Sample records for central amygdaloid axon

  1. NMDA Receptor Agonism and Antagonism within the Amygdaloid Central Nucleus Suppresses Pain Affect: Differential Contribution of the Ventrolateral Periaqueductal Gray (United States)

    Spuz, Catherine A.; Tomaszycki, Michelle L.; Borszcz, George S.


    The amygdala contributes to the generation of pain affect and the amygdaloid central nucleus (CeA) receives nociceptive input that is mediated by glutamatergic neurotransmission. The present study compared the contribution of N-methyl-D-aspartate (NMDA) receptor agonism and antagonism in CeA to generation of the affective response of rats to an acute noxious stimulus. Vocalizations that occur following a brief tail shock (vocalization afterdischarges) are a validated rodent model of pain affect, and were preferentially suppressed, in a dose dependent manner, by bilateral injection into CeA of NMDA (.1 µg, .25 µg, .5 µg, or 1 µg/side), or the NMDA receptor antagonist D-2-amino-5-phosphonovalerate (AP5, 1 µg, 2 µg, or 4 µg/side). Vocalizations that occur during tail shock were suppressed to a lesser degree, whereas, spinal motor reflexes (tail flick and hind limb movements) were unaffected by injection of NMDA or AP5 into CeA. Injection of NMDA, but not AP5, into CeA increased c-Fos immunoreactivity in the ventrolateral periaqueductal gray (vlPAG), and unilateral injection of the µ-opiate receptor antagonist H-D-Phe-Cys-Tyr-D-Trp-Arg-Thr-Pen-Thr-NH2 (CTAP, 0.25 µg) into vlPAG prevented the antinociception generated by injection of NMDA into CeA. These findings demonstrate that although NMDA receptor agonism and antagonism in CeA produce similar suppression of pain behaviors they do so via different neurobiological mechanisms. Perspective The amygdala contributes to production of the emotional dimension of pain. NMDA receptor agonism and antagonism within the central nucleus of the amygdala suppressed rats’ emotional response to acute painful stimulation. Understanding the neurobiology underlying emotional responses to pain will provide insights into new treatments for pain and its associated affective disorders. PMID:25261341

  2. Axonal Regulation of Central Nervous System Myelination: Structure and Function. (United States)

    Klingseisen, Anna; Lyons, David A


    Approximately half of the human brain consists of myelinated axons. Central nervous system (CNS) myelin is made by oligodendrocytes and is essential for nervous system formation, health, and function. Once thought simply as a static insulator that facilitated rapid impulse conduction, myelin is now known to be made and remodeled in to adult life. Oligodendrocytes have a remarkable capacity to differentiate by default, but many aspects of their development can be influenced by axons. However, how axons and oligodendrocytes interact and cooperate to regulate myelination in the CNS remains unclear. Here, we review recent advances in our understanding of how such interactions generate the complexity of myelination known to exist in vivo. We highlight intriguing results that indicate that the cross-sectional size of an axon alone may regulate myelination to a surprising degree. We also review new studies, which have highlighted diversity in the myelination of axons of different neuronal subtypes and circuits, and structure-function relationships, which suggest that myelinated axons can be exquisitely fine-tuned to mediate precise conduction needs. We also discuss recent advances in our understanding of how neuronal activity regulates CNS myelination, and aim to provide an integrated overview of how axon-oligodendrocyte interactions sculpt neuronal circuit structure and function.

  3. Distribution of dopamine transporter immunoreactive fibers in the human amygdaloid complex. (United States)

    García-Amado, María; Prensa, Lucía


    The nuclei of the human amygdaloid complex can be distinguished from each other on the basis of their cytoarchitecture, chemistry and connections, all of which process the information needed for the different functions (ranging from attention to memory and emotion) of the amygdala. This complex receives dopaminergic input that exerts modulatory effects over its intrinsic network and is critical for reward-related learning and fear conditioning. To determine the specific distribution of the dopaminergic input through the different nuclei and nuclear subdivisions of this structure we used stereological tools to quantify the fibers containing the dopamine transporter (used to signal the dopaminergic phenotype) in post-mortem samples from control individuals. Dopaminergic axons targeted every nucleus of the amygdaloid complex, and the density of dopamine transporter-containing axons varied considerably among its nuclear groups. The central group showed the greatest density of dopamine transporter-positive fibers, more than double the density of the basolateral group, the second most densely innervated structure. The dopamine transporter-positive innervation is very scant in the corticomedial group. The density of dopamine transporter-positive fibers did not vary among the nuclei of the basolateral group - i.e. basal, lateral and accessory basal nuclei - although there were significant density gradients among the subdivisions of these nuclei. These detailed quantitative data on dopamine transporter-positive innervation in the human amygdaloid complex can offer a useful reference in future studies aimed at analysing putative dysfunctions of this system in diseases involving brain dopamine, such as certain anxiety disorders, Parkinson's disease and schizophrenia. © 2013 Federation of European Neuroscience Societies and John Wiley & Sons Ltd.

  4. Forced notch signaling inhibits commissural axon outgrowth in the developing chick central nerve system.

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    Ming Shi

    Full Text Available BACKGROUND: A collection of in vitro evidence has demonstrated that Notch signaling plays a key role in the growth of neurites in differentiated neurons. However, the effects of Notch signaling on axon outgrowth in an in vivo condition remain largely unknown. METHODOLOGY/PRINCIPAL FINDINGS: In this study, the neural tubes of HH10-11 chick embryos were in ovo electroporated with various Notch transgenes of activating or inhibiting Notch signaling, and then their effects on commissural axon outgrowth across the floor plate midline in the chick developing central nerve system were investigated. Our results showed that forced expression of Notch intracellular domain, constitutively active form of RBPJ, or full-length Hes1 in the rostral hindbrain, diencephalon and spinal cord at stage HH10-11 significantly inhibited commissural axon outgrowth. On the other hand, inhibition of Notch signaling by ectopically expressing a dominant-negative form of RBPJ promoted commissural axonal growth along the circumferential axis. Further results revealed that these Notch signaling-mediated axon outgrowth defects may be not due to the alteration of axon guidance since commissural axon marker TAG1 was present in the axons in floor plate midline, and also not result from the changes in cell fate determination of commissural neurons since the expression of postmitotic neuron marker Tuj1 and specific commissural markers TAG1 and Pax7 was unchanged. CONCLUSIONS/SIGNIFICANCE: We first used an in vivo system to provide evidence that forced Notch signaling negatively regulates commissural axon outgrowth.

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

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    M.A. Pires-Neto


    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.

  6. [A case of malignant amygdaloid cyst]. (United States)

    Abdennour, S; Allag, S; Benhalima, H


    An amygdaloid cyst is a rare high laterocervical cystic tumor arising from the second branchial cleft. It accounts for 2% of laterocervical tumors and up to 85% of second branchial cleft abnormalities [1]. The incidence of intracystic squamous cell carcinoma ranges from 4 to 22% [2]. The diagnosis of primary carcinoma or intracystic metastasis is a controversial issue. We report a rare case of degenerate amygdaloid cyst meeting the diagnostic criteria for intracystic squamous cell carcinoma determined by Martin and Khafif. A 73-year-old female patient consulted for a left cervical swelling in 2010; the diagnosis was an amygdaloid cyst. She had a history of squamous cell carcinoma of the hard palate (T1NoMo) surgery and radiation therapy in 2009, without recurrence. Three years later, the swelling increased to a large size without any cervical node involvement. An exploratory cervicotomy with histological study revealed intracystic squamous cell degeneration. Primary squamous cell carcinoma location in the wall of an amygdaloid cyst is extremely rare and a highly controversial issue. The challenge is to be able to discriminate between a cystic metastasis of squamous cell carcinoma of the aerodigestive tract and a primary squamous cell carcinoma located in the wall of an amygdaloid cyst. Martin and Khafif defined specific criteria to confirm the diagnosis of primary branchiogenic carcinoma. Copyright © 2014 Elsevier Masson SAS. All rights reserved.

  7. Development of a central nervous system axonal myelination assay for high throughput screening. (United States)

    Lariosa-Willingham, Karen D; Rosler, Elen S; Tung, Jay S; Dugas, Jason C; Collins, Tassie L; Leonoudakis, Dmitri


    Regeneration of new myelin is impaired in persistent multiple sclerosis (MS) lesions, leaving neurons unable to function properly and subject to further degeneration. Current MS therapies attempt to ameliorate autoimmune-mediated demyelination, but none directly promote the regeneration of lost and damaged myelin of the central nervous system (CNS). Development of new drugs that stimulate remyelination has been hampered by the inability to evaluate axonal myelination in a rapid CNS culture system. We established a high throughput cell-based assay to identify compounds that promote myelination. Culture methods were developed for initiating myelination in vitro using primary embryonic rat cortical cells. We developed an immunofluorescent phenotypic image analysis method to quantify the morphological alignment of myelin characteristic of the initiation of myelination. Using γ-secretase inhibitors as promoters of myelination, the optimal growth, time course and compound treatment conditions were established in a 96 well plate format. We have characterized the cortical myelination assay by evaluating the cellular composition of the cultures and expression of markers of differentiation over the time course of the assay. We have validated the assay scalability and consistency by screening the NIH clinical collection library of 727 compounds and identified ten compounds that promote myelination. Half maximal effective concentration (EC50) values for these compounds were determined to rank them according to potency. We have designed the first high capacity in vitro assay that assesses myelination of live axons. This assay will be ideal for screening large compound libraries to identify new drugs that stimulate myelination. Identification of agents capable of promoting the myelination of axons will likely lead to the development of new therapeutics for MS patients.

  8. Mass fragmentographic determination of gamma-aminobutyric acid and glutamic acid in discrete amygdaloid nuclei of rat brain. (United States)

    Nakamura, K; Matsumoto, T; Hirano, M; Kagoshima, H; Kuroki, T; Yao, H; Uchimura, H; Nakahara, T


    A mass fragmentographic method for the simultaneous quantification of gamma-aminobutyric acid (GABA) and glutamic acid is described. In a convenient one-step reaction, the two amino acids were derivatized with pentafluoropropionic anhydride and pentafluoropropanol. The derivatization products were stable for several days. The technique has been applied to the assay of GABA and Glu in five amygdaloid nuclei of the rat brain. The GABA level was high in the central and medial nuclei, whereas the Glu level was high in the lateral and basal nuclei. The regional distribution of GABA was different from that of Glu within the amygdaloid nuclei.

  9. Neuroinflammation as Fuel for Axonal Regeneration in the Injured Vertebrate Central Nervous System

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    Ilse Bollaerts


    Full Text Available Damage to the central nervous system (CNS is one of the leading causes of morbidity and mortality in elderly, as repair after lesions or neurodegenerative disease usually fails because of the limited capacity of CNS regeneration. The causes underlying this limited regenerative potential are multifactorial, but one critical aspect is neuroinflammation. Although classically considered as harmful, it is now becoming increasingly clear that inflammation can also promote regeneration, if the appropriate context is provided. Here, we review the current knowledge on how acute inflammation is intertwined with axonal regeneration, an important component of CNS repair. After optic nerve or spinal cord injury, inflammatory stimulation and/or modification greatly improve the regenerative outcome in rodents. Moreover, the hypothesis of a beneficial role of inflammation is further supported by evidence from adult zebrafish, which possess the remarkable capability to repair CNS lesions and even restore functionality. Lastly, we shed light on the impact of aging processes on the regenerative capacity in the CNS of mammals and zebrafish. As aging not only affects the CNS, but also the immune system, the regeneration potential is expected to further decline in aged individuals, an element that should definitely be considered in the search for novel therapeutic strategies.

  10. Enhanced Transcriptional Activity and Mitochondrial Localization of STAT3 Co-induce Axon Regrowth in the Adult Central Nervous System

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    Xueting Luo


    Full Text Available Signal transducer and activator of transcription 3 (STAT3 is a transcription factor central to axon regrowth with an enigmatic ability to act in different subcellular regions independently of its transcriptional roles. However, its roles in mature CNS neurons remain unclear. Here, we show that along with nuclear translocation, STAT3 translocates to mitochondria in mature CNS neurons upon cytokine stimulation. Loss- and gain-of-function studies using knockout mice and viral expression of various STAT3 mutants demonstrate that STAT3′s transcriptional function is indispensable for CNS axon regrowth, whereas mitochondrial STAT3 enhances bioenergetics and further potentiates regrowth. STAT3′s localization, functions, and growth-promoting effects are regulated by mitogen-activated protein kinase kinase (MEK, an effect further enhanced by Pten deletion, leading to extensive axon regrowth in the mouse optic pathway and spinal cord. These results highlight CNS neuronal dependence on STAT3 transcriptional activity, with mitochondrial STAT3 providing ancillary roles, and illustrate a critical contribution for MEK in enhancing diverse STAT3 functions and axon regrowth.

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

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    Edmund eHollis


    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.

  12. The effect of 5-HT2a/2c receptor agonist microinjected into central amygdaloid nucleus and median preoptic area on maternal aggressive behavior in rats Efeito sobre o comportamento materno agressivo de ratos da microinjeção do agonista seletivo de receptores 5-HT2a/2c no núcleo central da amígdala e na área pré-óptica medial

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    Rosa Maria Martins de Almeida


    Full Text Available OBJECTIVE: Much evidence supports the hypothesis that 5-hydroxytryptamine (5-HT activation is related to the inhibition of aggression. We examined potentially pro- and anti-aggressive effects of the 5-HT2A/2C receptor agonist on specific brain sites. METHOD: Female Wistar rats on the 7th day postpartum were microinjected with the selective 5-HT2A/2C receptor agonist, alpha-methyl-5-hydroxytryptamine maleate (0.2 to 1.0 µg/0.2 µl into the central amygdaloid nucleus and median preoptic nucleus. For each brain area studied, the frequency of the behaviors: locomotion, social investigation, lateral threat, attacks (frontal and lateral, and biting the intruder were compared among the various treatments by an Analysis of Variance, followed when appropriate, by Tukey's test. RESULTS: Microinjection of the selective 5-HT2A/2C receptor agonist, a-methyl-5-hydroxytryptamine maleate into central amygdaloid nucleus increased maternal aggression in the absence of concurrent changes in non-aggressive behavior. By contrast, microinjection of the selective 5-HT2A/2C receptor agonist at several dilutions into the median preoptic nucleusdid not alter aggressive behavior. CONCLUSIONS: The current and earlier data with pro- and anti-aggressive effects of the 5-HT2a/2c receptor agonist, when microinjected into the median preoptic nucleus relative to the central amygdaloid nucleus, medial septum and periaqueductal grey area in female rats point to functionally separate serotonin receptor populations in the amygdaloid-septal-hypothalamic and periaqueductal gray matter areas controlling aggressive behavior. It is possible that amygdaloid 5-HT2a/2c receptors may increase aggressive behavior in lactating females as a result of changes in fear.OBJETIVO: Resultados de muitos estudos sustentam a hipótese de que a serotonina (5-HT está relacionada com a inibição do comportamento agressivo. Foram examinados os efeitos potenciais pró e anti-agressivos do agonista de

  13. Effect of the mineralogical composition on the petrophysical behavior of the amygdaloidal and vesicular basalt of Wadi Wizr, Eastern Desert, Egypt (United States)

    Nabawy, Bassem S.; Wassif, Nadia A.


    This paper gives an account of the petrophysical characteristics and the petrographical descriptions of Tertiary vesicular and amygdaloidal olivine basalt flows from Wadi Wizr in the central Eastern Desert of Egypt. The petrographical studies indicated that the studied vesicular basalts are rich in calcic-plagioclase, augite and olivine in addition to numerous amounts of fine opaque minerals and vesicles filled with carbonate and quartz amygdales. The degree of oxidation and alteration of magnetite and ilmenite are discussed in detail. Petrophysically, the studied samples can be grouped into two main groups; the first group includes amygdaloidal basalts and the second group consists of vesicular basalts. The vesicular group (the permeable one) is characterized by fair to very good porosity (∅), good permeability (k), very low true formation resistivity factor (F) and contain micro to ultra micropores. On the other hand, the amygdaloidal basalt group (impermeable group) is characterized by very low storage capacity properties, fair porosity, negligible permeability, medium to high true formation resistivity factor and ultra micropores. The mercury injection capillary pressure technique (MICP) indicates that the pore throats of the studied vesicular samples have a binomial distribution (rank IV), while that of the amygdaloidal samples have a trinomial distribution (rank V). It has been found in this study that the petrophysical behavior of basalts is dependent on the degree of oxidation and alteration; and in particular on the rate of cooling and oxidation of the opaque minerals which caused filling in the primarily produced vesicles by low temperature secondary minerals.

  14. γ-diketone central neuropathy: quantitative morphometric analysis of axons in rat spinal cord white matter regions and nerve roots

    International Nuclear Information System (INIS)

    LoPachin, Richard M.; Jortner, Bernard S.; Reid, Maria L.; Das, Soma


    A quantitative analytical method was used to measure myelinated axon morphometric parameters (e.g., axon area, ratio of axon area/fiber area, and index of circularity) in rat nervous tissue during intoxication with 2,5-hexanedione (HD). Parameters were assessed in nerve roots (dorsal and ventral) and in ascending (gracile fasciculus and spinocerebellar tract) and descending (corticospinal and rubrospinal tracts) spinal cord white matter tracts (L4-L5) of rats intoxicated with HD at two different daily dose-rates (175 or 400 mg HD/kg/day, gavage). For each dose-rate, tissue was sampled at four neurological endpoints: unaffected, slight, moderate, and severe toxicity, as determined by gait analysis and measurements of grip strength. Results indicate that, regardless of the HD dose-rate, axon atrophy (reduced axon area) was a widespread, abundant effect that developed in concert with neurological deficits. The atrophy response occurred contemporaneously in both ascending and descending spinal tracts, which suggests that loss of caliber developed simultaneously along the proximodistal axon axis. In contrast, swollen axons were a numerically small component and were present in nerve roots and spinal tracts only during subchronic intoxication at the lower HD dose-rate (i.e., 175 mg/kg/day). Intoxication at the higher dose-rate (400 mg/kg/day) produced neurological deficits in the absence of axonal swellings. These observations in conjunction with our previous studies of HD-induced peripheral neuropathy (Toxicol. Appl. Pharmacol. 135 (1995) 58; and Toxicol. Appl. Pharmacol. 165 (2000) 127) indicate that axon atrophy, and not axonal swelling, is a primary neuropathic phenomenon

  15. Signal propagation along the axon. (United States)

    Rama, Sylvain; Zbili, Mickaël; Debanne, Dominique


    Axons link distant brain regions and are usually considered as simple transmission cables in which reliable propagation occurs once an action potential has been generated. Safe propagation of action potentials relies on specific ion channel expression at strategic points of the axon such as nodes of Ranvier or axonal branch points. However, while action potentials are generally considered as the quantum of neuronal information, their signaling is not entirely digital. In fact, both their shape and their conduction speed have been shown to be modulated by activity, leading to regulations of synaptic latency and synaptic strength. We report here newly identified mechanisms of (1) safe spike propagation along the axon, (2) compartmentalization of action potential shape in the axon, (3) analog modulation of spike-evoked synaptic transmission and (4) alteration in conduction time after persistent regulation of axon morphology in central neurons. We discuss the contribution of these regulations in information processing. Copyright © 2018 Elsevier Ltd. All rights reserved.

  16. 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.

  17. Central connectivity of transient receptor potential melastatin 8-expressing axons in the brain stem and spinal dorsal horn. (United States)

    Kim, Yun Sook; Park, Jun Hong; Choi, Su Jung; Bae, Jin Young; Ahn, Dong Kuk; McKemy, David D; Bae, Yong Chul


    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.

  18. Stereological analysis of neuron, glial and endothelial cell numbers in the human amygdaloid complex.

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    María García-Amado

    Full Text Available Cell number alterations in the amygdaloid complex (AC might coincide with neurological and psychiatric pathologies with anxiety imbalances as well as with changes in brain functionality during aging. This stereological study focused on estimating, in samples from 7 control individuals aged 20 to 75 years old, the number and density of neurons, glia and endothelial cells in the entire AC and in its 5 nuclear groups (including the basolateral (BL, corticomedial and central groups, 5 nuclei and 13 nuclear subdivisions. The volume and total cell number in these territories were determined on Nissl-stained sections with the Cavalieri principle and the optical fractionator. The AC mean volume was 956 mm(3 and mean cell numbers (x10(6 were: 15.3 neurons, 60 glial cells and 16.8 endothelial cells. The numbers of endothelial cells and neurons were similar in each AC region and were one fourth the number of glial cells. Analysis of the influence of the individuals' age at death on volume, cell number and density in each of these 24 AC regions suggested that aging does not affect regional size or the amount of glial cells, but that neuron and endothelial cell numbers respectively tended to decrease and increase in territories such as AC or BL. These accurate stereological measures of volume and total cell numbers and densities in the AC of control individuals could serve as appropriate reference values to evaluate subtle alterations in this structure in pathological conditions.

  19. Stereological analysis of neuron, glial and endothelial cell numbers in the human amygdaloid complex. (United States)

    García-Amado, María; Prensa, Lucía


    Cell number alterations in the amygdaloid complex (AC) might coincide with neurological and psychiatric pathologies with anxiety imbalances as well as with changes in brain functionality during aging. This stereological study focused on estimating, in samples from 7 control individuals aged 20 to 75 years old, the number and density of neurons, glia and endothelial cells in the entire AC and in its 5 nuclear groups (including the basolateral (BL), corticomedial and central groups), 5 nuclei and 13 nuclear subdivisions. The volume and total cell number in these territories were determined on Nissl-stained sections with the Cavalieri principle and the optical fractionator. The AC mean volume was 956 mm(3) and mean cell numbers (x10(6)) were: 15.3 neurons, 60 glial cells and 16.8 endothelial cells. The numbers of endothelial cells and neurons were similar in each AC region and were one fourth the number of glial cells. Analysis of the influence of the individuals' age at death on volume, cell number and density in each of these 24 AC regions suggested that aging does not affect regional size or the amount of glial cells, but that neuron and endothelial cell numbers respectively tended to decrease and increase in territories such as AC or BL. These accurate stereological measures of volume and total cell numbers and densities in the AC of control individuals could serve as appropriate reference values to evaluate subtle alterations in this structure in pathological conditions.

  20. Genetics Home Reference: giant axonal neuropathy (United States)

    ... connect the brain and spinal cord (central nervous system) to muscles and to sensory cells that detect sensations such as touch, pain, heat, and sound. However, axons in the central nervous system are affected as well. The signs and symptoms ...

  1. AxonSeg: Open Source Software for Axon and Myelin Segmentation and Morphometric Analysis. (United States)

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


    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:

  2. Serotonin spillover onto the axon initial segment of motoneurons induces central fatigue by inhibiting action potential initiation

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    Cotel, Florence; Exley, Richard; Cragg, Stephanie


    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...... 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...

  3. Amygdaloid lesions block the effect of neuropeptides (vasopressin, ACTH4–10) on avoidance behavior

    NARCIS (Netherlands)

    Wimersma Greidanus, T.B. van; Croiset, G.; Bakker, E.; Bouman, H.

    Lesions in the amygdaloid complex result in an increased activity of rats in open field behavior in that generally more exploration and rearing is observed as compared with sham-operated animals. No effect of the lesion was observed on acquisition and extinction of an active avoidance response, but

  4. Cell intrinsic control of axon regeneration (United States)

    Mar, Fernando M; Bonni, Azad; Sousa, Mónica M


    Although neurons execute a cell intrinsic program of axonal growth during development, following the establishment of connections, the developmental growth capacity declines. Besides environmental challenges, this switch largely accounts for the failure of adult central nervous system (CNS) axons to regenerate. Here, we discuss the cell intrinsic control of axon regeneration, including not only the regulation of transcriptional and epigenetic mechanisms, but also the modulation of local protein translation, retrograde and anterograde axonal transport, and microtubule dynamics. We further explore the causes underlying the failure of CNS neurons to mount a vigorous regenerative response, and the paradigms demonstrating the activation of cell intrinsic axon growth programs. Finally, we present potential mechanisms to support axon regeneration, as these may represent future therapeutic approaches to promote recovery following CNS injury and disease. PMID:24531721

  5. Contribution of glycogen in supporting axon conduction in the peripheral and central nervous systems: the role of lactate

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    Angus M Brown


    Full Text Available The role of glycogen in the central nervous system is intimately linked with the glycolytic pathway. Glycogen is synthesized from glucose, the primary substrate for glycolysis, and degraded to glucose-6-phosphate. The metabolic cost of shunting glucose via glycogen exceeds that of simple phosphorylation of glucose to glucose-6-phosphate by hexokinase; thus, there must be a metabolic advantage in utilizing this shunt pathway. The dogmatic view of glycogen as a storage depot persists, based on initial descriptions of glycogen supporting neural function in the face of aglycemia. The variable latency to conduction failure, dependent upon tissue glycogen levels, provided convincing evidence of the role played by glycogen in supporting neural function. Glycogen is located predominantly in astrocytes in the central nervous system, thus for glycogen to benefit neural elements, intercellular metabolic communication must exist in the form of astrocyte to neuron substrate transfer. Experimental evidence supports a model where glycogen is metabolized to lactate in astrocytes, with cellular expression of monocarboxylate transporters and enzymes appropriately located for lactate shuttling between astrocytes and neural elements, where lactate acts as a substrate for oxidative metabolism. Biosensor recordings have demonstrated a significant steady concentration of lactate present on the periphery of both central white matter and peripheral nerve under unstimulated baseline conditions, indicating continuous cellular efflux of lactate to the interstitium. The existence of this lactate pool argues we must reexamine the ‘on demand’ shuttling of lactate between cellular elements, and suggests continuous lactate efflux surplus to immediate neural requirements.

  6. Activation of mTor Signaling by Gene Transduction to Induce Axon Regeneration in the Central Nervous System Following Neural Injury (United States)


    lesion staining is reduced to about 20% in the Tau- Tom control. Both p70S6K (CA) and NLS-p70S6K (CA) induce new axon growth and restore the extent of...TH innervation to 40.5 and 42.1 percent respectively. The latter is significantly different than the Tau- Tom control (p = 0.027), but the former is...not, due to the higher standard error. In measures of the number of TH-positive axons in the MFB (B) and the number Tau- Tom -positive axons in the

  7. Activation of mTor Signaling by Gene Transduction to Induce Axon Regeneration in the Central Nervous System Following Neural Injury (Addendum) (United States)


    dopaminergic axons within the medial forebrain bundle (MFB) by tyrosine hydroxylase (TH) immunohistochemistry, or the number of GFP-positive axons or Tomato...Yarygina O, Kholodilov N, Burke RE. Expression mediated by three partial sequences of the human tyrosine hydroxylase promoter in vivo, Submitted...Pathway in Mammalian Cells : Constitutive Active Mutants of Rheb and mTOR. Methods Enzymol. 2008;438:307-20.

  8. Increased mitochondrial content in remyelinated axons: implications for multiple sclerosis (United States)

    Zambonin, Jessica L.; Zhao, Chao; Ohno, Nobuhiko; Campbell, Graham R.; Engeham, Sarah; Ziabreva, Iryna; Schwarz, Nadine; Lee, Sok Ee; Frischer, Josa M.; Turnbull, Doug M.; Trapp, Bruce D.; Lassmann, Hans; Franklin, Robin J. M.


    Mitochondrial content within axons increases following demyelination in the central nervous system, presumably as a response to the changes in energy needs of axons imposed by redistribution of sodium channels. Myelin sheaths can be restored in demyelinated axons and remyelination in some multiple sclerosis lesions is extensive, while in others it is incomplete or absent. The effects of remyelination on axonal mitochondrial content in multiple sclerosis, particularly whether remyelination completely reverses the mitochondrial changes that follow demyelination, are currently unknown. In this study, we analysed axonal mitochondria within demyelinated, remyelinated and myelinated axons in post-mortem tissue from patients with multiple sclerosis and controls, as well as in experimental models of demyelination and remyelination, in vivo and in vitro. Immunofluorescent labelling of mitochondria (porin, a voltage-dependent anion channel expressed on all mitochondria) and axons (neurofilament), and ultrastructural imaging showed that in both multiple sclerosis and experimental demyelination, mitochondrial content within remyelinated axons was significantly less than in acutely and chronically demyelinated axons but more numerous than in myelinated axons. The greater mitochondrial content within remyelinated, compared with myelinated, axons was due to an increase in density of porin elements whereas increase in size accounted for the change observed in demyelinated axons. The increase in mitochondrial content in remyelinated axons was associated with an increase in mitochondrial respiratory chain complex IV activity. In vitro studies showed a significant increase in the number of stationary mitochondria in remyelinated compared with myelinated and demyelinated axons. The number of mobile mitochondria in remyelinated axons did not significantly differ from myelinated axons, although significantly greater than in demyelinated axons. Our neuropathological data and findings in

  9. Comparative analyses of the neuron numbers and volumes of the amygdaloid complex in old and new world primates. (United States)

    Carlo, C N; Stefanacci, L; Semendeferi, K; Stevens, C F


    The amygdaloid complex (AC), a key component of the limbic system, is a brain region critical for the detection and interpretation of emotionally salient information. Therefore, changes in its structure and function are likely to provide correlates of mood and emotion disorders, diseases that afflict a large portion of the human population. Previous gross comparisons of the AC in control and diseased individuals have, however, mainly failed to discover these expected correlations with diseases. We have characterized AC nuclei in different nonhuman primate species to establish a baseline for more refined comparisons between the normal and the diseased amygdala. AC nuclei volume and neuron number in 19 subdivisions are reported from 13 Old and New World primate brains, spanning five primate species, and compared with corresponding data from humans. Analysis of the four largest AC nuclei revealed that volume and neuron number of one component, the central nucleus, has a negative allometric relationship with total amygdala volume and neuron number, which is in contrast with the isometric relationship found in the other AC nuclei (for both neuron number and volume). Neuron density decreases across all four nuclei according to a single power law with an exponent of about minus one-half. Because we have included quantitative comparisons with great apes and humans, our conclusions apply to human brains, and our scaling laws can potentially be used to study the anatomical correlates of the amygdala in disorders involving pathological emotion processing. (c) 2009 Wiley-Liss, Inc.

  10. Meninges-derived cues control axon guidance. (United States)

    Suter, Tracey A C S; DeLoughery, Zachary J; Jaworski, Alexander


    The axons of developing neurons travel long distances along stereotyped pathways under the direction of extracellular cues sensed by the axonal growth cone. Guidance cues are either secreted proteins that diffuse freely or bind the extracellular matrix, or membrane-anchored proteins. Different populations of axons express distinct sets of receptors for guidance cues, which results in differential responses to specific ligands. The full repertoire of axon guidance cues and receptors and the identity of the tissues producing these cues remain to be elucidated. The meninges are connective tissue layers enveloping the vertebrate brain and spinal cord that serve to protect the central nervous system (CNS). The meninges also instruct nervous system development by regulating the generation and migration of neural progenitors, but it has not been determined whether they help guide axons to their targets. Here, we investigate a possible role for the meninges in neuronal wiring. Using mouse neural tissue explants, we show that developing spinal cord meninges produce secreted attractive and repulsive cues that can guide multiple types of axons in vitro. We find that motor and sensory neurons, which project axons across the CNS-peripheral nervous system (PNS) boundary, are attracted by meninges. Conversely, axons of both ipsi- and contralaterally projecting dorsal spinal cord interneurons are repelled by meninges. The responses of these axonal populations to the meninges are consistent with their trajectories relative to meninges in vivo, suggesting that meningeal guidance factors contribute to nervous system wiring and control which axons are able to traverse the CNS-PNS boundary. Copyright © 2017 Elsevier Inc. All rights reserved.

  11. B-RAF kinase drives developmental axon growth and promotes axon regeneration in the injured mature CNS (United States)

    O’Donovan, Kevin J.; Ma, Kaijie; Guo, Hengchang; Wang, Chen; Sun, Fang; Han, Seung Baek; Kim, Hyukmin; Wong, Jamie K.; Charron, Jean; Zou, Hongyan; Son, Young-Jin; He, Zhigang


    Activation of intrinsic growth programs that promote developmental axon growth may also facilitate axon regeneration in injured adult neurons. Here, we demonstrate that conditional activation of B-RAF kinase alone in mouse embryonic neurons is sufficient to drive the growth of long-range peripheral sensory axon projections in vivo in the absence of upstream neurotrophin signaling. We further show that activated B-RAF signaling enables robust regenerative growth of sensory axons into the spinal cord after a dorsal root crush as well as substantial axon regrowth in the crush-lesioned optic nerve. Finally, the combination of B-RAF gain-of-function and PTEN loss-of-function promotes optic nerve axon extension beyond what would be predicted for a simple additive effect. We conclude that cell-intrinsic RAF signaling is a crucial pathway promoting developmental and regenerative axon growth in the peripheral and central nervous systems. PMID:24733831

  12. Activation of mTor Signaling by Gene Transduction to Induce Axon Regeneration in the Central Nervous System Following Neural Injury (United States)


    which the axon-targeted fusion protein Tomato-Tau is delivered to SN neurons by AAV and expression is driven by the robust chicken -beta actin promoter...prior to sacrifice for histological analysis. Thus, the behavioral data is obtained prior to knowledge of the anatomical results. For were subcloned into an adeno-associated virus 2 (AAV2) backbone plasmid (pBL) that incorporated the chicken b-actin promoter and a woodchuck

  13. Axonal cleaved caspase-3 regulates axon targeting and morphogenesis in the developing auditory brainstem

    Directory of Open Access Journals (Sweden)

    Sarah E Rotschafer


    Full Text Available Caspase-3 is a cysteine protease that is most commonly associated with cell death. Recent studies have shown additional roles in mediating cell differentiation, cell proliferation, and development of cell morphology. We investigated the role of caspase-3 in the development of chick auditory brainstem nuclei during embryogenesis. Immunofluorescence from embryonic days E6-13 revealed that the temporal expression of cleaved caspase-3 follows the ascending anatomical pathway. Expression is first seen in the auditory portion of VIIIth nerve including central axonal regions projecting to nucleus magnocellularis (NM, then later in NM axons projecting to nucleus laminaris (NL, and subsequently in NL dendrites. To examine the function of cleaved caspase-3 in chick auditory brainstem development, we blocked caspase-3 cleavage in developing chick embryos with the caspase-3 inhibitor Z-DEVD-FMK from E6 to E9, then examined NM and NL morphology and NM axonal targeting on E10. NL lamination in treated embryos was disorganized and the neuropil around NL contained a significant number of glial cells normally excluded from this region. Additionally, NM axons projected into inappropriate portions of NL in Z-DEVD-FMK treated embyros. We found that the presence of misrouted axons was associated with more severe NL disorganization. The effects of axonal caspase-3 inhibition on both NL morphogenesis and NM axon targeting suggest that these developmental processes are coordinated, likely through communication between axons and their targets.

  14. Peroxisome deficiency but not the defect in ether lipid synthesis causes activation of the innate immune system and axonal loss in the central nervous system

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    Bottelbergs Astrid


    Full Text Available Abstract Background Mice with peroxisome deficiency in neural cells (Nestin-Pex5−/− develop a neurodegenerative phenotype leading to motor and cognitive disabilities and early death. Major pathologies at the end stage of disease include severe demyelination, axonal degeneration and neuroinflammation. We now investigated the onset and progression of these pathological processes, and their potential interrelationship. In addition, the putative role of oxidative stress, the impact of plasmalogen depletion on the neurodegenerative phenotype, and the consequences of peroxisome elimination in the postnatal period were studied. Methods Immunohistochemistry in association with gene expression analysis was performed on Nestin-Pex5−/− mice to document demyelination, axonal damage and neuroinflammation. Also Gnpat−/− mice, with selective plasmalogen deficiency and CMV-Tx-Pex5−/− mice, with tamoxifen induced generalized loss of peroxisomes were analysed. Results Activation of the innate immune system is a very early event in the pathological process in Nestin-Pex5−/− mice which evolves in chronic neuroinflammation. The complement factor C1q, one of the earliest up regulated transcripts, was expressed on neurons and oligodendrocytes but not on microglia. Transcripts of other pro- and anti-inflammatory genes and markers of phagocytotic activity were already significantly induced before detecting pathologies with immunofluorescent staining. Demyelination, macrophage activity and axonal loss co-occurred throughout the brain. As in patients with mild peroxisome biogenesis disorders who develop regressive changes, demyelination in cerebellum and brain stem preceded major myelin loss in corpus callosum of both Nestin-Pex5−/− and CMV-Tx-Pex5−/− mice. These lesions were not accompanied by generalized oxidative stress throughout the brain. Although Gnpat−/− mice displayed dysmyelination and Purkinje cell axon damage in cerebellum

  15. Axon degeneration: make the Schwann cell great again

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    Keit Men Wong


    Full Text Available Axonal degeneration is a pivotal feature of many neurodegenerative conditions and substantially accounts for neurological morbidity. A widely used experimental model to study the mechanisms of axonal degeneration is Wallerian degeneration (WD, which occurs after acute axonal injury. In the peripheral nervous system (PNS, WD is characterized by swift dismantling and clearance of injured axons with their myelin sheaths. This is a prerequisite for successful axonal regeneration. In the central nervous system (CNS, WD is much slower, which significantly contributes to failed axonal regeneration. Although it is well-documented that Schwann cells (SCs have a critical role in the regenerative potential of the PNS, to date we have only scarce knowledge as to how SCs 'sense' axonal injury and immediately respond to it. In this regard, it remains unknown as to whether SCs play the role of a passive bystander or an active director during the execution of the highly orchestrated disintegration program of axons. Older reports, together with more recent studies, suggest that SCs mount dynamic injury responses minutes after axonal injury, long before axonal breakdown occurs. The swift SC response to axonal injury could play either a pro-degenerative role, or alternatively a supportive role, to the integrity of distressed axons that have not yet committed to degenerate. Indeed, supporting the latter concept, recent findings in a chronic PNS neurodegeneration model indicate that deactivation of a key molecule promoting SC injury responses exacerbates axonal loss. If this holds true in a broader spectrum of conditions, it may provide the grounds for the development of new glia-centric therapeutic approaches to counteract axonal loss.

  16. Growing central axons deprived of normal target neurones by neonatal X-ray irradiation still terminate in a precisely laminated fashion

    International Nuclear Information System (INIS)

    Laurberg, S.; Hjorth-Simonsen, A.


    Some studies are described on rat pups. The object was to study the fate of axons that normally terminate in a highly selective laminar fashion in the molecular layer of the medial limb of the dentate gyrus of the mammalian cerebral cortex when this is removed by neonatal X-ray irradiation. The rats were shielded with Pb, except for a field above the hippocampus and the dentate gyrus, and exposed to X-rays from a 250 kV source at a distance of 34 cm. (U.K.)

  17. Can injured adult CNS axons regenerate by recapitulating development? (United States)

    Hilton, Brett J; Bradke, Frank


    In the adult mammalian central nervous system (CNS), neurons typically fail to regenerate their axons after injury. During development, by contrast, neurons extend axons effectively. A variety of intracellular mechanisms mediate this difference, including changes in gene expression, the ability to form a growth cone, differences in mitochondrial function/axonal transport and the efficacy of synaptic transmission. In turn, these intracellular processes are linked to extracellular differences between the developing and adult CNS. During development, the extracellular environment directs axon growth and circuit formation. In adulthood, by contrast, extracellular factors, such as myelin and the extracellular matrix, restrict axon growth. Here, we discuss whether the reactivation of developmental processes can elicit axon regeneration in the injured CNS. © 2017. Published by The Company of Biologists Ltd.

  18. Acute nutritional axonal neuropathy. (United States)

    Hamel, Johanna; Logigian, Eric L


    This study describes clinical, laboratory, and electrodiagnostic features of a severe acute axonal polyneuropathy common to patients with acute nutritional deficiency in the setting of alcoholism, bariatric surgery (BS), or anorexia. Retrospective analysis of clinical, electrodiagnostic, and laboratory data of patients with acute axonal neuropathy. Thirteen patients were identified with a severe, painful, sensory or sensorimotor axonal polyneuropathy that developed over 2-12 weeks with sensory ataxia, areflexia, variable muscle weakness, poor nutritional status, and weight loss, often with prolonged vomiting and normal cerebrospinal fluid protein. Vitamin B6 was low in half and thiamine was low in all patients when obtained before supplementation. Patients improved with weight gain and vitamin supplementation, with motor greater than sensory recovery. We suggest that acute or subacute axonal neuropathy in patients with weight loss or vomiting associated with alcohol abuse, BS, or dietary deficiency is one syndrome, caused by micronutrient deficiencies. Muscle Nerve 57: 33-39, 2018. © 2017 Wiley Periodicals, Inc.

  19. Concepts for regulation of axon integrity by enwrapping glia

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    Bogdan eBeirowski


    Full Text Available Long axons and their enwrapping glia (Schwann cells and oligodendrocytes form a unique compound structure that serves as conduit for transport of electric and chemical information in the nervous system. The peculiar cytoarchitecture over an enormous length as well as its substantial energetic requirements make this conduit particularly susceptible to detrimental alterations. Degeneration of long axons independent of neuronal cell bodies is observed comparatively early in a range of neurodegenerative conditions as a consequence of abnormalities in Schwann cells and oligodendrocytes. This leads to the most relevant disease symptoms and highlights the critical role that these glia have for axon integrity, but the underlying mechanisms remain elusive. The quest to understand why and how axons degenerate is now a crucial frontier in disease-oriented research. This challenge is most likely to lead to significant progress if the inextricable link between axons and their flanking glia in pathological situations is recognized. In this review I compile recent advances in our understanding of the molecular programs governing axon degeneration, and mechanisms of enwrapping glia’s non-cell autonomous impact on axon-integrity. A particular focus is placed on emerging evidence suggesting that enwrapping glia nurture long axons by virtue of their intimate association, release of trophic substances, and neurometabolic coupling. The correction of defects in these functions has the potential to stabilize axons in a variety of neuronal diseases in the peripheral and central nervous system.

  20. Enhancement of Amygdaloid Neuronal Dendritic Arborization by Fresh Leaf Juice of Centella asiatica (Linn during Growth Spurt Period in Rats

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    K. G. Mohandas Rao


    Full Text Available Centella asiatica (CeA is a creeping herb, growing in moist places in India and other Asian Countries. Ayurvedic system of medicine, an alternate system of medicine in India, uses leaves of CeA for memory enhancement. Here, we have investigated the role of CeA fresh leaf juice treatment during growth spurt period of rats on dendritic morphology of amygdaloid neurons, one of the regions concerned with learning and memory. The present study was conducted on neonatal rat pups. The rat pups (7-days-old were fed with 2, 4 and 6 ml/kg body of fresh leaf juice of CeA for 2, 4 and 6 weeks. After the treatment period, the rats were killed, brains removed and amygdaloid neurons impregnated with Silver nitrate (Golgi staining. Amygdaloid neurons were traced using camera lucida and dendritic branching points (a measure of dendritic arborization and intersections (a measure dendritic length quantified. These data were compared with those of age-matched control rats. The results showed a significant increase in dendritic length (intersections and dendritic branching points along the length of dendrites of the amygdaloid neurons of rats treated with 4 and 6 ml/kg body weight/day of CeA for longer periods of time (i.e. 4 and 6 weeks. We conclude that constituents/active principles present in CeA fresh leaf juice has neuronal dendritic growth stimulating property; hence it can be used for enhancing neuronal dendrites in stress and other neurodegenerative and memory disorders.

  1. Direct evidence of central nervous system axonal damage in patients with postoperative delirium: A preliminary study of pNF-H as a promising serum biomarker. (United States)

    Inoue, Reo; Sumitani, Masahiko; Ogata, Toru; Chikuda, Hirotaka; Matsubara, Takehiro; Kato, So; Shimojo, Nobutake; Uchida, Kanji; Yamada, Yoshitsugu


    Approximately 50-80% patients experience postoperative delirium, an acute cognitive dysfunction associated with prolonged hospitalization, increased mortality, excess healthcare costs, and persistent cognitive impairment. Elucidation of the mechanism of delirium and associated diagnostic and therapeutic measures are urgently required. Here we investigated the role of phosphorylated neurofilament heavy subunit (pNF-H), a major structural protein in axons, as a predictive maker of postoperative delirium. Twenty-three patients who underwent surgery for abdominal cancer were screened for postoperative delirium, and they were assessed for its severity using the memorial delirium assessment scale (MDAS) at and 48h after delirium onset. Serum pNF-H levels were also measured at both time points. The patients were divided into two groups according to the presence or absence of pNF-H. Clinical variables were compared between groups using the Mann-Whitney U test, and the relationship between pNF-H levels and delirium severity was analyzed using the exponential curve fitting. Fifteen of the 23 (65.2%) patients tested positive for pNF-H, and these patients exhibited significantly higher MDAS scores compared with the pNF-H-negative patients only at the onset of delirium. Although the MDAS score significantly improved over time in the positive group, pNF-H positivity persisted. There was a correlation between the maximum pNF-H level and maximum MDAS score (R 2 =0.31, p=0.013). More severe postoperative delirium was directly related to higher serum pNF-H levels, suggesting the potential application of pNF-H as a quantitative biomarker of neural damage in postoperative delirium. Copyright © 2017 Elsevier B.V. All rights reserved.

  2. Urinary bladder extracellular matrix hydrogels and matrix-bound vesicles differentially regulate central nervous system neuron viability and axon growth and branching. (United States)

    Faust, Anne; Kandakatla, Apoorva; van der Merwe, Yolandi; Ren, Tanchen; Huleihel, Luai; Hussey, George; Naranjo, Juan Diego; Johnson, Scott; Badylak, Stephen; Steketee, Michael


    Central nervous system neurons often degenerate after trauma due to the inflammatory innate immune response to injury, which can lead to neuronal cell death, scarring, and permanently lost neurologic function. Extracellular matrix bioscaffolds, derived by decellularizing healthy tissues, have been widely used in both preclinical and clinical studies to promote positive tissue remodeling, including neurogenesis, in numerous tissues, with extracellular matrix from homologous tissues often inducing more positive responses. Extracellular matrix hydrogels are liquid at room temperature and enable minimally invasive extracellular matrix injections into central nervous system tissues, before gelation at 37℃. However, few studies have analyzed how extracellular matrix hydrogels influence primary central nervous system neuron survival and growth, and whether central nervous system and non-central nervous system extracellular matrix specificity is critical to neuronal responses. Urinary bladder extracellular matrix hydrogels increase both primary hippocampal neuron survival and neurite growth to similar or even greater extents, suggesting extracellular matrix from non-homologous tissue sources, such as urinary bladder matrix-extracellular matrix, may be a more economical and safer alternative to developing central nervous system extracellular matrices for central nervous system applications. Additionally, we show matrix-bound vesicles derived from urinary bladder extracellular matrix are endocytosed by hippocampal neurons and positively regulate primary hippocampal neuron neurite growth. Matrix-bound vesicles carry protein and RNA cargos, including noncoding RNAs and miRNAs that map to the human genome and are known to regulate cellular processes. Thus, urinary bladder matrix-bound vesicles provide natural and transfectable cargoes which offer new experimental tools and therapeutic applications to study and treat central nervous system neuron injury.

  3. The medial amygdaloid nucleus modulates the baroreflex activity in conscious rats. (United States)

    Fortaleza, Eduardo Albino Trindade; Ferreira-Junior, Nilson Carlos; Lagatta, Davi Campos; Resstel, Leonardo Barbosa Moraes; Corrêa, Fernando Morgan Aguiar


    The medial amygdaloid nucleus (MeA) is involved in cardiovascular control. In the present study we report the effect of MeA pharmacological ablations caused by bilateral microinjections of the nonselective synaptic blocker CoCl2 on cardiac baroreflex responses in rats. MeA synaptic inhibition evoked by local bilateral microinjection of 100 nL of CoCl2 (1 mM) did not affect blood pressure or heart rate baseline, suggesting no tonic MeA influence on resting cardiovascular parameters. However, 10 min after CoCl2 microinjection into the MeA of male Wistar rats, the reflex bradycardic response evoked by intravenous infusion of phenylephrine was significantly enhanced when compared with the reflex bradycardic response observed before CoCl2. The treatment did not affect the tachycardic responses to the intravenous infusion of sodium nitroprusside (SNP). Baroreflex activity returned to control values 60 min after CoCl2 microinjections, confirming a reversible blockade. The present results indicate an involvement of the MeA in baroreflex modulation, suggesting that synapses in the MeA have an inhibitory influence on the bradycardic component of the baroreflex in conscious rats. Copyright © 2015 Elsevier B.V. All rights reserved.

  4. A growing field: The regulation of axonal regeneration by Wnt signaling. (United States)

    Garcia, Armando L; Udeh, Adanna; Kalahasty, Karthik; Hackam, Abigail S


    The canonical Wnt/β-catenin pathway is a highly conserved signaling cascade that plays critical roles during embryogenesis. Wnt ligands regulate axonal extension, growth cone guidance and synaptogenesis throughout the developing central nervous system (CNS). Recently, studies in mammalian and fish model systems have demonstrated that Wnt/β-catenin signaling also promotes axonal regeneration in the adult optic nerve and spinal cord after injury, raising the possibility that Wnt could be developed as a therapeutic strategy. In this review, we summarize experimental evidence that reveals novel roles for Wnt signaling in the injured CNS, and discuss possible mechanisms by which Wnt ligands could overcome molecular barriers inhibiting axonal growth to promote regeneration. A central challenge in the neuroscience field is developing therapeutic strategies that induce robust axonal regeneration. Although adult axons have the capacity to respond to axonal guidance molecules after injury, there are several major obstacles for axonal growth, including extensive neuronal death, glial scars at the injury site, and lack of axonal guidance signals. Research in rodents demonstrated that activation of Wnt/β-catenin signaling in retinal neurons and radial glia induced neuronal survival and axonal growth, but that activation within reactive glia at the injury site promoted proliferation and glial scar formation. Studies in zebrafish spinal cord injury models confirm an axonal regenerative role for Wnt/β-catenin signaling and identified the cell types responsible. Additionally, in vitro and in vivo studies demonstrated that Wnt induces axonal and neurite growth through transcription-dependent effects of its central mediator β-catenin, potentially by inducing regeneration-promoting genes. Canonical Wnt signaling may also function through transcription-independent interactions of β-catenin with cytoskeletal elements, which could stabilize growing axons and control growth cone

  5. Regeneration of axons in the mouse retina after injury. (United States)

    McConnell, P; Berry, M


    It is generally accepted that most axons in the mammalian CNS show only transient growth in response to injury, and numerous hypotheses have been advanced to account for this phenomenon. Detailed knowledge of the time-course and extent of this so-called 'abortive regeneration' is, however, surprisingly lacking. The retina of the adult albino mouse provides a convenient system in which to quantify the response of central axons to injury, since the retina can be prepared as a whole mount, allowing silver-impregnated axons to be followed along their entire course. Using this experimental model, sprouting of injured axons was observed as early as 14 h post lesion (hpl) with rapid growth (20 micrometers/day on average) continuing until 10 dpl. Thereafter, a decline in the overall growth rate was observed, presumably regenerated sprouts began to degenerate. However, not all axons showed this abortive response: numerous unfasciculated axons continued in random growth until at least 100 dpl. One possible interpretation of these results is that the concept of abortive regeneration of injured axons is untenable in regions of the CNS which are lacking in myelin.

  6. Oligodendrocyte Development in the Absence of Their Target Axons In Vivo.

    Directory of Open Access Journals (Sweden)

    Rafael Almeida

    Full Text Available Oligodendrocytes form myelin around axons of the central nervous system, enabling saltatory conduction. Recent work has established that axons can regulate certain aspects of oligodendrocyte development and myelination, yet remarkably oligodendrocytes in culture retain the ability to differentiate in the absence of axons and elaborate myelin sheaths around synthetic axon-like substrates. It remains unclear the extent to which the life-course of oligodendrocytes requires the presence of, or signals derived from axons in vivo. In particular, it is unclear whether the specific axons fated for myelination regulate the oligodendrocyte population in a living organism, and if so, which precise steps of oligodendrocyte-cell lineage progression are regulated by target axons. Here, we use live-imaging of zebrafish larvae carrying transgenic reporters that label oligodendrocyte-lineage cells to investigate which aspects of oligodendrocyte development, from specification to differentiation, are affected when we manipulate the target axonal environment. To drastically reduce the number of axons targeted for myelination, we use a previously identified kinesin-binding protein (kbp mutant, in which the first myelinated axons in the spinal cord, reticulospinal axons, do not fully grow in length, creating a region in the posterior spinal cord where most initial targets for myelination are absent. We find that a 73% reduction of reticulospinal axon surface in the posterior spinal cord of kbp mutants results in a 27% reduction in the number of oligodendrocytes. By time-lapse analysis of transgenic OPC reporters, we find that the reduction in oligodendrocyte number is explained by a reduction in OPC proliferation and survival. Interestingly, OPC specification and migration are unaltered in the near absence of normal axonal targets. Finally, we find that timely differentiation of OPCs into oligodendrocytes does not depend at all on the presence of target axons

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

    DEFF Research Database (Denmark)

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


    cells, while other fibers were unmyelinated. Immunohistochemistry demonstrated that some of the regenerated fibers were tyrosine hydroxylase- or serotonin-immunoreactive, indicating a central origin. These findings suggest that there is a considerable amount of spontaneous regeneration after spinal cord......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...... length of all NF-immunolabeled axons within the lesion cavities was increased 6- to 10-fold at 5, 10, and 15 wk post-lesion compared with 1 wk post-surgery. In ultrastructural studies we found the putatively regenerating axons within the lesion to be associated either with oligodendrocytes or Schwann...

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

    Directory of Open Access Journals (Sweden)

    Jeffery L Twiss


    Full Text Available 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 synthesis 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 documented 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 regenerating 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 regenerating 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.

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

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    Robin eWhite


    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.

  10. The role of mitochondria in axonal degeneration and tissue repair in MS

    NARCIS (Netherlands)

    van Horssen, J.; Witte, M.E.; Ciccarelli, O.


    Axonal injury is a key feature of multiple sclerosis (MS) pathology and is currently seen as the main correlate for permanent clinical disability. Although little is known about the pathogenetic mechanisms that drive axonal damage and loss, there is accumulating evidence highlighting the central

  11. The progeroid gene BubR1 regulates axon myelination and motor function

    NARCIS (Netherlands)

    Choi, C.I.; Yoo, K.H.; Hussaini, S.M.; Jeon, B.T.; Welby, J.; Gan, H.; Scarisbrick, I.A.; Zhang, Z.; Baker, D.J.; Deursen, J.M.A. van; Rodriguez, M.; Jang, M.H.


    Myelination, the process by which oligodendrocytes form the myelin sheath around axons, is key to axonal signal transduction and related motor function in the central nervous system (CNS). Aging is characterized by degenerative changes in the myelin sheath, although the molecular underpinnings of

  12. 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.

  13. Role of calpains in the injury-induced dysfunction and degeneration of the mammalian axon. (United States)

    Ma, Marek


    Axonal injury and degeneration, whether primary or secondary, contribute to the morbidity and mortality seen in many acquired and inherited central nervous system (CNS) and peripheral nervous system (PNS) disorders, such as traumatic brain injury, spinal cord injury, cerebral ischemia, neurodegenerative diseases, and peripheral neuropathies. The calpain family of proteases has been mechanistically linked to the dysfunction and degeneration of axons. While the direct mechanisms by which transection, mechanical strain, ischemia, or complement activation trigger intra-axonal calpain activity are likely different, the downstream effects of unregulated calpain activity may be similar in seemingly disparate diseases. In this review, a brief examination of axonal structure is followed by a focused overview of the calpain family. Finally, the mechanisms by which calpains may disrupt the axonal cytoskeleton, transport, and specialized domains (axon initial segment, nodes, and terminals) are discussed. © 2013.

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

    DEFF Research Database (Denmark)

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


    cells, while other fibers were unmyelinated. Immunohistochemistry demonstrated that some of the regenerated fibers were tyrosine hydroxylase- or serotonin-immunoreactive, indicating a central origin. These findings suggest that there is a considerable amount of spontaneous regeneration after spinal cord...... lesions in rodents and that the fibers remain several months after injury. The findings of tyrosine hydroxylase- and serotonin-immunoreactivity in the axons suggest that descending central fibers contribute to this endogenous repair of ischemic spinal cord injury....

  15. A high mitochondrial transport rate characterizes CNS neurons with high axonal regeneration capacity.

    Directory of Open Access Journals (Sweden)

    Romain Cartoni

    Full Text Available Improving axonal transport in the injured and diseased central nervous system has been proposed as a promising strategy to improve neuronal repair. However, the contribution of each cargo to the repair mechanism is unknown. DRG neurons globally increase axonal transport during regeneration. Because the transport of specific cargos after axonal insult has not been examined systematically in a model of enhanced regenerative capacity, it is unknown whether the transport of all cargos would be modulated equally in injured central nervous system neurons. Here, using a microfluidic culture system we compared neurons co-deleted for PTEN and SOCS3, an established model of high axonal regeneration capacity, to control neurons. We measured the axonal transport of three cargos (mitochondria, synaptic vesicles and late endosomes in regenerating axons and found that the transport of mitochondria, but not the other cargos, was increased in PTEN/SOCS3 co-deleted axons relative to controls. The results reported here suggest a pivotal role for this organelle during axonal regeneration.

  16. Exposure to an open-field arena increases c-Fos expression in a distributed anxiety-related system projecting to the basolateral amygdaloid complex

    DEFF Research Database (Denmark)

    Hale, M.W.; Hay-Schmidt, A.; Mikkelsen, J.D.


    Anxiety states and anxiety-related behaviors appear to be regulated by a distributed and highly interconnected system of brain structures including the basolateral amygdala. Our previous studies demonstrate that exposure of rats to an open-field in high- and low-light conditions results in a marked...... of specific afferent input to this region of the amygdala. In order to identify candidate brain regions mediating anxiety-induced activation of the basolateral amygdaloid complex in rats, we used cholera toxin B subunit (CTb) as a retrograde tracer to identify neurons with direct afferent projections....... These data are consistent with the hypothesis that exposure to the open-field arena activates an anxiety-related neuronal system with convergent input to the basolateral amygdaloid complex Udgivelsesdato: 2008/8/26...

  17. A sub-threshold dose of pilocarpine increases glutamine synthetase in reactive astrocytes and enhances the progression of amygdaloid-kindling epilepsy in rats. (United States)

    Sun, Hong-Liu; Deng, Da-Ping; Pan, Xiao-Hong; Wang, Chao-Yun; Zhang, Xiu-Li; Chen, Xiang-Ming; Wang, Chun-Hua; Liu, Yu-Xia; Li, Shu-Cui; Bai, Xian-Yong; Zhu, Wei


    The prognosis of patients exposed to a sub-threshold dose of a proconvulsant is difficult to establish. In this study, we investigated the effect of a single sub-threshold dose of the proconvulsant pilocarpine (PILO) on the progression of seizures that were subsequently induced by daily electrical stimulation (kindling) of the amygdaloid formation. Male Sprague–Dawley rats were each implanted with an electrode in the right basolateral amygdala and an indwelling cannula in the right ventricle. The animals were randomized into groups and were administered one of the following treatments: saline, PILO, saline+L-α-aminoadipic acid (L-AAA; one dosage tested), PILO+L-AAA, or PILO+L-methionine sulfoximine (three dosages tested). Amygdaloid stimulation and electroencephalography were performed once daily. We performed immunohistochemistry and western blot for glial fibrillary acidic protein and glutamine synthetase (GS). We also assayed the enzymic activity of GS in discrete brain regions. An intraperitoneal injection of a sub-threshold PILO dose enhanced the progression of amygdaloid-kindling seizures and was accompanied by an increase in reactive-astrocyte and GS (content and activity) in the hippocampus and piriform cortex. L-AAA and L-methionine sulfoximine, inhibitors of astrocytic and GS function, respectively, abolished the effect of PILO on amygdaloid-kindling seizures. We conclude that one sub-threshold dose of a proconvulsant may enhance the progression of subsequent epilepsy and astrocytic GS may play a role in this phenomenon. Thus, a future therapy for epilepsy could be inhibition of astrocytes and/or GS.

  18. Lost in the jungle: new hurdles for optic nerve axon regeneration. (United States)

    Pernet, Vincent; Schwab, Martin E


    The poor regenerative capacity of injured central nervous system (CNS) axons leads to permanent neurological deficits after brain, spinal cord, or optic nerve lesions. In the optic nerve, recent studies showed that stimulation of the cytokine or mammalian target of rapamycin (mTOR) signaling pathways potently enhances sprouting and regeneration of injured retinal ganglion cell axons in adult mice, but does not allow the majority of axons to reach their main cerebral targets. New analyses have revealed axon navigation defects in the optic nerve and at the optic chiasm under conditions of strong growth stimulation. We propose that a balanced growth stimulatory treatment will have to be combined with guidance factors and suppression of local growth inhibitory factors to obtain the full regeneration of long CNS axonal tracts. Copyright © 2014 Elsevier Ltd. All rights reserved.

  19. PACSIN1, a Tau-interacting protein, regulates axonal elongation and branching by facilitating microtubule instability. (United States)

    Liu, Yingying; Lv, Kaosheng; Li, Zenglong; Yu, Albert C H; Chen, Jianguo; Teng, Junlin


    Tau is a major member of the neuronal microtubule-associated proteins. It promotes tubulin assembly and stabilizes axonal microtubules. Previous studies have demonstrated that Tau forms cross-bridges between microtubules, with some particles located on cross-bridges, suggesting that some proteins interact with Tau and might be involved in regulating Tau-related microtubule dynamics. This study reports that PACSIN1 interacts with Tau in axon. PACSIN1 blockade results in impaired axonal elongation and a higher number of primary axonal branches in mouse dorsal root ganglia neurons, which is induced by increasing the binding ability of Tau to microtubules. In PACSIN1-blocked dorsal root ganglia neurons, a greater amount of Tau is inclined to accumulate in the central domain of growth cones, and it promotes the stability of the microtubule network. Taken together, these results suggest that PACSIN1 is an important Tau binding partner in regulating microtubule dynamics and forming axonal plasticity.

  20. CSPGs inhibit axon branching by impairing mitochondria-dependent regulation of actin dynamics and axonal translation. (United States)

    Sainath, Rajiv; Ketschek, Andrea; Grandi, Leah; Gallo, Gianluca


    Chondroitin sulfate proteoglycans (CSPGs) inhibit the formation of axon collateral branches. The regulation of the axonal cytoskeleton and mitochondria are important components of the mechanism of branching. Actin-dependent axonal plasticity, reflected in the dynamics of axonal actin patches and filopodia, is greatest along segments of the axon populated by mitochondria. It is reported that CSPGs partially depolarize the membrane potential of axonal mitochondria, which impairs the dynamics of the axonal actin cytoskeleton and decreases the formation and duration of axonal filopodia, the first steps in the mechanism of branching. The effects of CSPGs on actin cytoskeletal dynamics are specific to axon segments populated by mitochondria. In contrast, CSPGs do not affect the microtubule content of axons, or the localization of microtubules into axonal filopodia, a required step in the mechanism of branch formation. It is also reported that CSPGs decrease the mitochondria-dependent axonal translation of cortactin, an actin associated protein involved in branching. Finally, the inhibitory effects of CSPGs on axon branching, actin cytoskeletal dynamics and the axonal translation of cortactin are reversed by culturing neurons with acetyl-l-carnitine, which promotes mitochondrial respiration. Collectively these data indicate that CSPGs impair mitochondrial function in axons, an effect which contributes to the inhibition of axon branching. © 2016 Wiley Periodicals, Inc. Develop Neurobiol 77: 419-437, 2017. © 2016 Wiley Periodicals, Inc.

  1. The axonal cytoskeleton : from organization to function

    NARCIS (Netherlands)

    Kevenaar, Josta T|info:eu-repo/dai/nl/338771042; Hoogenraad, Casper C|info:eu-repo/dai/nl/227263502

    The axon is the single long fiber that extends from the neuron and transmits electrical signals away from the cell body. The neuronal cytoskeleton, composed of microtubules (MTs), actin filaments and neurofilaments, is not only required for axon formation and axonal transport but also provides the

  2. 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.

  3. Slowing of axonal regeneration is correlated with increased axonal viscosity during aging

    Directory of Open Access Journals (Sweden)

    Heidemann Steven R


    Full Text Available Abstract Background As we age, the speed of axonal regeneration declines. At the biophysical level, why this occurs is not well understood. Results To investigate we first measured the rate of axonal elongation of sensory neurons cultured from neonatal and adult rats. We found that neonatal axons grew 40% faster than adult axons (11.5 µm/hour vs. 8.2 µm/hour. To determine how the mechanical properties of axons change during maturation, we used force calibrated towing needles to measure the viscosity (stiffness and strength of substrate adhesion of neonatal and adult sensory axons. We found no significant difference in the strength of adhesions, but did find that adult axons were 3 times intrinsically stiffer than neonatal axons. Conclusions Taken together, our results suggest decreasing axonal stiffness may be part of an effective strategy to accelerate the regeneration of axons in the adult peripheral nervous system.

  4. Pannexin 1 Modulates Axonal Growth in Mouse Peripheral Nerves

    Directory of Open Access Journals (Sweden)

    Steven M. Horton


    Full Text Available The pannexin family of channels consists of three members—pannexin-1 (Panx1, pannexin-2 (Panx2, and pannexin-3 (Panx3 that enable the exchange of metabolites and signaling molecules between intracellular and extracellular compartments. Pannexin-mediated release of intracellular ATP into the extracellular space has been tied to a number of cellular activities, primarily through the activity of type P2 purinergic receptors. Previous work indicates that the opening of Panx1 channels and activation of purinergic receptors by extracellular ATP may cause inflammation and apoptosis. In the CNS (central nervous system and PNS (peripheral nervous system, coupled pannexin, and P2 functions have been linked to peripheral sensitization (pain pathways. Purinergic pathways are also essential for other critical processes in the PNS, including myelination and neurite outgrowth. However, whether such pathways are pannexin-dependent remains to be determined. In this study, we use a Panx1 knockout mouse model and pharmacological inhibitors of the Panx1 and the ATP-mediated signaling pathway to fill gaps in our understanding of Panx1 localization in peripheral nerves, roles for Panx1 in axonal outgrowth and myelination, and neurite extension. Our data show that Panx1 is localized to axonal, myelin, and vascular compartments of the peripheral nerves. Knockout of Panx1 gene significantly increased axonal caliber in vivo and axonal growth rate in cultured dorsal root ganglia (DRG neurons. Furthermore, genetic knockout of Panx1 or inhibition of components of purinergic signaling, by treatment with probenecid and apyrase, resulted in denser axonal outgrowth from cultured DRG explants compared to untreated wild-types. Our findings suggest that Panx1 regulates axonal growth in the peripheral nervous system.

  5. The Kinesin Adaptor Calsyntenin-1 Organizes Microtubule Polarity and Regulates Dynamics during Sensory Axon Arbor Development

    Directory of Open Access Journals (Sweden)

    Mary C. Halloran


    Full Text Available Axon growth and branching, and development of neuronal polarity are critically dependent on proper organization and dynamics of the microtubule (MT cytoskeleton. MTs must organize with correct polarity for delivery of diverse cargos to appropriate subcellular locations, yet the molecular mechanisms regulating MT polarity remain poorly understood. Moreover, how an actively branching axon reorganizes MTs to direct their plus ends distally at branch points is unknown. We used high-speed, in vivo imaging of polymerizing MT plus ends to characterize MT dynamics in developing sensory axon arbors in zebrafish embryos. We find that axonal MTs are highly dynamic throughout development, and that the peripheral and central axons of sensory neurons show differences in MT behaviors. Furthermore, we show that Calsyntenin-1 (Clstn-1, a kinesin adaptor required for sensory axon branching, also regulates MT polarity in developing axon arbors. In wild type neurons the vast majority of MTs are directed in the correct plus-end-distal orientation from early stages of development. Loss of Clstn-1 causes an increase in MTs polymerizing in the retrograde direction. These misoriented MTs most often are found near growth cones and branch points, suggesting Clstn-1 is particularly important for organizing MT polarity at these locations. Together, our results suggest that Clstn-1, in addition to regulating kinesin-mediated cargo transport, also organizes the underlying MT highway during axon arbor development.

  6. N-docosahexaenoylethanolamine regulates Hedgehog signaling and promotes growth of cortical axons

    Directory of Open Access Journals (Sweden)

    Giorgi Kharebava


    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.

  7. Differential role of gonadal hormones on kainic acid-induced neurodegeneration in medial amygdaloid nucleus of female and male rats. (United States)

    Pereno, G L; Beltramino, C A


    Sex hormones contribute to modulating brain functions throughout the life span. It has been suggested that estrogen prevents neuronal loss in different areas of the CNS such as the hippocampus. However there are less consistent data on its effects on the amygdala. Kainic acid (KA) is used to produce seizures that mimic those of temporal lobe epilepsy in humans. At high doses in animal models, KA induces neurotoxicity, particularly in the medial amygdaloid nuclei (MeA). It is uncertain whether the gonadal hormones are protective or not against this neurotoxicity in the MeA. Here we show that a single dose of KA induces neurodegeneration in the subnuclei of the MeA of rats with different degrees of intensity in males and females. A differential neuroprotective effect of the gonadal hormones was also observed. In diestrous rats, massive neuronal death similar to that in the ovariectomized females was detected. MeA neurons of proestrous rats, like the ovariectomized treated with estrogen, were significantly less affected by the KA. Testosterone produced a mild neuroprotective action, but dihydrotestosterone did not protect. A similar pattern was observed in all male groups. Together, the results indicate that estrogen protects MeA neurons from KA neurotoxicity. Androgens are only partially neuroprotective, with this effect being found only in testosterone, probably through its conversion to estrogen by aromatase.

  8. Biochemical Evaluation and Green Synthesis of Nano Silver Using Peroxidase from Euphorbia (Euphorbia amygdaloides and Its Antibacterial Activity

    Directory of Open Access Journals (Sweden)

    Semra Cicek


    Full Text Available Silver nanoparticles are used an increased attention for various biomedical and medical applications. In this study, green synthesis of silver nanoparticles was made with simple method by using peroxidase enzyme partially purified from Euphorbia (Euphorbia amygdaloides plant. Optimum pH, temperature and time period were determined to obtain silver nanoparticles using the peroxidase enzyme. The result shows that higher silver nanoparticle was synthesized for 4 hours and at 20°C and pH 8. Also, optimal concentration of metal ions was found as 0.5 mM. The synthesized silver nanoparticles were characterized by UV spectrum, scanning electron microscope (SEM and X-ray diffraction. Antibacterial activity of silver nanoparticles was measured against some microorganisms such as Serratia marcescens, Yersinia pseudotuberculosis, Klebsiella pneumoniae, Staphylococcus aureus, Staphylococcus epidermidis, Streptococcus pyogenes, Pseudomonas aeruginosa, Salmonella typhimurium, Listeria monocytogenes, and Escherichia coli. Synthesized silver nanoparticles have wide spectrum antibacterial activity in low concentration and may be a good alternative therapeutic approach in medicine and pharmaceutical fields in future.

  9. Necl-4/SynCAM-4 is expressed in myelinating oligodendrocytes but not required for axonal myelination.

    Directory of Open Access Journals (Sweden)

    Ying Zhu

    Full Text Available The timing and progression of axonal myelination are precisely controlled by intercellular interactions between neurons and glia in development. Previous in vitro studies demonstrated that Nectin like 4 (Necl-4, also known as cell adhesion molecule Cadm-4 or SynCAM-4 plays an essential role in axonal myelination by Schwann cells in the peripheral nervous system (PNS. However, the role of Necl-4 protein in axonal myelination in the developing central nervous system (CNS has remained unknown. In this study, we discovered upregulation of Necl-4 expression in mature oligodendrocytes at perinatal stages when axons undergo active myelination. We generated Necl4 gene knockout mice, but found that disruption of Necl-4 gene did not affect oligodendrocyte differentiation and myelin formation in the CNS. Surprisingly, disruption of Necl-4 had no significant effect on axonal myelination in the PNS either. Therefore, our results demonstrated that Necl-4 is dispensable for axonal myelination in the developing nervous system.

  10. 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


    , 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......, but not MMP-9, are involved in this process. Furthermore, administration of a novel antibody to MT1-MMP that selectively blocks pro-MMP-2 activation revealed a functional co-involvement of these proteinases in determining RGC axon outgrowth. Subsequent immunostainings showed expression of both MMP-2 and MT1......-MMP in RGC axons and glial cells. Finally, results from combined inhibition of MMP-2 and β1-integrin were suggestive for a functional interaction between these molecules. Overall, our data indicate MMP-2 and MT1-MMP as promising axonal outgrowth-promoting molecules. Axonal regeneration in the central...

  11. Axonal and presynaptic protein synthesis: new insights into the biology of the neuron. (United States)

    Giuditta, Antonio; Kaplan, Barry B; van Minnen, Jan; Alvarez, Jaime; Koenig, Edward


    The presence of a local mRNA translation system in axons and terminals was proposed almost 40 years ago. Over the ensuing period, an impressive body of evidence has grown to support this proposal -- yet the nerve cell body is still considered to be the only source of axonal and presynaptic proteins. To dispel this lingering neglect, we now present the wealth of recent observations bearing on this central idea, and consider their impact on our understanding of the biology of the neuron. We demonstrate that extrasomatic translation sites, which are now well recognized in dendrites, are also present in axonal and presynaptic compartments.

  12. Molecular and Cellular Mechanisms of Axonal Regeneration After Spinal Cord Injury* (United States)

    van Niekerk, Erna A.; Tuszynski, Mark H.; Lu, Paul; Dulin, Jennifer N.


    Following axotomy, a complex temporal and spatial coordination of molecular events enables regeneration of the peripheral nerve. In contrast, multiple intrinsic and extrinsic factors contribute to the general failure of axonal regeneration in the central nervous system. In this review, we examine the current understanding of differences in protein expression and post-translational modifications, activation of signaling networks, and environmental cues that may underlie the divergent regenerative capacity of central and peripheral axons. We also highlight key experimental strategies to enhance axonal regeneration via modulation of intraneuronal signaling networks and the extracellular milieu. Finally, we explore potential applications of proteomics to fill gaps in the current understanding of molecular mechanisms underlying regeneration, and to provide insight into the development of more effective approaches to promote axonal regeneration following injury to the nervous system. PMID:26695766

  13. Molecular and Cellular Mechanisms of Axonal Regeneration After Spinal Cord Injury. (United States)

    van Niekerk, Erna A; Tuszynski, Mark H; Lu, Paul; Dulin, Jennifer N


    Following axotomy, a complex temporal and spatial coordination of molecular events enables regeneration of the peripheral nerve. In contrast, multiple intrinsic and extrinsic factors contribute to the general failure of axonal regeneration in the central nervous system. In this review, we examine the current understanding of differences in protein expression and post-translational modifications, activation of signaling networks, and environmental cues that may underlie the divergent regenerative capacity of central and peripheral axons. We also highlight key experimental strategies to enhance axonal regeneration via modulation of intraneuronal signaling networks and the extracellular milieu. Finally, we explore potential applications of proteomics to fill gaps in the current understanding of molecular mechanisms underlying regeneration, and to provide insight into the development of more effective approaches to promote axonal regeneration following injury to the nervous system. © 2016 by The American Society for Biochemistry and Molecular Biology, Inc.

  14. Multiple sclerosis and anterograde axonal degeneration study by magnetic resonance

    International Nuclear Information System (INIS)

    Martinez Pardo, P.; Capdevila Cirera, A.; Sanz Marin, P.M.; Gili Planas, J.


    Multiple sclerosis (MS) is a disease of the central nervous system that affects specifically the myelin. Its diagnosis by imaging techniques is, since the development of magnetic resonance (MR), relatively simple, and its occasional association with anterograde axonal degeneration (WD) has been reported. In both disorders, there is a lengthening of the T1 and T2 relaxation times. In the present report, 76 patients with MS with less than 4 plaques in the typical periventricular position were studied retrospectively, resulting in a rate of association with anterograde axonal degeneration of 8%. We consider that in spite of their same behavior in MR,MS and WD, with moreover represent completely different pathologies, are perfectly differential by MR. The S-E images with longer repetition and echo times in the axial and coronal planes have proved to be those most sensitive for this differentiation. Given that MS is specific pathology of then myelin, the axonal damages in delayed until several plaques adjacent to an axon affect it. We consider that this, added to the restriction of our study group (less than 4 plaques), is the cause of the pow percentage of the MS-WD association in our study. (Author)

  15. Neurochemical Correlates of Accumbal Dopamine D2 and Amygdaloid 5-HT1B Receptor Densities on Observational Learning of Aggression (United States)

    Suzuki, Hideo; Lucas, Louis R.


    Social learning theory postulates that individuals learn to engage in aggressive behavior through observing an aggressive social model. Prior studies have shown that repeatedly observing aggression, also called “chronic passive exposure to aggression,” changes accumbal dopamine D2 receptor (D2R) and amygdaloid 5-HT1B receptor (5-HT1BR) densities in observers. But, the association between these outcomes remains unknown. Thus, our study used a rat paradigm to comprehensively examine the linkage between aggression, D2R density in the nucleus accumbens core (AcbC) and shell (AcbSh), and 5-HT1BR density in the medial (MeA), basomedial (BMA), and basolateral (BLA) amygdala following chronic passive exposure to aggression. Male Sprague-Dawley rats (N = 72) were passively exposed to either aggression or non-aggression acutely (1 day) or chronically (23 days). When observer rats were exposed to aggression chronically, they showed increased aggressive behavior and reduced D2R density in the bilateral AcbSh. On the other hand, exposure to aggression, regardless of exposure length, increased 5-HT1BR density in the bilateral BLA. Finally, low D2R in the AcbSh significantly interacted with high 5-HT1BR density in the BLA in predicting high levels of aggression in observer rats. Our results advance our understanding of the neurobiological mechanisms for observational learning of aggression, highlighting that dopamine-serotonin interaction, or AcbSh-BLA interaction, may contribute to a risk factor for aggression in observers who chronically witness aggressive interactions. PMID:25650085

  16. Polyethylene glycol restores axonal conduction after corpus callosum transection. (United States)

    Bamba, Ravinder; Riley, D Colton; Boyer, Richard B; Pollins, Alonda C; Shack, R Bruce; Thayer, Wesley P


    Polyethylene glycol (PEG) has been shown to restore axonal continuity after peripheral nerve transection in animal models. We hypothesized that PEG can also restore axonal continuity in the central nervous system. In this current experiment, coronal sectioning of the brains of Sprague-Dawley rats was performed after animal sacrifice. 3Brain high-resolution microelectrode arrays (MEA) were used to measure mean firing rate (MFR) and peak amplitude across the corpus callosum of the ex-vivo brain slices. The corpus callosum was subsequently transected and repeated measurements were performed. The cut ends of the corpus callosum were still apposite at this time. A PEG solution was applied to the injury site and repeated measurements were performed. MEA measurements showed that PEG was capable of restoring electrophysiology signaling after transection of central nerves. Before injury, the average MFRs at the ipsilateral, midline, and contralateral corpus callosum were 0.76, 0.66, and 0.65 spikes/second, respectively, and the average peak amplitudes were 69.79, 58.68, and 49.60 μV, respectively. After injury, the average MFRs were 0.71, 0.14, and 0.25 spikes/second, respectively and peak amplitudes were 52.11, 8.98, and 16.09 μV, respectively. After application of PEG, there were spikes in MFR and peak amplitude at the injury site and contralaterally. The average MFRs were 0.75, 0.55, and 0.47 spikes/second at the ipsilateral, midline, and contralateral corpus callosum, respectively and peak amplitudes were 59.44, 45.33, 40.02 μV, respectively. There were statistically differences in the average MFRs and peak amplitudes between the midline and non-midline corpus callosum groups ( P < 0.01, P < 0.05). These findings suggest that PEG restores axonal conduction between severed central nerves, potentially representing axonal fusion.

  17. Polyethylene glycol restores axonal conduction after corpus callosum transection

    Directory of Open Access Journals (Sweden)

    Ravinder Bamba


    Full Text Available Polyethylene glycol (PEG has been shown to restore axonal continuity after peripheral nerve transection in animal models. We hypothesized that PEG can also restore axonal continuity in the central nervous system. In this current experiment, coronal sectioning of the brains of Sprague-Dawley rats was performed after animal sacrifice. 3Brain high-resolution microelectrode arrays (MEA were used to measure mean firing rate (MFR and peak amplitude across the corpus callosum of the ex-vivo brain slices. The corpus callosum was subsequently transected and repeated measurements were performed. The cut ends of the corpus callosum were still apposite at this time. A PEG solution was applied to the injury site and repeated measurements were performed. MEA measurements showed that PEG was capable of restoring electrophysiology signaling after transection of central nerves. Before injury, the average MFRs at the ipsilateral, midline, and contralateral corpus callosum were 0.76, 0.66, and 0.65 spikes/second, respectively, and the average peak amplitudes were 69.79, 58.68, and 49.60 μV, respectively. After injury, the average MFRs were 0.71, 0.14, and 0.25 spikes/second, respectively and peak amplitudes were 52.11, 8.98, and 16.09 μV, respectively. After application of PEG, there were spikes in MFR and peak amplitude at the injury site and contralaterally. The average MFRs were 0.75, 0.55, and 0.47 spikes/second at the ipsilateral, midline, and contralateral corpus callosum, respectively and peak amplitudes were 59.44, 45.33, 40.02 μV, respectively. There were statistically differences in the average MFRs and peak amplitudes between the midline and non-midline corpus callosum groups (P < 0.01, P < 0.05. These findings suggest that PEG restores axonal conduction between severed central nerves, potentially representing axonal fusion.

  18. Exposure to an open-field arena increases c-Fos expression in a distributed anxiety-related system projecting to the basolateral amygdaloid complex

    DEFF Research Database (Denmark)

    Hale, M.W.; Hay-Schmidt, A.; Mikkelsen, J.D.


    Anxiety states and anxiety-related behaviors appear to be regulated by a distributed and highly interconnected system of brain structures including the basolateral amygdala. Our previous studies demonstrate that exposure of rats to an open-field in high- and low-light conditions results in a marked...... of specific afferent input to this region of the amygdala. In order to identify candidate brain regions mediating anxiety-induced activation of the basolateral amygdaloid complex in rats, we used cholera toxin B subunit (CTb) as a retrograde tracer to identify neurons with direct afferent projections...

  19. Characterizing Semaphorin-Mediated Effects on Sensory and Motor Axon Pathfinding and Connectivity During Embryonic Development. (United States)

    Huettl, Rosa Eva; Huber, Andrea B


    How are precise connectivity to peripheral targets and corresponding sensory-motor networks established during developmental innervation of the vertebrate extremities? The formation of functional sensory-motor circuits requires highly appropriate temporal and spatial regulation of axon growth which is achieved through the combination of different molecular mechanisms such as communication between heterotypic fiber systems, axon-environment, or axon-glia interactions that ensure proper fasciculation and accurate pathfinding to distal targets. Family members of the class 3 semaphorins and their cognate receptors, the neuropilins, were shown to govern various events during wiring of central and peripheral circuits, with mice lacking Sema3-Npn signaling showing deficits in timing of growth, selective fasciculation, guidance fidelity, and coupling of sensory axon growth to motor axons at developmental time points. Given the accuracy with which these processes have to interact in a stepwise manner, deficiency of the smallest cog in the wheel may impact severely on the faithful establishment and functionality of peripheral circuitries, ultimately leading to behavioral impairments or even cause the death of the animal. Reliable quantitative analyses of sensory-motor fasciculation, extension, and guidance of axons to their cognate target muscles and the skin during development, but also assessment of physiological and behavioral consequences at adult age, are therefore a necessity to extend our understanding of the molecular mechanisms of peripheral circuit formation. In this chapter we provide a detailed methodology to characterize class 3 semaphorin-mediated effects on peripheral sensory and motor axon pathfinding and connectivity during embryonic development.

  20. Sorting of Dendritic and Axonal Vesicles at the Pre-axonal Exclusion Zone

    Directory of Open Access Journals (Sweden)

    Ginny G. Farías


    Full Text Available Polarized sorting of newly synthesized proteins to the somatodendritic and axonal domains of neurons occurs by selective incorporation into distinct populations of vesicular transport carriers. An unresolved issue is how the vesicles themselves are sorted to their corresponding neuronal domains. Previous studies concluded that the axon initial segment (AIS is an actin-based filter that selectively prevents passage of somatodendritic vesicles into the axon. We find, however, that most somatodendritic vesicles fail to enter the axon at a more proximal region in the axon hillock, herein referred to as the pre-axonal exclusion zone (PAEZ. Forced coupling of a somatodendritic cargo protein to an axonally directed kinesin is sufficient to drive transport of whole somatodendritic vesicles through the PAEZ toward the distal axon. Based on these findings, we propose that polarized sorting of transport vesicles occurs at the PAEZ and depends on the ability of the vesicles to acquire an appropriately directed microtubule motor.

  1. Antinociception induced by stimulating amygdaloid nuclei in rats: changes produced by systemically administered antagonists

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    M.A. Oliveira


    Full Text Available The antinociceptive effects of stimulating the medial (ME and central (CE nuclei of the amygdala in rats were evaluated by the changes in the latency for the tail withdrawal reflex to noxious heating of the skin. A 30-s period of sine-wave stimulation of the ME or CE produced a significant and short increase in the duration of tail flick latency. A 15-s period of stimulation was ineffective. Repeated stimulation of these nuclei at 48-h intervals produced progressively smaller effects. The antinociception evoked from the ME was significantly reduced by the previous systemic administration of naloxone, methysergide, atropine, phenoxybenzamine, and propranolol, but not by mecamylamine, all given at the dose of 1.0 mg/kg. Previous systemic administration of naloxone, atropine, and propranolol, but not methysergide, phenoxybenzamine, or mecamylamine, was effective against the effects of stimulating the CE. We conclude that the antinociceptive effects of stimulating the ME involve at least opioid, serotonergic, adrenergic, and muscarinic cholinergic descending mechanisms. The effects of stimulating the CE involve at least opioid, ß-adrenergic, and muscarinic cholinergic descending mechanisms.

  2. Radial glia phagocytose axonal debris from degenerating overextending axons in the developing olfactory bulb. (United States)

    Amaya, Daniel A; Wegner, Michael; Stolt, C Claus; Chehrehasa, Fatemeh; Ekberg, Jenny A K; St John, James A


    Axon targeting during the development of the olfactory system is not always accurate, and numerous axons overextend past the target layer into the deeper layers of the olfactory bulb. To date, the fate of the mis-targeted axons has not been determined. We hypothesized that following overextension, the axons degenerate, and cells within the deeper layers of the olfactory bulb phagocytose the axonal debris. We utilized a line of transgenic mice that expresses ZsGreen fluorescent protein in primary olfactory axons. We found that overextending axons closely followed the filaments of radial glia present in the olfactory bulb during embryonic development. Following overextension into deeper layers of the olfactory bulb, axons degenerated and radial glia responded by phagocytosing the resulting debris. We used in vitro analysis to confirm that the radial glia had phagocytosed debris from olfactory axons. We also investigated whether the fate of overextending axons was altered when the development of the olfactory bulb was perturbed. In mice that lacked Sox10, a transcription factor essential for normal olfactory bulb development, we observed a disruption to the morphology and positioning of radial glia and an accumulation of olfactory axon debris within the bulb. Our results demonstrate that during early development of the olfactory system, radial glia play an important role in removing overextended axons from the deeper layers of the olfactory bulb. © 2014 Wiley Periodicals, Inc.

  3. Action Potential Dynamics in Fine Axons Probed with an Axonally Targeted Optical Voltage Sensor. (United States)

    Ma, Yihe; Bayguinov, Peter O; Jackson, Meyer B


    The complex and malleable conduction properties of axons determine how action potentials propagate through extensive axonal arbors to reach synaptic terminals. The excitability of axonal membranes plays a major role in neural circuit function, but because most axons are too thin for conventional electrical recording, their properties remain largely unexplored. To overcome this obstacle, we used a genetically encoded hybrid voltage sensor (hVOS) harboring an axonal targeting motif. Expressing this probe in transgenic mice enabled us to monitor voltage changes optically in two populations of axons in hippocampal slices, the large axons of dentate granule cells (mossy fibers) in the stratum lucidum of the CA3 region and the much finer axons of hilar mossy cells in the inner molecular layer of the dentate gyrus. Action potentials propagated with distinct velocities in each type of axon. Repetitive firing broadened action potentials in both populations, but at an intermediate frequency the degree of broadening differed. Repetitive firing also attenuated action potential amplitudes in both mossy cell and granule cell axons. These results indicate that the features of use-dependent action potential broadening, and possible failure, observed previously in large nerve terminals also appear in much finer unmyelinated axons. Subtle differences in the frequency dependences could influence the propagation of activity through different pathways to excite different populations of neurons. The axonally targeted hVOS probe used here opens up the diverse repertoire of neuronal processes to detailed biophysical study.

  4. Regulating Axonal Responses to Injury: The Intersection between Signaling Pathways Involved in Axon Myelination and The Inhibition of Axon Regeneration (United States)

    Rao, Sudheendra N. R.; Pearse, Damien D.


    Following spinal cord injury (SCI), a multitude of intrinsic and extrinsic factors adversely affect the gene programs that govern the expression of regeneration-associated genes (RAGs) and the production of a diversity of extracellular matrix molecules (ECM). Insufficient RAG expression in the injured neuron and the presence of inhibitory ECM at the lesion, leads to structural alterations in the axon that perturb the growth machinery, or form an extraneous barrier to axonal regeneration, respectively. Here, the role of myelin, both intact and debris, in antagonizing axon regeneration has been the focus of numerous investigations. These studies have employed antagonizing antibodies and knockout animals to examine how the growth cone of the re-growing axon responds to the presence of myelin and myelin-associated inhibitors (MAIs) within the lesion environment and caudal spinal cord. However, less attention has been placed on how the myelination of the axon after SCI, whether by endogenous glia or exogenously implanted glia, may alter axon regeneration. Here, we examine the intersection between intracellular signaling pathways in neurons and glia that are involved in axon myelination and axon growth, to provide greater insight into how interrogating this complex network of molecular interactions may lead to new therapeutics targeting SCI. PMID:27375427

  5. Molecular Analysis of Sensory Axon Branching Unraveled a cGMP-Dependent Signaling Cascade

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    Alexandre Dumoulin


    Full Text Available Axonal branching is a key process in the establishment of circuit connectivity within the nervous system. Molecular-genetic studies have shown that a specific form of axonal branching—the bifurcation of sensory neurons at the transition zone between the peripheral and the central nervous system—is regulated by a cyclic guanosine monophosphate (cGMP-dependent signaling cascade which is composed of C-type natriuretic peptide (CNP, the receptor guanylyl cyclase Npr2, and cGMP-dependent protein kinase Iα (cGKIα. In the absence of any one of these components, neurons in dorsal root ganglia (DRG and cranial sensory ganglia no longer bifurcate, and instead turn in either an ascending or a descending direction. In contrast, collateral axonal branch formation which represents a second type of axonal branch formation is not affected by inactivation of CNP, Npr2, or cGKI. Whereas axon bifurcation was lost in mouse mutants deficient for components of CNP-induced cGMP formation; the absence of the cGMP-degrading enzyme phosphodiesterase 2A had no effect on axon bifurcation. Adult mice that lack sensory axon bifurcation due to the conditional inactivation of Npr2-mediated cGMP signaling in DRG neurons demonstrated an altered shape of sensory axon terminal fields in the spinal cord, indicating that elaborate compensatory mechanisms reorganize neuronal circuits in the absence of bifurcation. On a functional level, these mice showed impaired heat sensation and nociception induced by chemical irritants, whereas responses to cold sensation, mechanical stimulation, and motor coordination are normal. These data point to a critical role of axon bifurcation for the processing of acute pain perception.

  6. Axonal interferon responses and alphaherpesvirus neuroinvasion (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

  7. Torsional Behavior of Axonal Microtubule Bundles (United States)

    Lazarus, Carole; Soheilypour, Mohammad; Mofrad, Mohammad R.K.


    Axonal microtubule (MT) bundles crosslinked by microtubule-associated protein (MAP) tau are responsible for vital biological functions such as maintaining mechanical integrity and shape of the axon as well as facilitating axonal transport. Breaking and twisting of MTs have been previously observed in damaged undulated axons. Such breaking and twisting of MTs is suggested to cause axonal swellings that lead to axonal degeneration, which is known as “diffuse axonal injury”. In particular, overstretching and torsion of axons can potentially damage the axonal cytoskeleton. Following our previous studies on mechanical response of axonal MT bundles under uniaxial tension and compression, this work seeks to characterize the mechanical behavior of MT bundles under pure torsion as well as a combination of torsional and tensile loads using a coarse-grained computational model. In the case of pure torsion, a competition between MAP tau tensile and MT bending energies is observed. After three turns, a transition occurs in the mechanical behavior of the bundle that is characterized by its diameter shrinkage. Furthermore, crosslink spacing is shown to considerably influence the mechanical response, with larger MAP tau spacing resulting in a higher rate of turns. Therefore, MAP tau crosslinking of MT filaments protects the bundle from excessive deformation. Simultaneous application of torsion and tension on MT bundles is shown to accelerate bundle failure, compared to pure tension experiments. MAP tau proteins fail in clusters of 10–100 elements located at the discontinuities or the ends of MT filaments. This failure occurs in a stepwise fashion, implying gradual accumulation of elastic tensile energy in crosslinks followed by rupture. Failure of large groups of interconnecting MAP tau proteins leads to detachment of MT filaments from the bundle near discontinuities. This study highlights the importance of torsional loading in axonal damage after traumatic brain injury

  8. Activation of ganglion cells and axon bundles using epiretinal electrical stimulation. (United States)

    Grosberg, Lauren E; Ganesan, Karthik; Goetz, Georges A; Madugula, Sasidhar S; Bhaskhar, Nandita; Fan, Victoria; Li, Peter; Hottowy, Pawel; Dabrowski, Wladyslaw; Sher, Alexander; Litke, Alan M; Mitra, Subhasish; Chichilnisky, E J


    Epiretinal prostheses for treating blindness activate axon bundles, causing large, arc-shaped visual percepts that limit the quality of artificial vision. Improving the function of epiretinal prostheses therefore requires understanding and avoiding axon bundle activation. This study introduces a method to detect axon bundle activation on the basis of its electrical signature and uses the method to test whether epiretinal stimulation can directly elicit spikes in individual retinal ganglion cells without activating nearby axon bundles. Combined electrical stimulation and recording from isolated primate retina were performed using a custom multielectrode system (512 electrodes, 10-μm diameter, 60-μm pitch). Axon bundle signals were identified by their bidirectional propagation, speed, and increasing amplitude as a function of stimulation current. The threshold for bundle activation varied across electrodes and retinas, and was in the same range as the threshold for activating retinal ganglion cells near their somas. In the peripheral retina, 45% of electrodes that activated individual ganglion cells (17% of all electrodes) did so without activating bundles. This permitted selective activation of 21% of recorded ganglion cells (7% of expected ganglion cells) over the array. In one recording in the central retina, 75% of electrodes that activated individual ganglion cells (16% of all electrodes) did so without activating bundles. The ability to selectively activate a subset of retinal ganglion cells without axon bundles suggests a possible novel architecture for future epiretinal prostheses. NEW & NOTEWORTHY Large-scale multielectrode recording and stimulation were used to test how selectively retinal ganglion cells can be electrically activated without activating axon bundles. A novel method was developed to identify axon activation on the basis of its unique electrical signature and was used to find that a subset of ganglion cells can be activated at single

  9. Hydrogels as scaffolds and delivery systems to enhance axonal regeneration after injuries

    Directory of Open Access Journals (Sweden)

    Oscar A. Carballo-Molina


    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

  10. IMP2 axonal localization, RNA interactome, and function in the development of axon trajectories

    DEFF Research Database (Denmark)

    Preitner, Nicolas; Quan, Jie; Li, Xinmin


    RNA-based regulatory mechanisms play important roles in the development and plasticity of neural circuits and neurological disease. Developing axons provide a model well suited to the study of RNA-based regulation, and contain specific subsets of mRNAsthat are locally translated and have roles...... to strong defects in commissural axon trajectories at the midline intermediate target. These results reveal a highly distinctive axonal enrichment of IMP2, show that it interacts with a network of axon guidance-related mRNAs, and reveal that it is required for normal axon pathfinding during vertebrate...

  11. Regulated viral BDNF delivery in combination with Schwann cells promotes axonal regeneration through capillary alginate hydrogels after spinal cord injury. (United States)

    Liu, Shengwen; Sandner, Beatrice; Schackel, Thomas; Nicholson, LaShae; Chtarto, Abdelwahed; Tenenbaum, Liliane; Puttagunta, Radhika; Müller, Rainer; Weidner, Norbert; Blesch, Armin


    Grafting of cell-seeded alginate capillary hydrogels into a spinal cord lesion site provides an axonal bridge while physically directing regenerating axonal growth in a linear pattern. However, without an additional growth stimulus, bridging axons fail to extend into the distal host spinal cord. Here we examined whether a combinatory strategy would support regeneration of descending axons across a cervical (C5) lateral hemisection lesion in the rat spinal cord. Following spinal cord transections, Schwann cell (SC)-seeded alginate hydrogels were grafted to the lesion site and AAV5 expressing brain-derived neurotrophic factor (BDNF) under control of a tetracycline-regulated promoter was injected caudally. In addition, we examined whether SC injection into the caudal spinal parenchyma would further enhance regeneration of descending axons to re-enter the host spinal cord. Our data show that both serotonergic and descending axons traced by biotinylated dextran amine (BDA) extend throughout the scaffolds. The number of regenerating axons is significantly increased when caudal BDNF expression is activated and transient BDNF delivery is able to sustain axons after gene expression is switched off. Descending axons are confined to the caudal graft/host interface even with continuous BDNF expression for 8weeks. Only with a caudal injection of SCs, a pathway facilitating axonal regeneration through the host/graft interface is generated allowing axons to successfully re-enter the caudal spinal cord. Recovery from spinal cord injury is poor due to the limited regeneration observed in the adult mammalian central nervous system. Biomaterials, cell transplantation and growth factors that can guide axons across a lesion site, provide a cellular substrate, stimulate axon growth and have shown some promise in increasing the growth distance of regenerating axons. In the present study, we combined an alginate biomaterial with linear channels with transplantation of Schwann cells within

  12. Squid Giant Axons Synthesize NF Proteins. (United States)

    Crispino, Marianna; Chun, Jong Tai; Giuditta, Antonio


    Squid giant axon has been an excellent model system for studying fundamental topics in neurobiology such as neuronal signaling. It has been also useful in addressing the questions of local protein synthesis in the axons. Incubation of isolated squid giant axons with [ 35 S]methionine followed by immunoprecipitation with a rabbit antibody against all squid neurofilament (NF) proteins demonstrates the local synthesis of a major 180 kDa NF protein and of several NF proteins of lower molecular weights. Their identification as NF proteins is based on their absence in the preimmune precipitates. Immunoprecipitates washed with more stringent buffers confirmed these results. Our data are at variance with a recent study based on the same experimental procedure that failed to visualize the local synthesis of NF proteins by the giant axon and thereby suggested their exclusive derivation from nerve cell bodies (as reported by Gainer et al. in Cell Mol Neurobiol 37:475-486, 2017). By reviewing the pertinent literature, we confute the claims that mRNA translation is absent in mature axons because of a putative translation block and that most proteins of mature axons are synthesized in the surrounding glial cells. Given the intrinsic axonal capacity to synthesize proteins, we stress the glial derivation of axonal and presynaptic RNAs and the related proposal that these neuronal domains are endowed with largely independent gene expression systems (as reported by Giuditta et al. in Physiol Rev 88:515-555, 2008).

  13. Ascending Midbrain Dopaminergic Axons Require Descending GAD65 Axon Fascicles for Normal Pathfinding

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    Claudia Marcela Garcia-Peña


    Full Text Available The Nigrostriatal pathway (NSP is formed by dopaminergic axons that project from the ventral midbrain to the dorsolateral striatum as part of the medial forebrain bundle. Previous studies have implicated chemotropic proteins in the formation of the NSP during development but little is known of the role of substrate-anchored signals in this process. We observed in mouse and rat embryos that midbrain dopaminergic axons ascend in close apposition to descending GAD65-positive axon bundles throughout their trajectory to the striatum. To test whether such interaction is important for dopaminergic axon pathfinding, we analyzed transgenic mouse embryos in which the GAD65 axon bundle was reduced by the conditional expression of the diphtheria toxin. In these embryos we observed dopaminergic misprojection into the hypothalamic region and abnormal projection in the striatum. In addition, analysis of Robo1/2 and Slit1/2 knockout embryos revealed that the previously described dopaminergic misprojection in these embryos is accompanied by severe alterations in the GAD65 axon scaffold. Additional studies with cultured dopaminergic neurons and whole embryos suggest that NCAM and Robo proteins are involved in the interaction of GAD65 and dopaminergic axons. These results indicate that the fasciculation between descending GAD65 axon bundles and ascending dopaminergic axons is required for the stereotypical NSP formation during brain development and that known guidance cues may determine this projection indirectly by instructing the pathfinding of the axons that are part of the GAD65 axon scaffold.

  14. Dynamics of mitochondrial transport in axons

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    Robert Francis Niescier


    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.

  15. The Genetics of Axon Guidance and Axon Regeneration in Caenorhabditis elegans (United States)

    Chisholm, Andrew D.; Hutter, Harald; Jin, Yishi; Wadsworth, William G.


    The correct wiring of neuronal circuits depends on outgrowth and guidance of neuronal processes during development. In the past two decades, great progress has been made in understanding the molecular basis of axon outgrowth and guidance. Genetic analysis in Caenorhabditis elegans has played a key role in elucidating conserved pathways regulating axon guidance, including Netrin signaling, the slit Slit/Robo pathway, Wnt signaling, and others. Axon guidance factors were first identified by screens for mutations affecting animal behavior, and by direct visual screens for axon guidance defects. Genetic analysis of these pathways has revealed the complex and combinatorial nature of guidance cues, and has delineated how cues guide growth cones via receptor activity and cytoskeletal rearrangement. Several axon guidance pathways also affect directed migrations of non-neuronal cells in C. elegans, with implications for normal and pathological cell migrations in situations such as tumor metastasis. The small number of neurons and highly stereotyped axonal architecture of the C. elegans nervous system allow analysis of axon guidance at the level of single identified axons, and permit in vivo tests of prevailing models of axon guidance. C. elegans axons also have a robust capacity to undergo regenerative regrowth after precise laser injury (axotomy). Although such axon regrowth shares some similarities with developmental axon outgrowth, screens for regrowth mutants have revealed regeneration-specific pathways and factors that were not identified in developmental screens. Several areas remain poorly understood, including how major axon tracts are formed in the embryo, and the function of axon regeneration in the natural environment. PMID:28114100

  16. Axon Termination, Pruning, and Synaptogenesis in the Giant Fiber System of Drosophila melanogaster Is Promoted by Highwire. (United States)

    Borgen, Melissa; Rowland, Kimberly; Boerner, Jana; Lloyd, Brandon; Khan, Aruna; Murphey, Rodney


    The ubiquitin ligase Highwire has a conserved role in synapse formation. Here, we show that Highwire coordinates several facets of central synapse formation in the Drosophila melanogaster giant fiber system, including axon termination, axon pruning, and synaptic function. Despite the similarities to the fly neuromuscular junction, the role of Highwire and the underlying signaling pathways are distinct in the fly's giant fiber system. During development, branching of the giant fiber presynaptic terminal occurs and, normally, the transient branches are pruned away. However, in highwire mutants these ectopic branches persist, indicating that Highwire promotes axon pruning. highwire mutants also exhibit defects in synaptic function. Highwire promotes axon pruning and synaptic function cell-autonomously by attenuating a mitogen-activated protein kinase pathway including Wallenda, c-Jun N-terminal kinase/Basket, and the transcription factor Jun. We also show a novel role for Highwire in non-cell autonomous promotion of synaptic function from the midline glia. Highwire also regulates axon termination in the giant fibers, as highwire mutant axons exhibit severe overgrowth beyond the pruning defect. This excessive axon growth is increased by manipulating Fos expression in the cells surrounding the giant fiber terminal, suggesting that Fos regulates a trans -synaptic signal that promotes giant fiber axon growth. Copyright © 2017 by the Genetics Society of America.

  17. Developmental downregulation of LIS1 expression limits axonal extension and allows axon pruning

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    Kanako Kumamoto


    Full Text Available The robust axonal growth and regenerative capacities of young neurons decrease substantially with age. This developmental downregulation of axonal growth may facilitate axonal pruning and neural circuit formation but limits functional recovery following nerve damage. While external factors influencing axonal growth have been extensively investigated, relatively little is known about the intrinsic molecular changes underlying the age-dependent reduction in regeneration capacity. We report that developmental downregulation of LIS1 is responsible for the decreased axonal extension capacity of mature dorsal root ganglion (DRG neurons. In contrast, exogenous LIS1 expression or endogenous LIS1 augmentation by calpain inhibition restored axonal extension capacity in mature DRG neurons and facilitated regeneration of the damaged sciatic nerve. The insulator protein CTCF suppressed LIS1 expression in mature DRG neurons, and this reduction resulted in excessive accumulation of phosphoactivated GSK-3β at the axon tip, causing failure of the axonal extension. Conversely, sustained LIS1 expression inhibited developmental axon pruning in the mammillary body. Thus, LIS1 regulation may coordinate the balance between axonal growth and pruning during maturation of neuronal circuits.

  18. Dynamics of target recognition by interstitial axon branching along developing cortical axons. (United States)

    Bastmeyer, M; O'Leary, D D


    Corticospinal axons innervate their midbrain, hindbrain, and spinal targets by extending collateral branches interstitially along their length. To establish that the axon shaft rather than the axonal growth cone is responsible for target recognition in this system, and to characterize the dynamics of interstitial branch formation, we have studied this process in an in vivo-like setting using slice cultures from neonatal mice containing the entire pathway of corticospinal axons. Corticospinal axons labeled with the dye 1,1'-dioctodecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate (or Dil) were imaged using time-lapse video microscopy of their pathway overlying the basilar pons, their major hindbrain target. The axon shaft millimeters behind the growth cone exhibits several dynamic behaviors, including the de novo formation of varicosities and filopodia-like extensions, and a behavior that we term "pulsation," which is characterized by a variable thickening and thining of short segments of the axon. An individual axon can have multiple sites of branching activity, with many of the branches being transient. These dynamic behaviors occur along the portion of the axon shaft overlying the basilar pons, but not just caudal to it. Once the collaterals extend into the pontine neuropil, they branch further in the neuropil, while the parent axon becomes quiescent. Thus, the branching activity is spatially restricted to specific portions of the axon, as well as temporally restricted to a relatively brief time window. These findings provide definitive evidence that collateral branches form de novo along corticospinal axons and establish that the process of target recognition in this system is a property of the axon shaft rather than the leading growth cone.

  19. Axonal wiring in neural development: Target-independent mechanisms help to establish precision and complexity. (United States)

    Petrovic, Milan; Schmucker, Dietmar


    The connectivity patterns of many neural circuits are highly ordered and often impressively complex. The intricate order and complexity of neuronal wiring remain not only a challenge for questions related to circuit functions but also for our understanding of how they develop with such an apparent precision. The chemotropic guidance of the growing axon by target-derived cues represents a central paradigm for how neurons get connected with the correct target cells. However, many studies reveal a remarkable variety of important target-independent wiring mechanisms. These mechanisms include axonal sorting, axonal tiling, growth cone polarization, as well as cell-intrinsic mechanisms underlying growth cone sprouting, and neurite branching. Our review focuses on target independent wiring mechanisms and in particular on recent progress emerging from studies on three different sensory systems: olfactory, visual, and somatosensory. We discuss molecular mechanisms that operate during axon-axon interactions or constitute axon-intrinsic functions and outline how they complement the well-known target-dependent wiring mechanisms. © 2015 WILEY Periodicals, Inc.

  20. Cargo distributions differentiate pathological axonal transport impairments. (United States)

    Mitchell, Cassie S; Lee, Robert H


    Axonal transport is an essential process in neurons, analogous to shipping goods, by which energetic and cellular building supplies are carried downstream (anterogradely) and wastes are carried upstream (retrogradely) by molecular motors, which act as cargo porters. Impairments in axonal transport have been linked to devastating and often lethal neurodegenerative diseases, such as Amyotrophic Lateral Sclerosis, Huntington's, and Alzheimer's. Axonal transport impairment types include a decrease in available motors for cargo transport (motor depletion), the presence of defective or non-functional motors (motor dilution), and the presence of increased or larger cargos (protein aggregation). An impediment to potential treatment identification has been the inability to determine what type(s) of axonal transport impairment candidates that could be present in a given disease. In this study, we utilize a computational model and common axonal transport experimental metrics to reveal the axonal transport impairment general characteristics or "signatures" that result from three general defect types of motor depletion, motor dilution, and protein aggregation. Our results not only provide a means to discern these general impairments types, they also reveal key dynamic and emergent features of axonal transport, which potentially underlie multiple impairment types. The identified characteristics, as well as the analytical method, can be used to help elucidate the axonal transport impairments observed in experimental and clinical data. For example, using the model-predicted defect signatures, we identify the defect candidates, which are most likely to be responsible for the axonal transport impairments in the G93A SOD1 mouse model of ALS. Copyright © 2012 Elsevier Ltd. All rights reserved.

  1. EphA4 blockers promote axonal regeneration and functional recovery following spinal cord injury in mice.

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    Yona Goldshmit

    Full Text Available Upregulation and activation of developmental axon guidance molecules, such as semaphorins and members of the Eph receptor tyrosine kinase family and their ligands, the ephrins, play a role in the inhibition of axonal regeneration following injury to the central nervous system. Previously we have demonstrated in a knockout model that axonal regeneration following spinal cord injury is promoted in the absence of the axon guidance protein EphA4. Antagonism of EphA4 was therefore proposed as a potential therapy to promote recovery from spinal cord injury. To further assess this potential, two soluble recombinant blockers of EphA4, unclustered ephrin-A5-Fc and EphA4-Fc, were examined for their ability to promote axonal regeneration and to improve functional outcome following spinal cord hemisection in wildtype mice. A 2-week administration of either of these blockers following spinal cord injury was sufficient to promote substantial axonal regeneration and functional recovery by 5 weeks following injury. Both inhibitors produced a moderate reduction in astrocytic gliosis, indicating that much of the effect of the blockers may be due to promotion of axon growth. These studies provide definitive evidence that soluble inhibitors of EphA4 function offer considerable therapeutic potential for the treatment of spinal cord injury and may have broader potential for the treatment of other central nervous system injuries.

  2. Mapping axonal density and average diameter using non-monotonic time-dependent gradient-echo MRI

    DEFF Research Database (Denmark)

    Nunes, Daniel; Cruz, Tomás L; Jespersen, Sune N


    Abstract White Matter (WM) microstructures, such as axonal density and average diameter, are crucial to the normal function of the Central Nervous System (CNS) as they are closely related with axonal conduction velocities. Conversely, disruptions of these microstructural features may result......, the axonal density can be extracted. We then experimentally demonstrate that maps derived from MGE acquired at 16.4 T in ex-vivo spinal cords, where the different tracts characterized by different microstructures are clearly contrasted in parametric maps extracted by fitting the MGE decay to the model. When...

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

    Directory of Open Access Journals (Sweden)

    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

  4. Drug therapy for chronic idiopathic axonal polyneuropathy

    NARCIS (Netherlands)

    Vrancken, A. F. J. E.; van Schaik, I. N.; Hughes, R. A. C.; Notermans, N. C.


    BACKGROUND: Chronic idiopathic axonal polyneuropathy is an insidiously progressive sensory or sensorimotor polyneuropathy that affects elderly people. Although severe disability or handicap does not occur, it reduces quality of life. OBJECTIVES: To assess whether drug therapy for chronic idiopathic

  5. In vitro autoradiographic localization of vasoactive intestinal peptide (VIP) binding sites in the rat central nervous system

    International Nuclear Information System (INIS)

    Besson, J.; Dussaillant, M.; Marie, J.C.; Rostene, W.; Rosselin, G.


    This paper describes the autoradiographic distribution of VIP binding sites in the rat central nervous system using monoiodinated 125I-labeled VIP. High densities of VIP binding sites are observed in the granular layer of the dorsal dentate gyrus of the hippocampus, the basolateral amygdaloid nucleus, the dorsolateral and median geniculate nuclei of the thalamus as well as in the ventral part of the hypothalamic dorsomedial nucleus

  6. EFA6 regulates selective polarised transport and axon regeneration from the axon initial segment

    Czech Academy of Sciences Publication Activity Database

    Eva, R.; Koseki, H.; Kanamarlapudi, V.; Fawcett, James


    Roč. 130, č. 21 (2017), s. 3663-3675 ISSN 0021-9533 Institutional support: RVO:68378041 Keywords : axon regeneration * axon transport * neuronal polarisation Subject RIV: FH - Neurology OBOR OECD: Neurosciences (including psychophysiology Impact factor: 4.431, year: 2016

  7. Axon initial segment Kv1 channels control axonal action potential waveform and synaptic efficacy

    NARCIS (Netherlands)

    Kole, Maarten H. P.; Letzkus, Johannes J.; Stuart, Greg J.


    Action potentials are binary signals that transmit information via their rate and temporal pattern. In this context, the axon is thought of as a transmission line, devoid of a role in neuronal computation. Here, we show a highly localized role of axonal Kv1 potassium channels in shaping the action

  8. Rescuing axons from degeneration does not affect retinal ganglion cell death

    Directory of Open Access Journals (Sweden)

    S. de Lima


    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.

  9. Intraneural Injection of ATP Stimulates Regeneration of Primary Sensory Axons in the Spinal Cord. (United States)

    Wu, Dongsheng; Lee, Sena; Luo, Juan; Xia, Haijian; Gushchina, Svetlana; Richardson, Peter M; Yeh, John; Krügel, Ute; Franke, Heike; Zhang, Yi; Bo, Xuenong


    Injury to the peripheral axons of sensory neurons strongly enhances the regeneration of their central axons in the spinal cord. It remains unclear on what molecules that initiate such conditioning effect. Because ATP is released extracellularly by nerve and other tissue injury, we hypothesize that injection of ATP into a peripheral nerve might mimic the stimulatory effect of nerve injury on the regenerative state of the primary sensory neurons. We found that a single injection of 6 μl of 150 μm ATP into female rat sciatic nerve quadrupled the number of axons growing into a lesion epicenter in spinal cord after a concomitant dorsal column transection. A second boost ATP injection 1 week after the first one markedly reinforced the stimulatory effect of a single injection. Single ATP injection increased expression of phospho-STAT3 and GAP43, two markers of regenerative activity, in sensory neurons. Double ATP injections sustained the activation of phospho-STAT3 and GAP43, which may account for the marked axonal growth across the lesion epicenter. Similar studies performed on P2X7 or P2Y2 receptor knock-out mice indicate P2Y2 receptors are involved in the activation of STAT3 after ATP injection or conditioning lesion, whereas P2X7 receptors are not. Injection of ATP at 150 μm caused little Wallerian degeneration and behavioral tests showed no significant long-term adverse effects on sciatic nerve functions. The results in this study reveal possible mechanisms underlying the stimulation of regenerative programs and suggest a practical strategy for stimulating axonal regeneration following spinal cord injury. SIGNIFICANCE STATEMENT Injury of peripheral axons of sensory neurons has been known to strongly enhance the regeneration of their central axons in the spinal cord. In this study, we found that injection of ATP into a peripheral nerve can mimic the effect of peripheral nerve injury and significantly increase the number of sensory axons growing across lesion

  10. Cross-talk between KLF4 and STAT3 regulates axon regeneration (United States)

    Qin, Song; Zou, Yuhua; Zhang, Chun-Li


    Cytokine-induced activation of signal transducer and activator of transcription 3 (STAT3) promotes the regrowth of damaged axons in the adult central nervous system (CNS). Here we show that KLF4 physically interacts with STAT3 upon cytokine-induced phosphorylation of tyrosine 705 (Y705) on STAT3. This interaction suppresses STAT3-dependent gene expression by blocking its DNA-binding activity. The deletion of KLF4 in vivo induces axon regeneration of adult retinal ganglion cells (RGCs) via Janus kinase (JAK)-STAT3 signalling. This regeneration can be greatly enhanced by exogenous cytokine treatment, or removal of an endogenous JAK-STAT3 pathway inhibitor called suppressor of cytokine signalling 3 (SOCS3). These findings reveal an unexpected cross-talk between KLF4 and activated STAT3 in the regulation of axon regeneration that might have therapeutic implications in promoting repair of injured adult CNS.

  11. Guidance of retinal axons in mammals. (United States)

    Herrera, Eloísa; Erskine, Lynda; Morenilla-Palao, Cruz


    In order to navigate through the surrounding environment many mammals, including humans, primarily rely on vision. The eye, composed of the choroid, sclera, retinal pigmented epithelium, cornea, lens, iris and retina, is the structure that receives the light and converts it into electrical impulses. The retina contains six major types of neurons involving in receiving and modifying visual information and passing it onto higher visual processing centres in the brain. Visual information is relayed to the brain via the axons of retinal ganglion cells (RGCs), a projection known as the optic pathway. The proper formation of this pathway during development is essential for normal vision in the adult individual. Along this pathway there are several points where visual axons face 'choices' in their direction of growth. Understanding how these choices are made has advanced significantly our knowledge of axon guidance mechanisms. Thus, the development of the visual pathway has served as an extremely useful model to reveal general principles of axon pathfinding throughout the nervous system. However, due to its particularities, some cellular and molecular mechanisms are specific for the visual circuit. Here we review both general and specific mechanisms involved in the guidance of mammalian RGC axons when they are traveling from the retina to the brain to establish precise and stereotyped connections that will sustain vision. Copyright © 2017 Elsevier Ltd. All rights reserved.

  12. The progeroid gene BubR1 regulates axon myelination and motor function. (United States)

    Choi, Chan-Il; Yoo, Ki Hyun; Hussaini, Syed Mohammed Qasim; Jeon, Byeong Tak; Welby, John; Gan, Haiyun; Scarisbrick, Isobel A; Zhang, Zhiguo; Baker, Darren J; van Deursen, Jan M; Rodriguez, Moses; Jang, Mi-Hyeon


    Myelination, the process by which oligodendrocytes form the myelin sheath around axons, is key to axonal signal transduction and related motor function in the central nervous system (CNS). Aging is characterized by degenerative changes in the myelin sheath, although the molecular underpinnings of normal and aberrant myelination remain incompletely understood. Here we report that axon myelination and related motor function are dependent on BubR1, a mitotic checkpoint protein that has been linked to progeroid phenotypes when expressed at low levels and healthy lifespan when overabundant. We found that oligodendrocyte progenitor cell proliferation and oligodendrocyte density is markedly reduced in mutant mice with low amounts of BubR1 ( BubR1 H/H mice), causing axonal hypomyelination in both brain and spinal cord. Expression of essential myelin-related genes such as MBP and PLP1 was significantly reduced in these tissues. Consistent with defective myelination, BubR1 H/H mice exhibited various motor deficits, including impaired motor strength, coordination, and balance, irregular gait patterns and reduced locomotor activity. Collectively, these data suggest that BubR1 is a key determinant of oligodendrocyte production and function and provide a molecular entry point to understand age-related degenerative changes in axon myelination.

  13. Hyaluronic acid hydrogels with IKVAV peptides for tissue repair and axonal regeneration in an injured rat brain

    Energy Technology Data Exchange (ETDEWEB)

    Wei, Y T [Biomaterials Laboratory, Department of Materials Science and Engineering, Tsinghua University, Beijing, 100084 (China); Tian, W M [Biomaterials Laboratory, Department of Materials Science and Engineering, Tsinghua University, Beijing, 100084 (China); Yu, X [Biomaterials Laboratory, Department of Materials Science and Engineering, Tsinghua University, Beijing, 100084 (China); Cui, F Z [Biomaterials Laboratory, Department of Materials Science and Engineering, Tsinghua University, Beijing, 100084 (China); Hou, S P [Beijing Institute of Neuroscience, Capital University of Medical Sciences, Beijing, 100054 (China); Xu, Q Y [Beijing Institute of Neuroscience, Capital University of Medical Sciences, Beijing, 100054 (China); Lee, In-Seop [Institute of Physics and Applied Physics, and Atomic-scale Surface Science Research Center, Yonsei University, Seoul 120-749 (Korea, Republic of)


    A biocompatible hydrogel of hyaluronic acid with the neurite-promoting peptide sequence of IKVAV was synthesized. The characterization of the hydrogel shows an open porous structure and a large surface area available for cell interaction. Its ability to promote tissue repair and axonal regeneration in the lesioned rat cerebrum is also evaluated. After implantation, the polymer hydrogel repaired the tissue defect and formed a permissive interface with the host tissue. Axonal growth occurred within the microstructure of the network. Within 6 weeks the polymer implant was invaded by host-derived tissue, glial cells, blood vessels and axons. Such a hydrogel matrix showed the properties of neuron conduction. It has the potential to repair tissue defects in the central nervous system by promoting the formation of a tissue matrix and axonal growth by replacing the lost tissue.

  14. Glial progenitor cell migration promotes CNS axon growth on functionalized electroconducting microfibers. (United States)

    Collazos-Castro, Jorge E; García-Rama, Concepción; Alves-Sampaio, Alexandra


    Electroactive systems that promote directional axonal growth and migration of glial progenitor cells (GPC) are needed for the treatment of neurological injuries. We report the functionalization of electroconducting microfibers with multiple biomolecules that synergistically stimulate the proliferation and migration of GPC, which in turn induce axonal elongation from embryonic cerebral cortex neurons. PEDOT doped with poly[(4-styrenesulfonic acid)-co-(maleic acid)] was synthesized on carbon microfibers and used for covalent attachment of molecules to the electroactive surface. The molecular complexes that promoted GPC proliferation and migration, followed by axonal extension, were composed of polylysine, heparin, basic fibroblast growth factor (bFGF), and matricellular proteins; the combination of bFGF with vitronectin or fibronectin being indispensable for sustained glial and axonal growth. The rate of glial-induced axonal elongation was about threefold that of axons growing directly on microfibers functionalized with polylysine alone. Electrical stimuli applied through the microfibers released bFGF and fibronectin from the polymer surface, consequently reducing GPC proliferation and promoting their differentiation into astrocytes, without causing cell detachment or toxicity. These results suggest that functionalized electroactive microfibers may provide a multifunctional tool for controlling neuron-glia interactions and enhancing neural repair. We report a multiple surface functionalization strategy for electroconducting microfibers (MFs), in order to promote proliferation and guided migration of glial precursor cells (GPC) and consequently create a permissive substrate for elongation of central nervous system (CNS) axons. GPC divided and migrated extensively on the functionalized MFs, leading to fast elongation of embryonic cerebral cortex axons. The application of electric pulses thorough the MFs controlled glial cell division and differentiation. The

  15. The effect of myelinating Schwann cells on axons. (United States)

    Martini, R


    Myelinating Schwann cells control the number of neurofilaments and elevate the phosphorylation state of neurofilaments in the axon, eventually leading to the typical large axon caliber. Conversely, absence of myelin leads to lower amounts of neurofilaments, reduced phosphorylation levels, and smaller axon diameters. In addition, myelinating Schwann cells mediate the spacing of Na(+) channel clusters during development of the node of Ranvier. When axons are associated with mutant Schwann cells in inherited neuropathies, their calibers are reduced and their neurofilaments are less phosphorylated and more closely spaced. Also, axonal transport is reduced and axons degenerate at the distal ends of long nerves. Myelin-associated glycoprotein may mediate some aspects of Schwann cell-axon communication, but much remains to be learned about the molecular bases of Schwann cell-axon communication. Copyright 2001 John Wiley & Sons, Inc.

  16. Modeling molecular mechanisms in the axon (United States)

    de Rooij, R.; Miller, K.E.; Kuhl, E.


    Axons are living systems that display highly dynamic changes in stiffness, viscosity, and internal stress. However, the mechanistic origin of these phenomenological properties remains elusive. Here we establish a computational mechanics model that interprets cellular-level characteristics as emergent properties from molecular-level events. We create an axon model of discrete microtubules, which are connected to neighboring microtubules via discrete crosslinking mechanisms that obey a set of simple rules. We explore two types of mechanisms: passive and active crosslinking. Our passive and active simulations suggest that the stiffness and viscosity of the axon increase linearly with the crosslink density, and that both are highly sensitive to the crosslink detachment and reattachment times. Our model explains how active crosslinking with dynein motors generates internal stresses and actively drives axon elongation. We anticipate that our model will allow us to probe a wide variety of molecular phenomena–both in isolation and in interaction–to explore emergent cellular-level features under physiological and pathological conditions. PMID:28603326

  17. Macrophages Promote Axon Regeneration with Concurrent Neurotoxicity

    NARCIS (Netherlands)

    Gensel, J.C.; Nakamura, S.; Guan, Z.; Rooijen, van N.; Ankeny, D.P.; Popovich, P.G.


    Activated macrophages can promote regeneration of CNS axons. However, macrophages also release factors that kill neurons. These opposing functions are likely induced simultaneously but are rarely considered together in the same experimental preparation. A goal of this study was to unequivocally

  18. Regulation of axon arborization pattern in the developing chick ciliary ganglion: Possible involvement of caspase 3. (United States)

    Katow, Hidetaka; Kanaya, Teppei; Ogawa, Tomohisa; Egawa, Ryo; Yawo, Hiromu


    During a certain critical period in the development of the central and peripheral nervous systems, axonal branches and synapses are massively reorganized to form mature connections. In this process, neurons search their appropriate targets, expanding and/or retracting their axons. Recent work suggested that the caspase superfamily regulates the axon morphology. Here, we tested the hypothesis that caspase 3, which is one of the major executioners in apoptotic cell death, is involved in regulating the axon arborization. The embryonic chicken ciliary ganglion was used as a model system of synapse reorganization. A dominant negative mutant of caspase-3 precursor (C3DN) was made and overexpressed in presynaptic neurons in the midbrain to interfere with the intrinsic caspase-3 activity using an in ovo electroporation method. The axon arborization pattern was 3-dimensionally and quantitatively analyzed in the ciliary ganglion. The overexpression of C3DN significantly reduced the number of branching points, the branch order and the complexity index, whereas it significantly elongated the terminal branches at E6. It also increased the internodal distance significantly at E8. But, these effects were negligible at E10 or later. During E6-8, there appeared to be a dynamic balance in the axon arborization pattern between the "targeting" mode, which is accompanied by elongation of terminal branches and the pruning of collateral branches, and the "pathfinding" mode, which is accompanied by the retraction of terminal branches and the sprouting of new collateral branches. The local and transient activation of caspase 3 could direct the balance towards the pathfinding mode. © 2017 Japanese Society of Developmental Biologists.

  19. Mouse Intermittent Hypoxia Mimicking Apnea of Prematurity: Effects on Myelinogenesis and Axonal Maturation (United States)



    Premature babies are at high risk for both infantile apnea and long-term neurobehavioral deficits. Recent studies suggest that diffuse structural changes in brain white matter are a positive predictor of poor cognitive outcomes. Since oligodendrocyte maturation, myelination, axon development and synapse formation mainly occur in the 3rd trimester of gestation and 1st postnatal year, infantile apnea could lead to and/or exaggerate white matter impairments in preterm neonates. Therefore, we investigated oligodendroglia and axon development in a neonatal mouse model of intermittent hypoxia between postnatal days 2 to 10. During critical phases of central nervous system development, intermittent hypoxia induced hypomyelination in the corpus callosum, striatum, fornix and cerebellum, but not the pons or spinal cord. Intermittent hypoxia-elicited alterations in myelin-forming processes were reflected by decreased expression of myelin proteins, including MBP, PLP, MAG and CNPase, possibly due to arrested maturation of oligodendrocytes. Ultra-structural abnormalities were apparent in the myelin sheath and axon. Immature oligodendrocytes were more vulnerable to neonatal intermittent hypoxia exposures than developing axons, suggesting that hypomyelination may contribute, at least partially, to axonal deficits. Insufficient neurofilament synthesis with anomalous components of neurofilament subunits, β-tubulin and MAP2 isoforms indicated immaturity of axons in intermittent hypoxia-exposed mouse brains. In addition, down-regulation of Synapsin I, Synaptophysin and Gap-43 phosphorylation suggested a potential stunt in axonogenesis and synaptogenesis. The region-selective and complex impairment in brain white matter induced by intermittent hypoxia was further associated with electrophysiological changes that may underlie long-term neurobehavioral sequelae. PMID:21953180

  20. Tri-partite complex for axonal transport drug delivery achieves pharmacological effect

    Directory of Open Access Journals (Sweden)

    Frederickson Martyn


    Full Text Available Abstract Background Targeted delivery of pharmaceutical agents into selected populations of CNS (Central Nervous System neurons is an extremely compelling goal. Currently, systemic methods are generally used for delivery of pain medications, anti-virals for treatment of dermatomal infections, anti-spasmodics, and neuroprotectants. Systemic side effects or undesirable effects on parts of the CNS that are not involved in the pathology limit efficacy and limit clinical utility for many classes of pharmaceuticals. Axonal transport from the periphery offers a possible selective route, but there has been little progress towards design of agents that can accomplish targeted delivery via this intraneural route. To achieve this goal, we developed a tripartite molecular construction concept involving an axonal transport facilitator molecule, a polymer linker, and a large number of drug molecules conjugated to the linker, then sought to evaluate its neurobiology and pharmacological behavior. Results We developed chemical synthesis methodologies for assembling these tripartite complexes using a variety of axonal transport facilitators including nerve growth factor, wheat germ agglutinin, and synthetic facilitators derived from phage display work. Loading of up to 100 drug molecules per complex was achieved. Conjugation methods were used that allowed the drugs to be released in active form inside the cell body after transport. Intramuscular and intradermal injection proved effective for introducing pharmacologically effective doses into selected populations of CNS neurons. Pharmacological efficacy with gabapentin in a paw withdrawal latency model revealed a ten fold increase in half life and a 300 fold decrease in necessary dose relative to systemic administration for gabapentin when the drug was delivered by axonal transport using the tripartite vehicle. Conclusion Specific targeting of selected subpopulations of CNS neurons for drug delivery by axonal

  1. 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 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.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.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.

  2. Mitochondria Localize to Injured Axons to Support Regeneration. (United States)

    Han, Sung Min; Baig, Huma S; Hammarlund, Marc


    Axon regeneration is essential to restore the nervous system after axon injury. However, the neuronal cell biology that underlies axon regeneration is incompletely understood. Here we use in vivo, single-neuron analysis to investigate the relationship between nerve injury, mitochondrial localization, and axon regeneration. Mitochondria translocate into injured axons so that average mitochondria density increases after injury. Moreover, single-neuron analysis reveals that axons that fail to increase mitochondria have poor regeneration. Experimental alterations to axonal mitochondrial distribution or mitochondrial respiratory chain function result in corresponding changes to regeneration outcomes. Axonal mitochondria are specifically required for growth-cone migration, identifying a key energy challenge for injured neurons. Finally, mitochondrial localization to the axon after injury is regulated in part by dual-leucine zipper kinase 1 (DLK-1), a conserved regulator of axon regeneration. These data identify regulation of axonal mitochondria as a new cell-biological mechanism that helps determine the regenerative response of injured neurons. Copyright © 2016 Elsevier Inc. All rights reserved.

  3. Diffuse Axonal Injury and Oxidative Stress: A Comprehensive Review

    Directory of Open Access Journals (Sweden)

    Alessandro Frati


    Full Text Available Traumatic brain injury (TBI is one of the world’s leading causes of morbidity and mortality among young individuals. TBI applies powerful rotational and translational forces to the brain parenchyma, which results in a traumatic diffuse axonal injury (DAI responsible for brain swelling and neuronal death. Following TBI, axonal degeneration has been identified as a progressive process that starts with disrupted axonal transport causing axonal swelling, followed by secondary axonal disconnection and Wallerian degeneration. These modifications in the axonal cytoskeleton interrupt the axoplasmic transport mechanisms, causing the gradual gathering of transport products so as to generate axonal swellings and modifications in neuronal homeostasis. Oxidative stress with consequent impairment of endogenous antioxidant defense mechanisms plays a significant role in the secondary events leading to neuronal death. Studies support the role of an altered axonal calcium homeostasis as a mechanism in the secondary damage of axon, and suggest that calcium channel blocker can alleviate the secondary damage, as well as other mechanisms implied in the secondary injury, and could be targeted as a candidate for therapeutic approaches. Reactive oxygen species (ROS-mediated axonal degeneration is mainly caused by extracellular Ca2+. Increases in the defense mechanisms through the use of exogenous antioxidants may be neuroprotective, particularly if they are given within the neuroprotective time window. A promising potential therapeutic target for DAI is to directly address mitochondria-related injury or to modulate energetic axonal energy failure.

  4. Diffuse Axonal Injury and Oxidative Stress: A Comprehensive Review. (United States)

    Frati, Alessandro; Cerretani, Daniela; Fiaschi, Anna Ida; Frati, Paola; Gatto, Vittorio; La Russa, Raffaele; Pesce, Alessandro; Pinchi, Enrica; Santurro, Alessandro; Fraschetti, Flavia; Fineschi, Vittorio


    Traumatic brain injury (TBI) is one of the world's leading causes of morbidity and mortality among young individuals. TBI applies powerful rotational and translational forces to the brain parenchyma, which results in a traumatic diffuse axonal injury (DAI) responsible for brain swelling and neuronal death. Following TBI, axonal degeneration has been identified as a progressive process that starts with disrupted axonal transport causing axonal swelling, followed by secondary axonal disconnection and Wallerian degeneration. These modifications in the axonal cytoskeleton interrupt the axoplasmic transport mechanisms, causing the gradual gathering of transport products so as to generate axonal swellings and modifications in neuronal homeostasis. Oxidative stress with consequent impairment of endogenous antioxidant defense mechanisms plays a significant role in the secondary events leading to neuronal death. Studies support the role of an altered axonal calcium homeostasis as a mechanism in the secondary damage of axon, and suggest that calcium channel blocker can alleviate the secondary damage, as well as other mechanisms implied in the secondary injury, and could be targeted as a candidate for therapeutic approaches. Reactive oxygen species (ROS)-mediated axonal degeneration is mainly caused by extracellular Ca 2+ . Increases in the defense mechanisms through the use of exogenous antioxidants may be neuroprotective, particularly if they are given within the neuroprotective time window. A promising potential therapeutic target for DAI is to directly address mitochondria-related injury or to modulate energetic axonal energy failure.

  5. The cytoskeleton-associated protein SCHIP1 is involved in axon guidance, and is required for piriform cortex and anterior commissure development. (United States)

    Klingler, Esther; Martin, Pierre-Marie; Garcia, Marta; Moreau-Fauvarque, Caroline; Falk, Julien; Chareyre, Fabrice; Giovannini, Marco; Chédotal, Alain; Girault, Jean-Antoine; Goutebroze, Laurence


    SCHIP1 is a cytoplasmic partner of cortical cytoskeleton ankyrins. The IQCJ-SCHIP1 isoform is a component of axon initial segments and nodes of Ranvier of mature axons in peripheral and central nervous systems, where it associates with membrane complexes comprising cell adhesion molecules. SCHIP1 is also expressed in the mouse developing central nervous system during embryonic stages of active axonogenesis. Here, we identify a new and early role for SCHIP1 during axon development and establishment of the anterior commissure (AC). The AC is composed of axons from the piriform cortex, the anterior olfactory nucleus and the amygdala. Schip1 mutant mice displayed early defects in AC development that might result from impaired axon growth and guidance. In addition, mutant mice presented a reduced thickness of the piriform cortex, which affected projection neurons in layers 2/3 and was likely to result from cell death rather than from impairment of neuron generation or migration. Piriform cortex neurons from E14.5 mutant embryos displayed axon initiation/outgrowth delay and guidance defects in vitro. The sensitivity of growth cones to semaphorin 3F and Eph receptor B2, two repulsive guidance cues crucial for AC development, was increased, providing a possible basis for certain fiber tract alterations. Thus, our results reveal new evidence for the involvement of cortical cytoskeleton-associated proteins in the regulation of axon development and their importance for the formation of neuronal circuits. © 2015. Published by The Company of Biologists Ltd.

  6. Motor axon excitability during Wallerian degeneration

    DEFF Research Database (Denmark)

    Moldovan, Mihai; Alvarez, Susana; Krarup, Christian


    Axonal loss and degeneration are major factors in determining long-term outcome in patients with peripheral nerve disorders or injury. Following loss of axonal continuity, the isolated nerve stump distal to the lesion undergoes Wallerian degeneration in several phases. In the initial 'latent' phase...... at ankle distal to axotomy were monitored by 'threshold-tracking'. The plantar compound muscle action potentials (CMAPs) were recorded under anesthesia in three animal models: 8-week-old wild-type mice, 8-week-old slow Wallerian degeneration mutant mice and 3-year-old cats. We found that the progressive...... decrease in CMAP following crush injury was associated with slowing of conduction and marked abnormalities in excitability: increased peak threshold deviations during both depolarizing and hyperpolarizing threshold electrotonus, enhanced superexcitability during the recovery cycle and increased rheobase...

  7. Sensory axonal dysfunction in cervical radiculopathy. (United States)

    Sung, Jia-Ying; Tani, Jowy; Hung, Kuo-Sheng; Lui, Tai-Ngar; Lin, Cindy Shin-Yi


    The aim of this study was to evaluate changes in sensory axonal excitability in the distal nerve in patients with cervical radiculopathy. The patients were classified by the findings of cervical MRI into two subgroups: 22 patients with C6/7 root compression and 25 patients with cervical cord and root compression above/at C6/7. Patients were investigated using conventional nerve conduction studies (NCS) and nerve excitability testing. Sensory nerve excitability testing was undertaken with stimulation at the wrist and recording from digit II (dermatome C6/7). The results were compared with healthy controls. Both preoperative and postoperative tests were performed if the patient underwent surgery. Sensory axonal excitability was significantly different in both cohorts compared with healthy controls, including prolonged strength-duration time constant, reduced S2 accommodation, increased threshold electrotonus hyperpolarisation (TEh (90-100 ms)), and increased superexcitability. The changes in these excitability indices are compatible with axonal membrane hyperpolarisation. In five patients who underwent surgery, the postoperative sensory excitability was tested after 1 week, and showed significant changes in TE (TEh (90-100 ms) and TEh slope, pcervical radiculopathy. These findings suggest that the hyperpolarised pattern might be due to Na(+)-K(+) ATPase overactivation induced by proximal ischaemia, or could reflect the remyelinating process. Distal sensory axons were hyperpolarised even though there were no changes in NCS, suggesting that nerve excitability testing may be more sensitive to clinical symptoms than NCS in patients with cervical radiculopathy. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to

  8. Unidirectional ephaptic stimulation between two myelinated axons. (United States)

    Capllonch-Juan, Miguel; Kolbl, Florian; Sepulveda, Francisco


    Providing realistic sensory feedback for prosthetic devices strongly relies on an accurate modelling of machine-nerve interfaces. Models of these interfaces in the peripheral nervous system usually neglect the effects that ephaptic coupling can have on the selectivity of stimulating electrodes. In this contribution, we study the ephaptic stimulation between myelinated axons and show its relation with the separation between fibers and the conductivity of the medium that surrounds them.

  9. Multifunctional Silk Nerve Guides for Axon Outgrowth (United States)

    Tupaj, Marie C.

    Peripheral nerve regeneration is a critical issue as 2.8% of trauma patients present with this type of injury, estimating a total of 200,000 nerve repair procedures yearly in the United States. While the peripheral nervous system exhibits slow regeneration, at a rate of 0.5 mm -- 9 mm/day following trauma, this regenerative ability is only possible under certain conditions. Clinical repairs have changed slightly in the last 30 years and standard methods of treatment include suturing damaged nerve ends, allografting, and autografting, with the autograft the gold standard of these approaches. Unfortunately, the use of autografts requires a second surgery and there is a shortage of nerves available for grafting. Allografts are a second option however allografts have lower success rates and are accompanied by the need of immunosuppressant drugs. Recently there has been a focus on developing nerve guides as an "off the shelf" approach. Although some natural and synthetic guidance channels have been approved by the FDA, these nerve guides are unfunctionalized and repair only short gaps, less than 3 cm in length. The goal of this project was to identify strategies for functionalizing peripheral nerve conduits for the outgrowth of neuron axons in vitro . To accomplish this, two strategies (bioelectrical and biophysical) were indentified for increasing axon outgrowth and promoting axon guidance. Bioelectrical strategies exploited electrical stimulation for increasing neurite outgrowth. Biophysical strategies tested a range of surface topographies for axon guidance. Novel methods were developed for integrating electrical and biophysical strategies into silk films in 2D. Finally, a functionalized nerve conduit system was developed that integrated all strategies for the purpose of attaching, elongating, and guiding nervous tissue in vitro. Future directions of this work include silk conduit translation into a rat sciatic nerve model in vivo for the purpose of repairing long

  10. Retinal ganglion cell survival and axon regeneration after optic nerve injury in naked mole-rats. (United States)

    Park, Kevin K; Luo, Xueting; Mooney, Skyler J; Yungher, Benjamin J; Belin, Stephane; Wang, Chen; Holmes, Melissa M; He, Zhigang


    In the adult mammalian central nervous system (CNS), axonal damage often triggers neuronal cell death and glial activation, with very limited spontaneous axon regeneration. In this study, we performed optic nerve injury in adult naked mole-rats, the longest living rodent, with a maximum life span exceeding 30 years, and found that injury responses in this species are quite distinct from those in other mammalian species. In contrast to what is seen in other mammals, the majority of injured retinal ganglion cells (RGCs) survive with relatively high spontaneous axon regeneration. Furthermore, injured RGCs display activated signal transducer and activator of transcription-3 (STAT3), whereas astrocytes in the optic nerve robustly occupy and fill the lesion area days after injury. These neuron-intrinsic and -extrinsic injury responses are reminiscent of those in "cold-blooded" animals, such as fish and amphibians, suggesting that the naked mole-rat is a powerful model for exploring the mechanisms of neuronal injury responses and axon regeneration in mammals. J. Comp. Neurol. 525:380-388, 2017. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

  11. Synaptic Democracy and Vesicular Transport in Axons (United States)

    Bressloff, Paul C.; Levien, Ethan


    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".

  12. 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


    axon guidance. OSNs continually undergo regeneration and hence require ongoing axon guidance. Neurogenesis and the regeneration of neurons and axons occur in other adult populations of peripheral and central neurons that also require axon guidance throughout life. Therefore, BACE1 inhibitors under development for the treatment of AD may potentially cause axon targeting defects in these neuronal populations as well.

  13. Axonal branching patterns of nucleus accumbens neurons in the rat. (United States)

    Tripathi, Anushree; Prensa, Lucía; Cebrián, Carolina; Mengual, Elisa


    The patterns of axonal collateralization of nucleus accumbens (Acb) projection neurons were investigated in the rat by means of single-axon tracing techniques using the anterograde tracer biotinylated dextran amine. Seventy-three axons were fully traced, originating from either the core (AcbC) or shell (AcbSh) compartment, as assessed by differential calbindin D28k-immunoreactivity. Axons from AcbC and AcbSh showed a substantial segregation in their targets; target areas were either exclusively or preferentially innervated from AcbC or AcbSh. Axon collaterals in the subthalamic nucleus were found at higher than expected frequencies; moreover, these originated exclusively in the dorsal AcbC. Intercompartmental collaterals were observed from ventral AcbC axons into AcbSh, and likewise, interconnections at pallidal and mesencephalic levels were also observed, although mostly from AcbC axons toward AcbSh targets, possibly supporting crosstalk between the two subcircuits at several levels. Cell somata giving rise to short-range accumbal axons, projecting to the ventral pallidum (VP), were spatially intermingled with others, giving rise to long-range axons that innervated VP and more caudal targets. This anatomical organization parallels that of the dorsal striatum and provides the basis for possible dual direct and indirect actions from a single axon on either individual or small sets of neurons. Copyright © 2010 Wiley-Liss, Inc.

  14. Axonal and Transynaptic Spread of Prions (United States)

    Shearin, Harold


    ABSTRACT Natural transmission of prion diseases depends upon the spread of prions from the nervous system to excretory or secretory tissues, but the mechanism of prion transport in axons and into peripheral tissue is unresolved. Here, we examined the temporal and spatial movement of prions from the brain stem along cranial nerves into skeletal muscle as a model of axonal transport and transynaptic spread. The disease-specific isoform of the prion protein, PrPSc, was observed in nerve fibers of the tongue approximately 2 weeks prior to PrPSc deposition in skeletal muscle. Initially, PrPSc deposits had a small punctate pattern on the edge of muscle cells that colocalized with synaptophysin, a marker for the neuromuscular junction (NMJ), in >50% of the cells. At later time points PrPSc was widely distributed in muscle cells, but PrPSc deposition at the NMJ, suggesting additional prion replication and dissemination within muscle cells. In contrast to the NMJ, PrPSc was not associated with synaptophysin in nerve fibers but was found to colocalize with LAMP-1 and cathepsin D during early stages of axonal spread. We propose that PrPSc-bound endosomes can lead to membrane recycling in which PrPSc is directed to the synapse, where it either moves across the NMJ into the postsynaptic muscle cell or induces PrPSc formation on muscle cells across the NMJ. IMPORTANCE Prion diseases are transmissible and fatal neurodegenerative diseases in which prion dissemination to excretory or secretory tissues is necessary for natural disease transmission. Despite the importance of this pathway, the cellular mechanism of prion transport in axons and into peripheral tissue is unresolved. This study demonstrates anterograde spread of prions within nerve fibers prior to infection of peripheral synapses (i.e., neuromuscular junction) and infection of peripheral tissues (i.e., muscle cells). Within nerve fibers prions were associated with the endosomal-lysosomal pathway prior to entry into

  15. Exposure to an open-field arena increases c-Fos expression in a subpopulation of neurons in the dorsal raphe nucleus, including neurons projecting to the basolateral amygdaloid complex

    DEFF Research Database (Denmark)

    Hale, M.W.; Hay-Schmidt, A.; Mikkelsen, J.D.


    . Treatment effects on c-Fos expression in serotonergic and non-serotonergic cells in the midbrain raphe nuclei were determined 2 h following open-field exposure or home cage control (CO) conditions. Rats tested under both light conditions responded with increases in c-Fos expression in serotonergic neurons...... of neurons in the midbrain raphe complex that projects to forebrain circuits regulating anxiety states, we used cholera toxin B subunit (CTb) as a retrograde tracer to identify neurons projecting to the basolateral amygdaloid complex (BL) in combination with c-Fos immunostaining to identify cells...

  16. Multichannel activity propagation across an engineered axon network (United States)

    Chen, H. Isaac; Wolf, John A.; Smith, Douglas H.


    Objective. Although substantial progress has been made in mapping the connections of the brain, less is known about how this organization translates into brain function. In particular, the massive interconnectivity of the brain has made it difficult to specifically examine data transmission between two nodes of the connectome, a central component of the ‘neural code.’ Here, we investigated the propagation of multiple streams of asynchronous neuronal activity across an isolated in vitro ‘connectome unit.’ Approach. We used the novel technique of axon stretch growth to create a model of a long-range cortico-cortical network, a modular system consisting of paired nodes of cortical neurons connected by axon tracts. Using optical stimulation and multi-electrode array recording techniques, we explored how input patterns are represented by cortical networks, how these representations shift as they are transmitted between cortical nodes and perturbed by external conditions, and how well the downstream node distinguishes different patterns. Main results. Stimulus representations included direct, synaptic, and multiplexed responses that grew in complexity as the distance between the stimulation source and recorded neuron increased. These representations collapsed into patterns with lower information content at higher stimulation frequencies. With internodal activity propagation, a hierarchy of network pathways, including latent circuits, was revealed using glutamatergic blockade. As stimulus channels were added, divergent, non-linear effects were observed in local versus distant network layers. Pairwise difference analysis of neuronal responses suggested that neuronal ensembles generally outperformed individual cells in discriminating input patterns. Significance. Our data illuminate the complexity of spiking activity propagation in cortical networks in vitro, which is characterized by the transformation of an input into myriad outputs over several network layers

  17. Regulation and dysregulation of axon infrastructure by myelinating glia. (United States)

    Pan, Simon; Chan, Jonah R


    Axon loss and neurodegeneration constitute clinically debilitating sequelae in demyelinating diseases such as multiple sclerosis, but the underlying mechanisms of secondary degeneration are not well understood. Myelinating glia play a fundamental role in promoting the maturation of the axon cytoskeleton, regulating axon trafficking parameters, and imposing architectural rearrangements such as the nodes of Ranvier and their associated molecular domains. In the setting of demyelination, these changes may be reversed or persist as maladaptive features, leading to axon degeneration. In this review, we consider recent insights into axon-glial interactions during development and disease to propose that disruption of the cytoskeleton, nodal architecture, and other components of axon infrastructure is a potential mediator of pathophysiological damage after demyelination. © 2017 Pan and Chan.

  18. Active polysomes in the axoplasm of the squid giant axon. (United States)

    Giuditta, A; Menichini, E; Perrone Capano, C; Langella, M; Martin, R; Castigli, E; Kaplan, B B


    Axons and axon terminals are widely believed to lack the capacity to synthesize proteins, relying instead on the delivery of proteins made in the perikaryon. In agreement with this view, axoplasmic proteins synthesized by the isolated giant axon of the squid are believed to derive entirely from periaxonal glial cells. However, squid axoplasm is known to contain the requisite components of an extra-mitochondrial protein synthetic system, including protein factors, tRNAs, rRNAs, and a heterogeneous family of mRNAs. Hence, the giant axon could, in principle, maintain an endogenous protein synthetic capacity. Here, we report that the squid giant axon also contains active polysomes and mRNA, which hybridizes to a riboprobe encoding murine neurofilament protein. Taken together, these findings provide direct evidence that proteins (including the putative neuron-specific neurofilament protein) are also synthesized de novo in the axonal compartment.

  19. A variational model for propagation time, volumetric and synchronicity optimization in the spinal cord axon network, and a method for testing it (United States)

    Mota, Bruno


    Most information in the central nervous system in general and the (simpler) spinal cord in particular, is transmitted along bundles of parallel axons. Each axon's transmission time increases linearly with length and decreases as a power law of caliber. Therefore, evolution must find a distribution of axonal numbers, lengths and calibers that balances the various tradeoffs between gains in propagation time, signal throughput and synchronicity, against volumetric and metabolic costs. Here I apply a variational method to calculate the distribution of axonal caliber in the spinal cord as a function of axonal length, that minimizes the average axonal signal propagation time, subject to the constraints of white matter total volume and the variance of propagation times, and allowing for arbitrary fiber priorities and end-points. The Lagrange multipliers obtained thereof can be naturally interpreted as 'exchange rates', e.g., how much evolution is willing to pay, in white matter added volume, per unit time decrease of propagation time. This is, to my knowledge, the first model that quantifies explicitly these evolutionary tradeoffs, and can obtain them empirically by measuring the distribution of axonal calibers. We are in the process of doing so using the isotropic fractionator method. I thank FAPERJ for financial support.

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


    White, Robin; Krämer-Albers, Eva-Maria


    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 specialized glial cells which ensheath axons with a lipid-rich insulating membrane. Myelination is a multi-step process initiated by axon-glia recognition triggering glial polarization followed by targeted myelin membrane expansion and compaction. Thereby, a myelin sheath of complex subdomain structure is...

  1. Long-range projection neurons of the mouse ventral tegmental area: a single-cell axon tracing analysis. (United States)

    Aransay, Ana; Rodríguez-López, Claudia; García-Amado, María; Clascá, Francisco; Prensa, Lucía


    Pathways arising from the ventral tegmental area (VTA) release dopamine and other neurotransmitters during the expectation and achievement of reward, and are regarded as central links of the brain networks that create drive, pleasure, and addiction. While the global pattern of VTA projections is well-known, the actual axonal wiring of individual VTA neurons had never been investigated. Here, we labeled and analyzed the axons of 30 VTA single neurons by means of single-cell transfection with the Sindbis-pal-eGFP vector in mice. These observations were complemented with those obtained by labeling the axons of small populations of VTA cells with iontophoretic microdeposits of biotinylated dextran amine. In the single-cell labeling experiments, each entire axonal tree was reconstructed from serial sections, the length of terminal axonal arbors was estimated by stereology, and the dopaminergic phenotype was tested by double-labeling for tyrosine hydroxylase immunofluorescence. We observed two main, markedly different VTA cell morphologies: neurons with a single main axon targeting only forebrain structures (FPN cells), and neurons with multibranched axons targeting both the forebrain and the brainstem (F + BSPN cells). Dopaminergic phenotype was observed in FPN cells. Moreover, four "subtypes" could be distinguished among the FPN cells based on their projection targets: (1) "Mesocorticolimbic" FPN projecting to both neocortex and basal forebrain; (2) "Mesocortical" FPN innervating the neocortex almost exclusively; (3) "Mesolimbic" FPN projecting to the basal forebrain, accumbens and caudateputamen; and (4) "Mesostriatal" FPN targeting only the caudateputamen. While the F + BSPN cells were scattered within VTA, the mesolimbic neurons were abundant in the paranigral nucleus. The observed diversity in wiring architectures is consistent with the notion that different VTA cell subpopulations modulate the activity of specific sets of prosencephalic and brainstem structures.

  2. Quantification of dendritic and axonal growth after injury to the auditory system of the adult cricket Gryllus bimaculatus

    Directory of Open Access Journals (Sweden)

    Alexandra ePfister


    Full Text Available Dendrite and axon growth and branching during development are regulated by a complex set of intracellular and external signals. However, the cues that maintain or influence adult neuronal morphology are less well understood. Injury and deafferentation tend to have negative effects on adult nervous systems. An interesting example of injury-induced compensatory growth is seen in the cricket, Gryllus bimaculatus. After unilateral loss of an ear in the adult cricket, auditory neurons within the central nervous system sprout to compensate for the injury. Specifically, after being deafferented, ascending neurons (AN-1 and AN-2 send dendrites across the midline of the prothoracic ganglion where they receive input from auditory afferents that project through the contralateral auditory nerve (N5. Deafferentation also triggers contralateral N5 axonal growth. In this study, we quantified AN dendritic and N5 axonal growth at 30 hours, as well as at 3, 5, 7, 14 and 20 days after deafferentation in adult crickets. Significant differences in the rates of dendritic growth between males and females were noted. In females, dendritic growth rates were non-linear; a rapid burst of dendritic extension in the first few days was followed by a plateau reached at 3 days after deafferentation. In males, however, dendritic growth rates were linear, with dendrites growing steadily over time and reaching lengths, on average, twice as long as in females. On the other hand, rates of N5 axonal growth showed no significant sexual dimorphism and were linear. Within each animal, the growth rates of dendrites and axons were not correlated, indicating that independent factors likely influence dendritic and axonal growth in response to injury in this system. Our findings provide a basis for future study of the cellular features that allow differing dendrite and axon growth patterns as well as sexually dimorphic dendritic growth in response to deafferentation.

  3. Origin, course, and laterality of spinocerebellar axons in the North American opossum, Didelphis virginiana. (United States)

    Terman, J R; Wang, X M; Martin, G F


    Spinocerebellar axons have been studied extensively in placental mammals, but there have been no full reports on their origin, laterality, or spinal course in any marsupial. We have used the North American opossum (Didelphis virginiana) to obtain such information and to ask whether any spinocerebellar neurons innervate both the anterior and posterior lobes of the cerebellum through axonal collaterals. To identify spinal neurons that project to the cerebellum, we employed the retrograde transport of Fluoro-Gold (FG) from the anterior lobe, the main target of spinocerebellar axons. In some cases, cerebellar injections of FG were combined with hemisections of the rostral cervical or midthoracic spinal cord, so that laterality of spinocerebellar connections could be established. To determine whether single neurons project to both the anterior lobe and the posterior lobe, injections of Fast Blue (FB) into the anterior lobe were combined with injections of Diamidino yellow (DY) or rhodamine B dextran (RBD) into the posterior lobe, or vice versa. Following injections of FG into the anterior lobe, neurons were labeled throughout the length of the spinal cord, which differed in laminar distribution and laterality of their projections. Among other areas, neurons were labeled in the central cervical nucleus, the nucleus centrobasalis, Clarke's nucleus, the dorsal horn dorsal spinocerebellar tract area, the spinal border region, and Stilling's nucleus. When anterior lobe injections of FB were combined with injections of RBD or DY into the posterior lobe, or vice versa, some double-labeled neurons were present in all major spinocerebellar groups. Cerebellar injections of FG also retrogradely labeled spinocerebellar axons, allowing us to document their locations in the gray matter as well as within the periphery of the lateral and ventral funiculi at all spinal levels. A few spinocerebellar axons also were found in the dorsal funiculus (a dorsal column-spinocerebellar tract

  4. Schwann Cell Glycogen Selectively Supports Myelinated Axon Function (United States)

    Brown, Angus M; Evans, Richard D; Black, Joel; Ransom, Bruce R


    Objectives Interruption of energy supply to peripheral axons is a cause of axon loss. We determined if glycogen was present in mammalian peripheral nerve, and if it supported axon conduction during aglycemia. Methods We used biochemical assay and electron microscopy to determine the presence of glycogen, and electrophysiology to monitor axon function. Results Glycogen was present in sciatic nerve, its concentration varying directly with ambient [glucose]. Electron microscopy detected glycogen granules primarily in myelinating Schwann cell cytoplasm and these diminished after exposure to aglycemia. During aglycemia, conduction failure in large myelinated axons (A fibers) mirrored the time-course of glycogen loss. Latency to CAP failure was directly related to nerve glycogen content at aglycemia onset. Glycogen did not benefit the function of slow-conducting, small diameter unmyelinated axons (C fibers) during aglycemia. Blocking glycogen breakdown pharmacologically accelerated CAP failure during aglycemia in A fibers, but not in C fibers. Lactate was as effective as glucose in supporting sciatic nerve function, and was continuously released into the extracellular space in the presence of glucose and fell rapidly during aglycemia. Interpretation Our findings indicated that glycogen is present in peripheral nerve, primarily in myelinating Schwann cells, and exclusively supports large diameter, myelinated axon conduction during aglycemia. Available evidence suggests that peripheral nerve glycogen breaks down during aglycemia and is passed, probably as lactate, to myelinated axons to support function. Unmyelinated axons are not protected by glycogen and are more vulnerable to dysfunction during periods of hypoglycemia. PMID:23034913

  5. Axonal branching patterns of ventral pallidal neurons in the rat. (United States)

    Tripathi, Anushree; Prensa, Lucía; Mengual, Elisa


    The ventral pallidum (VP) is a key component of the cortico-basal ganglia circuits that process motivational and emotional information, and also a crucial site for reward. Although the main targets of the two VP compartments, medial (VPm) and lateral (VPl) have already been established, the collateralization patterns of individual axons have not previously been investigated. Here we have fully traced eighty-four axons from VPm, VPl and the rostral extension of VP into the olfactory tubercle (VPr), using the anterograde tracer biotinylated dextran amine in the rat. Thirty to fifty percent of axons originating from VPm and VPr collateralized in the mediodorsal thalamic nucleus and lateral habenula, indicating a close association between the ventral basal ganglia-thalamo-cortical loop and the reward network at the single axon level. Additional collateralization of these axons in diverse components of the extended amygdala and corticopetal system supports a multisystem integration that may take place at the basal forebrain. Remarkably, we did not find evidence for a sharp segregation in the targets of axons arising from the two VP compartments, as VPl axons frequently collateralized in the caudal lateral hypothalamus and ventral tegmental area, the well-known targets of VPm, while VPm axons, in turn, also collateralized in typical VPl targets such as the subthalamic nucleus, substantia nigra pars compacta and reticulata, and retrorubral field. Nevertheless, VPl and VPm displayed collateralization patterns that paralleled those of dorsal pallidal components, confirming at the single axon level the parallel organization of functionally different basal ganglia loops.

  6. Differences in excitability properties of FDI and ADM motor axons. (United States)

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


    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.

  7. The age factor in axonal repair after spinal cord injury: A focus on neuron-intrinsic mechanisms. (United States)

    Geoffroy, Cédric G; Meves, Jessica M; Zheng, Binhai


    Age is an important consideration for recovery and repair after spinal cord injury. Spinal cord injury is increasingly affecting the middle-aged and aging populations. Despite rapid progress in research to promote axonal regeneration and repair, our understanding of how age can modulate this repair is rather limited. In this review, we discuss the literature supporting the notion of an age-dependent decline in axonal growth after central nervous system (CNS) injury. While both neuron-intrinsic and extrinsic factors are involved in the control of axon growth after injury, here we focus on possible intrinsic mechanisms for this age-dependent decline. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

  8. Attractant and repellent cues cooperate in guiding a subset of olfactory sensory axons to a well-defined protoglomerular target. (United States)

    Taku, Alemji A; Marcaccio, Christina L; Ye, Wenda; Krause, Gregory J; Raper, Jonathan A


    Olfactory sensory axons target well-defined intermediate targets in the zebrafish olfactory bulb called protoglomeruli well before they form odorant receptor-specific glomeruli. A subset of olfactory sensory neurons are labeled by expression of the or111-7:IRES:GAL4 transgene whose axons terminate in the central zone (CZ) protoglomerulus. Previous work has shown that some of these axons misproject to the more dorsal and anterior dorsal zone (DZ) protoglomerulus in the absence of Netrin 1/Dcc signaling. In search of additional cues that guide these axons to the CZ, we found that Semaphorin 3D (Sema3D) is expressed in the anterior bulb and acts as a repellent that pushes them towards the CZ. Further analysis indicates that Sema3D signaling is mediated through Nrp1a, while Nrp2b also promotes CZ targeting but in a Sema3D-independent manner. nrp1a, nrp2b and dcc transcripts are detected in or111-7 transgene-expressing neurons early in development and both Nrp1a and Dcc act cell-autonomously in sensory neurons to promote accurate targeting to the CZ. dcc and nrp1a double mutants have significantly more DZ misprojections than either single mutant, suggesting that the two signaling systems act independently and in parallel to direct a specific subset of sensory axons to their initial protoglomerular target. © 2016. Published by The Company of Biologists Ltd.

  9. Draxin, an axon guidance protein, affects chick trunk neural crest migration. (United States)

    Su, Yuhong; Naser, Iftekhar B; Islam, Shahidul M; Zhang, Sanbing; Ahmed, Giasuddin; Chen, Sandy; Shinmyo, Yohei; Kawakami, Minoru; Yamamura, Ken-ichi; Tanaka, Hideaki


    The neural crest is a multipotent population of migratory cells that arises in the central nervous system and subsequently migrates along defined stereotypic pathways. In the present work, we analyzed the role of a repulsive axon guidance protein, draxin, in the migration of neural crest cells. Draxin is expressed in the roof plate of the chick trunk spinal cord and around the early migration pathway of neural crest cells. Draxin modulates chick neural crest cell migration in vitro by reducing the polarization of these cells. When exposed to draxin, the velocity of migrating neural crest cells was reduced, and the cells changed direction so frequently that the net migration distance was also reduced. Overexpression of draxin also caused some early migrating neural crest cells to change direction to the dorsolateral pathway in the chick trunk region, presumably due to draxin's inhibitory activity. These results demonstrate that draxin, an axon guidance protein, can also affect trunk neural crest migration in the chick embryo.

  10. Reactive near field electromagnetic axonal communication channels and their role in neurodegenerative diseases. (United States)

    Morgera, Salvatore Domenic


    Research focus is on the micron-scale subsystem of the human nervous system known as the axon, or nerve fibre. In studying what has been traditionally treated as an electrochemical subsystem, we find that the axon is both an electrochemical and electromagnetic link in an intricately designed network. This work offers a game changing look at phenomena which enable interaction among millions of fibres tightly packed in bundles and tracts in the human peripheral and central nervous systems, respectively. We maintain that these fibres do not act independently as generally believed, but form intricate spatial and temporal near-field networks. An understanding of these networks will lead to improved diagnostics and therapeutics for neurodegenerative diseases.

  11. Death Receptor 6 Promotes Wallerian Degeneration in Peripheral Axons. (United States)

    Gamage, Kanchana K; Cheng, Irene; Park, Rachel E; Karim, Mardeen S; Edamura, Kazusa; Hughes, Christopher; Spano, Anthony J; Erisir, Alev; Deppmann, Christopher D


    Axon degeneration during development is required to sculpt a functional nervous system and is also a hallmark of pathological insult, such as injury [1, 2]. Despite similar morphological characteristics, very little overlap in molecular mechanisms has been reported between pathological and developmental degeneration [3-5]. In the peripheral nervous system (PNS), developmental axon pruning relies on receptor-mediated extrinsic degeneration mechanisms to determine which axons are maintained or degenerated [5-7]. Receptors have not been implicated in Wallerian axon degeneration; instead, axon autonomous, intrinsic mechanisms are thought to be the primary driver for this type of axon disintegration [8-10]. Here we survey the role of neuronally expressed, paralogous tumor necrosis factor receptor super family (TNFRSF) members in Wallerian degeneration. We find that an orphan receptor, death receptor 6 (DR6), is required to drive axon degeneration after axotomy in sympathetic and sensory neurons cultured in microfluidic devices. We sought to validate these in vitro findings in vivo using a transected sciatic nerve model. Consistent with the in vitro findings, DR6 -/- animals displayed preserved axons up to 4 weeks after injury. In contrast to phenotypes observed in Wld s and Sarm1 -/- mice, preserved axons in DR6 -/- animals display profound myelin remodeling. This indicates that deterioration of axons and myelin after axotomy are mechanistically distinct processes. Finally, we find that JNK signaling after injury requires DR6, suggesting a link between this novel extrinsic pathway and the axon autonomous, intrinsic pathways that have become established for Wallerian degeneration. Copyright © 2017 Elsevier Ltd. All rights reserved.

  12. Age-related changes in axonal transport. (United States)

    Frolkis, V V; Tanin, S A; Gorban, Y N


    In rats the rate of axonal transport (AT) or radiolabeled material decreased in the ventral roots of the spinal cord and the vagal and hypoglossal nerves with aging. A maximum AT deceleration in old age was observed in the vagus. The uncoupling of oxidative phosphorylation, inhibition of glycolysis and hypoxia induced a greater AT deceleration in old rats as compared to adults. Small doses of sodium fluoride accelerated AT, and this correlated with a rise in cAMP levels in ventral roots. High doses of sodium fluoride decelerated AT more markedly in old rats. It was shown that anabolic hormones (sex steroids and thyroxine) accelerated AT in both adult and old rats, whereas insulin induced a rise in AT rate in only adults. The catabolic steroid, hydrocortisone decelerated AT. In old rats castration diminished AT, while thyroidectomy had no effect. It was also shown that hydrocortisone and testosterone were transported along axons, reached fibers of the skeletal muscles, and hyperpolarized the plasma membrane. In old age the latent period was extended. Following 73 to 74 days of irradiation, AT slowed down in all the nerves studied in both adult and old rats. Following irradiation hormonal effects on AT changed, for example, the stimulatory effect of estradiol became weak, especially in old rats. Changes in AT could be an important mechanism of disordering the growth of neurons and innervated cells in old age.

  13. Wallerian-like axonal degeneration in the optic nerve after excitotoxic retinal insult: an ultrastructural study

    Directory of Open Access Journals (Sweden)

    Saggu Sarabjit K


    Full Text Available Abstract Background Excitotoxicity is involved in the pathogenesis of a number neurodegenerative diseases, and axonopathy is an early feature in several of these disorders. In models of excitotoxicity-associated neurological disease, an excitotoxin delivered to the central nervous system (CNS, could trigger neuronal death not only in the somatodendritic region, but also in the axonal region, via oligodendrocyte N-methyl-D-aspartate (NMDA receptors. The retina and optic nerve, as approachable regions of the brain, provide a unique anatomical substrate to investigate the "downstream" effect of isolated excitotoxic perikaryal injury on central nervous system (CNS axons, potentially providing information about the pathogenesis of the axonopathy in clinical neurological disorders. Herein, we provide ultrastructural information about the retinal ganglion cell (RGC somata and their axons, both unmyelinated and myelinated, after NMDA-induced retinal injury. Male Sprague-Dawley rats were killed at 0 h, 24 h, 72 h and 7 days after injecting 20 nM NMDA into the vitreous chamber of the left eye (n = 8 in each group. Saline-injected right eyes served as controls. After perfusion fixation, dissection, resin-embedding and staining, ultrathin sections of eyes and proximal (intraorbital and distal (intracranial optic nerve segments were evaluated by transmission electron tomography (TEM. Results TEM demonstrated features of necrosis in RGCs: mitochondrial and endoplasmic reticulum swelling, disintegration of polyribosomes, rupture of membranous organelle and formation of myelin bodies. Ultrastructural damage in the optic nerve mimicked the changes of Wallerian degeneration; early nodal/paranodal disturbances were followed by the appearance of three major morphological variants: dark degeneration, watery degeneration and demyelination. Conclusion NMDA-induced excitotoxic retinal injury causes mainly necrotic RGC somal death with Wallerian-like degeneration of the

  14. Is action potential threshold lowest in the axon?

    NARCIS (Netherlands)

    Kole, Maarten H. P.; Stuart, Greg J.


    Action potential threshold is thought to be lowest in the axon, but when measured using conventional techniques, we found that action potential voltage threshold of rat cortical pyramidal neurons was higher in the axon than at other neuronal locations. In contrast, both current threshold and voltage

  15. Protein-synthesizing machinery in the axon compartment. (United States)

    Koenig, E; Giuditta, A


    Contrary to the prevailing view that the axon lacks the capacity to synthesize proteins, a substantial body of evidence points to the existence of a metabolically active endogenous translational machinery. The machinery appears to be largely localized in the cortical zone of the axon, where, in vertebrate axons, it is distributed longitudinally as intermittent, discrete domains, called periaxoplasmic plaques. Studies, based on translation assays and probes of RNA transcripts in axon models such as the squid giant axon and selected vertebrate axons, provide evidence of locally synthesized proteins, most of which appear to be constituents of the slow axoplasmic transport rate groups. Metabolic and molecular biological findings are consistent with the view that the synthesis of proteins undergoing local turnover in the axonal compartment of macroneurons depends on the activity of an endogenous translational machinery. The documented presence of a metabolically active machinery in presynaptic terminals of squid photoreceptor neurons is also described. Finally, potential sources of axoplasmic RNAs comprising the machinery, which may include the ensheathing cell of the axon, as well as the cognate cell body, are also discussed.

  16. Wnts guide longitudinal axon tracts in the brain

    NARCIS (Netherlands)

    Prasad, A.A.


    The human brain contains more than 10 billion neurons that form over 10 trillion connections. The establishment of these connections during development requires axons to extend through the extracellular environment to their synaptic targets. This process of axon guidance is mediated by molecular

  17. 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.

  18. Motor Axonal Regeneration After Partial and Complete Spinal Cord Transection (United States)

    Lu, Paul; Blesch, Armin; Graham, Lori; Wang, Yaozhi; Samara, Ramsey; Banos, Karla; Haringer, Verena; Havton, Leif; Weishaupt, Nina; Bennett, David; Fouad, Karim; Tuszynski, Mark H.


    We subjected rats to either partial mid-cervical or complete upper thoracic spinal cord transections and examined whether combinatorial treatments support motor axonal regeneration into and beyond the lesion. Subjects received cAMP injections into brainstem reticular motor neurons to stimulate their endogenous growth state, bone marrow stromal cell grafts in lesion sites to provide permissive matrices for axonal growth, and brain-derived neurotrophic factor (BDNF) gradients beyond the lesion to stimulate distal growth of motor axons. Findings were compared to several control groups. Combinatorial treatment generated motor axon regeneration beyond both C5 hemisection and complete transection sites. Yet despite formation of synapses with neurons below the lesion, motor outcomes worsened after partial cervical lesions and spasticity worsened after complete transection. These findings highlight the complexity of spinal cord repair, and the need for additional control and shaping of axonal regeneration. PMID:22699902

  19. Plasticity of the Axon Initial Segment

    DEFF Research Database (Denmark)

    Petersen, Anders Victor; Cotel, Florence; Perrier, Jean François


    undergo important modifications during development. The development of the AIS is governed by intrinsic mechanisms. In addition, surrounding neuronal networks modify its maturation. As a result, neurons get tuned to particular physiological functions. Neuronal activity also influences the morphology......The axon initial segment (AIS) is a key neuronal compartment because it is responsible for action potential initiation. The local density of Na+ channels, the biophysical properties of K+ channels, as well as the length and diameter of the AIS determine the spiking of neurons. These parameters...... of the mature AIS. When excitatory neurons are hyperactive, their AIS undergo structural changes that decrease their excitability and thereby maintain the activity within a given range. These slow homeostatic regulatory mechanisms occur on a time scale of hours or days. In contrast, the activation...

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

    Czech Academy of Sciences Publication Activity Database

    Balaštík, Martin; Zhou, X.Z.; Alberich-Jorda, Meritxell; Weissová, Romana; Žiak, Jakub; Pazyra-Murphy, M.F.; Cosker, K.E.; Machoňová, Olga; Kozmiková, Iryna; Chen, CH.; Pastorino, L.; Asara, J.M.; Cole, A.; Sutherland, C.; Segal, R. A.; Lu, K.P.


    Roč. 13, č. 4 (2015), s. 812-828 ISSN 2211-1247 R&D Projects: GA MŠk(CZ) LK11213; GA MŠk LK21307; GA ČR GA15-03796S; GA MŠk LO1419 Institutional support: RVO:68378050 Keywords : Pin1 * axon guidance * Semaphorin 3A Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 7.870, year: 2015

  1. Axon tension regulates fasciculation/defasciculation through the control of axon shaft zippering

    Czech Academy of Sciences Publication Activity Database

    Šmít, Daniel; Fouquet, C.; Pincet, F.; Zápotocký, Martin; Trembleau, A.


    Roč. 6, Apr 19 (2017), č. článku e19907. ISSN 2050-084X R&D Projects: GA ČR(CZ) GA14-16755S; GA MŠk(CZ) 7AMB12FR002 Institutional support: RVO:67985823 Keywords : biophysics * cell adhesion * coarsening * developmental biology * mathematical model * mechanical tension * axon guidance Subject RIV: BO - Biophysics OBOR OECD: Biophysics Impact factor: 7.725, year: 2016

  2. Neuron Morphology Influences Axon Initial Segment Plasticity. (United States)

    Gulledge, Allan T; Bravo, Jaime J


    In most vertebrate neurons, action potentials are initiated in the axon initial segment (AIS), a specialized region of the axon containing a high density of voltage-gated sodium and potassium channels. It has recently been proposed that neurons use plasticity of AIS length and/or location to regulate their intrinsic excitability. Here we quantify the impact of neuron morphology on AIS plasticity using computational models of simplified and realistic somatodendritic morphologies. In small neurons (e.g., dentate granule neurons), excitability was highest when the AIS was of intermediate length and located adjacent to the soma. Conversely, neurons having larger dendritic trees (e.g., pyramidal neurons) were most excitable when the AIS was longer and/or located away from the soma. For any given somatodendritic morphology, increasing dendritic membrane capacitance and/or conductance favored a longer and more distally located AIS. Overall, changes to AIS length, with corresponding changes in total sodium conductance, were far more effective in regulating neuron excitability than were changes in AIS location, while dendritic capacitance had a larger impact on AIS performance than did dendritic conductance. The somatodendritic influence on AIS performance reflects modest soma-to-AIS voltage attenuation combined with neuron size-dependent changes in AIS input resistance, effective membrane time constant, and isolation from somatodendritic capacitance. We conclude that the impact of AIS plasticity on neuron excitability will depend largely on somatodendritic morphology, and that, in some neurons, a shorter or more distally located AIS may promote, rather than limit, action potential generation.

  3. IL4I1 augments CNS remyelination and axonal protection by modulating T cell driven inflammation. (United States)

    Psachoulia, Konstantina; Chamberlain, Kelly A; Heo, Dongeun; Davis, Stephanie E; Paskus, Jeremiah D; Nanescu, Sonia E; Dupree, Jeffrey L; Wynn, Thomas A; Huang, Jeffrey K


    SEE PLUCHINO AND PERUZZOTTI-JAMETTI DOI101093/AWW266 FOR A SCIENTIFIC COMMENTARY ON THIS ARTICLE: Myelin regeneration (remyelination) is a spontaneous process that occurs following central nervous system demyelination. However, for reasons that remain poorly understood, remyelination fails in the progressive phase of multiple sclerosis. Emerging evidence indicates that alternatively activated macrophages in central nervous system lesions are required for oligodendrocyte progenitor differentiation into remyelinating oligodendrocytes. Here, we show that an alternatively activated macrophage secreted enzyme, interleukin-four induced one (IL4I1), is upregulated at the onset of inflammation resolution and remyelination in mouse central nervous system lesions after lysolecithin-induced focal demyelination. Focal demyelination in mice lacking IL4I1 or interleukin 4 receptor alpha (IL4Rα) results in increased proinflammatory macrophage density, remyelination impairment, and axonal injury in central nervous system lesions. Conversely, recombinant IL4I1 administration into central nervous system lesions reduces proinflammatory macrophage density, enhances remyelination, and rescues remyelination impairment in IL4Rα deficient mice. We find that IL4I1 does not directly affect oligodendrocyte differentiation, but modulates inflammation by reducing interferon gamma and IL17 expression in lesioned central nervous system tissues, and in activated T cells from splenocyte cultures. Remarkably, intravenous injection of IL4I1 into mice with experimental autoimmune encephalomyelitis at disease onset significantly reversed disease severity, resulting in recovery from hindlimb paralysis. Analysis of post-mortem tissues reveals reduced axonal dystrophy in spinal cord, and decreased CD4 + T cell populations in spinal cord and spleen tissues. These results indicate that IL4I1 modulates inflammation by regulating T cell expansion, thereby permitting the formation of a favourable

  4. PTEN knockdown with the Y444F mutant AAV2 vector promotes axonal regeneration in the adult optic nerve

    Directory of Open Access Journals (Sweden)

    Zheng-ru Huang


    Full Text Available The lack of axonal regeneration is the major cause of vision loss after optic nerve injury in adult mammals. Activating the PI3K/AKT/mTOR signaling pathway has been shown to enhance the intrinsic growth capacity of neurons and to facilitate axonal regeneration in the central nervous system after injury. The deletion of the mTOR negative regulator phosphatase and tensin homolog (PTEN enhances regeneration of adult corticospinal neurons and ganglion cells. In the present study, we used a tyrosine-mutated (Y444F AAV2 vector to efficiently express a short hairpin RNA (shRNA for silencing PTEN expression in retinal ganglion cells. We evaluated cell survival and axonal regeneration in a rat model of optic nerve axotomy. The rats received an intravitreal injection of wildtype AAV2 or Y444F mutant AAV2 (both carrying shRNA to PTEN 4 weeks before optic nerve axotomy. Compared with the wildtype AAV2 vector, the Y444F mutant AAV2 vector enhanced retinal ganglia cell survival and stimulated axonal regeneration to a greater extent 6 weeks after axotomy. Moreover, post-axotomy injection of the Y444F AAV2 vector expressing the shRNA to PTEN rescued ~19% of retinal ganglion cells and induced axons to regenerate near to the optic chiasm. Taken together, our results demonstrate that PTEN knockdown with the Y444F AAV2 vector promotes retinal ganglion cell survival and stimulates long-distance axonal regeneration after optic nerve axotomy. Therefore, the Y444F AAV2 vector might be a promising gene therapy tool for treating optic nerve injury.

  5. Enlarging the nosological spectrum of hereditary diffuse leukoencephalopathy with axonal spheroids (HDLS). (United States)

    Hoffmann, Sarah; Murrell, Jill; Harms, Lutz; Miller, Kelly; Meisel, Andreas; Brosch, Thomas; Scheel, Michael; Ghetti, Bernardino; Goebel, Hans-Hilmar; Stenzel, Werner


    Hereditary diffuse leukoencephalopathy with axonal spheroids (HDLS) is an autosomal dominant disease clinically characterized by cognitive decline, personality changes, motor impairment, parkinsonism and seizures. Recently, mutations in the colony-stimulating factor-1 receptor (CSF1R) gene have been shown to be associated with HDLS. We report clinical, neuropathological and molecular genetic findings of patients from a new family with a mutation in the CSF1R gene. Disease onset was earlier and disease progression was more rapid compared with previously reported patients. Psychiatric symptoms including personality changes, alcohol abuse and severe depression were the first symptoms in male patients. In the index, female patient, the initial symptom was cognitive decline. Magnetic resonance imaging (MRI) showed bilateral, confluent white matter lesions in the cerebrum. Stereotactic biopsy revealed loss of myelin and microglial activation as well as macrophage infiltration of the parenchyma. Numerous axonal swellings and spheroids were present. Ultrastructural analysis revealed pigment-containing macrophages. Axonal swellings were detected by electron microscopy not only in the central nervous system (CNS) but also in skin nerves. We identified a heterozygous mutation (c.2330G>A, p.R777Q) in the CSF1R gene. Through this report, we aim to enlarge the nosological spectrum of HDLS, providing new clinical descriptions as well as novel neuropathological findings from the peripheral nervous system. © 2014 International Society of Neuropathology.

  6. Small-Molecule Stabilization of 14-3-3 Protein-Protein Interactions Stimulates Axon Regeneration. (United States)

    Kaplan, Andrew; Morquette, Barbara; Kroner, Antje; Leong, SooYuen; Madwar, Carolin; Sanz, Ricardo; Banerjee, Sara L; Antel, Jack; Bisson, Nicolas; David, Samuel; Fournier, Alyson E


    Damaged central nervous system (CNS) neurons have a poor ability to spontaneously regenerate, causing persistent functional deficits after injury. Therapies that stimulate axon growth are needed to repair CNS damage. 14-3-3 adaptors are hub proteins that are attractive targets to manipulate cell signaling. We identify a positive role for 14-3-3s in axon growth and uncover a developmental regulation of the phosphorylation and function of 14-3-3s. We show that fusicoccin-A (FC-A), a small-molecule stabilizer of 14-3-3 protein-protein interactions, stimulates axon growth in vitro and regeneration in vivo. We show that FC-A stabilizes a complex between 14-3-3 and the stress response regulator GCN1, inducing GCN1 turnover and neurite outgrowth. These findings show that 14-3-3 adaptor protein complexes are druggable targets and identify a new class of small molecules that may be further optimized for the repair of CNS damage. Copyright © 2017 Elsevier Inc. All rights reserved.

  7. Rational polypharmacology: systematically identifying and engaging multiple drug targets to promote axon growth (United States)

    Al-Ali, Hassan; Lee, Do-Hun; Danzi, Matt C.; Nassif, Houssam; Gautam, Prson; Wennerberg, Krister; Zuercher, Bill; Drewry, David H.; Lee, Jae K.; Lemmon, Vance P.; Bixby, John L.


    Mammalian Central Nervous System (CNS) neurons regrow their axons poorly following injury, resulting in irreversible functional losses. Identifying therapeutics that encourage CNS axon repair has been difficult, in part because multiple etiologies underlie this regenerative failure. This suggests a particular need for drugs that engage multiple molecular targets. Although multi-target drugs are generally more effective than highly selective alternatives, we lack systematic methods for discovering such drugs. Target-based screening is an efficient technique for identifying potent modulators of individual targets. In contrast, phenotypic screening can identify drugs with multiple targets; however, these targets remain unknown. To address this gap, we combined the two drug discovery approaches using machine learning and information theory. We screened compounds in a phenotypic assay with primary CNS neurons and also in a panel of kinase enzyme assays. We used learning algorithms to relate the compounds’ kinase inhibition profiles to their influence on neurite outgrowth. This allowed us to identify kinases that may serve as targets for promoting neurite outgrowth, as well as others whose targeting should be avoided. We found that compounds that inhibit multiple targets (polypharmacology) promote robust neurite outgrowth in vitro. One compound with exemplary polypharmacology, was found to promote axon growth in a rodent spinal cord injury model. A more general applicability of our approach is suggested by its ability to deconvolve known targets for a breast cancer cell line, as well as targets recently shown to mediate drug resistance. PMID:26056718

  8. Extracellular Tau Oligomers Induce Invasion of Endogenous Tau into the Somatodendritic Compartment and Axonal Transport Dysfunction (United States)

    Swanson, Eric; Breckenridge, Leigham; McMahon, Lloyd; Som, Sreemoyee; McConnell, Ian; Bloom, George S.


    Aggregates composed of the microtubule associated protein, tau, are a hallmark of Alzheimer’s disease and non-Alzheimer’s tauopathies. Extracellular tau can induce the accumulation and aggregation of intracellular tau, and tau pathology can be transmitted along neural networks over time. There are six splice variants of central nervous system tau, and various oligomeric and fibrillar forms are associated with neurodegeneration in vivo. The particular extracellular forms of tau capable of transferring tau pathology from neuron to neuron remain ill defined, however, as do the consequences of intracellular tau aggregation on neuronal physiology. The present study was undertaken to compare the effects of extracellular tau monomers, oligomers, and filaments comprising various tau isoforms on the behavior of cultured neurons. We found that 2N4R or 2N3R tau oligomers provoked aggregation of endogenous intracellular tau much more effectively than monomers or fibrils, or of oligomers made from other tau isoforms, and that a mixture of all six isoforms most potently provoked intracellular tau accumulation. These effects were associated with invasion of tau into the somatodendritic compartment. Finally, we observed that 2N4R oligomers perturbed fast axonal transport of membranous organelles along microtubules. Intracellular tau accumulation was often accompanied by increases in the run length, run time and instantaneous velocity of membranous cargo. This work indicates that extracellular tau oligomers can disrupt normal neuronal homeostasis by triggering axonal tau accumulation and loss of the polarized distribution of tau, and by impairing fast axonal transport. PMID:28482642

  9. Axonal and presynaptic RNAs are locally transcribed in glial cells. (United States)

    Giuditta, Antonio; Chun, Jong Tai; Eyman, Maria; Cefaliello, Carolina; Bruno, Anna Paola; Crispino, Marianna


    In the last few years, the long-standing opinion that axonal and presynaptic proteins are exclusively derived from the neuron cell body has been substantially modified by the demonstration that active systems of protein synthesis are present in axons and nerve terminals. These observations have raised the issue of the cellular origin of the involved RNAs, which has been generally attributed to the neuron soma. However, data gathered in a number of model systems indicated that axonal RNAs are synthesized in the surrounding glial cells. More recent experiments on the perfused squid giant axon have definitively proved that axoplasmic RNAs are transcribed in periaxonal glia. Their delivery to the axon occurs by a modulatory mechanism based on the release of neurotransmitters from the stimulated axon and on their binding to glial receptors. In additional experiments on squid optic lobe synaptosomes, presynaptic RNA has been also shown to be synthesized locally, presumably in nearby glia. Together with a wealth of literature data, these observations indicate that axons and nerve terminals are endowed with a local system of gene expression that supports the maintenance and plasticity of these neuronal domains.

  10. Propagation of action potentials in inhomogeneous axon regions. (United States)

    Ramón, F; Joyner, R W; Moore, J W


    Described are studies of propagation of action potentials through inhomogenous axon regions through experiments performed on squid giant axons and by computer simulations. The initial speed of propagation of the action potential is dependent upon the stimulus waveform. For a rectangular pulse of current, the action potential travel initally at a high speed that declines over the distance, reaching a constant speed of propagation at about 1-5 resting length constants; this distance depends on the stimulus strength. additional experiments studied the effects of changing the axon diameter and of introducing a temperature step. It was found that the propagated action potential suffers profound modification in shape and velocity as it reaches the region of transition. In both cases, it was possible to obtain reflected action potentials. A region of increased effective diameter was produced experimentally in the squid giant axon by insertion of an axial wire as usually employed in voltage clamps. It was found that the action potential, at the axial wire tip region, undergoes shape changes similar to those obtained tn simulations of a region of increased diameter as in a junction with the axon and soma in motor neurons. It is conducluded that the gaint axon can be used to reproduce simple electrical behaviors in other structures.-Ramón, F., R. W. Joyner and J.W. Moore. Propagation of action potentials in inhomogeneous axon regions.

  11. Mitotic motors coregulate microtubule patterns in axons and dendrites. (United States)

    Lin, Shen; Liu, Mei; Mozgova, Olga I; Yu, Wenqian; Baas, Peter W


    Microtubules are nearly uniformly oriented in the axons of vertebrate neurons but are non-uniformly oriented in their dendrites. Studies to date suggest a scenario for establishing these microtubule patterns whereby microtubules are transported into the axon and nascent dendrites with plus-ends-leading, and then additional microtubules of the opposite orientation are transported into the developing dendrites. Here, we used contemporary tools to confirm that depletion of kinesin-6 (also called CHO1/MKLP1 or kif23) from rat sympathetic neurons causes a reduction in the appearance of minus-end-distal microtubules in developing dendrites, which in turn causes them to assume an axon-like morphology. Interestingly, we observed a similar phenomenon when we depleted kinesin-12 (also called kif15 or HKLP2). Both motors are best known for their participation in mitosis in other cell types, and both are enriched in the cell body and dendrites of neurons. Unlike kinesin-12, which is present throughout the neuron, kinesin-6 is barely detectable in the axon. Accordingly, depletion of kinesin-6, unlike depletion of kinesin-12, has no effect on axonal branching or navigation. Interestingly, depletion of either motor results in faster growing axons with greater numbers of mobile microtubules. Based on these observations, we posit a model whereby these two motors generate forces that attenuate the transport of microtubules with plus-ends-leading from the cell body into the axon. Some of these microtubules are not only prevented from moving into the axon but are driven with minus-ends-leading into developing dendrites. In this manner, these so-called "mitotic" motors coregulate the microtubule patterns of axons and dendrites.

  12. Calsyntenin-1 shelters APP from proteolytic processing during anterograde axonal transport

    Directory of Open Access Journals (Sweden)

    Martin Steuble


    Endocytosis of amyloid-β precursor protein (APP is thought to represent the major source of substrate for the production of the amyloidogenic Aβ peptide by the β-secretase BACE1. The irreversible nature of proteolytic cleavage implies the existence of an efficient replenishment route for APP from its sites of synthesis to the cell surface. We recently found that APP exits the trans-Golgi network in intimate association with calsyntenin-1, a transmembrane cargo-docking protein for Kinesin-1-mediated vesicular transport. Here we characterized the function of calsyntenin-1 in neuronal APP transport using selective immunoisolation of intracellular trafficking organelles, immunocytochemistry, live-imaging, and RNAi. We found that APP is co-transported with calsyntenin-1 along axons to early endosomes in the central region of growth cones in carriers that exclude the α-secretase ADAM10. Intriguingly, calsyntenin-1/APP organelles contained BACE1, suggesting premature cleavage of APP along its anterograde path. However, we found that APP contained in calsyntenin-1/APP organelles was stable. We further analyzed vesicular trafficking of APP in cultured hippocampal neurons, in which calsyntenin-1 was reduced by RNAi. We found a markedly increased co-localization of APP and ADAM10 in axons and growth cones, along with increased proteolytic processing of APP and Aβ secretion in these neurons. This suggested that the reduced capacity for calsyntenin-1-dependent APP transport resulted in mis-sorting of APP into additional axonal carriers and, therefore, the premature encounter of unprotected APP with its ectodomain proteases. In combination, our results characterize calsyntenin-1/APP organelles as carriers for sheltered anterograde axonal transport of APP.

  13. Leukemia inhibitory factor protects axons in experimental autoimmune encephalomyelitis via an oligodendrocyte-independent mechanism.

    Directory of Open Access Journals (Sweden)

    Melissa M Gresle

    Full Text Available Leukemia inhibitory factor (LIF and Ciliary Neurotrophic factor (CNTF are members of the interleukin-6 family of cytokines, defined by use of the gp130 molecule as an obligate receptor. In the murine experimental autoimmune encephalomyelitis (EAE model, antagonism of LIF and genetic deletion of CNTF worsen disease. The potential mechanism of action of these cytokines in EAE is complex, as gp130 is expressed by all neural cells, and could involve immuno-modulation, reduction of oligodendrocyte injury, neuronal protection, or a combination of these actions. In this study we aim to investigate whether the beneficial effects of CNTF/LIF signalling in EAE are associated with axonal protection; and whether this requires signalling through oligodendrocytes. We induced MOG₃₅₋₅₅ EAE in CNTF, LIF and double knockout mice. On a CNTF null background, LIF knockout was associated with increased EAE severity (EAE grade 2.1±0.14 vs 2.6±0.19; P<0.05. These mice also showed increased axonal damage relative to LIF heterozygous mice, as indicated by decreased optic nerve parallel diffusivity on MRI (1540±207 µm²-/s vs 1310±175 µm²-/s; P<0.05, and optic nerve (-12.5% and spinal cord (-16% axon densities; and increased serum neurofilament-H levels (2.5 fold increase. No differences in inflammatory cell numbers or peripheral auto-immune T-cell priming were evident. Oligodendrocyte-targeted gp130 knockout mice showed that disruption of CNTF/LIF signalling in these cells has no effect on acute EAE severity. These studies demonstrate that endogenous CNTF and LIF act centrally to protect axons from acute inflammatory destruction via an oligodendrocyte-independent mechanism.

  14. Axonal Membranes and Their Domains: Assembly and Function of the Axon Initial Segment and Node of Ranvier

    Directory of Open Access Journals (Sweden)

    Andrew D. Nelson


    Full Text Available Neurons are highly specialized cells of the nervous system that receive, process and transmit electrical signals critical for normal brain function. Here, we review the intricate organization of axonal membrane domains that facilitate rapid action potential conduction underlying communication between complex neuronal circuits. Two critical excitable domains of vertebrate axons are the axon initial segment (AIS and the nodes of Ranvier, which are characterized by the high concentrations of voltage-gated ion channels, cell adhesion molecules and specialized cytoskeletal networks. The AIS is located at the proximal region of the axon and serves as the site of action potential initiation, while nodes of Ranvier, gaps between adjacent myelin sheaths, allow rapid propagation of the action potential through saltatory conduction. The AIS and nodes of Ranvier are assembled by ankyrins, spectrins and their associated binding partners through the clustering of membrane proteins and connection to the underlying cytoskeleton network. Although the AIS and nodes of Ranvier share similar protein composition, their mechanisms of assembly are strikingly different. Here we will cover the mechanisms of formation and maintenance of these axonal excitable membrane domains, specifically highlighting the similarities and differences between them. We will also discuss recent advances in super resolution fluorescence imaging which have elucidated the arrangement of the submembranous axonal cytoskeleton revealing a surprising structural organization necessary to maintain axonal organization and function. Finally, human mutations in axonal domain components have been associated with a growing number of neurological disorders including severe cognitive dysfunction, epilepsy, autism, neurodegenerative diseases and psychiatric disorders. Overall, this review highlights the assembly, maintenance and function of axonal excitable domains, particularly the AIS and nodes of

  15. DiI-labeling of DRG neurons to study axonal branching in a whole mount preparation of mouse embryonic spinal cord. (United States)

    Schmidt, Hannes; Rathjen, Fritz G


    Here we present a technique to label the trajectories of small groups of DRG neurons into the embryonic spinal cord by diffusive staining using the lipophilic tracer 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate (DiI). The comparison of axonal pathways of wild-type with those of mouse lines in which genes are mutated allows testing for a functional role of candidate proteins in the control of axonal branching which is an essential mechanism in the wiring of the nervous system. Axonal branching enables an individual neuron to connect with multiple targets, thereby providing the physical basis for the parallel processing of information. Ramifications at intermediate target regions of axonal growth may be distinguished from terminal arborization. Furthermore, different modes of axonal branch formation may be classified depending on whether branching results from the activities of the growth cone (splitting or delayed branching) or from the budding of collaterals from the axon shaft in a process called interstitial branching (Fig. 1). The central projections of neurons from the DRG offer a useful experimental system to study both types of axonal branching: when their afferent axons reach the dorsal root entry zone (DREZ) of the spinal cord between embryonic days 10 to 13 (E10-E13) they display a stereotyped pattern of T- or Y-shaped bifurcation. The two resulting daughter axons then proceed in rostral or caudal directions, respectively, at the dorsolateral margin of the cord and only after a waiting period collaterals sprout from these stem axons to penetrate the gray matter (interstitial branching) and project to relay neurons in specific laminae of the spinal cord where they further arborize (terminal branching). DiI tracings have revealed growth cones at the dorsal root entry zone of the spinal cord that appeared to be in the process of splitting suggesting that bifurcation is caused by splitting of the growth cone itself (Fig. 2), however

  16. Exposure to an open-field arena increases c-Fos expression in a subpopulation of neurons in the dorsal raphe nucleus, including neurons projecting to the basolateral amygdaloid complex

    DEFF Research Database (Denmark)

    Hale, M.W.; Hay-Schmidt, A.; Mikkelsen, J.D.


    Serotonergic systems in the dorsal raphe nucleus are thought to play an important role in the regulation of anxiety states. To investigate responses of neurons in the dorsal raphe nucleus to a mild anxiety-related stimulus, we exposed rats to an open-field, under low-light or high-light conditions...... of neurons in the midbrain raphe complex that projects to forebrain circuits regulating anxiety states, we used cholera toxin B subunit (CTb) as a retrograde tracer to identify neurons projecting to the basolateral amygdaloid complex (BL) in combination with c-Fos immunostaining to identify cells...... that activated neurons were serotonergic, non-serotonergic, or both. These data are consistent with the hypothesis that exposure to anxiogenic stimuli activates a subset of neurons in the midbrain raphe complex projecting to amygdala anxiety circuits Udgivelsesdato: 2008/12/10...

  17. Axon diameter mapping in crossing fibers with diffusion MRI

    DEFF Research Database (Denmark)

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


    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......This paper proposes a technique for a previously unaddressed problem, namely, mapping axon diameter in crossing fiber regions, using diffusion MRI. Direct measurement of tissue microstructure of this kind using diffusion MRI offers a new class of biomarkers that give more specific information about...... 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...

  18. Fiber Optic Detection of Action Potentials in Axons

    National Research Council Canada - National Science Library

    Smela, Elisabeth


    In prior exploratory research, we had designed a fiber optic sensor utilizing a long period Bragg grating for the purpose of detecting action potentials in axons optically, through a change in index...

  19. The nigrostriatal pathway: axonal collateralization and compartmental specificity. (United States)

    Prensa, L; Giménez-Amaya, J M; Parent, A; Bernácer, J; Cebrián, C


    This paper reviews two of the major features of the nigrostriatal pathway, its axonal collateralization, and compartmental specificity, as revealed by single-axon labeling experiments in rodents and immunocytological analysis of human postmortem tissue. The dorsal and ventral tiers of the substantia nigra pars compacta harbor various types of neurons the axons of which branch not only within the striatum but also in other major components of the basal ganglia. Furthermore, some nigrostriatal axons send collaterals both to thalamus and to brainstem pedunculopontine tegmental nucleus. In humans, the compartmental specificity of the nigrostriatal pathway is revealed by the fact that the matrix compartment is densely innervated by dopaminergic fibers, whereas the striosomes display different densities of dopaminergic terminals depending on their location within the striatum. The nigral neurons most severely affected in Parkinson's disease are the ventral tier cells that project to the matrix and form deep clusters in the substantia nigra pars reticulata.

  20. Syndecan Promotes Axon Regeneration by Stabilizing Growth Cone Migration

    Directory of Open Access Journals (Sweden)

    Tyson J. Edwards


    Full Text Available Growth cones facilitate the repair of nervous system damage by providing the driving force for axon regeneration. Using single-neuron laser axotomy and in vivo time-lapse imaging, we show that syndecan, a heparan sulfate (HS proteoglycan, is required for growth cone function during axon regeneration in C. elegans. In the absence of syndecan, regenerating growth cones form but are unstable and collapse, decreasing the effective growth rate and impeding regrowth to target cells. We provide evidence that syndecan has two distinct functions during axon regeneration: (1 a canonical function in axon guidance that requires expression outside the nervous system and depends on HS chains and (2 an intrinsic function in growth cone stabilization that is mediated by the syndecan core protein, independently of HS. Thus, syndecan is a regulator of a critical choke point in nervous system repair.

  1. Will PEDF Therapy Reverse Chronic Demyelination and Prevent Axon Loss in a Murine Model of Progressive Multiple Sclerosis (United States)


    Multiple Sclerosis ? PRINCIPAL INVESTIGATOR: David Pleasure MD CONTRACTING ORGANIZATION: University of California Davis, CA 95618 REPORT DATE...Murine Model of Progressive Multiple Sclerosis ? 5b. GRANT NUMBER W81XWH-12-1-0566 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) David Pleasure MD 5d...enhance central nervous system (CNS) remyelination and preserve CNS axons in mouse models of multiple sclerosis models. After determining the dosage of

  2. Targeting of pseudorabies virus structural proteins to axons requires association of the viral Us9 protein with lipid rafts.

    Directory of Open Access Journals (Sweden)

    Mathew G Lyman


    Full Text Available The pseudorabies virus (PRV Us9 protein plays a central role in targeting viral capsids and glycoproteins to axons of dissociated sympathetic neurons. As a result, Us9 null mutants are defective in anterograde transmission of infection in vivo. However, it is unclear how Us9 promotes axonal sorting of so many viral proteins. It is known that the glycoproteins gB, gC, gD and gE are associated with lipid raft microdomains on the surface of infected swine kidney cells and monocytes, and are directed into the axon in a Us9-dependent manner. In this report, we determined that Us9 is associated with lipid rafts, and that this association is critical to Us9-mediated sorting of viral structural proteins. We used infected non-polarized and polarized PC12 cells, a rat pheochromocytoma cell line that acquires many of the characteristics of sympathetic neurons in the presence of nerve growth factor (NGF. In these cells, Us9 is highly enriched in detergent-resistant membranes (DRMs. Moreover, reducing the affinity of Us9 for lipid rafts inhibited anterograde transmission of infection from sympathetic neurons to epithelial cells in vitro. We conclude that association of Us9 with lipid rafts is key for efficient targeting of structural proteins to axons and, as a consequence, for directional spread of PRV from pre-synaptic to post-synaptic neurons and cells of the mammalian nervous system.

  3. Differential compartmentalization of mRNAs in squid giant axon. (United States)

    Chun, J T; Gioio, A E; Crispino, M; Giuditta, A; Kaplan, B B


    Previously, we reported that the squid giant axon contains a heterogeneous population of mRNAs that includes beta-actin, beta-tubulin, kinesin, neurofilament proteins, and enolase. To define the absolute levels and relative distribution of these mRNAs, we have used competitive reverse transcription-PCR to quantify the levels of five mRNAs present in the giant axon and giant fiber lobe (GFL), the location of the parental cell soma. In the GFL, the number of transcripts for these mRNAs varied over a fourfold range, with beta-tubulin being the most abundant mRNA species (1.25 x 10(9) molecules per GFL). Based on transcript number, the rank order of mRNA levels in the GFL was beta-tubulin > beta-actin > kinesin > enolase > microtubule-associated protein (MAP) H1. In contrast, kinesin mRNA was most abundant in the axon (4.1 x 10(7) molecules per axon) with individual mRNA levels varying 15-fold. The rank order of mRNA levels in the axon was kinesin > beta-tubulin > MAP H1 > beta-actin > enolase. The relative abundance of the mRNA species in the axon did not correlate with the size of the transcript, nor was it directly related to their corresponding levels in the GFL. Taken together, these findings confirm that significant amounts of mRNA are present in the giant axon and suggest that specific mRNAs are differentially transported into the axonal domain.

  4. Modality-Specific Axonal Regeneration: Towards selective regenerative neural interfaces

    Directory of Open Access Journals (Sweden)

    Parisa eLotfi


    Full Text Available Regenerative peripheral nerve interfaces have been proposed as viable alternatives for the natural control of robotic prosthetic devices. However, sensory and motor axons at the neural interface are of mixed submodality types, which difficult the specific recording from motor axons and the eliciting of precise sensory modalities through selective stimulation. Here we evaluated the possibility of using type-specific neurotrophins to preferentially entice the regeneration of defined axonal populations from transected peripheral nerves into separate compartments. Segregation of mixed sensory fibers from dorsal root ganglion neurons was evaluated in vitro by compartmentalized diffusion delivery of nerve growth factor (NGF and neurotrophin-3 (NT-3, to preferentially entice the growth of TrkA+ nociceptive and TrkC+ proprioceptive subsets of sensory neurons, respectively. The average axon length in the NGF channel increased 2.5 fold compared to that in saline or NT-3, whereas the number of branches increased 3 fold in the NT-3 channels. These results were confirmed using a 3-D Y-shaped in vitro assay showing that the arm containing NGF was able to entice a 5-fold increase in axonal length of unbranched fibers. To address if such segregation can be enticed in vivo, a Y-shaped tubing was used to allow regeneration of the transected adult rat sciatic nerve into separate compartments filled with either NFG or NT-3. A significant increase in the number of CGRP+ pain fibers were attracted towards the sural nerve, while N-52+ large diameter axons were observed in the tibial and NT-3 compartments. This study demonstrates the guided enrichment of sensory axons in specific regenerative chambers, and supports the notion that neurotrophic factors can be used to segregate sensory and perhaps motor axons in separate peripheral interfaces.

  5. Modality-specific axonal regeneration: toward selective regenerative neural interfaces. (United States)

    Lotfi, Parisa; Garde, Kshitija; Chouhan, Amit K; Bengali, Ebrahim; Romero-Ortega, Mario I


    Regenerative peripheral nerve interfaces have been proposed as viable alternatives for the natural control of robotic prosthetic devices. However, sensory and motor axons at the neural interface are of mixed sub-modality types, which difficult the specific recording from motor axons and the eliciting of precise sensory modalities through selective stimulation. Here we evaluated the possibility of using type specific neurotrophins to preferentially entice the regeneration of defined axonal populations from transected peripheral nerves into separate compartments. Segregation of mixed sensory fibers from dorsal root ganglion neurons was evaluated in vitro by compartmentalized diffusion delivery of nerve growth factor (NGF) and neurotrophin-3 (NT-3), to preferentially entice the growth of TrkA+ nociceptive and TrkC+ proprioceptive subsets of sensory neurons, respectively. The average axon length in the NGF channel increased 2.5-fold compared to that in saline or NT-3, whereas the number of branches increased threefold in the NT-3 channels. These results were confirmed using a 3D "Y"-shaped in vitro assay showing that the arm containing NGF was able to entice a fivefold increase in axonal length of unbranched fibers. To address if such segregation can be enticed in vivo, a "Y"-shaped tubing was used to allow regeneration of the transected adult rat sciatic nerve into separate compartments filled with either NFG or NT-3. A significant increase in the number of CGRP+ pain fibers were attracted toward the sural nerve, while N-52+ large-diameter axons were observed in the tibial and NT-3 compartments. This study demonstrates the guided enrichment of sensory axons in specific regenerative chambers, and supports the notion that neurotrophic factors can be used to segregate sensory and perhaps motor axons in separate peripheral interfaces.

  6. MR imaging of a diffuse axonal injury

    International Nuclear Information System (INIS)

    Inoue, Yukiya; Okamoto, Hisayo; Mitsushima, Minoru; Hori, Tomokatsu; Sasaki, Mamoru; Teraoka, Akira.


    Six patients who had been diagnosed as having so-called a 'Diffuse Axonal Injury (DAI)' were examined by means of Magnetic Resonance Imaging (Yokogawa Resona 0.5T and Shimadzu SMT 50A). MRI revealed clear evidence of injured white matter in these patients, while X-ray CT scanning could not demonstrate such lesions definitely. The patients consisted of three adults and three adolescents. They had been injured by traffic accidents or falls. Every patient had lost consciousness immediately, and their coma had continued for at least two weeks after the trauma. X-ray CT scanning demonstrated no complicated lesion, such as intracranial hematoma or brain edema, resulting in increased intracranial pressure and cerebral herniation. In all of the patients, injuries of the deep white matter (corpus callosum, upper pons, or internal capsule, for example) were clearly found by T 2 -weighted imaging. Because these lesions had characteristic features in their localation, as has been described by Adams et al. these patients were diagnosed as having DAI. Also, it was interesting that the focal neurological deficits of these patients correlated well with the local injuries of the white matter. The three young patients recovered to various degrees, but the three adults passed into a vegetative state. The prognosis of the patients seemed to be determined by their age. Because the clinical diagnosis of DAI is controversial, the use of MRI will help in its clinical diagnosis and analysis. (author)

  7. Kinematics of turnaround and retrograde axonal transport

    International Nuclear Information System (INIS)

    Snyder, R.E.


    Rapid axonal transport of a pulse of 35 S-methionine-labelled material was studied in vitro in the sensory neurons of amphibian sciatic nerve using a position-sensitive detector. For 10 nerves studied at 23.0 +/- 0.2 degrees C it was found that a pulse moved in the anterograde direction characterized by front edge, peak, and trailing edge transport rates of (mm/d) 180.8 +/- 2.2 (+/- SEM), 176.6 +/- 2.3, and 153.7 +/- 3.0, respectively. Following its arrival at a distal ligature, a smaller pulse was observed to move in the retrograde direction characterized by front edge and peak transport rates of 158.0 +/- 7.3 and 110.3 +/- 3.5, respectively, indicating that retrograde transport proceeds at a rate of 0.88 +/- 0.04 that of anterograde. The retrograde pulse was observed to disperse at a rate greater than the anterograde. Reversal of radiolabel at the distal ligature began 1.49 +/- 0.15 h following arrival of the first radiolabel. Considerable variation was seen between preparations in the way radiolabel accumulated in the end (ligature) regions of the nerve. Although a retrograde pulse was seen in all preparations, in 7 of 10 preparations there was no evidence of this pulse accumulating within less than 2-3 mm of a proximal ligature; however, accumulation was observed within less than 5 mm in all preparations

  8. MR imaging of a diffuse axonal injury

    Energy Technology Data Exchange (ETDEWEB)

    Inoue, Yukiya; Okamoto, Hisayo; Mitsushima, Minoru; Hori, Tomokatsu (Tottori Univ., Yonago (Japan). School of Medicine); Sasaki, Mamoru; Teraoka, Akira


    Six patients who had been diagnosed as having so-called a 'Diffuse Axonal Injury (DAI)' were examined by means of Magnetic Resonance Imaging (Yokogawa Resona 0.5T and Shimadzu SMT 50A). MRI revealed clear evidence of injured white matter in these patients, while X-ray CT scanning could not demonstrate such lesions definitely. The patients consisted of three adults and three adolescents. They had been injured by traffic accidents or falls. Every patient had lost consciousness immediately, and their coma had continued for at least two weeks after the trauma. X-ray CT scanning demonstrated no complicated lesion, such as intracranial hematoma or brain edema, resulting in increased intracranial pressure and cerebral herniation. In all of the patients, injuries of the deep white matter (corpus callosum, upper pons, or internal capsule, for example) were clearly found by T{sub 2}-weighted imaging. Because these lesions had characteristic features in their localation, as has been described by Adams et al. these patients were diagnosed as having DAI. Also, it was interesting that the focal neurological deficits of these patients correlated well with the local injuries of the white matter. The three young patients recovered to various degrees, but the three adults passed into a vegetative state. The prognosis of the patients seemed to be determined by their age. Because the clinical diagnosis of DAI is controversial, the use of MRI will help in its clinical diagnosis and analysis. (author).

  9. Developmental time windows for axon growth influence neuronal network topology. (United States)

    Lim, Sol; Kaiser, Marcus


    Early brain connectivity development consists of multiple stages: birth of neurons, their migration and the subsequent growth of axons and dendrites. Each stage occurs within a certain period of time depending on types of neurons and cortical layers. Forming synapses between neurons either by growing axons starting at similar times for all neurons (much-overlapped time windows) or at different time points (less-overlapped) may affect the topological and spatial properties of neuronal networks. Here, we explore the extreme cases of axon formation during early development, either starting at the same time for all neurons (parallel, i.e., maximally overlapped time windows) or occurring for each neuron separately one neuron after another (serial, i.e., no overlaps in time windows). For both cases, the number of potential and established synapses remained comparable. Topological and spatial properties, however, differed: Neurons that started axon growth early on in serial growth achieved higher out-degrees, higher local efficiency and longer axon lengths while neurons demonstrated more homogeneous connectivity patterns for parallel growth. Second, connection probability decreased more rapidly with distance between neurons for parallel growth than for serial growth. Third, bidirectional connections were more numerous for parallel growth. Finally, we tested our predictions with C. elegans data. Together, this indicates that time windows for axon growth influence the topological and spatial properties of neuronal networks opening up the possibility to a posteriori estimate developmental mechanisms based on network properties of a developed network.

  10. Parametric Probability Distribution Functions for Axon Diameters of Corpus Callosum

    Directory of Open Access Journals (Sweden)

    Farshid eSepehrband


    Full Text Available Axon diameter is an important neuroanatomical characteristic of the nervous system that alters in the course of neurological disorders such as multiple sclerosis. Axon diameters vary, even within a fiber bundle, and are not normally distributed. An accurate distribution function is therefore beneficial, either to describe axon diameters that are obtained from a direct measurement technique (e.g., microscopy, or to infer them indirectly (e.g., using diffusion-weighted MRI. The gamma distribution is a common choice for this purpose (particularly for the inferential approach because it resembles the distribution profile of measured axon diameters which has been consistently shown to be non-negative and right-skewed. In this study we compared a wide range of parametric probability distribution functions against empirical data obtained from electron microscopy images. We observed that the gamma distribution fails to accurately describe the main characteristics of the axon diameter distribution, such as location and scale of the mode and the profile of distribution tails. We also found that the generalized extreme value distribution consistently fitted the measured distribution better than other distribution functions. This suggests that there may be distinct subpopulations of axons in the corpus callosum, each with their own distribution profiles. In addition, we observed that several other distributions outperformed the gamma distribution, yet had the same number of unknown parameters; these were the inverse Gaussian, log normal, log logistic and Birnbaum-Saunders distributions.

  11. 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.


    to represent large-diameter axons that have failed to myelinate. Conditional neuregulin-1 ablation resulted in a reduced sensitivity to noxious mechanical stimuli. These findings emphasize the importance of neuregulin-1 in mediating the signaling between axons and both myelinating and nonmyelinating Schwann...... cells required for normal sensory function. Sensory neuronal survival and axonal maintenance, however, are not dependent on axon-derived neuregulin-1 signaling in adulthood Udgivelsesdato: 2009/6/17...

  12. Neural ECM molecules in axonal and synaptic homeostatic plasticity. (United States)

    Frischknecht, Renato; Chang, Kae-Jiun; Rasband, Matthew N; Seidenbecher, Constanze I


    Neural circuits can express different forms of plasticity. So far, Hebbian synaptic plasticity was considered the most important plastic phenomenon, but over the last decade, homeostatic mechanisms gained more interest because they can explain how a neuronal network maintains stable baseline function despite multiple plastic challenges, like developmental plasticity, learning, or lesion. Such destabilizing influences can be counterbalanced by the mechanisms of homeostatic plasticity, which restore the stability of neuronal circuits. Synaptic scaling is a mechanism in which neurons can detect changes in their own firing rates through a set of molecular sensors that then regulate receptor trafficking to scale the accumulation of glutamate receptors at synaptic sites. Additional homeostatic mechanisms allow local changes in synaptic activation to generate local synaptic adaptations and network-wide changes in activity, which lead to adjustments in the balance between excitation and inhibition. The molecular pathways underlying these forms of homeostatic plasticity are currently under intense investigation, and it becomes clear that the extracellular matrix (ECM) of the brain, which surrounds individual neurons and integrates them into the tissue, is an important element in these processes. As a highly dynamic structure, which can be remodeled and degraded in an activity-dependent manner and in concerted action of neurons and glial cells, it can on one hand promote structural and functional plasticity and on the other hand stabilize neural microcircuits. This chapter highlights the composition of brain ECM with particular emphasis on perisynaptic and axonal matrix formations and its involvement in plastic and adaptive processes of the central nervous system.

  13. Rho-independent stimulation of axon outgrowth and activation of the ERK and Akt signaling pathways by C3 transferase in sensory neurons

    Directory of Open Access Journals (Sweden)

    Maria eAuer


    Full Text Available Peripheral nerve injury triggers the activation of RhoA in spinal motor and peripheral sensory neurons. RhoA activates a number of effector proteins including the Rho-associated kinase, ROCK, which targets the cytoskeleton and leads to inhibition of neurite outgrowth. Blockade of the Rho/ROCK pathway by pharmacological means improves axon regeneration after experimental injury. C3bot transferase, an exoenzyme produced by Clostridium botulinum, inactivates RhoA by ADP-ribosylation. Up to now it was not investigated thoroughly whether C3bot exerts positive effects on peripheral axon regeneration as well. In the present study, recombinant membrane permeable C3bot produced a small, but significant, axon outgrowth effect on peripheral sensory neurons dissociated from adult dorsal root ganglia of the rat. Neuronal overexpression of C3, however, did not enhance axonal growth. Moreover, transfection of plasmids encoding dominant negative RhoA or RhoA specific shRNAs failed to increase axonal growth. Furthermore, we show that the C3bot mutant, C3E174Q, which lacks RhoA inhibitory activity, still stimulates axonal growth. When analyzing possible signaling mechanisms we found that ERK (extracellular signal-regulated kinase and Akt are activated by C3bot and ERK is induced by the C3E174Q mutant. Upregulation of kinase activities by C3bot occurs significantly faster than inactivation of RhoA indicating a RhoA-independent pathway of action by C3bot. The induction of ERK signaling by C3bot was detected in embryonic hippocampal neurons, too. Taken together, although RhoA plays a central role for inhibition of axon outgrowth by myelin-derived inhibitors, it does not interfere with axonal growth of sensory neurons on a permissive substrate in vitro. C3bot blocks neuronal RhoA activity, but its positive effects on axon elongation and branching appear to be mediated by Rho independent mechanisms involving activation of axon growth promoting ERK and Akt kinases.

  14. Modelling in vivo action potential propagation along a giant axon. (United States)

    George, Stuart; Foster, Jamie M; Richardson, Giles


    A partial differential equation model for the three-dimensional current flow in an excitable, unmyelinated axon is considered. Where the axon radius is significantly below a critical value R(crit) (that depends upon intra- and extra-cellular conductivity and ion channel conductance) the resistance of the intracellular space is significantly higher than that of the extracellular space, such that the potential outside the axon is uniformly small whilst the intracellular potential is approximated by the transmembrane potential. In turn, since the current flow is predominantly axial, it can be shown that the transmembrane potential is approximated by a solution to the one-dimensional cable equation. It is noted that the radius of the squid giant axon, investigated by (Hodgkin and Huxley 1952e), lies close to R(crit). This motivates us to apply the three-dimensional model to the squid giant axon and compare the results thus found to those obtained using the cable equation. In the context of the in vitro experiments conducted in (Hodgkin and Huxley 1952e) we find only a small difference between the wave profiles determined using these two different approaches and little difference between the speeds of action potential propagation predicted. This suggests that the cable equation approximation is accurate in this scenario. However when applied to the it in vivo setting, in which the conductivity of the surrounding tissue is considerably lower than that of the axoplasm, there are marked differences in both wave profile and speed of action potential propagation calculated using the two approaches. In particular, the cable equation significantly over predicts the increase in the velocity of propagation as axon radius increases. The consequences of these results are discussed in terms of the evolutionary costs associated with increasing the speed of action potential propagation by increasing axon radius.

  15. Molecular Disorganization of Axons Adjacent to Human Cortical Microinfarcts

    Directory of Open Access Journals (Sweden)

    Hamza Coban


    Full Text Available Cortical microinfarcts (CMIs are microscopically identified wedge-shaped ischemic lesions that occur at or near the cortical surface and result from occlusion of penetrating arterioles. These microscopic lesions can be observed with high-resolution magnetic resonance imaging in aging brains and in patients with cerebrovascular disease. Recent studies have suggested that strategically located microinfarcts strongly correlate with cognitive deficits, which can contribute to Alzheimer’s disease as well as other forms of dementia. We have recently shown that the molecular organization of axons into functional microdomains is altered in areas adjacent to white matter lacunar and microinfarcts, creating a peri-infarct penumbral injury in surviving axons. Whether similar changes in nodal, adjacent paranodal, and proximal axon initial segment molecular organization occur in the cortex adjacent to human CMIs is not known. Paraffin-embedded sections of autopsy brain tissue from five patients with CMIs were immunofluorescently labeled for nodal and paranodal markers including beta-IV spectrin, ankyrin-G, and contactin-associated protein. High magnification images from the peri-infarct cortical tissue were generated using confocal microscopy. In surviving cortical tissue adjacent to microinfarcts, we observed a dramatic loss of axon initial segments, suggesting that neuronal firing capacity in adjacent cortical tissue is likely compromised. The number of identifiable nodal/paranodal complexes in surviving cortical tissue is reduced adjacent to microinfarcts, while the average paranodal length is increased indicating a breakdown of axoglial contact. This axonal microdomain disorganization occurs in the relative absence of changes in the structural integrity of myelinated axons as measured by myelin basic protein and neurofilament staining. These findings indicate that the molecular organization of surviving axons adjacent to human CMIs is abnormal

  16. Myelinated sensory and alpha motor axon regeneration in peripheral nerve neuromas (United States)

    Macias, M. Y.; Lehman, C. T.; Sanger, J. R.; Riley, D. A.


    Histochemical staining for carbonic anhydrase and cholinesterase (CE) activities was used to analyze sensory and motor axon regeneration, respectively, during neuroma formation in transected and tube-encapsulated peripheral nerves. Median-ulnar and sciatic nerves in the rodent model permitted testing whether a 4 cm greater distance of the motor neuron soma from axotomy site or intrinsic differences between motor and sensory neurons influenced regeneration and neuroma formation 10, 30, and 90 days later. Ventral root radiculotomy confirmed that CE-stained axons were 97% alpha motor axons. Distance significantly delayed axon regeneration. When distance was negligible, sensory axons grew out sooner than motor axons, but motor axons regenerated to a greater quantity. These results indicate regeneration differences between axon subtypes and suggest more extensive branching of motor axons within the neuroma. Thus, both distance from injury site to soma and inherent motor and sensory differences should be considered in peripheral nerve repair strategies.

  17. Cortical Interneuron Subtypes Vary in Their Axonal Action Potential Properties. (United States)

    Casale, Amanda E; Foust, Amanda J; Bal, Thierry; McCormick, David A


    The role of interneurons in cortical microcircuits is strongly influenced by their passive and active electrical properties. Although different types of interneurons exhibit unique electrophysiological properties recorded at the soma, it is not yet clear whether these differences are also manifested in other neuronal compartments. To address this question, we have used voltage-sensitive dye to image the propagation of action potentials into the fine collaterals of axons and dendrites in two of the largest cortical interneuron subtypes in the mouse: fast-spiking interneurons, which are typically basket or chandelier neurons; and somatostatin containing interneurons, which are typically regular spiking Martinotti cells. We found that fast-spiking and somatostatin-expressing interneurons differed in their electrophysiological characteristics along their entire dendrosomatoaxonal extent. The action potentials generated in the somata and axons, including axon collaterals, of somatostatin-expressing interneurons are significantly broader than those generated in the same compartments of fast-spiking inhibitory interneurons. In addition, action potentials back-propagated into the dendrites of somatostatin-expressing interneurons much more readily than fast-spiking interneurons. Pharmacological investigations suggested that axonal action potential repolarization in both cell types depends critically upon Kv1 channels, whereas the axonal and somatic action potentials of somatostatin-expressing interneurons also depend on BK Ca(2+)-activated K(+) channels. These results indicate that the two broad classes of interneurons studied here have expressly different subcellular physiological properties, allowing them to perform unique computational roles in cortical circuit operations. Neurons in the cerebral cortex are of two major types: excitatory and inhibitory. The proper balance of excitation and inhibition in the brain is critical for its operation. Neurons contain three main

  18. GRS defective axonal distribution as a potential contributor to distal spinal muscular atrophy type V pathogenesis in a new model of GRS-associated neuropathy. (United States)

    Seo, Ah Jung; Park, Byung Sun; Jung, Junyang


    Distal spinal muscular atrophy type V (dSMA-V), a hereditary axonal neuropathy, is a glycyl-tRNA synthetase (GRS)-associated neuropathy caused by a mutation in GRS. In this study, using an adenovirus vector system equipped with a neuron-specific promoter, we constructed a new GRS-associated neuropathy mouse model. We found that wild-type GRS (WT) is distributed in peripheral axons, dorsal root ganglion (DRG) cell bodies, central axon terminals and motor neuron cell bodies in the mouse model. In contrast, the L129P mutant GRS was localized in DRG and motor neuron cell bodies. Thus, we propose that the disease-causing L129P mutant is linked to a distribution defect in peripheral nerves in vivo. Copyright © 2014 Elsevier B.V. All rights reserved.

  19. Mechanistic logic underlying the axonal transport of cytosolic proteins (United States)

    Scott, David A.; Das, Utpal; Tang, Yong; Roy, Subhojit


    Proteins vital to presynaptic function are synthesized in the neuronal perikarya and delivered into synapses via two modes of axonal transport. While membrane-anchoring proteins are conveyed in fast axonal transport via motor-driven vesicles, cytosolic proteins travel in slow axonal transport; via mechanisms that are poorly understood. We found that in cultured axons, populations of cytosolic proteins tagged to photoactivable-GFP (PA-GFP) move with a slow motor-dependent anterograde bias; distinct from vesicular-trafficking or diffusion of untagged PA-GFP. The overall bias is likely generated by an intricate particle-kinetics involving transient assembly and short-range vectorial spurts. In-vivo biochemical studies reveal that cytosolic proteins are organized into higher-order structures within axon-enriched fractions that are largely segregated from vesicles. Data-driven biophysical modeling best predicts a scenario where soluble molecules dynamically assemble into mobile supra-molecular structures. We propose a model where cytosolic proteins are transported by dynamically assembling into multi-protein complexes that are directly/indirectly conveyed by motors. PMID:21555071

  20. 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.

  1. Subtypes of GABAergic neurons project axons in the neocortex

    Directory of Open Access Journals (Sweden)

    Shigeyoshi Higo


    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.

  2. Axonal transport and axon sprouting in the adult rat dentate gyrus: an autoradiographic study

    International Nuclear Information System (INIS)

    Goldowitz, D.; Cotman, C.W.


    In response to an entorhinal lesion, the commissural and associational afferents to the dentate gyrus have been shown to expand beyond their normal terminal zone into the area denervated by the entorhinal lesion. The present study has investigated the axonal transport of [ 3 H]-labeled proteins in the commissural and associational projections following an entorhinal lesion. Injections of [ 3 H]proline, [ 3 H]leucine or [ 3 H)fucose were given in the vicinity of the commissural and associational cells of origin before, immediately subsequent to, or at 5 to 15 days after the entorhinal lesion. The disposition of previously- or newly-synthesized proteins was examined in the commissural and associational terminal field at different times after an entorhinal lesion by light-microscopic autoradiography. (author)

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

    DEFF Research Database (Denmark)

    Petersen, Anders V.; Johansen, Emil O.; Perrier, Jean-Francois


    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 recording 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...

  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


    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. Perilesional edema in radiation necrosis reflects axonal degeneration

    International Nuclear Information System (INIS)

    Perez-Torres, Carlos J; Yuan, Liya; Schmidt, Robert E; Rich, Keith M; Ackerman, Joseph JH; Garbow, Joel R


    Recently, we characterized a Gamma Knife® radiation necrosis mouse model with various magnetic resonance imaging (MRI) protocols to identify biomarkers useful in differentiation from tumors. Though the irradiation was focal to one hemisphere, a contralateral injury was observed that appeared to be localized in the white matter only. Interestingly, this injury was identifiable in T2-weighted images, apparent diffusion coefficient (ADC), and magnetization transfer ratio (MTR) maps, but not on post-contrast T1-weighted images. This observation of edema independent of vascular changes is akin to the perilesional edema seen in clinical radiation necrosis. The pathology underlying the observed white-matter MRI changes was explored by performing immunohistochemistry for healthy axons and myelin. The presence of both healthy axons and myelin was reduced in the contralateral white-matter lesion. Based on our immunohistochemical findings, the contralateral white-matter injury is most likely due to axonal degeneration

  6. The nano-architecture of the axonal cytoskeleton. (United States)

    Leterrier, Christophe; Dubey, Pankaj; Roy, Subhojit


    The corporeal beauty of the neuronal cytoskeleton has captured the imagination of generations of scientists. One of the easiest cellular structures to visualize by light microscopy, its existence has been known for well over 100 years, yet we have only recently begun to fully appreciate its intricacy and diversity. Recent studies combining new probes with super-resolution microscopy and live imaging have revealed surprising details about the axonal cytoskeleton and, in particular, have discovered previously unknown actin-based structures. Along with traditional electron microscopy, these newer techniques offer a nanoscale view of the axonal cytoskeleton, which is important for our understanding of neuronal form and function, and lay the foundation for future studies. In this Review, we summarize existing concepts in the field and highlight contemporary discoveries that have fundamentally altered our perception of the axonal cytoskeleton.

  7. The axon-protective WLD(S) protein partially rescues mitochondrial respiration and glycolysis after axonal injury. (United States)

    Godzik, Katharina; Coleman, Michael P


    The axon-protective Wallerian degeneration slow (WLD(S)) protein can ameliorate the decline in axonal ATP levels after neurite transection. Here, we tested the hypothesis that this effect is associated with maintenance of mitochondrial respiration and/or glycolysis. We used isolated neurites of superior cervical ganglion (SCG) cultures in the Seahorse XF-24 Metabolic Flux Analyser to determine mitochondrial respiration and glycolysis under different conditions. We observed that both mitochondrial respiration and glycolysis declined significantly during the latent phase of Wallerian degeneration. WLD(S) partially reduced the decline both in glycolysis and in mitochondrial respiration. In addition, we found that depleting NAD levels in uncut cultures led to changes in mitochondrial respiration and glycolysis similar to those rescued by WLD(S) after cut, suggesting that the maintenance of NAD levels in Wld(S) neurites after axonal injury at least partially underlies the maintenance of ATP levels. However, by using another axon-protective mutation (Sarm1(-/-)), we could demonstrate that rescue of basal ECAR (and hence probably glycolysis) rather than basal OCR (mitochondrial respiration) may be part of the protective phenotype to delay Wallerian degeneration. These findings open new routes to study glycolysis and the connection between NAD and ATP levels in axon degeneration, which may help to eventually develop therapeutic strategies to treat neurodegenerative diseases.

  8. Nutritional tryptophan restriction impairs plasticity of retinotectal axons during the critical period. (United States)

    Penedo, Letícia Abel; Oliveira-Silva, Priscilla; Gonzalez, Ericka M C; Maciel, Rafaela; Jurgilas, Patricia B; Melibeu, Adriana da Cunha Faria; Campello-Costa, Paula; Serfaty, Claudio Alberto


    The use-dependent specification of neural circuits occurs during post-natal development with a conspicuous influence of environmental factors, such as malnutrition that interferes with the major steps of brain maturation. Serotonin (5-HT), derived exclusively from the essential aminoacid tryptophan, is involved in mechanisms of development and use-dependent plasticity of the central nervous system. We studied the effects of the nutritional restriction of tryptophan in the plasticity of uncrossed retinotectal axons following a retinal lesion to the contralateral retina during the critical period in pigmented rats. Litters were fed through their mothers with a low tryptophan content diet, based on corn and gelatin, a complemented diet with standard tryptophan requirements for rodents or standard laboratory diet. The results suggest a marked reduction in the plasticity of intact axons into denervated territories in the tryptophan restricted group in comparison to control groups. Tryptophan complementation between PND10-21 completely restored retinotectal plasticity. However, the re-introduction of tryptophan after the end of the critical period (between PND28-P41) did not restore the sprouting ability of uncrossed axons suggesting a time-dependent effect to the reversion of plasticity deficits. Tryptophan-restricted animals showed a reduced activity of matrix metalloproteinase-9 and altered expressions of phosphorylated forms of ERK1/2 and AKT. Our results demonstrate the influence of this essential aminoacid as a modulator of neural plasticity during the critical period through the reduction of serotonin content which alters plasticity-related signaling pathways and matrix degradation.

  9. Axoplasmic RNA species synthesized in the isolated squid giant axon. (United States)

    Rapallino, M V; Cupello, A; Giuditta, A


    Isolated squid stellate nerves and giant fiber lobes were incubated for 8 hr in Millipore filtered sea water containing [3H]uridine. The electrophoretic patterns of radioactive RNA purified from the axoplasm of the giant axon and from the giant fiber lobe (cell bodies of the giant axon) demonstrated the presence of RNA species with mobilities corresponding to tRNA and rRNA. The presence of labeled rRNAs was confirmed by the behavior of the large rRNA component (31S) which, in the squid, readily dissociates into its two constituent moyeties (17S and 20S). Comparable results were obtained with the axonal sheath and the stellate nerve. In all the electrophoretic patterns, additional species of radioactive RNA migrated between the 4S and the 20S markers, i.e. with mobilities corresponding to presumptive mRNAs. Chromatographic analysis of the purified RNAs on oligo(dT)cellulose indicated the presence of labeled poly(A)+ RNA in all tissue samples. Radioactive poly(A)+ RNA represented approximately 1% of the total labeled RNA in the axoplasm, axonal sheath and stellate nerve, but more than 2% in the giant fiber lobe. The labeled poly(A)+ RNAs of the giant fibre lobe showed a prevalence of larger species in comparison to the axonal sheath and stellate nerve. In conclusion, the axoplasmic RNAs synthesized by the isolated squid giant axon appear to include all the major classes of axoplasmic RNAs, that is rRNA, tRNA and mRNA.

  10. Uncovering sensory axonal dysfunction in asymptomatic type 2 diabetic neuropathy.

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    Jia-Ying Sung

    Full Text Available This study investigated sensory and motor nerve excitability properties to elucidate the development of diabetic neuropathy. A total of 109 type 2 diabetes patients were recruited, and 106 were analyzed. According to neuropathy severity, patients were categorized into G0, G1, and G2+3 groups using the total neuropathy score-reduced (TNSr. Patients in the G0 group were asymptomatic and had a TNSr score of 0. Sensory and motor nerve excitability data from diabetic patients were compared with data from 33 healthy controls. Clinical assessment, nerve conduction studies, and sensory and motor nerve excitability testing data were analyzed to determine axonal dysfunction in diabetic neuropathy. In the G0 group, sensory excitability testing revealed increased stimulus for the 50% sensory nerve action potential (P<0.05, shortened strength-duration time constant (P<0.01, increased superexcitability (P<0.01, decreased subexcitability (P<0.05, decreased accommodation to depolarizing current (P<0.01, and a trend of decreased accommodation to hyperpolarizing current in threshold electrotonus. All the changes progressed into G1 (TNSr 1-8 and G2+3 (TNSr 9-24 groups. In contrast, motor excitability only had significantly increased stimulus for the 50% compound motor nerve action potential (P<0.01 in the G0 group. This study revealed that the development of axonal dysfunction in sensory axons occurred prior to and in a different fashion from motor axons. Additionally, sensory nerve excitability tests can detect axonal dysfunction even in asymptomatic patients. These insights further our understanding of diabetic neuropathy and enable the early detection of sensory axonal abnormalities, which may provide a basis for neuroprotective therapeutic approaches.

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

    International Nuclear Information System (INIS)

    Menelaou, Evdokia; Paul, Latoya T.; Perera, Surangi N.; Svoboda, Kurt R.


    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.

  12. 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: [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)


    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.

  13. A novel and efficient gene transfer strategy reduces glial reactivity and improves neuronal survival and axonal growth in vitro.

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    Mathieu Desclaux

    Full Text Available BACKGROUND: The lack of axonal regeneration in the central nervous system is attributed among other factors to the formation of a glial scar. This cellular structure is mainly composed of reactive astrocytes that overexpress two intermediate filament proteins, the glial fibrillary acidic protein (GFAP and vimentin. Indeed, in vitro, astrocytes lacking GFAP or both GFAP and vimentin were shown to be the substrate for increased neuronal plasticity. Moreover, double knockout mice lacking both GFAP and vimentin presented lower levels of glial reactivity in vivo, significant axonal regrowth and improved functional recovery in comparison with wild-type mice after spinal cord hemisection. From these results, our objective was to develop a novel therapeutic strategy for axonal regeneration, based on the targeted suppression of astroglial reactivity and scarring by lentiviral-mediated RNA-interference (RNAi. METHODS AND FINDINGS: In this study, we constructed two lentiviral vectors, Lv-shGFAP and Lv-shVIM, which allow efficient and stable RNAi-mediated silencing of endogenous GFAP or vimentin in vitro. In cultured cortical and spinal reactive astrocytes, the use of these vectors resulted in a specific, stable and highly significant decrease in the corresponding protein levels. In a second model -- scratched primary cultured astrocytes -- Lv-shGFAP, alone or associated with Lv-shVIM, decreased astrocytic reactivity and glial scarring. Finally, in a heterotopic coculture model, cortical neurons displayed higher survival rates and increased neurite growth when cultured with astrocytes in which GFAP and vimentin had been invalidated by lentiviral-mediated RNAi. CONCLUSIONS: Lentiviral-mediated knockdown of GFAP and vimentin in astrocytes show that GFAP is a key target for modulating reactive gliosis and monitoring neuron/glia interactions. Thus, manipulation of reactive astrocytes with the Lv-shGFAP vector constitutes a promising therapeutic strategy for

  14. IFNgamma enhances microglial reactions to hippocampal axonal degeneration

    DEFF Research Database (Denmark)

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


    Glial reactivity is implicated in CNS repair and regenerative responses. Microglia, the cells responding earliest to axonal injury, produce tumor necrosis factor-alpha (TNFalpha), a cytokine with both cytopathic and neuroprotective effects. We have studied activation of hippocampal microglia...... 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...

  15. Selective rab11 transport and the intrinsic regenerative ability of CNS axons. (United States)

    Koseki, Hiroaki; Donegá, Matteo; Lam, Brian Yh; Petrova, Veselina; van Erp, Susan; Yeo, Giles Sh; Kwok, Jessica Cf; Ffrench-Constant, Charles; Eva, Richard; Fawcett, James W


    Neurons lose intrinsic axon regenerative ability with maturation, but the mechanism remains unclear. Using an in-vitro laser axotomy model, we show a progressive decline in the ability of cut CNS axons to form a new growth cone and then elongate. Failure of regeneration was associated with increased retraction after axotomy. Transportation into axons becomes selective with maturation; we hypothesized that selective exclusion of molecules needed for growth may contribute to regeneration decline. With neuronal maturity rab11 vesicles (which carry many molecules involved in axon growth) became selectively targeted to the somatodendritic compartment and excluded from axons by predominant retrograde transport However, on overexpression rab11 was mistrafficked into proximal axons, and these axons showed less retraction and enhanced regeneration after axotomy. These results suggest that the decline of intrinsic axon regenerative ability is associated with selective exclusion of key molecules, and that manipulation of transport can enhance regeneration.

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

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    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.

  17. Differential Release of β-Amyloid from Dendrite- Versus Axon-Targeted APP (United States)

    DeBoer, Scott R.; Dolios, Georgia; Wang, Rong


    The β-amyloid precursor protein (APP) plays a central role in the pathogenesis of Alzheimer's disease. APP is processed in neurons, but little is known about the relative contributions of presynaptic or postsynaptic compartments to the release of Aβ peptides. To address this issue, we transduced primary neurons from Sprague-Dawley rats or APP−/− mice (B6.129S7-Apptm1Dbo/J) with lentiviral constructs expressing APP chimeras harboring targeting motifs from low-density lipoprotein receptor or neuron-glia cell-adhesion molecule to polarize expression to either dendritic or axonal membranes, respectively. Using imaging and quantitative biochemical approaches, we now report that APP selectively targeted to either axons or dendrites leads to the secretion of full-length Aβ peptides with significantly elevated release from dendritic compartments. These findings reveal that the enzymatic machinery required for production of Aβ peptides are operative both in presynaptic and postsynaptic compartments of primary neurons, leading to the suggestion that Aβ-mediated impairments in glutamatergic neurotransmission is the result of Aβ release from both local and distal neuronal compartments. PMID:25209273

  18. Goldberg-Shprintzen megacolon syndrome with associated sensory motor axonal neuropathy. (United States)

    Dafsari, Hormos Salimi; Byrne, Susan; Lin, Jean-Pierre; Pitt, Matthew; Jongbloed, Jan Dh; Flinter, Frances; Jungbluth, Heinz


    Goldberg-Shprintzen megacolon syndrome (GOSHS) (OMIM 609460) is characterized by a combination of learning difficulties, characteristic dysmorphic features and Hirschsprung's disease. Variable clinical features include iris coloboma, congenital heart defects and central nervous system abnormalities, in particular polymicrogyria. GOSHS has been attributed to recessive mutations in KIAA1279, encoding kinesin family member (KIF)-binding protein (KBP) with a crucial role in neuronal microtubule dynamics. Here we report on a 7-year-old girl with GOSHS as a result of a homozygous deletion of exons 5 and 6 of the KIAA1279 gene. She had been referred with the suspicion of an underlying neuromuscular disorder before the genetic diagnosis was established, prompted by the findings of motor developmental delay, hypotonia, ptosis and absent reflexes. Neurophysiological studies revealed unequivocal evidence of a peripheral axonal sensory motor neuropathy. We hypothesize that an axonal sensory motor neuropathy may be part of the phenotypical spectrum of KIAA1279-related GOSHS, probably reflecting the effects of reduced KBP protein expression on peripheral neuronal function. © 2015 Wiley Periodicals, Inc.

  19. Quantifying mechanical force in axonal growth and guidance

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    Ahmad Ibrahim Mahmoud Athamneh


    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.

  20. Model of fasciculation and sorting in mixed populations of axons

    Czech Academy of Sciences Publication Activity Database

    Chaudhuri, D.; Borowski, P.; Zápotocký, Martin


    Roč. 84, č. 2 (2011), e021908 ISSN 1539-3755 R&D Projects: GA MŠk(CZ) LC554 Institutional research plan: CEZ:AV0Z50110509 Keywords : axon guidance * neurogenesis * mathematical model Subject RIV: FH - Neurology Impact factor: 2.255, year: 2011

  1. Axonal dynamics of excitatory and inhibitory neurons in somatosensory cortex.

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    Sally A Marik


    Full Text Available Cortical topography can be remapped as a consequence of sensory deprivation, suggesting that cortical circuits are continually modified by experience. To see the effect of altered sensory experience on specific components of cortical circuits, we imaged neurons, labeled with a genetically modified adeno-associated virus, in the intact mouse somatosensory cortex before and after whisker plucking. Following whisker plucking we observed massive and rapid reorganization of the axons of both excitatory and inhibitory neurons, accompanied by a transient increase in bouton density. For horizontally projecting axons of excitatory neurons there was a net increase in axonal projections from the non-deprived whisker barrel columns into the deprived barrel columns. The axon collaterals of inhibitory neurons located in the deprived whisker barrel columns retracted in the vicinity of their somata and sprouted long-range projections beyond their normal reach towards the non-deprived whisker barrel columns. These results suggest that alterations in the balance of excitation and inhibition in deprived and non-deprived barrel columns underlie the topographic remapping associated with sensory deprivation.

  2. Acute Motor Axonal Neuropathy in Association with Hepatitis E

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    Araz Al-Saffar


    Full Text Available Guillain–Barré syndrome (GBS is an acute peripheral neuropathy that develops as a result of post-infectious immune-mediated nerve injury. It can be classified into classic and variant GBS. Acute motor axonal neuropathy (AMAN is a subtype of GBS with the key clinical features of pure motor weakness, areflexia, absence of sensory symptoms, and lack of neurophysiologic evidence of demyelination. We reported a case of acute motor axonal neuropathy in association with hepatitis E infection. A young woman was referred to us after a period of nausea, fever, and diarrhea. She had unexplained muscle weakness at admission and has been diagnosed with acute hepatitis E infection. A rigorous clinical neurological assessment revealed bilateral symmetrical weakness, which affects the lower limbs more than the upper limbs, with no evidence of sensory involvement. Neurophysiological measurements indicated acute axonal injury without clues to demyelination. A diagnosis of acute motor axonal neuropathy subtype has been made, to which she only received supportive therapy. The symptoms resolved spontaneously and full recovery of motor function was attained after 35 days of weakness onset with complete normalization of neurophysiologic parameters.

  3. Investigation on the mechanism of peripheral axonal injury in glaucoma

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    Jun- Hong Zhao


    Full Text Available AIM: To compare the angles of longitudinal section of sclera around optic nerve heads and the never fiber layer changes in healthy adults and patients with glaucoma, and to investigate the mechanism of peripheral retinal axonal injury, with the combined knowledge of biomechanics. METHODS: The optical nerves and their peripheral tissue specimen in the 12 eyes from health adult donators and 12 eyes from glaucoma patient donators were dyed by Glees' method to compare the angles of longitudinal section of sclera around optic nerve heads(through optic nerve center, and to observe the anatomical features of the peripheral retinal axons. RESULTS: The mean angle of longitudinal section of sclera around optic nerve in healthy adults was 73.3°, while that in patients with absolute glaucoma was 75.6°. The difference showed no significance(t=1.44, P>0.05. There was a sharp bend in the course of peripheral optical fiber in healthy adults. However, the optic nerve fiber disappeared completely in patients with glaucoma end stage. CONCLUSION: The angle between the medial edge and leading edge of sclera(around optic nerve headsis an acute angle. The optical fiber in glaucoma end stage disappeared completely. The phenomenon may be related to high intraocular pressure, the sclera shape, the shear modulus of sclera and axons, and “axonal bending-injury” mechanism.

  4. IFNgamma enhances microglial reactions to hippocampal axonal degeneration

    DEFF Research Database (Denmark)

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


    Glial reactivity is implicated in CNS repair and regenerative responses. Microglia, the cells responding earliest to axonal injury, produce tumor necrosis factor-alpha (TNFalpha), a cytokine with both cytopathic and neuroprotective effects. We have studied activation of hippocampal microglia to p...

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

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    Shin Nagayama


    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.

  6. Conditioned fear inhibits c-fos mRNA expression in the central extended amygdala. (United States)

    Day, Heidi E W; Kryskow, Elisa M; Nyhuis, Tara J; Herlihy, Lauren; Campeau, Serge


    We have shown previously that unconditioned stressors inhibit neurons of the lateral/capsular division of the central nucleus of the amygdala (CEAl/c) and oval division of the bed nucleus of the stria terminalis (BSTov), which form part of the central extended amygdala. The current study investigated whether conditioned fear inhibits c-fos mRNA expression in these regions. Male rats were trained either to associate a visual stimulus (light) with footshock or were exposed to the light alone. After training, animals were replaced in the apparatus, and 2 h later injected remotely, via a catheter, with amphetamine (2 mg/kg i.p.), to induce c-fos mRNA and allow inhibition of expression to be measured. The rats were then presented with 15 visual stimuli over a 30 minute period. As expected, fear conditioned animals that were not injected with amphetamine, had extremely low levels of c-fos mRNA in the central extended amygdala. In contrast, animals that were trained with the light alone (no fear conditioning) and were injected with amphetamine had high levels of c-fos mRNA in the CEAl/c and BSTov. Animals that underwent fear conditioning, and were re-exposed to the conditioned stimulus after amphetamine injection had significantly reduced levels of c-fos mRNA in both the BSTov and CEAl/c, compared to the non-conditioned animals. These data suggest that conditioned fear can inhibit neurons of the central extended amygdala. Because these neurons are GABAergic, and project to the medial CEA (an amygdaloid output region), this may be a novel mechanism whereby conditioned fear potentiates amygdaloid output.

  7. Neurofilament protein synthesis in DRG neurons decreases more after peripheral axotomy than after central axotomy

    International Nuclear Information System (INIS)

    Greenberg, S.G.; Lasek, R.J.


    Cytoskeletal protein synthesis was studied in DRG neurons after transecting either their peripheral or their central branch axons. Specifically, the axons were transected 5-10 mm from the lumbar-5 ganglion on one side of the animal; the DRGs from the transected side and contralateral control side were labeled with radiolabeled amino acids in vitro; radiolabeled proteins were separated by 2-dimensional (2D) PAGE; and the amounts of radiolabel in certain proteins of the experimental and control ganglia were quantified and compared. We focused on the neurofilament proteins because they are neuron-specific. If either the peripheral or central axons were cut, the amounts of radiolabeled neurofilament protein synthesized by the DRG neurons decreased between 1 and 10 d after transection. Neurofilament protein labeling decreased more after transection of the peripheral axons than after transection of the central axons. In contrast to axonal transections, sham operations or heat shock did not decrease the radiolabeling of the neurofilament proteins, and these procedures also affected the labeling of actin, tubulin, and the heat-shock proteins differently from transection. These results and others indicate that axonal transection leads to specific changes in the synthesis of cytoskeletal proteins of DRG neurons, and that these changes differ from those produced by stress to the animal or ganglia. Studies of the changes in neurofilament protein synthesis from 1 to 40 d after axonal transection indicate that the amounts of radiolabeled neurofilament protein synthesis were decreased during axonal elongation, but that they returned toward control levels when the axons reached cells that stopped elongation

  8. Transplantation of Glial Cells Enhances Action Potential Conduction of Amyelinated Spinal Cord Axons in the Myelin-Deficient Rat (United States)

    Utzschneider, David A.; Archer, David R.; Kocsis, Jeffery D.; Waxman, Stephen G.; Duncan, Ian D.


    A central issue in transplantation research is to determine how and when transplantation of neural tissue can influence the development and function of the mammalian central nervous system. Of particular interest is whether electrophysiological function in the traumatized or diseased mammalian central nervous system can be improved by the replacement of cellular elements that are missing or damaged. Although it is known that transplantation of neural tissue can lead to functional improvement in models of neurological disease characterized by neuronal loss, less is known about results of transplantation in disorders of myelin. We report here that transplantation of glial cells into the dorsal columns of neonatal myelin-deficient rat spinal cords leads to myelination and a 3-fold increase in conduction velocity. We also show that impulses can propagate into and out of the transplant region and that axons myelinated by transplanted cells do not have impaired frequency-response properties. These results demonstrate that myelination following central nervous system glial cell transplantation enhances action potential conduction in myelin-deficient axons, with conduction velocity approaching normal values.

  9. NG2 cells response to axonal alteration in the spinal cord white matter in mice with genetic disruption of neurofilament light subunit expression

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    Xiao Zhi


    Full Text Available Abstract Background Chondroitin sulphate proteoglycan (NG2 expressing cells, morphologically characterized by multi-branched processes and small cell bodies, are the 4th commonest cell population of non-neuronal cell type in the central nervous system (CNS. They can interact with nodes of Ranvier, receive synaptic input, generate action potential and respond to some pathological stimuli, but the function of the cells is still unclear. We assumed the NG2 cells may play an active role in neuropathogenesis and aimed to determine if NG2 cells could sense and response to the alterations in the axonal contents caused by disruption of neurofilament light subunit (NFL expression. Results In the early neuropathological development stage, our study showed that the diameter of axons of upper motor neurons of NFL-/- mice decreased significantly while the thickness of their myelin sheath increased remarkably. Although there was an obvious morphological distortion in axons with occasionally partial demyelination, no obvious changes in expression of myelin proteins was detected. Parallel to these changes in the axons and their myelination, the processes of NG2 cells were disconnected from the nodes of Ranvier and extended further, suggesting that these cells in the spinal cord white matter could sense the alteration in axonal contents caused by disruption of NFL expression before astrocytic and microglial activation. Conclusion The structural configuration determined by the NFL gene may be important for maintenance of normal morphology of myelinated axons. The NG2 cells might serve as an early sensor for the delivery of information from impaired neurons to the local environment.

  10. Mecanismos involucrados en la promoción de crecimiento axonal por la glia envolvente del bulbo olfatorio

    Directory of Open Access Journals (Sweden)

    Vilma C. Muñetón-Gómez


    Full Text Available La actividad que promueve el crecimiento de axones por la glia envolvente (GE del bulbo olfatorio depende de la expresión de diversas moléculas durante el desarrollo, la vida adulta y la reparación de lesiones nerviosas. Diversas moléculas tales como las neurotrofinas y sus receptores, los factores de crecimiento, las moléculas de adhesión celular, las moléculas de matriz extracelular y las moléculas asociadas con la mielinización son producidas por la glia del sistema olfatorio durante el desarrollo. Su expresión sostenida durante la vida adulta parece estar asociada con el reemplazo celular y la alta plasticidad de este sistema. A su vez, su expresión se involucra en procesos de reparación de lesiones mediados por trasplantes de glia. La migración de la GE, que acompaña axones en crecimiento, se observa durante el desarrollo y en procesos de regeneración luego de una lesión. Los trasplantes de,GE permiten la navegación de brotes regenerantes a través del tejido gliótico inhibidor formado luego de una lesión del sistema nervioso central. El propósito de esta revisión es profundizar en los mecanismos de actividad promotora de crecimiento axonal.

  11. Axonal collateral-collateral transport of tract tracers in brain neurons: false anterograde labelling and useful tool. (United States)

    Chen, S; Aston-Jones, G


    It is well established that some neuroanatomical tracers may be taken up by local axonal terminals and transported to distant axonal collaterals (e.g., transganglionic transport in dorsal root ganglion cells). However, such collateral-collateral transport of tracers has not been systematically examined in the central nervous system. We addressed this issue with four neuronal tracers--biocytin, biotinylated dextran amine, cholera toxin B subunit, and Phaseolus vulgaris-leucoagglutinin--in the cerebellar cortex. Labelling of distant axonal collaterals in the cerebellar cortex (indication of collateral-collateral transport) was seen after focal iontophoretic microinjections of each of the four tracers. However, collateral-collateral transport properties differed among these tracers. Injection of biocytin or Phaseolus vulgaris-leucoagglutinin in the cerebellar cortex yielded distant collateral labelling only in parallel fibres. In contrast, injection of biotinylated dextran amine or cholera toxin B subunit produced distant collateral labelling of climbing fibres and mossy fibres, as well as parallel fibres. The present study is the first systematic examination of collateral-collateral transport following injection of anterograde tracers in brain. Such collateral-collateral transport may produce false-positive conclusions regarding neural connections when using these tracers for anterograde transport. However, this property may also be used as a tool to determine areas that are innervated by common distant afferents. In addition, these results may indicate a novel mode of chemical communication in the nervous system.

  12. In vivo modeling of neuronal function, axonal impairment and connectivity in neurodegenerative and neuropsychiatric disorders using induced pluripotent stem cells. (United States)

    Korecka, J A; Levy, S; Isacson, O


    Modeling neurological diseases using human embryonic or patient-derived induced pluripotent stem cells (iPSCs) improves the understanding of molecular and cellular changes underlying these diseases and can lead to new, potentially personalized therapies. Changes in expression of axon guidance cues and altered cytoskeletal maintenance have been implicated in neurodegenerative and neuropsychiatric disorders. To date, most of the iPSC patient-derived cellular dysfunction and phenotypic studies have been performed in vitro. To study the intrinsic axonal impairments and neuronal connectivity deficits in human disease iPSC-derived neurons we propose to graft these cells into the physiological three-dimensional multi-structural environment of the central nervous system of rodent models to obtain relevant in vivo data. Such human iPSC in vivo chimeric models can allow for neuronal maturation, capture neuropathological phenotypes of axonal and connectivity impairments, and serve as target engagement and drug validation studies using human cells, thus highly relevant for advancement of the drug development process in the late pre-clinical stages. Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.

  13. Optical Coherence Tomography-A New Diagnostic Tool to Evaluate Axonal Degeneration in Multiple Sclerosis: A Review

    Directory of Open Access Journals (Sweden)

    Nilüfer Kale


    Full Text Available Multiple sclerosis is an inflammatory demyelinating disorder of the central nervous system with a wide spectrum of clinical signs and symptoms. Multiple sclerosis lesions have a predilection for the optic nerves, periventricular white matter, brainstem, spinal cord, and cerebellum. The mechanisms responsible for multiple sclerosis are complex and heterogeneous across patients and disease stages. No specific markers exist for the definite diagnosis and prognosis of multiple sclerosis. The afferent visual pathway, which extends from the retina to the primary visual cortex including the optic nerve, is one of the most commonly affected sites in multiple sclerosis (94-99%. Pathology of affected optic nerves exhibits inflammation, demyelination, gliosis, axonal injury, and thinning of the retinal nerve fiber layer (RNFL. The RNFL is composed of unmyelinated axons, and measuring RNFL thickness is a viable method to monitor axonal loss reflecting disease progression. Optical coherence tomography is a noninvasive and reproducible tool in assessing the impact of multiple sclerosis on the thickness of the RNFL. Assessment of the afferent visual pathway using clinical, imaging and electrophysiological methods provides insights into the pathophysiology of multiple sclerosis and may also serve a prognostic role in multiple sclerosis

  14. Genetic Deletion of the Transcriptional Repressor NFIL3 Enhances Axon Growth In Vitro but Not Axonal Repair In Vivo

    NARCIS (Netherlands)

    van der Kallen, Loek R; Eggers, Ruben; Ehlert, Erich M; Verhaagen, J.; Smit, August B; van Kesteren, Ronald E


    Axonal regeneration after injury requires the coordinated expression of genes in injured neurons. We previously showed that either reducing expression or blocking function of the transcriptional repressor NFIL3 activates transcription of regeneration-associated genes Arg1 and Gap43 and strongly

  15. 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


    Following proximal axotomy, several types of neurons sprout de novo axons from distal dendrites. These processes may represent a means of forming new circuits following spinal cord injury. However, it is not know whether mammalian spinal interneurons, axotomized as a result of a spinal cord injur...

  16. Adult onset leukoencephalopathy with axonal spheroids and pigmented glia (ALSP) and Nasu-Hakola disease: lesion staging and dynamic changes of axons and microglial subsets. (United States)

    Oyanagi, Kiyomitsu; Kinoshita, Michiaki; Suzuki-Kouyama, Emi; Inoue, Teruhiko; Nakahara, Asa; Tokiwai, Mika; Arai, Nobutaka; Satoh, Jun-Ichi; Aoki, Naoya; Jinnai, Kenji; Yazawa, Ikuru; Arai, Kimihito; Ishihara, Kenji; Kawamura, Mitsuru; Ishizawa, Keisuke; Hasegawa, Kazuko; Yagisita, Saburo; Amano, Naoji; Yoshida, Kunihiro; Terada, Seishi; Yoshida, Mari; Akiyama, Haruhiko; Mitsuyama, Yoshio; Ikeda, Shu-Ichi


    The brains of 10 Japanese patients with adult onset leukoencephalopathy with axonal spheroids and pigmented glia (ALSP) encompassing hereditary diffuse leukoencephalopathy with axonal spheroids (HDLS) and pigmentary orthochromatic leukodystrophy (POLD) and eight Japanese patients with Nasu-Hakola disease (N-HD) and five age-matched Japanese controls were examined neuropathologically with special reference to lesion staging and dynamic changes of microglial subsets. In both diseases, the pathognomonic neuropathological features included spherically swollen axons (spheroids and globules), axon loss and changes of microglia in the white matter. In ALSP, four lesion stages based on the degree of axon loss were discernible: Stage I, patchy axon loss in the cerebral white matter without atrophy; Stage II, large patchy areas of axon loss with slight atrophy of the cerebral white matter and slight dilatation of the lateral ventricles; Stage III, extensive axon loss in the cerebral white matter and dilatation of the lateral and third ventricles without remarkable axon loss in the brainstem and cerebellum; Stage IV, devastated cerebral white matter with marked dilatation of the ventricles and axon loss in the brainstem and/or cerebellum. Internal capsule and pontine base were relatively well preserved in the N-HD, even at Stage IV, and the swollen axons were larger with a higher density in the ALSP. Microglial cells immunopositive for CD68, CD163 or CD204 were far more obvious in ALSP, than in N-HD, and the shape and density of the cells changed in each stage. With progression of the stage, clinical symptoms became worse to apathetic state, and epilepsy was frequently observed in patients at Stages III and IV in both diseases. From these findings, it is concluded that (i) shape, density and subsets of microglia change dynamically along the passage of stages and (ii) increase of IBA-1-, CD68-, CD163- and CD204-immunopositive cells precedes loss of axons in ALSP. © 2016

  17. Depolarization and electrical stimulation enhance in vitro and in vivo sensory axon growth after spinal cord injury. (United States)

    Goganau, Ioana; Sandner, Beatrice; Weidner, Norbert; Fouad, Karim; Blesch, Armin


    Activity dependent plasticity is a key mechanism for the central nervous system (CNS) to adapt to its environment. Whether neuronal activity also influences axonal regeneration in the injured CNS, and whether electrical stimulation (ES) can activate regenerative programs in the injured CNS remains incompletely understood. Using KCl-induced depolarization, in vivo ES followed by ex-vivo neurite growth assays and ES after spinal cord lesions and cell grafting, we aimed to identify parameters important for ES-enhanced neurite growth and axonal regeneration. Using cultures of sensory neurons, neurite growth was analyzed after KCl-induced depolarization for 1-72h. Increased neurite growth was detected after short-term stimulation and after longer stimulation if a sufficient delay between stimulation and growth measurements was provided. After in vivo ES (20Hz, 2× motor threshold, 0.2ms, 1h) of the intact sciatic nerve in adult Fischer344 rats, sensory neurons showed a 2-fold increase in in vitro neurite length one week later compared to sham animals, an effect not observed one day after ES. Longer ES (7h) and repeated ES (7days, 1h each) also increased growth by 56-67% one week later, but provided no additional benefit. In vivo growth of dorsal column sensory axons into a graft of bone marrow stromal cells 4weeks after a cervical spinal cord lesion was also enhanced with a single post-injury 1h ES of the intact sciatic nerve and was also observed after repeated ES without inducing pain-like behavior. While ES did not result in sensory functional recovery, our data indicate that ES has time-dependent influences on the regenerative capacity of sensory neurons and might further enhance axonal regeneration in combinatorial approaches after SCI. Copyright © 2017 Elsevier Inc. All rights reserved.

  18. Axonal transmission in the retina introduces a small dispersion of relative timing in the ganglion cell population response.

    Directory of Open Access Journals (Sweden)

    Günther Zeck

    Full Text Available BACKGROUND: Visual stimuli elicit action potentials in tens of different retinal ganglion cells. Each ganglion cell type responds with a different latency to a given stimulus, thus transforming the high-dimensional input into a temporal neural code. The timing of the first spikes between different retinal projection neurons cells may further change along axonal transmission. The purpose of this study is to investigate if intraretinal conduction velocity leads to a synchronization or dispersion of the population signal leaving the eye. METHODOLOGY/PRINCIPAL FINDINGS: We 'imaged' the initiation and transmission of light-evoked action potentials along individual axons in the rabbit retina at micron-scale resolution using a high-density multi-transistor array. We measured unimodal conduction velocity distributions (1.3±0.3 m/sec, mean ± SD for axonal populations at all retinal eccentricities with the exception of the central part that contains myelinated axons. The velocity variance within each piece of retina is caused by ganglion cell types that show narrower and slightly different average velocity tuning. Ganglion cells of the same type respond with similar latency to spatially homogenous stimuli and conduct with similar velocity. For ganglion cells of different type intraretinal conduction velocity and response latency to flashed stimuli are negatively correlated, indicating that differences in first spike timing increase (up to 10 msec. Similarly, the analysis of pair-wise correlated activity in response to white-noise stimuli reveals that conduction velocity and response latency are negatively correlated. CONCLUSION/SIGNIFICANCE: Intraretinal conduction does not change the relative spike timing between ganglion cells of the same type but increases spike timing differences among ganglion cells of different type. The fastest retinal ganglion cells therefore act as indicators of new stimuli for postsynaptic neurons. The intraretinal dispersion

  19. Limited trafficking of a neurotropic virus through inefficient retrograde axonal transport and the type I interferon response.

    Directory of Open Access Journals (Sweden)

    Karen Z Lancaster


    Full Text Available Poliovirus is an enteric virus that rarely invades the human central nervous system (CNS. To identify barriers limiting poliovirus spread from the periphery to CNS, we monitored trafficking of 10 marked viruses. After oral inoculation of susceptible mice, poliovirus was present in peripheral neurons, including vagus and sciatic nerves. To model viral trafficking in peripheral neurons, we intramuscularly injected mice with poliovirus, which follows a muscle-sciatic nerve-spinal cord-brain route. Only 20% of the poliovirus population successfully moved from muscle to brain, and three barriers limiting viral trafficking were identified. First, using light-sensitive viruses, we found limited viral replication in peripheral neurons. Second, retrograde axonal transport of poliovirus in peripheral neurons was inefficient; however, the efficiency was increased upon muscle damage, which also increased the transport efficiency of a non-viral neural tracer, wheat germ agglutinin. Third, using susceptible interferon (IFN alpha/beta receptor knockout mice, we demonstrated that the IFN response limited viral movement from the periphery to the brain. Surprisingly, the retrograde axonal transport barrier was equivalent in strength to the IFN barrier. Illustrating the importance of barriers created by the IFN response and inefficient axonal transport, IFN alpha/beta receptor knockout mice with muscle damage permitted 80% of the viral population to access the brain, and succumbed to disease three times faster than mice with intact barriers. These results suggest that multiple separate barriers limit poliovirus trafficking from peripheral neurons to the CNS, possibly explaining the rare incidence of paralytic poliomyelitis. This study identifies inefficient axonal transport as a substantial barrier to poliovirus trafficking in peripheral neurons, which may limit CNS access for other viruses.

  20. An αII Spectrin-Based Cytoskeleton Protects Large-Diameter Myelinated Axons from Degeneration. (United States)

    Huang, Claire Yu-Mei; Zhang, Chuansheng; Zollinger, Daniel R; Leterrier, Christophe; Rasband, Matthew N


    Axons must withstand mechanical forces, including tension, torsion, and compression. Spectrins and actin form a periodic cytoskeleton proposed to protect axons against these forces. However, because spectrins also participate in assembly of axon initial segments (AISs) and nodes of Ranvier, it is difficult to uncouple their roles in maintaining axon integrity from their functions at AIS and nodes. To overcome this problem and to determine the importance of spectrin cytoskeletons for axon integrity, we generated mice with αII spectrin-deficient peripheral sensory neurons. The axons of these neurons are very long and exposed to the mechanical forces associated with limb movement; most lack an AIS, and some are unmyelinated and have no nodes. We analyzed αII spectrin-deficient mice of both sexes and found that, in myelinated axons, αII spectrin forms a periodic cytoskeleton with βIV and βII spectrin at nodes of Ranvier and paranodes, respectively, but that loss of αII spectrin disrupts this organization. Avil-cre;Sptan1 f/f mice have reduced numbers of nodes, disrupted paranodal junctions, and mislocalized Kv1 K + channels. We show that the density of nodal βIV spectrin is constant among axons, but the density of nodal αII spectrin increases with axon diameter. Remarkably, Avil-cre;Sptan1 f/f mice have intact nociception and small-diameter axons, but severe ataxia due to preferential degeneration of large-diameter myelinated axons. Our results suggest that nodal αII spectrin helps resist the mechanical forces experienced by large-diameter axons, and that αII spectrin-dependent cytoskeletons are also required for assembly of nodes of Ranvier. SIGNIFICANCE STATEMENT A periodic axonal cytoskeleton consisting of actin and spectrin has been proposed to help axons resist the mechanical forces to which they are exposed (e.g., compression, torsion, and stretch). However, until now, no vertebrate animal model has tested the requirement of the spectrin cytoskeleton in

  1. Septin 7: Actin cross-organization is required for axonal association of Schwann cells

    Directory of Open Access Journals (Sweden)

    Alejandro D Roth


    Full Text Available Myelin sheaths present two distinct domains: compacted myelin spirals and flanking non-compacted cytoplasmic channels, where lipid and protein segregation is established by unknown mechanisms. Septins, a conserved family of membrane and cytoskeletal interacting GTPases, form intracellular diffusion barriers during cell division and neurite extension and are expressed in myelinating cells. Septins, particularly septin 7 (Sept7, the central constituent of septin polymers, are associated with the cytoplasmic channels of myelinating cells. Here we show that Schwann cells deprived of Sept7 fail to wrap around axons from dorsal root ganglion neurons and exhibit disorganization of the actin cytoskeleton. Likewise, Sept7 distribution is dependent on microfilament but not microtubule organization.

  2. Modality-Based Organization of Ascending Somatosensory Axons in the Direct Dorsal Column Pathway (United States)

    Niu, Jingwen; Ding, Long; Li, Jian J.; Kim, Hyukmin; Liu, Jiakun; Li, Haipeng; Moberly, Andrew; Badea, Tudor C.; Duncan, Ian D.; Son, Young-Jin; Scherer, Steven S.


    The long-standing doctrine regarding the functional organization of the direct dorsal column (DDC) pathway is the “somatotopic map” model, which suggests that somatosensory afferents are primarily organized by receptive field instead of modality. Using modality-specific genetic tracing, here we show that ascending mechanosensory and proprioceptive axons, two main types of the DDC afferents, are largely segregated into a medial–lateral pattern in the mouse dorsal column and medulla. In addition, we found that this modality-based organization is likely to be conserved in other mammalian species, including human. Furthermore, we identified key morphological differences between these two types of afferents, which explains how modality segregation is formed and why a rough “somatotopic map” was previously detected. Collectively, our results establish a new functional organization model for the mammalian direct dorsal column pathway and provide insight into how somatotopic and modality-based organization coexist in the central somatosensory pathway. PMID:24198362

  3. Pharmacogenetic stimulation of neuronal activity increases myelination in an axon-specific manner. (United States)

    Mitew, Stanislaw; Gobius, Ilan; Fenlon, Laura R; McDougall, Stuart J; Hawkes, David; Xing, Yao Lulu; Bujalka, Helena; Gundlach, Andrew L; Richards, Linda J; Kilpatrick, Trevor J; Merson, Tobias D; Emery, Ben


    Mounting evidence suggests that neuronal activity influences myelination, potentially allowing for experience-driven modulation of neural circuitry. The degree to which neuronal activity is capable of regulating myelination at the individual axon level is unclear. Here we demonstrate that stimulation of somatosensory axons in the mouse brain increases proliferation and differentiation of oligodendrocyte progenitor cells (OPCs) within the underlying white matter. Stimulated axons display an increased probability of being myelinated compared to neighboring non-stimulated axons, in addition to being ensheathed with thicker myelin. Conversely, attenuating neuronal firing reduces axonal myelination in a selective activity-dependent manner. Our findings reveal that the process of selecting axons for myelination is strongly influenced by the relative activity of individual axons within a population. These observed cellular changes are consistent with the emerging concept that adaptive myelination is a key mechanism for the fine-tuning of neuronal circuitry in the mammalian CNS.

  4. Effect of vesicle traps on traffic jam formation in fast axonal transport. (United States)

    Kuznetsov, A V


    The purpose of this paper is to develop a model for simulation of the formation of organelle traps in fast axonal transport. Such traps may form in the regions of microtubule polar mismatching. Depending on the orientation of microtubules pointing toward the trap region, these traps can accumulate either plus-end or minus-end oriented vesicles. The model predicts that the maximum concentrations of organelles occur at the boundaries of the trap regions; the overall concentration of organelles in the axon with traps is greatly increased compared to that in a healthy axon, which is expected to contribute to mechanical damages of the axon. The organelle traps induce hindrance to organelle transport down the axon; the total organelle flux down the axon with traps is found to be significantly reduced compared to that in a healthy axon. Copyright 2010 Elsevier Inc. All rights reserved.

  5. Efficient retrograde transport of pseudorabies virus within neurons requires local protein synthesis in axons. (United States)

    Koyuncu, Orkide O; Perlman, David H; Enquist, Lynn W


    After replicating in epithelial cells, alphaherpesviruses such as pseudorabies virus (PRV) invade axons of peripheral nervous system neurons and undergo retrograde transport toward the distant cell bodies. Although several viral proteins engage molecular motors to facilitate transport, the initial steps and neuronal responses to infection are poorly understood. Using compartmented neuron cultures to physically separate axon infection from cell bodies, we found that PRV infection induces local protein synthesis in axons, including proteins involved in cytoskeletal remodeling, intracellular trafficking, signaling, and metabolism. This rapid translation of axonal mRNAs is required for efficient PRV retrograde transport and infection of cell bodies. Furthermore, induction of axonal damage, which also induces local protein synthesis, prior to infection reduces virion trafficking, suggesting that host damage signals and virus particles compete for retrograde transport. Thus, similar to axonal damage, virus infection induces local protein translation in axons, and viruses likely exploit this response for invasion. Copyright © 2013 Elsevier Inc. All rights reserved.

  6. Retinal ganglion cells: Energetics, compartmentation, axonal transport, cytoskeletons and vulnerability. (United States)

    Yu, Dao-Yi; Cringle, Stephen J; Balaratnasingam, Chandrakumar; Morgan, William H; Yu, Paula K; Su, Er-Ning


    Retinal ganglion cells (RGCs) are specialized projection neurons that relay an immense amount of visual information from the retina to the brain. RGC signal inputs are collected by dendrites and output is distributed from the cell body via very thin (0.5-1 μm) and long (∼50 mm) axons. The RGC cell body is larger than other retinal neurons, but is still only a very small fraction (one ten thousandths) of the length and total surface area of the axon. The total distance traversed by RGCs extends from the retina, starting from synapses with bipolar and amacrine cells, to the brain, to synapses with neurons in the lateral geniculate nucleus. This review will focus on the energy demands of RGCs and the relevant tissues that surround them. RGC survival and function unexceptionally depends upon free energy, predominantly adenosine triphosphate (ATP). RGC energy metabolism is vastly different when compared to that of the photoreceptors. Each subcellular component of the RGC is remarkably different in terms of structure, function and extracellular environment. The energy demands and distribution of each component are also distinct as evidenced by the uneven distribution of mitochondria and ATP within the RGC - signifying the presence of intracellular energy gradients. In this review we will describe RGCs as having four subcellular components, (1) Dendrites, (2) Cell body, (3) Non-myelinated axon, including intraocular and optic nerve head portions, and (4) Myelinated axon, including the intra-orbital and intracranial portions. We will also describe how RGCs integrate information from each subcellular component in order achieve intracellular homeostatic stability as well as respond to perturbations in the extracellular environment. The possible cellular mechanisms such as axonal transport and axonal cytoskeleton proteins that are involved in maintaining RGC energy homeostasis during normal and disease conditions will also be discussed in depth. The emphasis of this

  7. Treatment with metallothionein prevents demyelination and axonal damage and increases oligodendrocyte precursors and tissue repair during experimental autoimmune encephalomyelitis

    DEFF Research Database (Denmark)

    Penkowa, Milena; Hidalgo, Juan


    and neuroprotective proteins that are expressed during EAE and MS. We have shown recently that exogenous administration of Zn-MT-II to Lewis rats with EAE significantly reduced clinical symptoms and the inflammatory response, oxidative stress, and apoptosis of the infiltrated central nervous system areas. We show...... for the first time that Zn-MT-II treatment during EAE significantly prevents demyelination and axonal damage and transection, and stimulates oligodendroglial regeneration from precursor cells, as well as the expression of the growth factors basic fibroblast growth factor (bFGF), transforming growth factor (TGF...

  8. Squid Giant Axon Contains Neurofilament Protein mRNA but does not Synthesize Neurofilament Proteins. (United States)

    Gainer, Harold; House, Shirley; Kim, Dong Sun; Chin, Hemin; Pant, Harish C


    When isolated squid giant axons are incubated in radioactive amino acids, abundant newly synthesized proteins are found in the axoplasm. These proteins are translated in the adaxonal Schwann cells and subsequently transferred into the giant axon. The question as to whether any de novo protein synthesis occurs in the giant axon itself is difficult to resolve because the small contribution of the proteins possibly synthesized intra-axonally is not easily distinguished from the large amounts of the proteins being supplied from the Schwann cells. In this paper, we reexamine this issue by studying the synthesis of endogenous neurofilament (NF) proteins in the axon. Our laboratory previously showed that NF mRNA and protein are present in the squid giant axon, but not in the surrounding adaxonal glia. Therefore, if the isolated squid axon could be shown to contain newly synthesized NF protein de novo, it could not arise from the adaxonal glia. The results of experiments in this paper show that abundant 3H-labeled NF protein is synthesized in the squid giant fiber lobe containing the giant axon's neuronal cell bodies, but despite the presence of NF mRNA in the giant axon no labeled NF protein is detected in the giant axon. This lends support to the glia-axon protein transfer hypothesis which posits that the squid giant axon obtains newly synthesized protein by Schwann cell transfer and not through intra-axonal protein synthesis, and further suggests that the NF mRNA in the axon is in a translationally repressed state.

  9. Neocortical axon arbors trade-off material and conduction delay conservation.

    Directory of Open Access Journals (Sweden)

    Julian M L Budd


    Full Text Available The brain contains a complex network of axons rapidly communicating information between billions of synaptically connected neurons. The morphology of individual axons, therefore, defines the course of information flow within the brain. More than a century ago, Ramón y Cajal proposed that conservation laws to save material (wire length and limit conduction delay regulate the design of individual axon arbors in cerebral cortex. Yet the spatial and temporal communication costs of single neocortical axons remain undefined. Here, using reconstructions of in vivo labelled excitatory spiny cell and inhibitory basket cell intracortical axons combined with a variety of graph optimization algorithms, we empirically investigated Cajal's conservation laws in cerebral cortex for whole three-dimensional (3D axon arbors, to our knowledge the first study of its kind. We found intracortical axons were significantly longer than optimal. The temporal cost of cortical axons was also suboptimal though far superior to wire-minimized arbors. We discovered that cortical axon branching appears to promote a low temporal dispersion of axonal latencies and a tight relationship between cortical distance and axonal latency. In addition, inhibitory basket cell axonal latencies may occur within a much narrower temporal window than excitatory spiny cell axons, which may help boost signal detection. Thus, to optimize neuronal network communication we find that a modest excess of axonal wire is traded-off to enhance arbor temporal economy and precision. Our results offer insight into the principles of brain organization and communication in and development of grey matter, where temporal precision is a crucial prerequisite for coincidence detection, synchronization and rapid network oscillations.

  10. Coevolution of axon guidance molecule Slit and its receptor Robo.

    Directory of Open Access Journals (Sweden)

    Qi Yu

    Full Text Available Coevolution is important for the maintenance of the interaction between a ligand and its receptor during evolution. The interaction between axon guidance molecule Slit and its receptor Robo is critical for the axon repulsion in neural tissues, which is evolutionarily conserved from planarians to humans. However, the mechanism of coevolution between Slit and Robo remains unclear. In this study, we found that coordinated amino acid changes took place at interacting sites of Slit and Robo by comparing the amino acids at these sites among different organisms. In addition, the high level correlation between evolutionary rate of Slit and Robo was identified in vertebrates. Furthermore, the sites under positive selection of slit and robo were detected in the same lineage such as mosquito and teleost. Overall, our results provide evidence for the coevolution between Slit and Robo.

  11. Activated retinal glia mediated axon regeneration in experimental glaucoma. (United States)

    Lorber, Barbara; Guidi, Alessandra; Fawcett, James W; Martin, Keith R


    Glaucoma, a leading cause of blindness, is a neurodegenerative disease characterized by progressive loss of retinal ganglion cell axons in the optic nerve and their cell bodies in the retina. Reactive retinal glial changes have been observed in glaucoma but the role of such glial changes in the pathogenesis of the condition remains unclear. In the present study we found that retinal ganglion cells in an experimental animal model of glaucoma have an increased axon regenerative potential. Regeneration of adult rat retinal ganglion cell axons after optic nerve crush was significantly increased in vivo when combined with intraocular pressure-induced experimental glaucoma. This enhanced axon regeneration response was correlated with a significant increase in activation of glial fibrillary acidic protein+retinal glia. Using a dissociated retinal ganglion cell culture model we showed that reducing the number of activated retinal glia with a glial specific toxin, α-Aminoadipic acid, significantly reduced the growth potential of retinal ganglion cells from glaucomatous rat eyes, suggesting that activated retinal glia mediate, at least in part, the growth promoting effect. This was shown to be mediated by both membrane-bound and soluble glial-derived factors. Neurotrophin and ciliary neurotrophic/leukemia inhibitory factor blockers did not affect the regenerative potential, excluding these growth factors as principal mediators of the enhanced growth response occurring in glaucomatous retinal cultures. These observations are the first to reveal that retinal ganglion cells from glaucomatous rat eyes have an enhanced regenerative capacity. Furthermore, our results suggest that activated retinal glia mediate at least part of this response. Further work to understand and enhance the regeneration-promoting effect of activated retinal glia is required to determine if this approach could be useful as part of a therapeutic strategy to encourage optic nerve regeneration in glaucoma

  12. [Craniocerebral trauma: magnetic resonance imaging of diffuse axonal injury]. (United States)

    Mallouhi, A


    Acceleration-deceleration rotational brain trauma is a common cause of disability or death in young adults and often leads to a focal destruction of axons. The resulting pathology, axonal shear injury is referred to as diffuse axonal injury (DAI). The DAI-associated lesions occur bilaterally, are widely dispersed and have been observed in the surface and deep white matter. They are found near to and far from the impact site. When DAI is clinically suspected, magnetic resonance imaging (MRI) is the method of choice for further clarification, especially in patients where cranial computed tomography (CT) is inconspicuous. To investigate the presence of DAI after traumatic brain injury (TBI), a multimodal MRI approach is applied including the common structural and also functional imaging sequences. For structural MRI, fluid-attenuated inversion recovery (FLAIR) weighted and susceptibility contrast imaging (SWI) are the sequences mainly used. The SWI technique is extremely sensitive to blood breakdown products, which appear as small signal voids at three locations, at the gray-white interface, in the corpus callosum and in the brain stem. Functional MRI comprises a group of constantly developing techniques that have great potential in optimal evaluation of the white matter in patients after craniocerebral trauma. These imaging techniques allow the visualization of changes associated with shear injuries, such as functional impairment of axons and decreased blood flow and abnormal metabolic activity of the brain parts affected. The multimodal MRI approach in patients with DAI results in a more detailed and differentiated representation of the underlying pathophysiological changes of the injured nerve tracts and helps to improve the diagnostic and prognostic accuracy of MRI. When DAI is suspected multimodal MRI should be performed as soon as possible after craniocerebral injury.

  13. Two stable steady states in the Hodgkin-Huxley axons


    Aihara, K.; Matsumoto, G.


    Two stable steady states were found in the numerical solution of the Hodgkin-Huxley equations for the intact squid axon bathed in potassium-rich sea water with an externally applied inward current. Under the conditions the two stable steady-states exist, the Hodgkin-Huxley equations have a complex bifurcation structure including, in addition to the two stable steady-states, a stable limit cycle, two unstable equilibrium points, and one asymptotically stable equilibrium point. It was also conc...

  14. PirB is a novel potential therapeutic target for enhancing axonal regeneration and synaptic plasticity following CNS injury in mammals. (United States)

    Gou, Zhaoyu; Mi, Yajing; Jiang, Fengliang; Deng, Bin; Yang, Jun; Gou, Xingchun


    A major barrier to axonal regeneration in mammals is the unfavorable extracellular environment that develops following injury to the central nervous system (CNS). In particular, three myelin-associated inhibitory proteins (MAIs) - Nogo, myelin-associated glycoprotein (MAG) and oligodendrocyte myelin glycoprotein (OMgp) - are known to inhibit axonal regeneration and functional recovery. These MAIs share a common receptor, glycosylphosphatidylinositol-anchored Nogo receptor (NgR). However, paired immunoglobulin-like receptor B (PirB) - which was originally identified as a receptor for class I major histocompatibility complex (MHCI) in the immune system - is also expressed in neurones and plays a similarly inhibitory role in axonal regeneration and synaptic plasticity following CNS injury through its association with MAIs. Importantly, suppression of PirB activity through antibody antagonism or genetic means can partially relieve the inhibition of neurite outgrowth in vitro and in vivo. In this review, we present the molecular features, expression patterns and known signaling pathways of PirB, and we specifically focus on putative roles for PirB in the CNS and its potential as a target of molecular therapies for enhancing axonal regeneration and synaptic plasticity following CNS injury.

  15. Internalization and Axonal Transport of the HIV Glycoprotein gp120 (United States)

    Berth, Sarah; Caicedo, Hector Hugo; Sarma, Tulika; Morfini, Gerardo


    The HIV glycoprotein gp120, a neurotoxic HIV glycoprotein that is overproduced and shed by HIV-infected macrophages, is associated with neurological complications of HIV such as distal sensory polyneuropathy, but interactions of gp120 in the peripheral nervous system remain to be characterized. Here, we demonstrate internalization of extracellular gp120 in a manner partially independent of binding to its coreceptor CXCR4 by F11 neuroblastoma cells and cultured dorsal root ganglion neurons. Immunocytochemical and pharmacological experiments indicate that gp120 does not undergo trafficking through the endolysosomal pathway. Instead, gp120 is mainly internalized through lipid rafts in a cholesterol-dependent manner, with a minor fraction being internalized by fluid phase pinocytosis. Experiments using compartmentalized microfluidic chambers further indicate that, after internalization, endocytosed gp120 selectively undergoes retrograde but not anterograde axonal transport from axons to neuronal cell bodies. Collectively, these studies illuminate mechanisms of gp120 internalization and axonal transport in peripheral nervous system neurons, providing a novel framework for mechanisms for gp120 neurotoxicity. PMID:25636314

  16. Inner membrane fusion mediates spatial distribution of axonal mitochondria (United States)

    Yu, Yiyi; Lee, Hao-Chih; Chen, Kuan-Chieh; Suhan, Joseph; Qiu, Minhua; Ba, Qinle; Yang, Ge


    In eukaryotic cells, mitochondria form a dynamic interconnected network to respond to changing needs at different subcellular locations. A fundamental yet unanswered question regarding this network is whether, and if so how, local fusion and fission of individual mitochondria affect their global distribution. To address this question, we developed high-resolution computational image analysis techniques to examine the relations between mitochondrial fusion/fission and spatial distribution within the axon of Drosophila larval neurons. We found that stationary and moving mitochondria underwent fusion and fission regularly but followed different spatial distribution patterns and exhibited different morphology. Disruption of inner membrane fusion by knockdown of dOpa1, Drosophila Optic Atrophy 1, not only increased the spatial density of stationary and moving mitochondria but also changed their spatial distributions and morphology differentially. Knockdown of dOpa1 also impaired axonal transport of mitochondria. But the changed spatial distributions of mitochondria resulted primarily from disruption of inner membrane fusion because knockdown of Milton, a mitochondrial kinesin-1 adapter, caused similar transport velocity impairment but different spatial distributions. Together, our data reveals that stationary mitochondria within the axon interconnect with moving mitochondria through fusion and fission and that local inner membrane fusion between individual mitochondria mediates their global distribution. PMID:26742817

  17. Dendritic and Axonal Wiring Optimization of Cortical GABAergic Interneurons. (United States)

    Anton-Sanchez, Laura; Bielza, Concha; Benavides-Piccione, Ruth; DeFelipe, Javier; Larrañaga, Pedro


    The way in which a neuronal tree expands plays an important role in its functional and computational characteristics. We aimed to study the existence of an optimal neuronal design for different types of cortical GABAergic neurons. To do this, we hypothesized that both the axonal and dendritic trees of individual neurons optimize brain connectivity in terms of wiring length. We took the branching points of real three-dimensional neuronal reconstructions of the axonal and dendritic trees of different types of cortical interneurons and searched for the minimal wiring arborization structure that respects the branching points. We compared the minimal wiring arborization with real axonal and dendritic trees. We tested this optimization problem using a new approach based on graph theory and evolutionary computation techniques. We concluded that neuronal wiring is near-optimal in most of the tested neurons, although the wiring length of dendritic trees is generally nearer to the optimum. Therefore, wiring economy is related to the way in which neuronal arborizations grow irrespective of the marked differences in the morphology of the examined interneurons.

  18. Axonal Actin Transport Driven By Metastable Actin Filaments (United States)

    Chakrabarty, Nilaj; Ganguly, Archan; Roy, Subhojit; Jung, Peter

    Actin is one of the key constituents of the neuronal cytoskeleton and is responsible for driving important cellular processes like axon elongation. Axonal actin is synthesized in the cell body and transported at rates of 0.25 - 3 mm/day, as shown by in-vivo pulse-chase radiolabelling studies. However, the underlying transport mechanisms are unknown. Recent experiments in cultured neurons have revealed a dynamic network of metastable actin filaments (actin trails). Actin trails seem to originate from focal actin hotspots which colocalize with stationary endosomes. Interestingly, the number of actin trails extending anterogradely is higher than the ones extending retrogradely. We hypothesize that the bulk axonal transport of actin originates from this directional asymmetry of the number of actin trails. To test this, we constructed a computational model of actin trail growth and simulated the pulse-chase experiment. In our model, local, metastable trails, which grow with their barbed ends anchored to the hotspots, drive the bulk anterograde transport. Our results indicate that the observed bias of the nucleation probabilities and the elongation rate of actin trails are sufficient to drive the bulk transport of actin at rates that agree with in-vivo pulse chase experiments.

  19. Prediction of Functional Outcome in Axonal Guillain-Barre Syndrome. (United States)

    Sung, Eun Jung; Kim, Dae Yul; Chang, Min Cheol; Ko, Eun Jae


    To identify the factors that could predict the functional outcome in patients with the axonal type of Guillain-Barre syndrome (GBS). Two hundred and two GBS patients admitted to our university hospital between 2003 and 2014 were reviewed retrospectively. We defined a good outcome as being "able to walk independently at 1 month after onset" and a poor outcome as being "unable to walk independently at 1 month after onset". We evaluated the factors that differed between the good and poor outcome groups. Twenty-four patients were classified into the acute motor axonal neuropathy type. There was a statistically significant difference between the good and poor outcome groups in terms of the GBS disability score at admission, and GBS disability score and Medical Research Council sum score at 1 month after admission. In an electrophysiologic analysis, the good outcome group showed greater amplitude of median, ulnar, deep peroneal, and posterior tibial nerve compound muscle action potentials (CMAP) and greater amplitude of median, ulnar, and superficial peroneal sensory nerve action potentials (SNAP) than the poor outcome group. A lower GBS disability score at admission, high amplitude of median, ulnar, deep peroneal, and posterior tibial CMAPs, and high amplitude of median, ulnar, and superficial peroneal SNAPs were associated with being able to walk at 1 month in patients with axonal GBS.

  20. Sodium Channel β2 Subunits Prevent Action Potential Propagation Failures at Axonal Branch Points. (United States)

    Cho, In Ha; Panzera, Lauren C; Chin, Morven; Hoppa, Michael B


    Neurotransmitter release depends on voltage-gated Na + channels (Na v s) to propagate an action potential (AP) successfully from the axon hillock to a synaptic terminal. Unmyelinated sections of axon are very diverse structures encompassing branch points and numerous presynaptic terminals with undefined molecular partners of Na + channels. Using optical recordings of Ca 2+ and membrane voltage, we demonstrate here that Na + channel β2 subunits (Na v β2s) are required to prevent AP propagation failures across the axonal arborization of cultured rat hippocampal neurons (mixed male and female). When Na v β2 expression was reduced, we identified two specific phenotypes: (1) membrane excitability and AP-evoked Ca 2+ entry were impaired at synapses and (2) AP propagation was severely compromised with >40% of axonal branches no longer responding to AP-stimulation. We went on to show that a great deal of electrical signaling heterogeneity exists in AP waveforms across the axonal arborization independent of axon morphology. Therefore, Na v β2 is a critical regulator of axonal excitability and synaptic function in unmyelinated axons. SIGNIFICANCE STATEMENT Voltage-gated Ca 2+ channels are fulcrums of neurotransmission that convert electrical inputs into chemical outputs in the form of vesicle fusion at synaptic terminals. However, the role of the electrical signal, the presynaptic action potential (AP), in modulating synaptic transmission is less clear. What is the fidelity of a propagating AP waveform in the axon and what molecules shape it throughout the axonal arborization? Our work identifies several new features of AP propagation in unmyelinated axons: (1) branches of a single axonal arborization have variable AP waveforms independent of morphology, (2) Na + channel β2 subunits modulate AP-evoked Ca 2+ -influx, and (3) β2 subunits maintain successful AP propagation across the axonal arbor. These findings are relevant to understanding the flow of excitation in the

  1. Structure and function of the amygdaloid NPY system: NPY Y2 receptors regulate excitatory and inhibitory synaptic transmission in the centromedial amygdala. (United States)

    Wood, J; Verma, D; Lach, G; Bonaventure, P; Herzog, H; Sperk, G; Tasan, R O


    The amygdala is essential for generating emotional-affective behaviors. It consists of several nuclei with highly selective, elaborate functions. In particular, the central extended amygdala, consisting of the central amygdala (CEA) and the bed nucleus of the stria terminalis (BNST) is an essential component actively controlling efferent connections to downstream effectors like hypothalamus and brain stem. Both, CEA and BNST contain high amounts of different neuropeptides that significantly contribute to synaptic transmission. Among these, neuropeptide Y (NPY) has emerged as an important anxiolytic and fear-reducing neuromodulator. Here, we characterized the expression, connectivity and electrophysiological function of NPY and Y2 receptors within the CEA. We identified several NPY-expressing neuronal populations, including somatostatin- and calretinin-expressing neurons. Furthermore, in the main intercalated nucleus, NPY is expressed primarily in dopamine D1 receptor-expressing neurons but also in interspersed somatostatin-expressing neurons. Interestingly, NPY neurons did not co-localize with the Y2 receptor. Retrograde tract tracing experiments revealed that NPY neurons reciprocally connect the CEA and BNST. Functionally, the Y2 receptor agonist PYY3-36, reduced both, inhibitory as well as excitatory synaptic transmission in the centromedial amygdala (CEm). However, we also provide evidence that lack of NPY or Y2 receptors results in increased GABA release specifically at inhibitory synapses in the CEm. Taken together, our findings suggest that NPY expressed by distinct populations of neurons can modulate afferent and efferent projections of the CEA via presynaptic Y2 receptors located at inhibitory and excitatory synapses.

  2. Simulated auditory nerve axon demyelination alters sensitivity and response timing to extracellular stimulation. (United States)

    Resnick, Jesse M; O'Brien, Gabrielle E; Rubinstein, Jay T


    Since cochlear implant function involves direct depolarization of spiral ganglion neurons (SGNs) by applied current, SGN physiological health must be an important factor in cochlear implant (CI) outcomes. This expected relationship has, however, been difficult to confirm in implant recipients. Suggestively, animal studies have demonstrated both acute and progressive SGN ultrastructural changes (notably axon demyelination), even in the absence of soma death, and corresponding altered physiology following sensorineural deafening. Whether such demyelination occurs in humans and how such changes might impact CI function remains unknown. To approach this problem, we incorporated SGN demyelination into a biophysical model of extracellular stimulation of SGN fibers. Our approach enabled exploration of the entire parameter space corresponding to simulated myelin diameter and extent of fiber affected. All simulated fibers were stimulated distally with anodic monophasic, cathodic monophasic, anode-phase-first (AF) biphasic, and cathode-phase-first (CF) biphasic pulses from an extracellular disc electrode and monitored for spikes centrally. Not surprisingly, axon sensitivity generally decreased with demyelination, resulting in elevated thresholds, however, this effect was strongly non-uniform. Fibers with severe demyelination affecting only the most peripheral nodes responded nearly identically to normally myelinated fibers. Additionally, partial demyelination (<50%) yielded only minimal increases in threshold even when the entire fiber was impacted. The temporal effects of demyelination were more unexpected. Both latency and jitter of responses demonstrated resilience to modest changes but exhibited strongly non-monotonic and stimulus-dependent relationships to more profound demyelination. Normal, and modestly demyelinated fibers, were more sensitive to cathodic than anodic monophasic pulses and to CF than AF biphasic pulses, however, when demyelination was more severe these

  3. Enhanced microglial clearance of myelin debris in T cell-infiltrated central nervous system

    DEFF Research Database (Denmark)

    Nielsen, Helle Hvilsted; Ladeby, Rune; Fenger, Christina


    Acute multiple sclerosis lesions are characterized by accumulation of T cells and macrophages, destruction of myelin and oligodendrocytes, and axonal damage. There is, however, limited information on neuroimmune interactions distal to sites of axonal damage in the T cell-infiltrated central nervous...... system. We investigated T-cell infiltration, myelin clearance, microglial activation, and phagocytic activity distal to sites of axonal transection through analysis of the perforant pathway deafferented dentate gyrus in SJL mice that had received T cells specific for myelin basic protein (TMBP...

  4. Sound-Evoked Activity Influences Myelination of Brainstem Axons in the Trapezoid Body. (United States)

    Sinclair, James L; Fischl, Matthew J; Alexandrova, Olga; Heβ, Martin; Grothe, Benedikt; Leibold, Christian; Kopp-Scheinpflug, Conny


    Plasticity of myelination represents a mechanism to tune the flow of information by balancing functional requirements with metabolic and spatial constraints. The auditory system is heavily myelinated and operates at the upper limits of action potential generation frequency and speed observed in the mammalian CNS. This study aimed to characterize the development of myelin within the trapezoid body, a central auditory fiber tract, and determine the influence sensory experience has on this process in mice of both sexes. We find that in vitro conduction speed doubles following hearing onset and the ability to support high-frequency firing increases concurrently. Also in this time, the diameter of trapezoid body axons and the thickness of myelin double, reaching mature-like thickness between 25 and 35 d of age. Earplugs were used to induce ∼50 dB elevation in auditory thresholds. If introduced at hearing onset, trapezoid body fibers developed thinner axons and myelin than age-matched controls. If plugged during adulthood, the thickest trapezoid body fibers also showed a decrease in myelin. These data demonstrate the need for sensory activity in both development and maintenance of myelin and have important implications in the study of myelin plasticity and how this could relate to sensorineural hearing loss following peripheral impairment. SIGNIFICANCE STATEMENT The auditory system has many mechanisms to maximize the dynamic range of its afferent fibers, which operate at the physiological limit of action potential generation, precision, and speed. In this study we demonstrate for the first time that changes in peripheral activity modifies the thickness of myelin in sensory neurons, not only in development but also in mature animals. The current study suggests that changes in CNS myelination occur as a downstream mechanism following peripheral deficit. Given the required submillisecond temporal precision for binaural auditory processing, reduced myelination might

  5. The disruption of mitochondrial axonal transport is an early event in neuroinflammation

    DEFF Research Database (Denmark)

    Errea, Oihana; Moreno, Beatriz; Gonzalez-Franquesa, Alba


    of neuroprotective therapies. Energy depletion due to mitochondrial dysfunction has been postulated as an important step in the damage of axons. This prompted us to study the effects of acute inflammation and oxidative stress on the morphology, transport, and function of mitochondria in axons. METHODS: Mouse......BACKGROUND: In brain inflammatory diseases, axonal damage is one of the most critical steps in the cascade that leads to permanent disability. Thus, identifying the initial events triggered by inflammation or oxidative stress that provoke axonal damage is critical for the development...... in axons, increasing the proportion of stationary mitochondria in axons after LPS challenge. Indeed, the two challenges used produced different effects: inflammation mostly reducing retrograde transport and oxidative stress slightly enhancing retrograde transportation. CONCLUSIONS: Neuroinflammation...

  6. Segregation of Axial Motor and Sensory Pathways via Heterotypic Trans-Axonal Signaling (United States)

    Gallarda, Benjamin W.; Bonanomi, Dario; Müller, Daniel; Brown, Arthur; Alaynick, William A.; Andrews, Shane E.; Lemke, Greg; Pfaff, Samuel L.; Marquardt, Till


    Execution of motor behaviors relies on circuitries effectively integrating immediate sensory feedback to efferent pathways controlling muscle activity. It remains unclear how, during neuromuscular circuit assembly, sensory and motor projections become incorporated into tightly coordinated, yet functionally separate pathways. We report that, within axial nerves, establishment of discrete afferent and efferent pathways depends on coordinate signaling between coextending sensory and motor projections. These heterotypic axon-axon interactions require motor axonal EphA3/EphA4 receptor tyrosine kinases activated by cognate sensory axonal ephrin-A ligands. Genetic elimination of trans-axonal ephrin-A → EphA signaling in mice triggers drastic motor-sensory miswiring, culminating in functional efferents within proximal afferent pathways. Effective assembly of a key circuit underlying motor behaviors thus critically depends on trans-axonal signaling interactions resolving motor and sensory projections into discrete pathways. PMID:18403711

  7. A Combinatorial Approach to Induce Sensory Axon Regeneration into the Dorsal Root Avulsed Spinal Cord

    DEFF Research Database (Denmark)

    Hoeber, Jan; Konig, Niclas; Trolle, Carl


    restores sensory functions. In this study, we elucidate mechanisms underlying stem cell-mediated ingrowth of sensory axons after dorsal root avulsion (DRA). We show that human spinal cord neural stem/progenitor cells (hscNSPC), and also, mesoporous silica particles loaded with growth factor mimetics (Meso......MIM), supported sensory axon regeneration. However, when hscNSPC and MesoMIM were combined, sensory axon regeneration failed. Morphological and tracing analysis showed that sensory axons grow through the newly established glial scar along “bridges” formed by migrating stem cells. Coimplantation of Meso......MIM prevented stem cell migration, “bridges” were not formed, and sensory axons failed to enter the spinal cord. MesoMIM applied alone supported sensory axons ingrowth, but without affecting glial scar formation. In vitro, the presence of MesoMIM significantly impaired migration of hscNSPC without affecting...

  8. Effects of beta 2 adrenergic agonists on axonal injury and mitochondrial metabolism in experimental autoimmune encephalomyelitis rats. (United States)

    Zhang, Z W; Qin, X Y; Che, F Y; Xie, G; Shen, L; Bai, Y Y


    The primary aims of this study were to investigate mitochondrial metabolism during experimental allergic encephalomyelitis (EAE) animal model axonal injury and to determine the correlation among neurological function scores, pathological changes, and the activities of the BB isoenzyme of creatine kinase (CK-BB), catalase (CAT), and calpain in the brain tissues of EAE rats. Another goal was to preliminarily define the mechanism of mitochondrial metabolism resulting from the effect of beta 2 adrenergic agonists in the process of EAE animal model axonal damage. EAE was induced in specific pathogen free Wistar rats by guinea pig spinal cord homogenate, complete Freund's adjuvant, and pertussis vaccine. We recorded the behavioral change in EAE rats, detected pathological changes in central nervous tissue, and observed the changes of the CK-BB, CAT, and calpain in the EAE rat brain and spinal cord. The results indicated that the average neurologic function score increased in the EAE group compared to that of the controls (P < 0.01). In addition, CAT and CK-BB activities significantly decreased and the calpain activity significantly increased compared with those of the control group (P < 0.05). The decrease of the activity of central nervous CK-BB and CAT content, as well as the increase of calpain activity at the highest time point were considered to be the consequences of EAE. Furthermore, the results revealed that use of salbutamol could alleviate disease symptoms and reduce the recurrence of the EAE disease.

  9. Modest enhancement of sensory axon regeneration in the sciatic nerve with conditional co-deletion of PTEN and SOCS3 in the dorsal root ganglia of adult mice. (United States)

    Gallaher, Zachary R; Steward, Oswald


    Axons within the peripheral nervous system are capable of regeneration, but full functional recovery is rare. Recent work has shown that conditional deletion of two key signaling inhibitors of the PI3K and Jak/Stat pathways-phosphatase and tensin homolog (PTEN) and suppressor of cytokine signaling-3 (SOCS3), respectively-promotes regeneration of normally non-regenerative central nervous system axons. Moreover, in studies of optic nerve regeneration, co-deletion of both PTEN and SOCS3 has an even greater effect. Here, we test the hypotheses (1) that PTEN deletion enhances axon regeneration following sciatic nerve crush and (2) that PTEN/SOCS3 co-deletion further promotes regeneration. PTEN fl/fl and PTEN/SOCS3 fl/fl mice received direct injections of AAV-Cre into the fourth and fifth lumbar dorsal root ganglia (DRG) two weeks prior to sciatic nerve crush. Western blot analysis of whole cell lysates from DRG using phospho-specific antibodies revealed that PTEN deletion did not enhance or prolong PI3K signaling following sciatic nerve crush. However, PTEN/SOCS3 co-deletion activated PI3K for at least 7 days post-injury in contrast to controls, where activation peaked at 3 days. Quantification of SCG10-expressing regenerating sensory axons in the sciatic nerve after crush injury revealed longer distance regeneration at 3 days post-injury with both PTEN and PTEN/SOCS3 co-deletion. Additionally, analysis of noxious thermosensation and mechanosensation with PTEN/SOCS3 co-deletion revealed enhanced sensation at 14 and 21 days after crush, respectively, after which all treatment groups reached the same functional plateau. These findings indicate that co-deletion of PTEN and SOCS3 results in modest but measureable enhancement of early regeneration of DRG axons following crush injury. Copyright © 2018 Elsevier Inc. All rights reserved.

  10. Inter-axonal interaction defines tiled presynaptic innervation in C. elegans


    Mizumoto, Kota; Shen, Kang


    Cellular interactions between neighboring axons are essential for global topographic map formation. Here we show that axonal interactions also precisely instruct the location of synapses. Motoneurons form en passant synapses in Caenorhabditis elegans. While axons from the same neuron class significantly overlap, each neuron innervates a unique and tiled segment of the muscle field by restricting its synapses to a distinct subaxonal domain—a phenomenon we term “synaptic tiling”. Using DA8 and ...

  11. Oligodendroglial MCT1 and Metabolic Support of Axons in Multiple Sclerosis (United States)


    AWARD NUMBER: W81XWH-14-1-0524 TITLE:Oligodendroglial MCT1 and Metabolic Support of Axons in Multiple Sclerosis PRINCIPAL INVESTIGATOR: Jeffrey D...29 Sep 2015 4. TITLE AND SUBTITLE Oligodendroglial MCT1 and Metabolic Support of Axons in Multiple Sclerosis 5a. CONTRACT NUMBER W81XWH-14-1-0524...MCT1 in injured oligodendroglia of multiple sclerosis patients contributes to axon neurodegeneration and that increasing MCT1 will be protective in the

  12. Acutely damaged axons are remyelinated in multiple sclerosis and experimental models of demyelination. (United States)

    Schultz, Verena; van der Meer, Franziska; Wrzos, Claudia; Scheidt, Uta; Bahn, Erik; Stadelmann, Christine; Brück, Wolfgang; Junker, Andreas


    Remyelination is in the center of new therapies for the treatment of multiple sclerosis to resolve and improve disease symptoms and protect axons from further damage. Although remyelination is considered beneficial in the long term, it is not known, whether this is also the case early in lesion formation. Additionally, the precise timing of acute axonal damage and remyelination has not been assessed so far. To shed light onto the interrelation between axons and the myelin sheath during de- and remyelination, we employed cuprizone- and focal lysolecithin-induced demyelination and performed time course experiments assessing the evolution of early and late stage remyelination and axonal damage. We observed damaged axons with signs of remyelination after cuprizone diet cessation and lysolecithin injection. Similar observations were made in early multiple sclerosis lesions. To assess the correlation of remyelination and axonal damage in multiple sclerosis lesions, we took advantage of a cohort of patients with early and late stage remyelinated lesions and assessed the number of APP- and SMI32- positive damaged axons and the density of SMI31-positive and silver impregnated preserved axons. Early de- and remyelinating lesions did not differ with respect to axonal density and axonal damage, but we observed a lower axonal density in late stage demyelinated multiple sclerosis lesions than in remyelinated multiple sclerosis lesions. Our findings suggest that remyelination may not only be protective over a long period of time, but may play an important role in the immediate axonal recuperation after a demyelinating insult. © 2017 The Authors GLIA Published by Wiley Periodicals, Inc.

  13. Ribosomes and polyribosomes are present in the squid giant axon: an immunocytochemical study. (United States)

    Sotelo, J R; Kun, A; Benech, J C; Giuditta, A; Morillas, J; Benech, C R


    Ribosomes and polyribosomes were detected by immuno-electron microscopy in the giant axon and small axons of the squid using a polyclonal antibody against rat brain ribosomes. The ribosomal fraction used as antigen was purified by ultracentrifugation on a sucrose density gradient and shown to contain ribosomal RNAs and native ribosomes. The polyclonal antibody raised in rabbits reacted with at least ten proteins on immunoblots of purified rat brain ribosomes as well as with a set of multiple ribosomal proteins prepared from the squid giant fiber lobe. Immunoreactions were performed on cryostat sections of the stellate nerve cut at a distance of more than 3 cm from the stellate ganglion, using pre-embedding techniques. Ribosomes and polyribosomes were identified within the giant axon and small axons using electron microscopic methods, following binding of peroxidase-conjugated anti-rabbit IgG secondary antibody. Polysomes were more frequently localized in peripheral axoplasm, including the cortical layer of the giant axon, and were generally associated with unidentified cytoskeletal filaments or with dense matrix material. The immunochemical demonstration of ribosomes and polyribosomes in the giant axon and small axons of the squid confirms similar observations in the squid and the goldfish obtained with the method of electron spectroscopic imaging, and strongly supports the view that a local system of protein synthesis is present in axons. The immunochemical method here described offers an alternative tool for the selective identification of ribosomes, and is likely to prove of value in the analyses of other axonal systems.

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

    DEFF Research Database (Denmark)

    Torpe, Nanna; Pocock, Roger David John


    , 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......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...

  15. Alterations in the Local Axonal Environment Influence Target Reinnervation and Neuronal Survival after Postnatal Axotomy

    National Research Council Canada - National Science Library

    Dainer, Hugh M


    Following peripheral nerve injury in adult animals, Schwann cells (SC) proliferate and provide guidance in the local axonal environment by generating the infrastructure along which regenerating nerves grow...

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

    Directory of Open Access Journals (Sweden)

    Christian Witzel


    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.

  17. The time course of ongoing activity during neuritis and following axonal transport disruption. (United States)

    Satkeviciute, Ieva; Goodwin, George; Bove, Geoffrey M; Dilley, Andrew


    Local nerve inflammation (neuritis) leads to ongoing activity and axonal mechanical sensitivity (AMS) along intact nociceptor axons, and disrupts axonal transport. This phenomenon forms the most feasible cause of radiating pain, such as sciatica. We have previously shown that axonal transport disruption without inflammation or degeneration also leads to AMS, but does not cause ongoing activity at the time point when AMS occurs, despite causing cutaneous hypersensitivity. However, there have been no systematic studies of ongoing activity during neuritis or non-inflammatory axonal transport disruption. In this study, we present the time course of ongoing activity from primary sensory neurons following neuritis and vinblastine-induced axonal transport disruption. Whereas 24% of C/slow Aδ-fiber neurons had ongoing activity during neuritis, few (disruption of axonal transport without inflammation does not lead to ongoing activity in sensory neurons, including nociceptors, but does cause a rapid and transient development of AMS. Since it is proposed that AMS underlies mechanically-induced radiating pain, and a transient disruption of axonal transport (as previously reported) leads to transient AMS, it follows that processes that disrupt axonal transport, such as neuritis, must persist to maintain AMS and the associated symptoms.

  18. Segregation of ipsilateral retinal ganglion cell axons at the optic chiasm requires the Shh receptor Boc. (United States)

    Fabre, Pierre J; Shimogori, Tomomi; Charron, Frédéric


    The pattern of contralaterally and ipsilaterally projecting retinal ganglion cell (RGC) axons at the optic chiasm is essential for the establishment of binocular vision. Contralateral axons cross the chiasm midline as they progress from the optic nerve to the optic tract. In contrast, ipsilateral axons deviate from the chiasm and continue in the ipsilateral optic tract, avoiding the chiasm midline. The molecular mechanism underlying this phenomenon is not completely understood. Here we show that the Sonic Hedgehog (Shh) receptor Boc is enriched in ipsilateral RGCs of the developing retina. Together with the presence of Shh at the midline, this complementary expression pattern led us to hypothesize that Shh might repel ipsilateral RGC axons at the chiasm. Consistent with this hypothesis, we found that only Boc-positive RGC axons retract in vitro in response to Shh and that this response is lost in Boc mutant RGCs. In vivo, we show that Boc is required for the normal segregation of ipsilateral axons at the optic chiasm and, conversely, that Boc expression in contralateral RGCs prevents their axons from crossing the optic chiasm. Together, these results suggest that Shh repels ipsilateral RGC axons at the optic chiasm via its receptor Boc. This work identifies a novel molecular pathway required for the segregation of axons at the optic chiasm.

  19. 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

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

    DEFF Research Database (Denmark)

    Moldovan, Mihai; Krarup, Christian


    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...

  1. Regeneration-associated macrophages: a novel approach to boost intrinsic regenerative capacity for axon regeneration

    Directory of Open Access Journals (Sweden)

    Min Jung Kwon


    Full Text Available Axons in central nervous system (CNS do not regenerate spontaneously after injuries such as stroke and traumatic spinal cord injury. Both intrinsic and extrinsic factors are responsible for the regeneration failure. Although intensive research efforts have been invested on extrinsic regeneration inhibitors, the extent to which glial inhibitors contribute to the regeneration failure in vivo still remains elusive. Recent experimental evidence has rekindled interests in intrinsic factors for the regulation of regeneration capacity in adult mammals. In this review, we propose that activating macrophages with pro-regenerative molecular signatures could be a novel approach for boosting intrinsic regenerative capacity of CNS neurons. Using a conditioning injury model in which regeneration of central branches of dorsal root ganglia sensory neurons is enhanced by a preceding injury to the peripheral branches, we have demonstrated that perineuronal macrophages surrounding dorsal root ganglia neurons are critically involved in the maintenance of enhanced regeneration capacity. Neuron-derived chemokine (C-C motif ligand 2 (CCL2 seems to mediate neuron-macrophage interactions conveying injury signals to perineuronal macrophages taking on a soley pro-regenerative phenotype, which we designate as regeneration-associated macrophages (RAMs. Manipulation of the CCL2 signaling could boost regeneration potential mimicking the conditioning injury, suggesting that the chemokine-mediated RAM activation could be utilized as a regenerative therapeutic strategy for CNS injuries.

  2. CNS repair and axon regeneration: Using genetic variation to determine mechanisms. (United States)

    Tedeschi, Andrea; Omura, Takao; Costigan, Michael


    The importance of genetic diversity in biological investigation has been recognized since the pioneering studies of Gregor Johann Mendel and Charles Darwin. Research in this area has been greatly informed recently by the publication of genomes from multiple species. Genes regulate and create every part and process in a living organism, react with the environment to create each living form and morph and mutate to determine the history and future of each species. The regenerative capacity of neurons differs profoundly between animal lineages and within the mammalian central and peripheral nervous systems. Here, we discuss research that suggests that genetic background contributes to the ability of injured axons to regenerate in the mammalian central nervous system (CNS), by controlling the regulation of specific signaling cascades. We detail the methods used to identify these pathways, which include among others Activin signaling and other TGF-β superfamily members. We discuss the potential of altering these pathways in patients with CNS damage and outline strategies to promote regeneration and repair by combinatorial manipulation of neuron-intrinsic and extrinsic determinants. Copyright © 2016 Elsevier Inc. All rights reserved.

  3. Mammalian motor neurons corelease glutamate and acetylcholine at central synapses

    DEFF Research Database (Denmark)

    Nishimaru, Hiroshi; Restrepo, Carlos Ernesto; Ryge, Jesper


    Motor neurons (MNs) are the principal neurons in the mammalian spinal cord whose activities cause muscles to contract. In addition to their peripheral axons, MNs have central collaterals that contact inhibitory Renshaw cells and other MNs. Since its original discovery > 60 years ago, it has been...

  4. Relationship of acute axonal damage, Wallerian degeneration, and clinical disability in multiple sclerosis. (United States)

    Singh, Shailender; Dallenga, Tobias; Winkler, Anne; Roemer, Shanu; Maruschak, Brigitte; Siebert, Heike; Brück, Wolfgang; Stadelmann, Christine


    Axonal damage and loss substantially contribute to the incremental accumulation of clinical disability in progressive multiple sclerosis. Here, we assessed the amount of Wallerian degeneration in brain tissue of multiple sclerosis patients in relation to demyelinating lesion activity and asked whether a transient blockade of Wallerian degeneration decreases axonal loss and clinical disability in a mouse model of inflammatory demyelination. Wallerian degeneration and acute axonal damage were determined immunohistochemically in the periplaque white matter of multiple sclerosis patients with early actively demyelinating lesions, chronic active lesions, and inactive lesions. Furthermore, we studied the effects of Wallerian degeneration blockage on clinical severity, inflammatory pathology, acute axonal damage, and long-term axonal loss in experimental autoimmune encephalomyelitis using Wallerian degeneration slow (Wld S ) mutant mice. The highest numbers of axons undergoing Wallerian degeneration were found in the perilesional white matter of multiple sclerosis patients early in the disease course and with actively demyelinating lesions. Furthermore, Wallerian degeneration was more abundant in patients harboring chronic active as compared to chronic inactive lesions. No co-localization of neuropeptide Y-Y1 receptor, a bona fide immunohistochemical marker of Wallerian degeneration, with amyloid precursor protein, frequently used as an indicator of acute axonal transport disturbance, was observed in human and mouse tissue, indicating distinct axon-degenerative processes. Experimentally, a delay of Wallerian degeneration, as observed in Wld S mice, did not result in a reduction of clinical disability or acute axonal damage in experimental autoimmune encephalomyelitis, further supporting that acute axonal damage as reflected by axonal transport disturbances does not share common molecular mechanisms with Wallerian degeneration. Furthermore, delaying Wallerian degeneration

  5. N-cadherin regulates primary motor axon growth and branching during zebrafish embryonic development. (United States)

    Brusés, Juan L


    N-cadherin is a classical type I cadherin that contributes to the formation of neural circuits by regulating growth cone migration and the formation of synaptic contacts. This study analyzed the role of N-cadherin in primary motor axons growth during development of the zebrafish (Danio rerio) embryo. After exiting the spinal cord, primary motor axons migrate ventrally through a common pathway and form the first neuromuscular junction with the muscle pioneer cells located at the horizontal myoseptum, which serves as a choice point for cell-type-specific pathway selection. Analysis of N-cadherin mutants (cdh2(hi3644Tg) ) and embryos injected with N-cadherin antisense morpholinos showed primary motor axons extending aberrant axonal branches at the choice point in ∼40% of the somitic hemisegments and an ∼150% increase in the number of branches per axon length within the ventral myotome. Analysis of individual axons trajectories showed that the caudal (CaP) and rostral (RoP) motor neurons axons formed aberrant branches at the choice point that abnormally extended in the rostrocaudal axis and ventrally to the horizontal myoseptum. Expression of a dominant-interfering N-cadherin cytoplasmic domain in primary motor neurons caused some axons to stall abnormally at the horizontal myoseptum and to impair their migration into the ventral myotome. However, in N-cadherin-depleted embryos, the majority of primary motor axons innervated their appropriate myotomal territories, indicating that N-cadherin regulates motor axon growth and branching without severely affecting the mechanisms that control axonal target selection. Copyright © 2011 Wiley-Liss, Inc.

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

    Directory of Open Access Journals (Sweden)

    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

  7. Pancreatic cancer genomes reveal aberrations in axon guidance pathway genes. (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


    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.

  8. Imaging findings in diffuse axonal injury after closed head trauma

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    Parizel, P.M.; Oezsarlak, Oe.; Goethem, J.W. van; Hauwe, L. van den; Schepper, A.M. de [Department of Radiology, Universitair Ziekenhuis Antwerpen (University of Antwerp), Edegem (Belgium); Dillen, C.; Cosyns, P. [Department of Psychiatry, Universitair Ziekenhuis Antwerpen (University of Antwerp), Edegem (Belgium); Verlooy, J. [Department of Neurosurgery, Universitair Ziekenhuis Antwerpen (University of Antwerp), Edegem (Belgium)


    Even in patients with closed head trauma, brain parenchyma can be severely injured due to disruption of axonal fibers by shearing forces during acceleration, deceleration, and rotation of the head. In this article we review the spectrum of imaging findings in patients with diffuse axonal injuries (DAI) after closed head trauma. Knowledge of the location and imaging characteristics of DAI is important to radiologists for detection and diagnosis. Common locations of DAI include: cerebral hemispheric gray-white matter interface and subcortical white matter, body and splenium of corpus callosum, basal ganglia, dorsolateral aspect of brainstem, and cerebellum. In the acute phase, CT may show punctate hemorrhages. The true extent of brain involvement is better appreciated with MR imaging, because both hemorrhagic and non-hemorrhagic lesions (gliotic scars) can be detected. The MR appearance of DAI lesions depends on several factors, including age of injury, presence of hemorrhage or blood-breakdown products (e. g., hemosiderin), and type of sequence used. Technical aspects in MR imaging of these patients are discussed. Non-hemorrhagic lesions can be detected with fluid attenuated inversion recovery (FLAIR), proton-density-, or T2-weighted images, whereas gradient echo sequences with long TE increase the visibility of old hemorrhagic lesions. (orig.) With 12 figs., 12 refs.

  9. Rapid signaling in distinct dopaminergic axons during locomotion and reward (United States)

    Howe, MW; Dombeck, DA


    Summary Dopaminergic projections from the midbrain to striatum are critical for motor control, as their degeneration in Parkinson’s disease results in profound movement deficits. Paradoxically, most recording methods report rapid phasic dopamine signaling (~100ms bursts) to unpredicted rewards, with little evidence for movement-related signaling. The leading model posits that phasic signaling in striatum targeting dopamine neurons drive reward-based learning, while slow variations in firing (tens of seconds to minutes) in these same neurons bias animals towards or away from movement. However, despite widespread acceptance of this model, current methods have provided little evidence to support or refute it. Here, using new optical recording methods, we report the discovery of rapid phasic signaling in striatum-targeting dopaminergic axons that was associated with, and capable of triggering, locomotion in mice. Axons expressing these signals were largely distinct from those signaling during unexpected rewards. These results suggest that dopaminergic neuromodulation can differentially impact motor control and reward learning with sub-second precision and suggest that both precise signal timing and neuronal subtype are important parameters to consider in the treatment of dopamine-related disorders. PMID:27398617

  10. Structure and Function of an Actin-Based Filter in the Proximal Axon

    Directory of Open Access Journals (Sweden)

    Varuzhan Balasanyan


    Full Text Available Summary: The essential organization of microtubules within neurons has been described; however, less is known about how neuronal actin is arranged and the functional implications of its arrangement. Here, we describe, in live cells, an actin-based structure in the proximal axon that selectively prevents some proteins from entering the axon while allowing the passage of others. Concentrated patches of actin in proximal axons are present shortly after axonal specification in rat and zebrafish neurons imaged live, and they mark positions where anterogradely traveling vesicles carrying dendritic proteins halt and reverse. Patches colocalize with the ARP2/3 complex, and when ARP2/3-mediated nucleation is blocked, a dendritic protein mislocalizes to the axon. Patches are highly dynamic, with few persisting longer than 30 min. In neurons in culture and in vivo, actin appears to form a contiguous, semipermeable barrier, despite its apparently sparse distribution, preventing axonal localization of constitutively active myosin Va but not myosin VI. : Balasanyan et al. find dynamic patches of actin in proximal axons of live neurons, mature and newly differentiated, in culture and in vivo. Patches contribute to a filter that sequesters some proteins within the somatodendritic domain while allowing others to pass into the axon, leading to polarized localization of proteins.

  11. Modeling of the axon membrane skeleton structure and implications for its mechanical properties.

    Directory of Open Access Journals (Sweden)

    Yihao Zhang


    Full Text Available Super-resolution microscopy recently revealed that, unlike the soma and dendrites, the axon membrane skeleton is structured as a series of actin rings connected by spectrin filaments that are held under tension. Currently, the structure-function relationship of the axonal structure is unclear. Here, we used atomic force microscopy (AFM to show that the stiffness of the axon plasma membrane is significantly higher than the stiffnesses of dendrites and somata. To examine whether the structure of the axon plasma membrane determines its overall stiffness, we introduced a coarse-grain molecular dynamics model of the axon membrane skeleton that reproduces the structure identified by super-resolution microscopy. Our proposed computational model accurately simulates the median value of the Young's modulus of the axon plasma membrane determined by atomic force microscopy. It also predicts that because the spectrin filaments are under entropic tension, the thermal random motion of the voltage-gated sodium channels (Nav, which are bound to ankyrin particles, a critical axonal protein, is reduced compared to the thermal motion when spectrin filaments are held at equilibrium. Lastly, our model predicts that because spectrin filaments are under tension, any axonal injuries that lacerate spectrin filaments will likely lead to a permanent disruption of the membrane skeleton due to the inability of spectrin filaments to spontaneously form their initial under-tension configuration.

  12. Axonal and presynaptic protein synthesis: new insights into the biology of the neuron

    NARCIS (Netherlands)

    Giuditta, A.; Kaplan, B.B.; van Minnen, J.; Alvarez, J.; Koenig, E.


    The presence of a local mRNA translation system in axons and terminals was proposed almost 40 years ago. Over the ensuing period, an impressive body of evidence has grown to support this proposal - yet the nerve cell body is still considered to be the only source of axonal and presynaptic proteins.

  13. Blast overpressure induced axonal injury changes in rat brainstem and spinal cord

    Directory of Open Access Journals (Sweden)

    Srinivasu Kallakuri


    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.

  14. Schwann Cell and Axon: An Interlaced Unit-From Action Potential to Phenotype Expression. (United States)

    Court, Felipe A; Alvarez, Jaime


    Here we propose a model of a peripheral axon with a great deal of autonomy from its cell body-the autonomous axon-but with a substantial dependence on its ensheathing Schwann cell (SC), the axon-SC unit. We review evidence in several fields and show that (i) axons can extend sprouts and grow without the concurrence of the cell body, but regulated by SCs; (ii) axons synthesize their proteins assisted by SCs that supply them with ribosomes and, probably, with mRNAs by way of exosomes; (iii) the molecular organization of the axoplasm, i.e., its phenotype, is regulated by the SC, as illustrated by the axonal microtubular content, which is down-regulated by the SC; and (iv) the axon has a program for self-destruction that is boosted by the SC. The main novelty of this model axon-SC unit is that it breaks with the notion that all proteins of the nerve cell are specified by its own nucleus. The notion of a collaborative specification of the axoplasm by more than one nucleus, which we present here, opens a new dimension in the understanding of the nervous system in health and disease and is also a frame of reference to understand other tissues or cell associations.

  15. Organophosphate-Related Alterations in Myelin and Axonal Transport in the Living Mammalian Brain (United States)


    510. Duncan JE, Goldstein LS. 2006. The Genetics of Axonal Transport and Axonal Transport Disorders PLoS Genet . 2(9): e124. 25 Duysen EG, Li...Gitajn L, Rea W, Yang Y, Stein EA.2007. Cocaine -induced brain activation detected by dynamic manganese-enhanced magnetic resonance imaging (MEMRI

  16. Misdirection and guidance of regenerating axons after experimental nerve injury and repair

    NARCIS (Netherlands)

    de Ruiter, Godard C W; Spinner, Robert J; Verhaagen, J.; Malessy, Martijn J A

    Misdirection of regenerating axons is one of the factors that can explain the limited results often found after nerve injury and repair. In the repair of mixed nerves innervating different distal targets (skin and muscle), misdirection may, for example, lead to motor axons projecting toward skin,

  17. Misdirection and guidance of regenerating axons after experimental nerve injury and repair A review

    NARCIS (Netherlands)

    Ruiter, G.C.W.; Spinner, R.J.; Verhaagen, J.; Malessay, M.J.A.


    Misdirection of regenerating axons is one of the factors that can explain the limited results often found after nerve injury and repair. In the repair of mixed nerves innervating different distal targets (skin and muscle), misdirection may, for example, lead to motor axons projecting toward skin,

  18. Misdirection and guidance of regenerating motor axons after experimental nerve injury and repair

    NARCIS (Netherlands)

    Ruiter, Godard de


    Misdirection of regenerating motor axons is one of the factors that can explain the disappointing recovery of function often observed after nerve injury and repair. In the first part of this thesis we quantified misdirection of motor axon regeneration after different types of nerve injury and repair

  19. Frizzled3 controls axonal polarity and intermediate target entry during striatal pathway development

    NARCIS (Netherlands)

    Morello, Francesca; Prasad, Asheeta A.; Rehberg, Kati; Baptista Vieira de Sá, Renata; Antón-Bolaños, Noelia; Leyva-Diaz, Eduardo; Adolfs, Youri; Tissir, Fadel; López-Bendito, Guillermina; Pasterkamp, R. Jeroen


    The striatum is a large brain nucleus with an important role in the control of movement and emotions.Mediumspiny neurons (MSNs) are striatal output neurons forming prominent descending axon tracts that target different brain nuclei. However, how MSN axon tracts in the forebrain develop remains

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

    Directory of Open Access Journals (Sweden)

    Pietro eBalbi


    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,, 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.

  1. Axonal remodeling in the corticospinal tract after stroke: how does rehabilitative training modulate it?

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    Naohiko Okabe


    Full Text Available Stroke causes long-term disability, and rehabilitative training is commonly used to improve the consecutive functional recovery. Following brain damage, surviving neurons undergo morphological alterations to reconstruct the remaining neural network. In the motor system, such neural network remodeling is observed as a motor map reorganization. Because of its significant correlation with functional recovery, motor map reorganization has been regarded as a key phenomenon for functional recovery after stroke. Although the mechanism underlying motor map reorganization remains unclear, increasing evidence has shown a critical role for axonal remodeling in the corticospinal tract. In this study, we review previous studies investigating axonal remodeling in the corticospinal tract after stroke and discuss which mechanisms may underlie the stimulatory effect of rehabilitative training. Axonal remodeling in the corticospinal tract can be classified into three types based on the location and the original targets of corticospinal neurons, and it seems that all the surviving corticospinal neurons in both ipsilesional and contralesional hemisphere can participate in axonal remodeling and motor map reorganization. Through axonal remodeling, corticospinal neurons alter their output selectivity from a single to multiple areas to compensate for the lost function. The remodeling of the corticospinal axon is influenced by the extent of tissue destruction and promoted by various therapeutic interventions, including rehabilitative training. Although the precise molecular mechanism underlying rehabilitation-promoted axonal remodeling remains elusive, previous data suggest that rehabilitative training promotes axonal remodeling by upregulating growth-promoting and downregulating growth-inhibiting signals.

  2. Neurobiology of axonal transport defects in motor neuron diseases: Opportunities for translational research? (United States)

    De Vos, Kurt J; Hafezparast, Majid


    Intracellular trafficking of cargoes is an essential process to maintain the structure and function of all mammalian cell types, but especially of neurons because of their extreme axon/dendrite polarisation. Axonal transport mediates the movement of cargoes such as proteins, mRNA, lipids, membrane-bound vesicles and organelles that are mostly synthesised in the cell body and in doing so is responsible for their correct spatiotemporal distribution in the axon, for example at specialised sites such as nodes of Ranvier and synaptic terminals. In addition, axonal transport maintains the essential long-distance communication between the cell body and synaptic terminals that allows neurons to react to their surroundings via trafficking of for example signalling endosomes. Axonal transport defects are a common observation in a variety of neurodegenerative diseases, and mutations in components of the axonal transport machinery have unequivocally shown that impaired axonal transport can cause neurodegeneration (reviewed in El-Kadi et al., 2007, De Vos et al., 2008; Millecamps and Julien, 2013). Here we review our current understanding of axonal transport defects and the role they play in motor neuron diseases (MNDs) with a specific focus on the most common form of MND, amyotrophic lateral sclerosis (ALS). Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.

  3. 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.


    Neuregulin-1 has a key role in mediating signaling between axons and Schwann cells during development. A limitation to studying its role in adulthood is the embryonic lethality of global Nrg1 gene deletion. We used the Cre-loxP system to generate transgenic mice in which neuregulin-1 is condition......Neuregulin-1 has a key role in mediating signaling between axons and Schwann cells during development. A limitation to studying its role in adulthood is the embryonic lethality of global Nrg1 gene deletion. We used the Cre-loxP system to generate transgenic mice in which neuregulin-1...... is conditionally ablated in the majority of small-diameter and a proportion of large-diameter sensory neurons that have axons conducting in the C- and Adelta-fiber range, respectively. Sensory neuron-specific neuregulin-1 ablation resulted in abnormally large Remak bundles with axons clustered in "polyaxonal...... cells required for normal sensory function. Sensory neuronal survival and axonal maintenance, however, are not dependent on axon-derived neuregulin-1 signaling in adulthood Udgivelsesdato: 2009/6/17...

  4. Intra-axonal Synthesis of SNAP25 Is Required for the Formation of Presynaptic Terminals

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    Andreia F.R. Batista


    Full Text Available Localized protein synthesis is a mechanism for developing axons to react acutely and in a spatially restricted manner to extracellular signals. As such, it is important for many aspects of axonal development, but its role in the formation of presynapses remains poorly understood. We found that the induced assembly of presynaptic terminals required local protein synthesis. Newly synthesized proteins were detectable at nascent presynapses within 15 min of inducing synapse formation in isolated axons. The transcript for the t-SNARE protein SNAP25, which is required for the fusion of synaptic vesicles with the plasma membrane, was recruited to presynaptic sites and locally translated. Inhibition of intra-axonal SNAP25 synthesis affected the clustering of SNAP25 and other presynaptic proteins and interfered with the release of synaptic vesicles from presynaptic sites. This study reveals a critical role for the axonal synthesis of SNAP25 in the assembly of presynaptic terminals.

  5. JMJD-1.2/PHF8 controls axon guidance by regulating Hedgehog-like signaling

    DEFF Research Database (Denmark)

    Riveiro, Alba; Mariani, Luca; Malmberg, Kim Emily


    Components of the KDM7 family of histone demethylases are implicated in neuronal development and one member, PHF8, is often found to be mutated in cases of X-linked mental retardation. However, how PHF8 regulates neurodevelopmental processes and contributes to the disease is still largely unknown...... the axonal defects. Deficiency of either wrt-8 or grl-16, or reduced expression of homologs of genes promoting Hedgehog signaling, restores correct axon guidance in jmjd-1.2 mutants. Genetic and overexpression data indicate that Hedgehog-related genes act on axon guidance through actin remodelers. Thus, our...... study highlights a novel function of jmjd-1.2 in axon guidance that might be relevant for the onset of X-linked mental retardation and provides compelling evidence of a conserved function of the Hedgehog pathway in C. elegans axon migration....

  6. Regulation of axon guidance by compartmentalized nonsense-mediated mRNA decay

    DEFF Research Database (Denmark)

    Colak, Dilek; Ji, Sheng-Jian; Porse, Bo T


    Growth cones enable axons to navigate toward their targets by responding to extracellular signaling molecules. Growth-cone responses are mediated in part by the local translation of axonal messenger RNAs (mRNAs). However, the mechanisms that regulate local translation are poorly understood. Here we...... show that Robo3.2, a receptor for the Slit family of guidance cues, is synthesized locally within axons of commissural neurons. Robo3.2 translation is induced by floor-plate-derived signals as axons cross the spinal cord midline. Robo3.2 is also a predicted target of the nonsense-mediated mRNA decay.......2 expression. These data show that local translation is regulated by mRNA stability and that NMD acts locally to influence axonal pathfinding....

  7. Axonal sprouting regulates myelin basic protein gene expression in denervated mouse hippocampus

    DEFF Research Database (Denmark)

    Jensen, M B; Poulsen, F R; Finsen, B


    to 35 days after transection of the entorhino-hippocampal perforant path axonal projection. In situ hybridization analysis showed that anterograde axonal and terminal degeneration lead to upregulated oligodendrocyte MBP mRNA expression starting between day 2 and day 4, in (1) the deep part of stratum...... axonal and terminal degeneration, myelin degenerative changes, microglial activation and axotomi-induced axonal sprouting. Oligodendrocyte MBP mRNA expression reached maximum in both these areas at day 7. MBP gene transcription remained constant in stratum radiatum, stratum pyramidale and stratum oriens...... of CA1, areas that were unaffected by perforant path transection. These results provide strong evidence that oligodendrocyte MBP gene expression can be regulated by axonal sprouting independently of microglial activation in the injured adult CNS....

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

    International Nuclear Information System (INIS)

    Curley, J Lowry; Catig, Gary C; Horn-Ranney, Elaine L; Moore, Michael J


    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)

  9. Activity-dependent myelination of parvalbumin interneurons mediated by axonal morphological plasticity. (United States)

    Stedehouder, J; Brizee, D; Shpak, G; Kushner, S A


    Axonal myelination of neocortical pyramidal neurons is dynamically modulated by neuronal activity. Recent studies have shown that a substantial proportion of neocortical myelin content is contributed by fast-spiking, parvalbumin (PV)-positive interneurons. However, it remains unknown whether the myelination of PV + interneurons is also modulated by intrinsic activity. Here, we utilized cell-type specific Designer Receptors Exclusively Activated by Designer Drugs (DREADDs) in adult male and female mice to activate a sparse population of medial prefrontal cortex PV + interneurons. Using single-cell axonal reconstructions, we find that DREADD-stimulated PV + interneurons exhibit a nearly two-fold increase in total length of myelination, predominantly mediated by a parallel increase of axonal arborization and number of internodes. In contrast, the distribution of axonal inter-branch segment distance and myelin internode length were not significantly altered. Topographical analysis revealed that myelination of DREADD-stimulated cells extended to higher axonal branch orders, while retaining a similar inter-branch distance threshold for myelination. Together, our results demonstrate that chemogenetically-induced neuronal activity increases the myelination of neocortical PV + interneurons mediated at least in part by an elaboration of their axonal morphology. SIGNIFICANCE STATEMENT Myelination is the wrapping of an axon in order to optimize conduction velocity in an energy-efficient manner. Previous studies have shown that myelination of neocortical pyramidal neurons is experience and activity-dependent. We now show that activity-dependent myelin plasticity in the adult neocortex extends to parvalbumin-expressing fast-spiking interneurons. Specifically, chemogenetic stimulation of parvalbumin interneurons in the medial prefrontal cortex significantly enhanced axonal myelination, which was paralleled by an increase in axonal arborization. This suggests that activity

  10. Axon Counts Yield Multiple Options for Triceps Fascicular Nerve to Axillary Nerve Transfer. (United States)

    Khair, M Michael; Schreiber, Joseph J; Rosenblatt, Lauren; Byun, David J; Lee, Steve K; Wolfe, Scott W


    To evaluate the relative axonal match between potential donor and recipient nerves, so that maximal reinnervation potential may be reached with the least chance of donor site morbidity. In 10 fresh-frozen cadaveric specimens, the main trunk and anterior, posterior, sensory and teres minor branches of the axillary nerve were identified, as were the radial nerve branches to the long, medial, and lateral heads of the triceps. The swing distances of the triceps fascicular nerve branches and the axillary nerve branches relative to the inferior border of the teres major muscle were recorded. Histomorphological analysis and axon counts were performed on sections of each branch. The median number of axons in the main axillary trunk was 7,887, with 4,052, 1,242, and 1,161 axons in the anterior, posterior, and teres minor branches, respectively. All specimens had a single long head triceps branch (median, 2,302 axons), a range of 1 to 3 branches to the medial head of the triceps (composite axon count, 2,198 axons), and 1 to 3 branches to the lateral head of the triceps (composite average, 1,462 axons). The medial and lateral head branches had sufficient swing distance to reach the anterior branch of the axillary nerve in all 10 specimens, with only 4 specimens having adequate long head branch swing distances. It is anatomically feasible to transfer multiple branches of the radial nerve supplying the medial, lateral, and sometimes, long head of the triceps to all branches of the axillary nerve in an attempt to reinnervate the deltoid and teres minor muscles. Understanding the axon counts of the different possible transfer combinations will improve operative flexibility and enable peripheral nerve surgeons to reinnervate for both abduction and external rotation with the highest donor/recipient axon count ratios. Copyright © 2016 American Society for Surgery of the Hand. Published by Elsevier Inc. All rights reserved.

  11. Dorsal column sensory axons degenerate due to impaired microvascular perfusion after spinal cord injury in rats (United States)

    Muradov, Johongir M.; Ewan, Eric E.; Hagg, Theo


    The mechanisms contributing to axon loss after spinal cord injury (SCI) are largely unknown but may involve microvascular loss as we have previously suggested. Here, we used a mild contusive injury (120 kdyn IH impactor) at T9 in rats focusing on ascending primary sensory dorsal column axons, anterogradely traced from the sciatic nerves. The injury caused a rapid and progressive loss of dorsal column microvasculature and oligodendrocytes at the injury site and penumbra and a ~70% loss of the sensory axons, by 24 hours. To model the microvascular loss, focal ischemia of the T9 dorsal columns was achieved via phototoxic activation of intravenously injected rose bengal. This caused an ~53% loss of sensory axons and an ~80% loss of dorsal column oligodendrocytes by 24 hours. Axon loss correlated with the extent and axial length of microvessel and oligodendrocyte loss along the dorsal column. To determine if oligodendrocyte loss contributes to axon loss, the glial toxin ethidium bromide (EB; 0.3 µg/µl) was microinjected into the T9 dorsal columns, and resulted in an ~88% loss of dorsal column oligodendrocytes and an ~56% loss of sensory axons after 72 hours. EB also caused an ~72% loss of microvessels. Lower concentrations of EB resulted in less axon, oligodendrocyte and microvessel loss, which were highly correlated (R2 = 0.81). These data suggest that focal spinal cord ischemia causes both oligodendrocyte and axon degeneration, which are perhaps linked. Importantly, they highlight the need of limiting the penumbral spread of ischemia and oligodendrocyte loss after SCI in order to protect axons. PMID:23978615


    Directory of Open Access Journals (Sweden)

    Saša Novak


    Full Text Available Pattern electroretinogram (PERG findings were analysed in 30 patients with central retinal vein occlusion. Latency and amplitude values of PERG waves were compared with the results obtained in 30 healthy individuals after sample randomisation. In 15 cases with „hemorrhagic type” occlusion of the central retinal vein significantly reduced N1-P1 wave amplitude was noted (0,369 mV, related to „exudative“ disease type (0,557 mV, as well as to the control group of examines (0,782 mV. PERG was described as the sensitive method and important indicator in damage assessment, ie. ischemia in the ganglional cell layer in central retinal vein occlusion. Ischemia increases anoxia, which influences not only the axons but also the enzymatic and transport processes within the cell bodies, dendrites, axons and axonal terminals. Slowing down of the fast phase of axoplasmatic transport in the axons in ischemic damage blocked transmission impulses which could be evident through different degrees of PERG wave amplitude reduction. With this method the patients can be selected in whom due to severe retinal ischemia there is the risk of neovascular glaucomma and maculopathy, which is the absolute indication for panlaser-photocoagulation.

  13. Reversible Axonal Dystrophy by Calcium Modulation in Frataxin-Deficient Sensory Neurons of YG8R Mice

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    Belén Mollá


    Full Text Available Friedreich’s ataxia (FRDA is a peripheral neuropathy involving a loss of proprioceptive sensory neurons. Studies of biopsies from patients suggest that axonal dysfunction precedes the death of proprioceptive neurons in a dying-back process. We observed that the deficiency of frataxin in sensory neurons of dorsal root ganglia (DRG of the YG8R mouse model causes the formation of axonal spheroids which retain dysfunctional mitochondria, shows alterations in the cytoskeleton and it produces impairment of axonal transport and autophagic flux. The homogenous distribution of axonal spheroids along the neurites supports the existence of continues focal damages. This lead us to propose for FRDA a model of distal axonopathy based on axonal focal damages. In addition, we observed the involvement of oxidative stress and dyshomeostasis of calcium in axonal spheroid formation generating axonal injury as a primary cause of pathophysiology. Axonal spheroids may be a consequence of calcium imbalance, thus we propose the quenching or removal extracellular Ca2+ to prevent spheroids formation. In our neuronal model, treatments with BAPTA and o-phenanthroline reverted the axonal dystrophy and the mitochondrial dysmorphic parameters. These results support the hypothesis that axonal pathology is reversible in FRDA by pharmacological manipulation of intracellular Ca2+ with Ca2+ chelators or metalloprotease inhibitors, preventing Ca2+-mediated axonal injury. Thus, the modulation of Ca2+ levels may be a relevant therapeutic target to develop early axonal protection and prevent dying-back neurodegeneration.

  14. A macroscopic model of traffic jams in axons. (United States)

    Kuznetsov, A V; Avramenko, A A


    The purpose of this paper is to develop a minimal macroscopic model capable of explaining the formation of traffic jams in fast axonal transport. The model accounts for the decrease of the number density of positively (and negatively) oriented microtubules near the location of the traffic jam due to formation of microtubule swirls; the model also accounts for the reduction of the effective velocity of organelle transport in the traffic jam region due to organelles falling off microtubule tracks more often in the swirl region. The model is based on molecular-motor-assisted transport equations and the hydrodynamic model of traffic jams in highway traffic. Parametric analyses of the model's predictions for various values of viscosity of the traffic flow, variance of the velocity distribution, diffusivity of microtubule-bound and free organelles, rate constants for binding to and detachment from microtubules, relaxation time, and average motor velocities of the retrograde and anterograde transport, are carried out.

  15. Neurogenetics of slow axonal transport: from cells to animals. (United States)

    Sadananda, Aparna; Ray, Krishanu


    Slow axonal transport is a multivariate phenomenon implicated in several neurodegenerative disorders. Recent reports have unraveled the molecular basis of the transport of certain slow component proteins, such as the neurofilament subunits, tubulin, and certain soluble enzymes such as Ca(2+)/calmodulin-dependent protein kinase IIa (CaM kinase IIa), etc., in tissue cultured neurons. In addition, genetic analyses also implicate microtubule-dependent motors and other housekeeping proteins in this process. However, the biological relevance of this phenomenon is not so well understood. Here, the authors have discussed the possibility of adopting neurogenetic analyses in multiple model organisms to correlate molecular level measurements of the slow transport phenomenon to animal behavior, thus facilitating the investigation of its biological efficacy.

  16. The axonal guidance receptor neogenin promotes acute inflammation.

    Directory of Open Access Journals (Sweden)

    Klemens König

    Full Text Available Neuronal guidance proteins (NGP were originally described in the context of axonal growth and migration. Yet recent work has demonstrated that NGPs also serve as guidance cues for immune competent cells. A crucial target receptor for NGPs during embryonic development is the neogenin receptor, however its role during acute inflammation is unknown. We report here that neogenin is abundantly expressed outside the nervous system and that animals with endogenous repression of neogenin (Neo1(-/- demonstrate attenuated changes of acute inflammation. Studies using functional inhibition of neogenin resulted in a significant attenuation of inflammatory peritonitis. In studies employing bone marrow chimeric animals we found the hematopoietic presence of Neo1(-/- to be responsible for the attenuated inflammatory response. Taken together our studies suggest that the guidance receptor neogenin holds crucial importance for the propagation of an acute inflammatory response and further define mechanisms shared between the nervous and the immune system.

  17. Video Object Tracking in Neural Axons with Fluorescence Microscopy Images

    Directory of Open Access Journals (Sweden)

    Liang Yuan


    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.

  18. Sodium Channel Nav1.8 Underlies TTX-Resistant Axonal Action Potential Conduction in Somatosensory C-Fibers of Distal Cutaneous Nerves. (United States)

    Klein, Amanda H; Vyshnevska, Alina; Hartke, Timothy V; De Col, Roberto; Mankowski, Joseph L; Turnquist, Brian; Bosmans, Frank; Reeh, Peter W; Schmelz, Martin; Carr, Richard W; Ringkamp, Matthias


    Voltage-gated sodium (Na V ) channels are responsible for the initiation and conduction of action potentials within primary afferents. The nine Na V channel isoforms recognized in mammals are often functionally divided into tetrodotoxin (TTX)-sensitive (TTX-s) channels (Na V 1.1-Na V 1.4, Na V 1.6-Na V 1.7) that are blocked by nanomolar concentrations and TTX-resistant (TTX-r) channels (Na V 1.8 and Na V 1.9) inhibited by millimolar concentrations, with Na V 1.5 having an intermediate toxin sensitivity. For small-diameter primary afferent neurons, it is unclear to what extent different Na V channel isoforms are distributed along the peripheral and central branches of their bifurcated axons. To determine the relative contribution of TTX-s and TTX-r channels to action potential conduction in different axonal compartments, we investigated the effects of TTX on C-fiber-mediated compound action potentials (C-CAPs) of proximal and distal peripheral nerve segments and dorsal roots from mice and pigtail monkeys ( Macaca nemestrina ). In the dorsal roots and proximal peripheral nerves of mice and nonhuman primates, TTX reduced the C-CAP amplitude to 16% of the baseline. In contrast, >30% of the C-CAP was resistant to TTX in distal peripheral branches of monkeys and WT and Na V 1.9 -/- mice. In nerves from Na V 1.8 -/- mice, TTX-r C-CAPs could not be detected. These data indicate that Na V 1.8 is the primary isoform underlying TTX-r conduction in distal axons of somatosensory C-fibers. Furthermore, there is a differential spatial distribution of Na V 1.8 within C-fiber axons, being functionally more prominent in the most distal axons and terminal regions. The enrichment of Na V 1.8 in distal axons may provide a useful target in the treatment of pain of peripheral origin. SIGNIFICANCE STATEMENT It is unclear whether individual sodium channel isoforms exert differential roles in action potential conduction along the axonal membrane of nociceptive, unmyelinated peripheral nerve

  19. Ephexin1 Is Required for Eph-Mediated Limb Trajectory of Spinal Motor Axons. (United States)

    Chang, Chih-Ju; Chang, Ming-Yuan; Chou, Szu-Yi; Huang, Chi-Chen; Chuang, Jian-Ying; Hsu, Tsung-I; Chang, Hsing-Fang; Wu, Yi-Hsin; Wu, Chung-Che; Morales, Daniel; Kania, Artur; Kao, Tzu-Jen


    The precise assembly of a functional nervous system relies on the guided migration of axonal growth cones, which is made possible by signals transmitted to the cytoskeleton by cell surface-expressed guidance receptors. We investigated the function of ephexin1, a Rho guanine nucleotide exchange factor, as an essential growth-cone guidance intermediary in the context of spinal lateral motor column (LMC) motor axon trajectory selection in the limb mesenchyme. Using in situ mRNA detection, we first show that ephexin1 is expressed in LMC neurons of chick and mouse embryos at the time of spinal motor axon extension into the limb. Ephexin1 loss of function and gain of function using in ovo electroporation in chick LMC neurons, of either sex, perturbed LMC axon trajectory selection, demonstrating an essential role of ephexin1 in motor axon guidance. In addition, ephexin1 loss in mice of either sex led to LMC axon trajectory selection errors. We also show that ephexin1 knockdown attenuates the growth preference of LMC neurites against ephrins in vitro and Eph receptor-mediated retargeting of LMC axons in vivo , suggesting that ephexin1 is required in Eph-mediated LMC motor axon guidance. Finally, both ephexin1 knockdown and ectopic expression of nonphosphorylatable ephexin1 mutant attenuated the retargeting of LMC axons caused by Src overexpression, implicating ephexin1 as an Src target in Eph signal relay in this context. In summary, our findings demonstrate that ephexin1 is essential for motor axon guidance and suggest an important role in relaying ephrin:Eph signals that mediate motor axon trajectory selection. SIGNIFICANCE STATEMENT The proper development of functioning neural circuits requires precise nerve connections among neurons or between neurons and their muscle targets. The Eph tyrosine kinase receptors expressed in neurons are important in many contexts during neural-circuit formation, such as axon outgrowth, axon guidance, and synaptic formation, and have been

  20. Neuron Morphology Influences Axon Initial Segment Plasticity123 (United States)


    In most vertebrate neurons, action potentials are initiated in the axon initial segment (AIS), a specialized region of the axon containing a high density of voltage-gated sodium and potassium channels. It has recently been proposed that neurons use plasticity of AIS length and/or location to regulate their intrinsic excitability. Here we quantify the impact of neuron morphology on AIS plasticity using computational models of simplified and realistic somatodendritic morphologies. In small neurons (e.g., dentate granule neurons), excitability was highest when the AIS was of intermediate length and located adjacent to the soma. Conversely, neurons having larger dendritic trees (e.g., pyramidal neurons) were most excitable when the AIS was longer and/or located away from the soma. For any given somatodendritic morphology, increasing dendritic membrane capacitance and/or conductance favored a longer and more distally located AIS. Overall, changes to AIS length, with corresponding changes in total sodium conductance, were far more effective in regulating neuron excitability than were changes in AIS location, while dendritic capacitance had a larger impact on AIS performance than did dendritic conductance. The somatodendritic influence on AIS performance reflects modest soma-to-AIS voltage attenuation combined with neuron size-dependent changes in AIS input resistance, effective membrane time constant, and isolation from somatodendritic capacitance. We conclude that the impact of AIS plasticity on neuron excitability will depend largely on somatodendritic morphology, and that, in some neurons, a shorter or more distally located AIS may promote, rather than limit, action potential generation. PMID:27022619

  1. Dynein is the motor for retrograde axonal transport of organelles

    International Nuclear Information System (INIS)

    Schnapp, B.J.; Reese, T.S.


    Vesicular organelles in axons of nerve cells are transported along microtubules either toward their plus ends (fast anterograde transport) or toward their minus ends (retrograde transport). Two microtubule-based motors were previously identified by examining plastic beads induced to move along microtubules by cytosol fractions from the squid giant axon: (i) an anterograde motor, kinesin, and (ii) a retrograde motor, which is characterized here. The retrograde motor, a cytosolic protein previously termed HMW1, was purified from optic lobes and extruded axoplasm by nucleotide-dependent microtubule affinity and release; microtubule gliding was used as the assay of motor activity. The following properties of the retrograde motor suggest that it is cytoplasmic dynein: (i) sedimentation at 20-22 S with a heavy chain of Mr greater than 200,000 that coelectrophoreses with the alpha and beta subunits of axonemal dynein, (ii) cleavage by UV irradiation in the presence of ATP and vanadate, and (iii) a molecular structure resembling two-headed dynein from axonemes. Furthermore, bead movement toward the minus end of microtubules was blocked when axoplasmic supernatants were treated with UV/vanadate. Treatment of axoplasmic supernatant with UV/vanadate also blocks the retrograde movement of purified organelles in vitro without changing the number of anterograde moving organelles, indicating that dynein interacts specifically with a subgroup of organelles programmed to move toward the cell body. However, purified optic lobe dynein, like purified kinesin, does not by itself promote the movement of purified organelles along microtubules, suggesting that additional axoplasmic factors are necessary for retrograde as well as anterograde transport

  2. Compensatory axon sprouting for very slow axonal die‐back in a transgenic model of spinal muscular atrophy type III (United States)

    Udina, Esther; Putman, Charles T.; Harris, Luke R.; Tyreman, Neil; Cook, Victoria E.


    Key points Smn +/− transgenic mouse is a model of the mildest form of spinal muscular atrophy.Although there is a loss of spinal motoneurons in 11‐month‐old animals, muscular force is maintained.This maintained muscular force is mediated by reinnervation of the denervated fibres by surviving motoneurons.The spinal motoneurons in these animals do not show an increased susceptibility to death after nerve injury and they retain their regenerative capacity.We conclude that the hypothesized immaturity of the neuromuscular system in this model cannot explain the loss of motoneurons by systematic die‐back. Abstract Spinal muscular atrophy (SMA) is a common autosomal recessive disorder in humans and is the leading genetic cause of infantile death. Patients lack the SMN1 gene with the severity of the disease depending on the number of copies of the highly homologous SMN2 gene. Although motoneuron death in the Smn +/− transgenic mouse model of the mildest form of SMA, SMA type III, has been reported, we have used retrograde tracing of sciatic and femoral motoneurons in the hindlimb with recording of muscle and motor unit isometric forces to count the number of motoneurons with intact neuromuscular connections. Thereby, we investigated whether incomplete maturation of the neuromuscular system induced by survival motoneuron protein (SMN) defects is responsible for die‐back of axons relative to survival of motoneurons. First, a reduction of ∼30% of backlabelled motoneurons began relatively late, at 11 months of age, with a significant loss of 19% at 7 months. Motor axon die‐back was affirmed by motor unit number estimation. Loss of functional motor units was fully compensated by axonal sprouting to retain normal contractile force in four hindlimb muscles (three fast‐twitch and one slow‐twitch) innervated by branches of the sciatic nerve. Second, our evaluation of whether axotomy of motoneurons in the adult Smn +/− transgenic mouse increases their

  3. Compensatory axon sprouting for very slow axonal die-back in a transgenic model of spinal muscular atrophy type III. (United States)

    Udina, Esther; Putman, Charles T; Harris, Luke R; Tyreman, Neil; Cook, Victoria E; Gordon, Tessa


    Smn +/- transgenic mouse is a model of the mildest form of spinal muscular atrophy. Although there is a loss of spinal motoneurons in 11-month-old animals, muscular force is maintained. This maintained muscular force is mediated by reinnervation of the denervated fibres by surviving motoneurons. The spinal motoneurons in these animals do not show an increased susceptibility to death after nerve injury and they retain their regenerative capacity. We conclude that the hypothesized immaturity of the neuromuscular system in this model cannot explain the loss of motoneurons by systematic die-back. Spinal muscular atrophy (SMA) is a common autosomal recessive disorder in humans and is the leading genetic cause of infantile death. Patients lack the SMN1 gene with the severity of the disease depending on the number of copies of the highly homologous SMN2 gene. Although motoneuron death in the Smn +/- transgenic mouse model of the mildest form of SMA, SMA type III, has been reported, we have used retrograde tracing of sciatic and femoral motoneurons in the hindlimb with recording of muscle and motor unit isometric forces to count the number of motoneurons with intact neuromuscular connections. Thereby, we investigated whether incomplete maturation of the neuromuscular system induced by survival motoneuron protein (SMN) defects is responsible for die-back of axons relative to survival of motoneurons. First, a reduction of ∼30% of backlabelled motoneurons began relatively late, at 11 months of age, with a significant loss of 19% at 7 months. Motor axon die-back was affirmed by motor unit number estimation. Loss of functional motor units was fully compensated by axonal sprouting to retain normal contractile force in four hindlimb muscles (three fast-twitch and one slow-twitch) innervated by branches of the sciatic nerve. Second, our evaluation of whether axotomy of motoneurons in the adult Smn +/- transgenic mouse increases their susceptibility to cell death demonstrated

  4. Functional Role of the Disulfide Isomerase ERp57 in Axonal Regeneration.

    Directory of Open Access Journals (Sweden)

    Valentina Castillo

    Full Text Available ERp57 (also known as grp58 and PDIA3 is a protein disulfide isomerase that catalyzes disulfide bonds formation of glycoproteins as part of the calnexin and calreticulin cycle. ERp57 is markedly upregulated in most common neurodegenerative diseases downstream of the endoplasmic reticulum (ER stress response. Despite accumulating correlative evidence supporting a neuroprotective role of ERp57, the contribution of this foldase to the physiology of the nervous system remains unknown. Here we developed a transgenic mouse model that overexpresses ERp57 in the nervous system under the control of the prion promoter. We analyzed the susceptibility of ERp57 transgenic mice to undergo neurodegeneration. Unexpectedly, ERp57 overexpression did not affect dopaminergic neuron loss and striatal denervation after injection of a Parkinson's disease-inducing neurotoxin. In sharp contrast, ERp57 transgenic animals presented enhanced locomotor recovery after mechanical injury to the sciatic nerve. These protective effects were associated with enhanced myelin removal, macrophage infiltration and axonal regeneration. Our results suggest that ERp57 specifically contributes to peripheral nerve regeneration, whereas its activity is dispensable for the survival of a specific neuronal population of the central nervous system. These results demonstrate for the first time a functional role of a component of the ER proteostasis network in peripheral nerve regeneration.

  5. CT features and clinical of diffuse axonal injury (with report of 41 cases)

    International Nuclear Information System (INIS)

    Zhang Yixing


    Objective: To evaluate CT imaging in the diagnosis of diffuse axonal injury (DAI) in correlation with the clinical manifestations. Methods: CT images and clinical data of 41 DAI cases were reviewed retrospectively, including 30 males and 11 females, 15 to 67 years old (average age was 30.5 years). According to the clinical features, all cases were classified into three groups: mild, moderate and severe injury. Results: In 10 cases of mild injury, the major CT findings were cerebral edema, slight cerebral hemorrhage in unilateral hemisphere or sub-arachnoid hemorrhage. Another 15 cases were classified as moderate injury: diffuse cerebral edema and hemorrhage in central brain gray matter were found on CT images. 16 cases with severe injury: severe diffuse cerebral edema accompanied with hemorrhage along the white-gray matter junction as well as epidural hematoma and/or subdural hematoma was demonstrated on CT images. Conclusion: CT scan is valuable in diagnosis of DAI and the anticipation of prognosis. (authors)

  6. Cadmium affects muscle type development and axon growth in zebrafish embryonic somitogenesis. (United States)

    Hen Chow, Elly Suk; Cheng, Shuk Han


    We have previously reported that exposure to cadmium during zebrafish embryonic development caused morphological malformations of organs and ectopic expression of genes involved in regulating developmental process. One of the most common developmental defects observed was altered axial curvature resulting from defects in the myotomes of the somites. In this study, we investigated the mechanisms of cadmium-induced toxicity in zebrafish somitogenesis. We showed that the critical period of exposure was the gastrulation period, which actually preceded the formation of the first morphologically distinct somites. The somites thus formed lost the typical chevron V-shape and are packed disorderly. The myogenic lineage commitment of the axial mesodermal cells was not affected, as the myogenic regulatory transcription factors were expressed normally. There were, however, losses of fast and slow muscle fibers in the myotomes. The innervation of the muscle blocks by spinal motoneurons is an important process of the somitogenesis. Both primary and secondary motoneurons appear to form normally while the axon growth is affected in cadmium-treated embryos. The notochord, which is essential in the patterning of the somites and the central nervous system, showed abnormal morphological features and failed to extend to the tail region. Taken together, it appears that cadmium exposure led to abnormal somite patterning of the muscle fibers and defects in axonogenesis.

  7. Stimulation of nicotinamide adenine dinucleotide biosynthetic pathways delays axonal degeneration after axotomy. (United States)

    Sasaki, Yo; Araki, Toshiyuki; Milbrandt, Jeffrey


    Axonal degeneration occurs in many neurodegenerative diseases and after traumatic injury and is a self-destructive program independent from programmed cell death. Previous studies demonstrated that overexpression of nicotinamide mononucleotide adenylyltransferase 1 (Nmnat1) or exogenous application of nicotinamide adenine dinucleotide (NAD) can protect axons of cultured dorsal root ganglion (DRG) neurons from degeneration caused by mechanical or neurotoxic injury. In mammalian cells, NAD can be synthesized from multiple precursors, including tryptophan, nicotinic acid, nicotinamide, and nicotinamide riboside (NmR), via multiple enzymatic steps. To determine whether other components of these NAD biosynthetic pathways are capable of delaying axonal degeneration, we overexpressed each of the enzymes involved in each pathway and/or exogenously administered their respective substrates in DRG cultures and assessed their capacity to protect axons after axotomy. Among the enzymes tested, Nmnat1 had the strongest protective effects, whereas nicotinamide phosphoribosyl transferase and nicotinic acid phosphoribosyl transferase showed moderate protective activity in the presence of their substrates. Strong axonal protection was also provided by Nmnat3, which is predominantly located in mitochondria, and an Nmnat1 mutant localized to the cytoplasm, indicating that the subcellular location of NAD production is not crucial for protective activity. In addition, we showed that exogenous application of the NAD precursors that are the substrates of these enzymes, including nicotinic acid mononucleotide, nicotinamide mononucleotide, and NmR, can also delay axonal degeneration. These results indicate that stimulation of NAD biosynthetic pathways via a variety of interventions may be useful in preventing or delaying axonal degeneration.

  8. Glia initiate brain assembly through non-canonical Chimaerin/Furin axon guidance in C. elegans (United States)

    Rapti, Georgia; Li, Chang; Shan, Alan; Lu, Yun; Shaham, Shai


    Brain assembly is hypothesized to begin when pioneer axons extend over non-neuronal cells, forming tracts guiding follower axons. Yet pioneer-neuron identities, their guidance substrates, and their interactions, are not well understood. Here, using time-lapse embryonic imaging, genetics, protein-interaction, and functional studies, we uncover the early events of C. elegans brain assembly. We demonstrate that C. elegans glia are key for assembly initiation, guiding pioneer and follower axons using distinct signals. Pioneer sublateral neurons, with unique growth properties, anatomy, and innervation, cooperate with glia to mediate follower-axon guidance. We further identify a CHIN-1/Chimaerin-KPC-1/Furin double mutant that severely disrupts assembly. CHIN-1/Chimaerin and KPC-1/Furin function non-canonically in glia and pioneer neurons for guidance-cue trafficking. We exploit this bottleneck to define roles for glial Netrin and Semaphorin in pioneer- and follower-axon guidance, respectively, and for glial and pioneer-neuron Flamingo/CELSR in follower-axon navigation. Altogether, our studies reveal previously-unknown glial roles in pioneer-axon guidance, suggesting conserved brain-assembly principles. PMID:28846083

  9. Expression of plasminogen activator inhibitor-1 by olfactory ensheathing glia promotes axonal regeneration. (United States)

    Simón, Diana; Martín-Bermejo, Maria Jesús; Gallego-Hernández, Maria Teresa; Pastrana, Erika; García-Escudero, Vega; García-Gómez, Ana; Lim, Filip; Díaz-Nido, Javier; Avila, Jesús; Moreno-Flores, Maria Teresa


    Olfactory ensheathing glia (OEG) cells are known to facilitate repair following axotomy of adult neurons, although the molecular mechanisms involved are not fully understood. We previously identified plasminogen activator inhibitor-1 (PAI-1), proteinase-activated receptor-1 (PAR-1), and thrombomodulin (TM) as candidates to regulate rat OEG-dependent axonal regeneration. In this study, we have validated the involvement of these proteins in promoting axonal regeneration by immortalized human OEGs. We studied the effect of silencing these proteins in OEGs on their capacity to promote the regeneration of severed adult retinal ganglion cells (RGCs) axons. Our results support the role of glial PAI-1 as a downstream effector of PAR-1 in promoting axon regeneration. In contrast, we found that TM inhibits OEG induced-axonal regeneration. We also assessed the signaling pathways downstream of PAR-1 that might modulate PAI-1 expression, observing that specifically inhibiting Gα(i), Rho kinase, or PLC and PKC downregulated the expression of PAI-1 in OEGs, with a concomitant reduction in OEG-dependent axon regeneration in adult RGCs. Our findings support an important role for the thrombin system in regulating adult axonal regeneration by OEGs. Copyright © 2011 Wiley-Liss, Inc.

  10. The Influence of Glutamate on Axonal Compound Action Potential In Vitro. (United States)

    Abouelela, Ahmed; Wieraszko, Andrzej


    Background  Our previous experiments demonstrated modulation of the amplitude of the axonal compound action potential (CAP) by electrical stimulation. To verify assumption that glutamate released from axons could be involved in this phenomenon, the modification of the axonal CAP induced by glutamate was investigated. Objectives  The major objective of this research is to verify the hypothesis that axonal activity would trigger the release of glutamate, which in turn would interact with specific axonal receptors modifying the amplitude of the action potential. Methods  Segments of the sciatic nerve were exposed to exogenous glutamate in vitro, and CAP was recorded before and after glutamate application. In some experiments, the release of radioactive glutamate analog from the sciatic nerve exposed to exogenous glutamate was also evaluated. Results  The glutamate-induced increase in CAP was blocked by different glutamate receptor antagonists. The effect of glutamate was not observed in Ca-free medium, and was blocked by antagonists of calcium channels. Exogenous glutamate, applied to the segments of sciatic nerve, induced the release of radioactive glutamate analog, demonstrating glutamate-induced glutamate release. Immunohistochemical examination revealed that axolemma contains components necessary for glutamatergic neurotransmission. Conclusion  The proteins of the axonal membrane can under the influence of electrical stimulation or exogenous glutamate change membrane permeability and ionic conductance, leading to a change in the amplitude of CAP. We suggest that increased axonal activity leads to the release of glutamate that results in changes in the amplitude of CAPs.

  11. Optogenetically enhanced axon regeneration: motor versus sensory neuron-specific stimulation. (United States)

    Ward, Patricia J; Clanton, Scott L; English, Arthur W


    Brief neuronal activation in injured peripheral nerves is both necessary and sufficient to enhance motor axon regeneration, and this effect is specific to the activated motoneurons. It is less clear whether sensory neurons respond in a similar manner to neuronal activation following peripheral axotomy. Further, it is unknown to what extent enhancement of axon regeneration with increased neuronal activity relies on a reflexive interaction within the spinal circuitry. We used mouse genetics and optical tools to evaluate the precision and selectivity of system-specific neuronal activation to enhance axon regeneration in a mixed nerve. We evaluated sensory and motor axon regeneration in two different mouse models expressing the light-sensitive cation channel, channelrhodopsin (ChR2). We selectively activated either sensory or motor axons using light stimulation combined with transection and repair of the sciatic nerve. Regardless of genotype, the number of ChR2-positive neurons whose axons had regenerated successfully was greater following system-specific optical treatment, with no effect on the number of ChR2-negative neurons (whether motor or sensory neurons). We conclude that acute system-specific neuronal activation is sufficient to enhance both motor and sensory axon regeneration. This regeneration-enhancing effect is likely cell autonomous. © 2018 Federation of European Neuroscience Societies and John Wiley & Sons Ltd.

  12. Modeling the mechanics of axonal fiber tracts using the embedded finite element method. (United States)

    Garimella, Harsha T; Kraft, Reuben H


    A subject-specific human head finite element model with embedded axonal fiber tractography obtained from diffusion tensor imaging was developed. The axonal fiber tractography finite element model was coupled with the volumetric elements in the head model using the embedded element method. This technique enables the calculation of axonal strains and real-time tracking of the mechanical response of the axonal fiber tracts. The coupled model was then verified using pressure and relative displacement-based (between skull and brain) experimental studies and was employed to analyze a head impact, demonstrating the applicability of this method in studying axonal injury. Following this, a comparison study of different injury criteria was performed. This model was used to determine the influence of impact direction on the extent of the axonal injury. The results suggested that the lateral impact loading is more dangerous compared to loading in the sagittal plane, a finding in agreement with previous studies. Through this analysis, we demonstrated the viability of the embedded element method as an alternative numerical approach for studying axonal injury in patient-specific human head models. Copyright © 2016 John Wiley & Sons, Ltd.

  13. Impaired JIP3-dependent axonal lysosome transport promotes amyloid plaque pathology. (United States)

    Gowrishankar, Swetha; Wu, Yumei; Ferguson, Shawn M


    Lysosomes robustly accumulate within axonal swellings at Alzheimer's disease (AD) amyloid plaques. However, the underlying mechanisms and disease relevance of such lysosome accumulations are not well understood. Motivated by these problems, we identified JNK-interacting protein 3 (JIP3) as an important regulator of axonal lysosome transport and maturation. JIP3 knockout mouse neuron primary cultures accumulate lysosomes within focal axonal swellings that resemble the dystrophic axons at amyloid plaques. These swellings contain high levels of amyloid precursor protein processing enzymes (BACE1 and presenilin 2) and are accompanied by elevated Aβ peptide levels. The in vivo importance of the JIP3-dependent regulation of axonal lysosomes was revealed by the worsening of the amyloid plaque pathology arising from JIP3 haploinsufficiency in a mouse model of AD. These results establish the critical role of JIP3-dependent axonal lysosome transport in regulating amyloidogenic amyloid precursor protein processing and support a model wherein Aβ production is amplified by plaque-induced axonal lysosome transport defects. © 2017 Gowrishankar et al.

  14. Non-nuclear Pool of Splicing Factor SFPQ Regulates Axonal Transcripts Required for Normal Motor Development. (United States)

    Thomas-Jinu, Swapna; Gordon, Patricia M; Fielding, Triona; Taylor, Richard; Smith, Bradley N; Snowden, Victoria; Blanc, Eric; Vance, Caroline; Topp, Simon; Wong, Chun-Hao; Bielen, Holger; Williams, Kelly L; McCann, Emily P; Nicholson, Garth A; Pan-Vazquez, Alejandro; Fox, Archa H; Bond, Charles S; Talbot, William S; Blair, Ian P; Shaw, Christopher E; Houart, Corinne


    Recent progress revealed the complexity of RNA processing and its association to human disorders. Here, we unveil a new facet of this complexity. Complete loss of function of the ubiquitous splicing factor SFPQ affects zebrafish motoneuron differentiation cell autonomously. In addition to its nuclear localization, the protein unexpectedly localizes to motor axons. The cytosolic version of SFPQ abolishes motor axonal defects, rescuing key transcripts, and restores motility in the paralyzed sfpq null mutants, indicating a non-nuclear processing role in motor axons. Novel variants affecting the conserved coiled-coil domain, so far exclusively found in fALS exomes, specifically affect the ability of SFPQ to localize in axons. They broadly rescue morphology and motility in the zebrafish mutant, but alter motor axon morphology, demonstrating functional requirement for axonal SFPQ. Altogether, we uncover the axonal function of the splicing factor SFPQ in motor development and highlight the importance of the coiled-coil domain in this process. VIDEO ABSTRACT. Copyright © 2017 The Author(s). Published by Elsevier Inc. All rights reserved.

  15. The Drosophila HEM-2/NAP1 homolog KETTE controls axonal pathfinding and cytoskeletal organization. (United States)

    Hummel, T; Leifker, K; Klämbt, C


    In Drosophila, the correct formation of the segmental commissures depends on neuron-glial interactions at the midline. The VUM midline neurons extend axons along which glial cells migrate in between anterior and posterior commissures. Here, we show that the gene kette is required for the normal projection of the VUM axons and subsequently disrupts glial migration. Axonal projection defects are also found for many other moto- and interneurons. In addition, kette affects the cell morphology of mesodermal and epidermal derivatives, which show an abnormal actin cytoskeleton. The KETTE protein is homologous to the transmembrane protein HEM-2/NAP1 evolutionary conserved from worms to vertebrates. In vitro analysis has shown a specific interaction of the vertebrate HEM-2/NAP1 with the SH2-SH3 adapter protein NCK and the small GTPase RAC1, which both have been implicated in regulating cytoskeleton organization and axonal growth. Hypomorphic kette mutations lead to axonal defects similar to mutations in the Drosophila NCK homolog dreadlocks. Furthermore, we show that kette and dock mutants genetically interact. NCK is thought to interact with the small G proteins RAC1 and CDC42, which play a role in axonal growth. In line with these observations, a kette phenocopy can be obtained following directed expression of mutant DCDC42 or DRAC1 in the CNS midline. In addition, the kette mutant phenotype can be partially rescued by expression of an activated DRAC1 transgene. Our data suggest an important role of the HEM-2 protein in cytoskeletal organization during axonal pathfinding.

  16. GDF10 Is a Signal for Axonal Sprouting and Functional Recovery after Stroke (United States)

    Li, S; Nie, EH; Yin, Y; Benowitz, LI; Tung, S; Vinters, HV; Bahjat, FR; Stenzel-Poore, MP; Kawaguchi, R; Coppola, G; Carmichael, ST


    Stroke produces a limited process of neural repair. Axonal sprouting in cortex adjacent to the infarct is part of this recovery process, but the signal that initiates axonal sprouting is not known. Growth and Differentiation Factor 10 (GDF10) is induced in peri-infarct neurons in mouse, non-human primate and human. GDF10 promotes axonal outgrowth in vitro in mouse, rat and human neurons through TGFβRI/II signaling. Using pharmacogenetic gain and loss of function studies, GDF10 produces axonal sprouting and enhanced functional recovery after stroke; knocking down GDF10 blocks axonal sprouting and reduces recovery. RNA-seq from peri-infarct cortical neurons indicates that GDF10 downregulates PTEN and upregulates PI3 kinase signaling and induces specific axonal guidance molecules. Unsupervised genome-wide association analysis of the GDF10 transcriptome shows that it is not related to neurodevelopment but may partially overlap with other CNS injury patterns. GDF10 is a stroke-induced signal for axonal sprouting and functional recovery. PMID:26502261

  17. The Mesoaccumbens Pathway: A Retrograde Labeling and Single-Cell Axon Tracing Analysis in the Mouse. (United States)

    Rodríguez-López, Claudia; Clascá, Francisco; Prensa, Lucía


    Neurons in the ventral tegmental area (VTA) that innervate the nucleus accumbens (Acb) constitute the so-called mesoaccumbens system. Increased activity by these neurons is correlated with the expectation and achievement of reward. The mesoaccumbens projection neurons are regarded as a central node in the brain networks that regulate drive and hedonic experience, and their dysregulation is a common pathophysiological step in addictive behaviors as well as major depression. Despite previous anatomical studies that have analyzed the origin of the mesoaccumbens axons within the VTA, regarded as a unit, the exact contributions of the various cytoarchitectural subdivisions of the VTA to this innervation is still unexplored; understanding these contributions would help further our understanding of their precise anatomical organization. With the aim of deciphering the contribution of the various VTA subdivisions to accumbal innervation, the present study has used retrograde tracer microinjections in the Acb to map the location within the various VTA subdivisions of neurons targeting either the shell or core compartments of the Acb in mice. Furthermore, the dopaminergic nature of these projections has also been analyzed using tyrosine-hydroxylase immunohistochemistry. We demonstrate here that small territories of the Acb core and shell are innervated simultaneously by many VTA subdivisions, contributing dopaminergic as well as non-dopaminergic axons to the accumbal innervation. In fact, single VTA subdivisions harbor both dopaminergic and non-dopaminergic neurons that project to the same accumbal territory. The most medial VTA subnuclei, like the caudal linear nucleus, project abundantly to medial aspects of the Acb core, whereas more lateral territories of the Acb are preferentially targeted by neurons located in the parabrachial pigmented and paranigral nuclei. Overall, about half of the mesoaccumbens neurons are putatively dopaminergic in mice. Anterograde single

  18. The Microtubule Regulatory Protein Stathmin Is Required to Maintain the Integrity of Axonal Microtubules in Drosophila.

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    Jason E Duncan

    Full Text Available Axonal transport, a form of long-distance, bi-directional intracellular transport that occurs between the cell body and synaptic terminal, is critical in maintaining the function and viability of neurons. We have identified a requirement for the stathmin (stai gene in the maintenance of axonal microtubules and regulation of axonal transport in Drosophila. The stai gene encodes a cytosolic phosphoprotein that regulates microtubule dynamics by partitioning tubulin dimers between pools of soluble tubulin and polymerized microtubules, and by directly binding to microtubules and promoting depolymerization. Analysis of stai function in Drosophila, which has a single stai gene, circumvents potential complications with studies performed in vertebrate systems in which mutant phenotypes may be compensated by genetic redundancy of other members of the stai gene family. This has allowed us to identify an essential function for stai in the maintenance of the integrity of axonal microtubules. In addition to the severe disruption in the abundance and architecture of microtubules in the axons of stai mutant Drosophila, we also observe additional neurological phenotypes associated with loss of stai function including a posterior paralysis and tail-flip phenotype in third instar larvae, aberrant accumulation of transported membranous organelles in stai deficient axons, a progressive bang-sensitive response to mechanical stimulation reminiscent of the class of Drosophila mutants used to model human epileptic seizures, and a reduced adult lifespan. Reductions in the levels of Kinesin-1, the primary anterograde motor in axonal transport, enhance these phenotypes. Collectively, our results indicate that stai has an important role in neuronal function, likely through the maintenance of microtubule integrity in the axons of nerves of the peripheral nervous system necessary to support and sustain long-distance axonal transport.

  19. The Microtubule Regulatory Protein Stathmin Is Required to Maintain the Integrity of Axonal Microtubules in Drosophila (United States)

    Duncan, Jason E.; Lytle, Nikki K.; Zuniga, Alfredo; Goldstein, Lawrence S. B.


    Axonal transport, a form of long-distance, bi-directional intracellular transport that occurs between the cell body and synaptic terminal, is critical in maintaining the function and viability of neurons. We have identified a requirement for the stathmin (stai) gene in the maintenance of axonal microtubules and regulation of axonal transport in Drosophila . The stai gene encodes a cytosolic phosphoprotein that regulates microtubule dynamics by partitioning tubulin dimers between pools of soluble tubulin and polymerized microtubules, and by directly binding to microtubules and promoting depolymerization. Analysis of stai function in Drosophila , which has a single stai gene, circumvents potential complications with studies performed in vertebrate systems in which mutant phenotypes may be compensated by genetic redundancy of other members of the stai gene family. This has allowed us to identify an essential function for stai in the maintenance of the integrity of axonal microtubules. In addition to the severe disruption in the abundance and architecture of microtubules in the axons of stai mutant Drosophila , we also observe additional neurological phenotypes associated with loss of stai function including a posterior paralysis and tail-flip phenotype in third instar larvae, aberrant accumulation of transported membranous organelles in stai deficient axons, a progressive bang-sensitive response to mechanical stimulation reminiscent of the class of Drosophila mutants used to model human epileptic seizures, and a reduced adult lifespan. Reductions in the levels of Kinesin-1, the primary anterograde motor in axonal transport, enhance these phenotypes. Collectively, our results indicate that stai has an important role in neuronal function, likely through the maintenance of microtubule integrity in the axons of nerves of the peripheral nervous system necessary to support and sustain long-distance axonal transport. PMID:23840848

  20. Current Opportunities for Clinical Monitoring of Axonal Pathology in Traumatic Brain Injury

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    Parmenion P. Tsitsopoulos


    Full Text Available Traumatic brain injury (TBI is a multidimensional and highly complex disease commonly resulting in widespread injury to axons, due to rapid inertial acceleration/deceleration forces transmitted to the brain during impact. Axonal injury leads to brain network dysfunction, significantly contributing to cognitive and functional impairments frequently observed in TBI survivors. Diffuse axonal injury (DAI is a clinical entity suggested by impaired level of consciousness and coma on clinical examination and characterized by widespread injury to the hemispheric white matter tracts, the corpus callosum and the brain stem. The clinical course of DAI is commonly unpredictable and it remains a challenging entity with limited therapeutic options, to date. Although axonal integrity may be disrupted at impact, the majority of axonal pathology evolves over time, resulting from delayed activation of complex intracellular biochemical cascades. Activation of these secondary biochemical pathways may lead to axonal transection, named secondary axotomy, and be responsible for the clinical decline of DAI patients. Advances in the neurocritical care of TBI patients have been achieved by refinements in multimodality monitoring for prevention and early detection of secondary injury factors, which can be applied also to DAI. There is an emerging role for biomarkers in blood, cerebrospinal fluid, and interstitial fluid using microdialysis in the evaluation of axonal injury in TBI. These biomarker studies have assessed various axonal and neuroglial markers as well as inflammatory mediators, such as cytokines and chemokines. Moreover, modern neuroimaging can detect subtle or overt DAI/white matter changes in diffuse TBI patients across all injury severities using magnetic resonance spectroscopy, diffusion tensor imaging, and positron emission tomography. Importantly, serial neuroimaging studies provide evidence for evolving axonal injury. Since axonal injury may be a key

  1. Axonal degeneration stimulates the formation of NG2+ cells and oligodendrocytes in the mouse

    DEFF Research Database (Denmark)

    Nielsen, Helle Hvilsted; Ladeby, Rune; Drøjdahl, Nina


    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...

  2. An Atypical SCF-like Ubiquitin Ligase Complex Promotes Wallerian Degeneration through Regulation of Axonal Nmnat2

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    Yuya Yamagishi


    Full Text Available Axon degeneration is a tightly regulated, self-destructive program that is a critical feature of many neurodegenerative diseases, but the molecular mechanisms regulating this program remain poorly understood. Here, we identify S-phase kinase-associated protein 1A (Skp1a, a core component of a Skp/Cullin/F-box (SCF-type E3 ubiquitin ligase complex, as a critical regulator of axon degeneration after injury in mammalian neurons. Depletion of Skp1a prolongs survival of injured axons in vitro and in the optic nerve in vivo. We demonstrate that Skp1a regulates the protein level of the nicotinamide adenine dinucleotide (NAD+ synthesizing enzyme nicotinamide mononucleotide adenylyltransferase 2 (Nmnat2 in axons. Loss of axonal Nmnat2 contributes to a local ATP deficit that triggers axon degeneration. Knockdown of Skp1a elevates basal levels of axonal Nmnat2, thereby delaying axon degeneration through prolonged maintenance of axonal ATP. Consistent with Skp1a functioning through regulation of Nmnat2, Skp1a knockdown fails to protect axons from Nmnat2 knockdown. These results illuminate the molecular mechanism underlying Skp1a-dependent axonal destruction.

  3. Guidance of Drosophila Mushroom Body Axons Depends upon DRL-Wnt Receptor Cleavage in the Brain Dorsomedial Lineage Precursors

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    Elodie Reynaud


    Full Text Available In vivo axon pathfinding mechanisms in the neuron-dense brain remain relatively poorly characterized. We study the Drosophila mushroom body (MB axons, whose α and β branches connect to different brain areas. We show that the Ryk family WNT5 receptor, DRL (derailed, which is expressed in the dorsomedial lineages, brain structure precursors adjacent to the MBs, is required for MB α branch axon guidance. DRL acts to capture and present WNT5 to MB axons rather than transduce a WNT5 signal. DRL’s ectodomain must be cleaved and shed to guide α axons. DRL-2, another Ryk, is expressed within MB axons and functions as a repulsive WNT5 signaling receptor. Finally, our biochemical data support the existence of a ternary complex composed of the cleaved DRL ectodomain, WNT5, and DRL-2. Thus, the interaction of MB-extrinsic and -intrinsic Ryks via their common ligand acts to guide MB α axons.

  4. Sorting of cargos between axons and dendrites: modelling of differences in cargo transport in these two types of neurites. (United States)

    Kuznetsov, A V


    Explaining how intracellular cargos are sorted between axons and dendrites is important for a mechanistic understanding of what happens in many neurodegenerative disorders. A simple model of cargo sorting relies on differences in microtubule (MT) orientation between axons and dendrites: in mammalian neurons all MTs in axons have their plus ends directed outward while in proximal regions of dendrites the MT polarity is mixed. It can therefore be assumed that cargos that need to be driven into axons associate with kinesin motors while cargos that need to be driven into dendrites associate with dynein motors. This paper develops equations of cargo transport in axons and dendrites based on the above assumptions. Propagation of a pulse of radiolabelled cargos entering an axon and dendrite is simulated. The model equations are solved utilising the Laplace transform method. Differences in cargo transport between axons and dendrites are discussed.

  5. Myosin-V Induces Cargo Immobilization and Clustering at the Axon Initial Segment

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    Anne F. J. Janssen


    Full Text Available The selective transport of different cargoes into axons and dendrites underlies the polarized organization of the neuron. Although it has become clear that the combined activity of different motors determines the destination and selectivity of transport, little is known about the mechanistic details of motor cooperation. For example, the exact role of myosin-V in opposing microtubule-based axon entries has remained unclear. Here we use two orthogonal chemically-induced heterodimerization systems to independently recruit different motors to cargoes. We find that recruiting myosin-V to kinesin-propelled cargoes at approximately equal numbers is sufficient to stall motility. Kinesin-driven cargoes entering the axon were arrested in the axon initial segment (AIS upon myosin-V recruitment and accumulated in distinct actin-rich hotspots. Importantly, unlike proposed previously, myosin-V did not return these cargoes to the cell body, suggesting that additional mechanism are required to establish cargo retrieval from the AIS.

  6. Islet Coordinately Regulates Motor Axon Guidance and Dendrite Targeting through the Frazzled/DCC Receptor

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    Celine Santiago


    Full Text Available Motor neuron axon targeting in the periphery is correlated with the positions of motor neuron inputs in the CNS, but how these processes are coordinated to form a myotopic map remains poorly understood. We show that the LIM homeodomain factor Islet (Isl controls targeting of both axons and dendrites in Drosophila motor neurons through regulation of the Frazzled (Fra/DCC receptor. Isl is required for fra expression in ventrally projecting motor neurons, and isl and fra mutants have similar axon guidance defects. Single-cell labeling indicates that isl and fra are also required for dendrite targeting in a subset of motor neurons. Finally, overexpression of Fra rescues axon and dendrite targeting defects in isl mutants. These results indicate that Fra acts downstream of Isl in both the periphery and the CNS, demonstrating how a single regulatory relationship is used in multiple cellular compartments to coordinate neural circuit wiring.

  7. Vertebrate Fidgetin Restrains Axonal Growth by Severing Labile Domains of Microtubules

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    Lanfranco Leo


    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.

  8. Progress of Research on Diffuse Axonal Injury after Traumatic Brain Injury

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    Junwei Ma


    Full Text Available The current work reviews the concept, pathological mechanism, and process of diagnosing of DAI. The pathological mechanism underlying DAI is complicated, including axonal breakage caused by axonal retraction balls, discontinued protein transport along the axonal axis, calcium influx, and calpain-mediated hydrolysis of structural protein, degradation of axonal cytoskeleton network, the changes of transport proteins such as amyloid precursor protein, and changes of glia cells. Based on the above pathological mechanism, the diagnosis of DAI is usually made using methods such as CT, traditional and new MRI, biochemical markers, and neuropsychological assessment. This review provides a basis in literature for further investigation and discusses the pathological mechanism. It may also facilitate improvement of the accuracy of diagnosis for DAI, which may come to play a critical role in breaking through the bottleneck of the clinical treatment of DAI and improving the survival and quality of life of patients through clear understanding of pathological mechanisms and accurate diagnosis.

  9. Lithium Enhances Axonal Regeneration in Peripheral Nerve by Inhibiting Glycogen Synthase Kinase 3β Activation

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    Huanxing Su


    Full Text Available Brachial plexus injury often involves traumatic root avulsion resulting in permanent paralysis of the innervated muscles. The lack of sufficient regeneration from spinal motoneurons to the peripheral nerve (PN is considered to be one of the major causes of the unsatisfactory outcome of various surgical interventions for repair of the devastating injury. The present study was undertaken to investigate potential inhibitory signals which influence axonal regeneration after root avulsion injury. The results of the study showed that root avulsion triggered GSK-3β activation in the injured motoneurons and remaining axons in the ventral funiculus. Systemic application of a clinical dose of lithium suppressed activated GSK-3β in the lesioned spinal cord to the normal level and induced extensive axonal regeneration into replanted ventral roots. Our study suggests that GSK-3β activity is involved in negative regulation for axonal elongation and regeneration and lithium, the specific GSK-3β inhibitor, enhances motoneuron regeneration from CNS to PNS.

  10. Phosphatidylserine improves axonal transport by inhibition of HDAC and has potential in treatment of neurodegenerative diseases

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    Shiran Naftelberg


    Full Text Available Familial dysautonomia (FD is a rare children neurodegenerative disease caused due to a point mutation in the IKBKAP gene that results in decreased IKK complex-associated protein (IKAP protein production. The disease affects mostly the dorsal root ganglion (DRG and the sympathetic ganglion. Recently, we found that the molecular mechanisms underlying neurodegeneration in FD patients are defects in axonal transport of nerve growth factors and microtubule stability in the DRG. Neurons are highly polarized cells with very long axons. In order to survive and maintain proper function, neurons depend on transport of proteins and other cellular components from the neuronal body along the axons. We further demonstrated that IKAP is necessary for axon maintenance and showed that phosphatidylserine acts as an HDAC6 inhibitor to rescue neuronal function in FD cells. In this review, we will highlight our latest research findings.

  11. Precise Somatotopic Thalamocortical Axon Guidance Depends on LPA-Mediated PRG-2/Radixin Signaling

    DEFF Research Database (Denmark)

    Cheng, Jin; Sahani, Sadhna; Hausrat, Torben Johann


    Precise connection of thalamic barreloids with their corresponding cortical barrels is critical for processing of vibrissal sensory information. Here, we show that PRG-2, a phospholipid-interacting molecule, is important for thalamocortical axon guidance. Developing thalamocortical fibers both in...

  12. Low frequency oscillating gradient spin-echo sequences improve sensitivity to axon diameter: An experimental study in viable nerve tissue. (United States)

    Kakkar, Lebina S; Bennett, Oscar F; Siow, Bernard; Richardson, Simon; Ianuş, Andrada; Quick, Tom; Atkinson, David; Phillips, James B; Drobnjak, Ivana


    Mapping axon diameters within the central and peripheral nervous system could play an important role in our understanding of nerve pathways, and help diagnose and monitor an array of neurological disorders. Numerous diffusion MRI methods have been proposed for imaging axon diameters, most of which use conventional single diffusion encoding (SDE) spin echo sequences. However, a growing number of studies show that oscillating gradient spin echo (OGSE) sequences can provide additional advantages over conventional SDE sequences. Recent theoretical results suggest that this is especially the case in realistic scenarios, such as when fibres have unknown or dispersed orientation. In the present study, we adopt the ActiveAx approach to experimentally investigate the extent of these advantages by comparing the performances of SDE and trapezoidal OGSE in viable nerve tissue. We optimise SDE and OGSE ActiveAx protocols for a rat peripheral nerve tissue and test their performance using Monte Carlo simulations and a 800 mT/m gradient strength pre-clinical imaging experiment. The imaging experiment uses excised sciatic nerve from a rat's leg placed in a MRI compatible viable isolated tissue (VIT) maintenance chamber, which keeps the tissue in a viable physiological state that preserves the structural complexity of the nerve and enables lengthy scan times. We compare model estimates to histology, which we perform on the nerve post scanning. Optimisation produces a three-shell SDE and OGSE ActiveAx protocol, with the OGSE protocol consisting of one SDE sequence and two low-frequency oscillating gradient waveform sequences. Both simulation and imaging results show that the OGSE ActiveAx estimates of the axon diameter index have a higher accuracy and a higher precision compared to those from SDE. Histology estimates of the axon diameter index in our nerve tissue samples are 4-5.8 μm and these are excellently matched with the OGSE estimates 4.2-6.5 μm, while SDE overestimates at

  13. Tormenta simpática paroxística siguiendo a injuria Axonal difusa Paroxysmal sympathetic storm after diffuse axonal head injury


    Pablo Young; Barbara C. Finn; Debora Pellegrini; Elias D. Soloaga; Julio E. Bruetman


    El término tormenta simpática paroxística se utiliza como sinónimo de alteraciones episódicas de la temperatura corporal, la presión arterial, la frecuencia respiratoria y cardíaca, el tamaño pupilar y el nivel de conciencia, que coinciden con hiperhidrosis, salivación excesiva y postura extensora. Esto siempre en el contexto de una injuria axonal difusa grave que sigue a un traumatismo encéfalo-craneano (TEC) grave. Presentamos dos pacientes jóvenes con injuria axonal difusa secundaria a TEC...

  14. Chondroitin sulfate proteoglycans negatively regulate the positioning of mitochondria and endoplasmic reticulum to distal axons. (United States)

    Sainath, Rajiv; Armijo-Weingart, Lorena; Ketscheck, Andrea; Xu, Zhuxuan; Li, Shuxin; Gallo, Gianluca


    Chondroitin sulfate proteoglycans (CSPGs) are components of the extracellular matrix that inhibit the extension and regeneration of axons. However, the underlying mechanism of action remains poorly understood. Mitochondria and endoplasmic reticulum (ER) are functionally inter-linked organelles important to axon development and maintenance. We report that CSPGs impair the targeting of mitochondria and ER to the growth cones of chicken embryonic sensory axons. The effect of CSPGs on the targeting of mitochondria is blocked by inhibition of the LAR receptor for CSPGs. The regulation of the targeting of mitochondria and ER to the growth cone by CSPGs is due to attenuation of PI3K signaling, which is known to be downstream of LAR receptor activation. Dynactin is a required component of the dynein motor complex that drives the normally occurring retrograde evacuation of mitochondria from growth cones. CSPGs elevate the levels of p150 Glu dynactin found in distal axons, and inhibition of the interaction of dynactin with dynein increased axon lengths on CSPGs. CSPGs decreased the membrane potential of mitochondria, and pharmacological inhibition of mitochondria respiration at the growth cone independent of manipulation of mitochondria positioning impaired axon extension. Combined inhibition of dynactin and potentiation of mitochondria respiration further increased axon lengths on CSPGs relative to inhibition of dynactin alone. These data reveal that the regulation of the localization of mitochondria and ER to growth cones is a previously unappreciated aspect of the effects of CSPGs on embryonic axons. © 2017 Wiley Periodicals, Inc. Develop Neurobiol 77: 1351-1370, 2017. © 2017 Wiley Periodicals, Inc.

  15. Selective axonal growth of embryonic hippocampal neurons according to topographic features of various sizes and shapes

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    Christine E Schmidt


    Full Text Available David Y Fozdar1*, Jae Y Lee2*, Christine E Schmidt2–6, Shaochen Chen1,3–5,7,1Departments of Mechanical Engineering, 2Chemical Engineering, 3Biomedical Engineering; 4Center for Nano Molecular Science and Technology; 5Texas Materials Institute; 6Institute of Neuroscience; 7Microelectronics Research Center, The University of Texas at Austin, Austin, TX, USA *Contributed equally to this workPurpose: Understanding how surface features influence the establishment and outgrowth of the axon of developing neurons at the single cell level may aid in designing implantable scaffolds for the regeneration of damaged nerves. Past studies have shown that micropatterned ridge-groove structures not only instigate axon polarization, alignment, and extension, but are also preferred over smooth surfaces and even neurotrophic ligands.Methods: Here, we performed axonal-outgrowth competition assays using a proprietary four-quadrant topography grid to determine the capacity of various micropatterned topographies to act as stimuli sequestering axon extension. Each topography in the grid consisted of an array of microscale (approximately 2 µm or submicroscale (approximately 300 nm holes or lines with variable dimensions. Individual rat embryonic hippocampal cells were positioned either between two juxtaposing topographies or at the borders of individual topographies juxtaposing unpatterned smooth surface, cultured for 24 hours, and analyzed with respect to axonal selection using conventional imaging techniques.Results: Topography was found to influence axon formation and extension relative to smooth surface, and the distance of neurons relative to topography was found to impact whether the topography could serve as an effective cue. Neurons were also found to prefer submicroscale over microscale features and holes over lines for a given feature size.Conclusion: The results suggest that implementing physical cues of various shapes and sizes on nerve guidance conduits

  16. Developmental plasticity of ascending spinal axons studies using the North American opossum, Didelphis virginiana. (United States)

    Terman, J R; Wang, X M; Martin, G F


    The objectives of the present study were to determine if axons of all ascending tracts grow through the lesion after transection of the thoracic spinal cord during development in the North American opossum, and if so, whether they reach regions of the brain they normally innervate. Opossum pups were subjected to transection of the mid-thoracic cord at PD5, PD8, PD12, PD20, or PD26 and injections of Fast Blue (FB) into the lower thoracic or upper lumbar cord 30-40 days or 6 months later. In the PD5 transected cases, labeled axons were present in all of the supraspinal areas labeled by comparable injections in unlesioned, age-matched controls. In the experimental cases, however, labeled axons appeared to be fewer in number and in some areas more restricted in location than in the controls. When lesions were made at PD8, labeled axons were present in the brain of animals allowed to survive 30-40 days prior to FB injections but they were not observed in those allowed to survive 6 months. When lesions were made at PD12 or later, labeled axons were never found rostral to the lesion. It appears, therefore, that axons of all ascending spinal pathways grow though the lesion after transection of the thoracic cord in developing opossums and that they innervate appropriate areas of the brain. Interestingly, the critical period for such growth is shorter than that for most descending axons, suggesting that factors which influence loss of developmental plasticity are not the same for all axons.

  17. Numerical analysis of the method of internal dialysis of giant axons


    Horn, L.W.


    This paper presents a numerical analysis of the method of internal dialysis used for studies of membrane transport in giant axons. Account is taken of the complete geometry, end effects, and finite dialyzate flow rates. Both influx and efflux experimental conditions are considered. Results place quantitative limits on system performance that are sufficiently general for use in experimental design. The completeness of solute equilibration and the uniformity of solute concentration at the axon ...

  18. The Impact of Motor Axon Misdirection and Attrition on Behavioral Deficit Following Experimental Nerve Injuries (United States)

    Alant, Jacob Daniel de Villiers; Senjaya, Ferry; Ivanovic, Aleksandra; Forden, Joanne; Shakhbazau, Antos; Midha, Rajiv


    Peripheral nerve transection and neuroma-in-continuity injuries are associated with permanent functional deficits, often despite successful end-organ reinnervation. Axonal misdirection with non-specific reinnervation, frustrated regeneration and axonal attrition are believed to be among the anatomical substrates that underlie the poor functional recovery associated with these devastating injuries. Yet, functional deficits associated with axonal misdirection in experimental neuroma-in-continuity injuries have not yet been studied. We hypothesized that experimental neuroma-in-continuity injuries would result in motor axon misdirection and attrition with proportional persistent functional deficits. The femoral nerve misdirection model was exploited to assess major motor pathway misdirection and axonal attrition over a spectrum of experimental nerve injuries, with neuroma-in-continuity injuries simulated by the combination of compression and traction forces in 42 male rats. Sciatic nerve injuries were employed in an additional 42 rats, to evaluate the contribution of axonal misdirection to locomotor deficits by a ladder rung task up to 12 weeks. Retrograde motor neuron labeling techniques were utilized to determine the degree of axonal misdirection and attrition. Characteristic histological neuroma-in-continuity features were demonstrated in the neuroma-in-continuity groups and poor functional recovery was seen despite successful nerve regeneration and muscle reinnervation. Good positive and negative correlations were observed respectively between axonal misdirection (pinjuries of mixed motor nerves that contribute to the long-term functional deficits. Although widely accepted in theory, to our knowledge, this is the first experimental evidence to convincingly demonstrate these correlations with data inclusive of the neuroma-in-continuity spectrum. This work emphasizes the need to focus on strategies that promote both robust and accurate nerve regeneration to optimize

  19. Dysfunction of axonal membrane conductances in adolescents and young adults with spinal muscular atrophy


    Farrar, Michelle A.; Vucic, Steve; Lin, Cindy S.-Y.; Park, Susanna B.; Johnston, Heather M.; du Sart, Desir?e; Bostock, Hugh; Kiernan, Matthew C.


    Spinal muscular atrophy is distinct among neurodegenerative conditions of the motor neuron, with onset in developing and maturing patients. Furthermore, the rate of degeneration appears to slow over time, at least in the milder forms. To investigate disease pathophysiology and potential adaptations, the present study utilized axonal excitability studies to provide insights into axonal biophysical properties and explored correlation with clinical severity. Multiple excitability indices (stimul...

  20. Independent signaling by Drosophila insulin receptor for axon guidance and growth

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    Caroline Rita Li


    Full Text Available The Drosophila insulin receptor (DInR regulates a diverse array of biological processes including growth, axon guidance, and sugar homeostasis. Growth regulation by DInR is mediated by Chico, the Drosophila homolog of vertebrate insulin-receptor-substrate proteins IRS1-4. In contrast, DInR regulation of photoreceptor axon guidance in the developing visual system is mediated by the SH2-SH3 domain adaptor protein Dreadlocks (Dock. In vitro studies by others identified five NPXY motifs, one in the juxtamembrane region and four in the signaling C-terminal tail (C-tail, important for interaction with Chico. Here we used yeast two-hybrid assays to identify regions in the DInR C-tail that interact with Dock. These Dock-binding sites were in separate portions of the C-tail from the previously identified Chico-binding sites. To test whether these sites are required for growth or axon guidance in whole animals, a panel of DInR proteins, in which the putative Chico and Dock interaction sites had been mutated individually or in combination, were tested for their ability to rescue viability, growth, and axon guidance defects of dinr mutant flies. Sites required for viability were identified. Unexpectedly, mutation of both putative Dock binding sites, either individually or in combination, did not lead to defects in photoreceptor axon guidance. Thus, either sites also required for viability are necessary for DInR function in axon guidance and/or there is redundancy built into the DInR/Dock interaction such that Dock is able to interact with multiple regions of DInR. We also found that simultaneous mutation of all 5 NPXY motifs implicated in Chico interaction drastically decreased growth in both male and female adult flies. Mutation of these 5 NPXY motifs did not affect photoreceptor axon guidance, showing that different sites within DInR control growth and axon guidance.

  1. Myelin-associated proteins labelled by slow axonal transport

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    Giorgi, P.P.; DuBois, H.


    This paper deals with the problem of protein metabolism and provides evidence that the neuronal contribution to myelin metabolism may be restricted to lipids only. On the other hand this line of research led to the partial characterization of a group of neuronal proteins probably involved in axo-glial interactions subserving the onset of myelination and the structural maintenance of the mature myelin sheath. Intraocular injection of radioactive amino acids allows the study of the anterograde transport of labelled proteins along retinofugal fibres which are well myelinated. Myelin extracted from the optic nerve and tract under these conditions also contains labelled proteins. Three hypotheses are available to explain this phenomenon. To offer an explanation for this phenomenon the work was planned as follows. a) Characterization of the spatio-temporal pattern of labelling of myelin, in order to define the experimental conditions (survival time and region of the optic pathway to be studied) necessary to obtain maximal labelling. b) Characterization (by gel electrophoresis) of the myelin-associated proteins which become labelled by axonal transport, in order to work on a consistent pattern of labelling. c) Investigation of the possible mechanism responsible for the labelling of myelin-associated proteins. (Auth.)




    The effects of detergents on squid giant axon action and resting potentials as well as membrane conductances in the voltage clamp have been studied. Anionic detergents (sodium lauryl sulfate, 0.1 to 1.0 mM; dimethyl benzene sulfonate, 1 to 20 mM, pH 7.6) cause a temporary increase and a later decrease of action potential height and the value of the resting potential. Cationic detergent (cetyl trimethyl ammonium chloride, 6 x 10(-5)M or more, pH 7.6) generally brings about immediate and irreversible decreases in the action and resting potentials. Non-ionic detergent (tween 80, 0.1 M, pH 7.6) causes a slight reversible reduction of action potential height without affecting the value of the resting potential. Both anionic and cationic detergents generally decrease the sodium and potassium conductances irreversibly. The effect of non-ionic detergent is to decrease the sodium conductance reversibly, leaving the potassium conductance almost unchanged.

  3. Axon ensheathment and metabolic supply by glial cells in Drosophila. (United States)

    Schirmeier, Stefanie; Matzat, Till; Klämbt, Christian


    Neuronal function requires constant working conditions and a well-balanced supply of ions and metabolites. The metabolic homeostasis in the nervous system crucially depends on the presence of glial cells, which nurture and isolate neuronal cells. Here we review recent findings on how these tasks are performed by glial cells in the genetically amenable model organism Drosophila melanogaster. Despite the small size of its nervous system, which would allow diffusion of metabolites, a surprising division of labor between glial cells and neurons is evident. Glial cells are glycolytically active and transfer lactate and alanine to neurons. Neurons in turn do not require glycolysis but can use the glially provided compounds for their energy homeostasis. Besides feeding neurons, glial cells also insulate neuronal axons in a way similar to Remak fibers in the mammalian nervous system. The molecular mechanisms orchestrating this insulation require neuregulin signaling and resemble the mechanisms controlling glial differentiation in mammals surprisingly well. We hypothesize that metabolic cross talk and insulation of neurons by glial cells emerged early during evolution as two closely interlinked features in the nervous system. This article is part of a Special Issue entitled SI: Myelin Evolution. Copyright © 2015 Elsevier B.V. All rights reserved.

  4. Mechanisms of neurodegeneration and axonal dysfunction in multiple sclerosis. (United States)

    Friese, Manuel A; Schattling, Benjamin; Fugger, Lars


    Multiple sclerosis (MS) is the most frequent chronic inflammatory disease of the CNS, and imposes major burdens on young lives. Great progress has been made in understanding and moderating the acute inflammatory components of MS, but the pathophysiological mechanisms of the concomitant neurodegeneration--which causes irreversible disability--are still not understood. Chronic inflammatory processes that continuously disturb neuroaxonal homeostasis drive neurodegeneration, so the clinical outcome probably depends on the balance of stressor load (inflammation) and any remaining capacity for neuronal self-protection. Hence, suitable drugs that promote the latter state are sorely needed. With the aim of identifying potential novel therapeutic targets in MS, we review research on the pathological mechanisms of neuroaxonal dysfunction and injury, such as altered ion channel activity, and the endogenous neuroprotective pathways that counteract oxidative stress and mitochondrial dysfunction. We focus on mechanisms inherent to neurons and their axons, which are separable from those acting on inflammatory responses and might, therefore, represent bona fide neuroprotective drug targets with the capability to halt MS progression.

  5. Diffuse Axonal Injury: Epidemiology, Outcome and Associated Risk Factors

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    Rita de Cassia Almeida Vieira


    Full Text Available Abstract Diffuse axonal injury (DAI, a type of traumatic injury, is known for its severe consequences. However, there are few studies describing the outcomes of DAI and the risk factors associated with it. This study aimed to describe the outcome for patients with a primary diagnosis of DAI six months after trauma and to identify sociodemographic and clinical factors associated with mortality and dependence at this time point. Seventy-eight patients with DAI were recruited from July 2013 to February 2014 in a prospective cohort study. Patient outcome was analyzed using the Extended Glasgow Outcome Scale (GOS-E within six months of the traumatic injury. The mean Injury Severity Score was 35.0 (SD = 11.9, and the mean New Injury Severity Score (NISS was 46.2 (SD = 15.9. Mild DAI was observed in 44.9% of the patients and severe DAI in 35.9%. Six months after trauma, 30.8% of the patients had died, and 45.1% had shown full recovery according to the GOS-E. In the logistic regression model, the severity variables—DAI with hypoxia, as measured by peripheral oxygen saturation, and hypotension with NISS value—had a statistically significant association with patient mortality; on the other hand, severity of DAI and length of hospital stay were the only significant predictors for dependence. Therefore, severity of DAI emerged as a risk factor for both mortality and dependence.

  6. Detection of functional homotopy in traumatic axonal injury

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    Li, Jian; Gao, Lei; Xie, Kai; Zhan, Jie; Luo, Xiaoping; Wang, Huifang; Zhang, Huifang; Zhao, Jing; Zhou, Fuqing; Zeng, Xianjun; He, Laichang; He, Yulin; Gong, Honghan [Nanchang University, Department of Radiology, The First Affiliated Hospital, Nanchang City, Jiangxi (China)


    This study aimed to explore the interhemispheric intrinsic connectivity in traumatic axonal injury (TAI) patients. Twenty-one patients with TAI (14 males, seven females; mean age, 38.71 ± 15.25 years) and 22 well-matched healthy controls (16 males, six females; mean age, 38.50 ± 13.82 years) were recruited, and from them we obtained resting-state fMRI data. Interhemispheric coordination was examined using voxel-mirrored homotopic connectivity (VMHC) and seed-based functional connectivity analysis was performed. We observed significantly decreased VMHC in a number of regions in TAI patients, including the prefrontal, temporal, occipital, parietal, and posterior cingulate cortices, thalami and cerebellar posterior lobes. Subsequent seed-based functional connectivity analysis revealed widely disrupted functional connectivity between the regions of local homotopic connectivity deficits and other areas of the brain, particularly the areas subserving the default, salience, integrative, and executive systems. The lower VMHC of the inferior frontal gyrus and basal ganglia, thalamus, and caudate were significant correlated with the Beck Depression Inventory score, Clinical Dementia Rating score, and Mini-Mental State Examination score, respectively. TAI is associated with regionally decreased interhemispheric interactions and extensively disrupted seed-based functional connectivity, generating further evidence of diffuse disconnection being associated with clinical symptoms in TAI patients. (orig.)

  7. MRI findings in acute diffuse axonal injured patients

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    Sato, Hidetaka [Nippon Medical School, Tokyo (Japan)


    Diffuse axonal injury (DAI) in the acute stage was clinically evaluated using magnetic resonance imaging (MRI), which is considered superior to computed tomography (CT) in detecting parenchymal brain lesions. MRI was disadvantageous, however, to patients suffering from acute severe head injury because of the long time required to construct imaging and unstable patient vital signs. We conducted MRI safely under a high magnetic field (1.5 tesla) in acute DAI by close observation and with nonmagnetic respirator and electrocardiographic monitoring. MRI was conducted in 95 patients diagnosed with DAI classified into mild (14), moderate (17) and severe (64) DAI by criteria established by Gennarelli (1986). In patients with mild or moderate DAI, CT revealed no lesion in the parenchymal area although MRI detected lesions in every case, mainly in cortical white matter or basal ganglia. In patients with severe DAI, CT revealed parenchymal lesions in 14 although MRI detected further lesions in cortical white matter, basal ganglia, corpus callosum and brainstem in every case. These results correspond well to the experimental model Gennarelli's. This study concluded that MRI was useful in assessing acute DAI patients. (author)

  8. BDNF promotes target innervation of Xenopus mandibular trigeminal axons in vivo. (United States)

    Huang, Jeffrey K; Dorey, Karel; Ishibashi, Shoko; Amaya, Enrique


    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. 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. 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.

  9. Effects of medium flow on axon growth with or without nerve growth factor. (United States)

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


    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. Copyright © 2015 Elsevier Inc. All rights reserved.

  10. PTEN deletion from adult-generated dentate granule cells disrupts granule cell mossy fiber axon structure. (United States)

    LaSarge, Candi L; Santos, Victor R; Danzer, Steve C


    Dysregulation of the mTOR-signaling pathway is implicated in the development of temporal lobe epilepsy. In mice, deletion of PTEN from hippocampal dentate granule cells leads to mTOR hyperactivation and promotes the rapid onset of spontaneous seizures. The mechanism by which these abnormal cells initiate epileptogenesis, however, is unclear. PTEN-knockout granule cells develop abnormally, exhibiting morphological features indicative of increased excitatory input. If these cells are directly responsible for seizure genesis, it follows that they should also possess increased output. To test this prediction, dentate granule cell axon morphology was quantified in control and PTEN-knockout mice. Unexpectedly, PTEN deletion increased giant mossy fiber bouton spacing along the axon length, suggesting reduced innervation of CA3. Increased width of the mossy fiber axon pathway in stratum lucidum, however, which likely reflects an unusual increase in mossy fiber axon collateralization in this region, offsets the reduction in boutons per axon length. These morphological changes predict a net increase in granule cell innervation of CA3. Increased diameter of axons from PTEN-knockout cells would further enhance granule cell communication with CA3. Altogether, these findings suggest that amplified information flow through the hippocampal circuit contributes to seizure occurrence in the PTEN-knockout mouse model of temporal lobe epilepsy. Copyright © 2015 Elsevier Inc. All rights reserved.

  11. Kinesin mRNA is present in the squid giant axon. (United States)

    Gioio, A E; Chun, J T; Crispino, M; Capano, C P; Giuditta, A; Kaplan, B B


    Recently, we reported the construction of a cDNA library encoding a heterogeneous population of polyadenylated mRNAs present in the squid giant axon. The nucleic acid sequencing of several randomly selected clones led to the identification of cDNAs encoding beta-actin and beta-tubulin, two relatively abundant axonal mRNA species. To continue characterization of this unique mRNA population, the axonal cDNA library was screened with a cDNA probe encoding the carboxy terminus of the squid kinesin heavy chain. The sequencing of several positive clones unambiguously identified axonal kinesin cDNA clones. The axonal localization of kinesin mRNA was subsequently verified by in situ hybridization histochemistry. In addition, the presence of kinesin RNA sequences in the axoplasmic polyribosome fraction was demonstrated using PCR methodology. In contrast to these findings, mRNA encoding the squid sodium channel was not detected in axoplasmic RNA, although these sequences were relatively abundant in the giant fiber lobe. Taken together, these findings demonstrate that kinesin mRNA is a component of a select group of mRNAs present in the squid giant axon, and suggest that kinesin may be synthesized locally in this model invertebrate motor neuron.

  12. Local gene expression in axons and nerve endings: the glia-neuron unit. (United States)

    Giuditta, Antonio; Chun, Jong Tai; Eyman, Maria; Cefaliello, Carolina; Bruno, Anna Paola; Crispino, Marianna


    Neurons have complex and often extensively elongated processes. This unique cell morphology raises the problem of how remote neuronal territories are replenished with proteins. For a long time, axonal and presynaptic proteins were thought to be exclusively synthesized in the cell body, which delivered them to peripheral sites by axoplasmic transport. Despite this early belief, protein has been shown to be synthesized in axons and nerve terminals, substantially alleviating the trophic burden of the perikaryon. This observation raised the question of the cellular origin of the peripheral RNAs involved in protein synthesis. The synthesis of these RNAs was initially attributed to the neuron soma almost by default. However, experimental data and theoretical considerations support the alternative view that axonal and presynaptic RNAs are also transcribed in the flanking glial cells and transferred to the axon domain of mature neurons. Altogether, these data suggest that axons and nerve terminals are served by a distinct gene expression system largely independent of the neuron cell body. Such a local system would allow the neuron periphery to respond promptly to environmental stimuli. This view has the theoretical merit of extending to axons and nerve terminals the marginalized concept of a glial supply of RNA (and protein) to the neuron cell body. Most long-term plastic changes requiring de novo gene expression occur in these domains, notably in presynaptic endings, despite their intrinsic lack of transcriptional capacity. This review enlightens novel perspectives on the biology and pathobiology of the neuron by critically reviewing these issues.

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

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    Morgane Belle


    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.

  14. Propagation of action potentials along complex axonal trees. Model and implementation. (United States)

    Manor, Y; Gonczarowski, J; Segev, I


    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).

  15. mRNP assembly, axonal transport, and local translation in neurodegenerative diseases. (United States)

    Khalil, Bilal; Morderer, Dmytro; Price, Phillip L; Liu, Feilin; Rossoll, Wilfried


    The development, maturation, and maintenance of the mammalian nervous system rely on complex spatiotemporal patterns of gene expression. In neurons, this is achieved by the expression of differentially localized isoforms and specific sets of mRNA-binding proteins (mRBPs) that regulate RNA processing, mRNA trafficking, and local protein synthesis at remote sites within dendrites and axons. There is growing evidence that axons contain a specialized transcriptome and are endowed with the machinery that allows them to rapidly alter their local proteome via local translation and protein degradation. This enables axons to quickly respond to changes in their environment during development, and to facilitate axon regeneration and maintenance in adult organisms. Aside from providing autonomy to neuronal processes, local translation allows axons to send retrograde injury signals to the cell soma. In this review, we discuss evidence that disturbances in mRNP transport, granule assembly, axonal localization, and local translation contribute to pathology in various neurodegenerative diseases, including spinal muscular atrophy (SMA), amyotrophic lateral sclerosis (ALS), frontotemporal dementia (FTD), and Alzheimer's disease (AD). Copyright © 2018. Published by Elsevier B.V.

  16. Vesicular Axonal Transport is Modified In Vivo by Tau Deletion or Overexpression in Drosophila

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    Yasmina Talmat-Amar


    Full Text Available Structural microtubule associated protein Tau is found in high amount in axons and is involved in several neurodegenerative diseases. Although many studies have highlighted the toxicity of an excess of Tau in neurons, the in vivo understanding of the endogenous role of Tau in axon morphology and physiology is poor. Indeed, knock-out mice display no strong cytoskeleton or axonal transport phenotype, probably because of some important functional redundancy with other microtubule-associated proteins (MAPs. Here, we took advantage of the model organism Drosophila, which genome contains only one homologue of the Tau/MAP2/MAP4 family to decipher (endogenous Tau functions. We found that Tau depletion leads to a decrease in microtubule number and microtubule density within axons, while Tau excess leads to the opposite phenotypes. Analysis of vesicular transport in tau mutants showed altered mobility of vesicles, but no change in the total amount of putatively mobile vesicles, whereas both aspects were affected when Tau was overexpressed. In conclusion, we show that loss of Tau in tau mutants not only leads to a decrease in axonal microtubule density, but also impairs axonal vesicular transport, albeit to a lesser extent compared to the effects of an excess of Tau.

  17. Decreased expression of axon-guidance receptors in the anterior cingulate cortex in autism

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    Suda Shiro


    Full Text Available Abstract Background Axon-guidance proteins play a crucial role in brain development. As the dysfunction of axon-guidance signaling is thought to underlie the microstructural abnormalities of the brain in people with autism, we examined the postmortem brains of people with autism to identify any changes in the expression of axon-guidance proteins. Results The mRNA and protein expression of axon-guidance proteins, including ephrin (EFNA4, eEFNB3, plexin (PLXNA4, roundabout 2 (ROBO2 and ROBO3, were examined in the anterior cingulate cortex and primary motor cortex of autistic brains (n = 8 and n = 7, respectively and control brains (n = 13 and n = 8, respectively using real-time reverse-transcriptase PCR (RT-PCR and western blotting. Real-time RT-PCR revealed that the relative expression levels of EFNB3, PLXNA4A and ROBO2 were significantly lower in the autistic group than in the control group. The protein levels of these three genes were further analyzed by western blotting, which showed that the immunoreactive values for PLXNA4 and ROBO2, but not for EFNB3, were significantly reduced in the ACC of the autistic brains compared with control brains. Conclusions In this study, we found decreased expression of axon-guidance proteins such as PLXNA4 and ROBO2 in the brains of people with autism, and suggest that dysfunctional axon-guidance protein expression may play an important role in the pathophysiology of autism.

  18. Fractional cable equation for general geometry: A model of axons with swellings and anomalous diffusion (United States)

    López-Sánchez, Erick J.; Romero, Juan M.; Yépez-Martínez, Huitzilin


    Different experimental studies have reported anomalous diffusion in brain tissues and notably this anomalous diffusion is expressed through fractional derivatives. Axons are important to understand neurodegenerative diseases such as multiple sclerosis, Alzheimer's disease, and Parkinson's disease. Indeed, abnormal accumulation of proteins and organelles in axons is a hallmark of these diseases. The diffusion in the axons can become anomalous as a result of this abnormality. In this case the voltage propagation in axons is affected. Another hallmark of different neurodegenerative diseases is given by discrete swellings along the axon. In order to model the voltage propagation in axons with anomalous diffusion and swellings, in this paper we propose a fractional cable equation for a general geometry. This generalized equation depends on fractional parameters and geometric quantities such as the curvature and torsion of the cable. For a cable with a constant radius we show that the voltage decreases when the fractional effect increases. In cables with swellings we find that when the fractional effect or the swelling radius increases, the voltage decreases. Similar behavior is obtained when the number of swellings and the fractional effect increase. Moreover, we find that when the radius swelling (or the number of swellings) and the fractional effect increase at the same time, the voltage dramatically decreases.

  19. Quantitative muscle ultrasound is useful for evaluating secondary axonal degeneration in chronic inflammatory demyelinating polyneuropathy. (United States)

    Hokkoku, Keiichi; Matsukura, Kiyoshi; Uchida, Yudai; Kuwabara, Midori; Furukawa, Yuichi; Tsukamoto, Hiroshi; Hatanaka, Yuki; Sonoo, Masahiro


    In chronic inflammatory demyelinating polyneuropathy (CIDP), exclusion of secondary axonal degeneration is challenging with conventional methods such as nerve conduction study (NCS), needle electromyography, and nerve biopsy. Increased echo intensity (EI) and decreased muscle thickness (MT) identified on muscle ultrasound (MUS) examination represent muscle denervation due to axonal degeneration in neurogenic disorders, suggesting MUS as a new tool to detect secondary axonal degeneration in patients with CIDP. EI and MT of abductor pollicis brevis, abductor digiti minimi, and first dorsal interosseous muscles were measured in 16 CIDP patients. Raw values were converted into z -scores using data from 60 normal controls (NCs). Six of 45 muscles showed abnormally high EI and low MT, suggesting denervation following secondary axonal degeneration. These six muscles belonged to two patients with long disease history, unresponsiveness to treatment, and long interval from onset to initial therapy. There were no significant differences in EI and MT ( p  = .23 and .67, respectively) between the CIDP and NC groups, although NCS results revealed obvious demyelinating abnormalities in all CIDP patients, suggesting the fact that muscle structures will be preserved, and EI and MT will not change unless secondary axonal degeneration occurs in CIDP. MUS is a promising tool for evaluating secondary axonal degeneration in patients with CIDP.

  20. Methodological advances in imaging intravital axonal transport [version 1; referees: 3 approved

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    James N. Sleigh


    Full Text Available Axonal transport is the active process whereby neurons transport cargoes such as organelles and proteins anterogradely from the cell body to the axon terminal and retrogradely in the opposite direction. Bi-directional transport in axons is absolutely essential for the functioning and survival of neurons and appears to be negatively impacted by both aging and diseases of the nervous system, such as Alzheimer’s disease and amyotrophic lateral sclerosis. The movement of individual cargoes along axons has been studied in vitro in live neurons and tissue explants for a number of years; however, it is currently unclear as to whether these systems faithfully and consistently replicate the in vivo situation. A number of intravital techniques originally developed for studying diverse biological events have recently been adapted to monitor axonal transport in real-time in a range of live organisms and are providing novel insight into this dynamic process. Here, we highlight these methodological advances in intravital imaging of axonal transport, outlining key strengths and limitations while discussing findings, possible improvements, and outstanding questions.

  1. Plum, an immunoglobulin superfamily protein, regulates axon pruning by facilitating TGF-β signaling. (United States)

    Yu, Xiaomeng M; Gutman, Itai; Mosca, Timothy J; Iram, Tal; Ozkan, Engin; Garcia, K Christopher; Luo, Liqun; Schuldiner, Oren


    Axon pruning during development is essential for proper wiring of the mature nervous system, but its regulation remains poorly understood. We have identified an immunoglobulin superfamily (IgSF) transmembrane protein, Plum, that is cell autonomously required for axon pruning of mushroom body (MB) γ neurons and for ectopic synapse refinement at the developing neuromuscular junction in Drosophila. Plum promotes MB γ neuron axon pruning by regulating the expression of Ecdysone Receptor-B1, a key initiator of axon pruning. Genetic analyses indicate that Plum acts to facilitate signaling of Myoglianin, a glial-derived TGF-β, on MB γ neurons upstream of the type-I TGF-β receptor Baboon. Myoglianin, Baboon, and Ecdysone Receptor-B1 are also required for neuromuscular junction ectopic synapse refinement. Our study highlights both IgSF proteins and TGF-β facilitation as key promoters of developmental axon elimination and demonstrates a mechanistic conservation between MB axon pruning during metamorphosis and the refinement of ectopic larval neuromuscular connections. Copyright © 2013 Elsevier Inc. All rights reserved.

  2. Spinal Glia Division Contributes to Conditioning Lesion-Induced Axon Regeneration Into the Injured Spinal Cord: Potential Role of Cyclic AMP-Induced Tissue Inhibitor of Metalloproteinase-1. (United States)

    Liu, Huaqing; Angert, Mila; Nishihara, Tasuku; Shubayev, Igor; Dolkas, Jennifer; Shubayev, Veronica I


    Regeneration of sensory neurons after spinal cord injury depends on the function of dividing neuronal-glial antigen 2 (NG2)-expressing cells. We have shown that increases in the number of dividing NG2-positive cells through short-term pharmacologic inhibition of matrix metalloproteinases contributes to recovery after spinal cord injury. A conditioning sciatic nerve crush (SNC) preceding spinal cord injury stimulates central sensory axon regeneration via the intraganglionic action of cyclic adenosine monophosphate. Here, using bromodeoxyuridine, mitomycin (mitosis inhibitor), and cholera toxin B tracer, we demonstrate that SNC-induced division of spinal glia is related to the spinal induction of tissue inhibitor of metalloproteinase-1 and contributes to central sensory axon growth into the damaged spinal cord. Dividing cells were mainly NG2-positive and Iba1-positive and included myeloid NG2-positive populations. The cells dividing in response to SNC mainly matured into oligodendrocytes and microglia within the injured spinal cord. Some postmitotic cells remained NG2-reactive and were associated with regenerating fibers. Moreover, intraganglionic tissue inhibitor of metalloproteinase-1 expression was induced after administration of SNC or cyclic adenosine monophosphate analog (dbcAMP) to dorsal root ganglia in vivo and in primary adult dorsal root ganglia cultures. Collectively, these findings support a novel model whereby a cyclic adenosine monophosphate-activated regeneration program induced in sensory neurons by a conditioning peripheral nerve lesion uses tissue inhibitor of metalloproteinase-1 to protect against short-term proteolysis, enabling glial cell division and promoting axon growth into the damaged CNS.

  3. Dendritic Branch Intersections Are Structurally Regulated Targets for Efficient Axonal Wiring and Synaptic Clustering (United States)

    Pinchas, Monika; Baranes, Danny


    Synaptic clustering on dendritic branches enhances plasticity, input integration and neuronal firing. However, the mechanisms guiding axons to cluster synapses at appropriate sites along dendritic branches are poorly understood. We searched for such a mechanism by investigating the structural overlap between dendritic branches and axons in a simplified model of neuronal networks - the hippocampal cell culture. Using newly developed software, we converted images of meshes of overlapping axonal and dendrites into topological maps of intersections, enabling quantitative study of overlapping neuritic geometry at the resolution of single dendritic branch-to-branch and axon-to-branch crossings. Among dendro-dendritic crossing configurations, it was revealed that the orientations through which dendritic branches cross is a regulated attribute. While crossing angle distribution among branches thinner than 1 µm appeared to be random, dendritic branches 1 µm or wider showed a preference for crossing each other at angle ranges of either 50°–70° or 80°–90°. It was then found that the dendro-dendritic crossings themselves, as well as their selective angles, both affected the path of axonal growth. Axons displayed 4 fold stronger tendency to traverse within 2 µm of dendro-dendritic intersections than at farther distances, probably to minimize wiring length. Moreover, almost 70% of the 50°–70° dendro-denritic crossings were traversed by axons from the obtuse angle’s zone, whereas only 15% traversed through the acute angle’s zone. By contrast, axons showed no orientation restriction when traversing 80°–90° crossings. When such traverse behavior was repeated by many axons, they converged in the vicinity of dendro-dendritic intersections, thereby clustering their synaptic connections. Thus, the vicinity of dendritic branch-to-branch crossings appears to be a regulated structure used by axons as a target for efficient wiring and as a preferred site for synaptic

  4. Transient developmental Purkinje cell axonal torpedoes in healthy and ataxic mouse cerebellum

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    Lovisa Ljungberg


    Full Text Available Information is carried out of the cerebellar cortical microcircuit via action potentials propagated along Purkinje cell axons. In several human neurodegenerative diseases, focal axonal swellings on Purkinje cells – known as torpedoes – have been associated with Purkinje cell loss. Interestingly, torpedoes are also reported to appear transiently during development in rat cerebellum. The function of Purkinje cell axonal torpedoes in health as well as in disease is poorly understood. We investigated the properties of developmental torpedoes in the postnatal mouse cerebellum of wildtype and transgenic mice. We found that Purkinje cell axonal torpedoes transiently appeared on axons of Purkinje neurons, with the largest number of torpedoes observed at postnatal day 11 (P11. This was after peak developmental apoptosis had occurred, when Purkinje cell counts in a lobule were static, suggesting that most developmental torpedoes appear on axons of neurons that persist into adulthood. We found that developmental torpedoes were not associated with a presynaptic GABAergic marker, indicating that they are not synapses. They were seldom found at axonal collateral branch points, and lacked microglia enrichment, suggesting that they are unlikely to be involved in axonal refinement. Interestingly, we found several differences between developmental torpedoes and disease-related torpedoes: developmental torpedoes occured largely on myelinated axons, and were not associated with changes in basket cell innervation on their parent soma. Disease-related torpedoes are typically reported to contain neurofilament; while the majority of developmental torpedoes did as well, a fraction of smaller developmental torpedoes did not. These differences indicate that developmental torpedoes may not be functionally identical to disease-related torpedoes. To study this further, we used a mouse model of spinocerebellar ataxia type 6 (SCA6, and found elevated disease

  5. Sustained maximal voluntary contraction produces independent changes in human motor axons and the muscle they innervate.

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    David A Milder

    Full Text Available The repetitive discharges required to produce a sustained muscle contraction results in activity-dependent hyperpolarization of the motor axons and a reduction in the force-generating capacity of the muscle. We investigated the relationship between these changes in the adductor pollicis muscle and the motor axons of its ulnar nerve supply, and the reproducibility of these changes. Ten subjects performed a 1-min maximal voluntary contraction. Activity-dependent changes in axonal excitability were measured using threshold tracking with electrical stimulation at the wrist; changes in the muscle were assessed as evoked and voluntary electromyography (EMG and isometric force. Separate components of axonal excitability and muscle properties were tested at 5 min intervals after the sustained contraction in 5 separate sessions. The current threshold required to produce the target muscle action potential increased immediately after the contraction by 14.8% (p<0.05, reflecting decreased axonal excitability secondary to hyperpolarization. This was not correlated with the decline in amplitude of muscle force or evoked EMG. A late reversal in threshold current after the initial recovery from hyperpolarization peaked at -5.9% at ∼35 min (p<0.05. This pattern was mirrored by other indices of axonal excitability revealing a previously unreported depolarization of motor axons in the late recovery period. Measures of axonal excitability were relatively stable at rest but less so after sustained activity. The coefficient of variation (CoV for threshold current increase was higher after activity (CoV 0.54, p<0.05 whereas changes in voluntary (CoV 0.12 and evoked twitch (CoV 0.15 force were relatively stable. These results demonstrate that activity-dependent changes in motor axon excitability are unlikely to contribute to concomitant changes in the muscle after sustained activity in healthy people. The variability in axonal excitability after sustained activity

  6. Channelrhodopsin-2 localised to the axon initial segment.

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    Matthew S Grubb


    Full Text Available The light-gated cation channel Channelrhodopsin-2 (ChR2 is a powerful and versatile tool for controlling neuronal activity. Currently available versions of ChR2 either distribute uniformly throughout the plasma membrane or are localised specifically to somatodendritic or synaptic domains. Localising ChR2 instead to the axon initial segment (AIS could prove an extremely useful addition to the optogenetic repertoire, targeting the channel directly to the site of action potential initiation, and limiting depolarisation and associated calcium entry elsewhere in the neuron. Here, we describe a ChR2 construct that we localised specifically to the AIS by adding the ankyrinG-binding loop of voltage-gated sodium channels (Na(vII-III to its intracellular terminus. Expression of ChR2-YFP-Na(vII-III did not significantly affect the passive or active electrical properties of cultured rat hippocampal neurons. However, the tiny ChR2 currents and small membrane depolarisations resulting from AIS targeting meant that optogenetic control of action potential firing with ChR2-YFP-Na(vII-III was unsuccessful in baseline conditions. We did succeed in stimulating action potentials with light in some ChR2-YFP-Na(vII-III-expressing neurons, but only when blocking KCNQ voltage-gated potassium channels. We discuss possible alternative approaches to obtaining precise control of neuronal spiking with AIS-targeted optogenetic constructs and propose potential uses for our ChR2-YFP-Na(vII-III probe where subthreshold modulation of action potential initiation is desirable.

  7. Thermodynamic analysis of the squid mantle muscles and giant axon during slow swimming and jet escape propulsion

    International Nuclear Information System (INIS)

    Yalçınkaya, Bahar Hazal; Erikli, Şükrü; Özilgen, Burak Arda; Olcay, Ali Bahadır; Sorgüven, Esra; Özilgen, Mustafa


    Squids have two substantially different types of muscle fibers: superficial mitochondria rich fibers, which perform aerobic respiration during slow swimming, and central mitochondria poor fibers, which perform anaerobic respiration during jet escape. A detailed thermodynamic analysis shows that during slow swimming, 3.82 J/(kg s) of chemical exergy is consumed, and a total muscle work of 0.28 J/(kg s) is produced. 0.27 J/(kg s) of this is produced by the fin to generate lift, and the rest by the mantle volume contraction. During the jet escape at a speed of 3 mantle length/s, squid consumes an exergy of 9.97 J/(kg s) and produces a muscle work of 0.16 J/(kg s). Exergy destruction rates during slow swimming and jet escape modes are 3.54 and 9.81 J/(kg s), respectively. Exergy destroyed because of the action potential propagation in the squid giant axon is calculated as 0.03 and 0.10 J/(kg s) for the slow and fast swimming modes, respectively. - Highlights: • Slow and fast swimming modes of a squid is thermodynamically analyzed. • As swimming speed increases, respiration mode switches from aerobic to anaerobic, and respiration efficiency decreases. • During fast swimming ca. 2.6 times more chemical exergy is consumed. • Both muscles and giant axon destroy nearly 3 times more exergy during jet escape. • Contraction efficiency decreases from 36.8% to 4.7% as the volume of the passive tissue increases from 5% to 95%.

  8. Chlorpyrifos and chlorpyrifos-oxon inhibit axonal growth by interfering with the morphogenic activity of acetylcholinesterase

    International Nuclear Information System (INIS)

    Yang Dongren; Howard, Angela; Bruun, Donald; Ajua-Alemanj, Mispa; Pickart, Cecile; Lein, Pamela J.


    A primary role of acetylcholinesterase (AChE) is regulation of cholinergic neurotransmission by hydrolysis of synaptic acetylcholine. In the developing nervous system, however, AChE also functions as a morphogenic factor to promote axonal growth. This raises the question of whether organophosphorus pesticides (OPs) that are known to selectively bind to and inactivate the enzymatic function of AChE also interfere with its morphogenic function to perturb axonogenesis. To test this hypothesis, we exposed primary cultures of sensory neurons derived from embryonic rat dorsal root ganglia (DRG) to chlorpyrifos (CPF) or its oxon metabolite (CPFO). Both OPs significantly decreased axonal length at concentrations that had no effect on cell viability, protein synthesis or the enzymatic activity of AChE. Comparative analyses of the effects of CPF and CPFO on axonal growth in DRG neurons cultured from AChE nullizygous (AChE -/- ) versus wild type (AChE +/+ ) mice indicated that while these OPs inhibited axonal growth in AChE +/+ DRG neurons, they had no effect on axonal growth in AChE -/- DRG neurons. However, transfection of AChE -/- DRG neurons with cDNA encoding full-length AChE restored the wild type response to the axon inhibitory effects of OPs. These data indicate that inhibition of axonal growth by OPs requires AChE, but the mechanism involves inhibition of the morphogenic rather than enzymatic activity of AChE. These findings suggest a novel mechanism for explaining not only the functional deficits observed in children and animals following developmental exposure to OPs, but also the increased vulnerability of the developing nervous system to OPs

  9. Axon and dendrite geography predict the specificity of synaptic connections in a functioning spinal cord network

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    Borisyuk Roman


    Full Text Available Abstract Background How specific are the synaptic connections formed as neuronal networks develop and can simple rules account for the formation of functioning circuits? These questions are assessed in the spinal circuits controlling swimming in hatchling frog tadpoles. This is possible because detailed information is now available on the identity and synaptic connections of the main types of neuron. Results The probabilities of synapses between 7 types of identified spinal neuron were measured directly by making electrical recordings from 500 pairs of neurons. For the same neuron types, the dorso-ventral distributions of axons and dendrites were measured and then used to calculate the probabilities that axons would encounter particular dendrites and so potentially form synaptic connections. Surprisingly, synapses were found between all types of neuron but contact probabilities could be predicted simply by the anatomical overlap of their axons and dendrites. These results suggested that synapse formation may not require axons to recognise specific, correct dendrites. To test the plausibility of simpler hypotheses, we first made computational models that were able to generate longitudinal axon growth paths and reproduce the axon distribution patterns and synaptic contact probabilities found in the spinal cord. To test if probabilistic rules could produce functioning spinal networks, we then made realistic computational models of spinal cord neurons, giving them established cell-specific properties and connecting them into networks using the contact probabilities we had determined. A majority of these networks produced robust swimming activity. Conclusion Simple factors such as morphogen gradients controlling dorso-ventral soma, dendrite and axon positions may sufficiently constrain the synaptic connections made between different types of neuron as the spinal cord first develops and allow functional networks to form. Our analysis implies that

  10. ON Cone Bipolar Cell Axonal Synapses in the OFF Inner Plexiform Layer of the Rabbit Retina (United States)

    Lauritzen, J. Scott; Anderson, James R.; Jones, Bryan W.; Watt, Carl B.; Mohammed, Shoeb; Hoang, John V.; Marc, Robert E.


    Analysis of the rabbit retinal connectome RC1 reveals that the division between the ON and OFF inner plexiform layer (IPL) is not structurally absolute. ON cone bipolar cells make non-canonical axonal synapses onto specific targets and receive amacrine cell synapses in the nominal OFF layer, creating novel motifs, including inhibitory crossover networks. Automated transmission electron microscope (ATEM) imaging, molecular tagging, tracing, and rendering of ≈ 400 bipolar cells reveals axonal ribbons in 36% of ON cone bipolar cells, throughout the OFF IPL. The targets include GABA-positive amacrine cells (γACs), glycine-positive amacrine cells (GACs) and ganglion cells. Most ON cone bipolar cell axonal contacts target GACs driven by OFF cone bipolar cells, forming new architectures for generating ON-OFF amacrine cells. Many of these ON-OFF GACs target ON cone bipolar cell axons, ON γACs and/or ON-OFF ganglion cells, representing widespread mechanisms for OFF to ON crossover inhibition. Other targets include OFF γACs presynaptic to OFF bipolar cells, forming γAC-mediated crossover motifs. ON cone bipolar cell axonal ribbons drive bistratified ON-OFF ganglion cells in the OFF layer and provide ON drive to polarity-appropriate targets such as bistratified diving ganglion cells (bsdGCs). The targeting precision of ON cone bipolar cell axonal synapses shows that this drive incidence is necessarily a joint distribution of cone bipolar cell axonal frequency and target cell trajectories through a given volume of the OFF layer. Such joint distribution sampling is likely common when targets are sparser than sources and when sources are coupled, as are ON cone bipolar cells. PMID:23042441

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

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    Keith B Godfrey


    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.

  12. Axonal Regeneration in Mammals with Spinal Cord Injury (United States)


    Cajal, S. 1905. Notas preventivas sobre la degeneracion y regeneracion las vias nerviosos centrales . Trab. Lab. Invest. Biol. Univ. Madrid, 4: 295-301...S. 1914. Degeneracion y Regeneration del Sistema Nervioso , Vol. 1, 2. (Nicolas Moya, Madrid), Ramon y Cajal, S. 1928. Degeneration and Regeneration...field of central nervous system (CNS) regeneration research. These developments have revealed important aspects regarding the histology and

  13. Development of the Early Axon Scaffold in the Rostral Brain of the Small Spotted Cat Shark (Scyliorhinus canicula) Embryo


    Ware, Michelle; Waring, Colin P.; Schubert, Frank R.


    International audience; The cat shark is increasingly used as a model for Chondrichthyes, an evolutionarily important sister group of the bony vertebrates that include teleosts and tetrapods. In the bony vertebrates, the first axon tracts form a highly conserved early axon scaffold. The corresponding structure has not been well characterised in cat shark and will prove a useful model for comparative studies. Using pan-neural markers, the early axon scaffold of the cat shark, Scyliorhinus cani...

  14. Dynamics of degeneration and regeneration in developing zebrafish peripheral axons reveals a requirement for extrinsic cell types

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    Villegas Rosario


    Full Text Available Abstract Background Understanding the cellular mechanisms regulating axon degeneration and regeneration is crucial for developing treatments for nerve injury and neurodegenerative disease. In neurons, axon degeneration is distinct from cell body death and often precedes or is associated with the onset of disease symptoms. In the peripheral nervous system of both vertebrates and invertebrates, after degeneration of detached fragments, axons can often regenerate to restore function. Many studies of axonal degeneration and regeneration have used in vitro approaches, but the influence of extrinsic cell types on these processes can only be fully addressed in live animals. Because of its simplicity and superficial location, the larval zebrafish posterior lateral line (pLL nerve is an ideal model system for live studies of axon degeneration and regeneration. Results We used laser axotomy and time-lapse imaging of pLL axons to characterize the roles of leukocytes, Schwann cells and target sensory hair cells in axon degeneration and regeneration in vivo. Immune cells were essential for efficient removal of axonal debris after axotomy. Schwann cells were required for proper fasciculation and pathfinding of regenerating axons to their target cells. Intact target hair cells were not themselves required for regeneration, but chemical ablation of neuromasts caused axons to transiently deviate from their normal paths. Conclusions Macrophages, Schwann cells, and target sensory organs are required for distinct aspects of pLL axon degeneration or regeneration in the zebrafish larva. Our work introduces a powerful vertebrate model for analyzing axonal degeneration and regeneration in the living animal and elucidating the role of extrinsic cell types in these processes.

  15. Bergmann glia and the recognition molecule CHL1 organize GABAergic axons and direct innervation of Purkinje cell dendrites.

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    Fabrice Ango


    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.

  16. Molecular mechanisms of retinal ganglion cell degeneration in glaucoma and future prospects for cell body and axonal protection

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    Yasunari eMunemasa


    Full Text Available Glaucoma, which affects more than 70 million people worldwide, is a heterogeneous group of disorders with a resultant common denominator; optic neuropathy, eventually leading to irreversible blindness. The clinical manifestations of primary open-angle glaucoma (POAG, the most common subtype of glaucoma, include excavation of the optic disc and progressive loss of visual field. Axonal degeneration of retinal ganglion cells (RGCs and apoptotic death of their cell bodies are observed in glaucoma, in which the reduction of intraocular pressure is known to slow progression of the disease. A pattern of localized retinal nerve fiber layer defects in glaucoma patients indicates that axonal degeneration may precede RGC body death in this condition. The mechanisms of degeneration of neuronal cell bodies and their axons may differ. In this review, we addressed the molecular mechanisms of cell body death and axonal degeneration in glaucoma and proposed axonal protection in addition to cell body protection. The concept of axonal protection may become a new therapeutic strategy to prevent further axonal degeneration or revive dying axons in patients with preperimetric glaucoma. Further study will be needed to clarify whether the combination therapy of axonal protection and cell body protection will have greater protective effects in early or progressive glaucomatous optic neuropathy.

  17. Patterns of axonal branching of neurons of the substantia nigra pars reticulata and pars lateralis in the rat. (United States)

    Cebrián, Carolina; Parent, André; Prensa, Lucía


    Axons from neurons of the rat substantia nigra pars reticulata (SNr) and pars lateralis (SNl) were traced after injecting their cell body with biotinylated dextran amine. Thirty-two single axons were reconstructed from serial sagittal sections with a camera lucida, whereas four other SNr axons were reconstructed in the coronal plane to determine whether they innervate the contralateral hemisphere. Four distinct types of SNr projection neurons were identified based on their main axonal targets: type I neurons that project to the thalamus; type II neurons that target the thalamus, the superior colliculus (SC), and the pedunculopontine tegmental nucleus (PPTg); type III neurons that project to the periaqueductal gray matter and the thalamus; and type IV neurons that target the deep mesencephalic nucleus (DpMe) and the SC. The axons of the SNl showed the same branching patterns as SNr axons of types I, II, and IV. The coronal reconstructions demonstrated that SNr neurons innervate the thalamus, the SC, and the DpMe bilaterally. At the thalamic level, SNr and SNl axons targeted preferentially the ventral medial, ventral lateral, paracentral, parafascicular, and mediodorsal nuclei. Axons reaching the SC arborized selectively within the deep layers of this structure. Our results reveal that the SNr and SNl harbor several subtypes of projection neurons endowed with a highly patterned set of axon collaterals. This organization allows single neurons of these output structures of the basal ganglia to exert a multifaceted influence on a wide variety of diencephalic and midbrain structures. (c) 2005 Wiley-Liss, Inc.

  18. Slow Muscle Precursors Lay Down a Collagen XV Matrix Fingerprint to Guide Motor Axon Navigation. (United States)

    Guillon, Emilie; Bretaud, Sandrine; Ruggiero, Florence


    The extracellular matrix (ECM) provides local positional information to guide motoneuron axons toward their muscle target. Collagen XV is a basement membrane component mainly expressed in skeletal muscle. We have identified two zebrafish paralogs of the human COL15A1 gene, col15a1a and col15a1b, which display distinct expression patterns. Here we show that col15a1b is expressed and deposited in the motor path ECM by slow muscle precursors also called adaxial cells. We further demonstrate that collagen XV-B deposition is both temporally and spatially regulated before motor axon extension from the spinal cord in such a way that it remains in this region after the adaxial cells have migrated toward the periphery of the myotome. Loss- and gain-of-function experiments in zebrafish embryos demonstrate that col15a1b expression and subsequent collagen XV-B deposition and organization in the motor path ECM depend on a previously undescribed two-step mechanism involving Hedgehog/Gli and unplugged/MuSK signaling pathways. In silico analysis predicts a putative Gli binding site in the col15a1b proximal promoter. Using col15a1b promoter-reporter constructs, we demonstrate that col15a1b participates in the slow muscle genetic program as a direct target of Hedgehog/Gli signaling. Loss and gain of col15a1b function provoke pathfinding errors in primary and secondary motoneuron axons both at and beyond the choice point where axon pathway selection takes place. These defects result in muscle atrophy and compromised swimming behavior, a phenotype partially rescued by injection of a smyhc1:col15a1b construct. These reveal an unexpected and novel role for collagen XV in motor axon pathfinding and neuromuscular development. In addition to the archetypal axon guidance cues, the extracellular matrix provides local information that guides motor axons from the spinal cord to their muscle targets. Many of the proteins involved are unknown. Using the zebrafish model, we identified an

  19. Cytoplasmic Dynein Transports Axonal Microtubules in a Polarity-Sorting Manner

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    Anand N. Rao


    Full Text Available Axonal microtubules are predominantly organized into a plus-end-out pattern. Here, we tested both experimentally and with computational modeling whether a motor-based polarity-sorting mechanism can explain this microtubule pattern. The posited mechanism centers on cytoplasmic dynein transporting plus-end-out and minus-end-out microtubules into and out of the axon, respectively. When cytoplasmic dynein was acutely inhibited, the bi-directional transport of microtubules in the axon was disrupted in both directions, after which minus-end-out microtubules accumulated in the axon over time. Computational modeling revealed that dynein-mediated transport of microtubules can establish and preserve a predominantly plus-end-out microtubule pattern as per the details of the experimental findings, but only if a kinesin motor and a static cross-linker protein are also at play. Consistent with the predictions of the model, partial depletion of TRIM46, a protein that cross-links axonal microtubules in a manner that influences their polarity orientation, leads to an increase in microtubule transport.

  20. Subcellular Optogenetic Stimulation for Activity-Dependent Myelination of Axons in a Novel Microfluidic Compartmentalized Platform. (United States)

    Lee, Hae Ung; Nag, Sudip; Blasiak, Agata; Jin, Yan; Thakor, Nitish; Yang, In Hong


    Myelination is governed by neuron-glia communication, which in turn is modulated by neural activity. The exact mechanisms remain elusive. We developed a novel in vitro optogenetic stimulation platform that facilitates subcellular activity induction in hundreds of neurons simultaneously. The light isolation was achieved by creating a biocompatible, light-absorbent, black microfluidic device integrated with a programmable, high-power LED array. The system was applied to a compartmentalized culture of primary neurons whose distal axons were interacting with oligodendrocyte precursor cells. Neural activity was induced along whole neurons or was constrained to cell bodies with proximal axons or distal axons only. All three modes of stimulation promoted oligodendrocyte differentiation and the myelination of axons as evidenced by a decrease in the number of oligodendrocyte precursor cells followed by increases in the number of mature oligodendrocytes and myelin sheath fragments. These results demonstrated the potential of our novel optogenetic stimulation system for the global and focal induction of neural activity in vitro for studying axon myelination.

  1. Combining Constitutively Active Rheb Expression and Chondroitinase Promotes Functional Axonal Regeneration after Cervical Spinal Cord Injury. (United States)

    Wu, Di; Klaw, Michelle C; Connors, Theresa; Kholodilov, Nikolai; Burke, Robert E; Côté, Marie-Pascale; Tom, Veronica J


    After spinal cord injury (SCI), severed axons in the adult mammalian CNS are unable to mount a robust regenerative response. In addition, the glial scar at the lesion site further restricts the regenerative potential of axons. We hypothesized that a combinatorial approach coincidentally targeting these obstacles would promote axonal regeneration. We combined (1) transplantation of a growth-permissive peripheral nerve graft (PNG) into an incomplete, cervical lesion cavity; (2) transduction of neurons rostral to the SCI site to express constitutively active Rheb (caRheb; a Ras homolog enriched in brain), a GTPase that directly activates the growth-promoting pathway mammalian target of rapamycin (mTOR) via AAV-caRheb injection; and (3) digestion of growth-inhibitory chondroitin sulfate proteoglycans within the glial scar at the distal PNG interface using the bacterial enzyme chondroitinase ABC (ChABC). We found that expressing caRheb in neurons post-SCI results in modestly yet significantly more axons regenerating across a ChABC-treated distal graft interface into caudal spinal cord than either treatment alone. Excitingly, we found that caRheb+ChABC treatment significantly potentiates the formation of synapses in the host spinal cord and improves the animals' ability to use the affected forelimb. Thus, this combination strategy enhances functional axonal regeneration following a cervical SCI. Copyright © 2017 The American Society of Gene and Cell Therapy. Published by Elsevier Inc. All rights reserved.

  2. Local synthesis of axonal and presynaptic RNA in squid model systems. (United States)

    Eyman, Maria; Cefaliello, Carolina; Ferrara, Eugenia; De Stefano, Rosanna; Lavina, Zeno Scotto; Crispino, Marianna; Squillace, Angela; van Minnen, Jan; Kaplan, Barry B; Giuditta, Antonio


    The presence of active systems of protein synthesis in axons and nerve endings raises the question of the cellular origin of the corresponding RNAs. Our present experiments demonstrate that, besides a possible derivation from neuronal cell bodies, axoplasmic RNAs originate in periaxonal glial cells and presynaptic RNAs derive from nearby cells, presumably glial cells. Indeed, in perfused squid giant axons, delivery of newly synthesized RNA to the axon perfusate is strongly stimulated by axonal depolarization or agonists of glial glutamate and acetylcholine receptors. Likewise, incubation of squid optic lobe slices with [3H]uridine leads to a marked accumulation of [3H]RNA in the large synaptosomes derived from the nerve terminals of retinal photoreceptor neurons. As the cell bodies of these neurons lie outside the optic lobe, the data demonstrate that presynaptic RNA is locally synthesized, presumably by perisynaptic glial cells. Overall, our results support the view that axons and presynaptic regions are endowed with local systems of gene expression which may prove essential for the maintenance and plasticity of these extrasomatic neuronal domains.

  3. Nitric oxide prevents axonal degeneration by inducing HIF-1-dependent expression of erythropoietin. (United States)

    Keswani, Sanjay C; Bosch-Marcé, Marta; Reed, Nicole; Fischer, Angela; Semenza, Gregg L; Höke, Ahmet


    Nitric oxide (NO) is a signaling molecule that can trigger adaptive (physiological) or maladaptive (pathological) responses to stress stimuli in a context-dependent manner. We have previously reported that NO may signal axonal injury to neighboring glial cells. In this study, we show that mice deficient in neuronal nitric oxide synthase (nNOS-/-) are more vulnerable than WT mice to toxin-induced peripheral neuropathy. The administration of NO donors to primary dorsal root ganglion cultures prevents axonal degeneration induced by acrylamide in a dose-dependent manner. We demonstrate that NO-induced axonal protection is dependent on hypoxia-inducible factor (HIF)-1-mediated transcription of erythropoietin (EPO) within glial (Schwann) cells present in the cultures. Transduction of Schwann cells with adenovirus AdCA5 encoding a constitutively active form of HIF-1α results in amelioration of acrylamide-induced axonal degeneration in an EPO-dependent manner. Mice that are partially deficient in HIF-1α (HIF-1α+/-) are also more susceptible than WT littermates to toxic neuropathy. Our results indicate that NO→HIF-1→EPO signaling represents an adaptive mechanism that protects against axonal degeneration.

  4. Improved prediction of direction-dependent, acute axonal injury in piglets. (United States)

    Atlan, Lorre S; Smith, Colin; Margulies, Susan S


    To guide development of safety equipment that reduces sports-related head injuries, we sought to enhance predictive relationships between head movement and acute axonal injury severity. The severity of traumatic brain injury (TBI) is influenced by the magnitude and direction of head kinematics. Previous studies have demonstrated correlation between rotational head kinematics and symptom severity in the adult. More recent studies have demonstrated brain injury age- and direction-dependence, relating head kinematics to white matter tract-oriented strains. We have recently developed and assessed novel rotational head kinematic parameters as predictors of white matter damage in the female immature piglet. We show that many previously published rotational kinematic injury predictor metrics poorly predict acute axonal pathology induced by rapid, non-impact head rotations and that inclusion of cerebral moments of inertia (MOI) in rotational head injury metrics refines prediction of diffuse axonal injury following rapid head rotations for two immature age groups. Rotational Work (RotWork) was the best significant predictor of traumatic axonal injury in both newborn and pre-adolescent piglets following head rotations in the axial, coronal, and sagittal planes. An improvement over current metrics, we find that RotWork, which incorporates head rotation rate, direction, and brain shape, significantly enhanced acute traumatic axonal injury prediction. For similar injury extent, the RotWork threshold is lower for the newborn piglet than the pre-adolescent. © 2017 Wiley Periodicals, Inc.

  5. Formation of compact myelin is required for maturation of the axonal cytoskeleton (United States)

    Brady, S. T.; Witt, A. S.; Kirkpatrick, L. L.; de Waegh, S. M.; Readhead, C.; Tu, P. H.; Lee, V. M.


    Although traditional roles ascribed to myelinating glial cells are structural and supportive, the importance of compact myelin for proper functioning of the nervous system can be inferred from mutations in myelin proteins and neuropathologies associated with loss of myelin. Myelinating Schwann cells are known to affect local properties of peripheral axons (de Waegh et al., 1992), but little is known about effects of oligodendrocytes on CNS axons. The shiverer mutant mouse has a deletion in the myelin basic protein gene that eliminates compact myelin in the CNS. In shiverer mice, both local axonal features like phosphorylation of cytoskeletal proteins and neuronal perikaryon functions like cytoskeletal gene expression are altered. This leads to changes in the organization and composition of the axonal cytoskeleton in shiverer unmyelinated axons relative to age-matched wild-type myelinated fibers, although connectivity and patterns of neuronal activity are comparable. Remarkably, transgenic shiverer mice with thin myelin sheaths display an intermediate phenotype indicating that CNS neurons are sensitive to myelin sheath thickness. These results indicate that formation of a normal compact myelin sheath is required for normal maturation of the neuronal cytoskeleton in large CNS neurons.

  6. Autoradiographic distribution of /sup 125/I-galanin binding sites in the rat central nervous system

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    Skofitsch, G.; Sills, M.A.; Jacobowitz, D.M.


    Galanin (GAL) binding sites in coronal sections of the rat brain were demonstrated using autoradiographic methods. Scatchard analysis of /sup 125/I-GAL binding to slide-mounted tissue sections revealed saturable binding to a single class of receptors with a Kd of approximately 0.2 nM. /sup 125/I-GAL binding sites were demonstrated throughout the rat central nervous system. Dense binding was observed in the following areas: prefrontal cortex, the anterior nuclei of the olfactory bulb, several nuclei of the amygdaloid complex, the dorsal septal area, dorsal bed nucleus of the stria terminalis, the ventral pallidum, the internal medullary laminae of the thalamus, medial pretectal nucleus, nucleus of the medial optic tract, borderline area of the caudal spinal trigeminal nucleus adjacent to the spinal trigeminal tract, the substantia gelatinosa and the superficial layers of the dorsal spinal cord. Moderate binding was observed in the piriform, periamygdaloid, entorhinal, insular cortex and the subiculum, the nucleus accumbens, medial forebrain bundle, anterior hypothalamic, ventromedial, dorsal premamillary, lateral and periventricular thalamic nuclei, the subzona incerta, Forel's field H1 and H2, periventricular gray matter, medial and superficial gray strata of the superior colliculus, dorsal parts of the central gray, peripeduncular area, the interpeduncular nucleus, substantia nigra zona compacta, ventral tegmental area, the dorsal and ventral parabrachial and parvocellular reticular nuclei. The preponderance of GAL-binding in somatosensory as well as in limbic areas suggests a possible involvement of GAL in a variety of brain functions.

  7. Oxidative stress and proinflammatory cytokines contribute to demyelination and axonal damage in a cerebellar culture model of neuroinflammation. (United States)

    di Penta, Alessandra; Moreno, Beatriz; Reix, Stephanie; Fernandez-Diez, Begoña; Villanueva, Maite; Errea, Oihana; Escala, Nagore; Vandenbroeck, Koen; Comella, Joan X; Villoslada, Pablo


    Demyelination and axonal damage are critical processes in the pathogenesis of multiple sclerosis (MS). Oxidative stress and pro-inflammatory cytokines elicited by inflammation mediates tissue damage. To monitor the demyelination and axonal injury associated with microglia activation we employed a model using cerebellar organotypic cultures stimulated with lipopolysaccharide (LPS). Microglia activated by LPS released pro-inflammatory cytokines (IL-1β, IL-6 and TNFα), and increased the expression of inducible nitric oxide synthase (iNOS) and production of reactive oxygen species (ROS). This activation was associated with demyelination and axonal damage in cerebellar cultures. Axonal damage, as revealed by the presence of non-phosphorylated neurofilaments, mitochondrial accumulation in axonal spheroids, and axonal transection, was associated with stronger iNOS expression and concomitant increases in ROS. Moreover, we analyzed the contribution of pro-inflammatory cytokines and oxidative stress in demyelination and axonal degeneration using the iNOS inhibitor ethyl pyruvate, a free-scavenger and xanthine oxidase inhibitor allopurinol, as well as via blockage of pro-inflammatory cytokines using a Fc-TNFR1 construct. We found that blocking microglia activation with ethyl pyruvate or allopurinol significantly decreased axonal damage, and to a lesser extent, demyelination. Blocking TNFα significantly decreased demyelination but did not prevented axonal damage. Moreover, the most common therapy for MS, interferon-beta, was used as an example of an immunomodulator compound that can be tested in this model. In vitro, interferon-beta treatment decreased oxidative stress (iNOS and ROS levels) and the release of pro-inflammatory cytokines after LPS stimulation, reducing axonal damage. The model of neuroinflammation using cerebellar culture stimulated with endotoxin mimicked myelin and axonal damage mediated by the combination of oxidative stress and pro-inflammatory cytokines

  8. A novel ALS-associated variant in UBQLN4 regulates motor axon morphogenesis (United States)

    Edens, Brittany M; Yan, Jianhua; Miller, Nimrod; Deng, Han-Xiang; Siddique, Teepu; Ma, Yongchao C


    The etiological underpinnings of amyotrophic lateral sclerosis (ALS) are complex and incompletely understood, although contributions to pathogenesis by regulators of proteolytic pathways have become increasingly apparent. Here, we present a novel variant in UBQLN4 that is associated with ALS and show that its expression compromises motor axon morphogenesis in mouse motor neurons and in zebrafish. We further demonstrate that the ALS-associated UBQLN4 variant impairs proteasomal function, and identify the Wnt signaling pathway effector beta-catenin as a UBQLN4 substrate. Inhibition of beta-catenin function rescues the UBQLN4 variant-induced motor axon phenotypes. These findings provide a strong link between the regulation of axonal morphogenesis and a new ALS-associated gene variant mediated by protein degradation pathways. DOI: PMID:28463112

  9. Neurofilament subunit (NFL) head domain phosphorylation regulates axonal transport of neurofilaments.

    LENUS (Irish Health Repository)

    Yates, Darran M


    Neurofilaments are the intermediate filaments of neurons and are synthesised in neuronal cell bodies and then transported through axons. Neurofilament light chain (NFL) is a principal component of neurofilaments, and phosphorylation of NFL head domain is believed to regulate the assembly of neurofilaments. However, the role that NFL phosphorylation has on transport of neurofilaments is poorly understood. To address this issue, we monitored axonal transport of phosphorylation mutants of NFL. We mutated four known phosphorylation sites in NFL head domain to either preclude phosphorylation, or mimic permanent phosphorylation. Mutation to preclude phosphorylation had no effect on transport but mutation of three sites to mimic permanent phosphorylation inhibited transport. Mutation of all four sites together to mimic permanent phosphorylation proved especially potent at inhibiting transport and also disrupted neurofilament assembly. Our results suggest that NFL head domain phosphorylation is a regulator of neurofilament axonal transport.

  10. Effect of the degree of polar mismatching on traffic jam formation in fast axonal transport. (United States)

    Kuznetsov, A V


    This paper simulates an axon with a region of reversed microtubule (MT) polarity, and investigates how the degree of polar mismatching in this region affects the formation of organelle traps in the axon. The model is based on modified Smith-Simmons equations governing molecular-motor-assisted transport in neurons. It is established that the structure that develops as a result of a region with disoriented MTs consists of two organelle traps, the trap to the left of this region accumulates plus-end-oriented organelles and the trap to the right of this region accumulates minus-end-oriented organelles. The presence of such a structure is shown to inhibit the transport of organelles down the axon. The degree by which the transport of organelles is inhibited depends on the degree of polar mismatching of MTs in the region between MT traps. Four cases with a different degree of polar mismatching are investigated.

  11. Action of a diffusible target-derived chemoattractant on cortical axon branch induction and directed growth. (United States)

    Sato, M; Lopez-Mascaraque, L; Heffner, C D; O'Leary, D D


    Cortical axons innervate their brainstem target, the basilar pons, by the initiation and extension of collateral branches interstitially along their length. To address whether a diffusible pons-derived chemoattractant controls these events, we used cocultures in collagen matrices and time-lapse microscopy. Pontine explants enhanced by 5-fold the de novo initiation of transient branches along cortical axons; most branches were directed toward pons. Of the branches extended toward pons, 2%-3% were stabilized; those extended away were not. Pontine explants also enhanced the stable bifurcation of growth cones and prompted directional changes by growth cone turning and collateral extension. These effects were distance dependent and mimicked by pons-conditioned medium. This evidence indicates that the pons activity promotes branch initiation interstitially along cortical axons, a novel property for a chemoattractant, and provides a directional cue for their growth. These findings suggest that the pons chemoattractant serves as a diffusible target-recognition molecule.

  12. Analytical investigation of various regimes of retrograde trafficking of neurotropic viruses in axons (United States)

    Kuznetsov, Andrey V.


    A model of retrograde axonal transport of neurotropic viruses is developed. The model accounts for active viral transport by dynein motors as well as for passive transport by diffusion; the destruction of the virus as it propagates toward the neuron soma is modeled utilizing a first-order decay rate process. The effect of a limited time during which the axonal synapse is exposed to the virus is incorporated. An analytical solution is obtained. The obtained solution makes it possible to identify four different regimes of viral transport in the axon that correspond to the following situations: (1) Small viral diffusivity and small rate of viral destruction; (2) Large viral diffusivity and small rate of viral destruction; (3) Small viral diffusivity and large rate of viral destruction; (4) Large viral diffusivity and large rate of viral destruction. Characteristic features of these regimes are discussed.

  13. SBF1 mutations associated with autosomal recessive axonal neuropathy with cranial nerve involvement. (United States)

    Manole, Andreea; Horga, Alejandro; Gamez, Josep; Raguer, Nuria; Salvado, Maria; San Millán, Beatriz; Navarro, Carmen; Pittmann, Alan; Reilly, Mary M; Houlden, Henry


    Biallelic mutations in the SBF1 gene have been identified in one family with demyelinating Charcot-Marie-Tooth disease (CMT4B3) and two families with axonal neuropathy and additional neurological and skeletal features. Here we describe novel sequence variants in SBF1 (c.1168C>G and c.2209_2210del) as the potential causative mutations in two siblings with severe axonal neuropathy, hearing loss, facial weakness and bulbar features. Pathogenicity of these variants is supported by co-segregation and in silico analyses and evolutionary conservation. Our findings suggest that SBF1 mutations may cause a syndromic form of autosomal recessive axonal neuropathy (AR-CMT2) in addition to CMT4B3.

  14. Effects of palytoxin on sodium and potassium permeabilities in unmyelinated axons. (United States)

    Pichon, Y


    Palytoxin (PTX) is a very potent marine toxin isolated from the Zoanthid Palythoa. Its effects on the nerve membrane have been studied on two different preparations: the giant axon of the Cockroach, Periplaneta americana and the giant axon of the Squids, Loligo pealei and Loligo forbesi. In both preparations, PTX at concentrations ranging from 0.03 to 10 microM depolarized the axonal membrane through a selective increase in the resting sodium conductance. This increase was never reversible and was only temporarily and partly antagonized by tetrodotoxin (TTX) at concentrations which block completely the voltage-dependent sodium conductance. A voltage-clamp analysis of these effects showed that, besides this increase, PTX induced complex modifications of the voltage-dependent ionic conductances and increased the leak conductance. The selectivity of the PTX induced sodium channels seemed to decrease with time. Altogether, the results indicate that PTX induces strong and irreversible modifications of the membrane structure.

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

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    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)


    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.

  16. Oligodendrocytes in the Mouse Corpus Callosum Maintain Axonal Function by Delivery of Glucose

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    Niklas Meyer


    Full Text Available In the optic nerve, oligodendrocytes maintain axonal function by supplying lactate as an energy substrate. Here, we report that, in acute brain slices of the mouse corpus callosum, exogenous glucose deprivation (EGD abolished compound action potentials (CAPs, which neither lactate nor pyruvate could prevent. Loading an oligodendrocyte with 20 mM glucose using a patch pipette prevented EGD-mediated CAP reduction in about 70% of experiments. Loading oligodendrocytes with lactate rescued CAPs less efficiently than glucose. In mice lacking connexin 47, oligodendrocyte filling with glucose did not prevent CAP loss, emphasizing the importance of glial networks for axonal energy supply. Compared with the optic nerve, the astrocyte network in the corpus callosum was less dense, and loading astrocytes with glucose did not prevent CAP loss during EGD. We suggest that callosal oligodendrocyte networks provide energy to sustain axonal function predominantly by glucose delivery, and mechanisms of metabolic support vary across different white matter regions.

  17. Genetic dysfunction of MT-ATP6 causes axonal Charcot-Marie-Tooth disease.

    LENUS (Irish Health Repository)

    Pitceathly, Robert D S


    Charcot-Marie-Tooth (CMT) disease is the most common inherited neuromuscular disorder, affecting 1 in 2,500 individuals. Mitochondrial DNA (mtDNA) mutations are not generally considered within the differential diagnosis of patients with uncomplicated inherited neuropathy, despite the essential requirement of ATP for axonal function. We identified the mtDNA mutation m.9185T>C in MT-ATP6, encoding the ATP6 subunit of the mitochondrial ATP synthase (OXPHOS complex V), at homoplasmic levels in a family with mitochondrial disease in whom a severe motor axonal neuropathy was a striking feature. This led us to hypothesize that mutations in the 2 mtDNA complex V subunit encoding genes, MT-ATP6 and MT-ATP8, might be an unrecognized cause of isolated axonal CMT and distal hereditary motor neuropathy (dHMN).

  18. Disruption of spinal cord white matter and sciatic nerve geometry inhibits axonal growth in vitro in the absence of glial scarring

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    Crutcher Keith A


    Full Text Available Abstract Background Axons within the mature mammalian central nervous system fail to regenerate following injury, usually resulting in long-lasting motor and sensory deficits. Studies involving transplantation of adult neurons into white matter implicate glial scar-associated factors in regeneration failure. However, these studies cannot distinguish between the effects of these factors and disruption of the spatial organization of cells and molecular factors (disrupted geometry. Since white matter can support or inhibit neurite growth depending on the geometry of the fiber tract, the present study sought to determine whether disrupted geometry is sufficient to inhibit neurite growth. Results Embryonic chick sympathetic neurons were cultured on unfixed longitudinal cryostat sections of mature rat spinal cord or sciatic nerve that had been crushed with forceps ex vivo then immediately frozen to prevent glial scarring. Neurite growth on uncrushed portions of spinal cord white matter or sciatic nerve was extensive and highly parallel with the longitudinal axis of the fiber tract but did not extend onto crushed portions. Moreover, neurite growth from neurons attached directly to crushed white matter or nerve tissue was shorter and less parallel compared with neurite growth on uncrushed tissue. In contrast, neurite growth appeared to be unaffected by crushed spinal cord gray matter. Conclusions These observations suggest that glial scar-associated factors are not necessary to block axonal growth at sites of injury. Disruption of fiber tract geometry, perhaps involving myelin-associated neurite-growth inhibitors, may be sufficient to pose a barrier to regenerating axons in spinal cord white matter and peripheral nerves.

  19. Two different pathogenic mechanisms, dying-back axonal neuropathy and pancreatic senescence, are present in the YG8R mouse model of Friedreich’s ataxia

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    Belén Mollá


    Full Text Available Frataxin (FXN deficiency causes Friedreich’s ataxia (FRDA, a multisystem disorder with neurological and non-neurological symptoms. FRDA pathophysiology combines developmental and degenerative processes of dorsal root ganglia (DRG, sensory nerves, dorsal columns and other central nervous structures. A dying-back mechanism has been proposed to explain the peripheral neuropathy and neuropathology. In addition, affected individuals have non-neuronal symptoms such as diabetes mellitus or glucose intolerance. To go further in the understanding of the pathogenic mechanisms of neuropathy and diabetes associated with the disease, we have investigated the humanized mouse YG8R model of FRDA. By biochemical and histopathological studies, we observed abnormal changes involving muscle spindles, dorsal root axons and DRG neurons, but normal findings in the posterior columns and brain, which agree with the existence of a dying-back process similar to that described in individuals with FRDA. In YG8R mice, we observed a large number of degenerated axons surrounded by a sheath exhibiting enlarged adaxonal compartments or by a thin disrupted myelin sheath. Thus, both axonal damage and defects in Schwann cells might underlie the nerve pathology. In the pancreas, we found a high proportion of senescent islets of Langerhans in YG8R mice, which decreases the β-cell number and islet mass to pathological levels, being unable to maintain normoglycemia. As a whole, these results confirm that the lack of FXN induces different pathogenic mechanisms in the nervous system and pancreas in the mouse model of FRDA: dying back of the sensory nerves, and pancreatic senescence.

  20. Robotic gait assistive technology as means to aggressive mobilization strategy in acute rehabilitation following severe diffuse axonal injury: a case study. (United States)

    Stam, Daniel; Fernandez, Jennifer


    Diffuse axonal injury is a prominent cause of disablement post-traumatic brain injury. Utilization of the rapid expansion of our current scientific knowledge base combined with greater access to neurological and assistive technology as adjuncts to providing sensorimotor experience may yield innovative new approaches to rehabilitation based upon a dynamic model of brain response following injury. A 24-year-old female who sustained a traumatic brain injury, bilateral subdural hemorrhage, subarachnoid hemorrhage and severe diffuse axonal injury secondary to a motor vehicle collision. Evidence-based appraisal of present literature suggests a link between graded intensity of aerobic activity to facilitation of neuro-plastic change and up-regulation of neurotrophins essential to functional recovery post-diffuse axonal injury. Following resolution of paroxysmal autonomic instability with dystonia, aggressive early mobilization techniques were progressed utilizing robotic assistive gait technology in combination with conventional therapy. This approach allowed for arguably greater repetition and cardiovascular demands across a six-month inpatient rehabilitation stay. Outcomes in this case suggest that the use of assistive technology to adjunct higher level and intensity rehabilitation strategies may be a safe and effective means towards reduction of disablement following severe traumatic brain and neurological injury. Implications for Rehabilitation Functional recovery and neuroplasticity following diffuse neurological injury involves a complex process determined by the sensorimotor experience provided by rehabilitation clinicians. This process is in part modulated by intrinsic brain biochemical processes correlated to cardiovascular intensity of the activity provided. It is important that rehabilitation professionals monitor physiological response to higher intensity activities to provide an adaptive versus maladaptive response of central nervous system plasticity with

  1. Axonal deficits in young adults with High Functioning Autism and their impact on processing speed

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    Mariana Lazar


    Full Text Available Microstructural white matter deficits in Autism Spectrum Disorders (ASD have been suggested by both histological findings and Diffusion Tensor Imaging (DTI studies, which show reduced fractional anisotropy (FA and increased mean diffusivity (MD. However, imaging reports are generally not consistent across studies and the underlying physiological causes of the reported differences in FA and MD remain poorly understood. In this study, we sought to further characterize white matter deficits in ASD by employing an advanced diffusion imaging method, the Diffusional Kurtosis Imaging (DKI, and a two-compartment diffusion model of white matter. This model differentially describes intra- and extra-axonal white matter compartments using Axonal Water Fraction (faxon a measure reflecting axonal caliber and density, and compartment-specific diffusivity measures. Diagnostic utility of these measures and associations with processing speed performance were also examined. Comparative studies were conducted in 16 young male adults with High Functioning Autism (HFA and 17 typically developing control participants (TDC. Significantly decreased faxon was observed in HFA compared to the control group in most of the major white matter tracts, including the corpus callosum, cortico-spinal tracts, and superior longitudinal, inferior longitudinal and inferior fronto-occipital fasciculi. Intra-axonal diffusivity (Daxon was also found to be reduced in some of these regions. Decreased axial extra-axonal diffusivity (ADextra was noted in the genu of the corpus callosum. Reduced processing speed significantly correlated with decreased faxon and Daxon in several tracts. faxon of the left cortico-spinal tract and superior longitudinal fasciculi showed good accuracy in discriminating the HFA and TDC groups. In conclusion, these findings suggest altered axonal microstructure in young adults with HFA which is associated with reduced processing speed. Compartment-specific diffusion

  2. Cryo Electron Tomography of Herpes Simplex Virus during Axonal Transport and Secondary Envelopment in Primary Neurons (United States)

    Ibiricu, Iosune; Huiskonen, Juha T.; Döhner, Katinka; Bradke, Frank; Sodeik, Beate; Grünewald, Kay


    During herpes simplex virus 1 (HSV1) egress in neurons, viral particles travel from the neuronal cell body along the axon towards the synapse. Whether HSV1 particles are transported as enveloped virions as proposed by the ‘married’ model or as non-enveloped capsids suggested by the ‘separate’ model is controversial. Specific viral proteins may form a recruitment platform for microtubule motors that catalyze such transport. However, their subviral location has remained elusive. Here we established a system to analyze herpesvirus egress by cryo electron tomography. At 16 h post infection, we observed intra-axonal transport of progeny HSV1 viral particles in dissociated hippocampal neurons by live-cell fluorescence microscopy. Cryo electron tomography of frozen-hydrated neurons revealed that most egressing capsids were transported independently of the viral envelope. Unexpectedly, we found not only DNA-containing capsids (cytosolic C-capsids), but also capsids lacking DNA (cytosolic A-/B-capsids) in mid-axon regions. Subvolume averaging revealed lower amounts of tegument on cytosolic A-/B-capsids than on C-capsids. Nevertheless, all capsid types underwent active axonal transport. Therefore, even few tegument proteins on the capsid vertices seemed to suffice for transport. Secondary envelopment of capsids was observed at axon terminals. On their luminal face, the enveloping vesicles were studded with typical glycoprotein-like spikes. Furthermore, we noted an accretion of tegument density at the concave cytosolic face of the vesicle membrane in close proximity to the capsids. Three-dimensional analysis revealed that these assembly sites lacked cytoskeletal elements, but that filamentous actin surrounded them and formed an assembly compartment. Our data support the ‘separate model’ for HSV1 egress, i.e. progeny herpes viruses being transported along axons as subassemblies and not as complete virions within transport vesicles. PMID:22194682

  3. Current contribution of diffusion tensor imaging in the evaluation of diffuse axonal injury

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    Daphine Centola Grassi

    Full Text Available ABSTRACT Traumatic brain injury (TBI is the number one cause of death and morbidity among young adults. Moreover, survivors are frequently left with functional disabilities during the most productive years of their lives. One main aspect of TBI pathology is diffuse axonal injury, which is increasingly recognized due to its presence in 40% to 50% of all cases that require hospital admission. Diffuse axonal injury is defined as widespread axonal damage and is characterized by complete axotomy and secondary reactions due to overall axonopathy. These changes can be seen in neuroimaging studies as hemorrhagic focal areas and diffuse edema. However, the diffuse axonal injury findings are frequently under-recognized in conventional neuroimaging studies. In such scenarios, diffuse tensor imaging (DTI plays an important role because it provides further information on white matter integrity that is not obtained with standard magnetic resonance imaging sequences. Extensive reviews concerning the physics of DTI and its use in the context of TBI patients have been published, but these issues are still hazy for many allied-health professionals. Herein, we aim to review the current contribution of diverse state-of-the-art DTI analytical methods to the understanding of diffuse axonal injury pathophysiology and prognosis, to serve as a quick reference for those interested in planning new studies and who are involved in the care of TBI victims. For this purpose, a comprehensive search in Pubmed was performed using the following keywords: “traumatic brain injury”, “diffuse axonal injury”, and “diffusion tensor imaging”.

  4. Ion channel density regulates switches between regular and fast spiking in soma but not in axons.

    Directory of Open Access Journals (Sweden)

    Hugo Zeberg


    Full Text Available The threshold firing frequency of a neuron is a characterizing feature of its dynamical behaviour, in turn determining its role in the oscillatory activity of the brain. Two main types of dynamics have been identified in brain neurons. Type 1 dynamics (regular spiking shows a continuous relationship between frequency and stimulation current (f-I(stim and, thus, an arbitrarily low frequency at threshold current; Type 2 (fast spiking shows a discontinuous f-I(stim relationship and a minimum threshold frequency. In a previous study of a hippocampal neuron model, we demonstrated that its dynamics could be of both Type 1 and Type 2, depending on ion channel density. In the present study we analyse the effect of varying channel density on threshold firing frequency on two well-studied axon membranes, namely the frog myelinated axon and the squid giant axon. Moreover, we analyse the hippocampal neuron model in more detail. The models are all based on voltage-clamp studies, thus comprising experimentally measurable parameters. The choice of analysing effects of channel density modifications is due to their physiological and pharmacological relevance. We show, using bifurcation analysis, that both axon models display exclusively Type 2 dynamics, independently of ion channel density. Nevertheless, both models have a region in the channel-density plane characterized by an N-shaped steady-state current-voltage relationship (a prerequisite for Type 1 dynamics and associated with this type of dynamics in the hippocampal model. In summary, our results suggest that the hippocampal soma and the two axon membranes represent two distinct kinds of membranes; membranes with a channel-density dependent switching between Type 1 and 2 dynamics, and membranes with a channel-density independent dynamics. The difference between the two membrane types suggests functional differences, compatible with a more flexible role of the soma membrane than that of the axon membrane.

  5. A Local Inflammatory Renin-Angiotensin System Drives Sensory Axon Sprouting in Provoked Vestibulodynia. (United States)

    Liao, Zhaohui; Chakrabarty, Anuradha; Mu, Ying; Bhattacherjee, Aritra; Goestch, Martha; Leclair, Catherine M; Smith, Peter G


    Vestibulodynia is a form of provoked vulvodynia characterized by profound tenderness, hyperinnervation, and frequently inflammation within well-defined areas of the human vestibule. Previous experiments in animal models show that inflammatory hypersensitivity and hyperinnervation occur in concert with establishment of a local renin-angiotensin system (RAS). Moreover, mechanical hypersensitivity and sensory axon sprouting are prevented by blocking effects of angiotensin II on angiotensin II receptor type 2 (AT2) receptors. This case-control study assessed whether a RAS contributes to hyperinnervation observed in human vestibulodynia. Vestibular biopsies from asymptomatic controls or patients' nontender areas showed moderate innervation and small numbers of inflammatory cells. In women with vestibulodynia, tender areas contained increased numbers of mechanoreceptive nociceptor axons, T-cells, macrophages, and B-cells, whereas mast cells were unchanged. RAS proteins were increased because of greater numbers of T cells and B cells expressing angiotensinogen, and increased renin-expressing T cells and macrophages. Chymase, which converts angiotensin I to angiotensin II, was present in constant numbers of mast cells. To determine if tender vestibular tissue generates angiotensin II that promotes axon sprouting, we conditioned culture medium with vestibular tissue. Rat sensory neurons cultured in control-conditioned medium showed normal axon outgrowth, whereas those in tender tissue-conditioned medium showed enhanced sprouting that was prevented by adding an AT2 antagonist or angiotensin II neutralizing antibody. Hypersensitivity in provoked vestibulodynia is therefore characterized by abnormal mechanonociceptor axon proliferation, which is attributable to inflammatory cell-derived angiotensin II (or a closely related peptide) acting on neuronal AT2 receptors. Accordingly, reducing inflammation or blocking AT2 represent rational strategies to mitigate this common pain

  6. Reduced axonal transport in Parkinson's disease cybrid neurites is restored by light therapy

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    De Taboada Luis


    Full Text Available Abstract Background It has been hypothesized that reduced axonal transport contributes to the degeneration of neuronal processes in Parkinson's disease (PD. Mitochondria supply the adenosine triphosphate (ATP needed to support axonal transport and contribute to many other cellular functions essential for the survival of neuronal cells. Furthermore, mitochondria in PD tissues are metabolically and functionally compromised. To address this hypothesis, we measured the velocity of mitochondrial movement in human transmitochondrial cybrid "cytoplasmic hybrid" neuronal cells bearing mitochondrial DNA from patients with sporadic PD and disease-free age-matched volunteer controls (CNT. The absorption of low level, near-infrared laser light by components of the mitochondrial electron transport chain (mtETC enhances mitochondrial metabolism, stimulates oxidative phosphorylation and improves redox capacity. PD and CNT cybrid neuronal cells were exposed to near-infrared laser light to determine if the velocity of mitochondrial movement can be restored by low level light therapy (LLLT. Axonal transport of labeled mitochondria was documented by time lapse microscopy in dopaminergic PD and CNT cybrid neuronal cells before and after illumination with an 810 nm diode laser (50 mW/cm2 for 40 seconds. Oxygen utilization and assembly of mtETC complexes were also determined. Results The velocity of mitochondrial movement in PD cybrid neuronal cells (0.175 +/- 0.005 SEM was significantly reduced (p Conclusion The results from this study support our proposal that axonal transport is reduced in sporadic PD and that a single, brief treatment with near-infrared light can restore axonal transport to control levels. These results are the first demonstration that LLLT can increase axonal transport in model human dopaminergic neuronal cells and they suggest that LLLT could be developed as a novel treatment to improve neuronal function in patients with PD.

  7. In vivo impact of presynaptic calcium channel dysfunction on motor axons in episodic ataxia type 2. (United States)

    Tomlinson, Susan E; Tan, S Veronica; Burke, David; Labrum, Robyn W; Haworth, Andrea; Gibbons, Vaneesha S; Sweeney, Mary G; Griggs, Robert C; Kullmann, Dimitri M; Bostock, Hugh; Hanna, Michael G


    Ion channel dysfunction causes a range of neurological disorders by altering transmembrane ion fluxes, neuronal or muscle excitability, and neurotransmitter release. Genetic neuronal channelopathies affecting peripheral axons provide a unique opportunity to examine the impact of dysfunction of a single channel subtype in detail in vivo. Episodic ataxia type 2 is caused by mutations in CACNA1A, which encodes the pore-forming subunit of the neuronal voltage-gated calcium channel Cav2.1. In peripheral motor axons, this channel is highly expressed at the presynaptic neuromuscular junction where it contributes to action potential-evoked neurotransmitter release, but it is not expressed mid-axon or thought to contribute to action potential generation. Eight patients from five families with genetically confirmed episodic ataxia type 2 underwent neurophysiological assessment to determine whether axonal excitability was normal and, if not, whether changes could be explained by Cav2.1 dysfunction. New mutations in the CACNA1A gene were identified in two families. Nerve conduction studies were normal, but increased jitter in single-fibre EMG studies indicated unstable neuromuscular transmission in two patients. Excitability properties of median motor axons were compared with those in 30 age-matched healthy control subjects. All patients had similar excitability abnormalities, including a high electrical threshold and increased responses to hyperpolarizing (P ataxia type 2 thus has unexpected effects on axon excitability, which may reflect an indirect effect of abnormal calcium current fluxes during development. © The Author (2016). Published by Oxford University Press on behalf of the Guarantors of Brain. All rights reserved.

  8. Dysfunction of axonal membrane conductances in adolescents and young adults with spinal muscular atrophy. (United States)

    Farrar, Michelle A; Vucic, Steve; Lin, Cindy S-Y; Park, Susanna B; Johnston, Heather M; du Sart, Desirée; Bostock, Hugh; Kiernan, Matthew C


    Spinal muscular atrophy is distinct among neurodegenerative conditions of the motor neuron, with onset in developing and maturing patients. Furthermore, the rate of degeneration appears to slow over time, at least in the milder forms. To investigate disease pathophysiology and potential adaptations, the present study utilized axonal excitability studies to provide insights into axonal biophysical properties and explored correlation with clinical severity. Multiple excitability indices (stimulus-response curve, strength-duration time constant, threshold electrotonus, current-threshold relationship and recovery cycle) were investigated in 25 genetically characterized adolescent and adult patients with spinal muscular atrophy, stimulating the median motor nerve at the wrist. Results were compared with 50 age-matched controls. The Medical Research Council sum score and Spinal Muscular Atrophy Functional Rating Scale were used to define the strength and motor functional status of patients with spinal muscular atrophy. In patients with spinal muscular atrophy, there were reductions in compound muscle action potential amplitude (P muscular atrophy, there was reduction of peak amplitude without alteration in axonal excitability; in contrast, in the non-ambulatory or severe spinal muscular atrophy cohort prominent changes in axonal function were apparent. Specifically, there were steep changes in the early phase of hyperpolarization in threshold electrotonus (P muscular atrophy supported a mixed pathology comprising features of axonal degeneration and regeneration. The present study has provided novel insight into the pathophysiology of spinal muscular atrophy, with identification of functional abnormalities involving axonal K(+) and Na(+) conductances and alterations in passive membrane properties, the latter linked to the process of neurodegeneration.

  9. Optically-Induced Neuronal Activity Is Sufficient to Promote Functional Motor Axon Regeneration In Vivo.

    Directory of Open Access Journals (Sweden)

    Patricia J Ward

    Full Text Available Peripheral nerve injuries are common, and functional recovery is very poor. Beyond surgical repair of the nerve, there are currently no treatment options for these patients. In experimental models of nerve injury, interventions (such as exercise and electrical stimulation that increase neuronal activity of the injured neurons effectively enhance axon regeneration. Here, we utilized optogenetics to determine whether increased activity alone is sufficient to promote motor axon regeneration. In thy-1-ChR2/YFP transgenic mice in which a subset of motoneurons express the light-sensitive cation channel, channelrhodopsin (ChR2, we activated axons in the sciatic nerve using blue light immediately prior to transection and surgical repair of the sciatic nerve. At four weeks post-injury, direct muscle EMG responses evoked with both optical and electrical stimuli as well as the ratio of these optical/electrical evoked EMG responses were significantly greater in mice that received optical treatment. Thus, significantly more ChR2+ axons successfully re-innervated the gastrocnemius muscle in mice that received optical treatment. Sections of the gastrocnemius muscles were reacted with antibodies to Synaptic Vesicle Protein 2 (SV2 to quantify the number of re-occupied motor endplates. The number of SV2+ endplates was greater in mice that received optical treatment. The number of retrogradely-labeled motoneurons following intramuscular injection of cholera toxin subunit B (conjugated to Alexa Fluor 555 was greater in mice that received optical treatment. Thus, the acute (1 hour, one-time optical treatment resulted in robust, long-lasting effects compared to untreated animals as well as untreated axons (ChR2-. We conclude that neuronal activation is sufficient to promote motor axon regeneration, and this regenerative effect is specific to the activated neurons.

  10. Effects of p-xylene inhalation on axonal transport in the rat retinal ganglion cells

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    Padilla, S.S.; Lyerly, D.P. (Environmental Protection Agency, Research Triangle Park, NC (USA))


    Although the solvent xylene is suspected of producing nervous system dysfunction in animals and humans, little is known regarding the neurochemical consequences of xylene inhalation. The intent of this study was to determine the effect of intermittent, acute, and subchronic p-xylene exposure on the axonal transport of proteins and glycoproteins within the rat retinofugal tract. A number of different exposure regimens were tested ranging from 50 ppm for a single 6-hr exposure to 1600 ppm 6 hr/day, 5 days/week, for a total of 8 exposure days. Immediately following removal from the inhalation chambers rats were injected intraocularly with (35S)methionine and (3H)fucose (to label retinal proteins and glycoproteins, respectively) and the axonal transport of labeled macromolecules to axons (optic nerve and optic tract) and nerve endings (lateral geniculate body and superior colliculus) was examined 20 hr after precursor injection. Only relatively severe exposure regimens (i.e., 800 or 1600 ppm 6 hr/day, 5 days/week, for 1.5 weeks) produced significant reductions in axonal transport; there was a moderate reduction in the axonal transport of 35S-labeled proteins in the 800-ppm-treated group which was more widespread in the 1600 ppm-treated group. Transport of 3H-labeled glycoproteins was less affected. Assessment of retinal metabolism immediately after isotope injection indicated that the rate of precursor uptake was not reduced in either treatment group. Furthermore, rapid transport was still substantially reduced in animals exposed to 1600 ppm p-xylene and allowed a 13-day withdrawal period. These data indicate that p-xylene inhalation decreases rapid axonal transport supplied to the projections of the rat retinal ganglion cells immediately after cessation of inhalation exposure and that this decreased transport is still apparent 13 days after the last exposure.

  11. Effects of p-xylene inhalation on axonal transport in the rat retinal ganglion cells

    International Nuclear Information System (INIS)

    Padilla, S.S.; Lyerly, D.P.


    Although the solvent xylene is suspected of producing nervous system dysfunction in animals and humans, little is known regarding the neurochemical consequences of xylene inhalation. The intent of this study was to determine the effect of intermittent, acute, and subchronic p-xylene exposure on the axonal transport of proteins and glycoproteins within the rat retinofugal tract. A number of different exposure regimens were tested ranging from 50 ppm for a single 6-hr exposure to 1600 ppm 6 hr/day, 5 days/week, for a total of 8 exposure days. Immediately following removal from the inhalation chambers rats were injected intraocularly with [35S]methionine and [3H]fucose (to label retinal proteins and glycoproteins, respectively) and the axonal transport of labeled macromolecules to axons (optic nerve and optic tract) and nerve endings (lateral geniculate body and superior colliculus) was examined 20 hr after precursor injection. Only relatively severe exposure regimens (i.e., 800 or 1600 ppm 6 hr/day, 5 days/week, for 1.5 weeks) produced significant reductions in axonal transport; there was a moderate reduction in the axonal transport of 35S-labeled proteins in the 800-ppm-treated group which was more widespread in the 1600 ppm-treated group. Transport of 3H-labeled glycoproteins was less affected. Assessment of retinal metabolism immediately after isotope injection indicated that the rate of precursor uptake was not reduced in either treatment group. Furthermore, rapid transport was still substantially reduced in animals exposed to 1600 ppm p-xylene and allowed a 13-day withdrawal period. These data indicate that p-xylene inhalation decreases rapid axonal transport supplied to the projections of the rat retinal ganglion cells immediately after cessation of inhalation exposure and that this decreased transport is still apparent 13 days after the last exposure

  12. Fisiopatología del síndrome de Guillain Barré axonal Physiopathology of axonal acute Guillain Barré syndrome

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    Juan Guillermo Montoya Ch.


    Full Text Available 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 emphasizing on Campylobacter jejuni. 2 Human genetic predisposition. 3 Molecular mimicry between lipopolysaccharides and gangliosides. 4 Mechanisms of action of antiganglioside antibodies and, 5 Pathologic findings.

  13. Axonal voltage-gated ion channels as pharmacological targets for pain

    DEFF Research Database (Denmark)

    Moldovan, Mihai; Alvarez, Susana; Romer Rosberg, Mette


    . The rationale for considering axonal voltage-gated ion channels as targets for pain treatment comes from the accumulating evidence that chronic pain states are associated with a dysregulation of these channels that could alter their specificity and make them more susceptible to pharmacological modulation...... ultimately depends on the function of voltage-gated ion channels. This review focuses on the pharmacological modulators of voltage-gated ion channels known to be present on axonal membrane which represents by far the largest surface of DRG neurons. Blockers of voltage-gated Na(+) channels, openers of voltage...

  14. Sensory-motor axonal polyneuropathy involving cranial nerves: An uncommon manifestation of disulfiram toxicity. (United States)

    Santos, Telma; Martins Campos, António; Morais, Hugo


    Disulfiram (tetraethylthiuram disulfide) has been used for the treatment of alcohol dependence. An axonal sensory-motor polyneuropathy with involvement of cranial pairs due to disulfiram is exceedingly rare. The authors report a unique case of an extremely severe axonal polyneuropathy involving cranial nerves that developed within weeks after a regular dosage of 500mg/day disulfiram. To the authors best knowledge, such a severe and rapidly-progressive course has never been described with disulfiram dosages of only 500mg/day. Copyright © 2016 Elsevier B.V. All rights reserved.

  15. Independent signaling by Drosophila insulin receptor for axon guidance and growth. (United States)

    Li, Caroline R; Guo, Dongyu; Pick, Leslie


    The Drosophila insulin receptor (DInR) regulates a diverse array of biological processes including growth, axon guidance, and sugar homeostasis. Growth regulation by DInR is mediated by Chico, the Drosophila homolog of vertebrate insulin receptor substrate proteins IRS1-4. In contrast, DInR regulation of photoreceptor axon guidance in the developing visual system is mediated by the SH2-SH3 domain adaptor protein Dreadlocks (Dock). In vitro studies by others identified five NPXY motifs, one in the juxtamembrane region and four in the signaling C-terminal tail (C-tail), important for interaction with Chico. Here we used yeast two-hybrid assays to identify regions in the DInR C-tail that interact with Dock. These Dock binding sites were in separate portions of the C-tail from the previously identified Chico binding sites. To test whether these sites are required for growth or axon guidance in whole animals, a panel of DInR proteins, in which the putative Chico and Dock interaction sites had been mutated individually or in combination, were tested for their ability to rescue viability, growth and axon guidance defects of dinr mutant flies. Sites required for viability were identified. Unexpectedly, mutation of both putative Dock binding sites, either individually or in combination, did not lead to defects in photoreceptor axon guidance. Thus, either sites also required for viability are necessary for DInR function in axon guidance and/or there is redundancy built into the DInR/Dock interaction such that Dock is able to interact with multiple regions of DInR. We also found that simultaneous mutation of all five NPXY motifs implicated in Chico interaction drastically decreased growth in both male and female adult flies. These animals resembled chico mutants, supporting the notion that DInR interacts directly with Chico in vivo to control body size. Mutation of these five NPXY motifs did not affect photoreceptor axon guidance, segregating the roles of DInR in the

  16. Schwann cell to axon transfer of ribosomes: toward a novel understanding of the role of glia in the nervous system

    NARCIS (Netherlands)

    Court, F.A.; Hendriks, W.T.J.; Mac Gillavry, H.D.; Alvarez, J.; van Minnen, J.


    Schwann cells play pivotal roles in the development and maintenance of the peripheral nervous system. Here, we show that intact sciatic nerve axons of mice contain a small population of ribosomes, which increases by several orders of magnitude when axons are desomatized (severed from their cell

  17. Negative guidance factor-induced macropinocytosis in the growth cone plays a critical role in repulsive axon turning. (United States)

    Kolpak, Adrianne L; Jiang, Jun; Guo, Daorong; Standley, Clive; Bellve, Karl; Fogarty, Kevin; Bao, Zheng-Zheng


    Macropinocytosis is a type of poorly characterized fluid-phase endocytosis that results in formation of relatively large vesicles. We report that Sonic hedgehog (Shh) protein induces macropinocytosis in the axons through activation of a noncanonical signaling pathway, including Rho GTPase and nonmuscle myosin II. Macropinocytosis induced by Shh is independent of clathrin-mediated endocytosis but dependent on dynamin, myosin II, and Rho GTPase activities. Inhibitors of macropinocytosis also abolished the negative effects of Shh on axonal growth, including growth cone collapse and chemorepulsive axon turning but not turning per se. Conversely, activation of myosin II or treatment of phorbol ester induces macropinocytosis in the axons and elicits growth cone collapse and repulsive axon turning. Furthermore, macropinocytosis is also induced by ephrin-A2, and inhibition of dynamin abolished repulsive axon turning induced by ephrin-A2. Macropinocytosis can be induced ex vivo by high Shh, correlating with axon retraction. These results demonstrate that macropinocytosis-mediated membrane trafficking is an important cellular mechanism involved in axon chemorepulsion induced by negative guidance factors.

  18. C. elegans dystroglycan coordinates responsiveness of follower axons to dorsal/ventral and anterior/posterior guidance cues

    NARCIS (Netherlands)

    Johnson, R.P.; Kramer, J.M.


    Neural development in metazoans is characterized by the establishment of initial process tracts by pioneer axons and the subsequent extension of follower axons along these pioneer processes. Mechanisms governing the fidelity of follower extension along pioneered routes are largely unknown. In C.

  19. RhoA Inactivation Prevents Photoreceptor Axon Retraction in an In Vitro Model of Acute Retinal Detachment


    Fontainhas, Aurora Maria; Townes-Anderson, Ellen


    Axon retraction by rod cells is an early response to detachment that likely contributes to poor outcomes after reattachment. In mammalian retina, blocking RhoA signaling prevents axon retraction. Effective treatment can occur as much as 6 hours after the detachment.

  20. Axonal protection by short-term hyperglycemia with involvement of autophagy in TNF-induced optic nerve degeneration

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    Kana eSase


    Full Text Available Previous reports showed that short-term hyperglycemia protects optic nerve axons in a rat experimental hypertensive glaucoma model. In this study, we investigated whether short-term hyperglycemia prevents tumor necrosis factor (TNF-induced optic nerve degeneration in rats and examined the role of autophagy in this axon change process. In phosphate-buffered saline-treated rat eyes, no significant difference in axon number between the normoglycemic (NG and streptozotocin-induced hyperglycemic (HG groups was seen at 2weeks. Substantial degenerative changes in the axons were noted 2 weeks after intravitreal injection of TNF in the NG group. However, the HG group showed significant protective effects on axons against TNF-induced optic nerve degeneration compared with the NG group. This protective effect was significantly inhibited by 3-methyladenine, an autophagy inhibitor. Immunoblot analysis showed that the LC3-II level in the optic nerve was increased in the HG group compared with the NG group. Increased p62 protein levels in the optic nerve after TNF injection was observed in the NG group, and this increase was inhibited in the HG group. Electron microscopy showed that autophagosomes were increased in optic nerve axons in the HG group. Immunohistochemical study showed that LC3 was colocalized with nerve fibers in the retina and optic nerve in both the NG and HG groups. Short-term hyperglycemia protects axons against TNF-induced optic nerve degeneration. This axonal-protective effect may be associated with autophagy machinery.

  1. Hierarchical axon targeting of Drosophila olfactory receptor neurons specified by the proneural transcription factors Atonal and Amos. (United States)

    Okumura, Misako; Kato, Tomoko; Miura, Masayuki; Chihara, Takahiro


    Sensory information is spatially represented in the brain to form a neural map. It has been suggested that axon-axon interactions are important for neural map formation; however, the underlying mechanisms are not fully understood. We used the Drosophila antennal lobe, the first olfactory center in the brain, as a model for studying neural map formation. Olfactory receptor neurons (ORNs) expressing the same odorant receptor target their axons to a single glomerulus out of approximately 50 glomeruli in the antennal lobe. Previous studies have showed that the axons of Atonal ORNs, specified by Atonal, a basic helix-loop-helix (bHLH) transcription factor, pioneer antennal lobe formation; however, the details remain to be elucidated. Here, we show that genetic ablation of Atonal ORNs affects antennal lobe structure and axon targeting of Amos ORNs, another type of ORN specified by the bHLH transcription factor Amos. During development, Atonal ORNs reach the antennal lobe and form the axon commissure before Amos ORNs. We also found that N-cadherin knockdown specifically in Atonal ORNs disrupts the glomerular boundary in the whole antennal lobe. Our results suggest that Atonal ORNs function as pioneer axons. Thus, correct axon targeting of Atonal ORNs is essential for formation of the whole antennal lobe. © 2015 The Molecular Biology Society of Japan and Wiley Publishing Asia Pty Ltd.

  2. The L1-type cell adhesion molecule Neuroglian is necessary for maintenance of sensory axon advance in the Drosophila embryo

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    Martin Veronica


    Full Text Available Abstract Background Cell adhesion molecules have long been implicated in the regulation of axon growth, but the precise cellular roles played by individual cell adhesion molecules and the molecular basis for their action are still not well understood. We have used the sensory system of the Drosophila embryo to shed light on the mechanism by which the L1-type cell adhesion molecule Neuroglian regulates axon growth. Results We have found a highly penetrant sensory axon stalling phenotype in neuroglian mutant embryos. Axons stalled at a variety of positions along their normal trajectory, but most commonly in the periphery some distance along the peripheral nerve. All lateral and dorsal cluster sensory neurons examined, except for the dorsal cluster neuron dbd, showed stalling. Sensory axons were never seen to project along inappropriate pathways in neuroglian mutants and stalled axons showed normal patterns of fasciculation within nerves. The growth cones of stalled axons possessed a simple morphology, similar to their appearance in wild-type embryos when advancing along nerves. Driving expression of the wild-type form of Neuroglian in sensory neurons alone rescued the neuroglian mutant phenotype of both pioneering and follower neurons. A partial rescue was achieved by expressing the Neuroglian extracellular domain. Over/mis-expression of Neuroglian in all neurons, oenocytes or trachea had no apparent effect on sensory axon growth. Conclusion We conclude that Neuroglian is necessary to maintain axon advance along axonal substrates, but is not required for initiation of axon outgrowth, axon fasciculation or recognition of correct growth substrates. Expression of Neuroglian in sensory neurons alone is sufficient to promote axon advance and the intracellular region of the molecule is largely dispensable for this function. It is unlikely, therefore, that Nrg acts as a molecular 'clutch' to couple adhesion of F-actin within the growth cone to the

  3. Investigating the Slow Axonal Transport of Neurofilaments: A Precursor for Optimal Neuronal Signaling (United States)

    Johnson, Christopher M.

    Neurofilaments are the intermediate filaments of neurons and are the most abundant structure of the neuronal cytoskeleton. Once synthesized within the cell body they are then transported throughout the axon along microtubule tracks, driven by the molecular motors kinesin and dynein. This movement is characterized by long pauses with no movement interrupted by infrequent bouts of rapid movement, resulting in an aggregate dense cytoskeletal structure, which serves to regulate an axon's shape and size. Curiously, the modulated kinetics of these polymers produces a very regular, yet non-uniform, morphology in myelinated axons which are composed of discretely spaced myelin-ensheathed segments that are separated by short constricted regions called "nodes of Ranvier". This unique design optimizes the conduction velocity of myelinated axons at minimal fiber size. Hence, neurofilaments regulate the axon caliber to optimize neuron function. The goal of this dissertation is to investigate the motile mechanism of neurofilament transport as well as the resulting electrophysiological effects that follow. We start by examining highly time-resolved kymograph images generated from recorded neurofilament movement via epifluorescence microscopy. Using kymograph analysis, edge detection algorithms, and pixel smoothing tactics, neurofilament trajectories are extracted and used to obtain statistical distributions for the characteristics of how these filaments move within cells. The results suggest that the observed intermittent and bidirectional motions of these filaments might be explained by a model in which dynein and kinesin motors attach to a single neurofilament cargo and interact through mechanical forces only (i.e. a "tug-of-war" model). We test this hypothesis by developing two discrete-state stochastic models for the kinetic cycles of kinesin and dynein, which are then incorporated into a separate stochastic model that represents the posed tug-of-war scenario. We then

  4. Effects of perinatal daidzein exposure on subsequent behavior and central estrogen receptor α expression in the adult male mouse. (United States)

    Yu, Chengjun; Tai, Fadao; Zeng, Shuangyan; Zhang, Xia


    Daidzein is one of the most important isoflavones present in soy and it is unique as it can be further metabolized to equol, a compound with greater estrogenic activity than other isoflavones. The potential role of daidzein in the prevention of some chronic diseases has drawn public attention and increased its consumption in human, including in pregnant women and adolescent. It is unclear whether perinatal exposure to daidzein through maternal diets affects subsequent behavior and central estrogen receptor α (ERα) expression in male adults. Following developmental exposure to daidzein through maternal diets during perinatal period, subsequent anxiety-like behavior, social behavior, spatial learning and memory of male mice at adulthood were assessed using a series of tests. The levels of central ER α expression were also examined using immunocytochemistry. Compared with the controls, adult male mice exposed to daidzein during the perinatal period showed significantly less exploration, higher levels of anxiety and aggression. They also displayed more social investigation for females and a tendency to improve spatial learning and memory. The mice with this early daidzein treatment demonstrated significantly higher levels of ERα expression in several brain regions such as the bed nucleus of the stria terminalis, medial preoptic, arcuate hypothalamic nucleus and central amygdaloid mucleus, but decreased it in the lateral septum. Our results indicated that perinatal exposure to daidzein enhanced masculinization on male behaviors which is assocciated with alterations in ERα expression levels led by perinatal daidzein exposure. Copyright © 2012 Elsevier Inc. All rights reserved.

  5. Targeting 14-3-3 adaptor protein-protein interactions to stimulate central nervous system repair

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    Andrew Kaplan


    Full Text Available The goal of developing treatments for central nervous system (CNS injuries is becoming more attainable with the recent identification of various drugs that can repair damaged axons. These discoveries have stemmed from screening efforts, large expression datasets and an improved understanding of the cellular and molecular biology underlying axon growth. It will be important to continue searching for new compounds that can induce axon repair. Here we describe how a family of adaptor proteins called 14-3-3s can be targeted using small molecule drugs to enhance axon outgrowth and regeneration. 14-3-3s bind to many functionally diverse client proteins to regulate their functions. We highlight the recent discovery of the axon-growth promoting activity of fusicoccin-A, a fungus-derived small molecule that stabilizes 14-3-3 interactions with their client proteins. Here we discuss how fusicoccin-A could serve as a starting point for the development of drugs to induce CNS repair.

  6. hnRNP R and its main interactor, the noncoding RNA 7SK, coregulate the axonal transcriptome of motoneurons. (United States)

    Briese, Michael; Saal-Bauernschubert, Lena; Ji, Changhe; Moradi, Mehri; Ghanawi, Hanaa; Uhl, Michael; Appenzeller, Silke; Backofen, Rolf; Sendtner, Michael


    Disturbed RNA processing and subcellular transport contribute to the pathomechanisms of motoneuron diseases such as amyotrophic lateral sclerosis and spinal muscular atrophy. RNA-binding proteins are involved in these processes, but the mechanisms by which they regulate the subcellular diversity of transcriptomes, particularly in axons, are not understood. Heterogeneous nuclear ribonucleoprotein R (hnRNP R) interacts with several proteins involved in motoneuron diseases. It is located in axons of developing motoneurons, and its depletion causes defects in axon growth. Here, we used individual nucleotide-resolution cross-linking and immunoprecipitation (iCLIP) to determine the RNA interactome of hnRNP R in motoneurons. We identified ∼3,500 RNA targets, predominantly with functions in synaptic transmission and axon guidance. Among the RNA targets identified by iCLIP, the noncoding RNA 7SK was the top interactor of hnRNP R. We detected 7SK in the nucleus and also in the cytosol of motoneurons. In axons, 7SK localized in close proximity to hnRNP R, and depletion of hnRNP R reduced axonal 7SK. Furthermore, suppression of 7SK led to defective axon growth that was accompanied by axonal transcriptome alterations similar to those caused by hnRNP R depletion. Using a series of 7SK-deletion mutants, we show that the function of 7SK in axon elongation depends on its interaction with hnRNP R but not with the PTEF-B complex involved in transcriptional regulation. These results propose a role for 7SK as an essential interactor of hnRNP R to regulate its function in axon maintenance. Copyright © 2018 the Author(s). Published by PNAS.

  7. Developmental Axon Stretch Stimulates Neuron Growth While Maintaining Normal Electrical Activity, Intracellular Calcium Flux, and Somatic Morphology

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    Joseph R Loverde


    Full Text Available Elongation of nerve fibers intuitively occurs throughout mammalian development, and is synchronized with expansion of the growing body. While most tissue systems enlarge through mitosis and differentiation, elongation of nerve fibers is remarkably unique. The emerging paradigm suggests that axons undergo stretch as contiguous tissues enlarge between the proximal and distal segments of spanning nerve fibers. While stretch is distinct from growth, tension is a known stimulus which regulates the growth of axons. Here, we hypothesized that the axon stretch-growth process may be a natural form of injury, whereby regenerative processes fortify elongating axons in order to prevent disconnection. Harnessing the live imaging capability of our axon stretch-growth bioreactors, we assessed neurons both during and following stretch for biomarkers associated with injury. Utilizing whole-cell patch clamp recording, we found no evidence of changes in spontaneous action potential activity or degradation of elicited action potentials during real-time axon stretch at strains of up to 18 % applied over 5 minutes. Unlike traumatic axonal injury, functional calcium imaging of the soma revealed no shifts in free intracellular calcium during axon stretch. Finally, the cross-sectional areas of nuclei and cytoplasms were normal, with no evidence of chromatolysis following week-long stretch-growth limited to the lower of 25 % strain or 3 mm total daily stretch. The neuronal growth cascade coupled to stretch was concluded to be independent of the changes in membrane potential, action potential generation, or calcium flux associated with traumatic injury. While axon stretch-growth is likely to share overlap with regenerative processes, we conclude that developmental stretch is a distinct stimulus from traumatic axon injury.

  8. Developmental axon stretch stimulates neuron growth while maintaining normal electrical activity, intracellular calcium flux, and somatic morphology. (United States)

    Loverde, Joseph R; Pfister, Bryan J


    Elongation of nerve fibers intuitively occurs throughout mammalian development, and is synchronized with expansion of the growing body. While most tissue systems enlarge through mitosis and differentiation, elongation of nerve fibers is remarkably unique. The emerging paradigm suggests that axons undergo stretch as contiguous tissues enlarge between the proximal and distal segments of spanning nerve fibers. While stretch is distinct from growth, tension is a known stimulus which regulates the growth of axons. Here, we hypothesized that the axon stretch-growth process may be a natural form of injury, whereby regenerative processes fortify elongating axons in order to prevent disconnection. Harnessing the live imaging capability of our axon stretch-growth bioreactors, we assessed neurons both during and following stretch for biomarkers associated with injury. Utilizing whole-cell patch clamp recording, we found no evidence of changes in spontaneous action potential activity or degradation of elicited action potentials during real-time axon stretch at strains of up to 18% applied over 5 min. Unlike traumatic axonal injury, functional calcium imaging of the soma revealed no shifts in free intracellular calcium during axon stretch. Finally, the cross-sectional areas of nuclei and cytoplasms were normal, with no evidence of chromatolysis following week-long stretch-growth limited to the lower of 25% strain or 3 mm total daily stretch. The neuronal growth cascade coupled to stretch was concluded to be independent of the changes in membrane potential, action potential generation, or calcium flux associated with traumatic injury. While axon stretch-growth is likely to share overlap with regenerative processes, we conclude that developmental stretch is a distinct stimulus from traumatic axon injury.

  9. Peptide sharing between influenza A H1N1 hemagglutinin and human axon guidance proteins. (United States)

    Lucchese, Guglielmo; Capone, Giovanni; Kanduc, Darja


    Epidemiologic data suggest that maternal microbial infections may cause fetal neurodevelopmental disorders, potentially increasing susceptibility to heavy psychopathologies such as schizophrenia, schizophreniform disorder, autism, pervasive developmental disorders, bipolar disorders, psychosis, epilepsy, language and speech disorders, and cognitive impairment in adult offspring. However, the molecular pathomechanisms underlying such a relationship are not clear. Here we analyze the potential role of the maternal immune response to viral infection in determining fetal brain injuries that increase the risk of neurological disorders in the adult. We use influenza infection as a disease model and human axon guidance pathway, a key process in the formation of neural network during midgestation, as a potential fetal target of immune insults. Specifically, we examined influenza A H1N1 hemagglutinin (HA), an antigenic viral protein, for amino acid sequence similarity to a random library of 188 axon guidance proteins. We obtain the results that (1) contrary to any theoretical expectations, 45 viral pentapeptide matches are distributed throughout a subset of 36 guidance molecules; (2) in 24 guidance proteins, the peptide sharing with HA antigen involves already experimentally validated influenza HA epitopes; and (3) most of the axon guidance vs HA peptide overlap is conserved among influenza A viral strains and subsets. Taken together, our data indicate that immune cross-reactivity between influenza HA and axon guidance molecules is possible and may well represent a pathologic mechanism capable of determining neurodevelopmental disruption in the fetus.

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


    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…

  11. Subcellular electrical stimulation of neurons enhances the myelination of axons by oligodendrocytes (United States)

    Lee, Hae Ung; Blasiak, Agata; Agrawal, Devansh R.; Loong, Daniel Teh Boon; Thakor, Nitish V.; All, Angelo H.; Ho, John S.


    Myelin formation has been identified as a modulator of neural plasticity. New tools are required to investigate the mechanisms by which environmental inputs and neural activity regulate myelination patterns. In this study, we demonstrate a microfluidic compartmentalized culture system with integrated electrical stimulation capabilities that can induce neural activity by whole cell and focal stimulation. A set of electric field simulations was performed to confirm spatial restriction of the electrical input in the compartmentalized culture system. We further demonstrate that electrode localization is a key consideration for generating uniform the stimulation of neuron and oligodendrocytes within the compartments. Using three configurations of the electrodes we tested the effects of subcellular activation of neural activity on distal axon myelination with oligodendrocytes. We further investigated if oligodendrocytes have to be exposed to the electrical field to induce axon myelination. An isolated stimulation of cell bodies and proximal axons had the same effect as an isolated stimulation of distal axons co-cultured with oligodendrocytes, and the two modes had a non-different result than whole cell stimulation. Our platform enabled the demonstration that electrical stimulation enhances oligodendrocyte maturation and myelin formation independent of the input localization and oligodendrocyte exposure to the electrical field. PMID:28671962

  12. Regulation of mitochondria-dynactin interaction and mitochondrial retrograde transport in axons. (United States)

    Drerup, Catherine M; Herbert, Amy L; Monk, Kelly R; Nechiporuk, Alex V


    Mitochondrial transport in axons is critical for neural circuit health and function. While several proteins have been found that modulate bidirectional mitochondrial motility, factors that regulate unidirectional mitochondrial transport have been harder to identify. In a genetic screen, we found a zebrafish strain in which mitochondria fail to attach to the dynein retrograde motor. This strain carries a loss-of-function mutation in actr10 , a member of the dynein-associated complex dynactin. The abnormal axon morphology and mitochondrial retrograde transport defects observed in actr10 mutants are distinct from dynein and dynactin mutant axonal phenotypes. In addition, Actr10 lacking the dynactin binding domain maintains its ability to bind mitochondria, arguing for a role for Actr10 in dynactin-mitochondria interaction. Finally, genetic interaction studies implicated Drp1 as a partner in Actr10-dependent mitochondrial retrograde transport. Together, this work identifies Actr10 as a factor necessary for dynactin-mitochondria interaction, enhancing our understanding of how mitochondria properly localize in axons.

  13. Nicotinamide riboside, a form of vitamin B3, protects against excitotoxicity-induced axonal degeneration. (United States)

    Vaur, Pauline; Brugg, Bernard; Mericskay, Mathias; Li, Zhenlin; Schmidt, Mark S; Vivien, Denis; Orset, Cyrille; Jacotot, Etienne; Brenner, Charles; Duplus, Eric


    NAD + depletion is a common phenomenon in neurodegenerative pathologies. Excitotoxicity occurs in multiple neurologic disorders and NAD + was shown to prevent neuronal degeneration in this process through mechanisms that remained to be determined. The activity of nicotinamide riboside (NR) in neuroprotective models and the recent description of extracellular conversion of NAD + to NR prompted us to probe the effects of NAD + and NR in protection against excitotoxicity. Here, we show that intracortical administration of NR but not NAD + reduces brain damage induced by NMDA injection. Using cortical neurons, we found that provision of extracellular NR delays NMDA-induced axonal degeneration (AxD) much more strongly than extracellular NAD + Moreover, the stronger effect of NR compared to NAD + depends of axonal stress since in AxD induced by pharmacological inhibition of nicotinamide salvage, both NAD + and NR prevent neuronal death and AxD in a manner that depends on internalization of NR. Taken together, our findings demonstrate that NR is a better neuroprotective agent than NAD + in excitotoxicity-induced AxD and that axonal protection involves defending intracellular NAD + homeostasis.-Vaur, P., Brugg, B., Mericskay, M., Li, Z., Schmidt, M. S., Vivien, D., Orset, C., Jacotot, E., Brenner, C., Duplus, E. Nicotinamide riboside, a form of vitamin B 3 , protects against excitotoxicity-induced axonal degeneration. © FASEB.

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

    International Nuclear Information System (INIS)

    Welsh, Lillian; Tanguay, Robert L.; Svoboda, Kurt R.


    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.

  15. A quantitative method for microstructural analysis of myelinated axons in the injured rodent brain

    NARCIS (Netherlands)

    van Tilborg, E; van Kammen, Caren M; de Theije, CGM; van Meer, Maurits P.A.; Dijkhuizen, RM; Nijboer, CHA


    MRI studies (e.g. using diffusion tensor imaging) revealed that injury to white matter tracts, as observed in for instance perinatal white matter injury and multiple sclerosis, leads to compromised microstructure of myelinated axonal tracts. Alterations in white matter microstructure are also

  16. A quantitative method for microstructural analysis of myelinated axons in the injured rodent brain

    NARCIS (Netherlands)

    Van Tilborg, E. (Erik); Van Kammen, C.M. (Caren M.); De Theije, C.G.M. (Caroline G. M.); Van Meer, M.P.A. (Maurits P. A.); Dijkhuizen, R.M. (Rick M.); Nijboer, C.H. (Cora H.)


    textabstractMRI studies (e.g. using diffusion tensor imaging) revealed that injury to white matter tracts, as observed in for instance perinatal white matter injury and multiple sclerosis, leads to compromised microstructure of myelinated axonal tracts. Alterations in white matter microstructure are

  17. Depth-sensing nano-indentation on a myelinated axon at various stages

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Wei-Chin; Liao, Jiunn-Der [Department of Materials Science and Engineering, National Cheng Kung University, 1 University Road, Tainan 70101, Taiwan (China); Lin, Chou-Ching K [Department of Neurology, National Cheng Kung University, 1 University Road, Tainan 70101, Taiwan (China); Ju, Ming-Shaung, E-mail: [Department of Mechanical Engineering, National Cheng Kung University, 1 University Road, Tainan 70101, Taiwan (China)


    A nano-mechanical characterization of a multi-layered myelin sheath structure, which enfolds an axon and plays a critical role in the transmission of nerve impulses, is conducted. Schwann cells co-cultured in vitro with PC12 cells for various co-culture times are differentiated to form a myelinated axon, which is then observed using a transmission electron microscope. Three major myelination stages, with distinct structural characteristics and thicknesses around the axon, can be produced by varying the co-culture time. A dynamic contact module and continuous depth-sensing nano-indentation are used on the myelinated structure to obtain the load-on-sample versus measured displacement curve of a multi-layered myelin sheath, which is used to determine the work required for the nano-indentation tip to penetrate the myelin sheath. By analyzing the harmonic contact stiffness versus the measured displacement profile, the results can be used to estimate the three stages of the multi-layered structure on a myelinated axon. The method can also be used to evaluate the development stages of myelination or demyelination during nerve regeneration.

  18. Schwann Cell Exosomes Mediate Neuron-Glia Communication and Enhance Axonal Regeneration. (United States)

    Lopez-Leal, Rodrigo; Court, Felipe A


    The functional and structural integrity of the nervous system depends on the coordinated action of neurons and glial cells. Phenomena like synaptic activity, conduction of action potentials, and neuronal growth and regeneration, to name a few, are fine tuned by glial cells. Furthermore, the active role of glial cells in the regulation of neuronal functions is underscored by several conditions in which specific mutation affecting the glia results in axonal dysfunction. We have shown that Schwann cells (SCs), the peripheral nervous system glia, supply axons with ribosomes, and since proteins underlie cellular programs or functions, this dependence of axons from glial cells provides a new and unexplored dimension to our understanding of the nervous system. Recent evidence has now established a new modality of intercellular communication through extracellular vesicles. We have already shown that SC-derived extracellular vesicles known as exosomes enhance axonal regeneration, and increase neuronal survival after pro-degenerative stimuli. Therefore, the biology nervous system will have to be reformulated to include that the phenotype of a nerve cell results from the contribution of two nuclei, with enormous significance for the understanding of the nervous system in health and disease.

  19. A phantom axon setup for validating models of action potential recordings. (United States)

    Rossel, Olivier; Soulier, Fabien; Bernard, Serge; Guiraud, David; Cathébras, Guy


    Electrode designs and strategies for electroneurogram recordings are often tested first by computer simulations and then by animal models, but they are rarely implanted for long-term evaluation in humans. The models show that the amplitude of the potential at the surface of an axon is higher in front of the nodes of Ranvier than at the internodes; however, this has not been investigated through in vivo measurements. An original experimental method is presented to emulate a single fiber action potential in an infinite conductive volume, allowing the potential of an axon to be recorded at both the nodes of Ranvier and the internodes, for a wide range of electrode-to-fiber radial distances. The paper particularly investigates the differences in the action potential amplitude along the longitudinal axis of an axon. At a short radial distance, the action potential amplitude measured in front of a node of Ranvier is two times larger than in the middle of two nodes. Moreover, farther from the phantom axon, the measured action potential amplitude is almost constant along the longitudinal axis. The results of this new method confirm the computer simulations, with a correlation of 97.6 %.

  20. C. elegans ZAG-1, a Zn-finger-homeodomain protein, regulates axonal development and neuronal differentiation. (United States)

    Clark, Scott G; Chiu, Catherine


    Neurons acquire distinct cell identities and implement differential gene programs to generate their appropriate neuronal attributes. On the basis of position, axonal structure and synaptic connectivity, the 302 neurons of the nematode Ceanorhabditis elegans are divided into 118 classes. The development and differentiation of many neurons require the gene zag-1, which encodes a deltaEF1/ZFH-1 Zn-finger-homeodomain protein. zag-1 mutations cause misexpression of neuron-specific genes, block formation of stereotypic axon branches, perturb neuronal migrations, and induce various axon-guidance, fasciculation and branching errors. A zag-1-GFP translational reporter is expressed transiently in most or all neurons during embryogenesis and in select neurons during the first larval stage. Analysis of the zag-1 promoter reveals that zag-1 is expressed in neurons and specific muscles, and that ZAG-1 directly represses its own expression. zag-1 activity also downregulates expression of genes involved in either the synthesis or reuptake of serotonin, dopamine and GABA. We propose that ZAG-1 acts as a transcriptional repressor to regulate multiple, discrete, neuron-specific aspects of terminal differentiation, including cell migration, axonal development and gene expression.

  1. Regenerated Sciatic Nerve Axons Stimulated through a Chronically Implanted Macro-Sieve Electrode. (United States)

    MacEwan, Matthew R; Zellmer, Erik R; Wheeler, Jesse J; Burton, Harold; Moran, Daniel W


    Sieve electrodes provide a chronic interface for stimulating peripheral nerve axons. Yet, successful utilization requires robust axonal regeneration through the implanted electrode. The present study determined the effect of large transit zones in enhancing axonal regeneration and revealed an intimate neural interface with an implanted sieve electrode. Fabrication of the polyimide sieve electrodes employed sacrificial photolithography. The manufactured macro-sieve electrode (MSE) contained nine large transit zones with areas of ~0.285 mm 2 surrounded by eight Pt-Ir metallized electrode sites. Prior to implantation, saline, or glial derived neurotropic factor (GDNF) was injected into nerve guidance silicone-conduits with or without a MSE. The MSE assembly or a nerve guidance conduit was implanted between transected ends of the sciatic nerve in adult male Lewis rats. At 3 months post-operation, fiber counts were similar through both implant types. Likewise, stimulation of nerves regenerated through a MSE or an open silicone conduit evoked comparable muscle forces. These results showed that nerve regeneration was comparable through MSE transit zones and an open conduit. GDNF had a minimal positive effect on the quality and morphology of fibers regenerating through the MSE; thus, the MSE may reduce reliance on GDNF to augment axonal regeneration. Selective stimulation of several individual muscles was achieved through monopolar stimulation of individual electrodes sites suggesting that the MSE might be an optimal platform for functional neuromuscular stimulation.

  2. Local synthesis of axonal and presynaptic RNA in squid model systems

    NARCIS (Netherlands)

    Eyman, M.; Cefaliello, C.; Ferrara, E.; De Stefano, R.; Lavina, Z.S.; Crispino, M.; Squillace, A.; van Minnen, J.; Kaplan, B.B.; Giuditta, A.


    The presence of active systems of protein synthesis in axons and nerve endings raises the question of the cellular origin of the corresponding RNAs. Our present experiments demonstrate that, besides a possible derivation from neuronal cell bodies, axoplasmic RNAs originate in periaxonal glial cells

  3. UV Irradiation Accelerates Amyloid Precursor Protein (APP) Processing and Disrupts APP Axonal Transport (United States)

    Almenar-Queralt, Angels; Falzone, Tomas L.; Shen, Zhouxin; Lillo, Concepcion; Killian, Rhiannon L.; Arreola, Angela S.;