol on mammalian cells but with more chronic toxicity than taxol on the cells. At a low concentration of 10 nM, 1 not only promoted neurite elongation as taxol did but also promoted axonal branching which was not achieved by using taxol. We propose that self-assembly of 1 along the MTs prohibited their lateral contacts and thus promoted axonal branching. Our strategy of enzyme-instructed self-assembly (EISA) of a taxol derivative provides a new tool for scientists to study the morphology of neurons, as well as their behaviours. PMID:26359218

  3. Matrine protects neuro-axon from CNS inflammation-induced injury.

    Science.gov (United States)

    Kan, Quan-Cheng; Lv, Peng; Zhang, Xiao-Jian; Xu, Yu-Ming; Zhang, Guang-Xian; Zhu, Lin

    2015-02-01

    Neuro-axonal injury in the central nervous system (CNS) is one of the major pathological hallmarks of experimental autoimmune encephalomyelitis (EAE), an experimental model of multiple sclerosis (MS). Matrine (MAT), a quinolizidine alkaloid derived from the herb Radix Sophorae Flave, has recently been shown to effectively suppress EAE through an anti-inflammatory mechanism. However, whether MAT can also protect myelin/axons from damage is not known. In the present study we show that, while untreated rats developed severe clinical disease, CNS inflammatory demyelination, and axonal damage, these clinical and pathological signs were significantly reduced by MAT treatment. Consistently, MAT treatment reduced the concentration of myelin basic protein in serum and downregulated expression of β-amyloid (Aβ) and B-site APP cleaving enzyme 1 (BACE-1) in the CNS. Further, the CNS of MAT-treated rats exhibited increased expression of brain-derived neurotrophic factor (BDNF), an important factor for neuronal survival and axonal growth. Together, these results demonstrate that MAT effectively prevented neuro-axonal injury, which can likely be attributed to inhibiting risk factors such as BACE-1 and upregulating neuroprotective factors such as BDNF. We conclude that this novel natural reagent, MAT, which effectively protects neuro-axons from CNS inflammation-induced damage, could be a potential candidate for the treatment of neurodegenerative diseases such as MS.

  4. Propagation of action potentials along complex axonal trees. Model and implementation.

    Science.gov (United States)

    Manor, Y; Gonczarowski, J; Segev, I

    1991-01-01

    Axonal trees are typically morphologically and physiologically complicated structures. Because of this complexity, axonal trees show a large repertoire of behavior: from transmission lines with delay, to frequency filtering devices in both temporal and spatial domains. Detailed theoretical exploration of the electrical behavior of realistically complex axonal trees is notably lacking, mainly because of the absence of a simple modeling tool. AXONTREE is an attempt to provide such a simulator. It is written in C for the SUN workstation and implements both a detailed compartmental modeling of Hodgkin and Huxley-like kinetics, and a more abstract, event-driven, modeling approach. The computing module of AXONTREE is introduced together with its input/output features. These features allow graphical construction of arbitrary trees directly on the computer screen, and superimposition of the results on the simulated structure. Several numerical improvements that increase the computational efficiency by a factor of 5-10 are presented; most notable is a novel method of dynamic lumping of the modeled tree into simpler representations ("equivalent cables"). AXONTREE's performance is examined using a reconstructed terminal of an axon from a Y cell in cat visual cortex. It is demonstrated that realistically complicated axonal trees can be handled efficiently. The application of AXONTREE for the study of propagation delays along axonal trees is presented in the companion paper (Manor et al., 1991). Images FIGURE 4 PMID:1777566

  5. BDNF promotes target innervation of Xenopus mandibular trigeminal axons in vivo

    Directory of Open Access Journals (Sweden)

    Ishibashi Shoko

    2007-05-01

    Full Text Available Abstract Background Trigeminal nerves consist of ophthalmic, maxillary, and mandibular branches that project to distinct regions of the facial epidermis. In Xenopus embryos, the mandibular branch of the trigeminal nerve extends toward and innervates the cement gland in the anterior facial epithelium. The cement gland has previously been proposed to provide a short-range chemoattractive signal to promote target innervation by mandibular trigeminal axons. Brain derived neurotrophic factor, BDNF is known to stimulate axon outgrowth and branching. The goal of this study is to determine whether BDNF functions as the proposed target recognition signal in the Xenopus cement gland. Results We found that the cement gland is enriched in BDNF mRNA transcripts compared to the other neurotrophins NT3 and NT4 during mandibular trigeminal nerve innervation. BDNF knockdown in Xenopus embryos or specifically in cement glands resulted in the failure of mandibular trigeminal axons to arborise or grow into the cement gland. BDNF expressed ectodermal grafts, when positioned in place of the cement gland, promoted local trigeminal axon arborisation in vivo. Conclusion BDNF is necessary locally to promote end stage target innervation of trigeminal axons in vivo, suggesting that BDNF functions as a short-range signal that stimulates mandibular trigeminal axon arborisation and growth into the cement gland.

  6. Synaptic gating at axonal branches, and sharp-wave ripples with replay: a simulation study.

    Science.gov (United States)

    Vladimirov, Nikita; Tu, Yuhai; Traub, Roger D

    2013-11-01

    Mechanisms of place cell replay occurring during sharp-wave ripples (SPW-Rs) remain obscure due to the fact that ripples in vitro depend on non-synaptic mechanisms, presumably via axo-axonal gap junctions between pyramidal cells. We suggest a model of in vivo SPW-Rs in which synaptic excitatory post-synaptic potentials (EPSPs) control the axonal spiking of cells in SPW-Rs: ripple activity remains hidden in the network of axonal collaterals (connected by gap junctions) due to conduction failures, unless there is a sufficient dendritic EPSP. The EPSP brings the axonal branching point to threshold, and action potentials from the collateral start to propagate to the soma and to the distal axon. The model coherently explains multiple experimental data on SPW-Rs, both in vitro and in vivo. The mechanism of synaptic gating leads to the following implication: a sequence of pyramidal cells can be replayed at ripple frequency by the superposition of subthreshold dendritic EPSPs and ripple activity in the axonal plexus. Replay is demonstrated in both forward and reverse directions. We discuss several testable predictions. In general, the mechanism of synaptic gating suggests that pyramidal cells under certain conditions can act like a transistor.

  7. Extra-neurohypophyseal axonal projections from individual vasopressin-containing magnocellular neurons in rat hypothalamus

    Directory of Open Access Journals (Sweden)

    Vito Salvador Hernandez

    2015-10-01

    Full Text Available Conventional neuroanatomical, immunohistochemical techniques and electrophysiological recording, as well as in vitro labeling methods may fail to detect long range extra-neurohypophyseal-projecting axons from vasopressin (AVP-containing magnocellular neurons (magnocells in the hypothalamic paraventricular nucleus (PVN. Here, we used in vivo extracellular recording, juxtacellular labeling, post hoc anatomo-immunohistochemical analysis and camera lucida reconstruction to address this question. We demonstrate that all well-labeled AVP immunopositive neurons inside the PVN possess main axons joining the tract of Greving and multi-axon-like processes, as well as axonal collaterals branching very near to the somata, which project to extra-neurohypophyseal regions. The detected regions in this study include the medial and lateral preoptical area, suprachiasmatic nucleus, lateral habenula, medial and central amygdala and the conducting systems, such as stria medullaris, the fornix and the internal capsule. Expression of vesicular glutamate transporter 2 was observed in axon-collaterals. These results, in congruency with several previous reports in the literature, provided unequivocal evidence that AVP magnocells have an uncommon feature of possessing multiple axon-like processes emanating from somata or proximal dendrites. Furthermore, the long-range non-neurohypophyseal projections are more common than an occasional phenomenon as previously thought.

  8. Augmented Reality Repair Guidance System

    Directory of Open Access Journals (Sweden)

    Sidharth Bhatia

    2012-07-01

    Full Text Available The daily life of a common man revolves around various forms of appliances/gadgets he uses throughout the day such as a mobile phone, laptop, printer, microwave oven, washing machine, etc. Although these appliances/gadgets are taken by most of the people for granted, the problem occurs when any of these things do not work as they are expected to. Getting them to the repair shops for every small glitch is expensive as well as time consuming. Although most of the companies which produce these appliances/gadgets do supply them with basic manuals, which deal with how to solve these minor issues, but reading them and at the same time repairing the corresponding appliance/gadget can be a frustrating task at times. These problems can be reduced to a large extent if some kind of live guidance is available. In this paper we propose a method to do so with the help of an augmented reality based system that will guide the user to carry out small scale repair jobs on these gadgets. All that is required is a decent webcam and a computing device, with a processor of 1 GHz or more and a display screen.

  9. Two different immunostaining patterns of beta-amyloid precursor protein (APP) may distinguish traumatic from nontraumatic axonal injury.

    Science.gov (United States)

    Hayashi, Takahito; Ago, Kazutoshi; Nakamae, Takuma; Higo, Eri; Ogata, Mamoru

    2015-09-01

    Immunostaining for beta-amyloid precursor protein (APP) is recognized as an effective tool for detecting traumatic axonal injury, but it also detects axonal injury due to ischemic or other metabolic causes. Previously, we reported two different patterns of APP staining: labeled axons oriented along with white matter bundles (pattern 1) and labeled axons scattered irregularly (pattern 2) (Hayashi et al. (Leg Med (Tokyo) 11:S171-173, 2009). In this study, we investigated whether these two patterns are consistent with patterns of trauma and hypoxic brain damage, respectively. Sections of the corpus callosum from 44 cases of blunt head injury and equivalent control tissue were immunostained for APP. APP was detected in injured axons such as axonal bulbs and varicose axons in 24 of the 44 cases of head injuries that also survived for three or more hours after injury. In 21 of the 24 APP-positive cases, pattern 1 alone was observed in 14 cases, pattern 2 alone was not observed in any cases, and both patterns 1 and 2 were detected in 7 cases. APP-labeled injured axons were detected in 3 of the 44 control cases, all of which were pattern 2. These results suggest that pattern 1 indicates traumatic axonal injury, while pattern 2 results from hypoxic insult. These patterns may be useful to differentiate between traumatic and nontraumatic axonal injuries.

  10. State of Washington radiation guidance for Hanford

    International Nuclear Information System (INIS)

    Cleanup of the U.S. Department of Energy's Hanford site is being managed through the Hanford Federal Facility Agreement and Consent Order known as the Tri-Party Agreement. The participants are the U.S. Department of Energy, the U.S. Environmental Protection Agency, and the State of Washington, with the Department of Ecology being the lead for the State of Washington. Through a memorandum of understanding the Department of Health is designated as the primary state agency for protection of human health and the environment from ionizing radiation. As part of this responsibility, the Department of Health is developing radiation cleanup guidance for Hanford cleanup. Another reason for developing State guidance is that there are no federal regulations that provide guidance on residual radioactivity on lands that will be released for public use. The U.S. Nuclear Regulatory Commission and the U.S. Environmental Protection Agency both have prepared draft regulations, but the issuance of these is uncertain. The state guidance is compatible with draft federal guidance and includes numerical guidance for residual contamination, modeling parameters, look-up tables, and land use categories. This guidance will apply until such a time as they are superseded by applicable federal regulations or the state environmental radiation standard

  11. Reproductive steroid receptors and actions in the locus coeruleus of male macaques: Part of an aggression circuit?

    Science.gov (United States)

    Bethea, Cynthia L; Belikova, Yelena; Phu, Kenny; Mammerella, Grace

    2016-11-01

    This study was initiated to determine whether the noradrenergic (NE) neurons of the locus coeruleus (LC) could mediate the stimulatory action of androgens on serotonin-related gene expression in male macaques. These experiments follow our observations that serotonin neurons lack androgen receptors (ARs), and yet respond to androgens. Male Japanese macaques (Macaca fuscata) were castrated for 5-7months and then treated for 3months with [1] placebo, [2] T (testosterone), [3] DHT (dihydrotestosterone; non-aromatizable androgen) plus ATD (steroidal aromatase inhibitor), or [4] FLUT (Flutamide; androgen antagonist) plus ATD (n=5/group). The noradrenergic (NE) innervation of the raphe was determined with immunolabeling of axons with an antibody to dopamine-β-hydroxylase (DBH). Immunolabeling of tyrosine hydroxylase (TH) dendrites and corticotropin releasing hormone (CRH) axons innervating the LC was also determined. Due to the longer treatment period employed, the expression of the cognate nuclear receptors was sought. Androgen receptor (AR), estrogen receptor alpha (ERα) and estrogen receptor beta (ERβ) immunostaining was accomplished. Quantitative image analysis was applied and immunopositive neurons or axons with boutons were measured. Double-label of NE neurons for each receptor plus TH determined whether the receptors were localized in NE neurons. Androgens with or without aromatase activity significantly stimulated DBH axon density in the raphe (ANOVA, p=0.006), and LC dendritic TH (ANOVA, p80% of LC NE neurons contained ERα or ERβ. In conclusion, the LC NE neurons may transduce the stimulatory effect of androgens on serotonin-related gene expression. Since LC NE neurons lack AR, the androgenic stimulation of dendritic TH and axonal DBH may be indirectly mediated by other neurons. Estrogen, either from metabolism of T or from de novo synthesis, appears necessary for robust CRH innervation of the LC, which differs from female macaques. PMID:27083854

  12. Comparison of electrical responses of terminals, axons, and somata of a peptidergic neurosecretory system.

    Science.gov (United States)

    Nagano, M; Cooke, I M

    1987-03-01

    Spontaneous and evoked electrical activity was recorded intracellularly from somata, axons, and terminal dilatations of an isolated peptidergic neurosecretory system, the X-organ-sinus gland, of the crabs Cardisoma carnifex and Podophthalmus vigil in order to compare their electrical characteristics. Spontaneous impulse activity was present in most penetrations and included irregular and pacemaker-like firing, as well as patterned activity (bursting). Extracellular recording showed that spontaneous impulses and bursting originate in a proximal region of the axon tract. Somata vary from being electrically nonresponsive to having overshooting impulses with a relatively slow rate of rise. Overshooting impulses were consistently recorded from axons and terminals. Regional differences include (1) a longer action potential duration in terminals, (2) ability of axons and terminals but not somata to sustain repetitive firing, (3) presence of depolarizing afterpotentials in axons but of hyperpolarizing afterpotentials in somata and terminals, and (4) occurrence of impulse broadening during repetitive firing in some terminals but not in axons or somata. Somata and terminals sustained reduced and slowed, but regenerative impulses in nominally Na-free saline and showed alterations of waveform in nominally Ca-free salines, while axons showed no regenerative responses in Na-free saline and no change of impulse form in Ca-free saline. Terminal responses in the presence of tetraethylammonium chloride (TEA) (50 mM) or Ba (50 mM) exhibited long depolarized plateaus, while impulses of somata were much less prolonged. Bursts often took the form of impulses superimposed on a depolarized plateau. Bursts could be evoked by single stimuli applied to the axon tract but not by current passed intracellularly. After addition of TTX, axon tract stimulation evoked plateaus without superimposed impulses. Terminals exhibit specialization of their electrical responses by comparison to axons and

  13. p250GAP is a novel player in the Cdh1-APC/Smurf1 pathway of axon growth regulation.

    Directory of Open Access Journals (Sweden)

    Madhuvanthi Kannan

    Full Text Available Axon growth is an essential process during brain development. The E3 ubiquitin ligase Cdh1-APC has emerged as a critical regulator of intrinsic axon growth control. Here, we identified the RhoGAP p250GAP as a novel interactor of the E3 ubiquitin ligase Cdh1-APC and found that p250GAP promotes axon growth downstream of Cdh1-APC. We also report that p250GAP undergoes non-proteolytic ubiquitination and associates with the Cdh1 substrate Smurf1 to synergistically regulate axon growth. Finally, we found that in vivo knockdown of p250GAP in the developing cerebellar cortex results in impaired migration and axonal growth. Taken together, our data indicate that Cdh1-APC together with the RhoA regulators p250GAP and Smurf1 controls axon growth in the mammalian brain.

  14. Sustainability guidance pack for suppliers: May 2011

    OpenAIRE

    2013-01-01

    This document provides guidance on specific sustainability topics to inform and support suppliers in meeting sustainability obligations. Suppliers are any organisation providing services, overlay and equipment for or on behalf of LOCOG, including at venues.

  15. Integrated Entry Guidance for Reusable Launch Vehicle

    Institute of Scientific and Technical Information of China (English)

    NING Guo-dong; ZHANG Shu-guang; FANG Zhen-ping

    2007-01-01

    A method for the implementation of integrated three-degree-of-freedom constrained entry guidance for reusable launch vehicle is presented. Given any feasible entry conditions, terminal area energy management interface conditions, and the reference trajectory generated onboard then, the method can generate a longitudinal guidance profile rapidly, featuring linear quadratic regular method and a proportional-integral-derivative tracking law with time-varying gains, which satisfies all the entry corridor constraints and meets the requirements with high precision. Afterwards, by utilizing special features of crossrange parameter, establishing bank-reversal corridor,and determining bank-reversals according to dynamically adjusted method, the algorithm enables the lateral entry guidance system to fly a wide range of missions and provides reliable and good performance in the presence of significant aerodynamic modeling uncertainty.Fast trajectory guidance profiles and simulations with a reusable launch vehicle model for various missions and aerodynamic uncertainties are presented to demonstrate the capacity and reliability of this method.

  16. The Guidance Clinic - An Alternative to Suspension

    Science.gov (United States)

    Stiavelli, Richard E.; Sykes, Dudley E.

    1972-01-01

    A guidance clinic program for disruptive students, based on behavior modification theory and positive reinforcement, has proven effective in dealing with junior and senior high school students who ordinarily would be suspended or excluded from school. (AN)

  17. 7 CFR 1794.7 - Guidance.

    Science.gov (United States)

    2010-01-01

    ... Analysis, Stop 1522, 1400 Independence Avenue, SW., Washington, DC 20250-1522. (b) Water and waste program... appropriate State Director. State Directors may provide supplemental guidance to meet state and local laws...

  18. Drill machine guidance using natural occurring radiation

    International Nuclear Information System (INIS)

    A drilling machine guidance system is described which uses only the naturally occuring radiation within the seam or stratum of interest. The apparatus can be used for guiding horizontal drilling machines through coal seams and the like. (U.K.)

  19. RCRA Programmatic Information Policy and Guidance

    Data.gov (United States)

    U.S. Environmental Protection Agency — This asset includes program policy and guidance documents that are used by the EPA regions, states, tribes and private parties to implement the hazardous waste...

  20. Axonal patterns and targets of dA1 interneurons in the chick hindbrain.

    Science.gov (United States)

    Kohl, Ayelet; Hadas, Yoav; Klar, Avihu; Sela-Donenfeld, Dalit

    2012-04-25

    Hindbrain dorsal interneurons that comprise the rhombic lip relay sensory information and coordinate motor outputs. The progenitor dA1 subgroup of interneurons, which is formed along the dorsal-most region of the caudal rhombic lip, gives rise to the cochlear and precerebellar nuclei. These centers project sensory inputs toward upper-brain regions. The fundamental role of dA1 interneurons in the assembly and function of these brainstem nuclei is well characterized. However, the precise en route axonal patterns and synaptic targets of dA1 interneurons are not clear as of yet. Novel genetic tools were used to label dA1 neurons and trace their axonal trajectories and synaptic connections at various stages of chick embryos. Using dA1-specific enhancers, two contralateral ascending axonal projection patterns were identified; one derived from rhombomeres 6-7 that elongated in the dorsal funiculus, while the other originated from rhombomeres 2-5 and extended in the lateral funiculus. Targets of dA1 axons were followed at later stages using PiggyBac-mediated DNA transposition. dA1 axons were found to project and form synapses in the auditory nuclei and cerebellum. Investigation of mechanisms that regulate the patterns of dA1 axons revealed a fundamental role of Lim-homeodomain (HD) proteins. Switch in the expression of the specific dA1 Lim-HD proteins Lhx2/9 into Lhx1, which is typically expressed in dB1 interneurons, modified dA1 axonal patterns to project along the routes of dB1 subgroup. Together, the results of this research provided new tools and knowledge to the assembly of trajectories and connectivity of hindbrain dA1 interneurons and of molecular mechanisms that control these patterns.

  1. Protein 4.1B contributes to the organization of peripheral myelinated axons.

    Directory of Open Access Journals (Sweden)

    Carmen Cifuentes-Diaz

    Full Text Available Neurons are characterized by extremely long axons. This exceptional cell shape is likely to depend on multiple factors including interactions between the cytoskeleton and membrane proteins. In many cell types, members of the protein 4.1 family play an important role in tethering the cortical actin-spectrin cytoskeleton to the plasma membrane. Protein 4.1B is localized in myelinated axons, enriched in paranodal and juxtaparanodal regions, and also all along the internodes, but not at nodes of Ranvier where are localized the voltage-dependent sodium channels responsible for action potential propagation. To shed light on the role of protein 4.1B in the general organization of myelinated peripheral axons, we studied 4.1B knockout mice. These mice displayed a mildly impaired gait and motility. Whereas nodes were unaffected, the distribution of Caspr/paranodin, which anchors 4.1B to the membrane, was disorganized in paranodal regions and its levels were decreased. In juxtaparanodes, the enrichment of Caspr2, which also interacts with 4.1B, and of the associated TAG-1 and Kv1.1, was absent in mutant mice, whereas their levels were unaltered. Ultrastructural abnormalities were observed both at paranodes and juxtaparanodes. Axon calibers were slightly diminished in phrenic nerves and preterminal motor axons were dysmorphic in skeletal muscle. βII spectrin enrichment was decreased along the axolemma. Electrophysiological recordings at 3 post-natal weeks showed the occurrence of spontaneous and evoked repetitive activity indicating neuronal hyperexcitability, without change in conduction velocity. Thus, our results show that in myelinated axons 4.1B contributes to the stabilization of membrane proteins at paranodes, to the clustering of juxtaparanodal proteins, and to the regulation of the internodal axon caliber.

  2. Network structure implied by initial axon outgrowth in rodent cortex: empirical measurement and models.

    Science.gov (United States)

    Cahalane, Diarmuid J; Clancy, Barbara; Kingsbury, Marcy A; Graf, Ethan; Sporns, Olaf; Finlay, Barbara L

    2011-01-11

    The developmental mechanisms by which the network organization of the adult cortex is established are incompletely understood. Here we report on empirical data on the development of connections in hamster isocortex and use these data to parameterize a network model of early cortical connectivity. Using anterograde tracers at a series of postnatal ages, we investigate the growth of connections in the early cortical sheet and systematically map initial axon extension from sites in anterior (motor), middle (somatosensory) and posterior (visual) cortex. As a general rule, developing axons extend from all sites to cover relatively large portions of the cortical field that include multiple cortical areas. From all sites, outgrowth is anisotropic, covering a greater distance along the medial/lateral axis than along the anterior/posterior axis. These observations are summarized as 2-dimensional probability distributions of axon terminal sites over the cortical sheet. Our network model consists of nodes, representing parcels of cortex, embedded in 2-dimensional space. Network nodes are connected via directed edges, representing axons, drawn according to the empirically derived anisotropic probability distribution. The networks generated are described by a number of graph theoretic measurements including graph efficiency, node betweenness centrality and average shortest path length. To determine if connectional anisotropy helps reduce the total volume occupied by axons, we define and measure a simple metric for the extra volume required by axons crossing. We investigate the impact of different levels of anisotropy on network structure and volume. The empirically observed level of anisotropy suggests a good trade-off between volume reduction and maintenance of both network efficiency and robustness. Future work will test the model's predictions for connectivity in larger cortices to gain insight into how the regulation of axonal outgrowth may have evolved to achieve efficient

  3. Filtration coefficient of the axon membrane as measured with hydrostatic and osmotic methods.

    Science.gov (United States)

    Vargas, F F

    1968-01-01

    The hydraulic conductivity of the membranes surrounding the giant axon of the squid, Dosidicus gigas, was measured. In some axons the axoplasm was partially removed by suction. Perfusion was then established by insertion of a second pipette. In other axons the axoplasm was left intact and only one pipette was inserted. In both groups hydrostatic pressure was applied by means of a water column in a capillary manometer. Displacement of the meniscus in time gave the rate of fluid flowing across the axon sheath. In both groups osmotic differences across the membrane were established by the addition of a test molecule to the external medium which was seawater. The hydraulic conductivity determined by application of hydrostatic pressure was 10.6 +/- 0.8.10(-8) cm/sec cm H(2)O in perfused axons and 3.2 +/- 0.6.10(-8) cm/sec cm H(2)O in intact axons. When the driving force was an osmotic pressure gradient the conductivity was 4.5 +/- 0.6 x 10(-10) cm/sec cm H(2)O and 4.8 +/- 0.9 x 10(-10) cm/sec cm H(2)O in perfused and intact axons, respectively. A comparable result was found when the internal solution was made hyperosmotic. The fluid flow was a linear function of the hydrostatic pressure up to 70 cm of water. Glycerol outflux and membrane conductance were increased 1.6 and 1.1 times by the application of hydrostatic pressure. These increments do not give an explanation of the difference between the filtration coefficients. Other possible explanations are suggested and discussed. PMID:5642470

  4. Rescuing axons from degeneration does not affect retinal ganglion cell death

    Directory of Open Access Journals (Sweden)

    S. de Lima

    2016-01-01

    Full Text Available After a traumatic injury to the central nervous system, the distal stumps of axons undergo Wallerian degeneration (WD, an event that comprises cytoskeleton and myelin breakdown, astrocytic gliosis, and overexpression of proteins that inhibit axonal regrowth. By contrast, injured neuronal cell bodies show features characteristic of attempts to initiate the regenerative process of elongating their axons. The main molecular event that leads to WD is an increase in the intracellular calcium concentration, which activates calpains, calcium-dependent proteases that degrade cytoskeleton proteins. The aim of our study was to investigate whether preventing axonal degeneration would impact the survival of retinal ganglion cells (RGCs after crushing the optic nerve. We observed that male Wistar rats (weighing 200-400 g; n=18 treated with an exogenous calpain inhibitor (20 mM administered via direct application of the inhibitor embedded within the copolymer resin Evlax immediately following optic nerve crush showed a delay in the onset of WD. This delayed onset was characterized by a decrease in the number of degenerated fibers (P<0.05 and an increase in the number of preserved fibers (P<0.05 4 days after injury. Additionally, most preserved fibers showed a normal G-ratio. These results indicated that calpain inhibition prevented the degeneration of optic nerve fibers, rescuing axons from the process of axonal degeneration. However, analysis of retinal ganglion cell survival demonstrated no difference between the calpain inhibitor- and vehicle-treated groups, suggesting that although the calpain inhibitor prevented axonal degeneration, it had no effect on RGC survival after optic nerve damage.

  5. The C-terminal binding protein (CTBP-1) regulates dorsal SMD axonal morphology in Caenorhabditis elegans.

    Science.gov (United States)

    Reid, A; Sherry, T J; Yücel, D; Llamosas, E; Nicholas, H R

    2015-12-17

    C-terminal binding proteins (CtBPs) are transcriptional co-repressors which cooperate with a variety of transcription factors to repress gene expression. Caenorhabditis elegans CTBP-1 expression has been observed in the nervous system and hypodermis. In C. elegans, CTBP-1 regulates several processes including Acute Functional Tolerance to ethanol and functions in the nervous system to modulate both lifespan and expression of a lipase gene called lips-7. Incorrect structure and/or function of the nervous system can lead to behavioral changes. Here, we demonstrate reduced exploration behavior in ctbp-1 mutants. Our examination of a subset of neurons involved in regulating locomotion revealed that the axonal morphology of dorsal SMD (SMDD) neurons is altered in ctbp-1 mutants at the fourth larval (L4) stage. Expressing CTBP-1 under the control of the endogenous ctbp-1 promoter rescued both the exploration behavior phenotype and defective SMDD axon structure in ctbp-1 mutants at the L4 stage. Interestingly, the pre-synaptic marker RAB-3 was found to localize to the mispositioned portion of SMDD axons in a ctbp-1 mutant. Further analysis of SMDD axonal morphology at days 1, 3 and 5 of adulthood revealed that the number of ctbp-1 mutants showing an SMDD axonal morphology defect increases in early adulthood and the observed defect appears to be qualitatively more severe. CTBP-1 is prominently expressed in the nervous system with weak expression detected in the hypodermis. Surprisingly, solely expressing CTBP-1a in the nervous system or hypodermis did not restore correct SMDD axonal structure in a ctbp-1 mutant. Our results demonstrate a role for CTBP-1 in exploration behavior and the regulation of SMDD axonal morphology in C. elegans.

  6. Short-term peripheral nerve stimulation ameliorates axonal dysfunction after spinal cord injury.

    Science.gov (United States)

    Lee, Michael; Kiernan, Matthew C; Macefield, Vaughan G; Lee, Bonne B; Lin, Cindy S-Y

    2015-05-01

    There is accumulating evidence that peripheral motor axons deteriorate following spinal cord injury (SCI). Secondary axonal dysfunction can exacerbate muscle atrophy, contribute to peripheral neuropathies and neuropathic pain, and lead to further functional impairment. In an attempt to ameliorate the adverse downstream effects that developed following SCI, we investigated the effects of a short-term peripheral nerve stimulation (PNS) program on motor axonal excitability in 22 SCI patients. Axonal excitability studies were undertaken in the median and common peroneal nerves (CPN) bilaterally before and after a 6-wk unilateral PNS program. PNS was delivered percutaneously over the median nerve at the wrist and CPN around the fibular head, and the compound muscle action potential (CMAP) from the abductor pollicis brevis and tibialis anterior was recorded. Stimulus intensity was above motor threshold, and pulses (450 μs) were delivered at 100 Hz with a 2-s on/off cycle for 30 min 5 days/wk. SCI patients had consistently high thresholds with a reduced CMAP consistent with axonal loss; in some patients the peripheral nerves were completely inexcitable. Nerve excitability studies revealed profound changes in membrane potential, with a "fanned-in" appearance in threshold electrotonus, consistent with membrane depolarization, and significantly reduced superexcitability during the recovery cycle. These membrane dysfunctions were ameliorated after 6 wk of PNS, which produced a significant hyperpolarizing effect. The contralateral, nonstimulated nerves remained depolarized. Short-term PNS reversed axonal dysfunction following SCI, may provide an opportunity to prevent chronic changes in axonal and muscular function, and may improve rehabilitation outcomes. PMID:25787956

  7. Vocational guidance: origin, evolution and current state

    OpenAIRE

    Di Doménico, Cristina; Vilanova, Alberto

    2000-01-01

    The socio-professional sources of the vocational guidance are reviwed, in the world and in Latin America. It stands out that psychology, as science and as a profession, possesses vigorous links to this practice that, however, tends to its epistemic and praxic emancipation in some nations. The contemporary prob- lems of the guidance are presented in their economic, politics, cultural and pro-fessional dimensions.

  8. ROUTE PLAN DESIGNER FOR TRACTOR GUIDANCE SYSTEMS

    DEFF Research Database (Denmark)

    Sveistrup, Daniel; Jørgensen, Rasmus Nyholm; Green, Ole;

    2010-01-01

    Earlier works have shown field trial designs to be very labor extensive, even when combining autoguidancesystems with conventional machinery.Designing routes for semi-automated systems in a controlled manner is both resource demandingand complicated. Different types of auto-guidance systems vary...... was outlined, it took less thanone hour entering the design into the software and generating the auto-guidance files.KeywordsGIS, Auto steering systems, plot trial design, full-scale field trials, Java...

  9. Axon degeneration and PGC-1α-mediated protection in a zebrafish model of α-synuclein toxicity

    Directory of Open Access Journals (Sweden)

    Kelley C. O’Donnell

    2014-05-01

    Full Text Available α-synuclein (aSyn expression is implicated in neurodegenerative processes, including Parkinson’s disease (PD and dementia with Lewy bodies (DLB. In animal models of these diseases, axon pathology often precedes cell death, raising the question of whether aSyn has compartment-specific toxic effects that could require early and/or independent therapeutic intervention. The relevance of axonal pathology to degeneration can only be addressed through longitudinal, in vivo monitoring of different neuronal compartments. With current imaging methods, dopaminergic neurons do not readily lend themselves to such a task in any vertebrate system. We therefore expressed human wild-type aSyn in zebrafish peripheral sensory neurons, which project elaborate superficial axons that can be continuously imaged in vivo. Axonal outgrowth was normal in these neurons but, by 2 days post-fertilization (dpf, many aSyn-expressing axons became dystrophic, with focal varicosities or diffuse beading. Approximately 20% of aSyn-expressing cells died by 3 dpf. Time-lapse imaging revealed that focal axonal swelling, but not overt fragmentation, usually preceded cell death. Co-expressing aSyn with a mitochondrial reporter revealed deficits in mitochondrial transport and morphology even when axons appeared overtly normal. The axon-protective protein Wallerian degeneration slow (WldS delayed axon degeneration but not cell death caused by aSyn. By contrast, the transcriptional coactivator PGC-1α, which has roles in the regulation of mitochondrial biogenesis and reactive-oxygen-species detoxification, abrogated aSyn toxicity in both the axon and the cell body. The rapid onset of axonal pathology in this system, and the relatively moderate degree of cell death, provide a new model for the study of aSyn toxicity and protection. Moreover, the accessibility of peripheral sensory axons will allow effects of aSyn to be studied in different neuronal compartments and might have utility in

  10. Axonal transport and incorporation of radioactivity after injection of N-[3H]acetyl-D-mannosamine into rat mesencephalon

    International Nuclear Information System (INIS)

    A study has been performed to demonstrate the possibility of incorporation of sialic acid into nerve endings of the rubrospinal tract after antegrade axonal transport. Young adult rats received injections of N-[3H]acetyl-D-mannosamine into the red nucleus and axonal transport of the tritiated compounds along the axons of afferent and efferent connections of the red nucleus was studied and the transported material was analysed. Light microscopic autoradiography and biochemical methods were used. (Auth./C.F.)

  11. A Purine-Sensitive Pathway Regulates Multiple Genes Involved in Axon Regeneration in Goldfish Retinal Ganglion Cells

    OpenAIRE

    Petrausch, Barbara; Tabibiazar, Raymond; Roser, Timo; Jing, Yun; Goldmann, Daniel; Stürmer, Claudia; Irwin, Nina; Benowitz, Larry I.

    2000-01-01

    In lower vertebrates, retinal ganglion cells (RGCs) can regenerate their axons and reestablish functional connections after optic nerve injury. We show here that in goldfish RGCs, the effects of several trophic factors converge on a purine-sensitive signaling mechanism that controls axonal outgrowth and the expression of multiple growth-associated proteins. In culture, goldfish RGCs regenerate their axons in response to two molecules secreted by optic nerve glia, axogenesis factor-1 (AF-1) an...

  12. The contributions of myelin and axonal caliber to transverse relaxation time in shiverer and neurofilament-deficient mouse models

    OpenAIRE

    Dyakin, Victor V.; Chen, Yuanxin; Branch, Craig A.; Veeranna; Yuan, Aidong; Rao, Mala; Kumar, Asok; Peterhoff, Corrinne M.; Nixon, Ralph A

    2010-01-01

    White matter disorders can involve injury to myelin or axons but the respective contribution of each to clinical course is difficult to evaluate non-invasively. Here, to develop a paradigm for further investigations of axonal pathology by MRI, we compared two genetic mouse models exhibiting relatively selective axonal or myelin deficits using quantitative MRI relaxography of the transverse relaxation times (T2) in vivo and ultrastructural morphometry. In HM-DKO mice, which lack genes encoding...

  13. L-carnitine enhances axonal plasticity and improves white-matter lesions after chronic hypoperfusion in rat brain

    OpenAIRE

    Ueno, Yuji; Koike, Masato; Shimada, Yoshiaki; Shimura, Hideki; Hira, Kenichiro; Tanaka, Ryota; Uchiyama, Yasuo; Hattori, Nobutaka; Urabe, Takao

    2014-01-01

    Chronic cerebral hypoperfusion causes white-matter lesions (WMLs) with oxidative stress and cognitive impairment. However, the biologic mechanisms that regulate axonal plasticity under chronic cerebral hypoperfusion have not been fully investigated. Here, we investigated whether L-carnitine, an antioxidant agent, enhances axonal plasticity and oligodendrocyte expression, and explored the signaling pathways that mediate axonal plasticity in a rat chronic hypoperfusion model. Adult male Wistar ...

  14. Ion channel clustering at the axon initial segment and node of Ranvier evolved sequentially in early chordates.

    OpenAIRE

    Hill, Alexis S.; Atsuo Nishino; Koichi Nakajo; Giuxin Zhang; Fineman, Jaime R.; Selzer, Michael E.; Yasushi Okamura; Cooper, Edward C.

    2008-01-01

    In many mammalian neurons, dense clusters of ion channels at the axonal initial segment and nodes of Ranvier underlie action potential generation and rapid conduction. Axonal clustering of mammalian voltage-gated sodium and KCNQ (Kv7) potassium channels is based on linkage to the actin–spectrin cytoskeleton, which is mediated by the adaptor protein ankyrin-G. We identified key steps in the evolution of this axonal channel clustering. The anchor motif for sodium channel clustering evolved earl...

  15. Brain-derived neurotrophic factor gene transfection promotes neuronal repair and neurite regeneration after diffuse axonal injury

    Institute of Scientific and Technical Information of China (English)

    Yin Yu; Chao Du; Xingli Zhao; Jiajia Shao; Qiang Shen; Tao Jiang; Wei Wu; Dong Zhu; Yu Tian; Yongchuan Guo

    2011-01-01

    This study sought to assess the potential of brain-derived neurotrophic factor (BDNF) to promote neuronal repair and regeneration in rats with diffuse axonal injury, and to examine the accompanying neurobiological changes. BDNF gene transfection reduced the severity of the pathological changes associated with diffuse axonal injury in cortical neurons of the frontal lobe and increased neurofilament protein expression. These findings demonstrate that BDNF can effectively promote neuronal repair and neurite regeneration after diffuse axonal injury.

  16. The comparison of the value of ct imaging and selected MRI sequences (including DWI) in the evaluation of axonal injuries

    OpenAIRE

    Paszkowska, Emilia; Wasilewski, Grzegorz; Szalcunas-Olsztyn, Anna; Jancewicz, Patryk; Stefanowicz, Elżbieta

    2010-01-01

    Summary Background: Diffuse axonal injuries of the brain consist in the damage (overstretching or torsion) of white matter axons, as a result of the forces of energy waves, evoked in the moment of injury, together with its accelerating-retarding inertia effect. Patients with DAI are most frequently the casualties of high speed car accidents. Diffuse axonal injuries of the brain are one of the most common acute brain injuries, with lesions typically occurring in the periventricular white matte...

  17. Time-Lapse Imaging of the Dynamics of CNS Glial-Axonal Interactions In Vitro and Ex Vivo

    OpenAIRE

    Kalliopi Ioannidou; Anderson, Kurt I; David Strachan; Edgar, Julia M.; Barnett, Susan C.

    2012-01-01

    Background Myelination is an exquisite and dynamic example of heterologous cell-cell interaction, which consists of the concentric wrapping of multiple layers of oligodendrocyte membrane around neuronal axons. Understanding the mechanism by which oligodendrocytes ensheath axons may bring us closer to designing strategies to promote remyelination in demyelinating diseases. The main aim of this study was to follow glial-axonal interactions over time both in vitro and ex vivo to visualize th...

  18. Differential compartmentalization and distinct functions of GABAB receptor variants

    DEFF Research Database (Denmark)

    Vigot, Réjan; Barbieri, Samuel; Bräuner-Osborne, Hans;

    2006-01-01

    GABAB receptors are the G protein-coupled receptors for the main inhibitory neurotransmitter in the brain, gamma-aminobutyric acid (GABA). Molecular diversity in the GABAB system arises from the GABAB1a and GABAB1b subunit isoforms that solely differ in their ectodomains by a pair of sushi repeats...... release, while predominantly GABAB1b mediates postsynaptic inhibition. Electron microscopy reveals a synaptic distribution of GABAB1 isoforms that agrees with the observed functional differences. Transfected CA3 neurons selectively express GABAB1a in distal axons, suggesting that the sushi repeats, a...

  19. Bergmann glia and the recognition molecule CHL1 organize GABAergic axons and direct innervation of Purkinje cell dendrites.

    Directory of Open Access Journals (Sweden)

    Fabrice Ango

    2008-04-01

    Full Text Available The geometric and subcellular organization of axon arbors distributes and regulates electrical signaling in neurons and networks, but the underlying mechanisms have remained elusive. In rodent cerebellar cortex, stellate interneurons elaborate characteristic axon arbors that selectively innervate Purkinje cell dendrites and likely regulate dendritic integration. We used GFP BAC transgenic reporter mice to examine the cellular processes and molecular mechanisms underlying the development of stellate cell axons and their innervation pattern. We show that stellate axons are organized and guided towards Purkinje cell dendrites by an intermediate scaffold of Bergmann glial (BG fibers. The L1 family immunoglobulin protein Close Homologue of L1 (CHL1 is localized to apical BG fibers and stellate cells during the development of stellate axon arbors. In the absence of CHL1, stellate axons deviate from BG fibers and show aberrant branching and orientation. Furthermore, synapse formation between aberrant stellate axons and Purkinje dendrites is reduced and cannot be maintained, leading to progressive atrophy of axon terminals. These results establish BG fibers as a guiding scaffold and CHL1 a molecular signal in the organization of stellate axon arbors and in directing their dendritic innervation.

  20. Efecto neuroprotector de los cannabinoides sobre la muerte neuronal inducida por Ampa en la médula espinal: Activación conjunta de los receptores CB1 y CB2

    Directory of Open Access Journals (Sweden)

    Carmen Guaza

    2005-03-01

    Full Text Available La sobreactivación de receptores de glutamato, como el receptor AMPA, induce la muerte neural por un proceso denominado excitotoxicidad, el cual ha sido claramente implicado en enfermedades agudas del sistema nerviso central (SNC, particularmente con daño axonal.