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Sample records for activity-dependent structural plasticity

  1. Phosphorylation of Complexin by PKA Regulates Activity-dependent Spontaneous Neurotransmitter Release and Structural Synaptic Plasticity

    PubMed Central

    Cho, Richard W.; Buhl, Lauren K.; Volfson, Dina; Tran, Adrienne; Li, Feng; Akbergenova, Yulia; Littleton, J. Troy

    2016-01-01

    Summary Synaptic plasticity is a fundamental feature of the nervous system that allows adaptation to changing behavioral environments. Most studies of synaptic plasticity have examined the regulated trafficking of postsynaptic glutamate receptors that generates alterations in synaptic transmission. Whether and how changes in the presynaptic release machinery contribute to neuronal plasticity is less clear. The SNARE complex mediates neurotransmitter release in response to presynaptic Ca++ entry. Here we show that the SNARE fusion clamp Complexin undergoes activity-dependent phosphorylation that alters the basic properties of neurotransmission in Drosophila. Retrograde signaling following stimulation activates PKA-dependent phosphorylation of the Complexin C-terminus that selectively and transiently enhances spontaneous release. Enhanced spontaneous release is required for activity-dependent synaptic growth. These data indicate that SNARE-dependent fusion mechanisms can be regulated in an activity-dependent manner and highlight the key role of spontaneous neurotransmitter release as a mediator of functional and structural plasticity. PMID:26590346

  2. ACTIVITY-DEPENDENT STRUCTURAL PLASTICITY AFTER AVERSIVE EXPERIENCES IN AMYGDALA AND AUDITORY CORTEX PYRAMIDAL NEURONS

    PubMed Central

    Gruene, Tina; Flick, Katelyn; Rendall, Sam; Cho, Jin Hyung; Gray, Jesse; Shansky, Rebecca

    2016-01-01

    The brain is highly plastic and undergoes changes in response to many experiences. Learning especially can induce structural remodeling of dendritic spines, which is thought to relate to memory formation. Classical Pavlovian fear conditioning (FC) traditionally pairs an auditory cue with an aversive footshock, and has been widely used to study neural processes underlying associative learning and memory. Past research has found dendritic spine changes after FC in several structures. But, due to heterogeneity of cells within brain structures and limitations of traditional neuroanatomical techniques, it is unclear if all cells included in analyses were actually active during learning processes, even if known circuits are isolated. In this study, we employed a novel approach to analyze structural plasticity explicitly in neurons activated by exposure to either cued or uncued footshocks. We used male and female Arc-dVenus transgenic mice, which express the Venus fluorophore driven by the activity-related Arc promoter, to identify neurons that were active during either scenario. We then targeted fluorescent microinjections to Arc+ and neighboring Arc− neurons in the basolateral area of the amygdala (BLA) and auditory association cortex (TeA). In both BLA and TeA, Arc+ neurons had reduced thin and mushroom spine densities compared to Arc− neurons. This effect was present in males and females alike and also in both cued and uncued shock groups. Overall, this study adds to our understanding of how neuronal activity affects structural plasticity, and represents a methodological advance in the ways we can directly relate structural changes to experience-related neural activity. PMID:27155146

  3. Role of BDNF epigenetics in activity-dependent neuronal plasticity.

    PubMed

    Karpova, Nina N

    2014-01-01

    Brain-derived neurotrophic factor (BDNF) is a key mediator of the activity-dependent processes in the brain that have a major impact on neuronal development and plasticity. Impaired control of neuronal activity-induced BDNF expression mediates the pathogenesis of various neurological and psychiatric disorders. Different environmental stimuli, such as the use of pharmacological compounds, physical and learning exercises or stress exposure, lead to activation of specific neuronal networks. These processes entail tight temporal and spatial transcriptional control of numerous BDNF splice variants through epigenetic mechanisms. The present review highlights recent findings on the dynamic and long-term epigenetic programming of BDNF gene expression by the DNA methylation, histone-modifying and microRNA machineries. The review also summarizes the current knowledge on the activity-dependent BDNF mRNA trafficking critical for rapid local regulation of BDNF levels and synaptic plasticity. Current data open novel directions for discovery of new promising therapeutic targets for treatment of neuropsychiatric disorders. This article is part of the Special Issue entitled 'BDNF Regulation of Synaptic Structure, Function, and Plasticity'.

  4. Activity-dependent plasticity of hippocampal place maps

    PubMed Central

    Schoenenberger, Philipp; O'Neill, Joseph; Csicsvari, Jozsef

    2016-01-01

    Hippocampal neurons encode a cognitive map of space. These maps are thought to be updated during learning and in response to changes in the environment through activity-dependent synaptic plasticity. Here we examine how changes in activity influence spatial coding in rats using halorhodopsin-mediated, spatially selective optogenetic silencing. Halorhoposin stimulation leads to light-induced suppression in many place cells and interneurons; some place cells increase their firing through disinhibition, whereas some show no effect. We find that place fields of the unaffected subpopulation remain stable. On the other hand, place fields of suppressed place cells were unstable, showing remapping across sessions before and after optogenetic inhibition. Disinhibited place cells had stable maps but sustained an elevated firing rate. These findings suggest that place representation in the hippocampus is constantly governed by activity-dependent processes, and that disinhibition may provide a mechanism for rate remapping. PMID:27282121

  5. Activity-Dependent Plasticity of Astroglial Potassium and Glutamate Clearance

    PubMed Central

    Cheung, Giselle; Sibille, Jérémie; Zapata, Jonathan; Rouach, Nathalie

    2015-01-01

    Recent evidence has shown that astrocytes play essential roles in synaptic transmission and plasticity. Nevertheless, how neuronal activity alters astroglial functional properties and whether such properties also display specific forms of plasticity still remain elusive. Here, we review research findings supporting this aspect of astrocytes, focusing on their roles in the clearance of extracellular potassium and glutamate, two neuroactive substances promptly released during excitatory synaptic transmission. Their subsequent removal, which is primarily carried out by glial potassium channels and glutamate transporters, is essential for proper functioning of the brain. Similar to neurons, different forms of short- and long-term plasticity in astroglial uptake have been reported. In addition, we also present novel findings showing robust potentiation of astrocytic inward currents in response to repetitive stimulations at mild frequencies, as low as 0.75 Hz, in acute hippocampal slices. Interestingly, neurotransmission was hardly affected at this frequency range, suggesting that astrocytes may be more sensitive to low frequency stimulation and may exhibit stronger plasticity than neurons to prevent hyperexcitability. Taken together, these important findings strongly indicate that astrocytes display both short- and long-term plasticity in their clearance of excess neuroactive substances from the extracellular space, thereby regulating neuronal activity and brain homeostasis. PMID:26346563

  6. Activity-dependent plasticity of mouse hippocampal assemblies in vitro

    PubMed Central

    Keller, Martin K.; Draguhn, Andreas; Both, Martin; Reichinnek, Susanne

    2015-01-01

    Memory formation is associated with the generation of transiently stable neuronal assemblies. In hippocampal networks, such groups of functionally coupled neurons express highly ordered spatiotemporal activity patterns which are coordinated by local network oscillations. One of these patterns, sharp wave-ripple complexes (SPW-R), repetitively activates previously established groups of memory-encoding neurons, thereby supporting memory consolidation. This function implies that repetition of specific SPW-R induces plastic changes which render the underlying neuronal assemblies more stable. We modeled this repetitive activation in an in vitro model of SPW-R in mouse hippocampal slices. Weak electrical stimulation upstream of the CA3-CA1 networks reliably induced SPW-R of stereotypic waveform, thus representing re-activation of similar neuronal activity patterns. Frequent repetition of these patterns (100 times) reduced the variance of both, evoked and spontaneous SPW-R waveforms, indicating stabilization of pre-existing assemblies. These effects were most pronounced in the CA1 subfield and depended on the timing of stimulation relative to spontaneous SPW-R. Additionally, plasticity of SPW-R was blocked by application of a NMDA receptor antagonist, suggesting a role for associative synaptic plasticity in this process. Thus, repetitive activation of specific patterns of SPW-R causes stabilization of memory-related networks. PMID:26041998

  7. Activity-Dependent Plasticity and Gene Expression Modifications in the Adult CNS

    PubMed Central

    Carulli, Daniela; Foscarin, Simona; Rossi, Ferdinando

    2011-01-01

    Information processing, memory formation, or functional recovery after nervous system damage depend on the ability of neurons to modify their functional properties or their connections. At the cellular/molecular level, structural modifications of neural circuits are finely regulated by intrinsic neuronal properties and growth-regulatory cues in the extracellular milieu. Recently, it has become clear that stimuli coming from the external world, which comprise sensory inflow, motor activity, cognitive elaboration, or social interaction, not only provide the involved neurons with instructive information needed to shape connection patterns to sustain adaptive function, but also exert a powerful influence on intrinsic and extrinsic growth-related mechanisms, so to create permissive conditions for neuritic remodeling. Here, we present an overview of recent findings concerning the effects of experience on molecular mechanisms underlying CNS structural plasticity, both in physiological conditions and after damage, with particular focus on activity-dependent modulation of growth-regulatory genes and epigenetic modifications. PMID:22144945

  8. Activity-dependent synaptic plasticity of a chalcogenide electronic synapse for neuromorphic systems.

    PubMed

    Li, Yi; Zhong, Yingpeng; Zhang, Jinjian; Xu, Lei; Wang, Qing; Sun, Huajun; Tong, Hao; Cheng, Xiaoming; Miao, Xiangshui

    2014-05-09

    Nanoscale inorganic electronic synapses or synaptic devices, which are capable of emulating the functions of biological synapses of brain neuronal systems, are regarded as the basic building blocks for beyond-Von Neumann computing architecture, combining information storage and processing. Here, we demonstrate a Ag/AgInSbTe/Ag structure for chalcogenide memristor-based electronic synapses. The memristive characteristics with reproducible gradual resistance tuning are utilised to mimic the activity-dependent synaptic plasticity that serves as the basis of memory and learning. Bidirectional long-term Hebbian plasticity modulation is implemented by the coactivity of pre- and postsynaptic spikes, and the sign and degree are affected by assorted factors including the temporal difference, spike rate and voltage. Moreover, synaptic saturation is observed to be an adjustment of Hebbian rules to stabilise the growth of synaptic weights. Our results may contribute to the development of highly functional plastic electronic synapses and the further construction of next-generation parallel neuromorphic computing architecture.

  9. Activity-dependent PSA expression regulates inhibitory maturation and onset of critical period plasticity.

    PubMed

    Di Cristo, Graziella; Chattopadhyaya, Bidisha; Kuhlman, Sandra J; Fu, Yu; Bélanger, Marie-Claude; Wu, Cai Zhi; Rutishauser, Urs; Maffei, Lamberto; Huang, Z Josh

    2007-12-01

    Functional maturation of GABAergic innervation in the developing visual cortex is regulated by neural activity and sensory inputs and in turn influences the critical period of ocular dominance plasticity. Here we show that polysialic acid (PSA), presented by the neural cell adhesion molecule, has a role in the maturation of GABAergic innervation and ocular dominance plasticity. Concentrations of PSA significantly decline shortly after eye opening in the adolescent mouse visual cortex; this decline is hindered by visual deprivation. The developmental and activity-dependent regulation of PSA expression is inversely correlated with the maturation of GABAergic innervation. Premature removal of PSA in visual cortex results in precocious maturation of perisomatic innervation by basket interneurons, enhanced inhibitory synaptic transmission, and earlier onset of ocular dominance plasticity. The developmental and activity-dependent decline of PSA expression therefore regulates the timing of the maturation of GABAergic inhibition and the onset of ocular dominance plasticity.

  10. Rapid and continuous activity-dependent plasticity of olfactory sensory input

    PubMed Central

    Cheetham, Claire E. J.; Park, Una; Belluscio, Leonardo

    2016-01-01

    Incorporation of new neurons enables plasticity and repair of circuits in the adult brain. Adult neurogenesis is a key feature of the mammalian olfactory system, with new olfactory sensory neurons (OSNs) wiring into highly organized olfactory bulb (OB) circuits throughout life. However, neither when new postnatally generated OSNs first form synapses nor whether OSNs retain the capacity for synaptogenesis once mature, is known. Therefore, how integration of adult-born OSNs may contribute to lifelong OB plasticity is unclear. Here, we use a combination of electron microscopy, optogenetic activation and in vivo time-lapse imaging to show that newly generated OSNs form highly dynamic synapses and are capable of eliciting robust stimulus-locked firing of neurons in the mouse OB. Furthermore, we demonstrate that mature OSN axons undergo continuous activity-dependent synaptic remodelling that persists into adulthood. OSN synaptogenesis, therefore, provides a sustained potential for OB plasticity and repair that is much faster than OSN replacement alone. PMID:26898529

  11. NFAT regulates pre-synaptic development and activity-dependent plasticity in Drosophila

    PubMed Central

    Freeman, Amanda; Franciscovich, Amy; Bowers, Mallory; Sandstrom, David J.; Sanyal, Subhabrata

    2010-01-01

    The calcium-regulated transcription factor NFAT is emerging as a key regulator of neuronal development and plasticity but precise cellular consequences of NFAT function remain poorly understood. Here, we report that the single Drosophila NFAT homolog is widely expressed in the nervous system including motor neurons and unexpectedly controls neural excitability. Likely due to this effect on excitability, NFAT regulates overall larval locomotion and both chronic and acute forms of activity-dependent plasticity at the larval glutamatergic neuro-muscular synapse. Specifically, NFAT-dependent synaptic phenotypes include changes in the number of pre-synaptic boutons, stable modifications in synaptic microtubule architecture and pre-synaptic transmitter release, while no evidence is found for synaptic retraction or alterations in the level of the synaptic cell adhesion molecule FasII. We propose that NFAT regulates pre-synaptic development and constraints long-term plasticity by dampening neuronal excitability. PMID:21185939

  12. Activity-dependent plasticity of spike pauses in cerebellar Purkinje cells

    PubMed Central

    Grasselli, Giorgio; He, Qionger; Wan, Vivian; Adelman, John P.; Ohtsuki, Gen; Hansel, Christian

    2016-01-01

    Summary Plasticity of intrinsic excitability has been described in several types of neurons, but the significance of non-synaptic mechanisms in brain plasticity and learning remains elusive. Cerebellar Purkinje cells are inhibitory neurons that spontaneously fire action potentials at high frequencies and regulate activity in their target cells in the cerebellar nuclei by generating a characteristic spike burst–pause sequence upon synaptic activation. Using patch-clamp recordings from mouse Purkinje cells, we find that depolarization-triggered intrinsic plasticity enhances spike firing and shortens the duration of spike pauses. Pause plasticity is absent from mice lacking SK2-type potassium channels (SK2−/− mice) and in occlusion experiments using the SK channel blocker apamin, while apamin wash-in mimics pause reduction. Our findings demonstrate that spike pauses can be regulated through an activity-dependent, exclusively non-synaptic, SK2 channel-dependent mechanism and suggest that pause plasticity—by altering the Purkinje cell output—may be crucial to cerebellar information storage and learning. PMID:26972012

  13. MPTP-meditated hippocampal dopamine deprivation modulates synaptic transmission and activity-dependent synaptic plasticity

    SciTech Connect

    Zhu Guoqi; Chen Ying; Huang Yuying; Li Qinglin; Behnisch, Thomas

    2011-08-01

    Parkinson's disease (PD)-like symptoms including learning deficits are inducible by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Therefore, it is possible that MPTP may disturb hippocampal memory processing by modulation of dopamine (DA)- and activity-dependent synaptic plasticity. We demonstrate here that intraperitoneal (i.p.) MPTP injection reduces the number of tyrosine hydroxylase (TH)-positive neurons in the substantia nigra (SN) within 7 days. Subsequently, the TH expression level in SN and hippocampus and the amount of DA and its metabolite DOPAC in striatum and hippocampus decrease. DA depletion does not alter basal synaptic transmission and changes pair-pulse facilitation (PPF) of field excitatory postsynaptic potentials (fEPSPs) only at the 30 ms inter-pulse interval. In addition, the induction of long-term potentiation (LTP) is impaired whereas the duration of long-term depression (LTD) becomes prolonged. Since both LTP and LTD depend critically on activation of NMDA and DA receptors, we also tested the effect of DA depletion on NMDA receptor-mediated synaptic transmission. Seven days after MPTP injection, the NMDA receptor-mediated fEPSPs are decreased by about 23%. Blocking the NMDA receptor-mediated fEPSP does not mimic the MPTP-LTP. Only co-application of D1/D5 and NMDA receptor antagonists during tetanization resembled the time course of fEPSP potentiation as observed 7 days after i.p. MPTP injection. Together, our data demonstrate that MPTP-induced degeneration of DA neurons and the subsequent hippocampal DA depletion alter NMDA receptor-mediated synaptic transmission and activity-dependent synaptic plasticity. - Highlights: > I.p. MPTP-injection mediates death of dopaminergic neurons. > I.p. MPTP-injection depletes DA and DOPAC in striatum and hippocampus. > I.p. MPTP-injection does not alter basal synaptic transmission. > Reduction of LTP and enhancement of LTD after i.p. MPTP-injection. > Attenuation of NMDA-receptors mediated f

  14. Nitric Oxide Mediates Activity-Dependent Plasticity of Retinal Bipolar Cell Output via S-Nitrosylation

    PubMed Central

    Tooker, Ryan E.; Lipin, Mikhail Y.; Leuranguer, Valerie; Rozsa, Eva; Bramley, Jayne R.; Harding, Jacqueline L.; Reynolds, Melissa M.

    2013-01-01

    Coding a wide range of light intensities in natural scenes poses a challenge for the retina: adaptation to bright light should not compromise sensitivity to dim light. Here we report a novel form of activity-dependent synaptic plasticity, specifically, a “weighted potentiation” that selectively increases output of Mb-type bipolar cells in the goldfish retina in response to weak inputs but leaves the input–output ratio for strong stimuli unaffected. In retinal slice preparation, strong depolarization of bipolar terminals significantly lowered the threshold for calcium spike initiation, which originated from a shift in activation of voltage-gated calcium currents (ICa) to more negative potentials. The process depended upon glutamate-evoked retrograde nitric oxide (NO) signaling as it was eliminated by pretreatment with an NO synthase blocker, TRIM. The NO-dependent ICa modulation was cGMP independent but could be blocked by N-ethylmaleimide (NEM), indicating that NO acted via an S-nitrosylation mechanism. Importantly, the NO action resulted in a weighted potentiation of Mb output in response to small (≤−30 mV) depolarizations. Coincidentally, light flashes with intensity ≥2.4 × 108 photons/cm2/s lowered the latency of scotopic (≤2.4 × 108 photons/cm2/s) light-evoked calcium spikes in Mb axon terminals in an NEM-sensitive manner, but light responses above cone threshold (≥3.5 × 109 photons/cm2/s) were unaltered. Under bright scotopic/mesopic conditions, this novel form of Mb output potentiation selectively amplifies dim retinal inputs at Mb → ganglion cell synapses. We propose that this process might counteract decreases in retinal sensitivity during light adaptation by preventing the loss of visual information carried by dim scotopic signals. PMID:24305814

  15. White Matter Damage Impairs Adaptive Recovery More than Cortical Damage in an in silico Model of Activity-Dependent Plasticity

    PubMed Central

    Follett, Pamela L.; Roth, Cassandra; Follett, David; Dammann, Olaf

    2013-01-01

    Little is understood of how damaged white matter interacts with developmental plasticity. We propose that computational neuroscience methods are underutilized in this problem. In this paper we present a non-deterministic, in silico model of activity-dependent plasticity. Using this model we compared the impact of neuronal cell loss or axonal dysfunction on the ability of the system to generate, maintain, and recover synapses. The results suggest the axonal dysfunction seen in white matter injury is a greater burden to adaptive plasticity and recovery than is the neuronal loss of cortical injury. Better understanding of the interaction between features of preterm brain injury and developmental plasticity is an essential component for improving recovery. PMID:19745092

  16. Activity-dependent signaling: influence on plasticity in circuits controlling fear-related behavior

    PubMed Central

    Hill, Julia L; Martinowich, Keri

    2015-01-01

    Fear regulation is impaired in anxiety and trauma-related disorders. Patients experience heightened fear expression and reduced ability to extinguish fear memories. Because fear regulation is abnormal in these disorders and extinction recapitulates current treatment strategies, understanding the underlying mechanisms is vital for developing new treatments. This is critical because although extinction-based exposure therapy is a mainstay of treatment, relapse is common. We examine recent findings describing changes in network activity and functional connectivity within limbic circuits during fear regulation, and explore how activity-dependent signaling contributes to the neural activity patterns that control fear and anxiety. We review the role of the prototypical activity-dependent molecule, brain-derived neurotrophic factor (BDNF), whose signaling has been critically linked to regulation of fear behavior. PMID:26485574

  17. Molecular Mechanisms Underlying Activity-Dependent GABAergic Synapse Development and Plasticity and Its Implications for Neurodevelopmental Disorders

    PubMed Central

    Chattopadhyaya, Bidisha

    2011-01-01

    GABAergic interneurons are critical for the normal function and development of neural circuits, and their dysfunction is implicated in a large number of neurodevelopmental disorders. Experience and activity-dependent mechanisms play an important role in GABAergic circuit development, also recent studies involve a number of molecular players involved in the process. Emphasizing the molecular mechanisms of GABAergic synapse formation, in particular basket cell perisomatic synapses, this paper draws attention to the links between critical period plasticity, GABAergic synapse maturation, and the consequences of its dysfunction on the development of the nervous system. PMID:21826279

  18. Distinct and developmentally regulated activity-dependent plasticity at descending glutamatergic synapses on flexor and extensor motoneurons

    PubMed Central

    Lenschow, Constanze; Cazalets, Jean-René; Bertrand, Sandrine S.

    2016-01-01

    Activity-dependent synaptic plasticity (ADSP) is paramount to synaptic processing and maturation. However, identifying the ADSP capabilities of the numerous synapses converging onto spinal motoneurons (MNs) remain elusive. Using spinal cord slices from mice at two developmental stages, 1–4 and 8–12 postnatal days (P1–P4; P8–P12), we found that high-frequency stimulation of presumed reticulospinal neuron axons in the ventrolateral funiculus (VLF) induced either an NMDA receptor-dependent-long-term depression (LTD), a short-term depression (STD) or no synaptic modulation in limb MNs. Our study shows that P1–P4 cervical MNs expressed the same plasticity profiles as P8–P12 lumbar MNs rather than P1–P4 lumbar MNs indicating that ADSP expression at VLF-MN synapses is linked to the rostrocaudal development of spinal motor circuitry. Interestingly, we observed that the ADSP expressed at VLF-MN was related to the functional flexor or extensor MN subtype. Moreover, heterosynaptic plasticity was triggered in MNs by VLF axon tetanisation at neighbouring synapses not directly involved in the plasticity induction. ADSP at VLF-MN synapses specify differential integrative synaptic processing by flexor and extensor MNs and could contribute to the maturation of spinal motor circuits and developmental acquisition of weight-bearing locomotion. PMID:27329279

  19. Environment- and activity-dependent dopamine neurotransmitter plasticity in the adult substantia nigra.

    PubMed

    Aumann, Tim D

    2016-04-01

    The ability of neurons to change the amount or type of neurotransmitter they use, or 'neurotransmitter plasticity', is an emerging new form of adult brain plasticity. For example, it has recently been shown that neurons in the adult rat hypothalamus up- or down-regulate dopamine (DA) neurotransmission in response to the amount of light the animal receives (photoperiod), and that this in turn affects anxiety- and depressive-like behaviors (Dulcis et al., 2013). In this Chapter I consolidate recent evidence from my laboratory suggesting neurons in the adult mouse substantia nigra pars compacta (SNc) also undergo DA neurotransmitter plasticity in response to persistent changes in their electrical activity, including that driven by the mouse's environment or behavior. Specifically, we have shown that the amounts of tyrosine hydroxylase (TH, the rate-limiting enzyme in DA synthesis) gene promoter activity, TH mRNA and TH protein in SNc neurons increases or decreases after ∼20h of altered electrical activity. Also, infusion of ion-channel agonists or antagonists into the midbrain for 2 weeks results in ∼10% (∼500 neurons) more or fewer TH immunoreactive (TH+) SNc neurons, with no change in the total number of SNc neurons (TH+ and TH-). Targeting ion-channels mediating cell-autonomous pacemaker activity in, or synaptic input and afferent pathways to, SNc neurons are equally effective in this regard. In addition, exposing mice to different environments (sex pairing or environment enrichment) for 1-2 weeks induces ∼10% more or fewer TH+ SNc (and ventral tegmental area or VTA) neurons and this is abolished by concurrent blockade of synaptic transmission in midbrain. Although further research is required to establish SNc (and VTA) DA neurotransmitter plasticity, and to determine whether it alters brain function and behavior, it is an exciting prospect because: (1) It may play important roles in movement, motor learning, reward, motivation, memory and cognition; and (2

  20. Activity-dependent dephosphorylation of paxillin contributed to nociceptive plasticity in spinal cord dorsal horn.

    PubMed

    Wang, Xin-Tai; Zheng, Rui; Suo, Zhan-Wei; Liu, Yan-Ni; Zhang, Zi-Yang; Ma, Zheng-An; Xue, Ye; Xue, Man; Yang, Xian; Hu, Xiao-Dong

    2016-03-01

    The enzymatic activity of protein tyrosine kinase Src is subjected to the regulation by C-terminal Src kinase (CSK) and protein tyrosine phosphatases (PTPs). Aberrant Src activation in the spinal cord dorsal horn is pivotal for the induction and development of nociceptive behavioral sensitization. In this study, we found that paxillin, one of the well-characterized cell adhesion components involved in cell migration and survival, integrated CSK and PTPs' signaling to regulate Src-dependent nociceptive plasticity. Paxillin localized at excitatory glutamatergic synapses in the spinal dorsal horn of mice, and the phosphorylation of Tyr118 on paxillin was necessary to associate with and target CSK at synapses. After peripheral tissue injury, the enhanced neuronal activity stimulated N-methyl-D-aspartate (NMDA) subtype glutamate receptors, which initiated PTPs' signaling to catalyze Tyr118 dephosphorylation. The reduced Tyr118 phosphorylation disrupted paxillin interaction with CSK, leading to the dispersal of CSK out of synapses. With the loss of CSK-mediated inhibition, Src activity was persistently increased. The active Src potentiated the synaptic transmission specifically mediated by GluN2B subunit-containing NMDA receptors. The active Src also facilitated the induction of long-term potentiation of C fiber-evoked field potentials and exaggerated painful responses. In complete Freund's adjuvant-injected mice, viral expression of phosphomimicking paxillin mutant to resume CSK synaptic localization repressed Src hyperactivity. Meanwhile, this phosphomimicking paxillin mutant blunted NMDA receptor-mediated synaptic transmission and alleviated chronic inflammatory pain. These data showed that PTPs-mediated dephosphorylation of paxillin at Tyr118 was involved in the modification of nociceptive plasticity through CSK-Src signaling.

  1. Activity-dependent plasticity improves M1 motor representation and corticospinal tract connectivity.

    PubMed

    Chakrabarty, S; Friel, K M; Martin, J H

    2009-03-01

    Motor cortex (M1) activity between postnatal weeks 5 and 7 is essential for normal development of the corticospinal tract (CST) and visually guided movements. Unilateral reversible inactivation of M1, by intracortical muscimol infusion, during this period permanently impairs development of the normal dorsoventral distribution of CST terminations and visually guided motor skills. These impairments are abrogated if this M1 inactivation is followed by inactivation of the contralateral, initially active M1, from weeks 7 to 11 (termed alternate inactivation). This later period is when the M1 motor representation normally develops. The purpose of this study was to determine the effects of alternate inactivation on the motor representation of the initially inactivated M1. We used intracortical microstimulation to map the left M1 1 to 2 mo after the end of left M1 muscimol infusion. We compared representations in the unilateral inactivation and alternate inactivation groups. Alternate inactivation converted the sparse proximal M1 motor representation produced by unilateral inactivation to a complete and high-resolution proximal-distal representation. The motor map was restored by week 11, the same age that our present and prior studies demonstrated that alternate inactivation restored CST spinal connectivity. Thus M1 motor map developmental plasticity closely parallels plasticity of CST spinal terminations. After alternate inactivation reestablished CST connections and the motor map, an additional 3 wk was required for motor skill recovery. Since motor map recovery preceded behavioral recovery, our findings suggest that the representation is necessary for recovering motor skills, but additional time, or experience, is needed to learn to take advantage of the restored CST connections and motor map.

  2. Opposing Effects of Neuronal Activity on Structural Plasticity

    PubMed Central

    Fauth, Michael; Tetzlaff, Christian

    2016-01-01

    The connectivity of the brain is continuously adjusted to new environmental influences by several activity-dependent adaptive processes. The most investigated adaptive mechanism is activity-dependent functional or synaptic plasticity regulating the transmission efficacy of existing synapses. Another important but less prominently discussed adaptive process is structural plasticity, which changes the connectivity by the formation and deletion of synapses. In this review, we show, based on experimental evidence, that structural plasticity can be classified similar to synaptic plasticity into two categories: (i) Hebbian structural plasticity, which leads to an increase (decrease) of the number of synapses during phases of high (low) neuronal activity and (ii) homeostatic structural plasticity, which balances these changes by removing and adding synapses. Furthermore, based on experimental and theoretical insights, we argue that each type of structural plasticity fulfills a different function. While Hebbian structural changes enhance memory lifetime, storage capacity, and memory robustness, homeostatic structural plasticity self-organizes the connectivity of the neural network to assure stability. However, the link between functional synaptic and structural plasticity as well as the detailed interactions between Hebbian and homeostatic structural plasticity are more complex. This implies even richer dynamics requiring further experimental and theoretical investigations. PMID:27445713

  3. Activity-Dependent p25 Generation Regulates Synaptic Plasticity and Aβ-Induced Cognitive Impairment

    PubMed Central

    Seo, Jinsoo; Giusti-Rodríguez, Paola; Zhou, Ying; Rudenko, Andrii; Cho, Sukhee; Ota, Kristie T.; Park, Christine; Patzke, Holger; Madabhushi, Ram; Pan, Ling; Mungenast, Alison E.; Guan, Ji-Song; Delalle, Ivana; Tsai, Li-Huei

    2015-01-01

    SUMMARY Cyclin-dependent kinase 5 regulates numerous neuronal functions with its activator, p35. Under neurotoxic conditions, p35 undergoes proteolytic cleavage to liberate p25, which has been implicated in various neurodegenerative diseases. Here, we show that p25 is generated following neuronal activity under physiological conditions in a GluN2B- and CaMKIIα-dependent manner. Moreover, we developed a knockin mouse model in which endogenous p35 is replaced with a calpain-resistant mutant p35 (Δp35KI) to prevent p25 generation. The Δp35KI mice exhibit impaired long-term depression and defective memory extinction, likely mediated through persistent GluA1 phosphorylation at Ser845. Finally, crossing the Δp35KI mice with the 5XFAD mouse model of Alzheimer's disease (AD) resulted in an amelioration of β-amyloid (Aβ)-induced synaptic depression and cognitive impairment. Together, these results reveal a physiological role of p25 production in synaptic plasticity and memory and provide new insights into the function of p25 in Aβ-associated neurotoxicity and AD-like pathology. PMID:24725413

  4. Superresolution imaging reveals activity-dependent plasticity of axon morphology linked to changes in action potential conduction velocity.

    PubMed

    Chéreau, Ronan; Saraceno, G Ezequiel; Angibaud, Julie; Cattaert, Daniel; Nägerl, U Valentin

    2017-02-07

    Axons convey information to nearby and distant cells, and the time it takes for action potentials (APs) to reach their targets governs the timing of information transfer in neural circuits. In the unmyelinated axons of hippocampus, the conduction speed of APs depends crucially on axon diameters, which vary widely. However, it is not known whether axon diameters are dynamic and regulated by activity-dependent mechanisms. Using time-lapse superresolution microscopy in brain slices, we report that axons grow wider after high-frequency AP firing: synaptic boutons undergo a rapid enlargement, which is mostly transient, whereas axon shafts show a more delayed and progressive increase in diameter. Simulations of AP propagation incorporating these morphological dynamics predicted bidirectional effects on AP conduction speed. The predictions were confirmed by electrophysiological experiments, revealing a phase of slowed down AP conduction, which is linked to the transient enlargement of the synaptic boutons, followed by a sustained increase in conduction speed that accompanies the axon shaft widening induced by high-frequency AP firing. Taken together, our study outlines a morphological plasticity mechanism for dynamically fine-tuning AP conduction velocity, which potentially has wide implications for the temporal transfer of information in the brain.

  5. D2-like dopamine receptor-mediated modulation of activity-dependent plasticity at GABAergic synapses in the subthalamic nucleus

    PubMed Central

    Baufreton, Jérôme; Bevan, Mark D

    2008-01-01

    Reciprocally connected glutamatergic subthalamic nucleus (STN) and GABAergic external globus pallidus (GP) neurons normally exhibit weakly correlated, irregular activity but following the depletion of dopamine in Parkinson's disease they express more highly correlated, rhythmic bursting activity. Patch clamp recording was used to test the hypothesis that dopaminergic modulation reduces the capability of GABAergic inputs to pattern ‘pathological’ activity in STN neurons. Electrically evoked GABAA receptor-mediated IPSCs exhibited activity-dependent plasticity in STN neurons, i.e. IPSCs evoked at frequencies between 1 and 50 Hz exhibited depression that increased with the frequency of activity. Dopamine, the D2-like dopamine receptor agonist quinpirole and external media containing a low [Ca2+] reduced both the magnitude of IPSCs evoked at 1–50 Hz and synaptic depression at 10–50 Hz. Dopamine/quinpirole also reduced the frequency but not the amplitude of miniature IPSCs recorded in the presence of tetrodotoxin. D1-like and D4 agonists were ineffective and D2/3 but not D4 receptor antagonists reversed the effects of dopamine or quinpirole. Together these data suggest that presynaptic D2/3 dopamine receptors modulate the short-term dynamics of GABAergic transmission in the STN by lowering the initial probability of transmitter release. Simulated GABAA receptor-mediated synaptic conductances representative of control or modulated transmission were then generated in STN neurons using the dynamic clamp technique. Dopamine-modulated transmission was less effective at resetting autonomous activity or generating rebound burst firing than control transmission. The data therefore support the conclusion that dopamine acting at presynaptic D2-like receptors reduces the propensity for GABAergic transmission to generate correlated, bursting activity in STN neurons. PMID:18292127

  6. Reinforced structural plastics

    NASA Technical Reports Server (NTRS)

    Lubowitz, H. R.; Kendrick, W. P.; Jones, J. F.; Thorpe, R. S.; Burns, E. A. (Inventor)

    1972-01-01

    Reinforced polyimide structures are described. Reinforcing materials are impregnated with a suspension of polyimide prepolymer and bonded together by heat and pressure to form a cured, hard-reinforced, polyimide structure.

  7. Three-dimensional EM Structure of an Intact Activator-dependent Transcription Initiation Complex

    SciTech Connect

    Hudson, B.; Quispe, J; Lara-González, S; Kim, Y; Berman, H; Arnold, E; Ebright, R; Lawson, C

    2009-01-01

    We present the experimentally determined 3D structure of an intact activator-dependent transcription initiation complex comprising the Escherichia coli catabolite activator protein (CAP), RNA polymerase holoenzyme (RNAP), and a DNA fragment containing positions -78 to +20 of a Class I CAP-dependent promoter with a CAP site at position -61.5 and a premelted transcription bubble. A 20-{angstrom} electron microscopy reconstruction was obtained by iterative projection-based matching of single particles visualized in carbon-sandwich negative stain and was fitted using atomic coordinate sets for CAP, RNAP, and DNA. The structure defines the organization of a Class I CAP-RNAP-promoter complex and supports previously proposed interactions of CAP with RNAP {alpha} subunit C-terminal domain ({alpha}CTD), interactions of {alpha}CTD with {sigma}70 region 4, interactions of CAP and RNAP with promoter DNA, and phased-DNA-bend-dependent partial wrapping of DNA around the complex. The structure also reveals the positions and shapes of species-specific domains within the RNAP {beta}{prime}, {beta}, and {sigma}70 subunits.

  8. Adaptation of short-term plasticity parameters via error-driven learning may explain the correlation between activity-dependent synaptic properties, connectivity motifs and target specificity

    PubMed Central

    Esposito, Umberto; Giugliano, Michele; Vasilaki, Eleni

    2015-01-01

    The anatomical connectivity among neurons has been experimentally found to be largely non-random across brain areas. This means that certain connectivity motifs occur at a higher frequency than would be expected by chance. Of particular interest, short-term synaptic plasticity properties were found to colocalize with specific motifs: an over-expression of bidirectional motifs has been found in neuronal pairs where short-term facilitation dominates synaptic transmission among the neurons, whereas an over-expression of unidirectional motifs has been observed in neuronal pairs where short-term depression dominates. In previous work we found that, given a network with fixed short-term properties, the interaction between short- and long-term plasticity of synaptic transmission is sufficient for the emergence of specific motifs. Here, we introduce an error-driven learning mechanism for short-term plasticity that may explain how such observed correspondences develop from randomly initialized dynamic synapses. By allowing synapses to change their properties, neurons are able to adapt their own activity depending on an error signal. This results in more rich dynamics and also, provided that the learning mechanism is target-specific, leads to specialized groups of synapses projecting onto functionally different targets, qualitatively replicating the experimental results of Wang and collaborators. PMID:25688203

  9. Ethanol up-regulates nucleus accumbens neuronal activity dependent pentraxin (Narp): implications for alcohol-induced behavioral plasticity.

    PubMed

    Ary, Alexis W; Cozzoli, Debra K; Finn, Deborah A; Crabbe, John C; Dehoff, Marlin H; Worley, Paul F; Szumlinski, Karen K

    2012-06-01

    Neuronal activity dependent pentraxin (Narp) interacts with α-amino-3-hydroxyl-5-methyl-4-isoxazole-propionate (AMPA) glutamate receptors to facilitate excitatory synapse formation by aggregating them at established synapses. Alcohol is well-characterized to influence central glutamatergic transmission, including AMPA receptor function. Herein, we examined the influence of injected and ingested alcohol upon Narp protein expression, as well as basal Narp expression in mouse lines selectively bred for high blood alcohol concentrations under limited access conditions. Alcohol up-regulated accumbens Narp levels, concomitant with increases in levels of the GluR1 AMPA receptor subunit. However, accumbens Narp or GluR1 levels did not vary as a function of selectively bred genotype. We next employed a Narp knock-out (KO) strategy to begin to understand the behavioral relevance of alcohol-induced changes in protein expression in several assays of alcohol reward. Compared to wild-type mice, Narp KO animals: fail to escalate daily intake of high alcohol concentrations under free-access conditions; shift their preference away from high alcohol concentrations with repeated alcohol experience; exhibit a conditioned place-aversion in response to the repeated pairing of 3 g/kg alcohol with a distinct environment and fail to exhibit alcohol-induced locomotor hyperactivity following repeated alcohol treatment. Narp deletion did not influence the daily intake of either food or water, nor did it alter any aspect of spontaneous or alcohol-induced motor activity, including the development of tolerance to its motor-impairing effects with repeated treatment. Taken together, these data indicate that Narp induction, and presumably subsequent aggregation of AMPA receptors, may be important for neuroplasticity within limbic subcircuits mediating or maintaining the rewarding properties of alcohol.

  10. Damage Diagnosis for Elasto-Plastic Structures.

    DTIC Science & Technology

    1986-12-01

    nonsta- tionary. The stiffness matrix is nonlinear to simulate the elasto-plastic behavior of a damaged structure. The stiffness matrix is also random...23 3.2 Small length cut from a beam .... ............... . 24 3.3 Stress-strain curve of elasto-plastic material ...... . 26...excitation. The stiffness matrix is nonlinear to simulate the elasto-plastic behavior of a damaged structure. The stiffness matrix is also random to

  11. Impact of combined prenatal ethanol and prenatal stress exposures on markers of activity-dependent synaptic plasticity in rat dentate gyrus.

    PubMed

    Staples, Miranda C; Porch, Morgan W; Savage, Daniel D

    2014-09-01

    Prenatal ethanol exposure and prenatal stress can each cause long-lasting deficits in hippocampal synaptic plasticity and disrupt learning and memory processes. However, the mechanisms underlying these perturbations following a learning event are still poorly understood. We examined the effects of prenatal ethanol exposure and prenatal stress exposure, either alone or in combination, on the cytosolic expression of activity-regulated cytoskeletal (ARC) protein and the synaptosomal expression of AMPA-glutamate receptor subunits (GluA1 and GluA2) in dentate gyrus of female adult offspring under baseline conditions and after 2-trial trace conditioning (TTTC). Surprisingly, baseline cytoplasmic ARC expression was significantly elevated in both prenatal treatment groups. In contrast, synaptosomal GluA1 receptor subunit expression was decreased in both prenatal treatment groups. GluA2 subunit expression was elevated in the prenatal stress group. TTTC did not alter ARC levels compared to an unpaired behavioral control (UPC) group in any of the 4 prenatal treatment groups. In contrast, TTTC significantly elevated both synaptosomal GluA1 and GluA2 subunit expression relative to the UPC group in control offspring, an effect that was not observed in any of the other 3 prenatal treatment groups. Given ARC's role in regulating synaptosomal AMPA receptors, these results suggest that prenatal ethanol-induced or prenatal stress exposure-induced increases in baseline ARC levels could contribute to reductions in both baseline and activity-dependent changes in AMPA receptors in a manner that diminishes the role of AMPA receptors in dentate gyrus synaptic plasticity and hippocampal-sensitive learning.

  12. Impact of Combined Prenatal Ethanol and Prenatal Stress Exposures on Markers of Activity-Dependent Synaptic Plasticity in Rat Dentate Gyrus

    PubMed Central

    Staples, Miranda C.; Porch, Morgan W.; Savage, Daniel D.

    2014-01-01

    Prenatal ethanol exposure and prenatal stress can each cause long-lasting deficits in hippocampal synaptic plasticity and disrupt learning and memory processes. However, the mechanisms underlying these perturbations following a learning event are still poorly understood. We examined the effects of prenatal ethanol exposure and prenatal stress exposure, either alone or in combination, on the cytosolic expression of activity-regulated cytoskeletal (ARC) protein and the synaptosomal expression of AMPA-glutamate receptor subunits (GluA1 and GluA2) in dentate gyrus of female adult offspring under baseline conditions and after 2-trial trace conditioning (TTTC). Surprisingly, baseline cytoplasmic ARC expression was significantly elevated in both prenatal treatment groups. In contrast, synaptosomal GluA1 receptor subunit expression was decreased in both prenatal treatment groups. GluA2 subunit expression was elevated in the prenatal stress group. TTTC did not alter ARC levels compared to an unpaired behavioral control (UPC) group in any of the 4 prenatal treatment groups. In contrast, TTTC significantly elevated both synaptosomal GluA1 and GluA2 subunit expression relative to the UPC group in control offspring, an effect that was not observed in any of the other 3 prenatal treatment groups. Given ARC's role in regulating synaptosomal AMPA receptors, these results suggest that prenatal ethanol-induced or prenatal stress exposure-induced increases in baseline ARC levels could contribute to reductions in both baseline and activity-dependent changes in AMPA receptors in a manner that diminishes the role of AMPA receptors in dentate gyrus synaptic plasticity and hippocampal-sensitive learning. PMID:25129673

  13. The miRNA Pathway Controls Rapid Changes in Activity-Dependent Synaptic Structure at the Drosophila melanogaster Neuromuscular Junction

    PubMed Central

    Nesler, Katherine R.; Sand, Robert I.; Symmes, Breanna A.; Pradhan, Sarala J.; Boin, Nathan G.; Laun, Anna E.; Barbee, Scott A.

    2013-01-01

    It is widely accepted that long-term changes in synapse structure and function are mediated by rapid activity-dependent gene transcription and new protein synthesis. A growing amount of evidence suggests that the microRNA (miRNA) pathway plays an important role in coordinating these processes. Despite recent advances in this field, there remains a critical need to identify specific activity-regulated miRNAs as well as their key messenger RNA (mRNA) targets. To address these questions, we used the larval Drosophila melanogaster neuromuscular junction (NMJ) as a model synapse in which to identify novel miRNA-mediated mechanisms that control activity-dependent synaptic growth. First, we developed a screen to identify miRNAs differentially regulated in the larval CNS following spaced synaptic stimulation. Surprisingly, we identified five miRNAs (miRs-1, -8, -289, -314, and -958) that were significantly downregulated by activity. Neuronal misexpression of three miRNAs (miRs-8, -289, and -958) suppressed activity-dependent synaptic growth suggesting that these miRNAs control the translation of biologically relevant target mRNAs. Functional annotation cluster analysis revealed that putative targets of miRs-8 and -289 are significantly enriched in clusters involved in the control of neuronal processes including axon development, pathfinding, and growth. In support of this, miR-8 regulated the expression of a wingless 3′UTR (wg 3′ untranslated region) reporter in vitro. Wg is an important presynaptic regulatory protein required for activity-dependent axon terminal growth at the fly NMJ. In conclusion, our results are consistent with a model where key activity-regulated miRNAs are required to coordinate the expression of genes involved in activity-dependent synaptogenesis. PMID:23844193

  14. Structural plasticity and reorganisation in chronic pain.

    PubMed

    Kuner, Rohini; Flor, Herta

    2016-12-15

    Chronic pain is not simply a temporal continuum of acute pain. Studies on functional plasticity in neural circuits of pain have provided mechanistic insights and linked various modulatory factors to a change in perception and behaviour. However, plasticity also occurs in the context of structural remodelling and reorganisation of synapses, cells and circuits, potentially contributing to the long-term nature of chronic pain. This Review discusses maladaptive structural plasticity in neural circuits of pain, spanning multiple anatomical and spatial scales in animal models and human patients, and addresses key questions on structure-function relationships.

  15. Stability of soil microbial structure and activity depends on microbial diversity.

    PubMed

    Tardy, Vincent; Mathieu, Olivier; Lévêque, Jean; Terrat, Sébastien; Chabbi, Abad; Lemanceau, Philippe; Ranjard, Lionel; Maron, Pierre-Alain

    2014-04-01

    Despite the central role of microbes in soil processes, empirical evidence concerning the effect of their diversity on soil stability remains controversial. Here, we addressed the ecological insurance hypothesis by examining the stability of microbial communities along a gradient of soil microbial diversity in response to mercury pollution and heat stress. Diversity was manipulated by dilution extinction approach. Structural and functional stabilities of microbial communities were assessed from patterns of genetic structure and soil respiration after the stress. Dilution led to the establishment of a consistent diversity gradient, as revealed by 454 sequencing of ribosomal genes. Diversity stability was enhanced in species-rich communities whatever the stress whereas functional stability was improved with increasing diversity after heat stress, but not after mercury pollution. This discrepancy implies that the relevance of ecological insurance for soil microbial communities might depend on the type of stress. Our results also suggest that the significance of microbial diversity for soil functional stability might increase with available soil resources. This could have strong repercussions in the current 'global changes' context because it suggests that the combined increased frequencies of extreme climatic events, nutrient loading and biotic exploitation may amplify the functional consequences of diversity decrease.

  16. Structural and Functional Plasticity at the Axon Initial Segment

    PubMed Central

    Yamada, Rei; Kuba, Hiroshi

    2016-01-01

    The axon initial segment (AIS) is positioned between the axonal and somato-dendritic compartments and plays a pivotal role in triggering action potentials (APs) and determining neuronal output. It is now widely accepted that structural properties of the AIS, such as length and/or location relative to the soma, change in an activity-dependent manner. This structural plasticity of the AIS is known to be crucial for homeostatic control of neuronal excitability. However, it is obvious that the impact of the AIS on neuronal excitability is critically dependent on the biophysical properties of the AIS, which are primarily determined by the composition and characteristics of ion channels in this domain. Moreover, these properties can be altered via phosphorylation and/or redistribution of the channels. Recently, studies in auditory neurons showed that alterations in the composition of voltage-gated K+ (Kv) channels at the AIS coincide with elongation of the AIS, thereby enhancing the neuronal excitability, suggesting that the interaction between structural and functional plasticities of the AIS is important in the control of neuronal excitability. In this review, we will summarize the current knowledge regarding structural and functional alterations of the AIS and discuss how they interact and contribute to regulating the neuronal output. PMID:27826229

  17. Nanoscale analysis of structural synaptic plasticity

    PubMed Central

    Bourne, Jennifer N.; Harris, Kristen M.

    2011-01-01

    In the 1950’s, transmission electron microscopy was first used to reveal the diversity in synaptic structure and composition in the central nervous system [1;2]. Since then, visualization and reconstruction of serial thin sections have provided three-dimensional contexts in which to understand how synapses are modified with plasticity, learning, and sensory input [3–17]. Three-dimensional reconstruction from serial section electron microscopy (ssEM) has proven invaluable for the comprehensive analysis of structural synaptic plasticity. It has provided the needed nanometer resolution to localize and measure key subcellular structures, such as the postsynaptic density (PSD) and presynaptic vesicles which define a synapse, polyribosomes as sites of local protein synthesis, smooth endoplasmic reticulum (SER) for local regulation of calcium and trafficking of membrane proteins, endosomes for recycling, and fine astroglial processes at the perimeter of some synapses. Thus, ssEM is an essential tool for nanoscale analysis of the cell biological and anatomical modifications that underlie changes in synaptic strength. Here we discuss several important issues associated with interpreting the functional significance of structural synaptic plasticity, especially during long-term potentiation, a widely studied cellular model of learning and memory. PMID:22088391

  18. Plastics as structural materials for aircraft

    NASA Technical Reports Server (NTRS)

    Kline, G M

    1937-01-01

    The purpose here is to consider the mechanical characteristics of reinforced phenol-formaldehyde resin as related to its use as structural material for aircraft. Data and graphs that have appeared in the literature are reproduced to illustrate the comparative behavior of plastics and materials commonly used in aircraft construction. Materials are characterized as to density, static strength, modulus of elasticity, resistance to long-time loading, strength under repeated impact, energy absorption, corrosion resistance, and ease of fabrication.

  19. Structural Synaptic Plasticity Has High Memory Capacity and Can Explain Graded Amnesia, Catastrophic Forgetting, and the Spacing Effect

    PubMed Central

    Knoblauch, Andreas; Körner, Edgar; Körner, Ursula; Sommer, Friedrich T.

    2014-01-01

    Although already William James and, more explicitly, Donald Hebb's theory of cell assemblies have suggested that activity-dependent rewiring of neuronal networks is the substrate of learning and memory, over the last six decades most theoretical work on memory has focused on plasticity of existing synapses in prewired networks. Research in the last decade has emphasized that structural modification of synaptic connectivity is common in the adult brain and tightly correlated with learning and memory. Here we present a parsimonious computational model for learning by structural plasticity. The basic modeling units are “potential synapses” defined as locations in the network where synapses can potentially grow to connect two neurons. This model generalizes well-known previous models for associative learning based on weight plasticity. Therefore, existing theory can be applied to analyze how many memories and how much information structural plasticity can store in a synapse. Surprisingly, we find that structural plasticity largely outperforms weight plasticity and can achieve a much higher storage capacity per synapse. The effect of structural plasticity on the structure of sparsely connected networks is quite intuitive: Structural plasticity increases the “effectual network connectivity”, that is, the network wiring that specifically supports storage and recall of the memories. Further, this model of structural plasticity produces gradients of effectual connectivity in the course of learning, thereby explaining various cognitive phenomena including graded amnesia, catastrophic forgetting, and the spacing effect. PMID:24858841

  20. Musings on the wanderer: what's new in our understanding of vago-vagal reflexes? III. Activity-dependent plasticity in vago-vagal reflexes controlling the stomach.

    PubMed

    Travagli, R Alberto; Hermann, Gerlinda E; Browning, Kirsteen N; Rogers, Richard C

    2003-02-01

    Vago-vagal reflex circuits modulate digestive functions from the oral cavity to the transverse colon. Previous articles in this series have described events at the level of the sensory receptors encoding the peripheral stimuli, the transmission of information in the afferent vagus, and the conversion of this data within the dorsal vagal complex (DVC) to impulses in the preganglionic efferents. The control by vagal efferents of the postganglionic neurons impinging on the glands and smooth muscles of the target organs has also been illustrated. Here we focus on some of the mechanisms by which these apparently static reflex circuits can be made quite plastic as a consequence of the action of modulatory inputs from other central nervous system sources. A large body of evidence has shown that the neuronal elements that constitute these brain stem circuits have nonuniform properties and function differently according to status of their target organs and the level of activity in critical modulatory inputs. We propose that DVC circuits undergo a certain amount of short-term plasticity that allows the brain stem neuronal elements to act in harmony with neural systems that control behavioral and physiological homeostasis.

  1. Structural Plasticity Denoises Responses and Improves Learning Speed

    PubMed Central

    Spiess, Robin; George, Richard; Cook, Matthew; Diehl, Peter U.

    2016-01-01

    Despite an abundance of computational models for learning of synaptic weights, there has been relatively little research on structural plasticity, i.e., the creation and elimination of synapses. Especially, it is not clear how structural plasticity works in concert with spike-timing-dependent plasticity (STDP) and what advantages their combination offers. Here we present a fairly large-scale functional model that uses leaky integrate-and-fire neurons, STDP, homeostasis, recurrent connections, and structural plasticity to learn the input encoding, the relation between inputs, and to infer missing inputs. Using this model, we compare the error and the amount of noise in the network's responses with and without structural plasticity and the influence of structural plasticity on the learning speed of the network. Using structural plasticity during learning shows good results for learning the representation of input values, i.e., structural plasticity strongly reduces the noise of the response by preventing spikes with a high error. For inferring missing inputs we see similar results, with responses having less noise if the network was trained using structural plasticity. Additionally, using structural plasticity with pruning significantly decreased the time to learn weights suitable for inference. Presumably, this is due to the clearer signal containing less spikes that misrepresent the desired value. Therefore, this work shows that structural plasticity is not only able to improve upon the performance using STDP without structural plasticity but also speeds up learning. Additionally, it addresses the practical problem of limited resources for connectivity that is not only apparent in the mammalian neocortex but also in computer hardware or neuromorphic (brain-inspired) hardware by efficiently pruning synapses without losing performance. PMID:27660610

  2. The molecular interfacial structure and plasticizer migration behavior of "green" plasticized poly(vinyl chloride).

    PubMed

    Zhang, Xiaoxian; Li, Yaoxin; Hankett, Jeanne M; Chen, Zhan

    2015-02-14

    Tributyl acetyl citrate (TBAC), a widely-used "green" plasticizer, has been extensively applied in products for daily use. In this paper, a variety of analytical tools including sum frequency generation vibrational spectroscopy (SFG), coherent anti-Stokes Raman spectroscopy (CARS), contact angle goniometry (CA), and Fourier transform infrared spectroscopy (FTIR) were applied together to investigate the molecular structures of TBAC plasticized poly(vinyl chloride) (PVC) and the migration behavior of TBAC from PVC-TBAC mixtures into water. We comprehensively examine the effects of oxygen and argon plasma treatments on the surface structures of PVC-TBAC thin films containing various bulk percentages of plasticizers and the leaching behavior of TBAC into water. It was found that TBAC is a relatively stable PVC plasticizer compared to traditional non-covalent plasticizers but is also surface active. Oxygen plasma treatment increased the hydrophilicity of TBAC-PVC surfaces, but did not enhance TBAC leaching. However, argon plasma treatment greatly enhanced the leaching of TBAC molecules from PVC plastics to water. Based on our observations, we believe that oxygen plasma treatment could be applied to TBAC plasticized PVC products to enhance surface hydrophilicity for improving the biocompatibility and antibacterial properties of PVC products. The structural information obtained in this study will ultimately facilitate a molecular level understanding of plasticized polymers, aiding in the design of PVC materials with improved properties.

  3. Structure, function, and plasticity of GABA transporters

    PubMed Central

    Scimemi, Annalisa

    2014-01-01

    GABA transporters belong to a large family of neurotransmitter:sodium symporters. They are widely expressed throughout the brain, with different levels of expression in different brain regions. GABA transporters are present in neurons and in astrocytes and their activity is crucial to regulate the extracellular concentration of GABA under basal conditions and during ongoing synaptic events. Numerous efforts have been devoted to determine the structural and functional properties of GABA transporters. There is also evidence that the expression of GABA transporters on the cell membrane and their lateral mobility can be modulated by different intracellular signaling cascades. The strength of individual synaptic contacts and the activity of entire neuronal networks may be finely tuned by altering the density, distribution and diffusion rate of GABA transporters within the cell membrane. These findings are intriguing because they suggest the existence of complex regulatory systems that control the plasticity of GABAergic transmission in the brain. Here we review the current knowledge on the structural and functional properties of GABA transporters and highlight the molecular mechanisms that alter the expression and mobility of GABA transporters at central synapses. PMID:24987330

  4. Experience-dependent structural synaptic plasticity in the mammalian brain.

    PubMed

    Holtmaat, Anthony; Svoboda, Karel

    2009-09-01

    Synaptic plasticity in adult neural circuits may involve the strengthening or weakening of existing synapses as well as structural plasticity, including synapse formation and elimination. Indeed, long-term in vivo imaging studies are beginning to reveal the structural dynamics of neocortical neurons in the normal and injured adult brain. Although the overall cell-specific morphology of axons and dendrites, as well as of a subpopulation of small synaptic structures, are remarkably stable, there is increasing evidence that experience-dependent plasticity of specific circuits in the somatosensory and visual cortex involves cell type-specific structural plasticity: some boutons and dendritic spines appear and disappear, accompanied by synapse formation and elimination, respectively. This Review focuses on recent evidence for such structural forms of synaptic plasticity in the mammalian cortex and outlines open questions.

  5. Hebbian Wiring Plasticity Generates Efficient Network Structures for Robust Inference with Synaptic Weight Plasticity

    PubMed Central

    Hiratani, Naoki; Fukai, Tomoki

    2016-01-01

    In the adult mammalian cortex, a small fraction of spines are created and eliminated every day, and the resultant synaptic connection structure is highly nonrandom, even in local circuits. However, it remains unknown whether a particular synaptic connection structure is functionally advantageous in local circuits, and why creation and elimination of synaptic connections is necessary in addition to rich synaptic weight plasticity. To answer these questions, we studied an inference task model through theoretical and numerical analyses. We demonstrate that a robustly beneficial network structure naturally emerges by combining Hebbian-type synaptic weight plasticity and wiring plasticity. Especially in a sparsely connected network, wiring plasticity achieves reliable computation by enabling efficient information transmission. Furthermore, the proposed rule reproduces experimental observed correlation between spine dynamics and task performance. PMID:27303271

  6. Evaluating Tools for Live Imaging of Structural Plasticity at the Axon Initial Segment

    PubMed Central

    Dumitrescu, Adna S.; Evans, Mark D.; Grubb, Matthew S.

    2016-01-01

    The axon initial segment (AIS) is a specialized neuronal compartment involved in the maintenance of axo-dendritic polarity and in the generation of action potentials. It is also a site of significant structural plasticity—manipulations of neuronal activity in vitro and in vivo can produce changes in AIS position and/or size that are associated with alterations in intrinsic excitability. However, to date all activity-dependent AIS changes have been observed in experiments carried out on fixed samples, offering only a snapshot, population-wide view of this form of plasticity. To extend these findings by following morphological changes at the AIS of individual neurons requires reliable means of labeling the structure in live preparations. Here, we assessed five different immunofluorescence-based and genetically-encoded tools for live-labeling the AIS of dentate granule cells (DGCs) in dissociated hippocampal cultures. We found that an antibody targeting the extracellular domain of neurofascin provided accurate live label of AIS structure at baseline, but could not follow rapid activity-dependent changes in AIS length. Three different fusion constructs of GFP with full-length AIS proteins also proved unsuitable: while neurofascin-186-GFP and NaVβ4-GFP did not localize to the AIS in our experimental conditions, overexpressing 270kDa-AnkyrinG-GFP produced abnormally elongated AISs in mature neurons. In contrast, a genetically-encoded construct consisting of a voltage-gated sodium channel intracellular domain fused to yellow fluorescent protein (YFP-NaVII–III) fulfilled all of our criteria for successful live AIS label: this construct specifically localized to the AIS, accurately revealed plastic changes at the structure within hours, and, crucially, did not alter normal cell firing properties. We therefore recommend this probe for future studies of live AIS plasticity in vitro and in vivo. PMID:27932952

  7. Structural features of plastic deformation in bulk metallic glasses

    SciTech Connect

    Scudino, S. Shakur Shahabi, H.; Stoica, M.; Kühn, U.; Kaban, I.; Escher, B.; Eckert, J.; Vaughan, G. B. M.

    2015-01-19

    Spatially resolved strain maps of a plastically deformed bulk metallic glass (BMG) have been created by using high-energy X-ray diffraction. The results reveal that plastic deformation creates a spatially heterogeneous atomic arrangement, consisting of strong compressive and tensile strain fields. In addition, significant shear strain is introduced in the samples. The analysis of the eigenvalues and eigenvectors of the strain tensor indicates that considerable structural anisotropy occurs in both the magnitude and direction of the strain. These features are in contrast to the behavior observed in elastically deformed BMGs and represent a distinctive structural sign of plastic deformation in metallic glasses.

  8. A computer program for cyclic plasticity and structural fatigue analysis

    NASA Technical Reports Server (NTRS)

    Kalev, I.

    1980-01-01

    A computerized tool for the analysis of time independent cyclic plasticity structural response, life to crack initiation prediction, and crack growth rate prediction for metallic materials is described. Three analytical items are combined: the finite element method with its associated numerical techniques for idealization of the structural component, cyclic plasticity models for idealization of the material behavior, and damage accumulation criteria for the fatigue failure.

  9. Cyclic plasticity and failure of structural components

    NASA Technical Reports Server (NTRS)

    Kalev, I.

    1980-01-01

    An analytical approach for low-cycle fatigue prediction is presented. The approach combines a cyclic plasticity model with the finite element method and a damage accumulation criterion for ductile metals. The cyclic plasticity model is based on the concept of the combination of several yield surfaces. The surfaces are related to the material uniaxial stress-strain curve idealized by piecewise linear segments. The damage criterion is based on the Coffin-Manson formulae modified for the mean stress variation effect. It is extended to the multiaxial varying stress-strain field and applied for both the crack initiation and the crack growth processes. The stable slow crack growth rate is approximated by the damage accumulation gradient computed from the cracked finite element models. This procedure requires fatigue testing data of only smooth specimens under constant strain amplitudes. The present approach is illustrated by numerical examples of an aircraft wing stiffened panel subjected to compression, which causes material yielding and residual tension.

  10. Structural basis of activation-dependent binding of ligand-mimetic antibody AL-57 to integrin LFA-1

    SciTech Connect

    Zhang, Hongmin; Liu, Jin-huan; Yang, Wei; Springer, Timothy; Shimaoka, Motomu; Wang, Jia-huai

    2010-09-21

    The activity of integrin LFA-1 ({alpha}{sub L}{beta}{sub 2}) to its ligand ICAM-1 is regulated through the conformational changes of its ligand-binding domain, the I domain of {alpha}{sub L} chain, from an inactive, low-affinity closed form (LA), to an intermediate-affinity form (IA), and then finally, to a high-affinity open form (HA). A ligand-mimetic human monoclonal antibody AL-57 (activated LFA-1 clone 57) was identified by phage display to specifically recognize the affinity-upregulated I domain. Here, we describe the crystal structures of the Fab fragment of AL-57 in complex with IA, as well as in its unligated form. We discuss the structural features conferring AL-57's strong selectivity for the high affinity, open conformation of the I domain. The AL-57-binding site overlaps the ICAM-1 binding site on the I domain. Furthermore, an antibody Asp mimics an ICAM Glu by forming a coordination to the metal-ion dependent adhesion site (MIDAS). The structure also reveals better shape complementarity and a more hydrophobic interacting interface in AL-57 binding than in ICAM-1 binding. The results explain AL-57's antagonistic mimicry of LFA-1's natural ligands, the ICAM molecules.

  11. Structurally simplified biphenyl combretastatin A4 derivatives retain in vitro anti-cancer activity dependent on mitotic arrest

    PubMed Central

    Tarade, Daniel; Ma, Dennis; Pignanelli, Christopher; Mansour, Fadi; Simard, Daniel; van den Berg, Sean; Gauld, James; McNulty, James; Pandey, Siyaram

    2017-01-01

    The cis-stilbene, combretastatin A4 (CA4), is a potent microtubule targeting and vascular damaging agent. Despite promising results at the pre-clinical level and extensive clinical evaluation, CA4 has yet to be approved for therapeutic use. One impediment to the development of CA4 is an inherent conformational instability about the ethylene linker, which joins two aromatic rings. We have previously published preliminary data regarding structurally simplified biphenyl derivatives of CA4, lacking an ethylene linker, which retain anti-proliferative and pro-apoptotic activity, albeit at higher doses. Our current study provides a more comprehensive evaluation regarding the anti-proliferative and pro-apoptotic properties of biphenyl CA4 derivatives in both 2D and 3D cancerous and non-cancerous cell models. Computational analysis has revealed that cytotoxicity of CA4 and biphenyl analogues correlates with predicted tubulin affinity. Additional mechanistic evaluation of the biphenyl derivatives found that their anti-cancer activity is dependent on prolonged mitotic arrest, in a similar manner to CA4. Lastly, we have shown that cancer cells deficient in the extrinsic pathway of apoptosis experience delayed cell death following treatment with CA4 or analogues. Biphenyl derivatives of CA4 represent structurally simplified analogues of CA4, which retain a similar mechanism of action. The biphenyl analogues warrant in vivo examination to evaluate their potential as vascular damaging agents. PMID:28253265

  12. Structural and Functional Plasticity in the Maternal Brain Circuitry

    ERIC Educational Resources Information Center

    Pereira, Mariana

    2016-01-01

    Parenting recruits a distributed network of brain structures (and neuromodulators) that coordinates caregiving responses attuned to the young's affect, needs, and developmental stage. Many of these structures and connections undergo significant structural and functional plasticity, mediated by the interplay between maternal hormones and social…

  13. Enhancement of Photo-Oxidation Activities Depending on Structural Distortion of Fe-Doped TiO2 Nanoparticles

    NASA Astrophysics Data System (ADS)

    Kim, Yeonwoo; Yang, Sena; Jeon, Eun Hee; Baik, Jaeyoon; Kim, Namdong; Kim, Hyun Sung; Lee, Hangil

    2016-01-01

    To design a high-performance photocatalytic system with TiO2, it is necessary to reduce the bandgap and enhance the absorption efficiency. The reduction of the bandgap to the visible range was investigated with reference to the surface distortion of anatase TiO2 nanoparticles induced by varying Fe doping concentrations. Fe-doped TiO2 nanoparticles (Fe@TiO2) were synthesized by a hydrothermal method and analyzed by various surface analysis techniques such as transmission electron microscopy, Raman spectroscopy, X-ray diffraction, scanning transmission X-ray microscopy, and high-resolution photoemission spectroscopy. We observed that Fe doping over 5 wt.% gave rise to a distorted structure, i.e., Fe2Ti3O9, indicating numerous Ti3+ and oxygen-vacancy sites. The Ti3+ sites act as electron trap sites to deliver the electron to O2 as well as introduce the dopant level inside the bandgap, resulting in a significant increase in the photocatalytic oxidation reaction of thiol (-SH) of 2-aminothiophenol to sulfonic acid (-SO3H) under ultraviolet and visible light illumination.

  14. Evaluation of engineering plastic for rollover protective structure (ROPS) mounting.

    PubMed

    Comer, R S; Ayers, P D; Liu, J

    2007-04-01

    Agriculture has one of the highest fatality rates of any industry in America. Tractor rollovers are a significant contributor to the high death rate. Rollover protective structures (ROPS) have helped lower these high fatality rates on full-size tractors. However, a large number of older tractors still do not use ROPS due to the difficulty of designing and creating a mounting structure. To help reduce this difficulty, engineering plastics were evaluated for use in a ROPS mounting structure on older tractors. The use of engineering plastics around axle housings could provide a uniform mounting configuration as well as lower costs for aftermarket ROPS. Various plastics were examined through shear testing, scale model testing, and compressive strength testing. Once a material was chosen based upon strength and cost, full-scale testing of the plastic's strength on axle housings was conducted. Finally, a mounting structure was tested in static ROPS tests, and field upset tests were performed in accordance with SAE Standard J2194. Initial tests revealed that the ROPS mounting structure and axle housing combination had higher torsional strength with less twisting than the axle housing alone. An engineering plastic ROPS mounting structure was easily successful in withstanding the forces applied during the static longitudinal and lateral ROPS tests. Field upset testing revealed that the mounting structure could withstand the impact loads seen during actual upsets without a failure. During both static testing and field upset testing, no permanent twisting of the mounting structure was found. Engineering plastic could therefore be a viable option for a universal ROPS mounting structure for older tractors.

  15. Structural Signature of Plastic Deformation in Metallic Glasses

    NASA Astrophysics Data System (ADS)

    Peng, H. L.; Li, M. Z.; Wang, W. H.

    2011-04-01

    The structure feature of a model CuZr metallic glass during deformation is investigated by molecular dynamics simulations. A spatially heterogeneous irreversible rearrangement is observed in terms of nonaffine displacement. We find that regions with smaller nonaffine displacement have more Voronoi pentagons, while in those with larger nonaffine displacement other types of faces are more populated. We use the degree of local fivefold symmetry (LFFS) as the structural indicator to predict plastic deformation of local structures and find that the plastic events prefer to be initiated in regions with a lower degree of LFFS and propagate toward regions with a higher degree of LFFS.

  16. Human Structural Plasticity at Record Speed

    PubMed Central

    Johansen-Berg, Heidi; Baptista, Cassandra Sampaio; Thomas, Adam G.

    2012-01-01

    How rapidly does learning shape our brains? A new study using diffusion magnetic resonance imaging in both humans and rats suggests that just two hours of spatial learning is sufficient to change brain structure. PMID:22445333

  17. Structural Plasticity, Effectual Connectivity, and Memory in Cortex

    PubMed Central

    Knoblauch, Andreas; Sommer, Friedrich T.

    2016-01-01

    Learning and memory is commonly attributed to the modification of synaptic strengths in neuronal networks. More recent experiments have also revealed a major role of structural plasticity including elimination and regeneration of synapses, growth and retraction of dendritic spines, and remodeling of axons and dendrites. Here we work out the idea that one likely function of structural plasticity is to increase “effectual connectivity” in order to improve the capacity of sparsely connected networks to store Hebbian cell assemblies that are supposed to represent memories. For this we define effectual connectivity as the fraction of synaptically linked neuron pairs within a cell assembly representing a memory. We show by theory and numerical simulation the close links between effectual connectivity and both information storage capacity of neural networks and effective connectivity as commonly employed in functional brain imaging and connectome analysis. Then, by applying our model to a recently proposed memory model, we can give improved estimates on the number of cell assemblies that can be stored in a cortical macrocolumn assuming realistic connectivity. Finally, we derive a simplified model of structural plasticity to enable large scale simulation of memory phenomena, and apply our model to link ongoing adult structural plasticity to recent behavioral data on the spacing effect of learning. PMID:27378861

  18. Unravelling the structural plasticity of stretched DNA under torsional constraint

    NASA Astrophysics Data System (ADS)

    King, Graeme A.; Peterman, Erwin J. G.; Wuite, Gijs J. L.

    2016-06-01

    Regions of the genome are often held under torsional constraint. Nevertheless, the influence of such constraint on DNA-protein interactions during genome metabolism is still poorly understood. Here using a combined optical tweezers and fluorescence microscope, we quantify and explain how torsional constraint influences the structural stability of DNA under applied tension. We provide direct evidence that concomitant basepair melting and helical unwinding can occur in torsionally constrained DNA at forces >~50 pN. This striking result indicates that local changes in linking number can be absorbed by the rest of the DNA duplex. We also present compelling new evidence that an overwound DNA structure (likely P-DNA) is created (alongside underwound structures) at forces >~110 pN. These findings substantiate previous theoretical predictions and highlight a remarkable structural plasticity of torsionally constrained DNA. Such plasticity may be required in vivo to absorb local changes in linking number in DNA held under torsional constraint.

  19. Chicken fetal liver DNA damage and adduct formation by activation-dependent DNA-reactive carcinogens and related compounds of several structural classes.

    PubMed

    Williams, Gary M; Duan, Jian-Dong; Brunnemann, Klaus D; Iatropoulos, Michael J; Vock, Esther; Deschl, Ulrich

    2014-09-01

    The chicken egg genotoxicity assay (CEGA), which utilizes the liver of an intact and aseptic embryo-fetal test organism, was evaluated using four activation-dependent DNA-reactive carcinogens and four structurally related less potent carcinogens or non-carcinogens. In the assay, three daily doses of test substances were administered to eggs containing 9-11-day-old fetuses and the fetal livers were assessed for two endpoints, DNA breaks using the alkaline single cell gel electrophoresis (comet) assay and DNA adducts using the (32)P-nucleotide postlabeling (NPL) assay. The effects of four carcinogens of different structures requiring distinct pathways of bioactivation, i.e., 2-acetylaminofluorene (AAF), aflatoxin B1 (AFB1), benzo[a]pyrene (B[a]P), and diethylnitrosamine (DEN), were compared with structurally related non-carcinogens fluorene (FLU) and benzo[e]pyrene (B[e]P) or weak carcinogens, aflatoxin B2 (AFB2) and N-nitrosodiethanolamine (NDELA). The four carcinogens all produced DNA breaks at microgram or low milligram total doses, whereas less potent carcinogens and non-carcinogens yielded borderline or negative results, respectively, at higher doses. AAF and B[a]P produced DNA adducts, whereas none was found with the related comparators FLU or B[e]P, consistent with comet results. DEN and NDELA were also negative for adducts, as expected in the case of DEN for an alkylating agent in the standard NPL assay. Also, AFB1 and AFB2 were negative in NPL, as expected, due to the nature of ring opened aflatoxin adducts, which are resistant to enzymatic digestion. Thus, the CEGA, using comet and NPL, is capable of detection of the genotoxicity of diverse DNA-reactive carcinogens, while not yielding false positives for non-carcinogens.

  20. ECM receptors in neuronal structure, synaptic plasticity, and behavior.

    PubMed

    Kerrisk, Meghan E; Cingolani, Lorenzo A; Koleske, Anthony J

    2014-01-01

    During central nervous system development, extracellular matrix (ECM) receptors and their ligands play key roles as guidance molecules, informing neurons where and when to send axonal and dendritic projections, establish connections, and form synapses between pre- and postsynaptic cells. Once stable synapses are formed, many ECM receptors transition in function to control the maintenance of stable connections between neurons and regulate synaptic plasticity. These receptors bind to and are activated by ECM ligands. In turn, ECM receptor activation modulates downstream signaling cascades that control cytoskeletal dynamics and synaptic activity to regulate neuronal structure and function and thereby impact animal behavior. The activities of cell adhesion receptors that mediate interactions between pre- and postsynaptic partners are also strongly influenced by ECM composition. This chapter highlights a number of ECM receptors, their roles in the control of synapse structure and function, and the impact of these receptors on synaptic plasticity and animal behavior.

  1. ECM receptors in neuronal structure, synaptic plasticity, and behavior

    PubMed Central

    Kerrisk, Meghan E.; Cingolani, Lorenzo A.; Koleske, Anthony J.

    2015-01-01

    During central nervous system development, extracellular matrix (ECM) receptors and their ligands play key roles as guidance molecules, informing neurons where and when to send axonal and dendritic projections, establish connections, and form synapses between pre- and postsynaptic cells. Once stable synapses are formed, many ECM receptors transition in function to control the maintenance of stable connections between neurons and regulate synaptic plasticity. These receptors bind to and are activated by ECM ligands. In turn, ECM receptor activation modulates downstream signaling cascades that control cytoskeletal dynamics and synaptic activity to regulate neuronal structure and function and thereby impact animal behavior. The activities of cell adhesion receptors that mediate interactions between pre- and post-synaptic partners are also strongly influenced by ECM composition. This chapter highlights a number of ECM receptors, their roles in the control of synapse structure and function, and the impact of these receptors on synaptic plasticity and animal behavior. PMID:25410355

  2. Plastic optical fibre sensor for damage detection in offshore structures

    NASA Astrophysics Data System (ADS)

    Kuang, K. S. C.; Koh, C. G.

    2009-12-01

    It is important to ensure the safe and reliable use of massive engineering structures such as offshore platforms, including all aspects of safety and design code compliance. Although routine inspection is an integral part of the safety protocol in operating and maintaining these structures, regular assessment of the effectiveness and efficiency of existing safety evaluation methods is clearly desired in view of emerging technologies for structural health monitoring of engineering structures. The recent advancement in plastic optical fibre (POF) materials and processing render POF sensors an attractive alternative to glass-based optical fibre sensors as they offer much greater being flexibility, high resistance to fracture and hence the ease in their handling and installation. In this paper, some preliminary results demonstrating the use of plastic optical fibre sensors for damage detection and structural health monitoring for offshore and marine-related applications will be summarized. In this study, POF will be used for crack detection in tubular steel specimens in conjunction with a high-resolution photon-counting optical time-domain reflectrometry (v-OTDR). Although the use of OTDR technique is an established method in the telecommunication industry, this study is new in that it is now possible, with the availability of v-OTDR and graded-index perfluorinated POF, to detect and locate the crack position in the host structure to within 10 cm accuracy or better. It will also be shown that this technique could readily be configured to monitor crack growth in steel tubular members.

  3. Plastic optical fibre sensor for damage detection in offshore structures

    NASA Astrophysics Data System (ADS)

    Kuang, K. S. C.; Koh, C. G.

    2010-03-01

    It is important to ensure the safe and reliable use of massive engineering structures such as offshore platforms, including all aspects of safety and design code compliance. Although routine inspection is an integral part of the safety protocol in operating and maintaining these structures, regular assessment of the effectiveness and efficiency of existing safety evaluation methods is clearly desired in view of emerging technologies for structural health monitoring of engineering structures. The recent advancement in plastic optical fibre (POF) materials and processing render POF sensors an attractive alternative to glass-based optical fibre sensors as they offer much greater being flexibility, high resistance to fracture and hence the ease in their handling and installation. In this paper, some preliminary results demonstrating the use of plastic optical fibre sensors for damage detection and structural health monitoring for offshore and marine-related applications will be summarized. In this study, POF will be used for crack detection in tubular steel specimens in conjunction with a high-resolution photon-counting optical time-domain reflectrometry (v-OTDR). Although the use of OTDR technique is an established method in the telecommunication industry, this study is new in that it is now possible, with the availability of v-OTDR and graded-index perfluorinated POF, to detect and locate the crack position in the host structure to within 10 cm accuracy or better. It will also be shown that this technique could readily be configured to monitor crack growth in steel tubular members.

  4. A simplified method for elastic-plastic-creep structural analysis

    NASA Technical Reports Server (NTRS)

    Kaufman, A.

    1984-01-01

    A simplified inelastic analysis computer program (ANSYPM) was developed for predicting the stress-strain history at the critical location of a thermomechanically cycled structure from an elastic solution. The program uses an iterative and incremental procedure to estimate the plastic strains from the material stress-strain properties and a plasticity hardening model. Creep effects are calculated on the basis of stress relaxation at constant strain, creep at constant stress or a combination of stress relaxation and creep accumulation. The simplified method was exercised on a number of problems involving uniaxial and multiaxial loading, isothermal and nonisothermal conditions, dwell times at various points in the cycles, different materials and kinematic hardening. Good agreement was found between these analytical results and nonlinear finite element solutions for these problems. The simplified analysis program used less than 1 percent of the CPU time required for a nonlinear finite element analysis.

  5. A simplified method for elastic-plastic-creep structural analysis

    NASA Technical Reports Server (NTRS)

    Kaufman, A.

    1985-01-01

    A simplified inelastic analysis computer program (ANSYPM) was developed for predicting the stress-strain history at the critical location of a thermomechanically cycled structure from an elastic solution. The program uses an iterative and incremental procedure to estimate the plastic strains from the material stress-strain properties and a plasticity hardening model. Creep effects are calculated on the basis of stress relaxation at constant strain, creep at constant stress or a combination of stress relaxation and creep accumulation. The simplified method was exercised on a number of problems involving uniaxial and multiaxial loading, isothermal and nonisothermal conditions, dwell times at various points in the cycles, different materials and kinematic hardening. Good agreement was found between these analytical results and nonlinear finite element solutions for these problems. The simplified analysis program used less than 1 percent of the CPU time required for a nonlinear finite element analysis.

  6. Technology and future prospects for lightweight plastic vehicle structures

    SciTech Connect

    Stodolsky, F.; Cuenca, R.M.; Bonsignore, P.V.

    1997-08-01

    The state of the technology and the materials and processing issues of using plastics in vehicle body applications (structural and semistructural) were assessed. Plastics are significantly lighter in weight, more easily fabricated into complex shapes, and more corrosion resistance than sheet steel, high-strength steel, or aluminum. However, at their current stage of development, plastics are deficient in one or more necessary properties: heat resistance and dimensional stability, stiffness and tensile strength, toughness, and impact resistance. To upgrade their physical properties for automotive chassis/body applications, plastics need to be compounds with suitable reinforcing fibers. As a short-term approach, the material of choice is a composite structure made with low-cost glass-fiber reinforcement, such as that made in the resin-transfer-molding (RTM) process and used in the body of the Dodge Viper. However, RTM technology based on thermosets requires a processing cycle time that is too long for large production runs. Adaptation of RTM to the formation of thermoplastic composite bodies could have a significant advantage over thermoset technology. Cyclic oligomers, which are precursors to thermoplastic matrix polymers, show promise for this application. Farther on the horizon are advanced composites compounds with the much more expensive (but stronger and stiffer) carbon-fiber reinforcement. However, significant price reductions of precursor materials and advances in processing and fabrication would be needed. Other materials holding promise are liquid crystal polymers (LCP) and LCP blends with other polymers (molecular composites). However, the cost of monomers and the subsequent polymerization technology also remains a considerable drawback to the widespread and increasing acceptance of LCPs.

  7. Structural Transformations in Metallic Materials During Plastic Deformation

    NASA Astrophysics Data System (ADS)

    Zasimchuk, E.; Turchak, T.; Baskova, A.; Chausov, N.; Hutsaylyuk, V.

    2017-03-01

    In this paper, the structure formation during the plastic deformation of polycrystalline nickel and aluminum based alloy 2024-T3 is investigated. The possibility of the relaxation and synergetic structure formation is examined. It is shown the deformation softening to be due to the crystallization of the amorphous structure of hydrodynamics flow channels (synergetic structure) HC as micrograins and their subsequent growth. The possible mechanism of micrograins' growth is proposed. The deformation processes change the phase composition of the multiphase alloy 2024-T3. It is shown by the quantitative analysis of the structures which were deformed in different regimes of the alloy samples. A method for increasing of the fatigue life through a dynamic pre-deformation is suggested.

  8. Structural Transformations in Metallic Materials During Plastic Deformation

    NASA Astrophysics Data System (ADS)

    Zasimchuk, E.; Turchak, T.; Baskova, A.; Chausov, N.; Hutsaylyuk, V.

    2017-02-01

    In this paper, the structure formation during the plastic deformation of polycrystalline nickel and aluminum based alloy 2024-T3 is investigated. The possibility of the relaxation and synergetic structure formation is examined. It is shown the deformation softening to be due to the crystallization of the amorphous structure of hydrodynamics flow channels (synergetic structure) HC as micrograins and their subsequent growth. The possible mechanism of micrograins' growth is proposed. The deformation processes change the phase composition of the multiphase alloy 2024-T3. It is shown by the quantitative analysis of the structures which were deformed in different regimes of the alloy samples. A method for increasing of the fatigue life through a dynamic pre-deformation is suggested.

  9. Plasticity of the RNA Kink Turn Structural Motif

    SciTech Connect

    Antonioli, A.; Cochrane, J; Lipchock, S; Strobel, S

    2010-01-01

    The kink turn (K-turn) is an RNA structural motif found in many biologically significant RNAs. While most examples of the K-turn have a similar fold, the crystal structure of the Azoarcus group I intron revealed a novel RNA conformation, a reverse kink turn bent in the direction opposite that of a consensus K-turn. The reverse K-turn is bent toward the major grooves rather than the minor grooves of the flanking helices, yet the sequence differs from the K-turn consensus by only a single nucleotide. Here we demonstrate that the reverse bend direction is not solely defined by internal sequence elements, but is instead affected by structural elements external to the K-turn. It bends toward the major groove under the direction of a tetraloop-tetraloop receptor. The ability of one sequence to form two distinct structures demonstrates the inherent plasticity of the K-turn sequence. Such plasticity suggests that the K-turn is not a primary element in RNA folding, but instead is shaped by other structural elements within the RNA or ribonucleoprotein assembly.

  10. Unravelling the structural plasticity of stretched DNA under torsional constraint

    PubMed Central

    King, Graeme A.; Peterman, Erwin J. G.; Wuite, Gijs J. L.

    2016-01-01

    Regions of the genome are often held under torsional constraint. Nevertheless, the influence of such constraint on DNA–protein interactions during genome metabolism is still poorly understood. Here using a combined optical tweezers and fluorescence microscope, we quantify and explain how torsional constraint influences the structural stability of DNA under applied tension. We provide direct evidence that concomitant basepair melting and helical unwinding can occur in torsionally constrained DNA at forces >∼50 pN. This striking result indicates that local changes in linking number can be absorbed by the rest of the DNA duplex. We also present compelling new evidence that an overwound DNA structure (likely P-DNA) is created (alongside underwound structures) at forces >∼110 pN. These findings substantiate previous theoretical predictions and highlight a remarkable structural plasticity of torsionally constrained DNA. Such plasticity may be required in vivo to absorb local changes in linking number in DNA held under torsional constraint. PMID:27263853

  11. Structural brain plasticity in Parkinson's disease induced by balance training.

    PubMed

    Sehm, Bernhard; Taubert, Marco; Conde, Virginia; Weise, David; Classen, Joseph; Dukart, Juergen; Draganski, Bogdan; Villringer, Arno; Ragert, Patrick

    2014-01-01

    We investigated morphometric brain changes in patients with Parkinson's disease (PD) that are associated with balance training. A total of 20 patients and 16 healthy matched controls learned a balance task over a period of 6 weeks. Balance testing and structural magnetic resonance imaging were performed before and after 2, 4, and 6 training weeks. Balance performance was re-evaluated after ∼20 months. Balance training resulted in performance improvements in both groups. Voxel-based morphometry revealed learning-dependent gray matter changes in the left hippocampus in healthy controls. In PD patients, performance improvements were correlated with gray matter changes in the right anterior precuneus, left inferior parietal cortex, left ventral premotor cortex, bilateral anterior cingulate cortex, and left middle temporal gyrus. Furthermore, a TIME × GROUP interaction analysis revealed time-dependent gray matter changes in the right cerebellum. Our results highlight training-induced balance improvements in PD patients that may be associated with specific patterns of structural brain plasticity. In summary, we provide novel evidence for the capacity of the human brain to undergo learning-related structural plasticity even in a pathophysiological disease state such as in PD.

  12. Thermal and Structural Properties of Silk Biomaterials Plasticized by Glycerol.

    PubMed

    Brown, Joseph E; Davidowski, Stephen K; Xu, Dian; Cebe, Peggy; Onofrei, David; Holland, Gregory P; Kaplan, David L

    2016-12-12

    The molecular interactions of silk materials plasticized using glycerol were studied, as these materials provide options for biodegradable and flexible protein-based systems. Plasticizer interactions with silk were analyzed by thermal, spectroscopic, and solid-state NMR analyses. Spectroscopic analysis implied that glycerol was hydrogen bonded to the peptide matrix, but may be displaced with polar solvents. Solid-state NMR indicated that glycerol induced β-sheet formation in the dried silk materials, but not to the extent of methanol treatment. Fast scanning calorimetry suggested that β-sheet crystal formation in silk-glycerol films appeared to be less organized than in the methanol treated silk films. We propose that glycerol may be simultaneously inducing and interfering with β-sheet formation in silk materials, causing some improper folding that results in less-organized silk II structures even after the glycerol is removed. This difference, along with trace residual glycerol, allows glycerol extracted silk materials to retain more flexibility than methanol processed versions.

  13. Activity dependent CAM cleavage and neurotransmission

    PubMed Central

    Conant, Katherine; Allen, Megan; Lim, Seung T.

    2015-01-01

    Spatially localized proteolysis represents an elegant means by which neuronal activity dependent changes in synaptic structure, and thus experience dependent learning and memory, can be achieved. In vitro and in vivo studies suggest that matrix metalloproteinase and adamalysin activity is concentrated at the cell surface, and emerging evidence suggests that increased peri-synaptic expression, release and/or activation of these proteinases occurs with enhanced excitatory neurotransmission. Synaptically expressed cell adhesion molecules (CAMs) could therefore represent important targets for neuronal activity-dependent proteolysis. Several CAM subtypes are expressed at the synapse, and their cleavage can influence the efficacy of synaptic transmission through a variety of non-mutually exclusive mechanisms. In the following review, we discuss mechanisms that regulate neuronal activity-dependent synaptic CAM shedding, including those that may be calcium dependent. We also highlight CAM targets of activity-dependent proteolysis including neuroligin and intercellular adhesion molecule-5 (ICAM-5). We include discussion focused on potential consequences of synaptic CAM shedding, with an emphasis on interactions between soluble CAM cleavage products and specific pre- and post-synaptic receptors. PMID:26321910

  14. Structural plasticity and catalysis regulation of a thermosensor histidine kinase

    PubMed Central

    Albanesi, Daniela; Martín, Mariana; Trajtenberg, Felipe; Mansilla, María C.; Haouz, Ahmed; Alzari, Pedro M.; de Mendoza, Diego; Buschiazzo, Alejandro

    2009-01-01

    Temperature sensing is essential for the survival of living cells. A major challenge is to understand how a biological thermometer processes thermal information to optimize cellular functions. Using structural and biochemical approaches, we show that the thermosensitive histidine kinase, DesK, from Bacillus subtilis is cold-activated through specific interhelical rearrangements in its central four-helix bundle domain. As revealed by the crystal structures of DesK in different functional states, the plasticity of this helical domain influences the catalytic activities of the protein, either by modifying the mobility of the ATP-binding domains for autokinase activity or by modulating binding of the cognate response regulator to sustain the phosphotransferase and phosphatase activities. The structural and biochemical data suggest a model in which the transmembrane sensor domain of DesK promotes these structural changes through conformational signals transmitted by the membrane-connecting two-helical coiled-coil, ultimately controlling the alternation between output autokinase and phosphatase activities. The structural comparison of the different DesK variants indicates that incoming signals can take the form of helix rotations and asymmetric helical bends similar to those reported for other sensing systems, suggesting that a similar switching mechanism could be operational in a wide range of sensor histidine kinases. PMID:19805278

  15. Implementation of elastic-plastic structural analysis into NASTRAN

    NASA Technical Reports Server (NTRS)

    Levy, A.; Pifko, A. B.; Ogilvie, P. L.

    1983-01-01

    Elastic-plastic analytic capabilities were incorporated into the NASTRAN program. The present implementation includes a general rigid format and additional bulk data cards as well as to two new modules. The modules are specialized to include only perfect plasticity of the CTRMEN and CROD elements but can easily be expanded to include other plasticity theories and elements. The practical problem of an elastic-plastic analysis of a ship's bracket connection is demonstrated and compared to an equivalent analysis using Grumman's PLANS program. The present work demonstrates the feasibility of incorporating general elastic-plastic capabilities into NASTRAN.

  16. MicroRNA precursors are not structurally robust but plastic.

    PubMed

    Rodrigo, Guillermo; Elena, Santiago F

    2013-01-01

    Robustness is considered a ubiquitous property of living systems at all levels of organization, and small noncoding RNA (sncRNA) is a genuine model for its study at the molecular level. In this communication, we question whether microRNA precursors (pre-miRNAs) are actually structurally robust, as previously suggested. We found that natural pre-miRNAs are not more robust than expected under an appropriate null model. On the contrary, we found that eukaryotic pre-miRNAs show a significant enrichment in conformational flexibility at the thermal equilibrium of the molecule, that is, in their plasticity. Our results further support the selection for functional diversification and evolvability in sncRNAs.

  17. Development of recycled plastic composites for structural applications from CEA plastics

    NASA Astrophysics Data System (ADS)

    Bhalla, Agrim

    Plastic waste from consumer electronic appliances (CEAs) such as computer and printer parts including Polystyrene (PS), Acrylonitrile Butadiene Styrene (ABS), Polystyrene (PS) and PC/ABS were collected using handheld FTIR Spectrophotometer. The blends of these plastics with High Density Polyethylene (HDPE) are manufactured under special processing conditions in a single screw compounding injection molding machine. The blends are thermoplastics have high stiffness and strength, which may enhance the mechanical properties of HDPE like tensile modulus, ultimate tensile strength, tensile break and tensile yield. These composites have a potential to be used for the future application of recycled plastic lumber, thus replacing the traditional wood lumber.

  18. The genetics of phenotypic plasticity in nematode feeding structures

    PubMed Central

    Dardiry, Mohannad; Lenuzzi, Masa; Namdeo, Suryesh; Renahan, Tess; Sieriebriennikov, Bogdan; Werner, Michael S.

    2017-01-01

    Phenotypic plasticity has been proposed as an ecological and evolutionary concept. Ecologically, it can help study how genes and the environment interact to produce robust phenotypes. Evolutionarily, as a facilitator it might contribute to phenotypic novelty and diversification. However, the discussion of phenotypic plasticity remains contentious in parts due to the absence of model systems and rigorous genetic studies. Here, we summarize recent work on the nematode Pristionchus pacificus, which exhibits a feeding plasticity allowing predatory or bacteriovorous feeding. We show feeding plasticity to be controlled by developmental switch genes that are themselves under epigenetic control. Phylogenetic and comparative studies support phenotypic plasticity and its role as a facilitator of morphological novelty and diversity. PMID:28298309

  19. Injection of WGA-Alexa 488 into the ipsilateral hemidiaphragm of acutely and chronically C2 hemisected rats reveals activity-dependent synaptic plasticity in the respiratory motor pathways.

    PubMed

    Buttry, Janelle L; Goshgarian, Harry G

    2014-11-01

    WGA-Alexa 488 is a fluorescent neuronal tracer that demonstrates transsynaptic transport in the central nervous system. The transsynaptic transport occurs over physiologically active synaptic connections rather than less active or silent connections. Immediately following C2 spinal cord hemisection (C2Hx), when WGA-Alexa 488 is injected into the ipsilateral hemidiaphragm, the tracer diffuses across the midline of the diaphragm and retrogradely labels the phrenic nuclei (PN) bilaterally in the spinal cord. Subsequently, the tracer is transsynaptically transported bilaterally to the rostral Ventral Respiratory Groups (rVRGs) in the medulla over physiologically active connections. No other neurons are labeled in the acute C2Hx model at the level of the phrenic nuclei or in the medulla. However, with a recovery period of at least 7weeks (chronic C2Hx), the pattern of WGA-Alexa 488 labeling is notably changed. In addition to the bilateral PN and rVRG labeling, the chronic C2Hx model reveals fluorescence in the ipsilateral ventral and dorsal spinocerebellar tracts, and the ipsilateral reticulospinal tract. Furthermore, interneurons are labeled bilaterally in laminae VII and VIII of the spinal cord as well as neurons in the motor nuclei bilaterally of the intercostal and forelimb muscles. Moreover, in the chronic C2Hx model, there is bilateral labeling of additional medullary centers including raphe, hypoglossal, spinal trigeminal, parvicellular reticular, gigantocellular reticular, and intermediate reticular nuclei. The selective WGA-Alexa 488 labeling of additional locations in the chronic C2Hx model is presumably due to a hyperactive state of the synaptic pathways and nuclei previously shown to connect with the respiratory centers in a non-injured model. The present study suggests that hyperactivity not only occurs in neuronal centers and pathways caudal to spinal cord injury, but in supraspinal centers as well. The significance of such injury-induced plasticity is

  20. Activity-dependent Protein Dynamics Define Interconnected Cores of Co-regulated Postsynaptic Proteins*

    PubMed Central

    Trinidad, Jonathan C.; Thalhammer, Agnes; Burlingame, Alma L.; Schoepfer, Ralf

    2013-01-01

    Synapses are highly dynamic structures that mediate cell–cell communication in the central nervous system. Their molecular composition is altered in an activity-dependent fashion, which modulates the efficacy of subsequent synaptic transmission events. Whereas activity-dependent trafficking of individual key synaptic proteins into and out of the synapse has been characterized previously, global activity-dependent changes in the synaptic proteome have not been studied. To test the feasibility of carrying out an unbiased large-scale approach, we investigated alterations in the molecular composition of synaptic spines following mass stimulation of the central nervous system induced by pilocarpine. We observed widespread changes in relative synaptic abundances encompassing essentially all proteins, supporting the view that the molecular composition of the postsynaptic density is tightly regulated. In most cases, we observed that members of gene families displayed coordinate regulation even when they were not known to physically interact. Analysis of correlated synaptic localization revealed a tightly co-regulated cluster of proteins, consisting of mainly glutamate receptors and their adaptors. This cluster constitutes a functional core of the postsynaptic machinery, and changes in its size affect synaptic strength and synaptic size. Our data show that the unbiased investigation of activity-dependent signaling of the postsynaptic density proteome can offer valuable new information on synaptic plasticity. PMID:23035237

  1. Paradoxical signaling regulates structural plasticity in dendritic spines

    PubMed Central

    Rangamani, Padmini; Levy, Michael G.; Khan, Shahid; Oster, George

    2016-01-01

    Transient spine enlargement (3- to 5-min timescale) is an important event associated with the structural plasticity of dendritic spines. Many of the molecular mechanisms associated with transient spine enlargement have been identified experimentally. Here, we use a systems biology approach to construct a mathematical model of biochemical signaling and actin-mediated transient spine expansion in response to calcium influx caused by NMDA receptor activation. We have identified that a key feature of this signaling network is the paradoxical signaling loop. Paradoxical components act bifunctionally in signaling networks, and their role is to control both the activation and the inhibition of a desired response function (protein activity or spine volume). Using ordinary differential equation (ODE)-based modeling, we show that the dynamics of different regulators of transient spine expansion, including calmodulin-dependent protein kinase II (CaMKII), RhoA, and Cdc42, and the spine volume can be described using paradoxical signaling loops. Our model is able to capture the experimentally observed dynamics of transient spine volume. Furthermore, we show that actin remodeling events provide a robustness to spine volume dynamics. We also generate experimentally testable predictions about the role of different components and parameters of the network on spine dynamics. PMID:27551076

  2. Multiscale Modeling of Structurally-Graded Materials Using Discrete Dislocation Plasticity Models and Continuum Crystal Plasticity Models

    NASA Technical Reports Server (NTRS)

    Saether, Erik; Hochhalter, Jacob D.; Glaessgen, Edward H.

    2012-01-01

    A multiscale modeling methodology that combines the predictive capability of discrete dislocation plasticity and the computational efficiency of continuum crystal plasticity is developed. Single crystal configurations of different grain sizes modeled with periodic boundary conditions are analyzed using discrete dislocation plasticity (DD) to obtain grain size-dependent stress-strain predictions. These relationships are mapped into crystal plasticity parameters to develop a multiscale DD/CP model for continuum level simulations. A polycrystal model of a structurally-graded microstructure is developed, analyzed and used as a benchmark for comparison between the multiscale DD/CP model and the DD predictions. The multiscale DD/CP model follows the DD predictions closely up to an initial peak stress and then follows a strain hardening path that is parallel but somewhat offset from the DD predictions. The difference is believed to be from a combination of the strain rate in the DD simulation and the inability of the DD/CP model to represent non-monotonic material response.

  3. Thin-walled compliant plastic structures for meso-scale fluidic systems

    SciTech Connect

    Miles, R R; Schumann, D L

    1998-12-29

    Thin-walled, compliant plastic structures for meso-scale fluidic systems were fabricated, tested and used to demonstrate valving, pumping, metering and mixing. These structures permit the isolation of actuators and sensors from the working fluid, thereby reducing chemical compatibility issues. The thin-walled, compliant plastic structures can be used in either a permanent, reusable system or as an inexpensive disposable for single-use assay systems. The implementation of valving, pumping, mixing and metering operations involve only an elastic change in the mechanical shape of various portions of the structure. Advantages provided by the thin-walled plastic structures include reduced dead volume and rapid mixing. Five different methods for fabricating the thin-walled plastic structures discussed including laser welding, molding, vacuum forming, thermal heat staking and photolithographic patterning techniques.

  4. Activity-dependent dendritic release of BDNF and biological consequences

    PubMed Central

    Kuczewski, Nicola; Porcher, Christophe; Lessmann, Volkmar; Medina, Igor; Gaiarsa, Jean-Luc

    2009-01-01

    Network construction and reorganization is modulated by the level and pattern of synaptic activity generated in the nervous system. During the past decades, neurotrophins, and in particular brain-derived neurotrophic factor (BDNF), have emerged as attractive candidates for linking synaptic activity and brain plasticity. Thus, neurotrophin expression and secretion are under the control of activity-dependent mechanisms and, besides their classical role in supporting neuronal survival neurotrophins, modulate nearly all key steps of network construction from neuronal migration to experience-dependent refinement of local connections. In this paper, we provide an overview of recent findings showing that BDNF can serve as a target-derived messenger for activity-dependent synaptic plasticity and development at the single cell level. PMID:19156544

  5. Reversible, activity-dependent targeting of profilin to neuronal nuclei

    SciTech Connect

    Birbach, Andreas . E-mail: andreas.birbach@lbicr.lbg.ac.at; Verkuyl, J. Martin; Matus, Andrew . E-mail: aim@fmi.ch

    2006-07-15

    The actin cytoskeleton in pyramidal neurons plays a major role in activity-dependent processes underlying neuronal plasticity. The small actin-binding protein profilin shows NMDA receptor-dependent accumulation in dendritic spines, which is correlated with suppression of actin dynamics and long-term stabilization of synaptic morphology. Here we show that following NMDA receptor activation profilin also accumulates in the nucleus of hippocampal neurons via a process involving rearrangement of the actin cytoskeleton. This simultaneous targeting to dendritic spines and the cell nucleus suggests a novel mechanism of neuronal plasticity in which profilin both tags activated synapses and influences nuclear events.

  6. 76 FR 13227 - Continental Structural Plastics, Including On-Site Leased Workers From Kelly Services and Doepker...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-03-10

    ... Employment and Training Administration Continental Structural Plastics, Including On-Site Leased Workers From... 31, 2008, applicable to workers of Continental Structural Plastics, North Baltimore, Ohio. The... Continental Structural Plastics, including on- site leased workers from Kelly Services and Doepker Group,...

  7. Structural analysis of the alcohol acyltransferase protein family from Cucumis melo shows that enzyme activity depends on an essential solvent channel.

    PubMed

    Galaz, Sebastián; Morales-Quintana, Luis; Moya-León, María Alejandra; Herrera, Raúl

    2013-03-01

    Alcohol acyltransferases (AAT) play a key role in ester biosynthesis. In Cucumis melo var. cantalupensis, AATs are encoded by a gene family of four members (CmAAT1-4). CmAAT1, CmAAT3 and CmAAT4 are capable of synthesizing esters, with CmAAT1 the most active. CmAAT2 is inactive and has an Ala268 residue instead of a threonine which is present in all other active AATs, although the role of this residue is still unclear. The present work aims to understand the molecular mechanism involved in ester biosynthesis in melon fruit and to clarify the importance of the Ala268 residue. First, structural models for each protein were built by comparative modelling methodology. Afterwards, conformational interaction between the protein and several ligands, alcohols and acyl-CoAs was explored by molecular docking and molecular dynamics simulation. Structural analysis showed that CmAATs share a similar structure. Also, well-defined solvent channels were described in the CmAATs except for CmAAT2 which does not have a proper channel and instead has a small pocket around Ala268. Residues of the catalytic HxxxD motif interact with substrates within the solvent channel, with Ser363 also important. Strong binding interaction energies were described for the best substrate couple of each CmAAT (hexyl-, benzyl- and cinnamyl-acetate for CmAAT1, 3 and 4 respectively). CmAAT1 and CmAAT2 protein surfaces share similar electrostatic potentials; nevertheless the entrance channels for the substrates differ in location and electrostatic character, suggesting that Ala268 might be responsible for that. This could partly explain the major differences in activity reported for these two enzymes.

  8. Reliability of elasto-plastic structure using finite element method

    NASA Astrophysics Data System (ADS)

    Ning, Liu; Wilson H, Tang; Jiashou, Zhuo

    2002-02-01

    A solution of probabilistic FEM for elastic-plastic materials is presented based on the incremental theory of plasticity and a modified initial stress method. The formulations are deduced through a direct differentiation scheme. Partial differentiation of displacement, stress and the performance function can be iteratively performed with the computation of the mean values of displacement and stress. The presented method enjoys the efficiency of both the perturbation method and the finite difference method, but avoids the approximation during the partial differentiation calculation. In order to improve the efficiency, the adjoint vector method is introduced to calculate the differentiation of stress and displacement with respect to random variables. In addition, a time-saving computational method for reliability index of elastic-plastic materials is suggested based upon the advanced First Order Second Moment (FOSM) and by the usage of Taylor expansion for displacement. The suggested method is also applicable to 3-D cases.

  9. Structure of the Ni(II) complex of Escherichia coli peptide deformylase and suggestions on deformylase activities depending on different metal(II) centres.

    PubMed

    Yen, Ngo Thi Hai; Bogdanović, Xenia; Palm, Gottfried J; Kühl, Olaf; Hinrichs, Winfried

    2010-02-01

    Crystal structures of polypeptide deformylase (PDF) of Escherichia coli with nickel(II) replacing the native iron(II) have been solved with chloride and formate as metal ligands. The chloro complex is a model for the correct protonation state of the hydrolytic hydroxo ligand and the protonated status of the Glu133 side chain as part of the hydrolytic mechanism. The ambiguity that recently some PDFs have been identified with Zn(2+) ion as the active-site centre whereas others are only active with Fe(2+) (or Co(2+), Ni(2+) is discussed with respect to Lewis acid criteria of the metal ion and substrate activation by the CD loop.

  10. Structural Signature of Plasticity Unveiled by Nano-Scale Viscoelastic Contact in a Metallic Glass

    PubMed Central

    Lu, Y. M.; Zeng, J. F.; Wang, S.; Sun, B. A.; Wang, Q.; Lu, J.; Gravier, S.; Bladin, J. J.; Wang, W. H.; Pan, M. X.; Liu, C. T.; Yang, Y.

    2016-01-01

    Room-temperature plasticity in metallic glasses (MGs) is commonly associated with local structural heterogeneity; however, direct observation of the subtle structural change caused by plasticity is vitally important but the data are extremely scarce. Based on dynamic atomic force microscopy (DAFM), here we show that plasticity-induced structural evolution in a Zr-Ni MG can be revealed via nano-scale viscoelastic contacts between an AFM tip and plastically deformed MG surface layers. Our experimental results clearly show a spatial amplification of the nano-scale structural heterogeneity caused by the distributed plastic flow, which can be linked to the limited growth, reorientation and agglomeration of some nano-scale energy-absorbing regions, which are reminiscent of the behavior of the defect-like regions with non-affine deformation as conceived in many theories and models. Furthermore, we are able to experimentally extract the thermodynamic properties of these nano-scale regions, which possess an energy barrier of 0.3–0.5 eV, about half of that for a typical shear transformation event that usually occurs at the onset of plasticity. The outcome of our current work sheds quantitative insights into the correlation between plasticity and structural heterogeneity in MGs. PMID:27383387

  11. Structural Signature of Plasticity Unveiled by Nano-Scale Viscoelastic Contact in a Metallic Glass

    NASA Astrophysics Data System (ADS)

    Lu, Y. M.; Zeng, J. F.; Wang, S.; Sun, B. A.; Wang, Q.; Lu, J.; Gravier, S.; Bladin, J. J.; Wang, W. H.; Pan, M. X.; Liu, C. T.; Yang, Y.

    2016-07-01

    Room-temperature plasticity in metallic glasses (MGs) is commonly associated with local structural heterogeneity; however, direct observation of the subtle structural change caused by plasticity is vitally important but the data are extremely scarce. Based on dynamic atomic force microscopy (DAFM), here we show that plasticity-induced structural evolution in a Zr-Ni MG can be revealed via nano-scale viscoelastic contacts between an AFM tip and plastically deformed MG surface layers. Our experimental results clearly show a spatial amplification of the nano-scale structural heterogeneity caused by the distributed plastic flow, which can be linked to the limited growth, reorientation and agglomeration of some nano-scale energy-absorbing regions, which are reminiscent of the behavior of the defect-like regions with non-affine deformation as conceived in many theories and models. Furthermore, we are able to experimentally extract the thermodynamic properties of these nano-scale regions, which possess an energy barrier of 0.3–0.5 eV, about half of that for a typical shear transformation event that usually occurs at the onset of plasticity. The outcome of our current work sheds quantitative insights into the correlation between plasticity and structural heterogeneity in MGs.

  12. Extracellular proteolysis in structural and functional plasticity of mossy fiber synapses in hippocampus

    PubMed Central

    Wiera, Grzegorz; Mozrzymas, Jerzy W.

    2015-01-01

    Brain is continuously altered in response to experience and environmental changes. One of the underlying mechanisms is synaptic plasticity, which is manifested by modification of synapse structure and function. It is becoming clear that regulated extracellular proteolysis plays a pivotal role in the structural and functional remodeling of synapses during brain development, learning and memory formation. Clearly, plasticity mechanisms may substantially differ between projections. Mossy fiber synapses onto CA3 pyramidal cells display several unique functional features, including pronounced short-term facilitation, a presynaptically expressed long-term potentiation (LTP) that is independent of NMDAR activation, and NMDA-dependent metaplasticity. Moreover, structural plasticity at mossy fiber synapses ranges from the reorganization of projection topology after hippocampus-dependent learning, through intrinsically different dynamic properties of synaptic boutons to pre- and postsynaptic structural changes accompanying LTP induction. Although concomitant functional and structural plasticity in this pathway strongly suggests a role of extracellular proteolysis, its impact only starts to be investigated in this projection. In the present report, we review the role of extracellular proteolysis in various aspects of synaptic plasticity in hippocampal mossy fiber synapses. A growing body of evidence demonstrates that among perisynaptic proteases, tissue plasminogen activator (tPA)/plasmin system, β-site amyloid precursor protein-cleaving enzyme 1 (BACE1) and metalloproteinases play a crucial role in shaping plastic changes in this projection. We discuss recent advances and emerging hypotheses on the roles of proteases in mechanisms underlying mossy fiber target specific synaptic plasticity and memory formation. PMID:26582976

  13. Synapse Maturation by Activity-Dependent Ectodomain Shedding of SIRPα

    PubMed Central

    Toth, Anna B.; Terauchi, Akiko; Zhang, Lily Y.; Johnson-Venkatesh, Erin M.; Larsen, David J.; Sutton, Michael A.; Umemori, Hisashi

    2013-01-01

    Formation of appropriate synaptic connections is critical for proper functioning of the brain. After initial synaptic differentiation, active synapses are stabilized by neural activity-dependent signals to establish functional synaptic connections. However, the molecular mechanisms underlying activity-dependent synapse maturation remain to be elucidated. Here we show that activity-dependent ectodomain shedding of SIRPα mediates presynaptic maturation. Two target-derived molecules, FGF22 and SIRPα, sequentially organize the glutamatergic presynaptic terminals during the initial synaptic differentiation and synapse maturation stages, respectively, in the mouse hippocampus. SIRPα drives presynaptic maturation in an activity-dependent fashion. Remarkably, neural activity cleaves the extracellular domain of SIRPα, and the shed ectodomain, in turn, promotes the maturation of the presynaptic terminal. This process involves CaM kinase, matrix metalloproteinases, and the presynaptic receptor CD47. Finally, SIRPα-dependent synapse maturation has significant impacts on synaptic function and plasticity. Thus, ectodomain shedding of SIRPα is an activity-dependent trans-synaptic mechanism for the maturation of functional synapses. PMID:24036914

  14. Structural-chemical modeling of transition of coals to the plastic state

    SciTech Connect

    A.M. Gyul'maliev; S.G. Gagarin

    2007-02-15

    The structural-chemical simulation of the formation of plastic state during the thermal treatment (pyrolysis, coking) of coals is based on allowance for intermolecular interactions in the organic matter. The feasibility of transition of coals to the plastic state is determined by the ratio between the onset plastic state (softening) and runaway degradation temperatures, values that depend on the petrographic composition and the degree of metamorphism of coals and the distribution of structural and chemical characteristics of organic matter. 33 refs., 8 figs., 2 tabs.

  15. 76 FR 175 - Continental Structural Plastics Including On-Site Leased Workers From Kelly Services and Time...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-01-03

    ... Employment and Training Administration Continental Structural Plastics Including On-Site Leased Workers From... of Continental Structural Plastics, North Baltimore, Ohio. The notice was published in the Federal... Plastics. The Department has determined that these workers were sufficiently under the control of...

  16. Redistribution of Kv1 and Kv7 enhances neuronal excitability during structural axon initial segment plasticity

    PubMed Central

    Kuba, Hiroshi; Yamada, Rei; Ishiguro, Go; Adachi, Ryota

    2015-01-01

    Structural plasticity of the axon initial segment (AIS), the trigger zone of neurons, is a powerful means for regulating neuronal activity. Here, we show that AIS plasticity is not limited to structural changes; it also occurs as changes in ion-channel expression, which substantially augments the efficacy of regulation. In the avian cochlear nucleus, depriving afferent inputs by removing cochlea elongated the AIS, and simultaneously switched the dominant Kv channels at the AIS from Kv1.1 to Kv7.2. Due to the slow activation kinetics of Kv7.2, the redistribution of the Kv channels reduced the shunting conductance at the elongated AIS during the initiation of action potentials and effectively enhanced the excitability of the deprived neurons. The results indicate that the functional plasticity of the AIS works cooperatively with the structural plasticity and compensates for the loss of afferent inputs to maintain the homeostasis of auditory circuits after hearing loss by cochlea removal. PMID:26581625

  17. Studies on the effect of storage time and plasticizers on the structural variations in thermoplastic starch.

    PubMed

    Schmitt, H; Guidez, A; Prashantha, K; Soulestin, J; Lacrampe, M F; Krawczak, P

    2015-01-22

    Starch was combined with plasticizers such as glycerol, sorbitol, glycerol/sorbitol and urea/ethanolamine blends by means of high shear extrusion process to prepare thermoplastic starch (TPS). Effect of storage time and plasticizers on the structural stability of melt processed TPS was investigated. Morphological observation, X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy reveal that melt extrusion process is efficient in transforming granular starch into a plasticized starch for all plasticizer compositions. XRD analysis highlights major changes in the microstructure of plasticized starch, and dependence of crystalline type and degree of crystallinity mainly on the plasticizer composition and storage time. Dynamical mechanical analysis (DMA) yields a decrease of the peak intensity of loss factor with aging time. The effect of ageing on tensile strength also appears to be highly dependent on the plasticizer composition. Thus, through different plasticizer combinations and ageing, starch-based materials with significant differences in tensile properties can be obtained, which may be tuned to meet the requirements of a wide range of applications.

  18. Automated Remote Focusing, Drift Correction, and Photostimulation to Evaluate Structural Plasticity in Dendritic Spines

    PubMed Central

    Evans, Paul R.; Garrett, Tavita R.; Yan, Long; Yasuda, Ryohei

    2017-01-01

    Long-term structural plasticity of dendritic spines plays a key role in synaptic plasticity, the cellular basis for learning and memory. The biochemical step is mediated by a complex network of signaling proteins in spines. Two-photon imaging techniques combined with two-photon glutamate uncaging allows researchers to induce and quantify structural plasticity in single dendritic spines. However, this method is laborious and slow, making it unsuitable for high throughput screening of factors necessary for structural plasticity. Here we introduce a MATLAB-based module built for Scanimage to automatically track, image, and stimulate multiple dendritic spines. We implemented an electrically tunable lens in combination with a drift correction algorithm to rapidly and continuously track targeted spines and correct sample movements. With a straightforward user interface to design custom multi-position experiments, we were able to adequately image and produce targeted plasticity in multiple dendritic spines using glutamate uncaging. Our methods are inexpensive, open source, and provides up to a five-fold increase in throughput for quantifying structural plasticity of dendritic spines. PMID:28114380

  19. An upper bound on damage of elastic-plastic structures at shakedown

    NASA Astrophysics Data System (ADS)

    Feng, Xi-Qiao; Yu, Shou-Wen

    1994-07-01

    In this paper, a shakedown theory for plastic-damaged structures is presented. Damage mechanics and shakedown theory are closely related to each other in some aspects. The damage of materials may change their mechanical properties and as well as the shakedown load domains of structures. Here the damage variable is proposed as the failure criterion of ductile structures at shakedown. Based on an elastic prefectly-plastic damage model, an upper bound on local damage of structures is given via a mathematical programming. The suggested method is illustrated by an example of thick-walled cylindrical tube.

  20. Hyperbolic Structure for a Simplified Model of Dynamical Perfect Plasticity

    NASA Astrophysics Data System (ADS)

    Babadjian, Jean-François; Mifsud, Clément

    2017-02-01

    This paper is devoted to confronting two different approaches to the problem of dynamical perfect plasticity. Interpreting this model as a constrained boundary value Friedrichs' system enables one to derive admissible hyperbolic boundary conditions. Using variational methods, we show the well-posedness of this problem in a suitable weak measure theoretical setting. Thanks to the property of finite speed propagation, we establish a new regularity result for the solution in short time. Finally, we prove that this variational solution is actually a solution of the hyperbolic formulation in a suitable dissipative/entropic sense, and that a partial converse statement holds under an additional time regularity assumption for the dissipative solutions.

  1. Activity-dependent inhibitory synapse remodeling through gephyrin phosphorylation.

    PubMed

    Flores, Carmen E; Nikonenko, Irina; Mendez, Pablo; Fritschy, Jean-Marc; Tyagarajan, Shiva K; Muller, Dominique

    2015-01-06

    Maintaining a proper balance between excitation and inhibition is essential for the functioning of neuronal networks. However, little is known about the mechanisms through which excitatory activity can affect inhibitory synapse plasticity. Here we used tagged gephyrin, one of the main scaffolding proteins of the postsynaptic density at GABAergic synapses, to monitor the activity-dependent adaptation of perisomatic inhibitory synapses over prolonged periods of time in hippocampal slice cultures. We find that learning-related activity patterns known to induce N-methyl-D-aspartate (NMDA) receptor-dependent long-term potentiation and transient optogenetic activation of single neurons induce within hours a robust increase in the formation and size of gephyrin-tagged clusters at inhibitory synapses identified by correlated confocal electron microscopy. This inhibitory morphological plasticity was associated with an increase in spontaneous inhibitory activity but did not require activation of GABAA receptors. Importantly, this activity-dependent inhibitory plasticity was prevented by pharmacological blockade of Ca(2+)/calmodulin-dependent protein kinase II (CaMKII), it was associated with an increased phosphorylation of gephyrin on a site targeted by CaMKII, and could be prevented or mimicked by gephyrin phospho-mutants for this site. These results reveal a homeostatic mechanism through which activity regulates the dynamics and function of perisomatic inhibitory synapses, and they identify a CaMKII-dependent phosphorylation site on gephyrin as critically important for this process.

  2. Learning structure of sensory inputs with synaptic plasticity leads to interference

    PubMed Central

    Chrol-Cannon, Joseph; Jin, Yaochu

    2015-01-01

    Synaptic plasticity is often explored as a form of unsupervised adaptation in cortical microcircuits to learn the structure of complex sensory inputs and thereby improve performance of classification and prediction. The question of whether the specific structure of the input patterns is encoded in the structure of neural networks has been largely neglected. Existing studies that have analyzed input-specific structural adaptation have used simplified, synthetic inputs in contrast to complex and noisy patterns found in real-world sensory data. In this work, input-specific structural changes are analyzed for three empirically derived models of plasticity applied to three temporal sensory classification tasks that include complex, real-world visual and auditory data. Two forms of spike-timing dependent plasticity (STDP) and the Bienenstock-Cooper-Munro (BCM) plasticity rule are used to adapt the recurrent network structure during the training process before performance is tested on the pattern recognition tasks. It is shown that synaptic adaptation is highly sensitive to specific classes of input pattern. However, plasticity does not improve the performance on sensory pattern recognition tasks, partly due to synaptic interference between consecutively presented input samples. The changes in synaptic strength produced by one stimulus are reversed by the presentation of another, thus largely preventing input-specific synaptic changes from being retained in the structure of the network. To solve the problem of interference, we suggest that models of plasticity be extended to restrict neural activity and synaptic modification to a subset of the neural circuit, which is increasingly found to be the case in experimental neuroscience. PMID:26300769

  3. Chronic fluoxetine treatment alters the structure, connectivity and plasticity of cortical interneurons.

    PubMed

    Guirado, Ramon; Perez-Rando, Marta; Sanchez-Matarredona, David; Castrén, Eero; Nacher, Juan

    2014-10-01

    Novel hypotheses suggest that antidepressants, such as the selective serotonin reuptake inhibitor fluoxetine, induce neuronal structural plasticity, resembling that of the juvenile brain, although the underlying mechanisms of this reopening of the critical periods still remain unclear. However, recent studies suggest that inhibitory networks play an important role in this structural plasticity induced by fluoxetine. For this reason we have analysed the effects of a chronic fluoxetine treatment in the hippocampus and medial prefrontal cortex (mPFC) of transgenic mice displaying eGFP labelled interneurons. We have found an increase in the expression of molecules related to critical period plasticity, such as the polysialylated form of the neural cell adhesion molecule (PSA-NCAM), GAD67/65 and synaptophysin, as well as a reduction in the number of parvalbumin expressing interneurons surrounded by perineuronal nets. We have also described a trend towards decrease in the perisomatic inhibitory puncta on pyramidal neurons in the mPFC and an increase in the density of inhibitory puncta on eGFP interneurons. Finally, we have found that chronic fluoxetine treatment affects the structure of interneurons in the mPFC, increasing their dendritic spine density. The present study provides evidence indicating that fluoxetine promotes structural changes in the inhibitory neurons of the adult cerebral cortex, probably through alterations in plasticity-related molecules of neurons or the extracellular matrix surrounding them, which are present in interneurons and are known to be crucial for the development of the critical periods of plasticity in the juvenile brain.

  4. Discussion on Applicability of Rigid Plastic Dynamic Deformation Analysis to Soil Structures

    NASA Astrophysics Data System (ADS)

    Hoshina, Takashi; Ohtsuka, Satoru; Isobe, Koichi

    This paper proposes a new analysis method to estimate a residual deformation of soil structure for external loads. It employs a rigid plastic constitutive equation for soil which needs a small number of soil constants in comparison with general elasto-plastic constitutive equations. The purpose of this method is to simulate a large amount of deformation caused by failure of soil structure based on finite deformation theory. The features of proposed method are (1) simulation for large deformation of soil structure, (2) no effect of initial stress distribution, and (3) application to dynamic load. This study expresses the formulation of rigid plastic dynamic finite element method based on finite deformation theory. It examines the applicability of proposed method by applying to Prandtl's limit bearing capacity of foundation for static monotonically increasing load. The result clearly shows the applicability of rigid plastic constitutive equation to deformation analysis. Both kinematical effect and time rate dependency on limit bearing capacity were clearly presented by employing Rigid Plastic Dynamic Deformation Analysis Method.

  5. Simultaneous imaging of structural plasticity and calcium dynamics in developing dendrites and axons.

    PubMed

    Siegel, Friederike; Lohmann, Christian

    2013-11-01

    During nervous system development, the formation of synapses between pre- and postsynaptic neurons is a remarkably specific process. Both structural and functional plasticity are critical for the selection of synaptic partners and for the establishment and maturation of synapses. To unravel the respective contributions of structural and functional mechanisms as well as their interactions during synaptogenesis, it is important to directly observe structural changes and functional signaling simultaneously. Here, we present an imaging approach to simultaneously follow changes in structure and function. Differential labeling of individual cells and the neuronal network with distinct dyes allows the study of structural plasticity and changes in calcium signaling associated with neural activity at the same time and with high resolution. This is achieved by bulk loading of neuronal populations with a calcium-sensitive indicator in combination with electroporation of individual cells with a calcium indicator and an additional noncalcium-sensitive dye with a different excitation spectrum. Recordings of the two differently labeled structures can be acquired simultaneously using confocal microscopy. Thus, structural plasticity and calcium dynamics of the individually labeled neuron and the surrounding network can be related to each other. This combined imaging approach can be applied to virtually all systems of neuronal networks to study structure and function. We provide a comprehensive description of the labeling procedure, the imaging parameters, and the important aspects of analysis for simultaneous recordings of structure and function in individual neurons.

  6. Hippocampal Structural Plasticity Accompanies the Resulting Contextual Fear Memory Following Stress and Fear Conditioning

    ERIC Educational Resources Information Center

    Giachero, Marcelo; Calfa, Gaston D.; Molina, Victor A.

    2013-01-01

    The present research investigated the resulting contextual fear memory and structural plasticity changes in the dorsal hippocampus (DH) following stress and fear conditioning. This combination enhanced fear retention and increased the number of total and mature dendritic spines in DH. Intra-basolateral amygdala (BLA) infusion of midazolam prior to…

  7. Learning to Perceive Structure from Motion and Neural Plasticity in Patients with Alzheimer's Disease

    ERIC Educational Resources Information Center

    Kim, Nam-Gyoon; Park, Jong-Hee

    2010-01-01

    Recent research has demonstrated that Alzheimer's disease (AD) affects the visual sensory pathways, producing a variety of visual deficits, including the capacity to perceive structure-from-motion (SFM). Because the sensory areas of the adult brain are known to retain a large degree of plasticity, the present study was conducted to explore whether…

  8. Effects of plasticization and shear stress on phase structure development and properties of soy protein blends.

    PubMed

    Chen, Feng; Zhang, Jinwen

    2010-11-01

    In this study, soy protein concentrate (SPC) was used as a plastic component to blend with poly(butylene adipate-co-terephthalate) (PBAT). Effects of SPC plasticization and blend composition on its deformation during mixing were studied in detail. Influence of using water as the major plasticizer and glycerol as the co-plasticizer on the deformation of the SPC phase during mixing was explored. The effect of shear stress, as affected by SPC loading level, on the phase structure of SPC in the blends was also investigated. Quantitative analysis of the aspect ratio of SPC particles was conducted by using ImageJ software, and an empirical model predicting the formation of percolated structure was applied. The experimental results and the model prediction showed a fairly good agreement. The experimental results and statistic analysis suggest that both SPC loading level and its water content prior to compounding had significant influences on development of the SPC phase structure and were correlated in determining the morphological structures of the resulting blends. Consequently, physical and mechanical properties of the blends greatly depended on the phase morphology and PBAT/SPC ratio of the blends.

  9. Plasticity beyond peri-infarct cortex: spinal up regulation of structural plasticity, neurotrophins, and inflammatory cytokines during recovery from cortical stroke.

    PubMed

    Sist, Bernice; Fouad, Karim; Winship, Ian R

    2014-02-01

    Stroke induces pathophysiological and adaptive processes in regions proximal and distal to the infarct. Recent studies suggest that plasticity at the level of the spinal cord may contribute to sensorimotor recovery after cortical stroke. Here, we compare the time course of heightened structural plasticity in the spinal cord against the temporal profile of cortical plasticity and spontaneous behavioral recovery. To examine the relation between trophic and inflammatory effectors and spinal structural plasticity, spinal expression of brain derived neurotrophic factor (BDNF), neurotrophin-3 (NT-3), tumor necrosis factor-α (TNF-α), and interleukin-6 (IL-6) was measured. Growth-associated protein 43 (GAP-43), measured at 3, 7, 14, or 28 days after photothrombotic stroke of the forelimb sensorimotor cortex (FL-SMC) to provide an index of periods of heightened structural plasticity, varied as a function of lesion size and time after stroke in the cortical hemispheres and the spinal cord. Notably, GAP-43 levels in the cervical spinal cord were significantly increased after FL-SMC lesion, but the temporal window of elevated structural plasticity was more finite in spinal cord relative to ipsilesional cortical expression (returning to baseline levels by 28 post-stroke). Peak GAP-43 expression in spinal cord occurred during periods of accelerated spontaneous recovery, as measured on the Montoya Staircase reaching task, and returned to baseline as recovery plateaued. Interestingly, spinal GAP-43 levels were significantly correlated with spinal levels of the inflammatory cytokines TNF-α and IL-6 as well as the neurotrophin NT-3, while a transient increase in BDNF levels preceded elevated GAP-43 expression. These data identify a significant but time-limited window of heightened structural plasticity in the spinal cord following stroke that correlates with spontaneous recovery and the spinal expression of inflammatory cytokines and neurotrophic factors.

  10. Novel activity-dependent approaches to therapeutic hypnosis and psychotherapy: the general waking trance.

    PubMed

    Rossi, Ernest; Erickson-Klein, Roxanna; Rossi, Kathryn

    2008-10-01

    This paper presents a highly edited version of a videotape made in 1980 by Marion Moore, M.D., showing Milton H. Erickson and Moore demonstrating novel, activity-dependent approaches to hand-levitation and therapeutic hypnosis on their subject, Ernest Rossi. Erickson's naturalistic and utilization approach is described in his very direct and surprising induction in a trance challenged patient. These novel, and surprising inductions are examples of how Erickson was prescient in developing activity-dependent approaches to therapeutic hypnosis and psychotherapy several generations before modern neuroscience documented the activity-dependent molecular-genomic mechanisms of memory, learning, and behavior change. Erickson describes a case where he utilized what he called, "The General Waking Trance" when he "dared" not use an obvious hypnotic induction. It is proposed that the states of intense mental absorption and response attentiveness that are facilitated by the general waking trance are functionally related to the three conditions neuroscientists have identified as novelty, enrichment, and exercise (both mental and physical), which can turn on activity-dependent gene expression and activity-dependent brain plasticity, that are the molecular-genomic and neural basis ofmemory, learning, consciousness, and behavior change. We recommend that the next step in investigating the efficacy of therapeutic hypnosis will be in partnering with neuroscientists to explore the possibilities and limitations of utilizing the activity-dependent approaches to hypnotic induction and the general waking trance in facilitating activity-dependent gene expression and brain plasticity.

  11. Structurally Enhanced Self-Plasticization of Poly(vinyl chloride) via Click Grafting of Hyperbranched Polyglycerol.

    PubMed

    Lee, Kyu Won; Chung, Jae Woo; Kwak, Seung-Yeop

    2016-12-01

    A highly self-plasticized poly(vinyl chloride) (PVC) is demonstrated for the first time via click grafting of hyperbranched polyglycerol (HPG). The plasticizing effect of the grafted HPG on PVC is systematically investigated by various analytical methods. The amorphous and bulky dendritic structure of HPG efficiently increases the free volume of the grafted PVC, which leads to a remarkably lower glass transition temperature comparable to that of the conventional plasticized PVC. Viscoelastic analysis reveals that HPG considerably improves the softness of the grafted PVC at room temperature and promotes the segmental motion in the system. The HPG-grafted PVC films exhibit an exceptional stretchability unlike the mixture of PVC and HPG because the covalent attachment of HPG to PVC allows it to maintain its homogeneous and well-organized architecture under tensile stretching. The work provides valuable insights into the design of highly flexible and stretchable polymeric materials by means of introducing hyperbranched side chains.

  12. Functional and structural plasticity in the primary somatosensory cortex associated with chronic pain.

    PubMed

    Kim, Woojin; Kim, Sun Kwang; Nabekura, Junichi

    2017-03-09

    Tissue or nerve injury induces widespread plastic changes from the periphery and spinal cord up to the cortex, resulting in chronic pain. Although many clinicians and researchers have extensively studied altered nociceptive signaling and neural circuit plasticity at the spinal cord level, effective treatments to ameliorate chronic pain are still insufficient. For about the last two decades, the rapid development in macroscopic brain imaging studies on humans and animal models have revealed maladaptive plastic changes in the 'pain matrix' brain regions, which may subsequently contribute to chronic pain. Among these brain regions, our group has concentrated for many years on the primary somatosensory (S1) cortex with a help of advanced imaging techniques and has found the functional and structural changes in neurons/glia as well as individual synapses in the S1 cortex during chronic pain. Taken together, it is now believed that such S1 plasticity is one of the causes for chronic pain, not a simple and passive epiphenomenon following tissue/nerve injury as previously thought. In this small review, we discuss the relation of plasticity in the S1 cortex with chronic pain, based on clinical trials and experimental studies conducted on this field. This article is protected by copyright. All rights reserved.

  13. Binocular vision in amblyopia: structure, suppression and plasticity.

    PubMed

    Hess, Robert F; Thompson, Benjamin; Baker, Daniel H

    2014-03-01

    The amblyopic visual system was once considered to be structurally monocular. However, it now evident that the capacity for binocular vision is present in many observers with amblyopia. This has led to new techniques for quantifying suppression that have provided insights into the relationship between suppression and the monocular and binocular visual deficits experienced by amblyopes. Furthermore, new treatments are emerging that directly target suppressive interactions within the visual cortex and, on the basis of initial data, appear to improve both binocular and monocular visual function, even in adults with amblyopia. The aim of this review is to provide an overview of recent studies that have investigated the structure, measurement and treatment of binocular vision in observers with strabismic, anisometropic and mixed amblyopia.

  14. Plastic-Based Structurally Programmable Microfluidic Biochips for Clinical Diagnostics

    DTIC Science & Technology

    2005-05-01

    oxidation and doping of the generated PANI. A novel approach along with a structure- property study for ZrO2 and TiO2 filled PDMS was performed. A...derive the expression for pressure needed to overcome the passive valve as: ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎣ ⎡ ⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ +−⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ +=∆ 2211 2 1111) cos ...21 2 11) cos (2 ww P cl θσ (III-3) The passive valve shown in Figure III-23 is not an optimum geometry for the biochip

  15. Structural Plasticity of Dentate Granule Cell Mossy Fibers During the Development of Limbic Epilepsy

    PubMed Central

    Danzer, Steve C.; He, Xiaoping; Loepke, Andreas W.; McNamara, James O.

    2009-01-01

    Altered granule cell≫CA3 pyramidal cell synaptic connectivity may contribute to the development of limbic epilepsy. To explore this possibility, granule cell giant mossy fiber bouton plasticity was examined in the kindling and pilocarpine models of epilepsy using green fluorescent protein-expressing transgenic mice. These studies revealed significant increases in the frequency of giant boutons with satellite boutons 2 days and 1 month after pilocarpine status epilepticus, and increases in giant bouton area at 1 month. Similar increases in giant bouton area were observed shortly after kindling. Finally, both models exhibited plasticity of mossy fiber giant bouton filopodia, which contact GABAergic interneurons mediating feedforward inhibition of CA3 pyramids. In the kindling model, however, all changes were fleeting, having resolved by 1 month after the last evoked seizure. Together, these findings demonstrate striking structural plasticity of granule cell mossy fiber synaptic terminal structure in two distinct models of adult limbic epileptogenesis. We suggest that these plasticities modify local connectivities between individual mossy fiber terminals and their targets, inhibitory interneurons, and CA3 pyramidal cells potentially altering the balance of excitation and inhibition during the development of epilepsy. PMID:19294647

  16. Thermoelectric plastics: from design to synthesis, processing and structure-property relationships.

    PubMed

    Kroon, Renee; Mengistie, Desalegn Alemu; Kiefer, David; Hynynen, Jonna; Ryan, Jason D; Yu, Liyang; Müller, Christian

    2016-11-07

    Thermoelectric plastics are a class of polymer-based materials that combine the ability to directly convert heat to electricity, and vice versa, with ease of processing. Potential applications include waste heat recovery, spot cooling and miniature power sources for autonomous electronics. Recent progress has led to surging interest in organic thermoelectrics. This tutorial review discusses the current trends in the field with regard to the four main building blocks of thermoelectric plastics: (1) organic semiconductors and in particular conjugated polymers, (2) dopants and counterions, (3) insulating polymers, and (4) conductive fillers. The design and synthesis of conjugated polymers that promise to show good thermoelectric properties are explored, followed by an overview of relevant structure-property relationships. Doping of conjugated polymers is discussed and its interplay with processing as well as structure formation is elucidated. The use of insulating polymers as binders or matrices is proposed, which permit the adjustment of the rheological and mechanical properties of a thermoelectric plastic. Then, nanocomposites of conductive fillers such as carbon nanotubes, graphene and inorganic nanowires in a polymer matrix are introduced. A case study examines poly(3,4-ethylenedioxythiophene) (PEDOT) based materials, which up to now have shown the most promising thermoelectric performance. Finally, a discussion of the advantages provided by bulk architectures e.g. for wearable applications highlights the unique advantages that thermoelectric plastics promise to offer.

  17. Structure and Plasticity of Endophilin and Sorting Nexin 9

    SciTech Connect

    Wang, Qi; Kaan, Hung Yi Kristal; Hooda, Reshma Noordin; Goh, Shih Lin; Sondermann, Holger

    2009-06-17

    Endophilin and Sorting Nexin 9 (Snx9) play key roles in endocytosis by membrane curvature sensing and remodeling via their Bin/Amphiphysin/Rvs (BAR) domains. BAR and the related F-BAR domains form dimeric, crescent-shaped units that occur N- or C-terminally to other lipid-binding, adaptor, or catalytic modules. In crystal structures, the PX-BAR unit of Snx9 (Snx9{sup PX-BAR}) adopts an overall compact, moderately curved conformation. SAXS-based solution studies revealed an alternative, more curved state of Snx9{sup PX-BAR} in which the PX domains are flexibly connected to the BAR domains, providing a model for how Snx9 exhibits lipid-dependent curvature preferences. In contrast, Endophilin appears to be rigid in solution, and the SH3 domains are located at the distal tips of a BAR domain dimer with fixed curvature. We also observed tip-to-tip interactions between the BAR domains in a trigonal crystal form of Snx9PX-BAR reminiscent of functionally important interactions described for F-BAR domains.

  18. Structural Plasticity Controlled by Calcium Based Correlation Detection

    PubMed Central

    Helias, Moritz; Rotter, Stefan; Gewaltig, Marc-Oliver; Diesmann, Markus

    2008-01-01

    Hebbian learning in cortical networks during development and adulthood relies on the presence of a mechanism to detect correlation between the presynaptic and the postsynaptic spiking activity. Recently, the calcium concentration in spines was experimentally shown to be a correlation sensitive signal with the necessary properties: it is confined to the spine volume, it depends on the relative timing of pre- and postsynaptic action potentials, and it is independent of the spine's location along the dendrite. NMDA receptors are a candidate mediator for the correlation dependent calcium signal. Here, we present a quantitative model of correlation detection in synapses based on the calcium influx through NMDA receptors under realistic conditions of irregular pre- and postsynaptic spiking activity with pairwise correlation. Our analytical framework captures the interaction of the learning rule and the correlation dynamics of the neurons. We find that a simple thresholding mechanism can act as a sensitive and reliable correlation detector at physiological firing rates. Furthermore, the mechanism is sensitive to correlation among afferent synapses by cooperation and competition. In our model this mechanism controls synapse formation and elimination. We explain how synapse elimination leads to firing rate homeostasis and show that the connectivity structure is shaped by the correlations between neighboring inputs. PMID:19129936

  19. Bidirectional Synaptic Structural Plasticity after Chronic Cocaine Administration Occurs through Rap1 Small GTPase Signaling.

    PubMed

    Cahill, Michael E; Bagot, Rosemary C; Gancarz, Amy M; Walker, Deena M; Sun, HaoSheng; Wang, Zi-Jun; Heller, Elizabeth A; Feng, Jian; Kennedy, Pamela J; Koo, Ja Wook; Cates, Hannah M; Neve, Rachael L; Shen, Li; Dietz, David M; Nestler, Eric J

    2016-02-03

    Dendritic spines are the sites of most excitatory synapses in the CNS, and opposing alterations in the synaptic structure of medium spiny neurons (MSNs) of the nucleus accumbens (NAc), a primary brain reward region, are seen at early versus late time points after cocaine administration. Here we investigate the time-dependent molecular and biochemical processes that regulate this bidirectional synaptic structural plasticity of NAc MSNs and associated changes in cocaine reward in response to chronic cocaine exposure. Our findings reveal key roles for the bidirectional synaptic expression of the Rap1b small GTPase and an associated local synaptic protein translation network in this process. The transcriptional mechanisms and pathway-specific inputs to NAc that regulate Rap1b expression are also characterized. Collectively, these findings provide a precise mechanism by which nuclear to synaptic interactions induce "metaplasticity" in NAc MSNs, and we reveal the specific effects of this plasticity on reward behavior in a brain circuit-specific manner.

  20. What is the structure of a polymer glass after plastic deformation?

    NASA Astrophysics Data System (ADS)

    Montes, Helene; Lequeux, Francois; Alba-Simionesco, Christiane; Casas, Frederic

    2008-03-01

    We aim to study the effect of plastic deformation on the structure of a glassy polymer. Using neutrons scattering on a large range of length scales, and comparing samples deformed below and above Tg, we show that: 1) The deformation is extremely homogeneous (or affine) for length scales above the entanglement distance 2) The crossover length scale between affine and non affine deeformation is about half the one of the entanglements, and is independent of temperature below the glass transition 3) The arrangement of the polymer chain is distorded by plastic deformation at the atomic scale We then discuss these results and compare them to the results of the simulation of Hoy and Robbins (J. Polym. Sci., 44 (2006), 3487). As a conclusion we see that the entanglements are respopnsible for the very homogeneous deformations, forcing the individual plastic events to propagate in the sample following the tension of the chains. Thus we conclude that the physics of the plastic deformation of polymer glasses are very different from the one of other glasses.

  1. Smaller is Plastic: Polymorphic Structures and Mechanism of Deformation in Nanoscale hcp Metals.

    PubMed

    Bhogra, Meha; Ramamurty, U; Waghmare, Umesh V

    2015-06-10

    Using first-principles calculations, we establish the existence of highly stable polymorphs of hcp metals (Ti, Mg, Be, La and Y) with nanoscale structural periodicity. They arise from heterogeneous deformation of the hcp structure occurring in response to large shear stresses localized at the basal planes separated by a few nanometers. Through Landau theoretical analysis, we show that their stability derives from nonlinear coupling between strains at different length scales. Such multiscale hyperelasticity and long-period structures constitute a new mechanism of size-dependent plasticity and its enhancement in nanoscale hcp metals.

  2. Structure and deformation behavior of Armco iron subjected to severe plastic deformation

    SciTech Connect

    Valiev, R.Z. |; Rauch, E.F.; Baudelet, B.; Ivanisenko, Yu.V.

    1996-12-01

    Structural evolutions in an Armco iron subjected to severe plastic deformation by torsion under high pressure are analyzed with conventional and high resolution electron microscopes. The substructure observed at low strains appears to shrink with increasing deformation and transforms at very high strains into grain boundaries. The resulting grain size decreases down to a constant submicrometric value. Meanwhile, the material strength, as revealed by micro hardness measurements, levels out. Dislocation densities and internal stress levels are used to discuss the structural transformations. Hydrostatic pressure and deformation temperature are believed to modify the steady-state stress level and structural size by impeding the recovery processes involving diffusion.

  3. Homeostatic structural plasticity can account for topology changes following deafferentation and focal stroke.

    PubMed

    Butz, Markus; Steenbuck, Ines D; van Ooyen, Arjen

    2014-01-01

    After brain lesions caused by tumors or stroke, or after lasting loss of input (deafferentation), inter- and intra-regional brain networks respond with complex changes in topology. Not only areas directly affected by the lesion but also regions remote from the lesion may alter their connectivity-a phenomenon known as diaschisis. Changes in network topology after brain lesions can lead to cognitive decline and increasing functional disability. However, the principles governing changes in network topology are poorly understood. Here, we investigated whether homeostatic structural plasticity can account for changes in network topology after deafferentation and brain lesions. Homeostatic structural plasticity postulates that neurons aim to maintain a desired level of electrical activity by deleting synapses when neuronal activity is too high and by providing new synaptic contacts when activity is too low. Using our Model of Structural Plasticity, we explored how local changes in connectivity induced by a focal loss of input affected global network topology. In accordance with experimental and clinical data, we found that after partial deafferentation, the network as a whole became more random, although it maintained its small-world topology, while deafferentated neurons increased their betweenness centrality as they rewired and returned to the homeostatic range of activity. Furthermore, deafferentated neurons increased their global but decreased their local efficiency and got longer tailed degree distributions, indicating the emergence of hub neurons. Together, our results suggest that homeostatic structural plasticity may be an important driving force for lesion-induced network reorganization and that the increase in betweenness centrality of deafferentated areas may hold as a biomarker for brain repair.

  4. Activity-Dependent Neuronal Model on Complex Networks

    PubMed Central

    de Arcangelis, Lucilla; Herrmann, Hans J.

    2012-01-01

    Neuronal avalanches are a novel mode of activity in neuronal networks, experimentally found in vitro and in vivo, and exhibit a robust critical behavior: these avalanches are characterized by a power law distribution for the size and duration, features found in other problems in the context of the physics of complex systems. We present a recent model inspired in self-organized criticality, which consists of an electrical network with threshold firing, refractory period, and activity-dependent synaptic plasticity. The model reproduces the critical behavior of the distribution of avalanche sizes and durations measured experimentally. Moreover, the power spectra of the electrical signal reproduce very robustly the power law behavior found in human electroencephalogram (EEG) spectra. We implement this model on a variety of complex networks, i.e., regular, small-world, and scale-free and verify the robustness of the critical behavior. PMID:22470347

  5. Elastic-Plastic Strain Acceptance Criteria for Structures Subject to Rapidly Applied Transient Dynamic Loading

    SciTech Connect

    W.R. Solonick

    2003-04-01

    Rapidly applied transient dynamic loads produce stresses and deflections in structures that typically exceed those from static loading conditions. Previous acceptance criteria for structures designed for rapidly applied transient dynamic loading limited stresses to those determined from elastic analysis. Different stress limits were established for different grades of structure depending upon the amount of permanent set considered acceptable. Structure allowed to sustain very limited permanent set is designed to stress limits not significantly greater than yield stress. Greater permanent set in structure under rapidly applied transient dynamic loading conditions is permitted by establishing stress limits that are significantly greater than yield stress but still provide adequate safety margin (with respect to failure). This paper presents a strain-based elastic-plastic (i.e., inelastic) analysis criterion developed as an alternative to the more conservative stress-based elastic analysis stress criterion for structures subjected to rapidly applied transient dynamic loading. The strain limits established are based on material ductility considerations only and are set as a fraction of the strain at ultimate stress obtained from an engineering stress/strain curve of the material. Strains limits are categorized by type as membrane or surface and by region as general, local , or concentrated. The application of the elastic-plastic criterion provides a more accurate, less conservative design/analysis basis for structures than that used in elastic stress-based analysis criteria, while still providing adequate safety margins.

  6. Elastic-plastic strain acceptance criterion for structures subject to rapidly applied transient dynamic loading

    SciTech Connect

    Solonick, W.

    1996-11-01

    Rapidly applied transient dynamic loads produce stresses and deflections in structures that typically exceed those from static loading conditions. Previous acceptance criteria for structures designed for rapidly applied transient dynamic loading limited stresses to those determined from elastic analysis. Different stress limits were established for different grades of structure depending upon the amount of permanent set considered acceptable. Structure allowed to sustain very limited permanent set is designed to stress limits not significantly greater than yield stress. Greater permanent set in structure under rapidly applied transient dynamic loading conditions is permitted by establishing stress limits that are significantly greater than yield stress but still provide adequate safety margin (with respect to failure). This paper presents a strain-based elastic-plastic (i.e., inelastic) analysis criterion developed as an alternative to the more conservative stress-based elastic analysis stress criterion for structures subjected to rapidly applied transient dynamic loading. The strain limits established are based on a fraction of the strain at ultimate stress obtained from an engineering stress/strain curve of the material. Strains limits are categorized by type as membrane or surface and by region as general, local, or concentrated. The application of the elastic-plastic criterion provides a more accurate, less conservative design/analysis basis for structures than that used in elastic stress-based analysis criteria, while still providing adequate safety margins.

  7. Mild Thyroid Hormone Insufficiency During Development Compromises Activity-Dependent Neuroplasticity in the Hippocampus of Adult Male Rats.

    PubMed

    Gilbert, M E; Sanchez-Huerta, K; Wood, C

    2016-02-01

    Severe thyroid hormone (TH) deficiency during critical phases of brain development results in irreversible neurological and cognitive impairments. The mechanisms accounting for this are likely multifactorial, and are not fully understood. Here we pursue the possibility that one important element is that TH affects basal and activity-dependent neurotrophin expression in brain regions important for neural processing. Graded exposure to propylthiouracil (PTU) during development produced dose-dependent reductions in mRNA expression of nerve growth factor (Ngf) in whole hippocampus of neonates. These changes in basal expression persisted to adulthood despite the return to euthyroid conditions in blood. In contrast to small PTU-induced reductions in basal expression of several genes, developmental PTU treatment dramatically reduced the activity-dependent expression of neurotrophins and related genes (Bdnft, Bdnfiv, Arc, and Klf9) in adulthood and was accompanied by deficits in hippocampal-based learning. These data demonstrate that mild TH insufficiency during development not only reduces expression of important neurotrophins that persists into adulthood but also severely restricts the activity-dependent induction of these genes. Considering the importance of these neurotrophins for sculpting the structural and functional synaptic architecture in the developing and the mature brain, it is likely that TH-mediated deficits in these plasticity mechanisms contribute to the cognitive deficiencies that accompany developmental TH compromise.

  8. Dislocation subgrain structures and modeling the plastic hardening of metallic single crystals

    NASA Astrophysics Data System (ADS)

    Hansen, B. L.; Bronkhorst, C. A.; Ortiz, M.

    2010-07-01

    A single crystal plasticity theory for insertion into finite element simulation is formulated using sequential laminates to model subgrain dislocation structures. It is known that local models do not adequately account for latent hardening, as latent hardening is not only a material property, but a nonlocal property (e.g. grain size and shape). The addition of the nonlocal energy from the formation of subgrain structure dislocation walls and the boundary layer misfits provide both latent and self-hardening of a crystal slip. Latent hardening occurs as the formation of new dislocation walls limits motion of new mobile dislocations, thus hardening future slip systems. Self-hardening is accomplished by an evolution of the subgrain structure length scale. The substructure length scale is computed by minimizing the nonlocal energy. The minimization of the nonlocal energy is a competition between the dislocation wall energy and the boundary layer energies. The nonlocal terms are also directly minimized within the subgrain model as they affect deformation response. The geometrical relationship between the dislocation walls and slip planes affecting the dislocation mean free path is taken into account, giving a first-order approximation to shape effects. A coplanar slip model is developed due to requirements while modeling the subgrain structure. This subgrain structure plasticity model is noteworthy as all material parameters are experimentally determined rather than fit. The model also has an inherit path dependence due to the formation of the subgrain structures. Validation is accomplished by comparison with single crystal tension test results.

  9. Learning the structure of correlated synaptic subgroups using stable and competitive spike-timing-dependent plasticity.

    PubMed

    Meffin, H; Besson, J; Burkitt, A N; Grayden, D B

    2006-04-01

    Synaptic plasticity must be both competitive and stable if ongoing learning of the structure of neural inputs is to occur. In this paper, a wide class of spike-timing-dependent plasticity (STDP) models is identified that have both of these desirable properties in the case in which the input consists of subgroups of synapses that are correlated within the subgroup through the occurrence of simultaneous input spikes. The process of synaptic structure formation is studied, illustrating one particular class of these models. When the learning rate is small, multiple alternative synaptic structures are possible given the same inputs, with the outcome depending on the initial weight configuration. For large learning rates, the synaptic structure does not stabilize, resulting in neurons without consistent response properties. For learning rates in between, a unique and stable synaptic structure typically forms. When this synaptic structure exhibits a bimodal distribution, the neuron will respond selectively to one or more of the subgroups. The robustness with which this selectivity develops during learning is largely determined by the ratio of the subgroup correlation strength to the number of subgroups. The fraction of potentiated subgroups is primarily determined by the balance between potentiation and depression.

  10. CD44: a novel synaptic cell adhesion molecule regulating structural and functional plasticity of dendritic spines

    PubMed Central

    Roszkowska, Matylda; Skupien, Anna; Wójtowicz, Tomasz; Konopka, Anna; Gorlewicz, Adam; Kisiel, Magdalena; Bekisz, Marek; Ruszczycki, Blazej; Dolezyczek, Hubert; Rejmak, Emilia; Knapska, Ewelina; Mozrzymas, Jerzy W.; Wlodarczyk, Jakub; Wilczynski, Grzegorz M.; Dzwonek, Joanna

    2016-01-01

    Synaptic cell adhesion molecules regulate signal transduction, synaptic function, and plasticity. However, their role in neuronal interactions with the extracellular matrix (ECM) is not well understood. Here we report that the CD44, a transmembrane receptor for hyaluronan, modulates synaptic plasticity. High-resolution ultrastructural analysis showed that CD44 was localized at mature synapses in the adult brain. The reduced expression of CD44 affected the synaptic excitatory transmission of primary hippocampal neurons, simultaneously modifying dendritic spine shape. The frequency of miniature excitatory postsynaptic currents decreased, accompanied by dendritic spine elongation and thinning. These structural and functional alterations went along with a decrease in the number of presynaptic Bassoon puncta, together with a reduction of PSD-95 levels at dendritic spines, suggesting a reduced number of functional synapses. Lack of CD44 also abrogated spine head enlargement upon neuronal stimulation. Moreover, our results indicate that CD44 contributes to proper dendritic spine shape and function by modulating the activity of actin cytoskeleton regulators, that is, Rho GTPases (RhoA, Rac1, and Cdc42). Thus CD44 appears to be a novel molecular player regulating functional and structural plasticity of dendritic spines. PMID:27798233

  11. Extracellular matrix control of dendritic spine and synapse structure and plasticity in adulthood

    PubMed Central

    Levy, Aaron D.; Omar, Mitchell H.; Koleske, Anthony J.

    2014-01-01

    Dendritic spines are the receptive contacts at most excitatory synapses in the central nervous system. Spines are dynamic in the developing brain, changing shape as they mature as well as appearing and disappearing as they make and break connections. Spines become much more stable in adulthood, and spine structure must be actively maintained to support established circuit function. At the same time, adult spines must retain some plasticity so their structure can be modified by activity and experience. As such, the regulation of spine stability and remodeling in the adult animal is critical for normal function, and disruption of these processes is associated with a variety of late onset diseases including schizophrenia and Alzheimer’s disease. The extracellular matrix (ECM), composed of a meshwork of proteins and proteoglycans, is a critical regulator of spine and synapse stability and plasticity. While the role of ECM receptors in spine regulation has been extensively studied, considerably less research has focused directly on the role of specific ECM ligands. Here, we review the evidence for a role of several brain ECM ligands and remodeling proteases in the regulation of dendritic spine and synapse formation, plasticity, and stability in adults. PMID:25368556

  12. Dietary cholesterol alters memory and synaptic structural plasticity in young rat brain.

    PubMed

    Ya, Bai-liu; Liu, Wen-yan; Ge, Feng; Zhang, Yan-xia; Zhu, Bao-liang; Bai, Bo

    2013-08-01

    Cholesterol plays an important role in synaptic plasticity, learning and memory. To better explore how dietary cholesterol contributes to learning and memory and the related changes in synaptic structural plasticity, rats were categorized into a regular diet (RD) group and a cholesterol-enriched diet (CD) group, and were fed with respective diet for 2 months. Dietary cholesterol impacts on learning and memory, hippocampal synaptic ultrastructure, expression levels of postsynaptic density-95 (PSD-95), synaptophysin (SYP) and cannabinoid receptor type 1 (CB1R) were investigated. We found CD rats had better performances in learning and memory using Morris water maze and object recognition test than RD rats. The memory improvement was accompanied with alterations of synaptic ultrastructure in the CA1 area of the hippocampus evaluated by electron microscopy, enhanced immunoreactivity of SYP, a presynaptic marker in hippocampus detected by immunocytochemistry, as well as increased levels of PSD-95, SYP and decreased level of CB1R in brains of CD rats determined by Western blot. Taken together, the results suggest that the improvement of learning and memory abilities of the young adult rats induced by dietary cholesterol may be linked with changes in synaptic structural plasticity in the brain.

  13. Computer simulation of model cohesive powders: Plastic consolidation, structural changes, and elasticity under isotropic loads

    NASA Astrophysics Data System (ADS)

    Gilabert, F. A.; Roux, J.-N.; Castellanos, A.

    2008-09-01

    The quasistatic behavior of a simple two-dimensional model of a cohesive powder under isotropic loads is investigated by discrete element simulations. We ignore contact plasticity and focus on the effect of geometry and collective rearrangements on the material behavior. The loose packing states, as assembled and characterized in a previous numerical study [Gilabert, Roux, and Castellanos, Phys. Rev. E 75, 011303 (2007)], are observed, under growing confining pressure P , to undergo important structural changes, while solid fraction Φ irreversibly increases (typically, from 0.4-0.5 to 0.75-0.8). The system state goes through three stages, with different forms of the plastic consolidation curve, i.e., Φ as a function of the growing reduced pressure P*=Pa/F0 , defined with adhesion force F0 and grain diameter a . In the low-confinement regime (I), the system undergoes negligible plastic compaction, and its structure is influenced by the assembling process. In regime II the material state is independent of initial conditions, and the void ratio varies linearly with lnP [i.e., Δ(1/Φ)=λΔ(lnP*) ], as described in the engineering literature. Plasticity index λ is reduced in the presence of a small rolling resistance (RR). In the last stage of compaction (III), Φ approaches an asymptotic, maximum solid fraction Φmax , as a power law Φmax-Φ∝(P*)-α , with α≃1 , and properties of cohesionless granular packs are gradually retrieved. Under consolidation, while the range ξ of fractal density correlations decreases, force patterns reorganize from self-balanced clusters to force chains, with correlative evolutions of force distributions, and elastic moduli increase by a large amount. Plastic deformation events correspond to very small changes in the network topology, while the denser regions tend to move like rigid bodies. Elastic properties are dominated by the bending of thin junctions in loose systems. For growing RR those tend to form particle chains, the

  14. On a numerical solution of the plastic buckling problem of structures

    NASA Technical Reports Server (NTRS)

    Gupta, K. K.

    1978-01-01

    An automated digital computer procedure is presented for the accurate and efficient solution of the plastic buckling problem of structures. This is achieved by a Sturm sequence method employing a bisection strategy, which eliminates the need for having to solve the buckling eigenvalue problem at each incremental (decremental) loading stage that is associated with the usual solution techniques. The plastic buckling mode shape is determined by a simple inverse iteration process, once the buckling load has been established. Numerical results are presented for plate problems with various edge conditions. The resulting computer program written in FORTRAN V for the JPL UNIVAC 1108 machine proves to be most economical in comparison with other existing methods of such analysis.

  15. On the solution of elastic-plastic static and dynamic postbuckling collapse of general structure

    NASA Technical Reports Server (NTRS)

    Padovan, J.; Tovichakchaikul, S.

    1983-01-01

    Many investigations have considered structural collapse from strictly the transient point of view. While such an approach is ideally correct, certain difficulties have to be overcome in its implementation. The present investigation is concerned with the development of self-adaptive algorithms which make it possible to conduct the analysis of both static elastic and elastic-plastic postbuckling, as well as static loading to the onset of buckling followed by subsequent dynamic postbuckling. The approach employed to solve the static portion of loading is to extend the constrained Incremental Newton-Raphson (INR) algorithm by incorporating elastic-plastic constitutive characterizations. Large deformation moderate strain theory is adopted to establish the overall strategy. Attention is given to governing field equations, aspects of algorithmic development, and numerical experiments conducted to illustrate the efficiency and stability of the developed schemes.

  16. Plasticity in protein-peptide recognition: crystal structures of two different peptides bound to concanavalin A.

    PubMed Central

    Jain, D; Kaur, K J; Salunke, D M

    2001-01-01

    The structures of concanavalin A (ConA) in complex with two carbohydrate-mimicking peptides, 10-mer (MYWYPYASGS) and 15-mer (RVWYPYGSYLTASGS) have been determined at 2.75 A resolution. In both crystal structures four independent peptide molecules bind to each of the crystallographically independent subunits of ConA tetramer. The peptides exhibit small but significant variability in conformations and interactions while binding to ConA. The crystal structure of another similar peptide, 12-mer (DVFYPYPYASGS), in complex with ConA has been determined (Jain, D., K. J. Kaur, B. Sundaravadivel, and D. M. Salunke. 2000. Structural and functional consequences of peptide-carbohydrate mimicry. J. Biol. Chem. 275:16098-16102). Comparison of the three complexes shows that the peptides bind to ConA at a common binding site, using different contacting residues and interactions depending on their sequence and the local environment at the binding site. The binding is also optimized by corresponding plasticity of the peptide binding site on ConA. The diversity in conformation and interactions observed here are in agreement with the structural leeway concerning plasticity of specific molecular recognition in biological processes. The adaptability of peptide-ConA interactions may also be correlated with the carbohydrate-mimicking property of these peptides. PMID:11371463

  17. Transition of Temporal Scaling Behavior in Percolation Assisted Shear-branching Structure during Plastic Deformation

    NASA Astrophysics Data System (ADS)

    Ren, Jingli; Chen, Cun; Wang, Gang; Liaw, Peter K.

    2017-03-01

    This paper explores the temporal scaling behavior induced shear-branching structure in response to variant temperatures and strain rates during plastic deformation of Zr-based bulk metallic glass (BMG). The data analysis based on the compression tests suggests that there are two states of shear-branching structures: the fractal structure with a long-range order at an intermediate temperature of 223 K and a larger strain rate of 2.5 × 10‑2 s‑1 the disordered structure dominated at other temperature and strain rate. It can be deduced from the percolation theory that the compressive ductility, ec, can reach the maximum value at the intermediate temperature. Furthermore, a dynamical model involving temperature is given for depicting the shear-sliding process, reflecting the plastic deformation has fractal structure at the temperature of 223 K and strain rate of 2.5 × 10‑2 s‑1.

  18. Transition of Temporal Scaling Behavior in Percolation Assisted Shear-branching Structure during Plastic Deformation

    PubMed Central

    Ren, Jingli; Chen, Cun; Wang, Gang; Liaw, Peter K.

    2017-01-01

    This paper explores the temporal scaling behavior induced shear-branching structure in response to variant temperatures and strain rates during plastic deformation of Zr-based bulk metallic glass (BMG). The data analysis based on the compression tests suggests that there are two states of shear-branching structures: the fractal structure with a long-range order at an intermediate temperature of 223 K and a larger strain rate of 2.5 × 10−2 s−1; the disordered structure dominated at other temperature and strain rate. It can be deduced from the percolation theory that the compressive ductility, ec, can reach the maximum value at the intermediate temperature. Furthermore, a dynamical model involving temperature is given for depicting the shear-sliding process, reflecting the plastic deformation has fractal structure at the temperature of 223 K and strain rate of 2.5 × 10−2 s−1. PMID:28327562

  19. Structural plasticity: how intermetallics deform themselves in response to chemical pressure, and the complex structures that result.

    PubMed

    Berns, Veronica M; Fredrickson, Daniel C

    2014-10-06

    Interfaces between periodic domains play a crucial role in the properties of metallic materials, as is vividly illustrated by the way in which the familiar malleability of many metals arises from the formation and migration of dislocations. In complex intermetallics, such interfaces can occur as an integral part of the ground-state crystal structure, rather than as defects, resulting in such marvels as the NaCd2 structure (whose giant cubic unit cell contains more than 1000 atoms). However, the sources of the periodic interfaces in intermetallics remain mysterious, unlike the dislocations in simple metals, which can be associated with the exertion of physical stresses. In this Article, we propose and explore the concept of structural plasticity, the hypothesis that interfaces in complex intermetallic structures similarly result from stresses, but ones that are inherent in a defect-free parent structure, rather than being externally applied. Using DFT-chemical pressure analysis, we show how the complex structures of Ca2Ag7 (Yb2Ag7 type), Ca14Cd51 (Gd14Ag51 type), and the 1/1 Tsai-type quasicrystal approximant CaCd6 (YCd6 type) can all be traced to large negative pressures around the Ca atoms of a common progenitor structure, the CaCu5 type with its simple hexagonal 6-atom unit cell. Two structural paths are found by which the compounds provide relief to the Ca atoms' negative pressures: a Ca-rich pathway, where lower coordination numbers are achieved through defects eliminating transition metal (TM) atoms from the structure; and a TM-rich path, along which the addition of spacer Cd atoms provides the Ca coordination environments greater independence from each other as they contract. The common origins of these structures in the presence of stresses within a single parent structure highlights the diverse paths by which intermetallics can cope with competing interactions, and the role that structural plasticity may play in navigating this diversity.

  20. Annual reversible plasticity of feeding structures: cyclical changes of jaw allometry in a sea urchin.

    PubMed

    Ebert, Thomas A; Hernández, José Carlos; Clemente, Sabrina

    2014-03-22

    A wide variety of organisms show morphologically plastic responses to environmental stressors but in general these changes are not reversible. Though less common, reversible morphological structures are shown by a range of species in response to changes in predators, competitors or food. Theoretical analysis indicates that reversible plasticity increases fitness if organisms are long-lived relative to the frequency of changes in the stressor and morphological changes are rapid. Many sea urchin species show differences in the sizes of jaws (demi-pyramids) of the feeding apparatus, Aristotle's lantern, relative to overall body size, and these differences have been correlated with available food. The question addressed here is whether reversible changes of relative jaw size occur in the field as available food changes with season. Monthly samples of the North American Pacific coast sea urchin Strongylocentrotus purpuratus were collected from Gregory Point on the Oregon (USA) coast and showed an annual cycle of relative jaw size together with a linear trend from 2007 to 2009. Strongylocentrotus purpuratus is a long-lived species and under field conditions individuals experience multiple episodes of changes in food resources both seasonally and from year to year. Their rapid and reversible jaw plasticity fits well with theoretical expectations.

  1. Translational control of auditory imprinting and structural plasticity by eIF2α

    PubMed Central

    Batista, Gervasio; Johnson, Jennifer Leigh; Dominguez, Elena; Costa-Mattioli, Mauro; Pena, Jose L

    2016-01-01

    The formation of imprinted memories during a critical period is crucial for vital behaviors, including filial attachment. Yet, little is known about the underlying molecular mechanisms. Using a combination of behavior, pharmacology, in vivo surface sensing of translation (SUnSET) and DiOlistic labeling we found that, translational control by the eukaryotic translation initiation factor 2 alpha (eIF2α) bidirectionally regulates auditory but not visual imprinting and related changes in structural plasticity in chickens. Increasing phosphorylation of eIF2α (p-eIF2α) reduces translation rates and spine plasticity, and selectively impairs auditory imprinting. By contrast, inhibition of an eIF2α kinase or blocking the translational program controlled by p-eIF2α enhances auditory imprinting. Importantly, these manipulations are able to reopen the critical period. Thus, we have identified a translational control mechanism that selectively underlies auditory imprinting. Restoring translational control of eIF2α holds the promise to rejuvenate adult brain plasticity and restore learning and memory in a variety of cognitive disorders. DOI: http://dx.doi.org/10.7554/eLife.17197.001 PMID:28009255

  2. Structuring policy problems for plastics, the environment and human health: reflections from the UK.

    PubMed

    Shaxson, Louise

    2009-07-27

    How can we strengthen the science-policy interface for plastics, the environment and human health? In a complex policy area with multiple stakeholders, it is important to clarify the nature of the particular plastics-related issue before trying to understand how to reconcile the supply and demand for evidence in policy. This article proposes a simple problem typology to assess the fundamental characteristics of a policy issue and thus identify appropriate processes for science-policy interactions. This is illustrated with two case studies from one UK Government Department, showing how policy and science meet over the environmental problems of plastics waste in the marine environment and on land. A problem-structuring methodology helps us understand why some policy issues can be addressed through relatively linear flows of science from experts to policymakers but why others demand a more reflexive approach to brokering the knowledge between science and policy. Suggestions are given at the end of the article for practical actions that can be taken on both sides.

  3. Structuring policy problems for plastics, the environment and human health: reflections from the UK

    PubMed Central

    Shaxson, Louise

    2009-01-01

    How can we strengthen the science–policy interface for plastics, the environment and human health? In a complex policy area with multiple stakeholders, it is important to clarify the nature of the particular plastics-related issue before trying to understand how to reconcile the supply and demand for evidence in policy. This article proposes a simple problem typology to assess the fundamental characteristics of a policy issue and thus identify appropriate processes for science–policy interactions. This is illustrated with two case studies from one UK Government Department, showing how policy and science meet over the environmental problems of plastics waste in the marine environment and on land. A problem-structuring methodology helps us understand why some policy issues can be addressed through relatively linear flows of science from experts to policymakers but why others demand a more reflexive approach to brokering the knowledge between science and policy. Suggestions are given at the end of the article for practical actions that can be taken on both sides. PMID:19528061

  4. Molecular surface structural changes of plasticized PVC materials after plasma treatment.

    PubMed

    Zhang, Xiaoxian; Zhang, Chi; Hankett, Jeanne M; Chen, Zhan

    2013-03-26

    In this research, a variety of analytical techniques including sum frequency generation vibrational spectroscopy (SFG), coherent anti-Stokes Raman spectroscopy (CARS), and X-ray photoelectron spectroscopy (XPS) have been employed to investigate the surface and bulk structures of phthalate plasticized poly(vinyl chloride) (PVC) at the molecular level. Two types of phthalate molecules with different chain lengths, diethyl phthalate (DEP) and dibutyl phthalate (DBP), mixed with PVC in various weight ratios were examined to verify their different surface and bulk behaviors. The effects of oxygen and argon plasma treatment on PVC/DBP and PVC/DEP hybrid films were investigated on both the surface and bulk of films using SFG and CARS to evaluate the different plasticizer migration processes. Without plasma treatment, SFG results indicated that more plasticizers segregate to the surface at higher plasticizer bulk concentrations. SFG studies also demonstrated the presence of phthalates on the surface even at very low bulk concentration (5 wt %). Additionally, the results gathered from SFG, CARS, and XPS experiments suggested that the PVC/DEP system was unstable, and DEP molecules could leach out from the PVC under low vacuum after several minutes. In contrast, the PVC/DBP system was more stable; the migration process of DBP out of PVC could be effectively suppressed after oxygen plasma treatment. XPS results indicated the increase of C═O/C-O groups and decrease of C-Cl functionalities on the polymer surface after oxygen plasma treatment. The XPS results also suggested that exposure to argon plasma induced chemical bond breaking and formation of cross-linking or unsaturated groups with chain scission on the surface. Finally, our results indicate the potential risk of using DEP molecules in PVC since DEP can easily leach out from the polymeric bulk.

  5. RBM3 mediates structural plasticity and protective effects of cooling in neurodegeneration

    PubMed Central

    Peretti, Diego; Bastide, Amandine; Radford, Helois; Verity, Nicholas; Molloy, Colin; Martin, Maria Guerra; Moreno, Julie A.; Steinert, Joern R; Smith, Tim; Dinsdale, David; Willis, Anne E.; Mallucci, Giovanna R.

    2014-01-01

    In the healthy adult brain synapses are continuously remodelled through a process of elimination and formation known as structural plasticity1. Reduction in synapse number is a consistent early feature of neurodegenerative diseases2, 3, suggesting deficient compensatory mechanisms. While much is known about toxic processes leading to synaptic dysfunction and loss in these disorders2,3, how synaptic regeneration is affected is unknown. In hibernating mammals, cooling induces loss of synaptic contacts, which are reformed on rewarming, a form of structural plasticity4, 5. We have found that similar changes occur in artificially cooled laboratory rodents. Cooling and hibernation also induce a number cold-shock proteins in the brain, including the RNA binding protein, RBM36. The relationship of such proteins to structural plasticity is unknown. Here we show that synapse regeneration is impaired in mouse models of neurodegenerative disease, in association with the failure to induce RBM3. In both prion-infected and 5×FAD (Alzheimer-type) mice7, the capacity to regenerate synapses after cooling declined in parallel with the loss of induction of RBM3. Enhanced expression of RBM3 in the hippocampus prevented this deficit and restored the capacity for synapse reassembly after cooling. Further, RBM3 over-expression, achieved either by boosting endogenous levels through hypothermia prior to the loss of the RBM3 response, or by lentiviral delivery, resulted in sustained synaptic protection in 5×FAD mice and throughout the course of prion disease, preventing behavioural deficits and neuronal loss and significantly prolonging survival. In contrast, knockdown of RBM3 exacerbated synapse loss in both models and accelerated disease and prevented the neuroprotective effects of cooling. Thus, deficient synapse regeneration, mediated at least in part by failure of the RBM3 stress response, contributes to synapse loss throughout the course of neurodegenerative disease. The data support

  6. Predicting performance and plasticity in the development of respiratory structures and metabolic systems.

    PubMed

    Greenlee, Kendra J; Montooth, Kristi L; Helm, Bryan R

    2014-07-01

    The scaling laws governing metabolism suggest that we can predict metabolic rates across taxonomic scales that span large differences in mass. Yet, scaling relationships can vary with development, body region, and environment. Within species, there is variation in metabolic rate that is independent of mass and which may be explained by genetic variation, the environment or their interaction (i.e., metabolic plasticity). Additionally, some structures, such as the insect tracheal respiratory system, change throughout development and in response to the environment to match the changing functional requirements of the organism. We discuss how study of the development of respiratory function meets multiple challenges set forth by the NSF Grand Challenges Workshop. Development of the structure and function of respiratory and metabolic systems (1) is inherently stable and yet can respond dynamically to change, (2) is plastic and exhibits sensitivity to environments, and (3) can be examined across multiple scales in time and space. Predicting respiratory performance and plasticity requires quantitative models that integrate information across scales of function from the expression of metabolic genes and mitochondrial biogenesis to the building of respiratory structures. We present insect models where data are available on the development of the tracheal respiratory system and of metabolic physiology and suggest what is needed to develop predictive models. Incorporating quantitative genetic data will enable mapping of genetic and genetic-by-environment variation onto phenotypes, which is necessary to understand the evolution of respiratory and metabolic systems and their ability to enable respiratory homeostasis as organisms walk the tightrope between stability and change.

  7. Predicting Performance and Plasticity in the Development of Respiratory Structures and Metabolic Systems

    PubMed Central

    Montooth, Kristi L.; Helm, Bryan R.

    2014-01-01

    The scaling laws governing metabolism suggest that we can predict metabolic rates across taxonomic scales that span large differences in mass. Yet, scaling relationships can vary with development, body region, and environment. Within species, there is variation in metabolic rate that is independent of mass and which may be explained by genetic variation, the environment or their interaction (i.e., metabolic plasticity). Additionally, some structures, such as the insect tracheal respiratory system, change throughout development and in response to the environment to match the changing functional requirements of the organism. We discuss how study of the development of respiratory function meets multiple challenges set forth by the NSF Grand Challenges Workshop. Development of the structure and function of respiratory and metabolic systems (1) is inherently stable and yet can respond dynamically to change, (2) is plastic and exhibits sensitivity to environments, and (3) can be examined across multiple scales in time and space. Predicting respiratory performance and plasticity requires quantitative models that integrate information across scales of function from the expression of metabolic genes and mitochondrial biogenesis to the building of respiratory structures. We present insect models where data are available on the development of the tracheal respiratory system and of metabolic physiology and suggest what is needed to develop predictive models. Incorporating quantitative genetic data will enable mapping of genetic and genetic-by-environment variation onto phenotypes, which is necessary to understand the evolution of respiratory and metabolic systems and their ability to enable respiratory homeostasis as organisms walk the tightrope between stability and change. PMID:24812329

  8. Structural and mechanical properties of nanocrystalline titanium processed by severe plastic deformation

    SciTech Connect

    Popov, A.A.; Pyshmintsev, I.Y.; Demakov, S.L.; Illarionov, A.G.; Lowe, T.C.; Sergeyeva, A.V.; Valiev, R.Z.

    1997-10-01

    Recent investigations have demonstrated that materials with ultrafine grain (UFG) structure (nano- and submicron crystalline) can be processed by severe plastic deformation. One advantage of this method is that it can be applied to both pure metals and alloys. Moreover, it produces samples that have no residual porosity so that meaningful measurements of the physical and mechanical properties are possible. Investigations of ultrafine grain copper and aluminum alloys have revealed a number of specific features of their mechanical behavior, namely extremely high hardness and strength, the absence of strain hardening, and deviation form the Hall-Petch relationship. In this work the authors investigate the mechanical properties and thermal stability of UFG titanium.

  9. The calcium sensor Copine-6 regulates spine structural plasticity and learning and memory

    PubMed Central

    Reinhard, Judith R.; Kriz, Alexander; Galic, Milos; Angliker, Nico; Rajalu, Mathieu; Vogt, Kaspar E.; Ruegg, Markus A.

    2016-01-01

    Hippocampal long-term potentiation (LTP) represents the cellular response of excitatory synapses to specific patterns of high neuronal activity and is required for learning and memory. Here we identify a mechanism that requires the calcium-binding protein Copine-6 to translate the initial calcium signals into changes in spine structure. We show that Copine-6 is recruited from the cytosol of dendrites to postsynaptic spine membranes by calcium transients that precede LTP. Cpne6 knockout mice are deficient in hippocampal LTP, learning and memory. Hippocampal neurons from Cpne6 knockouts lack spine structural plasticity as do wild-type neurons that express a Copine-6 calcium mutant. The function of Copine-6 is based on its binding, activating and recruiting the Rho GTPase Rac1 to cell membranes. Consistent with this function, the LTP deficit of Cpne6 knockout mice is rescued by the actin stabilizer jasplakinolide. These data show that Copine-6 links activity-triggered calcium signals to spine structural plasticity necessary for learning and memory. PMID:27194588

  10. Analysis of a ceramic filled bio-plastic composite sandwich structure

    SciTech Connect

    Habib Ullah, M.; Islam, M. T.

    2013-11-25

    Design and analysis of a ceramic-filled bio-plastic composite sandwich structure is presented. This proposed high-dielectric structure is used as a substrate for patch antennas. A meandered-strip line-fed fractal-shape patch antenna is designed and fabricated on a copper-laminated sandwich-structured substrate. Measurement results of this antenna show 44% and 20% of bandwidths with maximum gains of 3.45 dBi and 5.87 dBi for the lower and upper bands, respectively. The half-power beam widths of 104° and 78° have been observed from the measured radiation pattern at the two resonance frequencies 0.9 GHz and 2.5 GHz.

  11. Dendritic structural plasticity in the basolateral amygdala after fear conditioning and its extinction in mice.

    PubMed

    Heinrichs, Stephen C; Leite-Morris, Kimberly A; Guy, Marsha D; Goldberg, Lisa R; Young, Angela J; Kaplan, Gary B

    2013-07-01

    Previous research suggests that morphology and arborization of dendritic spines change as a result of fear conditioning in cortical and subcortical brain regions. This study uniquely aims to delineate these structural changes in the basolateral amygdala (BLA) after both fear conditioning and fear extinction. C57BL/6 mice acquired robust conditioned fear responses (70-80% cued freezing behavior) after six pairings with a tone cue associated with footshock in comparison to unshocked controls. During fear acquisition, freezing behavior was significantly affected by both shock exposure and trial number. For fear extinction, mice were exposed to the conditioned stimulus tone in the absence of shock administration and behavioral responses significantly varied by shock treatment. In the retention tests over 3 weeks, the percentage time spent freezing varied with the factor of extinction training. In all treatment groups, alterations in dendritic plasticity were analyzed using Golgi-Cox staining of dendrites in the BLA. Spine density differed between the fear conditioned group and both the fear extinction and control groups on third order dendrites. Spine density was significantly increased in the fear conditioned group compared to the fear extinction group and controls. Similarly in Sholl analyses, fear conditioning significantly increased BLA spine numbers and dendritic intersections while subsequent extinction training reversed these effects. In summary, fear extinction produced enduring behavioral plasticity that is associated with a reversal of alterations in BLA dendritic plasticity produced by fear conditioning. These neuroplasticity findings can inform our understanding of structural mechanisms underlying stress-related pathology can inform treatment research into these disorders.

  12. The evolution of phenotypic plasticity in spatially structured environments: implications of intraspecific competition, plasticity costs and environmental characteristics.

    PubMed

    Ernande, B; Dieckmann, U

    2004-05-01

    We model the evolution of reaction norms focusing on three aspects: frequency-dependent selection arising from resource competition, maintenance and production costs of phenotypic plasticity, and three characteristics of environmental heterogeneity (frequency of environments, their intrinsic carrying capacity and the sensitivity to phenotypic maladaptation in these environments). We show that (i) reaction norms evolve so as to trade adaptation for acquiring resources against cost avoidance; (ii) maintenance costs cause reaction norms to better adapt to frequent rather than to infrequent environments, whereas production costs do not; and (iii) evolved reaction norms confer better adaptation to environments with low rather than with high intrinsic carrying capacity. The two previous findings contradict earlier theoretical results and originate from two previously unexplored features that are included in our model. First, production costs of phenotypic plasticity are only incurred when a given phenotype is actually produced. Therefore, they are proportional to the frequency of environments, and these frequencies thus affect the selection pressure to avoid costs just as much as the selection pressure to improve adaptation. This prevents the frequency of environments from affecting the evolving reaction norm. Secondly, our model describes the evolution of plasticity for a phenotype determining an individual's capability to acquire resources, and thus its realized carrying capacity. When individuals are distributed randomly across environments, they cannot avoid experiencing environments with intrinsically low carrying capacity. As selection pressures arising from the need to improve adaptation are stronger under such extreme conditions than under mild ones, better adaptation to environments with low rather than with high intrinsic carrying capacity results.

  13. Lim kinase, a bi-functional effector in injury-induced structural plasticity of synapses

    PubMed Central

    Wang, Weiwei; Townes-Anderson, Ellen

    2016-01-01

    The structural plasticity of synaptic terminals contributes to normal nervous system function but also to neural degeneration, in the form of terminal retraction, and regeneration, due to process growth. Synaptic morphological change is mediated through the actin cytoskeleton, which is enriched in axonal and dendritic terminals. Whereas the three RhoGTPases, RhoA, Cdc42 and Rac, function as upstream signaling nodes sensitive to extracellular stimuli, LIMK-cofilin activity serves as a common downstream effector to up-regulate actin turnover, which is necessary for both polymerization and depolymerization. The dual effects of LIMK activity make LIMK a potential target of therapeutic intervention for injury-induced synaptic plasticity, as LIMK inhibition can stabilize actin cytoskeleton and preserve existing structure. This therapeutic benefit of LIMK inhibition has been demonstrated in animal models of injury-induced axon retraction and neuritic sprouting by rod photoreceptors. A better understanding of the regulation of LIMK-cofilin activity and the interaction with the microtubular cytoskeleton may open new ways to promote synaptic regeneration that can benefit neuronal degenerative disease. PMID:27630670

  14. Structural recovery in plastic crystals by time-resolved non-linear dielectric spectroscopy.

    PubMed

    Riechers, Birte; Samwer, Konrad; Richert, Ranko

    2015-04-21

    The dielectric relaxation of several different plastic crystals has been examined at high amplitudes of the ac electric fields, with the aim of exploring possible differences with respect to supercooled liquids. In all cases, the steady state high field loss spectrum appears to be widened, compared with its low field limit counterpart, whereas peak position and peak amplitude remain almost unchanged. This field induced change in the loss profile is explained on the basis of two distinct effects: an increased relaxation time due to reduced configurational entropy at high fields which affects the low frequency part of the spectrum, and accelerated dynamics at frequencies above the loss peak position resulting from the added energy that the sample absorbs from the external electric field. From the time-resolved assessment of the field induced changes in fictive temperatures at relatively high frequencies, we find that this structural recovery is slaved to the average rather than mode specific structural relaxation time. In other words, the very fast relaxation modes in the plastic crystal cannot adjust their fictive temperatures faster than the slower modes, the equivalent of time aging-time superposition. As a result, an explanation for this single fictive temperature must be consistent with positional order, i.e., translational motion or local density fluctuations do not govern the persistence time of local time constants.

  15. Causal measures of structure and plasticity in simulated and living neural networks.

    PubMed

    Cadotte, Alex J; DeMarse, Thomas B; He, Ping; Ding, Mingzhou

    2008-10-07

    A major goal of neuroscience is to understand the relationship between neural structures and their function. Recording of neural activity with arrays of electrodes is a primary tool employed toward this goal. However, the relationships among the neural activity recorded by these arrays are often highly complex making it problematic to accurately quantify a network's structural information and then relate that structure to its function. Current statistical methods including cross correlation and coherence have achieved only modest success in characterizing the structural connectivity. Over the last decade an alternative technique known as Granger causality is emerging within neuroscience. This technique, borrowed from the field of economics, provides a strong mathematical foundation based on linear auto-regression to detect and quantify "causal" relationships among different time series. This paper presents a combination of three Granger based analytical methods that can quickly provide a relatively complete representation of the causal structure within a neural network. These are a simple pairwise Granger causality metric, a conditional metric, and a little known computationally inexpensive subtractive conditional method. Each causal metric is first described and evaluated in a series of biologically plausible neural simulations. We then demonstrate how Granger causality can detect and quantify changes in the strength of those relationships during plasticity using 60 channel spike train data from an in vitro cortical network measured on a microelectrode array. We show that these metrics can not only detect the presence of causal relationships, they also provide crucial information about the strength and direction of that relationship, particularly when that relationship maybe changing during plasticity. Although we focus on the analysis of multichannel spike train data the metrics we describe are applicable to any stationary time series in which causal

  16. Regulation of spine and synapse formation by activity-dependent intracellular signaling pathways

    PubMed Central

    Saneyoshi, Takeo; Fortin, Dale A; Soderling, Thomas R

    2010-01-01

    Formation of the human brain during embryonic and postnatal development is an extraordinarily complex process resulting at maturity in billions of neurons with trillions of specialized connections called synapses. These synapses, composed of a varicosity or bouton from a presynaptic neuron that communicates with a dendritic spine of the postsynaptic neuron, comprise the neural network that is essential for complex behavioral phenomena and cognition. Inappropriate synapse formation or structure is thought to underlie several developmental neuropathologies. Even in the mature CNS, alterations in synapse structure and function continues to be a very dynamic process that is foundational to learning and memory as well as other adaptive abilities of the brain. This synaptic plasticity in mature neurons, which is often triggered by certain patterns of neural activity, is again multifaceted and involves post-translational modifications (e.g. phosphorylation) and subcellular relocalization or trafficking (endocytosis/exocytosis) of existing synaptic proteins, initiation of protein synthesis from existing mRNAs localized in dendrites or spines, and triggering of new gene transcription in the nucleus. These various cellular processes support varying temporal components of synaptic plasticity that begin within 1–2 min but can persist for hours to days. This review will give a critical assessment of activity-dependent molecular modulations of synapses reported over the past couple years. Owing to space limitations, it will focus on mammalian excitatory (i.e. glutamatergic) synapses and will not consider several activity-independent signaling pathways (e.g. ephrinB receptor) that also modulate spine and synapse formation [1,2]. PMID:19896363

  17. Plasticity of CYP2B Enzymes: Structural and Solution Biophysical Methods

    PubMed Central

    Wilderman, P. Ross; Halpert, James R.

    2013-01-01

    In the past three years, major advances in understanding cytochrome P450 2B (CYP2B) structure-function relationships have been made through determination of multiple ligand-bound and one ligand-free X-ray crystal structure of CYP2B4 and one ligand-bound X-ray crystal structure of CYP2B6. These structures have provided insight into the features that provide the high degree of plasticity of the enzymes. A combination of a phenylalanine cluster that allows for concerted movement of helices F through G and a conserved set of electrostatic interactions involving Arg262 facilitates movement of this region to accommodate binding of ligands of various sizes without perturbing most of the P450 fold. Integrating solution based techniques such as NMR or deuterium exchange mass spectrometry (DXMS) with computational methods including molecular docking has provided further insight into enzyme behavior upon ligand binding. In addition, extended molecular dynamics simulations have provided a link between an open and a closed conformation of ligand-free CYP2B4 found in crystal structures. Other studies revealed the utility of rational engineering in improving stability of P450s to facilitate structural studies. The solution and computational results combined with the X-ray crystal structures yield a comprehensive picture of how these enzymes adopt different conformations to bind various ligands. PMID:22208531

  18. Neuronal plasticity and antidepressant actions.

    PubMed

    Castrén, Eero; Hen, René

    2013-05-01

    Antidepressant treatments enhance plasticity and increase neurogenesis in the adult brain, but it has been unclear how these effects influence mood. We propose that, like environmental enrichment and exercise, antidepressant treatments enhance adaptability by increasing structural variability within the nervous system at many levels, from proliferating precursors to immature synaptic contacts. Conversely, sensory deprivation and chronic stress reduce this structural variability. Activity-dependent competition within the mood-related circuits, guided by rehabilitation, then selects for the survival and stabilization of those structures that best represent the internal or external milieu. Increased variability together with competition-mediated selection facilitates normal function, such as pattern separation within the dentate gyrus and other mood-related circuits, thereby enhancing adaptability toward novel experiences.

  19. Imaging ERK and PKA Activation in Single Dendritic Spines during Structural Plasticity.

    PubMed

    Tang, Shen; Yasuda, Ryohei

    2017-03-22

    Extracellular signal-regulated kinase (ERK) and protein kinase A (PKA) play important roles in LTP and spine structural plasticity. While fluorescence resonance energy transfer (FRET)-based sensors for these kinases had previously been developed, they did not provide sufficient sensitivity for imaging small neuronal compartments, such as single dendritic spines in brain slices. Here we improved the sensitivity of FRET-based kinase sensors for monitoring kinase activity under two-photon fluorescence lifetime imaging microscopy (2pFLIM). Using these improved sensors, we succeeded in imaging ERK and PKA activation in single dendritic spines during structural long-term potentiation (sLTP) in hippocampal CA1 pyramidal neurons, revealing that the activation of these kinases spreads widely with length constants of more than 10 μm. The strategy for improvement of sensors used here should be applicable for developing highly sensitive biosensors for various protein kinases. VIDEO ABSTRACT.

  20. Structural Plasticity Underpins Promiscuous Binding of the Prosurvival Protein A1

    SciTech Connect

    Smits,C.; Czabotar, P.; Hinds, M.; Day, C.

    2008-01-01

    Apoptotic pathways are regulated by protein-protein interactions. Interaction of the BH3 domains of proapoptotic Bcl-2 family proteins with the hydrophobic groove of prosurvival proteins is critical. Whereas some BH3 domains bind in a promiscuous manner, others exhibit considerable selectivity and the sequence characteristics that distinguish these activities are unclear. In this study, crystal structures of complexes between the prosurvival protein A1 and the BH3 domains from Puma, Bmf, Bak, and Bid have been solved. The structure of A1 is similar to that of other prosurvival proteins, although features, such as an acidic patch in the binding groove, may allow specific therapeutic modulation of apoptosis. Significant conformational plasticity was observed in the intermolecular interactions and these differences explain some of the variation in affinity. This study, in combination with published data, suggests that interactions between conserved residues demarcate optimal binding.

  1. Design method for distillation columns filled with metallic, ceramic, or plastic structured packings

    SciTech Connect

    Gualito, J.J.; Cerino, F.J.; Cardenas, J.C.; Rocha, J.A.

    1997-05-01

    This work is a continuation and refinement of a general model developed at the Separations Research Program at The University of Texas at Austin (SRP II model) for the prediction of the height equivalent to a theoretical plate and pressure drop for distillation columns filled with metallic structured packings. It contains three parts. In the first part, the general model is briefly described and the participating equations are summarized. In the main part, the parameters needed for applying the general model for structured packings made of ceramic and plastic are presented and discussed. In the third part, the authors try to correct the model in order to get good predictions at low and high pressures.

  2. Synaptic plasticity in a cerebellum-like structure depends on temporal order

    NASA Astrophysics Data System (ADS)

    Bell, Curtis C.; Han, Victor Z.; Sugawara, Yoshiko; Grant, Kirsty

    1997-05-01

    Cerebellum-like structures in fish appear to act as adaptive sensory processors, in which learned predictions about sensory input are generated and subtracted from actual sensory input, allowing unpredicted inputs to stand out1-3. Pairing sensory input with centrally originating predictive signals, such as corollary discharge signals linked to motor commands, results in neural responses to the predictive signals alone that are Negative images' of the previously paired sensory responses. Adding these 'negative images' to actual sensory inputs minimizes the neural response to predictable sensory features. At the cellular level, sensory input is relayed to the basal region of Purkinje-like cells, whereas predictive signals are relayed by parallel fibres to the apical dendrites of the same cells4. The generation of negative images could be explained by plasticity at parallel fibre synapses5-7. We show here that such plasticity exists in the electrosensory lobe of mormyrid electric fish and that it has the necessary properties for such a model: it is reversible, anti-hebbian (excitatory postsynaptic potentials (EPSPs) are depressed after pairing with a postsynaptic spike) and tightly dependent on the sequence of pre- and postsynaptic events, with depression occurring only if the postsynaptic spike follows EPSP onset within 60 ms.

  3. Cocaine activates Rac1 to control structural and behavioral plasticity in caudate putamen.

    PubMed

    Li, Juan; Zhang, Lei; Chen, Zhenzhong; Xie, Minjuan; Huang, Lu; Xue, Jinhua; Liu, Yutong; Liu, Nuyun; Guo, Fukun; Zheng, Yi; Kong, Jiming; Zhang, Lin; Zhang, Lu

    2015-03-01

    Repeated exposure to cocaine was previously found to cause sensitized behavioral responses and structural remodeling on medium spiny neurons of the nucleus accumbens (NAc) and caudate putamen (CPu). Rac1 has emerged as a key integrator of environmental cues that regulates dendritic cytoskeletons. In this study, we investigated the role of Rac1 in cocaine-induced dendritic and behavioral plasticity in the CPu. We found that Rac1 activation was reduced in the NAc but increased in the CPu following repeated cocaine treatment. Inhibition of Rac1 activity by a Rac1-specific inhibitor NSC23766, overexpression of a dominant negative mutant of Rac1 (T17N-Rac1) or local knockout of Rac1 attenuated the cocaine-induced increase in dendrites and spine density in the CPu, whereas overexpression of a constitutively active Rac1 exert the opposite effect. Moreover, NSC23766 reversed the increased number of asymmetric spine synapses in the CPu following chronic cocaine exposure. Downregulation of Rac1 activity likewise attenuates behavioral reward responses to cocaine exposure, with activation of Rac1 producing the opposite effect. Thus, Rac1 signaling is differentially regulated in the NAc and CPu after repeated cocaine treatment, and induction of Rac1 activation in the CPu is important for cocaine exposure-induced dendritic remodeling and behavioral plasticity.

  4. Functional and Structural Brain Plasticity Enhanced by Motor and Cognitive Rehabilitation in Multiple Sclerosis

    PubMed Central

    Prosperini, Luca; Piattella, Maria Cristina

    2015-01-01

    Rehabilitation is recognized to be important in ameliorating motor and cognitive functions, reducing disease burden, and improving quality of life in patients with multiple sclerosis (MS). In this systematic review, we summarize the existing evidences that motor and cognitive rehabilitation may enhance functional and structural brain plasticity in patients with MS, as assessed by means of the most advanced neuroimaging techniques, including diffusion tensor imaging and task-related and resting-state functional magnetic resonance imaging (MRI). In most cases, the rehabilitation program was based on computer-assisted/video game exercises performed in either an outpatient or home setting. Despite their heterogeneity, all the included studies describe changes in white matter microarchitecture, in task-related activation, and/or in functional connectivity following both task-oriented and selective training. When explored, relevant correlation between improved function and MRI-detected brain changes was often found, supporting the hypothesis that training-induced brain plasticity is specifically linked to the trained domain. Small sample sizes, lack of randomization and/or an active control group, as well as missed relationship between MRI-detected changes and clinical performance, are the major drawbacks of the selected studies. Knowledge gaps in this field of research are also discussed to provide a framework for future investigations. PMID:26064692

  5. Influence of Plastic Deformation on Martensitic Transformation During Hot Stamping of Complex Structure Auto Parts

    NASA Astrophysics Data System (ADS)

    Shen, Yuhan; Song, Yanli; Hua, Lin; Lu, Jue

    2017-02-01

    The ultra-high strength steel auto parts manufactured by hot stamping are widely applied for weight reduction and safety improvement. During the hot stamping process, hot forming and quenching are performed in one step wherein plastic deformation and phase transformation simultaneously take place and affect each other. Thereinto, the influence of deformation on martensitic transformation is of great importance. In the present paper, the influence of plastic deformation on martensitic transformation during hot stamping of complex structure auto parts was investigated. For this purpose, a B-pillar reinforced panel in B1500HS steel was manufactured by hot stamping, and the process was simulated by finite element software based on a thermo-mechanical-metallurgical coupled model. Considering various deformation degrees, the microstructures and mechanical properties at four typical locations of the hot stamped B-pillar reinforced panel were detected. The results show that the martensitic content and the microhardness increase with the increase in the deformation amount. There are two reasons causing this phenomenon: (1) the increase in mechanical driving force and (2) the increased probability of the martensitic nucleation at crystal defects. The x-ray diffraction analysis indicates the carbon enrichment in retained austenite which results from the carbon diffusion during the low-carbon martensite formation. Furthermore, the carbon content decreases with the increase in the deformation amount, because the deformation of austenite suppresses the carbon diffusion.

  6. Needle-based fluorescence endomicroscopy via structured illumination with a plastic, achromatic objective

    PubMed Central

    Kyrish, Matthew; Dobbs, Jessica; Jain, Shalini; Wang, Xiao; Yu, Dihua; Richards-Kortum, Rebecca

    2013-01-01

    Abstract. In order to diagnose cancer, a sample must be removed, prepared, and examined under a microscope, which is expensive, invasive, and time consuming. Fiber optic fluorescence endomicroscopy, where an image guide is used to obtain high-resolution images of tissue in vivo, has shown promise as an alternative to conventional biopsies. However, the resolution of standard endomicroscopy is limited by the fiber bundle sampling frequency and out-of-focus light. A system is presented which incorporates a plastic, achromatic objective to increase the sampling and which provides optical sectioning via structured illumination to reject background light. An image is relayed from the sample by a fiber bundle with the custom 2.1-mm outer diameter objective lens integrated to the distal tip. The objective is corrected for the excitation and the emission wavelengths of proflavine (452 and 515 nm). It magnifies the object onto the fiber bundle to improve the system’s lateral resolution by increasing the sampling. The plastic lenses were fabricated via single-point diamond turning and assembled using a zero alignment technique. Ex vivo images of normal and neoplastic murine mammary tissues stained with proflavine are captured. The system achieves higher contrast and resolves smaller features than standard fluorescence endomicroscopy. PMID:24002190

  7. Activity-Dependent Model for Neuronal Avalanches

    NASA Astrophysics Data System (ADS)

    de Arcangelis, L.

    Networks of living neurons represent one of the most fascinating systems of modern biology. If the physical and chemical mechanisms at the basis of the functioning of a single neuron are quite well understood, the collective behavior of a system of many neurons is an extremely intriguing subject. Crucial ingredient of this complex behavior is the plasticity property of the network, namely the capacity to adapt and evolve depending on the level of activity. This plastic ability is believed, nowadays, to be at the basis of learning and memory in real brains. This fundamental problem in neurobiology has recently shown a number of features in common to other complex systems. These features mainly concern the morphology of the network, namely the spatial organization of the established connections, and a novel kind of neuronal activity. Experimental data have, in fact, shown that electrical information propagates in a cortex slice via an avalanche mode. Both features have been found in other problems in the context of the physics of complex systems and successful models have been developed to describe their behavior. In this contribution, we apply a statistical mechanical model to describe the complex activity in a neuronal network. The network is chosen to have a number of connections in long range, as found for neurons in vitro. The model implements the main physiological properties of living neurons and is able to reproduce recent experimental results. The numerical power spectra for electrical activity reproduces also the power law behavior measured in an EEG of man resting with the eyes closed.

  8. Rule learning enhances structural plasticity of long-range axons in frontal cortex

    PubMed Central

    Johnson, Carolyn M.; Peckler, Hannah; Tai, Lung-Hao; Wilbrecht, Linda

    2016-01-01

    Rules encompass cue-action-outcome associations used to guide decisions and strategies in a specific context. Subregions of the frontal cortex including the orbitofrontal cortex (OFC) and dorsomedial prefrontal cortex (dmPFC) are implicated in rule learning, although changes in structural connectivity underlying rule learning are poorly understood. We imaged OFC axonal projections to dmPFC during training in a multiple choice foraging task and used a reinforcement learning model to quantify explore–exploit strategy use and prediction error magnitude. Here we show that rule training, but not experience of reward alone, enhances OFC bouton plasticity. Baseline bouton density and gains during training correlate with rule exploitation, while bouton loss correlates with exploration and scales with the magnitude of experienced prediction errors. We conclude that rule learning sculpts frontal cortex interconnectivity and adjusts a thermostat for the explore–exploit balance. PMID:26949122

  9. Evolution of the health of concrete structures by electrically conductive GFRP (glass fiber reinforced plastic) composites

    NASA Astrophysics Data System (ADS)

    Shin, Soon-Gi

    2002-02-01

    The function and performance of self-diagnostic composites embedded in concrete blocks and piles were investigated by bending tests and electrical resistance measurement. Carbon powder (CP) and carbon fiber (CF) were introduced into glass fiber reinforced plastic (GFRP) composites to provide electrical conductivity. The CPGFRP composite displays generally good performance in various bending tests of concrete block and piles compared to the CFGFRP composite. The electrical resistance of the CPGFRP composite increases remarkably at small strains in response to microcrack formation at about 200 μm strain, and can be used to detect smaller deformations before crack formation. The CPGFRP composite shows continuous change in resistance up to a large strain level just before the final fracture for concrete structures reinforced by steel bars. It is concluded that self-diagnostic composites can be used to predict damage and fracture in concrete blocks and piles.

  10. Structural plasticity of interneurons in the adult brain: role of PSA-NCAM and implications for psychiatric disorders.

    PubMed

    Nacher, Juan; Guirado, Ramon; Castillo-Gómez, Esther

    2013-06-01

    Neuronal structural plasticity is known to have a major role in cognitive processes and in the response of the CNS to aversive experiences. This type of plasticity involves processes ranging from neurite outgrowth/retraction or dendritic spine remodeling, to the incorporation of new neurons to the established circuitry. However, the study of how these structural changes take place has been focused mainly on excitatory neurons, while little attention has been paid to interneurons. The exploration of these plastic phenomena in interneurons is very important, not only for our knowledge of CNS physiology, but also for understanding better the etiology of different psychiatric and neurological disorders in which alterations in the structure and connectivity of inhibitory networks have been described. Here we review recent work on the structural remodeling of interneurons in the adult brain, both in basal conditions and after chronic stress or sensory deprivation. We also describe studies from our laboratory and others on the putative mediators of this interneuronal structural plasticity, focusing on the polysialylated form of the neural cell adhesion molecule (PSA-NCAM). This molecule is expressed by some interneurons in the adult CNS and, through its anti-adhesive and insulating properties, may participate in the remodeling of their structure. Finally, we review recent findings on the possible implication of PSA-NCAM on the remodeling of inhibitory neurons in certain psychiatric disorders and their treatments.

  11. A period of structural plasticity at the axon initial segment in developing visual cortex

    PubMed Central

    Gutzmann, Annika; Ergül, Nursah; Grossmann, Rebecca; Schultz, Christian; Wahle, Petra; Engelhardt, Maren

    2014-01-01

    Cortical networks are shaped by sensory experience and are most susceptible to modifications during critical periods characterized by enhanced plasticity at the structural and functional level. A system particularly well-studied in this context is the mammalian visual system. Plasticity has been documented for the somatodendritic compartment of neurons in detail. A neuronal microdomain not yet studied in this context is the axon initial segment (AIS) located at the proximal axon segment. It is a specific electrogenic axonal domain and the site of action potential (AP) generation. Recent studies showed that structure and function of the AIS can be dynamically regulated. Here we hypothesize that the AIS shows a dynamic regulation during maturation of the visual cortex. We therefore analyzed AIS length development from embryonic day (E) 12.5 to adulthood in mice. A tri-phasic time course of AIS length remodeling during development was observed. AIS first appeared at E14.5 and increased in length throughout the postnatal period to a peak between postnatal day (P) 10 to P15 (eyes open P13–14). Then, AIS length was reduced significantly around the beginning of the critical period for ocular dominance plasticity (CP, P21). Shortest AIS were observed at the peak of the CP (P28), followed by a moderate elongation toward the end of the CP (P35). To test if the dynamic maturation of the AIS is influenced by eye opening (onset of activity), animals were deprived of visual input before and during the CP. Deprivation for 1 week prior to eye opening did not affect AIS length development. However, deprivation from P0 to 28 and P14 to 28 resulted in AIS length distribution similar to the peak at P15. In other words, deprivation from birth prevents the transient shortening of the AIS and maintains an immature AIS length. These results are the first to suggest a dynamic maturation of the AIS in cortical neurons and point to novel mechanisms in the development of neuronal

  12. Structural plasticity in the language system related to increased second language proficiency.

    PubMed

    Stein, Maria; Federspiel, Andrea; Koenig, Thomas; Wirth, Miranka; Strik, Werner; Wiest, Roland; Brandeis, Daniel; Dierks, Thomas

    2012-04-01

    While functional changes linked to second language learning have been subject to extensive investigation, the issue of learning-dependent structural plasticity in the fields of bilingualism and language comprehension has so far received less notice. In the present study we used voxel-based morphometry to monitor structural changes occurring within five months of second language learning. Native English-speaking exchange students learning German in Switzerland were examined once at the beginning of their stay and once about five months later, when their German language skills had significantly increased. We show that structural changes in the left inferior frontal gyrus are correlated with the increase in second language proficiency as measured by a paper-and-pencil language test. Contrary to the increase in proficiency and grey matter, the absolute values of grey matter density and second language proficiency did not correlate (neither on first nor on second measurement). This indicates that the individual amount of learning is reflected in brain structure changes, regardless of absolute proficiency.

  13. A developmentally plastic adult mouse kidney cell line spontaneously generates multiple adult kidney structures

    SciTech Connect

    Webb, Carol F.; Ratliff, Michelle L.; Powell, Rebecca; Wirsig-Wiechmann, Celeste R.; Lakiza, Olga; Obara, Tomoko

    2015-08-07

    Despite exciting new possibilities for regenerative therapy posed by the ability to induce pluripotent stem cells, recapitulation of three-dimensional kidneys for repair or replacement has not been possible. ARID3a-deficient mouse tissues generated multipotent, developmentally plastic cells. Therefore, we assessed the adult mouse ARID3a−/− kidney cell line, KKPS5, which expresses renal progenitor surface markers as an alternative cell source for modeling kidney development. Remarkably, these cells spontaneously developed into multicellular nephron-like structures in vitro, and engrafted into immunocompromised medaka mesonephros, where they formed mouse nephron structures. These data implicate KKPS5 cells as a new model system for studying kidney development. - Highlights: • An ARID3a-deficient mouse kidney cell line expresses multiple progenitor markers. • This cell line spontaneously forms multiple nephron-like structures in vitro. • This cell line formed mouse kidney structures in immunocompromised medaka fish kidneys. • Our data identify a novel model system for studying kidney development.

  14. Plastic deformation of amorphous poly(L/DL-lactide): structure evolution and physical properties.

    PubMed

    Pluta, Miroslaw; Galeski, Andrzej

    2007-06-01

    Plastic deformation of amorphous, thermally noncrystallizable poly(L/DL-lactide) 70/30 (P(L/DL)LA) was induced by a plane-strain compression in a channel-die at different temperatures, above the glass transition (Tg) from 60 to 90 degrees C. Samples undeformed (reference) and deformed to different compression ratios, from 4.6 to 23.0, were studied by X-ray diffraction, thermally modulated differential scanning calorimetry, light microscopy, and mechanical methods-viscoelastic and tensile tests. The effects of the compression ratios and deformation temperatures on the final structure and properties of the P(L/DL)LA were evaluated. It was revealed that plastic deformation transformed an amorphous P(L/DL)LA (thermally noncrystallizable) to a crystalline fibrillar texture oriented in the flow direction. Fibrillar texture was formed in spite of the tendency of the plane-strain compression to form single-crystal-like texture. The crystallite size in the transverse direction was small, up to 90 angstroms at the highest compression ratio. No evidence of lamellar organization and features of supermolecular structure were detected by small-angle X-ray scattering and light microscopy, respectively. The oriented samples exhibited a low crystallinity degree at the level of 6-9% at the highest compression ratio. The main transformation mechanism was shear and orientation-induced crystallization. The crystalline phase was in the alpha crystallographic modification of poly(lactide) typically formed in more stereoregular poly(lactide) by thermal treatment. The glass transition increased with the increase of compression ratio reflecting the increase of orientation of the polymer chains. The tensile strength of deformed samples was improved considerably in comparison to that of the reference sample.

  15. POLYESTER GLASS PLASTICS FOR SHIPBUILDING,

    DTIC Science & Technology

    POLYESTER PLASTICS , SHIP HULLS), (*SHIP HULLS, POLYESTER PLASTICS ), GLASS TEXTILES, REINFORCING MATERIALS, SHIP STRUCTURAL COMPONENTS, COMPOSITE MATERIALS, PROCESSING, CHEMISTRY, HANDBOOKS, BINDERS, USSR

  16. Morphological alterations in the hippocampus of the Ts65Dn mouse model for Down Syndrome correlate with structural plasticity markers.

    PubMed

    Villarroya, Olga; Ballestín, Raúl; López-Hidalgo, Rosa; Mulet, Maria; Blasco-Ibáñez, José Miguel; Crespo, Carlos; Nacher, Juan; Gilabert-Juan, Javier; Varea, Emilio

    2017-04-04

    Down syndrome (DS) is the most common chromosomal aneuploidy. Although trisomy on chromosome 21 can display variable phenotypes, there is a common feature among all DS individuals: the presence of intellectual disability. This condition is partially attributed to abnormalities found in the hippocampus of individuals with DS and in the murine model for DS, Ts65Dn. To check if all hippocampal areas were equally affected in 4-5 month adult Ts65Dn mice, we analysed the morphology of dentate gyrus granule cells and cornu ammonis pyramidal neurons using Sholl method on Golgi-Cox impregnated neurons. Structural plasticity has been analysed using immunohistochemistry for plasticity molecules followed by densitometric analysis (Brain Derived Neurotrophic Factor (BDNF), Polysialylated form of the Neural Cell Adhesion Molecule (PSA-NCAM) and the Growth Associated Protein 43 (GAP43)). We observed an impairment in the dendritic arborisation of granule cells, but not in the pyramidal neurons in the Ts65Dn mice. When we analysed the expression of molecules related to structural plasticity in trisomic mouse hippocampus, we observed a reduction in the expression of BDNF and PSA-NCAM, and an increment in the expression of GAP43. These alterations were restricted to the regions related to dentate granule cells suggesting an interrelation. Therefore the impairment in dendritic arborisation and molecular plasticity is not a general feature of all Down Syndrome principal neurons. Pharmacological manipulations of the levels of plasticity molecules could provide a way to restore granule cell morphology and function.

  17. The influences of soil and nearby structures on dispersion characteristics of wave propagating along buried plastic pipes

    NASA Astrophysics Data System (ADS)

    Liu, Shuyong; Jiang, J.; Parr, Nicola

    2016-09-01

    Water loss in distribution systems is a global problem for the water industry and governments. According to the international water supply association (IWSA), as a result of leaks from distribution pipes, 20% to 30% of water is lost while in transit from treatment plants to consumers. Although governments have tried to push the water industry to reduce the water leaks, a lot of experts have pointed out that a wide use of plastic pipes instead of metal pipes in recent years has caused difficulties in the detection of leaks using current acoustic technology. Leaks from plastic pipes are much quieter than traditional metal pipes and comparing to metal pipes the plastic pipes have very different coupling characteristics with soil, water and surrounding structures, such as other pipes, road surface and building foundations. The dispersion characteristics of wave propagating along buried plastic pipes are investigated in this paper using finite element and boundary element based models. Both empty and water- filled pipes were considered. Influences from nearby pipes and building foundations were carefully studied. The results showed that soil condition and nearby structures have significant influences on the dispersion characteristics of wave propagating along buried plastic pipes.

  18. Physical exercise in overweight to obese individuals induces metabolic- and neurotrophic-related structural brain plasticity

    PubMed Central

    Mueller, Karsten; Möller, Harald E.; Horstmann, Annette; Busse, Franziska; Lepsien, Jöran; Blüher, Matthias; Stumvoll, Michael; Villringer, Arno; Pleger, Burkhard

    2015-01-01

    Previous cross-sectional studies on body-weight-related alterations in brain structure revealed profound changes in the gray matter (GM) and white matter (WM) that resemble findings obtained from individuals with advancing age. This suggests that obesity may lead to structural brain changes that are comparable with brain aging. Here, we asked whether weight-loss-dependent improved metabolic and neurotrophic functioning parallels the reversal of obesity-related alterations in brain structure. To this end we applied magnetic resonance imaging (MRI) together with voxel-based morphometry and diffusion-tensor imaging in overweight to obese individuals who participated in a fitness course with intensive physical training twice a week over a period of 3 months. After the fitness course, participants presented, with inter-individual heterogeneity, a reduced body mass index (BMI), reduced serum leptin concentrations, elevated high-density lipoprotein-cholesterol (HDL-C), and alterations of serum brain-derived neurotrophic factor (BDNF) concentrations suggesting changes of metabolic and neurotrophic function. Exercise-dependent changes in BMI and serum concentration of BDNF, leptin, and HDL-C were related to an increase in GM density in the left hippocampus, the insular cortex, and the left cerebellar lobule. We also observed exercise-dependent changes of diffusivity parameters in surrounding WM structures as well as in the corpus callosum. These findings suggest that weight-loss due to physical exercise in overweight to obese participants induces profound structural brain plasticity, not primarily of sensorimotor brain regions involved in physical exercise, but of regions previously reported to be structurally affected by an increased body weight and functionally implemented in gustation and cognitive processing. PMID:26190989

  19. Correlation between structural heterogeneity and plastic deformation for phase separating FeCu metallic glasses

    PubMed Central

    Peng, Chuan-Xiao; Song, Kai-Kai; Wang, Li; Şopu, Daniel; Pauly, Simon; Eckert, Jürgen

    2016-01-01

    Unlike crystalline metals, the plastic deformation of metallic glasses (MGs) involves a competition between disordering and structural relaxation ordering, which is not well understood, yet. Molecular dynamics (MD) simulations were performed to investigate the evolutions of strain localizations, short-range order (SRO) as well as the free volume in the glass during compressive deformation of Fe50Cu50 MGs with different degrees of phase separation. Our findings indicate that the free volume in the phase separating MGs decreases while the shear strain localizations increase with increasing degree of phase separation. Cu-centered clusters show higher potential energies and Voronoi volumes, and bear larger local shear strains. On the other hand, Fe-centered pentagon-rich clusters in Cu-rich regions seem to play an important role to resist the shear transformation. The dilatation or annihilation of Voronoi volumes is due to the competition between ordering via structural relaxation and shear stress-induced deformation. The present study could provide a better understanding of the relationship between the structural inhomogeneity and the deformation of MGs. PMID:27681052

  20. Demonstrating the Effects of Processing on the Structure and Physical Properties of Plastic Using Disposable PETE Cups

    ERIC Educational Resources Information Center

    Erk, Kendra A.; Rhein, Morgan; Krafcik, Matthew J.; Ydstie, Sophie

    2015-01-01

    An educational activity is described in which the structure and physical properties of disposable plastic cups were directly related to the method of processing. The mechanical properties of specimens cut from the walls of poly(ethylene terephthalate) (PETE) cups, oriented parallel and perpendicular to the thermoforming direction, were measured in…

  1. Learning Discloses Abnormal Structural and Functional Plasticity at Hippocampal Synapses in the APP23 Mouse Model of Alzheimer's Disease

    ERIC Educational Resources Information Center

    Middei, Silvia; Roberto, Anna; Berretta, Nicola; Panico, Maria Beatrice; Lista, Simone; Bernardi, Giorgio; Mercuri, Nicola B.; Ammassari-Teule, Martine; Nistico, Robert

    2010-01-01

    B6-Tg/Thy1APP23Sdz (APP23) mutant mice exhibit neurohistological hallmarks of Alzheimer's disease but show intact basal hippocampal neurotransmission and synaptic plasticity. Here, we examine whether spatial learning differently modifies the structural and electrophysiological properties of hippocampal synapses in APP23 and wild-type mice. While…

  2. Structural Plasticity of Malaria Dihydroorotate Dehydrogenase Allows Selective Binding of Diverse Chemical Scaffolds

    SciTech Connect

    Deng, Xiaoyi; Gujjar, Ramesh; El Mazouni, Farah; Kaminsky, Werner; Malmquist, Nicholas A.; Goldsmith, Elizabeth J.; Rathod, Pradipsinh K.; Phillips, Margaret A.

    2010-01-20

    Malaria remains a major global health burden and current drug therapies are compromised by resistance. Plasmodium falciparum dihydroorotate dehydrogenase (PfDHODH) was validated as a new drug target through the identification of potent and selective triazolopyrimidine-based DHODH inhibitors with anti-malarial activity in vivo. Here we report x-ray structure determination of PfDHODH bound to three inhibitors from this series, representing the first of the enzyme bound to malaria specific inhibitors. We demonstrate that conformational flexibility results in an unexpected binding mode identifying a new hydrophobic pocket on the enzyme. Importantly this plasticity allows PfDHODH to bind inhibitors from different chemical classes and to accommodate inhibitor modifications during lead optimization, increasing the value of PfDHODH as a drug target. A second discovery, based on small molecule crystallography, is that the triazolopyrimidines populate a resonance form that promotes charge separation. These intrinsic dipoles allow formation of energetically favorable H-bond interactions with the enzyme. The importance of delocalization to binding affinity was supported by site-directed mutagenesis and the demonstration that triazolopyrimidine analogs that lack this intrinsic dipole are inactive. Finally, the PfDHODH-triazolopyrimidine bound structures provide considerable new insight into species-selective inhibitor binding in this enzyme family. Together, these studies will directly impact efforts to exploit PfDHODH for the development of anti-malarial chemotherapy.

  3. Chronic Social Defeat Stress Modulates Dendritic Spines Structural Plasticity in Adult Mouse Frontal Association Cortex

    PubMed Central

    Shu, Yu

    2017-01-01

    Chronic stress is associated with occurrence of many mental disorders. Previous studies have shown that dendrites and spines of pyramidal neurons of the prefrontal cortex undergo drastic reorganization following chronic stress experience. So the prefrontal cortex is believed to play a key role in response of neural system to chronic stress. However, how stress induces dynamic structural changes in neural circuit of prefrontal cortex remains unknown. In the present study, we examined the effects of chronic social defeat stress on dendritic spine structural plasticity in the mouse frontal association (FrA) cortex in vivo using two-photon microscopy. We found that chronic stress altered spine dynamics in FrA and increased the connectivity in FrA neural circuits. We also found that the changes in spine dynamics in FrA are correlated with the deficit of sucrose preference in defeated mice. Our findings suggest that chronic stress experience leads to adaptive change in neural circuits that may be important for encoding stress experience related memory and anhedonia. PMID:28197343

  4. Experimental febrile seizures induce age-dependent structural plasticity and improve memory in mice.

    PubMed

    Tao, K; Ichikawa, J; Matsuki, N; Ikegaya, Y; Koyama, R

    2016-03-24

    Population-based studies have demonstrated that children with a history of febrile seizure (FS) perform better than age-matched controls at hippocampus-dependent memory tasks. Here, we report that FSs induce two distinct structural reorganizations in the hippocampus and bidirectionally modify future learning abilities in an age-dependent manner. Compared with age-matched controls, adult mice that had experienced experimental FSs induced by hyperthermia (HT) on postnatal day 14 (P14-HT) performed better in a cognitive task that requires dentate granule cells (DGCs). The enhanced memory performance correlated with an FS-induced persistent increase in the density of large mossy fiber terminals (LMTs) of the DGCs. The memory enhancement was not observed in mice that had experienced HT-induced seizures at P11 which exhibited abnormally located DGCs in addition to the increased LMT density. The ectopic DGCs of the P11-HT mice were abolished by the diuretic bumetanide, and this pharmacological treatment unveiled the masked memory enhancement. Thus, this work provides a novel basis for age-dependent structural plasticity in which FSs influence future brain function.

  5. Spatial and seasonal variation in diversity and structure of microbial biofilms on marine plastics in Northern European waters.

    PubMed

    Oberbeckmann, Sonja; Loeder, Martin G J; Gerdts, Gunnar; Osborn, A Mark

    2014-11-01

    Plastic pollution is now recognised as a major threat to marine environments and marine biota. Recent research highlights that diverse microbial species are found to colonise plastic surfaces (the plastisphere) within marine waters. Here, we investigate how the structure and diversity of marine plastisphere microbial community vary with respect to season, location and plastic substrate type. We performed a 6-week exposure experiment with polyethylene terephthalate (PET) bottles in the North Sea (UK) as well as sea surface sampling of plastic polymers in Northern European waters. Scanning electron microscopy revealed diverse plastisphere communities comprising prokaryotic and eukaryotic microorganisms. Denaturing gradient gel electrophoresis (DGGE) and sequencing analysis revealed that plastisphere microbial communities on PET fragments varied both with season and location and comprised of bacteria belonging to Bacteroidetes, Proteobacteria, Cyanobacteria and members of the eukaryotes Bacillariophyceae and Phaeophyceae. Polymers sampled from the sea surface mainly comprised polyethylene, polystyrene and polypropylene particles. Variation within plastisphere communities on different polymer types was observed, but communities were primarily dominated by Cyanobacteria. This research reveals that the composition of plastisphere microbial communities in marine waters varies with season, geographical location and plastic substrate type.

  6. A plastic-composite-plastic structure high performance flexible energy harvester based on PIN-PMN-PT single crystal/epoxy 2-2 composite

    NASA Astrophysics Data System (ADS)

    Zeng, Zhou; Gai, Linlin; Wang, Xian; Lin, Di; Wang, Sheng; Luo, Haosu; Wang, Dong

    2017-03-01

    We present a high performance flexible piezoelectric energy harvester constituted by a Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 (PIN-PMN-PT) single crystal/epoxy 2-2 composite flake, a polyethylene terephthalate (PET) substrate, and a PET cover, which is capable of harvesting energy from biomechanical movements. Electrical properties of the device under different epoxy volume fractions, load resistances, and strains are studied systematically. Both theoretical and experimental results show that the plastic-composite-plastic structure contributes to the flexibility of the device, and a high performance bulk PIN-PMN-PT single crystal (a thickness of 50 μm) results in its high electrical output. At a low excitation frequency of 4.2 Hz, the optimal flexible energy harvester (with ve = 21%) can generate a peak voltage of 12.9 V and a maximum power density of 0.28 mW/cm3 under a bending radius of 10.5 mm, and maintain its performance after 40 000 bending-unbending cycles. High flexibility and excellent electrical output at low operational frequency demonstrate the promise of the device in biomechanical motion energy harvesting for wireless and portable low-power electronics.

  7. REVERSING CYCLIC ELASTO-PLASTIC DEMANDS ON STRUCTURES DURING STRONG MOTION EARTHQUAKE EXCITATION.

    USGS Publications Warehouse

    Perez, V.; Brady, A.G.; Safak, E.

    1986-01-01

    Using the horizontal components from El Centro 1940, Taft 1952, and 4 accelerograms from the San Fernando earthquake of 2/9/71, the time history of the elasto-plastic displacement response was calculated for oscillators having periods within the range of 1 to 6 s and ductility factors within the range of 3 to 6. The Nth largest peak of the elasto-plastic response (N equals 2,4,8,16), when expressed as a percentage of maximum response (that is, N equals 1), is fairly independent of period within our period range. When considering only plastic peaks occurring, sometimes in a one-directional group of peaks, in the reverse direction from the preceding plastic peak, the amplitude of the Nth reversing plastic peak is similar to the Nth elastic peak, regardless of the ductility factor.

  8. Histone methyltransferase Ash1L mediates activity-dependent repression of neurexin-1α

    PubMed Central

    Zhu, Τao; Liang, Chen; Li, Dongdong; Tian, Miaomiao; Liu, Sanxiong; Gao, Guanjun; Guan, Ji-Song

    2016-01-01

    Activity-dependent transcription is critical for the regulation of long-term synaptic plasticity and plastic rewiring in the brain. Here, we report that the transcription of neurexin1α (nrxn1α), a presynaptic adhesion molecule for synaptic formation, is regulated by transient neuronal activation. We showed that 10 minutes of firing at 50 Hz in neurons repressed the expression of nrxn1α for 24 hours in a primary cortical neuron culture through a transcriptional repression mechanism. By performing a screening assay using a synthetic zinc finger protein (ZFP) to pull down the proteins enriched near the nrxn1α promoter region in vivo, we identified that Ash1L, a histone methyltransferase, is enriched in the nrxn1α promoter. Neuronal activity triggered binding of Ash1L to the promoter and enriched the histone marker H3K36me2 at the nrxn1α promoter region. Knockout of Ash1L in mice completely abolished the activity-dependent repression of nrxn1α. Taken together, our results reveal that a novel process of activity-dependent transcriptional repression exists in neurons and that Ash1L mediates the long-term repression of nrxn1α, thus implicating an important role for epigenetic modification in brain functioning. PMID:27229316

  9. Immunocytochemical evidence of plasticity in the nervous structures of the rat lower lip.

    PubMed

    Verzé, L; Paraninfo, A; Ramieri, G; Viglietti-Panzica, C; Panzica, G C

    1999-08-01

    In this immunocytochemical study we investigated the distribution of nervous structures in the lower lip of adult rats. The region is characterized by a rich cutaneous and mucosal sensory innervation originating from terminal branches of the trigeminal system. Lower lip innervation was investigated by detection of the general neuronal marker protein gene product 9.5 (PGP 9.5) and the growth-associated protein 43 (GAP-43), a neurochemical marker of neuronal plasticity. The entire neural network of both cutaneous and mucosal aspects was stained by the antibody to PGP 9.5. In particular, nerve fibers were observed in the submucosal and the subepithelial plexuses. Thin immunoreactive fibers were observed within the epithelial layers ending as free fibers or as fibers associated with immunopositive Merkel cells. Well-identified anatomical structures receiving sensory or autonomic innervation were also surrounded by PGP 9.5-ir nerve fibers, in particular, hair follicles, vibrissae, glands, and blood vessels. GAP-43-immunostained nerve fibers were observed in all these structures; however, they were generally less numerous than the PGP 9.5-immunoreactive elements. An equal amount of PGP 9.5 and GAP-43 immunoreactivity occurred, in contrast, in the subepidermal and the submucosal plexuses, or in the epidermis and the mucosal epithelium. The present results show that GAP-43 is normally expressed in the mature trigeminal sensory system of the rat. Skin and oral mucosa are characterized by continuous remodeling that may also involve the sensory nervous apparatus. Continuous neural remodeling, regeneration and sprouting may be the reason for the observed expression of GAP-43.

  10. Orofacial Neuropathic Pain Leads to a Hyporesponsive Barrel Cortex with Enhanced Structural Synaptic Plasticity

    PubMed Central

    Thibault, Karine; Rivière, Sébastien; Lenkei, Zsolt

    2016-01-01

    Chronic pain is a long-lasting debilitating condition that is particularly difficult to treat due to the lack of identified underlying mechanisms. Although several key contributing processes have been described at the level of the spinal cord, very few studies have investigated the supraspinal mechanisms underlying chronic pain. Using a combination of approaches (cortical intrinsic imaging, immunohistochemical and behavioural analysis), our study aimed to decipher the nature of functional and structural changes in a mouse model of orofacial neuropathic pain, focusing on cortical areas involved in various pain components. Our results show that chronic neuropathic orofacial pain is associated with decreased haemodynamic responsiveness to whisker stimulation in the barrel field cortex. This reduced functional activation is likely due to the increased basal neuronal activity (measured indirectly using cFos and phospho-ERK immunoreactivity) observed in several cortical areas, including the contralateral barrel field, motor and cingulate cortices. In the same animals, immunohistochemical analysis of markers for active pre- or postsynaptic elements (Piccolo and phospho-Cofilin, respectively) revealed an increased immunofluorescence in deep cortical layers of the contralateral barrel field, motor and cingulate cortices. These results suggest that long-lasting orofacial neuropathic pain is associated with exacerbated neuronal activity and synaptic plasticity at the cortical level. PMID:27548330

  11. Circadian and homeostatic regulation of structural synaptic plasticity in hypocretin neurons.

    PubMed

    Appelbaum, Lior; Wang, Gordon; Yokogawa, Tohei; Skariah, Gemini M; Smith, Stephen J; Mourrain, Philippe; Mignot, Emmanuel

    2010-10-06

    Neurons exhibit rhythmic activity that ultimately affects behavior such as sleep. In living zebrafish larvae, we used time-lapse two-photon imaging of the presynaptic marker synaptophysin in hypocretin/orexin (HCRT) neurons to determine the dynamics of synaptic modifications during the day and night. We observed circadian rhythmicity in synapse number in HCRT axons. This rhythm is regulated primarily by the circadian clock but is also affected by sleep deprivation. Furthermore, NPTX2, a protein implicated in AMPA receptor clustering, modulates circadian synaptic changes. In zebrafish, nptx2b is a rhythmic gene that is mostly expressed in hypothalamic and pineal gland cells. Arrhythmic transgenic nptx2b overexpression (hcrt:NPTX2b) increases synapse number and abolishes rhythmicity in HCRT axons. Finally, hcrt:NPTX2b fish are resistant to the sleep-promoting effects of melatonin. This behavioral effect is consistent with NPTX2b-mediated increased activity of HCRT circuitry. These data provide real-time in vivo evidence of circadian and homeostatic regulation of structural synaptic plasticity.

  12. Parental influence on begging call structure in zebra finches (Taeniopygia guttata): evidence of early vocal plasticity

    PubMed Central

    Villain, Avelyne S.; Boucaud, Ingrid C. A.; Bouchut, Colette; Vignal, Clémentine

    2015-01-01

    Begging calls are signals of need used by young birds to elicit care from adults. Different theoretical frameworks have been proposed to understand this parent–offspring communication. But relationships between parental response and begging intensity, or between begging characteristics and proxies of a young’s need remain puzzling. Few studies have considered the adjustment of nestling begging features to previous experience as a possible explanation of these discrepancies. In this study, we tested the effect of a heterospecific rearing environment on individual developmental trajectories of the acoustic structure of nestling begging calls. Fifty-two zebra finch chicks were fostered either to Bengalese finch or to zebra finch parents, and begging calls were recorded at several stages of nestling development. Acoustic analyses revealed that the development of the spectral features of the begging calls differed between experimental conditions: chicks reared by Bengalese finches produced higher pitched and less broadband begging calls than chicks reared by conspecific parents. Differences were stronger in males than females and were not explained by differences in growth rate. We conclude that nestling begging calls can be plastic in response to social interactions with parents. PMID:26716009

  13. Experience-dependent plasticity in white matter microstructure: reasoning training alters structural connectivity.

    PubMed

    Mackey, Allyson P; Whitaker, Kirstie J; Bunge, Silvia A

    2012-01-01

    Diffusion tensor imaging (DTI) techniques have made it possible to investigate white matter plasticity in humans. Changes in DTI measures, principally increases in fractional anisotropy (FA), have been observed following training programs as diverse as juggling, meditation, and working memory. Here, we sought to test whether three months of reasoning training could alter white matter microstructure. We recruited participants (n = 23) who were enrolled in a course to prepare for the Law School Admission Test (LSAT), a test that places strong demands on reasoning skills, as well as age- and IQ-matched controls planning to take the LSAT in the future (n = 22). DTI data were collected at two scan sessions scheduled three months apart. In trained participants but not controls, we observed decreases in radial diffusivity (RD) in white matter connecting frontal cortices, and in mean diffusivity (MD) within frontal and parietal lobe white matter. Further, participants exhibiting larger gains on the LSAT exhibited greater decreases in MD in the right internal capsule. In summary, reasoning training altered multiple measures of white matter structure in young adults. While the cellular underpinnings are unknown, these results provide evidence of experience-dependent white matter changes that may not be limited to myelination.

  14. The Formation of Multi-synaptic Connections by the Interaction of Synaptic and Structural Plasticity and Their Functional Consequences

    PubMed Central

    Fauth, Michael; Wörgötter, Florentin; Tetzlaff, Christian

    2015-01-01

    Cortical connectivity emerges from the permanent interaction between neuronal activity and synaptic as well as structural plasticity. An important experimentally observed feature of this connectivity is the distribution of the number of synapses from one neuron to another, which has been measured in several cortical layers. All of these distributions are bimodal with one peak at zero and a second one at a small number (3–8) of synapses. In this study, using a probabilistic model of structural plasticity, which depends on the synaptic weights, we explore how these distributions can emerge and which functional consequences they have. We find that bimodal distributions arise generically from the interaction of structural plasticity with synaptic plasticity rules that fulfill the following biological realistic constraints: First, the synaptic weights have to grow with the postsynaptic activity. Second, this growth curve and/or the input-output relation of the postsynaptic neuron have to change sub-linearly (negative curvature). As most neurons show such input-output-relations, these constraints can be fulfilled by many biological reasonable systems. Given such a system, we show that the different activities, which can explain the layer-specific distributions, correspond to experimentally observed activities. Considering these activities as working point of the system and varying the pre- or postsynaptic stimulation reveals a hysteresis in the number of synapses. As a consequence of this, the connectivity between two neurons can be controlled by activity but is also safeguarded against overly fast changes. These results indicate that the complex dynamics between activity and plasticity will, already between a pair of neurons, induce a variety of possible stable synaptic distributions, which could support memory mechanisms. PMID:25590330

  15. Interactions between mitochondria and the transcription factor myocyte enhancer factor 2 (MEF2) regulate neuronal structural and functional plasticity and metaplasticity

    PubMed Central

    Brusco, Janaina; Haas, Kurt

    2015-01-01

    The classical view of mitochondria as housekeeping organelles acting in the background to simply maintain cellular energy demands has been challenged by mounting evidence of their direct and active participation in synaptic plasticity in neurons. Time-lapse imaging has revealed that mitochondria are motile in dendrites, with their localization and fusion and fission events regulated by synaptic activity. The positioning of mitochondria directly influences function of nearby synapses through multiple pathways including control over local concentrations of ATP, Ca2+ and reactive oxygen species. Recent studies have also shown that mitochondrial protein cascades, classically associated with apoptosis, are involved in neural plasticity in healthy cells. These findings link mitochondria to the plasticity- and metaplasticity-associated activity-dependent transcription factor myocyte enhancer factor 2 (MEF2), further repositioning mitochondria as potential command centres for regulation of synaptic plasticity. Intriguingly, MEF2 and mitochondrial functions appear to be intricately intertwined, as MEF2 is a target of mitochondrial apoptotic caspases and, in turn, MEF2 regulates mitochondrial genome transcription essential for production of superoxidase and hydrogen peroxidase. Here, we review evidence supporting mitochondria as central organelles controlling the spatiotemporal expression of neuronal plasticity, and attempt to disentangle the MEF2–mitochondria relationship mediating these functions. PMID:25581818

  16. Automatic Generation of Connectivity for Large-Scale Neuronal Network Models through Structural Plasticity

    PubMed Central

    Diaz-Pier, Sandra; Naveau, Mikaël; Butz-Ostendorf, Markus; Morrison, Abigail

    2016-01-01

    With the emergence of new high performance computation technology in the last decade, the simulation of large scale neural networks which are able to reproduce the behavior and structure of the brain has finally become an achievable target of neuroscience. Due to the number of synaptic connections between neurons and the complexity of biological networks, most contemporary models have manually defined or static connectivity. However, it is expected that modeling the dynamic generation and deletion of the links among neurons, locally and between different regions of the brain, is crucial to unravel important mechanisms associated with learning, memory and healing. Moreover, for many neural circuits that could potentially be modeled, activity data is more readily and reliably available than connectivity data. Thus, a framework that enables networks to wire themselves on the basis of specified activity targets can be of great value in specifying network models where connectivity data is incomplete or has large error margins. To address these issues, in the present work we present an implementation of a model of structural plasticity in the neural network simulator NEST. In this model, synapses consist of two parts, a pre- and a post-synaptic element. Synapses are created and deleted during the execution of the simulation following local homeostatic rules until a mean level of electrical activity is reached in the network. We assess the scalability of the implementation in order to evaluate its potential usage in the self generation of connectivity of large scale networks. We show and discuss the results of simulations on simple two population networks and more complex models of the cortical microcircuit involving 8 populations and 4 layers using the new framework. PMID:27303272

  17. Structural and functional plasticity of subcellular tethering, targeting and processing of RPGRIP1 by RPGR isoforms

    PubMed Central

    Patil, Hemangi; Guruju, Mallikarjuna R.; Cho, Kyoung-in; Yi, Haiqing; Orry, Andrew; Kim, Hyesung; Ferreira, Paulo A.

    2012-01-01

    Summary Mutations affecting the retinitis pigmentosa GTPase regulator-interacting protein 1 (RPGRIP1) interactome cause syndromic retinal dystrophies. RPGRIP1 interacts with the retinitis pigmentosa GTPase regulator (RPGR) through a domain homologous to RCC1 (RHD), a nucleotide exchange factor of Ran GTPase. However, functional relationships between RPGR and RPGRIP1 and their subcellular roles are lacking. We show by molecular modeling and analyses of RPGR disease-mutations that the RPGR-interacting domain (RID) of RPGRIP1 embraces multivalently the shared RHD of RPGR1–19 and RPGRORF15 isoforms and the mutations are non-overlapping with the interface found between RCC1 and Ran GTPase. RPGR disease-mutations grouped into six classes based on their structural locations and differential impairment with RPGRIP1 interaction. RPGRIP1α1 expression alone causes its profuse self-aggregation, an effect suppressed by co-expression of either RPGR isoform before and after RPGRIP1α1 self-aggregation ensue. RPGR1–19 localizes to the endoplasmic reticulum, whereas RPGRORF15 presents cytosolic distribution and they determine uniquely the subcellular co-localization of RPGRIP1α1. Disease mutations in RPGR1–19, RPGRORF15, or RID of RPGRIP1α1, singly or in combination, exert distinct effects on the subcellular targeting, co-localization or tethering of RPGRIP1α1 with RPGR1–19 or RPGRORF15 in kidney, photoreceptor and hepatocyte cell lines. Additionally, RPGRORF15, but not RPGR1–19, protects the RID of RPGRIP1α1 from limited proteolysis. These studies define RPGR- and cell-type-dependent targeting pathways with structural and functional plasticity modulating the expression of mutations in RPGR and RPGRIP1. Further, RPGR isoforms distinctively determine the subcellular targeting of RPGRIP1α1, with deficits in RPGRORF15-dependent intracellular localization of RPGRIP1α1 contributing to pathomechanisms shared by etiologically distinct syndromic retinal dystrophies. PMID

  18. Activity-dependent regulation of genes implicated in X-linked non-specific mental retardation.

    PubMed

    Boda, B; Mas, C; Muller, D

    2002-01-01

    X-linked forms of non-specific mental retardation are complex disorders, for which mutations in several genes have recently been identified. These include OPHN1, GDI1, PAK3, IL1RAPL, TM4SF2, FMR2 and RSK2. To investigate the mechanisms through which alterations of these gene products could result in cognitive impairment, we analyzed their expression using quantitative PCR technique in two in vitro models of activity-dependent gene regulation: kainate-induced seizures and long-term synaptic potentiation (LTP). We found that the level of expression of four genes, PAK3, IL1RAPL, RSK2 and TM4SF2, was significantly up-regulated following kainate treatment. Furthermore we observed a significant increase in mRNA levels of PAK3 and IL1RAPL following LTP induction. These results suggest a possible role for these four genes in activity-dependent brain plasticity.

  19. RAD sequencing resolves fine-scale population structure in a benthic invertebrate: implications for understanding phenotypic plasticity

    PubMed Central

    Weigand, Hannah; Weiss, Martina; Fawcett, Katie; Lehman, Katrin; Clark, M. S.; Leese, Florian; McMinn, Carrie; Moore, Heather; Hoffman, Joseph I.

    2017-01-01

    The field of molecular ecology is transitioning from the use of small panels of classical genetic markers such as microsatellites to much larger panels of single nucleotide polymorphisms (SNPs) generated by approaches like RAD sequencing. However, few empirical studies have directly compared the ability of these methods to resolve population structure. This could have implications for understanding phenotypic plasticity, as many previous studies of natural populations may have lacked the power to detect genetic differences, especially over micro-geographic scales. We therefore compared the ability of microsatellites and RAD sequencing to resolve fine-scale population structure in a commercially important benthic invertebrate by genotyping great scallops (Pecten maximus) from nine populations around Northern Ireland at 13 microsatellites and 10 539 SNPs. The shells were then subjected to morphometric and colour analysis in order to compare patterns of phenotypic and genetic variation. We found that RAD sequencing was superior at resolving population structure, yielding higher Fst values and support for two distinct genetic clusters, whereas only one cluster could be detected in a Bayesian analysis of the microsatellite dataset. Furthermore, appreciable phenotypic variation was observed in size-independent shell shape and coloration, including among localities that could not be distinguished from one another genetically, providing support for the notion that these traits are phenotypically plastic. Taken together, our results suggest that RAD sequencing is a powerful approach for studying population structure and phenotypic plasticity in natural populations. PMID:28386419

  20. Plasticity to simulated shade is associated with altitude in structured populations of Arabidopsis thaliana.

    PubMed

    Botto, Javier F

    2015-07-01

    Plants compete for photosynthesis light and induce a shade avoidance syndrome (SAS) that confers an important advantage in asymmetric competition for light at high canopy densities. Shade plasticity was studied in a greenhouse experiment cultivating Arabidopsis thaliana plants from 15 populations spread across an altitudinal gradient in the northeast area of Spain that contain a high genetic variation into a reduced geographical range. Plants were exposed to sunlight or simulated shade to identify the range of shade plasticity. Fourteen vegetative, flowering and reproductive traits were measured throughout the life cycle. Shade plasticity in flowering time and dry mass was significantly associated with the altitude of population origin. Plants from coastal populations showed higher shade plasticity indexes than those from mountains. The altitudinal variation in flowering leaf plasticity adjusted negatively with average and minimum temperatures, whereas dry mass plasticity was better explained by negative regressions with the average, maximum and minimum temperatures, and by a positive regression with average precipitation of the population origin. The lack of an altitudinal gradient for the widest number of traits suggests that shade light could be a driver explaining the distribution pattern of individuals in smaller geographical scales than those explored here.

  1. Structural modifications induced by compressive plastic deformation in single-step and sequentially irradiated UHMWPE for hip joint components.

    PubMed

    Puppulin, Leonardo; Sugano, Nobuhiko; Zhu, Wenliang; Pezzotti, Giuseppe

    2014-03-01

    Structural modifications were studied at the molecular scale in two highly crosslinked UHMWPE materials for hip-joint acetabular components, as induced upon application of (uniaxial) compressive strain to the as-manufactured microstructures. The two materials, quite different in their starting resins and belonging to different manufacturing generations, were a single-step irradiated and a sequentially irradiated polyethylene. The latter material represents the most recently launched gamma-ray-irradiated polyethylene material in the global hip implant market. Confocal/polarized Raman spectroscopy was systematically applied to characterize the initial microstructures and the microstructural response of the materials to plastic deformation. Crystallinity fractions and preferential orientation of molecular chains have been followed up during in vitro deformation tests on unused cups and correlated to plastic strain magnitude and to the recovery capacity of the material. Moreover, analyses of the in vivo deformation behavior of two short-term retrieved hip cups are also presented. Trends of preferential orientation of molecular chains as a function of residual strain were similar for both materials, but distinctly different in their extents. The sequentially irradiated material was more resistant to plastic deformation and, for the same magnitude of residual plastic strain, possessed a higher capacity of recovery as compared to the single-step irradiated one.

  2. Flexible crossbar-structured resistive memory arrays on plastic substrates via inorganic-based laser lift-off.

    PubMed

    Kim, Seungjun; Son, Jung Hwan; Lee, Seung Hyun; You, Byoung Kuk; Park, Kwi-Il; Lee, Hwan Keon; Byun, Myunghwan; Lee, Keon Jae

    2014-11-26

    Crossbar-structured memory comprising 32 × 32 arrays with one selector-one resistor (1S-1R) components are initially fabricated on a rigid substrate. They are transferred without mechanical damage via an inorganic-based laser lift-off (ILLO) process as a result of laser-material interaction. Addressing tests of the transferred memory arrays are successfully performed to verify mitigation of cross-talk on a plastic substrate.

  3. Trigeminothalamic barrelette neurons: natural structural side asymmetries and sensory input-dependent plasticity in adult rats.

    PubMed

    Negredo, P; Martin, Y B; Lagares, A; Castro, J; Villacorta, J A; Avendaño, C

    2009-11-10

    In the rodent trigeminal principal nucleus (Pr5) the barrelette thalamic-projecting neurons relay information from individual whiskers to corresponding contralateral thalamic barreloids. Here we investigated the presence of lateral asymmetries in the dendritic trees of these neurons, and the morphometric changes resulting from input-dependent plasticity in young adult rats. After retrograde labeling with dextran amines from the thalamus, neurons were digitally reconstructed with Neurolucida, and metrically and topologically analyzed with NeuroExplorer. The most unexpected and remarkable result was the observation of side-to-side asymmetries in the barrelette neurons of control rats. These asymmetries more significantly involved the number of low-grade trees and the total dendritic length, which were greater on the left side. Chronic global input loss resulting from infraorbital nerve (IoN) transection, or loss of active touch resulting from whisker clipping in the right neutralized, or even reversed, the observed lateral differences. While results after IoN transection have to be interpreted in the context of partial neuron death in this model, profound bilateral changes were found after haptic loss, which is achieved without inflicting any nerve damage. After whisker trimming, neurons on the left side closely resembled neurons on the right in controls, the natural dendritic length asymmetry being reversed mainly by a shortening of the left trees and a more moderate elongation of the right trees. These results demonstrate that dendritic morphometry is both side- and input-dependent, and that unilateral manipulation of the sensory periphery leads to bilateral morphometric changes in second order neurons of the whisker-barrel system. The presence of anatomical asymmetries in neural structures involved in early stages of somatosensory processing could help explain the expression of sensory input-dependent behavioral asymmetries.

  4. Mechanical properties and structural features of novel Fe-based bulk metallic glasses with unprecedented plasticity

    NASA Astrophysics Data System (ADS)

    Yang, Weiming; Liu, Haishun; Zhao, Yucheng; Inoue, Akihisa; Jiang, Kemin; Huo, Juntao; Ling, Haibo; Li, Qiang; Shen, Baolong

    2014-08-01

    Fe-based bulk metallic glasses (BMGs) have attracted great attention due to their unique magnetic and mechanical properties, but few applications have been materialized because of their brittleness at room temperature. Here we report a new Fe50Ni30P13C7 BMG which exhibits unprecedented compressive plasticity (>20%) at room temperature without final fracture. The mechanism of unprecedented plasticity for this new Fe-based BMG was also investigated. It was discovered that the ductile Fe50Ni30P13C7 BMG is composed of unique clusters mainly linked by less directional metal-metal bonds which are inclined to accommodate shear strain and absorbed energy in the front of crack tip. This conclusion was further verified by the X-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy experiments of Fe80-xNixP13C7 (x = 0, 10, 20, 30) and Fe72-xNixB20Si4Nb4 (x = 0, 7.2, 14.4, 21.6, 28.8) glassy systems. The results also indicate a strong correlation between the p-d hybridization and plasticity, verifying that the transition from brittle to ductile induced by Ni addition is due to the change of bonding characteristics in atomic configurations. Thus, we can design the plasticity of Fe-based BMGs and open up a new possible pathway for manufacturing BMGs with high strength and plasticity.

  5. Mechanical properties and structural features of novel Fe-based bulk metallic glasses with unprecedented plasticity.

    PubMed

    Yang, Weiming; Liu, Haishun; Zhao, Yucheng; Inoue, Akihisa; Jiang, Kemin; Huo, Juntao; Ling, Haibo; Li, Qiang; Shen, Baolong

    2014-08-29

    Fe-based bulk metallic glasses (BMGs) have attracted great attention due to their unique magnetic and mechanical properties, but few applications have been materialized because of their brittleness at room temperature. Here we report a new Fe(50)Ni(30)P(13)C(7) BMG which exhibits unprecedented compressive plasticity (>20%) at room temperature without final fracture. The mechanism of unprecedented plasticity for this new Fe-based BMG was also investigated. It was discovered that the ductile Fe(50)Ni(30)P(13)C(7) BMG is composed of unique clusters mainly linked by less directional metal-metal bonds which are inclined to accommodate shear strain and absorbed energy in the front of crack tip. This conclusion was further verified by the X-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy experiments of Fe(80-x)Ni(x)P(13)C(7) (x = 0, 10, 20, 30) and Fe(72-x)Ni(x)B(20)Si(4)Nb(4) (x = 0, 7.2, 14.4, 21.6, 28.8) glassy systems. The results also indicate a strong correlation between the p-d hybridization and plasticity, verifying that the transition from brittle to ductile induced by Ni addition is due to the change of bonding characteristics in atomic configurations. Thus, we can design the plasticity of Fe-based BMGs and open up a new possible pathway for manufacturing BMGs with high strength and plasticity.

  6. Activity-dependent expression of brain-derived neurotrophic factor in dendrites: facts and open questions.

    PubMed

    Tongiorgi, Enrico

    2008-08-01

    Long-lasting synaptic changes in transmission and morphology at the basis of memory storage, require delivery of newly synthesized proteins to affected synapses. Although many of these proteins are generated in the cell body, several key molecules for plasticity can be delivered in the form of silent mRNAs at synapses in extra somatic compartments where they are locally translated. One of such mRNAs encodes brain-derived neurotrophic factor (BDNF), a key molecule in neuronal development, learning and memory. A single BDNF protein is produced from several splice variants having a different 5' untranslated region. These mRNA variants have a different subcellular localization (soma, proximal or distal dendritic compartment) and may represent a spatial code for a local control of BDNF availability. This review will highlight current knowledge on the mechanisms of spatial and temporal regulation of activity-dependent BDNF mRNA localization in dendrites in relation with synaptic plasticity.

  7. Biodegradability of Plastics

    PubMed Central

    Tokiwa, Yutaka; Calabia, Buenaventurada P.; Ugwu, Charles U.; Aiba, Seiichi

    2009-01-01

    Plastic is a broad name given to different polymers with high molecular weight, which can be degraded by various processes. However, considering their abundance in the environment and their specificity in attacking plastics, biodegradation of plastics by microorganisms and enzymes seems to be the most effective process. When plastics are used as substrates for microorganisms, evaluation of their biodegradability should not only be based on their chemical structure, but also on their physical properties (melting point, glass transition temperature, crystallinity, storage modulus etc.). In this review, microbial and enzymatic biodegradation of plastics and some factors that affect their biodegradability are discussed. PMID:19865515

  8. Biodegradability of plastics.

    PubMed

    Tokiwa, Yutaka; Calabia, Buenaventurada P; Ugwu, Charles U; Aiba, Seiichi

    2009-08-26

    Plastic is a broad name given to different polymers with high molecular weight, which can be degraded by various processes. However, considering their abundance in the environment and their specificity in attacking plastics, biodegradation of plastics by microorganisms and enzymes seems to be the most effective process. When plastics are used as substrates for microorganisms, evaluation of their biodegradability should not only be based on their chemical structure, but also on their physical properties (melting point, glass transition temperature, crystallinity, storage modulus etc.). In this review, microbial and enzymatic biodegradation of plastics and some factors that affect their biodegradability are discussed.

  9. Core-shell structured titanium-nitrogen alloys with high strength, high thermal stability and good plasticity.

    PubMed

    Zhang, Y S; Zhao, Y H; Zhang, W; Lu, J W; Hu, J J; Huo, W T; Zhang, P X

    2017-01-06

    Multifunctional materials with more than two good properties are widely required in modern industries. However, some properties are often trade-off with each other by single microstructural designation. For example, nanostructured materials have high strength, but low ductility and thermal stability. Here by means of spark plasma sintering (SPS) of nitrided Ti particles, we synthesized bulk core-shell structured Ti alloys with isolated soft coarse-grained Ti cores and hard Ti-N solid solution shells. The core-shell Ti alloys exhibit a high yield strength (~1.4 GPa) comparable to that of nanostructured states and high thermal stability (over 1100 °C, 0.71 of melting temperature), contributed by the hard Ti-N shells, as well as a good plasticity (fracture plasticity of 12%) due to the soft Ti cores. Our results demonstrate that this core-shell structure offers a design pathway towards an advanced material with enhancing strength-plasticity-thermal stability synergy.

  10. Onset of plasticity and its relation to structure in CuZr metallic glasses: a molecular dynamics study

    NASA Astrophysics Data System (ADS)

    Gutierrez, Gonzalo; Sepulveda, Matias; Amigo, Nicolas

    2015-03-01

    The plastic behavior of crystalline metals is well understood. It is known that this regime is mainly mediated by the nucleation and propagation of dislocations as well as by grain boundary sliding. In metallic glasses (MGs), the plastic behavior is quite different from their crystalline counterparts. It is well known that bulk metallic glasses, in addition to the high yield strength and a elastic deformation to a strain limit about 2 % (i.e., more than an order of magnitude greater than conventional crystalline metals), are brittle at room temperature. Interestingly, MG nanowires present an important degree of ductillity, and is an ideal system to study the onset of plasticity in MG. Here we present a computational tensile test which shows the evolution of the atomic structure of a Cu50Zr50 metallic glass nanowire at 300 K according to the applied strain increased. The system consists of a million atoms CuZr nanowire metallic glass. Local structure of atoms is analyzed by means of the Voronoi polyhedral technique and the nucleation and propagation of SBs by monitoring the atomic strain. Supported by grant Fondecyt-Chile 1120603.

  11. Core-shell structured titanium-nitrogen alloys with high strength, high thermal stability and good plasticity

    NASA Astrophysics Data System (ADS)

    Zhang, Y. S.; Zhao, Y. H.; Zhang, W.; Lu, J. W.; Hu, J. J.; Huo, W. T.; Zhang, P. X.

    2017-01-01

    Multifunctional materials with more than two good properties are widely required in modern industries. However, some properties are often trade-off with each other by single microstructural designation. For example, nanostructured materials have high strength, but low ductility and thermal stability. Here by means of spark plasma sintering (SPS) of nitrided Ti particles, we synthesized bulk core-shell structured Ti alloys with isolated soft coarse-grained Ti cores and hard Ti-N solid solution shells. The core-shell Ti alloys exhibit a high yield strength (~1.4 GPa) comparable to that of nanostructured states and high thermal stability (over 1100 °C, 0.71 of melting temperature), contributed by the hard Ti-N shells, as well as a good plasticity (fracture plasticity of 12%) due to the soft Ti cores. Our results demonstrate that this core-shell structure offers a design pathway towards an advanced material with enhancing strength-plasticity-thermal stability synergy.

  12. Core-shell structured titanium-nitrogen alloys with high strength, high thermal stability and good plasticity

    PubMed Central

    Zhang, Y. S.; Zhao, Y. H.; Zhang, W.; Lu, J. W.; Hu, J. J.; Huo, W. T.; Zhang, P. X.

    2017-01-01

    Multifunctional materials with more than two good properties are widely required in modern industries. However, some properties are often trade-off with each other by single microstructural designation. For example, nanostructured materials have high strength, but low ductility and thermal stability. Here by means of spark plasma sintering (SPS) of nitrided Ti particles, we synthesized bulk core-shell structured Ti alloys with isolated soft coarse-grained Ti cores and hard Ti-N solid solution shells. The core-shell Ti alloys exhibit a high yield strength (~1.4 GPa) comparable to that of nanostructured states and high thermal stability (over 1100 °C, 0.71 of melting temperature), contributed by the hard Ti-N shells, as well as a good plasticity (fracture plasticity of 12%) due to the soft Ti cores. Our results demonstrate that this core-shell structure offers a design pathway towards an advanced material with enhancing strength-plasticity-thermal stability synergy. PMID:28059150

  13. Evaluation of the thermal efficiency of a high-temperature heat-insulation structure based on honeycomb plastic

    NASA Astrophysics Data System (ADS)

    Ryzhenkov, A. V.; Lapin, E. E.; Loginova, N. A.; Sitdikov, D. R.; Grigor'ev, S. V.

    2016-06-01

    Highly efficient heat-insulation materials are needed in order to reduce the heat losses in operation of heat-power equipment at temperatures up to 700°C. A review of the available solutions showed that the development of a high-temperature heat-insulation structure of a new type is needed. The basic features of application of honeycomb plastics in heat insulation of heat-power equipment are discussed, the known techniques for evaluating the heat conductance of such materials are reviewed, and the results of calculation-parametric studies on determining the optimum honeycomb design for heat-insulation structures are reported.

  14. Repetitive transcranial magnetic stimulation (rTMS) influences spatial cognition and modulates hippocampal structural synaptic plasticity in aging mice.

    PubMed

    Ma, Jun; Zhang, Zhanchi; Kang, Lin; Geng, Dandan; Wang, Yanyong; Wang, Mingwei; Cui, Huixian

    2014-10-01

    Normal aging is characteristic with the gradual decline in cognitive function associated with the progressive reduction of structural and functional plasticity in the hippocampus. Repetitive transcranial magnetic stimulation (rTMS) has developed into a novel neurological and psychiatric tool that can be used to investigate the neurobiology of cognitive function. Recent studies have demonstrated that low-frequency rTMS (≤1Hz) affects synaptic plasticity in rats with vascular dementia (VaD), and it ameliorates the spatial cognitive ability in mice with Aβ1-42-mediated memory deficits, but there are little concerns about the effects of rTMS on normal aging related cognition and synaptic plasticity changes. Thus, the current study investigated the effects of rTMS on spatial memory behavior, neuron and synapse morphology in the hippocampus, and synaptic protein markers and brain-derived neurotrophic factor (BDNF)/tropomyosin-related kinase B (TrkB) in normal aging mice, to illustrate the mechanisms of rTMS in regulating cognitive capacity. Relative to adult animals, aging caused hippocampal-dependent cognitive impairment, simultaneously inhibited the activation of the BDNF-TrkB signaling pathway, reduced the transcription and expression of synaptic protein markers: synaptophysin (SYN), growth associated protein 43 (GAP43) and post-synaptic density protein 95 (PSD95), as well as decreased synapse density and PSD (post-synaptic density) thickness. Interestingly, rTMS with low intensity (110% average resting motor threshold intensity, 1Hz, LIMS) triggered the activation of BDNF and TrkB, upregulated the level of synaptic protein markers, and increased synapse density and thickened PSD, and further reversed the spatial cognition dysfunction in aging mice. Conversely, high-intensity magnetic stimulation (150% average resting motor threshold intensity, 1Hz, HIMS) appeared to be detrimental, inducing thinning of PSDs, disordered synaptic structure, and a large number of

  15. Self-organized origami structures via ion-induced plastic strain.

    PubMed

    Chalapat, Khattiya; Chekurov, Nikolai; Jiang, Hua; Li, Jian; Parviz, Babak; Paraoanu, G S

    2013-01-04

    Ion processing of the reactive surface of a free-standing polycrystalline metal film induces a flow of atoms into grain boundaries, resulting in plastic deformation. A thorough experimental and theoretical analysis of this process is presented, along with the demonstration of novel engineering concepts for precisely controlled 3D assembly at micro- and nanoscopic scales.

  16. New disordering mode for TFSI- anions: the nonequilibrium, plastic crystalline structure of Et4NTFSI.

    PubMed

    Henderson, Wesley A; Herstedt, Marie; Young, Victor G; Passerini, Stefano; De Long, Hugh C; Trulove, Paul C

    2006-02-20

    A new TFSI- anion disordering mode has been discovered in a supercooled plastic crystalline phase of Et4NTFSI, which may, in part, account for the low melting points of TFSI- salts with organic cations, thereby forming ionic liquids, and the intriguing properties of LiTFSI for lithium battery applications.

  17. Diffusion dynamics of synaptic molecules during inhibitory postsynaptic plasticity

    PubMed Central

    Petrini, Enrica Maria; Barberis, Andrea

    2014-01-01

    The plasticity of inhibitory transmission is expected to play a key role in the modulation of neuronal excitability and network function. Over the last two decades, the investigation of the determinants of inhibitory synaptic plasticity has allowed distinguishing presynaptic and postsynaptic mechanisms. While there has been a remarkable progress in the characterization of presynaptically-expressed plasticity of inhibition, the postsynaptic mechanisms of inhibitory long-term synaptic plasticity only begin to be unraveled. At postsynaptic level, the expression of inhibitory synaptic plasticity involves the rearrangement of the postsynaptic molecular components of the GABAergic synapse, including GABAA receptors, scaffold proteins and structural molecules. This implies a dynamic modulation of receptor intracellular trafficking and receptor surface lateral diffusion, along with regulation of the availability and distribution of scaffold proteins. This Review will focus on the mechanisms of the multifaceted molecular reorganization of the inhibitory synapse during postsynaptic plasticity, with special emphasis on the key role of protein dynamics to ensure prompt and reliable activity-dependent adjustments of synaptic strength. PMID:25294987

  18. Determination of the structural changes by Raman and {sup 13}C CP/MAS NMR spectroscopy on native corn starch with plasticizers

    SciTech Connect

    Cozar, O.; Filip, C.; Tripon, C.; Cioica, N.; Coţa, C.; Nagy, E. M.

    2013-11-13

    The plasticizing - antiplasticizing effect of water and glycerol contents on native corn starch samples is investigated by FT-Raman and {sup 13}C CP/MAS NMR spectroscopy. The presence of both amorphous and crystalline structural phases was evidenced in pure native corn starch and also in the samples containing plasticizers. Among the crystalline starch structures, the A- and V- types were suggested by CP/MAS NMR spectra.

  19. Plastic Surgery

    MedlinePlus

    ... Loss Surgery? A Week of Healthy Breakfasts Shyness Plastic Surgery KidsHealth > For Teens > Plastic Surgery Print A ... her forehead lightened with a laser? What Is Plastic Surgery? Just because the name includes the word " ...

  20. Chronic Mild Stress Modulates Activity-Dependent Transcription of BDNF in Rat Hippocampal Slices.

    PubMed

    Molteni, Raffaella; Rossetti, Andrea C; Savino, Elisa; Racagni, Giorgio; Calabrese, Francesca

    2016-01-01

    Although activity-dependent transcription represents a crucial mechanism for long-lasting experience-dependent changes in the hippocampus, limited data exist on its contribution to pathological conditions. We aim to investigate the influence of chronic stress on the activity-dependent transcription of brain-derived neurotrophic factor (BDNF). The ex vivo methodology of acute stimulation of hippocampal slices obtained from rats exposed to chronic mild stress (CMS) was used to evaluate whether the adverse experience may alter activity-dependent BDNF gene expression. CMS reduces BDNF expression and that acute depolarization significantly upregulates total BDNF mRNA levels only in control animals, showing that CMS exposure may alter BDNF transcription under basal conditions and during neuronal activation. Moreover, while the basal effect of CMS on total BDNF reflects parallel modulations of all the transcripts examined, isoform-specific changes were found after depolarization. This different effect was also observed in the activation of intracellular signaling pathways related to the neurotrophin. In conclusion, our study discloses a functional alteration of BDNF transcription as a consequence of stress. Being the activity-regulated transcription a critical process in synaptic and neuronal plasticity, the different regulation of individual BDNF promoters may contribute to long-lasting changes, which are fundamental for the vulnerability of the hippocampus to stress-related diseases.

  1. Dynamic DNA methylation in the brain: a new epigenetic mark for experience-dependent plasticity

    PubMed Central

    Tognini, Paola; Napoli, Debora; Pizzorusso, Tommaso

    2015-01-01

    Experience-dependent plasticity is the ability of brain circuits to undergo molecular, structural and functional changes as a function of neural activity. Neural activity continuously shapes our brain during all the stages of our life, from infancy through adulthood and beyond. Epigenetic modifications of histone proteins and DNA seem to be a leading molecular mechanism to modulate the transcriptional changes underlying the fine-tuning of synaptic connections and circuitry rewiring during activity-dependent plasticity. The recent discovery that cytosine methylation is an epigenetic mark particularly dynamic in brain cells has strongly increased the interest of neuroscientists in understanding the role of covalent modifications of DNA in activity-induced remodeling of neuronal circuits. Here, we provide an overview of the role of DNA methylation and hydroxylmethylation in brain plasticity both during adulthood, with emphasis on learning and memory related processes, and during postnatal development, focusing specifically on experience-dependent plasticity in the visual cortex. PMID:26379502

  2. Requirement for Plk2 in orchestrated ras and rap signaling, homeostatic structural plasticity, and memory.

    PubMed

    Lee, Kea Joo; Lee, Yeunkum; Rozeboom, Aaron; Lee, Ji-Yun; Udagawa, Noriko; Hoe, Hyang-Sook; Pak, Daniel T S

    2011-03-10

    Ras and Rap small GTPases are important for synaptic plasticity and memory. However, their roles in homeostatic plasticity are unknown. Here, we report that polo-like kinase 2 (Plk2), a homeostatic suppressor of overexcitation, governs the activity of Ras and Rap via coordination of their regulatory proteins. Plk2 directs elimination of Ras activator RasGRF1 and Rap inhibitor SPAR via phosphorylation-dependent ubiquitin-proteasome degradation. Conversely, Plk2 phosphorylation stimulates Ras inhibitor SynGAP and Rap activator PDZGEF1. These Ras/Rap regulators perform complementary functions to downregulate dendritic spines and AMPA receptors following elevated activity, and their collective regulation by Plk2 profoundly stimulates Rap and suppresses Ras. Furthermore, perturbation of Plk2 disrupts Ras and Rap signaling, prevents homeostatic shrinkage and loss of dendritic spines, and impairs proper memory formation. Our study demonstrates a critical role of Plk2 in the synchronized tuning of Ras and Rap and underscores the functional importance of this regulation in homeostatic synaptic plasticity.

  3. Finite deformation analysis of continuum structures with time dependent anisotropic elastic plastic material behavior (LWBR/AWBA Development Program)

    SciTech Connect

    Hutula, D.N.

    1980-03-01

    A finite element procedure is presented for finite deformation analysis of continuum structures with time-dependent anisotropic elastic-plastic material behavior. An updated Lagrangian formulation is used to describe the kinematics of deformation. Anisotropic constitutive relations are referred, at each material point, to a set of three mutually orthogonal axes which rotate as a unit with an angular velocity equal to the spin at the point. The time-history of the solution is generated by using a linear incremental procedure with residual force correction, along with an automatic time step control algorithm which chooses time step sizes to control the accuracy and numerical stability of the solution.

  4. Structure of aging Al-Li-Cu-Zr-Sc-Ag alloy after severe plastic deformation and long-term storage

    NASA Astrophysics Data System (ADS)

    Kaigorodova, L. I.; Rasposienko, D. Yu.; Pushin, V. G.; Pilyugin, V. P.; Smirnov, S. V.

    2015-11-01

    Structural and phase transformations in commercial aging aluminum-lithium Al-1.2 Li-3.2 Cu-0.09 Zr-0.11 Sc-0.4 Ag-0.3 Mg alloy have been studied after severe plastic deformation by high-pressure torsion (at a pressure of 4 GPa with 1, 5, and 10 revolutions of the anvil) and natural aging (roomtemperature storage) for 1 week and 2 years. It has been found that, in this case, the process of static recrystallization is achieved in the alloy, the degree of which increases with an increasing degree of deformation and time of storage.

  5. Activity-Dependent Plasticity of Spinal Locomotion: Implications for Sensory Processing

    PubMed Central

    Edgerton, V. Reggie; Roy, Roland R.

    2009-01-01

    The lumbosacral spinal cord of mammals contains the neural circuitry capable of generating full weight-bearing locomotion of the hindlimbs without any supraspinal input. One or more interventions, e.g., pharmacological, epidural stimulation, and/or locomotor training, however, are necessary to gain access to and modulate the properties of this circuitry, and to facilitate recovery of full weight-bearing locomotion after spinal cord injury. PMID:19955866

  6. Structure-property relation in HPMC polymer films plasticized with Sorbitol

    NASA Astrophysics Data System (ADS)

    Prakash, Y.; Somashekarappa, H.; Mahadevaiah, Somashekar, R.

    2013-06-01

    A correlation study on physical and mechanical properties of Hydroxy propyl-methylcellulose (HPMC) polymer films plasticized with different weight ratio of Sorbitol, prepared using solution casting method, was carried out using wide angle X-ray technique and universal testing machine. It is found that the crystallanity decreases as the concentration of Sorbitol increases up to a certain concentration and there afterwards increases. Measured Physical Properties like tensile strength decreases and elongation (%) increases indicating increase in the flexibility of the films. These observations confirm the correlation between microstructal parameters and mechanical properties of films. These films are suitable for packaging food products.

  7. Effect of synaptic plasticity on the structure and dynamics of disordered networks of coupled neurons

    NASA Astrophysics Data System (ADS)

    Bayati, M.; Valizadeh, A.

    2012-07-01

    In an all-to-all network of integrate-and-fire neurons in which there is a disorder in the intrinsic oscillatory frequencies of the neurons, we show that through spike-timing-dependent plasticity the synapses which have the high-frequency neurons as presynaptic tend to be potentiated while the links originated from the low-frequency neurons are weakened. The emergent effective flow of directed connections introduces the high-frequency neurons as the more influential elements in the network and facilitates synchronization by decreasing the synaptic cost for onset of synchronization.

  8. Overexpression of Mineralocorticoid Receptors Partially Prevents Chronic Stress-Induced Reductions in Hippocampal Memory and Structural Plasticity.

    PubMed

    Kanatsou, Sofia; Fearey, Brenna C; Kuil, Laura E; Lucassen, Paul J; Harris, Anjanette P; Seckl, Jonathan R; Krugers, Harm; Joels, Marian

    2015-01-01

    Exposure to chronic stress is a risk factor for cognitive decline and psychopathology in genetically predisposed individuals. Preliminary evidence in humans suggests that mineralocorticoid receptors (MRs) may confer resilience to these stress-related changes. We specifically tested this idea using a well-controlled mouse model for chronic stress in combination with transgenic MR overexpression in the forebrain. Exposure to unpredictable stressors for 21 days in adulthood reduced learning and memory formation in a low arousing hippocampus-dependent contextual learning task, but enhanced stressful contextual fear learning. We found support for a moderating effect of MR background on chronic stress only for contextual memory formation under low arousing conditions. In an attempt to understand potentially contributing factors, we studied structural plasticity. Chronic stress altered dendritic morphology in the hippocampal CA3 area and reduced the total number of doublecortin-positive immature neurons in the infrapyramidal blade of the dentate gyrus. The latter reduction was absent in MR overexpressing mice. We therefore provide partial support for the idea that overexpression of MRs may confer resilience to the effects of chronic stress on hippocampus-dependent function and structural plasticity.

  9. Effect of Severe Plastic Deformation on Structure and Properties of Al-Sc-Ta and Al-Sc-Ti Alloys.

    PubMed

    Berezina, Alla; Monastyrska, Tetiana; Davydenko, Olexandr; Molebny, Oleh; Polishchuk, Sergey

    2017-12-01

    The comparative analysis of the effect of monotonous and non-monotonous severe plastic deformations (SPD) on the structure and properties of aluminum alloys has been carried out. Conventional hydrostatic extrusion (HE) with a constant deformation direction and equal-channel angular hydroextrusion (ECAH) with an abrupt change in the deformation direction were chosen for the cases of monotonous and non-monotonous SPD, respectively. Model cast hypoeutectic Al-0.3%Sc alloys and hypereutectic Al-0.6%Sc alloys with Ta and Ti additives were chosen for studying. It was demonstrated that SPD of the alloys resulted in the segregation of the material into active and inactive zones which formed a banded structure. The active zones were shown to be bands of localized plastic deformation. The distance between zones was found to be independent of the accumulated strain degree and was in the range of 0.6-1 μm. Dynamic recrystallization in the active zones was observed using TEM. The dynamic recrystallization was accompanied by the formation of disclinations, deformation bands, low-angle, and high-angle boundaries, i.e., rotational deformation modes developed. The dynamic recrystallization was more intense during the non-monotonous deformation as compared with the monotonous one, which was confirmed by the reduction of texture degree in the materials after ECAH.

  10. Overexpression of Mineralocorticoid Receptors Partially Prevents Chronic Stress-Induced Reductions in Hippocampal Memory and Structural Plasticity

    PubMed Central

    Kanatsou, Sofia; Fearey, Brenna C.; Kuil, Laura E.; Lucassen, Paul J.; Harris, Anjanette P.; Seckl, Jonathan R.

    2015-01-01

    Exposure to chronic stress is a risk factor for cognitive decline and psychopathology in genetically predisposed individuals. Preliminary evidence in humans suggests that mineralocorticoid receptors (MRs) may confer resilience to these stress-related changes. We specifically tested this idea using a well-controlled mouse model for chronic stress in combination with transgenic MR overexpression in the forebrain. Exposure to unpredictable stressors for 21 days in adulthood reduced learning and memory formation in a low arousing hippocampus-dependent contextual learning task, but enhanced stressful contextual fear learning. We found support for a moderating effect of MR background on chronic stress only for contextual memory formation under low arousing conditions. In an attempt to understand potentially contributing factors, we studied structural plasticity. Chronic stress altered dendritic morphology in the hippocampal CA3 area and reduced the total number of doublecortin-positive immature neurons in the infrapyramidal blade of the dentate gyrus. The latter reduction was absent in MR overexpressing mice. We therefore provide partial support for the idea that overexpression of MRs may confer resilience to the effects of chronic stress on hippocampus-dependent function and structural plasticity. PMID:26600250

  11. Activity-dependent upregulation of presynaptic kainate receptors at immature CA3-CA1 synapses.

    PubMed

    Clarke, Vernon R J; Molchanova, Svetlana M; Hirvonen, Teemu; Taira, Tomi; Lauri, Sari E

    2014-12-10

    Presynaptic kainate-type glutamate receptors (KARs) regulate glutamate release probability and short-term plasticity in various areas of the brain. Here we show that long-term depression (LTD) in the area CA1 of neonatal rodent hippocampus is associated with an upregulation of tonic inhibitory KAR activity, which contributes to synaptic depression and causes a pronounced increase in short-term facilitation of transmission. This increased KAR function was mediated by high-affinity receptors and required activation of NMDA receptors, nitric oxide (NO) synthetase, and postsynaptic calcium signaling. In contrast, KAR activity was irreversibly downregulated in response to induction of long-term potentiation in a manner that depended on activation of the TrkB-receptor of BDNF. Both tonic KAR activity and its plasticity were restricted to early stages of synapse development and were lost in parallel with maturation of the network due to ongoing BDNF-TrkB signaling. These data show that presynaptic KARs are targets for activity-dependent modulation via diffusible messengers NO and BDNF, which enhance and depress tonic KAR activity at immature synapses, respectively. The plasticity of presynaptic KARs in the developing network allows nascent synapses to shape their response to incoming activity. In particular, upregulation of KAR function after LTD allows the synapse to preferentially pass high-frequency afferent activity. This can provide a potential rescue from synapse elimination by uncorrelated activity and also increase the computational dynamics of the developing CA3-CA1 circuitry.

  12. Dynamic rupture simulations on complex fault zone structures with off-fault plasticity using the ADER-DG method

    NASA Astrophysics Data System (ADS)

    Wollherr, Stephanie; Gabriel, Alice-Agnes; Igel, Heiner

    2015-04-01

    In dynamic rupture models, high stress concentrations at rupture fronts have to to be accommodated by off-fault inelastic processes such as plastic deformation. As presented in (Roten et al., 2014), incorporating plastic yielding can significantly reduce earlier predictions of ground motions in the Los Angeles Basin. Further, an inelastic response of materials surrounding a fault potentially has a strong impact on surface displacement and is therefore a key aspect in understanding the triggering of tsunamis through floor uplifting. We present an implementation of off-fault-plasticity and its verification for the software package SeisSol, an arbitrary high-order derivative discontinuous Galerkin (ADER-DG) method. The software recently reached multi-petaflop/s performance on some of the largest supercomputers worldwide and was a Gordon Bell prize finalist application in 2014 (Heinecke et al., 2014). For the nonelastic calculations we impose a Drucker-Prager yield criterion in shear stress with a viscous regularization following (Andrews, 2005). It permits the smooth relaxation of high stress concentrations induced in the dynamic rupture process. We verify the implementation by comparison to the SCEC/USGS Spontaneous Rupture Code Verification Benchmarks. The results of test problem TPV13 with a 60-degree dipping normal fault show that SeisSol is in good accordance with other codes. Additionally we aim to explore the numerical characteristics of the off-fault plasticity implementation by performing convergence tests for the 2D code. The ADER-DG method is especially suited for complex geometries by using unstructured tetrahedral meshes. Local adaptation of the mesh resolution enables a fine sampling of the cohesive zone on the fault while simultaneously satisfying the dispersion requirements of wave propagation away from the fault. In this context we will investigate the influence of off-fault-plasticity on geometrically complex fault zone structures like subduction

  13. Application of fiber-reinforced plastic rods as prestressing tendons in concrete structures. Final report

    SciTech Connect

    Mattock, A.H.; Babaei, K.

    1989-08-01

    The study is concerned with the possibility of utilizing fiber-reinforced plastic rods as prestressing tendons, in place of traditional steel tendons, in elements of prestressed-concrete bridges exposed to corrosive environments. A survey was made of available information on the behavior characteristics of fiber-reinforced plastic tension elements and, in particular, those of glass-fiber-reinforced (GFR) tension elements. Also, an analytical study was made of the flexural behavior of concrete elements prestressed by GFR tendons. Based on the analytical study and on the survey of available information, an assessment is made of the impact on the design of prestressed-concrete members if GFR tendons are used. Some preliminary design recommendations are made, together with proposals for research needed before GFR prestressing tendons should be used in practice. Four GFR tendons with Con-Tech Systems anchorages were tested, the primary variable being the embedded length of the GFR rods in the anchorages. All the tendons failed by the rods pulling out of the anchorages. For embedded lengths of 15.2 in or greater, the failure loads were 90% of the advertised tendon strength of 220 ksi, or about 100% of the guaranteed tensile strength of 197 ksi (60 kN/rod).

  14. Structure and microhardness of Al-Si-Cu-Ni alloy after severe plastic deformation and high-temperature annealing

    NASA Astrophysics Data System (ADS)

    Shvets, Karina; Khalikova, Gulnara; Korznikova, Elena; Trifonov, Vadim

    2015-10-01

    The effect of severe plastic deformation by high-pressure torsion (HPT) and subsequent annealing on the microstructure and microhardness of squeeze casting Al-22%Si-3%Cu-1.7%Ni alloy was investigated. HPT was performed at room temperature with 5 rotations under the pressure of 4 GPa. Annealing temperature range varied from 300 to 500°C for 5 min. HPT resulted in refinement and partial dissolution of the primary silicon and intermetallic particles in aluminum matrix and structure fragmentation that caused the microhardness increase. Subsequent annealing lead to the decomposition of the supersaturated solid solution that took place simultaneously with recovery and recrystallization of the fragmented structure. Increase of annealing temperature resulted in decrease of microhardness values.

  15. Structural plasticity of histones H3-H4 facilitates their allosteric exchange between RbAp48 and ASF1

    PubMed Central

    Zhang, Wei; Tyl, Marek; Ward, Richard; Sobott, Frank; Maman, Joseph; Murthy, Andal S.; Watson, Aleksandra A.; Fedorov, Oleg; Bowman, Andrew; Owen-Hughes, Tom; EL-Mkami, Hassane; Murzina, Natalia V.; Norman, David; Laue, Ernest D.

    2012-01-01

    The mechanisms by which histones are disassembled and reassembled into nucleosomes and chromatin structure during DNA replication, repair and transcription are poorly understood. A better understanding of the processes involved is, however, crucial if we are to understand whether and how histone variants and post-translationally modified histones are inherited in an epigenetic manner. To this end we have studied the interaction of histones H3–H4 with the human retinoblastoma-associated protein RbAp48 and their exchange with a second histone chaperone, anti-silencing function protein 1 (ASF1). Exchange of histones H3–H4 between these two histone chaperones plays a central role in the assembly of new nucleosomes and we show here that the H3–H4 complex has a surprising structural plasticity, which is important for this exchange. PMID:23178455

  16. When Music and Long-Term Memory Interact: Effects of Musical Expertise on Functional and Structural Plasticity in the Hippocampus

    PubMed Central

    Groussard, Mathilde; La Joie, Renaud; Rauchs, Géraldine; Landeau, Brigitte; Chételat, Gaël; Viader, Fausto; Desgranges, Béatrice; Eustache, Francis; Platel, Hervé

    2010-01-01

    The development of musical skills by musicians results in specific structural and functional modifications in the brain. Surprisingly, no functional magnetic resonance imaging (fMRI) study has investigated the impact of musical training on brain function during long-term memory retrieval, a faculty particularly important in music. Thus, using fMRI, we examined for the first time this process during a musical familiarity task (i.e., semantic memory for music). Musical expertise induced supplementary activations in the hippocampus, medial frontal gyrus, and superior temporal areas on both sides, suggesting a constant interaction between episodic and semantic memory during this task in musicians. In addition, a voxel-based morphometry (VBM) investigation was performed within these areas and revealed that gray matter density of the hippocampus was higher in musicians than in nonmusicians. Our data indicate that musical expertise critically modifies long-term memory processes and induces structural and functional plasticity in the hippocampus. PMID:20957158

  17. Structural plasticity of histones H3-H4 facilitates their allosteric exchange between RbAp48 and ASF1.

    PubMed

    Zhang, Wei; Tyl, Marek; Ward, Richard; Sobott, Frank; Maman, Joseph; Murthy, Andal S; Watson, Aleksandra A; Fedorov, Oleg; Bowman, Andrew; Owen-Hughes, Tom; El Mkami, Hassane; Murzina, Natalia V; Norman, David G; Laue, Ernest D

    2013-01-01

    The mechanisms by which histones are disassembled and reassembled into nucleosomes and chromatin structure during DNA replication, repair and transcription are poorly understood. A better understanding of the processes involved is, however, crucial if we are to understand whether and how histone variants and post-translationally modified histones are inherited in an epigenetic manner. To this end we have studied the interaction of the histone H3-H4 complex with the human retinoblastoma-associated protein RbAp48 and their exchange with a second histone chaperone, anti-silencing function protein 1 (ASF1). Exchange of histones H3-H4 between these two histone chaperones has a central role in the assembly of new nucleosomes, and we show here that the H3-H4 complex has an unexpected structural plasticity, which is important for this exchange.

  18. Structural evaluation of a mimicry-recognizing paratope: plasticity in antigen-antibody interactions manifests in molecular mimicry.

    PubMed

    Tapryal, Suman; Gaur, Vineet; Kaur, Kanwal J; Salunke, Dinakar M

    2013-07-01

    Molecular mimicry manifests antagonistically with respect to the specificity of immune recognition. However, it often occurs because different Ags share surface topologies in terms of shape or chemical nature. It also occurs when a flexible paratope accommodates dissimilar Ags by adjusting structural features according to the antigenic epitopes or differential positioning in the Ag combining site. Toward deciphering the structural basis of molecular mimicry, mAb 2D10 was isolated from a maturing immune response elicited against methyl α-d-mannopyranoside and also bound equivalently to a dodecapeptide. The physicochemical evidence of this carbohydrate-peptide mimicry in the case of mAb 2D10 had been established earlier. These studies had strongly suggested direct involvement of a flexible paratope in the observed mimicry. Surprisingly, comparison of the Ag-free structure of single-chain variable fragment 2D10 with those bound to sugar and peptide Ags revealed a conformationally invariant state of the Ab while binding to chemically and structurally disparate Ags. This equivalent binding of the two dissimilar Ags was through mutually independent interactions, demonstrating functional equivalence in the absence of structural correlation. Thus, existence of a multispecific, mature Ab in the secondary immune response was evident, as was the plasticity in the interactions while accommodating topologically diverse Ags. Although our data highlight the structural basis of receptor multispecificity, they also illustrate mechanisms adopted by the immune system to neutralize the escape mutants generated during pathogenic insult.

  19. MeCP2 is required for activity-dependent refinement of olfactory circuits

    PubMed Central

    Degano, Alicia L.; Park, Min Jung; Penati, Judy; Li, Qun; Ronnett, Gabriele V.

    2014-01-01

    Methyl CpG binding protein 2 (MeCP2) is a structural chromosomal protein involved in the regulation of gene expression. Alterations in the levels of MeCP2 have been related to neurodevelopmental disorders. Studies in mouse models of MeCP2 deficiency have demonstrated that this protein is important for neuronal maturation, neurite complexity, synaptogenesis, and synaptic plasticity. However, the mechanisms by which MeCP2 dysfunction leads to neurodevelopmental defects, and the role of activity, remain unclear, as most studies examine the adult nervous system, which may obfuscate the primary consequences of MeCP2 mutation. We hypothesize that MeCP2 plays a role during the formation and activity-driven maturation of neural circuits at early postnatal stages. To test this hypothesis, we use the olfactory system as a neurodevelopmental model. This system undergoes postnatal neurogenesis; axons from olfactory neurons form highly stereotyped projections to higher-order neurons, facilitating the detection of possible defects in the establishment of connectivity. In vivo olfactory stimulation paradigms were used to produce physiological synaptic activity in gene-targeted mice in which specific olfactory circuits are visualized. Our results reveal defective postnatal refinement of olfactory circuits in Mecp2 knock out (KO) mice after sensory (odorant) stimulation. This failure in refinement was associated with deficits in the normal responses to odorants, including brain-derived neurotrophic factor (BDNF) production, as well as changes in adhesion molecules known to regulate axonal convergence. The defective refinement observed in Mecp2 KO mice was prevented by daily treatment with ampakine beginning after the first postnatal week. These observations indicate that increasing synaptic activity at early postnatal stage might circumvent the detrimental effect of MeCP2 deficiency on circuitry maturation. The present results provide in vivo evidence in real time for the role of

  20. MeCP2 is required for activity-dependent refinement of olfactory circuits.

    PubMed

    Degano, Alicia L; Park, Min Jung; Penati, Judith; Li, Qun; Ronnett, Gabriele V

    2014-03-01

    Methyl CpG binding protein 2 (MeCP2) is a structural chromosomal protein involved in the regulation of gene expression. Alterations in the levels of MeCP2 have been related to neurodevelopmental disorders. Studies in mouse models of MeCP2 deficiency have demonstrated that this protein is important for neuronal maturation, neurite complexity, synaptogenesis, and synaptic plasticity. However, the mechanisms by which MeCP2 dysfunction leads to neurodevelopmental defects, and the role of activity, remain unclear, as most studies examine the adult nervous system, which may obfuscate the primary consequences of MeCP2 mutation. We hypothesize that MeCP2 plays a role during the formation and activity-driven maturation of neural circuits at early postnatal stages. To test this hypothesis, we use the olfactory system as a neurodevelopmental model. This system undergoes postnatal neurogenesis; axons from olfactory neurons form highly stereotyped projections to higher-order neurons, facilitating the detection of possible defects in the establishment of connectivity. In vivo olfactory stimulation paradigms were used to produce physiological synaptic activity in gene-targeted mice in which specific olfactory circuits are visualized. Our results reveal defective postnatal refinement of olfactory circuits in Mecp2 knock out (KO) mice after sensory (odorant) stimulation. This failure in refinement was associated with deficits in the normal responses to odorants, including brain-derived neurotrophic factor (BDNF) production, as well as changes in adhesion molecules known to regulate axonal convergence. The defective refinement observed in Mecp2 KO mice was prevented by daily treatment with ampakine beginning after the first postnatal week. These observations indicate that increasing synaptic activity at early postnatal stage might circumvent the detrimental effect of MeCP2 deficiency on circuitry maturation. The present results provide in vivo evidence in real time for the role of

  1. The importance of material structure in the laser cutting of glass fiber reinforced plastic composites

    SciTech Connect

    Caprino, G. . Dipt. di Ingegneria dei Materiali e della Produzione); Tagliaferri, V. . Istituto di Ingegneria Meccanica); Covelli, L. )

    1995-01-01

    A previously proposed micromechanical formula, aiming to predict the vaporization energy Q[sub v] of composite materials as a function of fiber and matrix properties and fiber volume ratio, was assessed. The experimental data, obtained on glass fiber reinforced plastic panels with different fiber contents cut by a medium power CO[sub 2] cw laser, were treated according to a procedure previously suggested, in order to evaluate Q[sub v]. An excellent agreement was found between experimental and theoretical Q[sub v] values. Theory was then used to predict the response to laser cutting of a composite material with a fiber content varying along the thickness. The theoretical predictions indicated that, in this case, the interpretation of the experimental results may be misleading, bringing to errors in the evaluation of the material thermal properties, or in the prediction of the kerf depth. Some experimental data were obtained, confirming the theoretical findings.

  2. Mouse Social Network Dynamics and Community Structure are Associated with Plasticity-Related Brain Gene Expression

    PubMed Central

    Williamson, Cait M.; Franks, Becca; Curley, James P.

    2016-01-01

    Laboratory studies of social behavior have typically focused on dyadic interactions occurring within a limited spatiotemporal context. However, this strategy prevents analyses of the dynamics of group social behavior and constrains identification of the biological pathways mediating individual differences in behavior. In the current study, we aimed to identify the spatiotemporal dynamics and hierarchical organization of a large social network of male mice. We also sought to determine if standard assays of social and exploratory behavior are predictive of social behavior in this social network and whether individual network position was associated with the mRNA expression of two plasticity-related genes, DNA methyltransferase 1 and 3a. Mice were observed to form a hierarchically organized social network and self-organized into two separate social network communities. Members of both communities exhibited distinct patterns of socio-spatial organization within the vivaria that was not limited to only agonistic interactions. We further established that exploratory and social behaviors in standard behavioral assays conducted prior to placing the mice into the large group was predictive of initial network position and behavior but were not associated with final social network position. Finally, we determined that social network position is associated with variation in mRNA levels of two neural plasticity genes, DNMT1 and DNMT3a, in the hippocampus but not the mPOA. This work demonstrates the importance of understanding the role of social context and complex social dynamics in determining the relationship between individual differences in social behavior and brain gene expression. PMID:27540359

  3. Mouse Social Network Dynamics and Community Structure are Associated with Plasticity-Related Brain Gene Expression.

    PubMed

    Williamson, Cait M; Franks, Becca; Curley, James P

    2016-01-01

    Laboratory studies of social behavior have typically focused on dyadic interactions occurring within a limited spatiotemporal context. However, this strategy prevents analyses of the dynamics of group social behavior and constrains identification of the biological pathways mediating individual differences in behavior. In the current study, we aimed to identify the spatiotemporal dynamics and hierarchical organization of a large social network of male mice. We also sought to determine if standard assays of social and exploratory behavior are predictive of social behavior in this social network and whether individual network position was associated with the mRNA expression of two plasticity-related genes, DNA methyltransferase 1 and 3a. Mice were observed to form a hierarchically organized social network and self-organized into two separate social network communities. Members of both communities exhibited distinct patterns of socio-spatial organization within the vivaria that was not limited to only agonistic interactions. We further established that exploratory and social behaviors in standard behavioral assays conducted prior to placing the mice into the large group was predictive of initial network position and behavior but were not associated with final social network position. Finally, we determined that social network position is associated with variation in mRNA levels of two neural plasticity genes, DNMT1 and DNMT3a, in the hippocampus but not the mPOA. This work demonstrates the importance of understanding the role of social context and complex social dynamics in determining the relationship between individual differences in social behavior and brain gene expression.

  4. Low among-provenance differences in structural and functional plasticity in response to nutrients in saplings of the circum-Mediterranean tree Arbutus unedo L.

    PubMed

    Santiso, Xabier; Retuerto, Rubén

    2015-10-01

    The Mediterranean region is an area of special interest for conservation where the incidence of multiple drivers of global change is expected to increase. One of the factors predicted to change is soil-nutrient availability, an essential factor for plant growth. Thus, study of the effects of variation in this parameter is especially relevant in species with a circum-Mediterranean distribution, such as Arbutus unedo L., in which the different provenances grow in different habitats, which must differ in nutritional conditions. We aimed to determine the effect of provenance on plasticity, to establish whether structural and morphological traits differ in the level of plasticity and to assess how nutrients affect the photosynthetic light response. In a common garden experiment, we studied seven provenances from the circum-Mediterranean range of A. unedo and established two nutrient treatments (low and high nutrient availability). We measured physiological and structural traits in 1-year-old sapling and determined a phenotypic plasticity index (PPI) to quantify the level of plasticity, whereas the radiation effects were tested by construction and analysis of light response curves. Interestingly, provenance did not explain a significant amount of variance, but the plasticity was four times higher for the structural traits than for the physiological traits. Therefore, the plasticity to nutrient availability will not favour or prevent the expansion or contraction of the range of any of these provenances of A. unedo. Furthermore, the structural plasticity demonstrated the ability of the strawberry tree to optimize resource allocation, whereas the physiology remained stable, thus avoiding extra expenditure. The study findings also suggest that increased availability of nutrients would improve the performance of the species during the Mediterranean summer, characterized by high irradiance. These abilities will be key to the survival of saplings of the species under the future

  5. Reconciling species-level vs plastic responses of evergreen leaf structure to light gradients: shade leaves punch above their weight.

    PubMed

    Lusk, Christopher H; Onoda, Yusuke; Kooyman, Robert; Gutiérrez-Girón, Alba

    2010-04-01

    *When grown in a common light environment, the leaves of shade-tolerant evergreen trees have a larger leaf mass per unit area (LMA) than their light-demanding counterparts, associated with differences in lifespan. Yet plastic responses of LMA run counter to this pattern: shade leaves have smaller LMA than sun leaves, despite often living longer. *We measured LMA and cell wall content, and conducted punch and shear tests, on sun and shade leaves of 13 rainforest evergreens of differing shade tolerance, in order to understand adaptation vs plastic responses of leaf structure and biomechanics to shade. *Species shade tolerance and leaf mechanical properties correlated better with cell wall mass per unit area than with LMA. Growth light environment had less effect on leaf mechanics than on LMA: shade leaves had, on average, 40% lower LMA than sun leaves, but differences in work-to-shear, and especially force-to-punch, were smaller. This was associated with a slightly larger cell wall fraction in shade leaves. *The persistence of shade leaves might reflect unattractiveness to herbivores because they yield smaller benefits (cell contents per area) per unit fracture force than sun leaves. In forest trees, cell wall fraction and force-to-punch are more robust correlates of species light requirements than LMA.

  6. Structurally dissimilar antimanic agents modulate synaptic plasticity by regulating AMPA glutamate receptor subunit GluR1 synaptic expression.

    PubMed

    Du, Jing; Gray, Neil A; Falke, Cynthia; Yuan, Peixiong; Szabo, Steven; Manji, Husseini K

    2003-11-01

    A growing body of data from clinical and preclinical studies suggests that the glutamatergic system may represent a novel therapeutic target for severe recurrent mood disorders. Since synapse-specific glutamate receptor expression/localization is known to play critical roles in synaptic plasticity, we investigated the effects of mood stabilizers on AMPA receptor expression. Rats were treated chronically with lithium or valproate, hippocampal synaptosomes were isolated, and GluR1 levels were determined. Additionally, hippocampal neurons were prepared from E18 rat embryos and treated with lithium or valproate. Surface expression of GluR1 was determined using a biotinylation assay, and double-immunostaining with anti-GluR1 and anti-synaptotagmin antibodies was used to determine synaptic GluR1 levels. The AMPA receptor subunit GluR1 expression in hippocampal synaptosomes was significantly reduced by both chronic lithium and valproate. Overall, these studies show that AMPA receptor subunit GluR1 is a common target for two structurally highly dissimilar, but highly efficacious, mood stabilizers, lithium and valproate. These studies suggest that regulation of glutamatergically mediated synaptic plasticity may play a role in the treatment of mood disorders, and raise the possibility that agents more directly affecting synaptic GluR1 may represent novel therapies for this devastating illness.

  7. Plasticity in PYD assembly revealed by cryo-EM structure of the PYD filament of AIM2.

    PubMed

    Lu, Alvin; Li, Yang; Yin, Qian; Ruan, Jianbin; Yu, Xiong; Egelman, Edward; Wu, Hao

    Absent in melanoma 2 (AIM2) is an essential cytosolic double-stranded DNA receptor that assembles with the adaptor, apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC), and caspase-1 to form the AIM2 inflammasome, which leads to proteolytic maturation of cytokines and pyroptotic cell death. AIM2 contains an N-terminal Pyrin domain (PYD) that interacts with ASC through PYD/PYD interactions and nucleates ASC(PYD) filament formation. To elucidate the molecular basis of AIM2-induced ASC(PYD) polymerization, we generated AIM2(PYD) filaments fused to green fluorescent protein (GFP) and determined its cryo-electron microscopic (cryo-EM) structure. The map showed distinct definition of helices, allowing fitting of the crystal structure. Surprisingly, the GFP-AIM2(PYD) filament is a 1-start helix with helical parameters distinct from those of the 3-start ASC(PYD) filament. However, despite the apparent symmetry difference, helical net and detailed interface analyses reveal minimal changes in subunit packing. GFP-AIM2(PYD) nucleated ASC(PYD) filament formation in comparable efficiency as untagged AIM2(PYD), suggesting assembly plasticity in both AIM2(PYD) and ASC(PYD). The DNA-binding domain of AIM2 is able to form AIM2/DNA filaments, within which the AIM2(PYD) is brought into proximity to template ASC(PYD) filament assembly. Because ASC is able to interact with many PYD-containing receptors for the formation of inflammasomes, the observed structural plasticity may be critically important for this versatility in the PYD/PYD interactions.

  8. Plasticity in PYD assembly revealed by cryo-EM structure of the PYD filament of AIM2

    PubMed Central

    Lu, Alvin; Li, Yang; Yin, Qian; Ruan, Jianbin; Yu, Xiong; Egelman, Edward; Wu, Hao

    2015-01-01

    Absent in melanoma 2 (AIM2) is an essential cytosolic double-stranded DNA receptor that assembles with the adaptor, apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC), and caspase-1 to form the AIM2 inflammasome, which leads to proteolytic maturation of cytokines and pyroptotic cell death. AIM2 contains an N-terminal Pyrin domain (PYD) that interacts with ASC through PYD/PYD interactions and nucleates ASCPYD filament formation. To elucidate the molecular basis of AIM2-induced ASCPYD polymerization, we generated AIM2PYD filaments fused to green fluorescent protein (GFP) and determined its cryo-electron microscopic (cryo-EM) structure. The map showed distinct definition of helices, allowing fitting of the crystal structure. Surprisingly, the GFP-AIM2PYD filament is a 1-start helix with helical parameters distinct from those of the 3-start ASCPYD filament. However, despite the apparent symmetry difference, helical net and detailed interface analyses reveal minimal changes in subunit packing. GFP-AIM2PYD nucleated ASCPYD filament formation in comparable efficiency as untagged AIM2PYD, suggesting assembly plasticity in both AIM2PYD and ASCPYD. The DNA-binding domain of AIM2 is able to form AIM2/DNA filaments, within which the AIM2PYD is brought into proximity to template ASCPYD filament assembly. Because ASC is able to interact with many PYD-containing receptors for the formation of inflammasomes, the observed structural plasticity may be critically important for this versatility in the PYD/PYD interactions. PMID:26583071

  9. Plastic Jellyfish.

    ERIC Educational Resources Information Center

    Moseley, Christine

    2000-01-01

    Presents an environmental science activity designed to enhance students' awareness of the hazards of plastic waste for wildlife in aquatic environments. Discusses how students can take steps to reduce the effects of plastic waste. (WRM)

  10. Reduced Activity-Dependent Protein Levels in a Mouse Model of the Fragile X Premutation

    PubMed Central

    von Leden, Ramona E.; Curley, Lindsey C.; Greenberg, Gian D.; Hunsaker, Michael R.; Willemsen, Rob; Berman, Robert F.

    2014-01-01

    Environmental enrichment results in increased levels of Fmrp in brain and increased dendritic complexity. The present experiment evaluated activity-dependent increases in Fmrp levels in the motor cortex in response to training on a skilled forelimb reaching task in the CGG KI mouse model of the fragile X premutation. Fmrp, Arc, and c-Fos protein levels were quantified by Western blot in the contralateral motor cortex of mice following training to reach for sucrose pellets with a non-preferred paw and compared to levels in the ipsilateral motor cortex. After training, all mice showed increases in Fmrp, Arc, and c-Fos protein levels in the contralateral compared to the ipsilateral hemisphere; however, the increase in CGG KI mice was less than wildtype mice. Increases in Fmrp and Arc proteins scaled with learning, whereas this relationship was not observed with the c-Fos levels. These data suggest the possibility that reduced levels of activity-dependent proteins associated with synaptic plasticity such as Fmrp and Arc may contribute to the neurocognitive phenotype reported in the CGG KI mice and the fragile X premutation. PMID:24462720

  11. Reduced activity-dependent protein levels in a mouse model of the fragile X premutation.

    PubMed

    von Leden, Ramona E; Curley, Lindsey C; Greenberg, Gian D; Hunsaker, Michael R; Willemsen, Rob; Berman, Robert F

    2014-03-01

    Environmental enrichment results in increased levels of Fmrp in brain and increased dendritic complexity. The present experiment evaluated activity-dependent increases in Fmrp levels in the motor cortex in response to training on a skilled forelimb reaching task in the CGG KI mouse model of the fragile X premutation. Fmrp, Arc, and c-Fos protein levels were quantified by Western blot in the contralateral motor cortex of mice following training to reach for sucrose pellets with a non-preferred paw and compared to levels in the ipsilateral motor cortex. After training, all mice showed increases in Fmrp, Arc, and c-Fos protein levels in the contralateral compared to the ipsilateral hemisphere; however, the increase in CGG KI mice was less than wildtype mice. Increases in Fmrp and Arc proteins scaled with learning, whereas this relationship was not observed with the c-Fos levels. These data suggest the possibility that reduced levels of activity-dependent proteins associated with synaptic plasticity such as Fmrp and Arc may contribute to the neurocognitive phenotype reported in the CGG KI mice and the fragile X premutation.

  12. On the structure and strength of ultrafine-grained copper produced by severe plastic deformation

    SciTech Connect

    Gertsman, V.Y. |; Birringer, R.; Gleiter, H.; Valiev, R.Z.

    1994-01-15

    In the last few years materials with ultrafine-grained (UFG) structures having grain size in the range of nanometers or submicrometers have attracted considerable attention of researchers in various areas. However, there are still many open questions concerning the structure of UFG materials, because direct structural studies are difficult in the case of very fine grains. The behavior of submicrometer-grained materials is similar in many aspects to that of nanostructured materials. Due to the coarser grains they are more suitable for structural investigation. This paper deals with the annealing temperature dependence of the structure and room-temperature yield stress of submicrometer-grained copper.

  13. Micro-structural Evolution in Metals Subjected to Simple Shear by a Particular Severe Plastic Deformation Method

    NASA Astrophysics Data System (ADS)

    Li, Jinghui; Li, Fuguo; Li, Pan; Ma, Zhanchao; Wang, Chengpeng; Wang, Lei

    2015-08-01

    Simple shear (SS) has been considered an optimal deformation method of severe plastic deformation (SPD). To achieve SS, a particular SPD method known as mutative channel torsion extrusion (MCTE) was designed based on the geometric equivalence of SS, and the cavity parameters of a die were calculated according to strain equivalence. To investigate the characteristics of micro-structural evolution subjected to MCTE, simulated and experimental investigations were conducted. The simulated results indicate that equivalent strain distribution on the cross section is relatively uniform, and the metallographic observations confirm the simulated phenomenon. Transmission electron microscopy investigations show that the process of grain refinement undergoes the formation of shear bands, dislocation cells, dislocation forests, large-angle grain boundaries, and recrystallization nuclei. Two types of mechanisms are proposed in view of the different effects of SS on grain refinement. Eventually, MCTE is ensured as an effective method for grain refinement.

  14. Physics in Plastics Technology.

    ERIC Educational Resources Information Center

    Thomas, Ken

    1980-01-01

    Discusses the increasing role of the physicist in plastics technology. Relationships of molecular structure to material behavior, design which is related to the material, and the practical problems of fabricating a material into an article are included. (HM)

  15. Dendritic and Axonal Propagation Delays Determine Emergent Structures of Neuronal Networks with Plastic Synapses

    PubMed Central

    Madadi Asl, Mojtaba; Valizadeh, Alireza; Tass, Peter A.

    2017-01-01

    Spike-timing-dependent plasticity (STDP) modifies synaptic strengths based on the relative timing of pre- and postsynaptic spikes. The temporal order of spikes turned out to be crucial. We here take into account how propagation delays, composed of dendritic and axonal delay times, may affect the temporal order of spikes. In a minimal setting, characterized by neglecting dendritic and axonal propagation delays, STDP eliminates bidirectional connections between two coupled neurons and turns them into unidirectional connections. In this paper, however, we show that depending on the dendritic and axonal propagation delays, the temporal order of spikes at the synapses can be different from those in the cell bodies and, consequently, qualitatively different connectivity patterns emerge. In particular, we show that for a system of two coupled oscillatory neurons, bidirectional synapses can be preserved and potentiated. Intriguingly, this finding also translates to large networks of type-II phase oscillators and, hence, crucially impacts on the overall hierarchical connectivity patterns of oscillatory neuronal networks. PMID:28045109

  16. Basal tissue structure in the earliest euconodonts: Testing hypotheses of developmental plasticity in euconodont phylogeny

    USGS Publications Warehouse

    Dong, X.-P.; Donoghue, P.C.J.; Repetski, J.E.

    2005-01-01

    The hypothesis that conodonts are vertebrates rests solely on evidence of soft tissue anatomy. This has been corroborated by microstructural, topological and developmental evidence of homology between conodont and vertebrate hard tissues. However, these conclusions have been reached on the basis of evidence from highly derived euconodont taxa and the degree to which they are representative of plesiomorphic euconodonts remains an open question. Furthermore, the range of variation in tissue types comprising the euconodont basal body has been used to establish a hypothesis of developmental plasticity early in the phylogeny of the clade, and a model of diminishing potentiality in the evolution of development systems. The microstructural fabrics of the basal tissues of the earliest euconodonts (presumed to be the most plesiomorphic) are examined to test these two hypotheses. It is found that the range of microstructural variation observed hitherto was already apparent among plesiomorphic euconodonts. Thus, established histological data are representative of the most plesiomorphic euconodonts. However, although there is evidence of a range in microstructural fabrics, these are compatible with the dentine tissue system alone, and the degree of variation is compatible with that seen in clades of comparable diversity. ?? The Palaeontological Association.

  17. Dendritic and Axonal Propagation Delays Determine Emergent Structures of Neuronal Networks with Plastic Synapses.

    PubMed

    Madadi Asl, Mojtaba; Valizadeh, Alireza; Tass, Peter A

    2017-01-03

    Spike-timing-dependent plasticity (STDP) modifies synaptic strengths based on the relative timing of pre- and postsynaptic spikes. The temporal order of spikes turned out to be crucial. We here take into account how propagation delays, composed of dendritic and axonal delay times, may affect the temporal order of spikes. In a minimal setting, characterized by neglecting dendritic and axonal propagation delays, STDP eliminates bidirectional connections between two coupled neurons and turns them into unidirectional connections. In this paper, however, we show that depending on the dendritic and axonal propagation delays, the temporal order of spikes at the synapses can be different from those in the cell bodies and, consequently, qualitatively different connectivity patterns emerge. In particular, we show that for a system of two coupled oscillatory neurons, bidirectional synapses can be preserved and potentiated. Intriguingly, this finding also translates to large networks of type-II phase oscillators and, hence, crucially impacts on the overall hierarchical connectivity patterns of oscillatory neuronal networks.

  18. Alternative binding proteins: anticalins - harnessing the structural plasticity of the lipocalin ligand pocket to engineer novel binding activities.

    PubMed

    Skerra, Arne

    2008-06-01

    Antibodies are the paradigm for binding proteins, with their hypervariable loop region supported by a structurally rigid framework, thus providing the vast repertoire of antigen-binding sites in the immune system. Lipocalins are another family of proteins that exhibit a binding site with high structural plasticity, which is composed of four peptide loops mounted on a stable beta-barrel scaffold. Using site-directed random mutagenesis and selection via phage display against prescribed molecular targets, it is possible to generate artificial lipocalins with novel ligand specificities, so-called anticalins. Anticalins have been successfully selected both against small hapten-like compounds and against large protein antigens and they usually possess high target affinity and specificity. Their structural analysis has yielded interesting insights into the phenomenon of molecular recognition. Compared with antibodies, they are much smaller, have a simpler molecular architecture (comprising just one polypeptide chain) and they do not require post-translational modification. In addition, anticalins exhibit robust biophysical properties and can easily be produced in microbial expression systems. As their structure-function relationships are well understood, rational engineering of additional features such as site-directed pegylation or fusion with functional effector domains, dimerization modules or even with another anticalin, can be readily achieved. Thus, anticalins offer many applications, not only as reagents for biochemical research but also as a new class of potential drugs for medical therapy.

  19. CHARACTERIZATION OF PLASTICALLY-INDUCED STRUCTURAL CHANGES IN A Zr-BASED BULK METALLIC GLASS USING POSITRON ANNIHILATION SPECTROCOPY

    SciTech Connect

    Flores, K M; Kanungo, B P; Glade, S C; Asoka-Kumar, P

    2005-09-16

    Flow in metallic glasses is associated with stress-induced cooperative rearrangements of small groups of atoms involving the surrounding free volume. Understanding the details of these rearrangements therefore requires knowledge of the amount and distribution of the free volume and how that distribution evolves with deformation. The present study employs positron annihilation spectroscopy to investigate the free volume change in Zr{sub 58.5}Cu{sub 15.6}Ni{sub 12.8}Al{sub 10.3}Nb{sub 2.8} bulk metallic glass after inhomogeneous plastic deformation by cold rolling and structural relaxation by annealing. Results indicate that the size distribution of open volume sites is at least bimodal. The size and concentration of the larger group, identified as flow defects, changes with processing. Following initial plastic deformation the size of the flow defects increases, consistent with the free volume theory for flow. Following more extensive deformation, however, the size distribution of the positron traps shifts, with much larger open volume sites forming at the expense of the flow defects. This suggests that a critical strain is required for flow defects to coalesce and form more stable nanovoids, which have been observed elsewhere by high resolution TEM. Although these results suggest the presence of three distinct open volume size groups, further analysis indicates that all groups have the same line shape parameter. This is in contrast to the distinctly different interactions observed in crystalline materials with multiple defect types. This similarity may be due to the disordered structure of the glass and positron affinity to particular atoms surrounding open-volume regions.

  20. Plasticity of surface structures and β2-adrenergic receptor localization in failing ventricular cardiomyocytes during recovery from heart failure

    PubMed Central

    Lyon, Alexander R.; Nikolaev, Viacheslav O.; Miragoli, Michele; Sikkel, Markus B.; Paur, Helen; Benard, Ludovic; Hulot, Jean-Sebastien; Kohlbrenner, Erik; Hajjar, Roger J.; Peters, Nicholas S.; Korchev, Yuri E.; Macleod, Ken T.; Harding, Sian E.; Gorelik, Julia

    2016-01-01

    Background Cardiomyocyte surface morphology and T-tubular structure are significantly disrupted in chronic heart failure with important functional sequelae, including redistribution of sarcolemmal beta2adrenergic receptors (β2AR) and localized secondary messenger signaling. Plasticity of these changes in the reverse remodeled failing ventricle is unknown. We used AAV9.SERCA2a gene therapy to rescue failing rat hearts, and measured z-groove index, T-tubule density and compartmentalized β2AR-mediated cAMP signals using a combined nanoscale scanning ion conductance microscopy-Förster resonance energy transfer technique. Methods and Results Cardiomyocyte surface morphology, quantified by z-groove index and T-tubule density, was normalized in reverse remodeled hearts following SERCA2a gene therapy. Recovery of sarcolemmal microstructure correlated with functional β2AR redistribution back into the z-groove and T-tubular network, whereas minimal cAMP responses were initiated following local β2AR stimulation of crest membrane, as observed in failing cardiomyocytes. Improvement of β2AR localization was associated with recovery of βAR-stimulated contractile responses in rescued cardiomyocytes. Retubulation was associated with reduced spatial heterogeneity of electrically-stimulated calcium transients, and recovery of myocardial BIN-1 and TCAP protein expression, but not junctophilin-2. Conclusions In summary, abnormalities of sarcolemmal structure in heart failure show plasticity with reappearance of z-grooves and T-tubules in reverse remodeled hearts. Recovery of surface topology is necessary for normalization of β2AR location and signaling responses. PMID:22456061

  1. NF-KappaB in Long-Term Memory and Structural Plasticity in the Adult Mammalian Brain

    PubMed Central

    Kaltschmidt, Barbara; Kaltschmidt, Christian

    2015-01-01

    The transcription factor nuclear factor kappaB (NF-κB) is a well-known regulator of inflammation, stress, and immune responses as well as cell survival. In the nervous system, NF-κB is one of the crucial components in the molecular switch that converts short- to long-term memory—a process that requires de novo gene expression. Here, the researches published on NF-κB and downstream target genes in mammals will be reviewed, which are necessary for structural plasticity and long-term memory, both under normal and pathological conditions in the brain. Genetic evidence has revealed that NF-κB regulates neuroprotection, neuronal transmission, and long-term memory. In addition, after genetic ablation of all NF-κB subunits, a severe defect in hippocampal adult neurogenesis was observed during aging. Proliferation of neural precursors is increased; however, axon outgrowth, synaptogenesis, and tissue homeostasis of the dentate gyrus are hampered. In this process, the NF-κB target gene PKAcat and other downstream target genes such as Igf2 are critically involved. Therefore, NF-κB activity seems to be crucial in regulating structural plasticity and replenishment of granule cells within the hippocampus throughout the life. In addition to the function of NF-κB in neurons, we will discuss on a neuroinflammatory role of the transcription factor in glia. Finally, a model for NF-κB homeostasis on the molecular level is presented, in order to explain seemingly the contradictory, the friend or foe, role of NF-κB in the nervous system. PMID:26635522

  2. High-resolution crystal structures reveal plasticity in the metal binding site of apurinic/apyrimidinic endonuclease I.

    PubMed

    He, Hongzhen; Chen, Qiujia; Georgiadis, Millie M

    2014-10-21

    Apurinic/apyrimidinic endonuclease I (APE1) is an essential base excision repair enzyme that catalyzes a Mg²⁺-dependent reaction in which the phosphodiester backbone is cleaved 5' of an abasic site in duplex DNA. This reaction has been proposed to involve either one or two metal ions bound to the active site. In the present study, we report crystal structures of Mg²⁺, Mn²⁺, and apo-APE1 determined at 1.4, 2.2, and 1.65 Å, respectively, representing two of the highest resolution structures yet reported for APE1. In our structures, a single well-ordered Mn²⁺ ion was observed coordinated by D70 and E96; the Mg²⁺ site exhibited disorder modeled as two closely positioned sites coordinated by D70 and E96 or E96 alone. Direct metal binding analysis of wild-type, D70A, and E96A APE1, as assessed by differential scanning fluorimetry, indicated a role for D70 and E96 in binding of Mg²⁺ or Mn²⁺ to APE1. Consistent with the disorder exhibited by Mg²⁺ bound to the active site, two different conformations of E96 were observed coordinated to Mg²⁺. A third conformation for E96 in the apo structure is similar to that observed in the APE1-DNA-Mg²⁺ complex structure. Thus, binding of Mg²⁺ in three different positions within the active site of APE1 in these crystal structures corresponds directly with three different conformations of E96. Taken together, our results are consistent with the initial capture of metal by D70 and E96 and repositioning of Mg²⁺ facilitated by the structural plasticity of E96 in the active site.

  3. Taurine content in different brain structures during ageing: effect on hippocampal synaptic plasticity.

    PubMed

    Suárez, Luz M; Muñoz, María-Dolores; Martín Del Río, Rafael; Solís, José M

    2016-05-01

    A reduction in taurine content accompanies the ageing process in many tissues. In fact, the decline of brain taurine levels has been associated with cognitive deficits whereas chronic administration of taurine seems to ameliorate age-related deficits such as memory acquisition and retention. In the present study, using rats of three age groups (young, adult and aged) we determined whether the content of taurine and other amino acids (glutamate, serine, glutamine, glycine, alanine and GABA) was altered during ageing in different brain areas (cerebellum, cortex and hippocampus) as well non-brain tissues (heart, kidney, liver and plasma). Moreover, using hippocampal slices we tested whether ageing affects synaptic function and plasticity. These parameters were also determined in aged rats fed with either taurine-devoid or taurine-supplemented diets. With age, we found heterogeneous changes in amino acid content depending on the amino acid type and the tissue. In the case of taurine, its content was reduced in the cerebellum of adult and aged rats, but it remained unchanged in the hippocampus, cortex, heart and liver. The synaptic response amplitude decreased in aged rats, although the late phase of long-term synaptic potentiation (late-LTP), a taurine-dependent process, was not altered. Our study highlights the stability of taurine content in the hippocampus during ageing regardless of whether taurine was present in the diet, which is consistent with the lack of changes detected in late-LTP. These results indicate that the beneficial effects of taurine supplementation might be independent of the replenishment of taurine stores.

  4. Conformational Plasticity and Structure/Function Relationships in Cytochromes P450

    PubMed Central

    Kazanis, Sophia; Dang, Marina

    2010-01-01

    Abstract The cytochrome P450s are a superfamily of enzymes that are found in all kingdoms of living organisms, and typically catalyze the oxidative addition of atomic oxygen to an unactivated C-C or C-H bond. Over 8000 nonredundant sequences of putative and confirmed P450 enzymes have been identified, but three-dimensional structures have been determined for only a small fraction of these. While all P450 enzymes for which structures have been determined share a common global fold, the flexibility and modularity of structure around the active site account for the ability of P450 enzymes to accommodate a vast number of structurally dissimilar substrates and support a wide range of selective oxidations. In this review, known P450 structures are compared, and some structural criteria for prediction of substrate selectivity and reaction type are suggested. The importance of dynamic processes such as redox-dependent and effector-induced conformational changes in determining catalytic competence and regio- and stereoselectivity is discussed, and noncrystallographic methods for characterizing P450 structures and dynamics, in particular, mass spectrometry and nuclear magnetic resonance spectroscopy are reviewed. Antioxid. Redox Signal. 13, 1273–1296. PMID:20446763

  5. Ral mediates activity-dependent growth of postsynaptic membranes via recruitment of the exocyst

    PubMed Central

    Teodoro, Rita O; Pekkurnaz, Gulçin; Nasser, Abdullah; Higashi-Kovtun, Misao E; Balakireva, Maria; McLachlan, Ian G; Camonis, Jacques; Schwarz, Thomas L

    2013-01-01

    Remodelling neuronal connections by synaptic activity requires membrane trafficking. We present evidence for a signalling pathway by which synaptic activity and its consequent Ca2+ influx activate the small GTPase Ral and thereby recruit exocyst proteins to postsynaptic zones. In accord with the ability of the exocyst to direct delivery of post-Golgi vesicles, constitutively active Ral expressed in Drosophila muscle causes the exocyst to be concentrated in the region surrounding synaptic boutons and consequently enlarges the membrane folds of the postsynaptic plasma membrane (the subsynaptic reticulum, SSR). SSR growth requires Ral and the exocyst component Sec5 and Ral-induced enlargement of these membrane folds does not occur in sec5−/− muscles. Chronic changes in synaptic activity influence the plastic growth of this membrane in a manner consistent with activity-dependent activation of Ral. Thus, Ral regulation of the exocyst represents a control point for postsynaptic plasticity. This pathway may also function in mammals as expression of activated RalA in hippocampal neurons increases dendritic spine density in an exocyst-dependent manner and increases Sec5 in spines. PMID:23812009

  6. Modeling of Inelastic Behavior of Structures Using Plastic and Metal Laminates.

    DTIC Science & Technology

    1980-08-01

    One notes from Figure 5 that locating the concentrated reinforcement at y = d/4 appears to provide the best overall representation of the elastoplastic ...modeling into the inelastic range currently exists. The basic criteria to be satisfied when modeling an isotropic metallic structure elastoplastically ...model a mild steel parent material. This composite material was then shown to satisfy the basic criteria needed to elastoplastically model a structure

  7. Excitatory synaptic activity is associated with a rapid structural plasticity of inhibitory synapses on hippocampal CA1 pyramidal cells.

    PubMed

    Lushnikova, Irina; Skibo, Galina; Muller, Dominique; Nikonenko, Irina

    2011-04-01

    Synaptic activity, such as long-term potentiation (LTP), has been shown to induce morphological plasticity of excitatory synapses on dendritic spines through the spine head and postsynaptic density (PSD) enlargement and reorganization. Much less, however, is known about activity-induced morphological modifications of inhibitory synapses. Using an in vitro model of rat organotypic hippocampal slice cultures and electron microscopy, we studied activity-related morphological changes of somatic inhibitory inputs triggered by a brief oxygen-glucose deprivation (OGD) episode, a condition associated with a synaptic enhancement referred to as anoxic LTP and a structural remodeling of excitatory synapses. Three-dimensional reconstruction of inhibitory axo-somatic synapses at different times before and after brief OGD revealed important morphological changes. The PSD area significantly and markedly increased at synapses with large and complex PSDs, but not at synapses with simple, macular PSDs. Activity-related changes of PSD size and presynaptic bouton volume developed in a strongly correlated manner. Analyses of single and serial sections further showed that the density of inhibitory synaptic contacts on the cell soma did not change within 1 h after OGD. In contrast, the proportion of the cell surface covered with inhibitory PSDs, as well as the complexity of these PSDs significantly increased, with less macular PSDs and more complex, segmented shapes. Together, these data reveal a rapid activity-related restructuring of somatic inhibitory synapses characterized by an enlargement and increased complexity of inhibitory PSDs, providing a new mechanism for a quick adjustment of the excitatory-inhibitory balance. This article is part of a Special Issue entitled 'Synaptic Plasticity & Interneurons'.

  8. Structure and conformational plasticity of the U6 small nuclear ribonucleoprotein core.

    PubMed

    Montemayor, Eric J; Didychuk, Allison L; Liao, Honghong; Hu, Panzhou; Brow, David A; Butcher, Samuel E

    2017-01-01

    U6 small nuclear RNA (snRNA) is a key component of the active site of the spliceosome, a large ribonucleoprotein complex that catalyzes the splicing of precursor messenger RNA. Prior to its incorporation into the spliceosome, U6 is bound by the protein Prp24, which facilitates unwinding of the U6 internal stem-loop (ISL) so that it can pair with U4 snRNA. A previously reported crystal structure of the `core' of the U6 small nuclear ribonucleoprotein (snRNP) contained an ISL-stabilized A62G mutant of U6 bound to all four RNA-recognition motif (RRM) domains of Prp24 [Montemayor et al. (2014), Nature Struct. Mol. Biol. 21, 544-551]. The structure revealed a novel topology containing interlocked rings of protein and RNA that was not predicted by prior biochemical and genetic data. Here, the crystal structure of the U6 snRNP core with a wild-type ISL is reported. This complex crystallized in a new space group, apparently owing in part to the presence of an intramolecular cross-link in RRM1 that was not observed in the previously reported U6-A62G structure. The structure exhibits the same protein-RNA interface and maintains the unique interlocked topology. However, the orientation of the wild-type ISL is altered relative to the A62G mutant structure, suggesting inherent structural dynamics that may facilitate its pairing with U4. Consistent with their similar architectures in the crystalline state, the wild-type and A62G variants of U6 exhibit similar Prp24-binding affinities and electrophoretic mobilities when analyzed by gel-shift assay.

  9. Activity-Dependent Bidirectional Regulation of GAD Expression in a Homeostatic Fashion Is Mediated by BDNF-Dependent and Independent Pathways.

    PubMed

    Hanno-Iijima, Yoko; Tanaka, Masami; Iijima, Takatoshi

    2015-01-01

    Homeostatic synaptic plasticity, or synaptic scaling, is a mechanism that tunes neuronal transmission to compensate for prolonged, excessive changes in neuronal activity. Both excitatory and inhibitory neurons undergo homeostatic changes based on synaptic transmission strength, which could effectively contribute to a fine-tuning of circuit activity. However, gene regulation that underlies homeostatic synaptic plasticity in GABAergic (GABA, gamma aminobutyric) neurons is still poorly understood. The present study demonstrated activity-dependent dynamic scaling in which NMDA-R (N-methyl-D-aspartic acid receptor) activity regulated the expression of GABA synthetic enzymes: glutamic acid decarboxylase 65 and 67 (GAD65 and GAD67). Results revealed that activity-regulated BDNF (brain-derived neurotrophic factor) release is necessary, but not sufficient, for activity-dependent up-scaling of these GAD isoforms. Bidirectional forms of activity-dependent GAD expression require both BDNF-dependent and BDNF-independent pathways, both triggered by NMDA-R activity. Additional results indicated that these two GAD genes differ in their responsiveness to chronic changes in neuronal activity, which could be partially caused by differential dependence on BDNF. In parallel to activity-dependent bidirectional scaling in GAD expression, the present study further observed that a chronic change in neuronal activity leads to an alteration in neurotransmitter release from GABAergic neurons in a homeostatic, bidirectional fashion. Therefore, the differential expression of GAD65 and 67 during prolonged changes in neuronal activity may be implicated in some aspects of bidirectional homeostatic plasticity within mature GABAergic presynapses.

  10. Evaluation of three types of structured floating plastic media in moving bed biofilters for total ammonia nitrogen removal in a low salinity hatchery recirculating aquaculture system

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Three different commercially available structural plastic media were evaluated in triplicate in moving bed toriod filters under low salinity (11-12 ppt) warm water culture conditions and two different feed loading rates. The culture system consisted of nine separate modules that include a double dra...

  11. A QSPR for the plasticization efficiency of polyvinylchloride plasticizers.

    PubMed

    Chandola, Mridula; Marathe, Sujata

    2008-01-01

    A simple quantitative structure property relationship (QSPR) for correlating the plasticization efficiency of 25 polyvinylchloride (PVC) plasticizers was obtained using molecular modeling. The plasticizers studied were-aromatic esters (phthalate, terephthalate, benzoate, trimellitate), aliphatic esters (adipate, sebacate, azelate), citrates and a phosphate. The low temperature flex point, Tf, of plasticized polyvinylchloride resins was considered as an indicator of plasticization efficiency. Initially, we attempted to predict plasticization efficiency of PVC plasticizers from physical and structural descriptors derived from the plasticizer molecule alone. However, the correlation of these descriptors with Tf was not very good with R=0.78 and r2=0.613. This implied that the selected descriptors were unable to predict all the interactions between PVC and plasticizer. Hence, to account for these interactions, a model containing two polyvinylchloride (PVC) chain segments along with a plasticizer molecule in a simulation box was constructed, using molecular mechanics. A good QSPR equation correlating physical and structural descriptors derived from the model to Tf of the plasticized resins was obtained with R=0.954 and r2=0.909.

  12. Survey of long-term durability of fiberglass reinforced plastic structures

    NASA Technical Reports Server (NTRS)

    Lieblein, S.

    1981-01-01

    Included are fluid containment vessels, marine structures, and aircraft components with up to 19 years of service. Correlations were obtained for the variation of static fatigue strength, cyclic fatigue strength, and residual burst strength for pressure vessels. In addition, data are presented for the effects of moisture on strength retention. Data variations were analyzed, and relationships and implications for testing are discussed. Change in strength properties for complete structures was examined for indications of the effects of environmental conditions such as moisture and outdoor exposure (ultraviolet radiation, weathering) on long term durability.

  13. Re-evaluation of all-plastic organic dye laser with DFB structure fabricated using photoresists

    PubMed Central

    Tsutsumi, Naoto; Nagi, Saori; Kinashi, Kenji; Sakai, Wataru

    2016-01-01

    Organic solid-state lasers (OSSLs) with distributed feedback structures can detect nanoscale materials and therefore offer an attractive sensing platform for biological and medical applications. Here we investigate the lasing characteristics, i.e., the threshold and slope efficiency, as a function of the grating depth in OSSL devices with distributed feedback (DFB) structure fabricated using photoresists. Two types of photoresists were used for the DFB structures: a negative photoresist, SU-8 2002, and a positive photoresist, ma-P 1275. The DFB structure was fabricated using a Lloyd-mirror configuration. The active layer was a rhodamine 6G-doped cellulose acetate waveguide. The threshold for the first order mode (m  = 1) was lower than that for the second and third order modes (m = 2, and 3). A low threshold of 27 μJ cm−2 pulse−1 (58 nJ) was obtained using SU-8 2002, with m = 1. The slope efficiency was evaluated as a function of grating depth for each mode and increased as the grating depth increased. PMID:27703217

  14. Re-evaluation of all-plastic organic dye laser with DFB structure fabricated using photoresists

    NASA Astrophysics Data System (ADS)

    Tsutsumi, Naoto; Nagi, Saori; Kinashi, Kenji; Sakai, Wataru

    2016-10-01

    Organic solid-state lasers (OSSLs) with distributed feedback structures can detect nanoscale materials and therefore offer an attractive sensing platform for biological and medical applications. Here we investigate the lasing characteristics, i.e., the threshold and slope efficiency, as a function of the grating depth in OSSL devices with distributed feedback (DFB) structure fabricated using photoresists. Two types of photoresists were used for the DFB structures: a negative photoresist, SU-8 2002, and a positive photoresist, ma-P 1275. The DFB structure was fabricated using a Lloyd-mirror configuration. The active layer was a rhodamine 6G-doped cellulose acetate waveguide. The threshold for the first order mode (m  = 1) was lower than that for the second and third order modes (m = 2, and 3). A low threshold of 27 μJ cm‑2 pulse‑1 (58 nJ) was obtained using SU-8 2002, with m = 1. The slope efficiency was evaluated as a function of grating depth for each mode and increased as the grating depth increased.

  15. The Structural Plasticity of White Matter Networks Following Anterior Temporal Lobe Resection

    ERIC Educational Resources Information Center

    Yogarajah, Mahinda; Focke, Niels K.; Bonelli, Silvia B.; Thompson, Pamela; Vollmar, Christian; McEvoy, Andrew W.; Alexander, Daniel C.; Symms, Mark R.; Koepp, Matthias J.; Duncan, John S.

    2010-01-01

    Anterior temporal lobe resection is an effective treatment for refractory temporal lobe epilepsy. The structural consequences of such surgery in the white matter, and how these relate to language function after surgery remain unknown. We carried out a longitudinal study with diffusion tensor imaging in 26 left and 20 right temporal lobe epilepsy…

  16. Multiscale Analysis of Structurally-Graded Microstructures Using Molecular Dynamics, Discrete Dislocation Dynamics and Continuum Crystal Plasticity

    NASA Technical Reports Server (NTRS)

    Saether, Erik; Hochhalter, Jacob D.; Glaessgen, Edward H.; Mishin, Yuri

    2014-01-01

    A multiscale modeling methodology is developed for structurally-graded material microstructures. Molecular dynamic (MD) simulations are performed at the nanoscale to determine fundamental failure mechanisms and quantify material constitutive parameters. These parameters are used to calibrate material processes at the mesoscale using discrete dislocation dynamics (DD). Different grain boundary interactions with dislocations are analyzed using DD to predict grain-size dependent stress-strain behavior. These relationships are mapped into crystal plasticity (CP) parameters to develop a computationally efficient finite element-based DD/CP model for continuum-level simulations and complete the multiscale analysis by predicting the behavior of macroscopic physical specimens. The present analysis is focused on simulating the behavior of a graded microstructure in which grain sizes are on the order of nanometers in the exterior region and transition to larger, multi-micron size in the interior domain. This microstructural configuration has been shown to offer improved mechanical properties over homogeneous coarse-grained materials by increasing yield stress while maintaining ductility. Various mesoscopic polycrystal models of structurally-graded microstructures are generated, analyzed and used as a benchmark for comparison between multiscale DD/CP model and DD predictions. A final series of simulations utilize the DD/CP analysis method exclusively to study macroscopic models that cannot be analyzed by MD or DD methods alone due to the model size.

  17. Structural plasticity in hippocampal cells related to the facilitative effect of intracranial self-stimulation on a spatial memory task.

    PubMed

    Chamorro-López, Jacobo; Miguéns, Miguel; Morgado-Bernal, Ignacio; Kastanauskaite, Asta; Selvas, Abraham; Cabané-Cucurella, Alberto; Aldavert-Vera, Laura; DeFelipe, Javier; Segura-Torres, Pilar

    2015-12-01

    Posttraining intracranial self-stimulation (SS) in the lateral hypothalamus facilitates the acquisition and retention of several implicit and explicit memory tasks. Here, intracellular injections of Lucifer yellow were used to assess morphological changes in hippocampal neurons that might be specifically related to the facilitative posttraining SS effect upon the acquisition and retention of a distributed spatial task in the Morris water maze. We examined the structure, size and branching complexity of cornus ammonis 1 (CA1) cells, and the spine density of CA1 pyramidal neurons and granular cells of the dentate gyrus (DG). Animals that received SS after each acquisition session performed faster and better than Sham ones--an improvement that was also evident in a probe trial 3 days after the last training session. The neuromorphological analysis revealed an increment in the size and branching complexity in apical CA1 dendritic arborization in SS-treated subjects as compared with Sham animals. Furthermore, increased spine density was observed in the CA1 field in SS animals, whereas no effects were observed in DG cells. Our results support the hypothesis that the facilitating effect of SS on the acquisition and retention of a spatial memory task could be related to structural plasticity in CA1 hippocampal cells.

  18. Structural plasticity and in vivo activity of Cas1 from the type I-F CRISPR-Cas system.

    PubMed

    Wilkinson, Max E; Nakatani, Yoshio; Staals, Raymond H J; Kieper, Sebastian N; Opel-Reading, Helen K; McKenzie, Rebecca E; Fineran, Peter C; Krause, Kurt L

    2016-04-15

    CRISPR-Cas systems are adaptive immune systems in prokaryotes that provide protection against viruses and other foreign DNA. In the adaptation stage, foreign DNA is integrated into CRISPR (clustered regularly interspaced short palindromic repeat) arrays as new spacers. These spacers are used in the interference stage to guide effector CRISPR associated (Cas) protein(s) to target complementary foreign invading DNA. Cas1 is the integrase enzyme that is central to the catalysis of spacer integration. There are many diverse types of CRISPR-Cas systems, including type I-F systems, which are typified by a unique Cas1-Cas2-3 adaptation complex. In the present study we characterize the Cas1 protein of the potato phytopathogen Pectobacterium atrosepticum, an important model organism for understanding spacer acquisition in type I-F CRISPR-Cas systems. We demonstrate by mutagenesis that Cas1 is essential for adaptation in vivo and requires a conserved aspartic acid residue. By X-ray crystallography, we show that although P. atrosepticum Cas1 adopts a fold conserved among other Cas1 proteins, it possesses remarkable asymmetry as a result of structural plasticity. In particular, we resolve for the first time a flexible, asymmetric loop that may be unique to type I-F Cas1 proteins, and we discuss the implications of these structural features for DNA binding and enzymatic activity.

  19. The long-term structural plasticity of cerebellar parallel fiber axons and its modulation by motor learning.

    PubMed

    Carrillo, Jennifer; Cheng, Shao-Ying; Ko, Kwang Woo; Jones, Theresa A; Nishiyama, Hiroshi

    2013-05-08

    Presynaptic axonal varicosities, like postsynaptic spines, are dynamically added and eliminated even in mature neuronal circuitry. To study the role of this axonal structural plasticity in behavioral learning, we performed two-photon in vivo imaging of cerebellar parallel fibers (PFs) in adult mice. PFs make excitatory synapses on Purkinje cells (PCs) in the cerebellar cortex, and long-term potentiation and depression at PF-PC synapses are thought to play crucial roles in cerebellar-dependent learning. Time-lapse vital imaging of PFs revealed that, under a control condition (no behavioral training), ∼10% of PF varicosities appeared and disappeared over a period of 2 weeks without changing the total number of varicosities. The fraction of dynamic PF varicosities significantly diminished during training on an acrobatic motor skill learning task, largely because of reduced addition of new varicosities. Thus, this form of motor learning was associated with greater structural stability of PFs and a slight decrease in the total number of varicosities. Together with prior findings that the number of PF-PC synapses increases during similar training, our results suggest that acrobatic motor skill learning involves a reduction of some PF inputs and a strengthening of others, probably via the conversion of some preexisting PF varicosities into multisynaptic terminals.

  20. CaMKII requirement for the persistence of in vivo hippocampal mossy fiber synaptic plasticity and structural reorganization.

    PubMed

    Juárez-Muñoz, Yectivani; Rivera-Olvera, Alejandro; Ramos-Languren, Laura E; Escobar, Martha L

    2017-03-01

    CaMKII has been proposed as a molecular substrate for long-term memory storage due to its capacity to maintain an active autophosporylated state even after the decay of the external stimuli. The hippocampal mossy fiber-CA3 pathway (MF-CA3) is considered as a relevant area for acquisition and storage of different learning tasks. MF-CA3 pathway exhibits a form of LTP characterized by a slow initial increase in the EPSP slope that is independent of NMDA receptors activation. Our previous studies show that application of high frequency stimulation sufficient to elicit MF-CA3 LTP produces structural reorganization, in a manner independent of LTP induction, at the stratum oriens of hippocampal CA3 area 7days after stimulation. However, the molecular mechanisms that underlie the maintenance of MF-CA3 LTP as well as the concomitant structural reorganization in this area remain to be elucidated. Here we show that acute microinfusion of myr-CaMKIINtide, a noncompetitive inhibitor of CaMKII, in the hippocampal CA3 area of adult rats during the late-phase of in vivo MF-CA3 LTP blocked its maintenance and prevented the accompanying morphological reorganization in CA3 area. These findings support the idea that CaMKII is a key molecular substrate for the long-term hippocampal synaptic plasticity maintenance.

  1. Mild Thyroid Hormone Insufficiency During Development Compromises Activity-Dependent Neuroplasticity in the Hippocampus of Adult Male Rats

    EPA Pesticide Factsheets

    behavioral measures of learning and memory in adult offspring of rats treated with thyroid hormone synthesis inhibitor, propylthiouracil.Electrophysiological measures of 'memory' in form of plasticity model known as long term potentiation (LTP)Molecular changes induced by LTPThis dataset is associated with the following publication:Gilbert , M., K. Sanchez-Huerta, and C. Wood. Mild Thyroid Hormone Insufficiency During Development Compromises Activity-Dependent Neuroplasticity in the Hippocampus of Adult Make Rats. ENDOCRINOLOGY. Endocrine Society, 157(2): 774-87, (2016).

  2. PLPP/CIN regulates bidirectional synaptic plasticity via GluN2A interaction with postsynaptic proteins

    PubMed Central

    Kim, Ji-Eun; Kim, Yeon-Joo; Lee, Duk-Shin; Kim, Ji Yang; Ko, Ah-Reum; Hyun, Hye-Won; Kim, Min Ju; Kang, Tae-Cheon

    2016-01-01

    Dendritic spines are dynamic structures whose efficacies and morphologies are modulated by activity-dependent synaptic plasticity. The actin cytoskeleton plays an important role in stabilization and structural modification of spines. However, the regulatory mechanism by which it alters the plasticity threshold remains elusive. Here, we demonstrate the role of pyridoxal-5′-phosphate phosphatase/chronophin (PLPP/CIN), one of the cofilin-mediated F-actin regulators, in modulating synaptic plasticity in vivo. PLPP/CIN transgenic (Tg) mice had immature spines with small heads, while PLPP/CIN knockout (KO) mice had gigantic spines. Furthermore, PLPP/CIN Tg mice exhibited enhanced synaptic plasticity, but KO mice showed abnormal synaptic plasticity. The PLPP/CIN-induced alterations in synaptic plasticity were consistent with the acquisition and the recall capacity of spatial learning. PLPP/CIN also enhanced N-methyl-D-aspartate receptor (GluN) functionality by regulating the coupling of GluN2A with interacting proteins, particularly postsynaptic density-95 (PSD95). Therefore, these results suggest that PLPP/CIN may be an important factor for regulating the plasticity threshold. PMID:27212638

  3. Nitric oxide mediates local activity-dependent excitatory synapse development.

    PubMed

    Nikonenko, Irina; Nikonenko, Alexander; Mendez, Pablo; Michurina, Tatyana V; Enikolopov, Grigori; Muller, Dominique

    2013-10-29

    Learning related paradigms play an important role in shaping the development and specificity of synaptic networks, notably by regulating mechanisms of spine growth and pruning. The molecular events underlying these synaptic rearrangements remain poorly understood. Here we identify NO signaling as a key mediator of activity-dependent excitatory synapse development. We find that chronic blockade of NO production in vitro and in vivo interferes with the development of hippocampal and cortical excitatory spine synapses. The effect results from a selective loss of activity-mediated spine growth mechanisms and is associated with morphological and functional alterations of remaining synapses. These effects of NO are mediated by a cGMP cascade and can be reproduced or prevented by postsynaptic expression of vasodilator-stimulated phosphoprotein phospho-mimetic or phospho-resistant mutants. In vivo analyses show that absence of NO prevents the increase in excitatory synapse density induced by environmental enrichment and interferes with the formation of local clusters of excitatory synapses. We conclude that NO plays an important role in regulating the development of excitatory synapses by promoting local activity-dependent spine-growth mechanisms.

  4. A network model for activity-dependent sleep regulation.

    PubMed

    Roy, Sandip; Krueger, James M; Rector, David M; Wan, Yan

    2008-08-07

    We develop and characterize a dynamical network model for activity-dependent sleep regulation. Specifically, in accordance with the activity-dependent theory for sleep, we view organism sleep as emerging from the local sleep states of functional units known as cortical columns; these local sleep states evolve through integration of local activity inputs, loose couplings with neighboring cortical columns, and global regulation (e.g. by the circadian clock). We model these cortical columns as coupled or networked activity-integrators that transition between sleep and waking states based on thresholds on the total activity. The model dynamics for three canonical experiments (which we have studied both through simulation and system-theoretic analysis) match with experimentally observed characteristics of the cortical-column network. Most notably, assuming connectedness of the network graph, our model predicts the recovery of the columns to a synchronized state upon temporary overstimulation of a single column and/or randomization of the initial sleep and activity-integration states. In analogy with other models for networked oscillators, our model also predicts the possibility for such phenomena as mode-locking.

  5. [Structural-metabolic plasticity of mammalian skeletal muscles in hypokinesis and weightlessness].

    PubMed

    Shenkman, B S

    2002-01-01

    Under review are investigations of the contractile structure of skeletal muscles of humans and animals (rats and primates) following space flight, long-term hypokinesia, immersion (human subjects) and head-down suspension (rats). Close consideration is given to experimental testing of hypotheses concerning neuronal, humoral and cell processes leading to atrophy. Described are consistencies and mechanisms of changes in the myosin phenotype and electromechanic coupling in muscular fibers as well as their capillarization and energy potential.

  6. Structural plasticity in the human cytosolic sulfotransferase dimer and its role in substrate selectivity and catalysis.

    PubMed

    Tibbs, Zachary E; Rohn-Glowacki, Katie Jo; Crittenden, Frank; Guidry, Amber L; Falany, Charles N

    2015-02-01

    The cytosolic sulfotransferases (SULTs) are dimeric enzymes that help maintain homeostasis through the modulation of hormone and drug activity by catalyzing their transformation into hydrophilic sulfate esters and increasing their excretion. Each of the thirteen active human SULT isoforms displays a unique substrate specificity pattern that underlies its individual role in our bodies. These specificities have proven to be complex, in some cases masking the biological role of specific isoforms. The first part of this review offers a short summary of historical underpinnings of human SULTs, primarily centered on the characterization of each isoform's kinetic and structural properties. Recent structural investigations have revealed each SULT has an active site "lid" that undergoes restructuring once the cofactor/sulfonate donor, 3'-phosphoadenosine-5'-phosphosulfate (PAPS), binds to the enzyme. This structural rearrangement can alter substrate-binding profiles, therefore complicating enzyme/substrate interactions and making substrate/cosubstrate concentrations and binding order important considerations in enzyme functionality. Molecular dynamic simulations have recently been employed to describe this restructuring in an attempt to offer insight to its effects on substrate selectivity. In addition to reviewing new data on SULT molecular dynamics, we will discuss the contribution of PAPS concentrations and SULT dimerization in the regulation of SULT activity within the human body.

  7. Structural Plasticity of the Phage P22 Tail Needle gp26 Probed with Xenon Gas

    SciTech Connect

    Olia, A.; Casjens, S; Cingolani, G

    2009-01-01

    The tail needle, gp26, is a highly stable homo-trimeric fiber found in the tail apparatus of bacteriophage P22. In the mature virion, gp26 is responsible for plugging the DNA exit channel, and likely plays an important role in penetrating the host cell envelope. In this article, we have determined the 1.98 A resolution crystal structure of gp26 bound to xenon gas. The structure led us to identify a calcium and a chloride ion intimately bound at the interior of alpha-helical core, as well as seven small cavities occupied by xenon atoms. The two ions engage in buried polar interactions with gp26 side chains that provide specificity and register to gp26 helical core, thus enhancing its stability. Conversely, the distribution of xenon accessible cavities correlates well with the flexibility of the fiber observed in solution and in the crystal structure. We suggest that small internal cavities in gp26 between the helical core and the C-terminal tip allow for flexible swinging of the latter, without affecting the overall stability of the protein. The C-terminal tip may be important in scanning the bacterial surface in search of a cell-envelope penetration site, or for recognition of a yet unidentified receptor on the surface of the host.

  8. Structural Plasticity in Globins: Role of Protein Dynamics in Defining Ligand Migration Pathways.

    PubMed

    Estarellas, C; Capece, L; Seira, C; Bidon-Chanal, A; Estrin, D A; Luque, F J

    2016-01-01

    Globins are a family of proteins characterized by the presence of the heme prosthetic group and involved in variety of biological functions in the cell. Due to their biological relevance and widespread distribution in all kingdoms of life, intense research efforts have been devoted to disclosing the relationships between structural features, protein dynamics, and function. Particular attention has been paid to the impact of differences in amino acid sequence on the topological features of docking sites and cavities and to the influence of conformational flexibility in facilitating the migration of small ligands through these cavities. Often, tunnels are carved in the interior of globins, and ligand exchange is regulated by gating residues. Understanding the subtle intricacies that relate the differences in sequence with the structural and dynamical features of globins with the ultimate aim of rationalizing the thermodynamics and kinetics of ligand binding continues to be a major challenge in the field. Due to the evolution of computational techniques, significant advances into our understanding of these questions have been made. In this review we focus our attention on the analysis of the ligand migration pathways as well as the function of the structural cavities and tunnels in a series of representative globins, emphasizing the synergy between experimental and theoretical approaches to gain a comprehensive knowledge into the molecular mechanisms of this diverse family of proteins.

  9. Nonisothermal elasto-visco-plastic response of shell-type structures

    NASA Technical Reports Server (NTRS)

    Simitses, G. J.; Carlson, R. L.; Riff, R.

    1987-01-01

    A mathematical model and solution methodologies for analyzing structural response of thin, metallic shell-type structures under large transient, cyclic or static thermomechanical loads is disussed. Among the system responses, which are associated with these load conditions, are thermal buckling and creep buckling. Thus, geometric as well as material-type nonlinearities (of high order) can be anticipated and have been considered in the development of the mathematical model. Furthermore, this was accommodated in the solution procedures. A complete true ab-inito rate theory of kinematics and kinetics for continuum and curved thin structures, without any restriction on the magnitude of the strains or the deformation, was formulated. The time dependence and large strain behavior are incorporated through the introduction of the time rates of the metric and curvature in two coordinate systems, a fixed (spatial) one and a convected (material) coordinate system. The relations between the time derivative and the covariant derivatives (gradients) have been developed for curved space and motion, so that the velocity components supply the connection between the equations of motion and the time rate of change of the metric and curvature tensors.

  10. Structural plasticity of PAM recognition by engineered variants of the RNA-guided endonuclease Cas9

    PubMed Central

    Anders, Carolin; Bargsten, Katja; Jinek, Martin

    2016-01-01

    Summary The RNA-guided endonuclease Cas9 from Streptococcus pyogenes (SpCas9) forms the core of a powerful genome editing technology. DNA cleavage by SpCas9 is dependent on the presence of a 5’-NGG-3’ protospacer adjacent motif (PAM) in the target DNA, restricting the choice of targetable sequences. To address this limitation, artificial SpCas9 variants with altered PAM specificities have recently been developed. Here we report crystal structures of the VQR, EQR, and VRER SpCas9 variants bound to target DNAs containing their preferred PAM sequences. The structures reveal that the non-canonical PAMs are recognized by an induced fit mechanism. Besides mediating sequence-specific base recognition, the amino acid substitutions introduced in the SpCas9 variants facilitate conformational remodeling of the PAM region of the bound DNA. Guided by the structural data, we developed a SpCas9 variant that specifically recognizes NAAG PAMs. Taken together, these studies inform further development of Cas9-based genome editing tools. PMID:26990992

  11. Structural and functional plasticity specific to musical training with wind instruments.

    PubMed

    Choi, Uk-Su; Sung, Yul-Wan; Hong, Sujin; Chung, Jun-Young; Ogawa, Seiji

    2015-01-01

    Numerous neuroimaging studies have shown structural and functional changes resulting from musical training. Among these studies, changes in primary sensory areas are mostly related to motor functions. In this study, we looked for some similar functional and structural changes in other functional modalities, such as somatosensory function, by examining the effects of musical training with wind instruments. We found significant changes in two aspects of neuroplasticity, cortical thickness, and resting-state neuronal networks. A group of subjects with several years of continuous musical training and who are currently playing in university wind ensembles showed differences in cortical thickness in lip- and tongue-related brain areas vs. non-music playing subjects. Cortical thickness in lip-related brain areas was significantly thicker and that in tongue-related areas was significantly thinner in the music playing group compared with that in the non-music playing group. Association analysis of lip-related areas in the music playing group showed that the increase in cortical thickness was caused by musical training. In addition, seed-based correlation analysis showed differential activation in the precentral gyrus and supplementary motor areas (SMA) between the music and non-music playing groups. These results suggest that high-intensity training with specific musical instruments could induce structural changes in related anatomical areas and could also generate a new functional neuronal network in the brain.

  12. Structural and functional plasticity specific to musical training with wind instruments

    PubMed Central

    Choi, Uk-Su; Sung, Yul-Wan; Hong, Sujin; Chung, Jun-Young; Ogawa, Seiji

    2015-01-01

    Numerous neuroimaging studies have shown structural and functional changes resulting from musical training. Among these studies, changes in primary sensory areas are mostly related to motor functions. In this study, we looked for some similar functional and structural changes in other functional modalities, such as somatosensory function, by examining the effects of musical training with wind instruments. We found significant changes in two aspects of neuroplasticity, cortical thickness, and resting-state neuronal networks. A group of subjects with several years of continuous musical training and who are currently playing in university wind ensembles showed differences in cortical thickness in lip- and tongue-related brain areas vs. non-music playing subjects. Cortical thickness in lip-related brain areas was significantly thicker and that in tongue-related areas was significantly thinner in the music playing group compared with that in the non-music playing group. Association analysis of lip-related areas in the music playing group showed that the increase in cortical thickness was caused by musical training. In addition, seed-based correlation analysis showed differential activation in the precentral gyrus and supplementary motor areas (SMA) between the music and non-music playing groups. These results suggest that high-intensity training with specific musical instruments could induce structural changes in related anatomical areas and could also generate a new functional neuronal network in the brain. PMID:26578939

  13. Dynamic response of Cu4Zr54 metallic glass to high strain rate shock loading: plasticity, spall and atomic-level structures

    SciTech Connect

    Luo, Shengnian; Arman, Bedri; Germann, Timothy C; Cagin, Tahir

    2009-01-01

    We investigate dynamic response of Cu{sub 46}Zr{sub 54} metallic glass under adiabatic planar shock wave loading (one-dimensional strain) wjth molecular dynamics simulations, including Hugoniot (shock) states, shock-induced plasticity and spallation. The Hugoniot states are obtained up to 60 CPa along with the von Mises shear flow strengths, and the dynamic spall strength, at different strain rates and temperatures. The spall strengths likely represent the limiting values achievable in experiments such as laser ablation. For the steady shock states, a clear elastic-plastic transition is identified (e.g., in the shock velocity-particle velocity curve), and the shear strength shows strain-softening. However, the elastic-plastic transition across the shock front displays transient stress overshoot (hardening) above the Hugoniot elastic limit followed by a relatively sluggish relaxation to the steady shock state, and the plastic shock front steepens with increasing shock strength. The local von Mises shear strain analysis is used to characterize local deformation, and the Voronoi tessellation analysis, the corresponding short-range structures at various stages of shock, release, tension and spallation. The plasticity in this glass is manifested as localized shear transformation zones and of local structure rather than thermal origin, and void nucleation occurs preferentially at the highly shear-deformed regions. The Voronoi and shear strain analyses show that the atoms with different local structures are of different shear resistances that lead to shear localization (e.g., the atoms indexed with (0,0,12,0) are most shear-resistant, and those with (0,2,8,1) are highly prone to shear flow). The dynamic changes in local structures are consistent with the observed deformation dynamics.

  14. Spatial organization of plastic deformation in single crystals with different structure of slip dislocation

    SciTech Connect

    Kunitsyna, T. S.; Teplyakova, L. A. Koneva, N. A.; Poltaranin, M. A.

    2015-10-27

    It is established that different structure of slip dislocation at the end of the linear hardening stage results in different distribution of dislocation charges in the volume of a single crystal. In the alloy with a near atomic order the slip of single dislocations leads to formation of planar structures—layers with the excess density of dislocations. In the alloy with long-range atomic order the slip of superdislocations brings the formation of the system of parallel rod-like charged dislocation linking.

  15. Hierarchical fiber-optic delamination detection system for carbon fiber reinforced plastic structures

    NASA Astrophysics Data System (ADS)

    Minakuchi, Shu; Banshoya, Hidehiko; Shingo, Ii; Takeda, Nobuo

    2012-10-01

    This study develops a delamination detection system by extending our previous approach for monitoring surface cracks in a large-scale composite structure. In the new system, numerous thin glass capillaries are embedded into a composite structure, and internal pressure in the built-in capillary sensors, based on comparative vacuum monitoring (CVM), is maintained as a vacuum. When delamination is induced, the capillary sensors located within the delaminated area are breached, and atmospheric air flows into the capillaries. The consequent pressure change within the capillaries is then converted into axial strain in a surface-mounted optical fiber through a transducing mechanism, which is connected to the capillaries. By monitoring the strain distribution along the optical fiber, it is possible to identify a transducing mechanism in which the pressure change occurred and thus to specify the location of the delamination. This study begins by establishing a novel sensor embedding/extracting method. The airflow characteristic in the capillary sensors is then comprehensively evaluated, determining the basic performance of the new system. The proposed detection technique is validated by taking a step-by-step approach, and finally the hierarchical fiber-optic delamination detection system is demonstrated. A further advance to be combined with a self-healing concept is also discussed.

  16. Plastics Technology.

    ERIC Educational Resources Information Center

    Barker, Tommy G.

    This curriculum guide is designed to assist junior high schools industrial arts teachers in planning new courses and revising existing courses in plastics technology. Addressed in the individual units of the guide are the following topics: introduction to production technology; history and development of plastics; safety; youth leadership,…

  17. The structural plasticity of white matter networks following anterior temporal lobe resection

    PubMed Central

    Yogarajah, Mahinda; Focke, Niels K.; Bonelli, Silvia B.; Thompson, Pamela; Vollmar, Christian; McEvoy, Andrew W.; Alexander, Daniel C.; Symms, Mark R.; Koepp, Matthias J.

    2010-01-01

    Anterior temporal lobe resection is an effective treatment for refractory temporal lobe epilepsy. The structural consequences of such surgery in the white matter, and how these relate to language function after surgery remain unknown. We carried out a longitudinal study with diffusion tensor imaging in 26 left and 20 right temporal lobe epilepsy patients before and a mean of 4.5 months after anterior temporal lobe resection. The whole-brain analysis technique tract-based spatial statistics was used to compare pre- and postoperative data in the left and right temporal lobe epilepsy groups separately. We observed widespread, significant, mean 7%, decreases in fractional anisotropy in white matter networks connected to the area of resection, following both left and right temporal lobe resections. However, we also observed a widespread, mean 8%, increase in fractional anisotropy after left anterior temporal lobe resection in the ipsilateral external capsule and posterior limb of the internal capsule, and corona radiata. These findings were confirmed on analysis of the native clusters and hand drawn regions of interest. Postoperative tractography seeded from this area suggests that this cluster is part of the ventro-medial language network. The mean pre- and postoperative fractional anisotropy and parallel diffusivity in this cluster were significantly correlated with postoperative verbal fluency and naming test scores. In addition, the percentage change in parallel diffusivity in this cluster was correlated with the percentage change in verbal fluency after anterior temporal lobe resection, such that the bigger the increase in parallel diffusivity, the smaller the fall in language proficiency after surgery. We suggest that the findings of increased fractional anisotropy in this ventro-medial language network represent structural reorganization in response to the anterior temporal lobe resection, which may damage the more susceptible dorso-lateral language pathway

  18. Playing Super Mario induces structural brain plasticity: gray matter changes resulting from training with a commercial video game.

    PubMed

    Kühn, S; Gleich, T; Lorenz, R C; Lindenberger, U; Gallinat, J

    2014-02-01

    Video gaming is a highly pervasive activity, providing a multitude of complex cognitive and motor demands. Gaming can be seen as an intense training of several skills. Associated cerebral structural plasticity induced has not been investigated so far. Comparing a control with a video gaming training group that was trained for 2 months for at least 30 min per day with a platformer game, we found significant gray matter (GM) increase in right hippocampal formation (HC), right dorsolateral prefrontal cortex (DLPFC) and bilateral cerebellum in the training group. The HC increase correlated with changes from egocentric to allocentric navigation strategy. GM increases in HC and DLPFC correlated with participants' desire for video gaming, evidence suggesting a predictive role of desire in volume change. Video game training augments GM in brain areas crucial for spatial navigation, strategic planning, working memory and motor performance going along with evidence for behavioral changes of navigation strategy. The presented video game training could therefore be used to counteract known risk factors for mental disease such as smaller hippocampus and prefrontal cortex volume in, for example, post-traumatic stress disorder, schizophrenia and neurodegenerative disease.

  19. Receptor protein tyrosine phosphatase sigma regulates synapse structure, function and plasticity.

    PubMed

    Horn, Katherine E; Xu, Bin; Gobert, Delphine; Hamam, Bassam N; Thompson, Katherine M; Wu, Chia-Lun; Bouchard, Jean-François; Uetani, Noriko; Racine, Ronald J; Tremblay, Michel L; Ruthazer, Edward S; Chapman, C Andrew; Kennedy, Timothy E

    2012-07-01

    The mechanisms that regulate synapse formation and maintenance are incompletely understood. In particular, relatively few inhibitors of synapse formation have been identified. Receptor protein tyrosine phosphatase σ (RPTPσ), a transmembrane tyrosine phosphatase, is widely expressed by neurons in developing and mature mammalian brain, and functions as a receptor for chondroitin sulfate proteoglycans that inhibits axon regeneration following injury. In this study, we address RPTPσ function in the mature brain. We demonstrate increased axon collateral branching in the hippocampus of RPTPσ null mice during normal aging or following chemically induced seizure, indicating that RPTPσ maintains neural circuitry by inhibiting axonal branching. Previous studies demonstrated a role for pre-synaptic RPTPσ promoting synaptic differentiation during development; however, subcellular fractionation revealed enrichment of RPTPσ in post-synaptic densities. We report that neurons lacking RPTPσ have an increased density of pre-synaptic varicosities in vitro and increased dendritic spine density and length in vivo. RPTPσ knockouts exhibit an increased frequency of miniature excitatory post-synaptic currents, and greater paired-pulse facilitation, consistent with increased synapse density but reduced synaptic efficiency. Furthermore, RPTPσ nulls exhibit reduced long-term potentiation and enhanced novel object recognition memory. We conclude that RPTPσ limits synapse number and regulates synapse structure and function in the mature CNS.

  20. Structural plasticity in the topology of the membrane-interacting domain of HIV-1 gp41.

    PubMed

    Kyrychenko, Alexander; Freites, J Alfredo; He, Jing; Tobias, Douglas J; Wimley, William C; Ladokhin, Alexey S

    2014-02-04

    We use a number of computational and experimental approaches to investigate the membrane topology of the membrane-interacting C-terminal domain of the HIV-1 gp41 fusion protein. Several putative transmembrane regions are identified using hydrophobicity analysis based on the Wimley-White scales, including the membrane-proximal external region (MPER). The MPER region is an important target for neutralizing anti-HIV monoclonal antibodies and is believed to have an interfacial topology in the membrane. To assess the possibility of a transmembrane topology of MPER, we examined the membrane interactions of a peptide corresponding to a 22-residue stretch of the MPER sequence (residues 662-683) using fluorescence spectroscopy and oriented circular dichroism. In addition to the previously reported interfacial location, we identify a stable transmembrane conformation of the peptide in synthetic lipid bilayers. All-atom molecular dynamics simulations of the MPER-derived peptide in a lipid bilayer demonstrate a stable helical structure with an average tilt of 24 degrees, with the five tryptophan residues sampling different environments inside the hydrocarbon core of the lipid bilayer, consistent with the observed spectral properties of intrinsic fluorescence. The degree of lipid bilayer penetration obtained by computer simulation was verified using depth-dependent fluorescence quenching of a selectively attached fluorescence probe. Overall, our data indicate that the MPER sequence can have at least two stable conformations in the lipid bilayer, interfacial and transmembrane, and suggest a possibility that external perturbations can switch the topology during physiological functioning.

  1. Structural plasticity and dynamic selectivity of acid-sensing ion channel-spider toxin complexes

    SciTech Connect

    Baconguis, Isabelle; Gouaux, Eric

    2012-07-29

    Acid-sensing ion channels (ASICs) are voltage-independent, amiloride-sensitive channels involved in diverse physiological processes ranging from nociception to taste. Despite the importance of ASICs in physiology, we know little about the mechanism of channel activation. Here we show that psalmotoxin activates non-selective and Na+-selective currents in chicken ASIC1a at pH7.25 and 5.5, respectively. Crystal structures of ASIC1a–psalmotoxin complexes map the toxin binding site to the extracellular domain and show how toxin binding triggers an expansion of the extracellular vestibule and stabilization of the open channel pore. At pH7.25 the pore is approximately 10Å in diameter, whereas at pH5.5 the pore is largely hydrophobic and elliptical in cross-section with dimensions of approximately 5 by 7Å, consistent with a barrier mechanism for ion selectivity. These studies define mechanisms for activation of ASICs, illuminate the basis for dynamic ion selectivity and provide the blueprints for new therapeutic agents.

  2. Multiple keys for a single lock: the unusual structural plasticity of the nucleotidyltransferase (4')/kanamycin complex.

    PubMed

    Matesanz, Ruth; Diaz, José Fernando; Corzana, Francisco; Santana, Andrés G; Bastida, Agatha; Asensio, Juan Luis

    2012-03-05

    The most common mode of bacterial resistance to aminoglycoside antibiotics is the enzyme-catalysed chemical modification of the drug. Over the last two decades, significant efforts in medicinal chemistry have been focused on the design of non- inactivable antibiotics. Unfortunately, this strategy has met with limited success on account of the remarkably wide substrate specificity of aminoglycoside-modifying enzymes. To understand the mechanisms behind substrate promiscuity, we have performed a comprehensive experimental and theoretical analysis of the molecular-recognition processes that lead to antibiotic inactivation by Staphylococcus aureus nucleotidyltransferase 4'(ANT(4')), a clinically relevant protein. According to our results, the ability of this enzyme to inactivate structurally diverse polycationic molecules relies on three specific features of the catalytic region. First, the dominant role of electrostatics in aminoglycoside recognition, in combination with the significant extension of the enzyme anionic regions, confers to the protein/antibiotic complex a highly dynamic character. The motion deduced for the bound antibiotic seem to be essential for the enzyme action and probably provide a mechanism to explore alternative drug inactivation modes. Second, the nucleotide recognition is exclusively mediated by the inorganic fragment. In fact, even inorganic triphosphate can be employed as a substrate. Third, ANT(4') seems to be equipped with a duplicated basic catalyst that is able to promote drug inactivation through different reactive geometries. This particular combination of features explains the enzyme versatility and renders the design of non-inactivable derivatives a challenging task.

  3. Obesity-Induced Structural and Neuronal Plasticity in the Lateral Orbitofrontal Cortex.

    PubMed

    Thompson, Jennifer L; Drysdale, Michael; Baimel, Corey; Kaur, Manpreet; MacGowan, Taigan; Pitman, Kimberley A; Borgland, Stephanie L

    2017-01-18

    The orbitofrontal cortex (OFC) integrates sensory information with the current value of foods and updates actions based on this information. Obese humans and rats fed a cafeteria diet have impaired devaluation of food rewards, implicating a potential obesity-induced dysfunction of the OFC. We hypothesized that obesity alters OFC pyramidal neuronal structure and function and reduces conditioned suppression of feeding. Rats were given restricted (1 h/day), extended (23 h/day) or no (chow only) access to a cafeteria diet and tested for a conditioned suppression of feeding. Golgi-cox impregnation and whole-cell patch clamp experiments were performed in lateral OFC pyramidal neurons of rats from the 3 feeding groups. Rats with 40 days of extended, but not restricted, access to a cafeteria diet became obese and continued to feed during foot shock-predicting cues. Access to a cafeteria diet induced morphological changes in basilar dendrites of lateral OFC pyramidal neurons. While there were no alterations in excitatory synaptic transmission underlying altered spine density, we observed a more depolarized resting membrane potential. This was accompanied by decreased inhibitory synaptic transmission onto lateral OFC pyramidal neurons due to decreased release probability at GABAergic inputs. These changes could underlie the inability of the OFC to encode changes in the motivation value of food that is observed in obese rodents and humans.Neuropsychopharmacology advance online publication, 18 January 2017; doi:10.1038/npp.2016.284.

  4. Structural plasticity and dynamic selectivity of acid-sensing ion channel-spider toxin complexes.

    PubMed

    Baconguis, Isabelle; Gouaux, Eric

    2012-09-20

    Acid-sensing ion channels (ASICs) are voltage-independent, amiloride-sensitive channels involved in diverse physiological processes ranging from nociception to taste. Despite the importance of ASICs in physiology, we know little about the mechanism of channel activation. Here we show that psalmotoxin activates non-selective and Na(+)-selective currents in chicken ASIC1a at pH 7.25 and 5.5, respectively. Crystal structures of ASIC1a-psalmotoxin complexes map the toxin binding site to the extracellular domain and show how toxin binding triggers an expansion of the extracellular vestibule and stabilization of the open channel pore. At pH 7.25 the pore is approximately 10 Å in diameter, whereas at pH 5.5 the pore is largely hydrophobic and elliptical in cross-section with dimensions of approximately 5 by 7 Å, consistent with a barrier mechanism for ion selectivity. These studies define mechanisms for activation of ASICs, illuminate the basis for dynamic ion selectivity and provide the blueprints for new therapeutic agents.

  5. Structural plasticity of calmodulin on the surface of CaF2 nanoparticles preserves its biological function

    NASA Astrophysics Data System (ADS)

    Astegno, Alessandra; Maresi, Elena; Marino, Valerio; Dominici, Paola; Pedroni, Marco; Piccinelli, Fabio; Dell'Orco, Daniele

    2014-11-01

    Nanoparticles are increasingly used in biomedical applications and are especially attractive as biocompatible and biodegradable protein delivery systems. Herein, the interaction between biocompatible 25 nm CaF2 nanoparticles and the ubiquitous calcium sensor calmodulin has been investigated in order to assess the potential of these particles to serve as suitable surface protein carriers. Calmodulin is a multifunctional messenger protein that activates a wide variety of signaling pathways in eukaryotic cells by changing its conformation in a calcium-dependent manner. Isothermal titration calorimetry and circular dichroism studies have shown that the interaction between calmodulin and CaF2 nanoparticles occurs with physiologically relevant affinity and that the binding process is fully reversible, occurring without significant alterations in protein secondary and tertiary structures. Experiments performed with a mutant form of calmodulin having an impaired Ca2+-binding ability in the C-terminal lobe suggest that the EF-hand Ca2+-binding motifs are directly involved in the binding of calmodulin to the CaF2 matrix. The residual capability of nanoparticle-bound calmodulin to function as a calcium sensor protein, binding to and altering the activity of a target protein, was successfully probed by biochemical assays. Even if efficiently carried by CaF2 nanoparticles, calmodulin may dissociate, thus retaining the ability to bind the peptide encompassing the putative C-terminal calmodulin-binding domain of glutamate decarboxylase and activate the enzyme. We conclude that the high flexibility and structural plasticity of calmodulin are responsible for the preservation of its function when bound in high amounts to a nanoparticle surface.Nanoparticles are increasingly used in biomedical applications and are especially attractive as biocompatible and biodegradable protein delivery systems. Herein, the interaction between biocompatible 25 nm CaF2 nanoparticles and the ubiquitous

  6. Multiclass Classification by Adaptive Network of Dendritic Neurons with Binary Synapses Using Structural Plasticity

    PubMed Central

    Hussain, Shaista; Basu, Arindam

    2016-01-01

    The development of power-efficient neuromorphic devices presents the challenge of designing spike pattern classification algorithms which can be implemented on low-precision hardware and can also achieve state-of-the-art performance. In our pursuit of meeting this challenge, we present a pattern classification model which uses a sparse connection matrix and exploits the mechanism of nonlinear dendritic processing to achieve high classification accuracy. A rate-based structural learning rule for multiclass classification is proposed which modifies a connectivity matrix of binary synaptic connections by choosing the best “k” out of “d” inputs to make connections on every dendritic branch (k < < d). Because learning only modifies connectivity, the model is well suited for implementation in neuromorphic systems using address-event representation (AER). We develop an ensemble method which combines several dendritic classifiers to achieve enhanced generalization over individual classifiers. We have two major findings: (1) Our results demonstrate that an ensemble created with classifiers comprising moderate number of dendrites performs better than both ensembles of perceptrons and of complex dendritic trees. (2) In order to determine the moderate number of dendrites required for a specific classification problem, a two-step solution is proposed. First, an adaptive approach is proposed which scales the relative size of the dendritic trees of neurons for each class. It works by progressively adding dendrites with fixed number of synapses to the network, thereby allocating synaptic resources as per the complexity of the given problem. As a second step, theoretical capacity calculations are used to convert each neuronal dendritic tree to its optimal topology where dendrites of each class are assigned different number of synapses. The performance of the model is evaluated on classification of handwritten digits from the benchmark MNIST dataset and compared with other

  7. Multiclass Classification by Adaptive Network of Dendritic Neurons with Binary Synapses Using Structural Plasticity.

    PubMed

    Hussain, Shaista; Basu, Arindam

    2016-01-01

    The development of power-efficient neuromorphic devices presents the challenge of designing spike pattern classification algorithms which can be implemented on low-precision hardware and can also achieve state-of-the-art performance. In our pursuit of meeting this challenge, we present a pattern classification model which uses a sparse connection matrix and exploits the mechanism of nonlinear dendritic processing to achieve high classification accuracy. A rate-based structural learning rule for multiclass classification is proposed which modifies a connectivity matrix of binary synaptic connections by choosing the best "k" out of "d" inputs to make connections on every dendritic branch (k < < d). Because learning only modifies connectivity, the model is well suited for implementation in neuromorphic systems using address-event representation (AER). We develop an ensemble method which combines several dendritic classifiers to achieve enhanced generalization over individual classifiers. We have two major findings: (1) Our results demonstrate that an ensemble created with classifiers comprising moderate number of dendrites performs better than both ensembles of perceptrons and of complex dendritic trees. (2) In order to determine the moderate number of dendrites required for a specific classification problem, a two-step solution is proposed. First, an adaptive approach is proposed which scales the relative size of the dendritic trees of neurons for each class. It works by progressively adding dendrites with fixed number of synapses to the network, thereby allocating synaptic resources as per the complexity of the given problem. As a second step, theoretical capacity calculations are used to convert each neuronal dendritic tree to its optimal topology where dendrites of each class are assigned different number of synapses. The performance of the model is evaluated on classification of handwritten digits from the benchmark MNIST dataset and compared with other spike

  8. Masticatory loading, function, and plasticity: a microanatomical analysis of mammalian circumorbital soft-tissue structures.

    PubMed

    Jasarević, Eldin; Ning, Jie; Daniel, Ashley N; Menegaz, Rachel A; Johnson, Jeffrey J; Stack, M Sharon; Ravosa, Matthew J

    2010-04-01

    In contrast to experimental evidence regarding the postorbital bar, postorbital septum, and browridge, there is exceedingly little evidence regarding the load-bearing nature of soft-tissue structures of the mammalian circumorbital region. This hinders our understanding of pronounced transformations during primate origins, in which euprimates evolved a postorbital bar from an ancestor with the primitive mammalian condition where only soft tissues spanned the lateral orbital margin between frontal bone and zygomatic arch. To address this significant gap, we investigated the postorbital microanatomy of rabbits subjected to long-term variation in diet-induced masticatory stresses. Rabbits exhibit a masticatory complex and feeding behaviors similar to primates, yet retain a more primitive mammalian circumorbital region. Three cohorts were obtained as weanlings and raised on different diets until adult. Following euthanasia, postorbital soft tissues were dissected away, fixed, and decalcified. These soft tissues were divided into inferior, intermediate, and superior units and then dehydrated, embedded, and sectioned. H&E staining was used to characterize overall architecture. Collagen orientation and complexity were evaluated via picrosirius-red staining. Safranin-O identified proteoglycan content with additional immunostaining performed to assess Type-II collagen expression. Surprisingly, the ligament along the lateral orbital wall was composed of elastic fibrocartilage. A more degraded organization of collagen fibers in this postorbital fibrocartilage is correlated with increased masticatory forces due to a more fracture-resistant diet. Furthermore, the lack of marked changes in the extracellular composition of the lateral orbital wall related to tissue viscoelasticity suggests it is unlikely that long-term exposure to elevated masticatory stresses underlies the development of a bony postorbital bar.

  9. Sleep-Dependent Structural Synaptic Plasticity of Inhibitory Synapses in the Dendrites of Hypocretin/Orexin Neurons.

    PubMed

    Elbaz, Idan; Zada, David; Tovin, Adi; Braun, Tslil; Lerer-Goldshtein, Tali; Wang, Gordon; Mourrain, Philippe; Appelbaum, Lior

    2016-10-12

    Sleep is tightly regulated by the circadian clock and homeostatic mechanisms. Although the sleep/wake cycle is known to be associated with structural and physiological synaptic changes that benefit the brain, the function of sleep is still debated. The hypothalamic hypocretin/orexin (Hcrt) neurons regulate various functions including feeding, reward, sleep, and wake. Continuous imaging of single neuronal circuits in live animals is vital to understanding the role of sleep in regulating synaptic dynamics, and the transparency of the zebrafish model enables time-lapse imaging of single synapses during both day and night. Here, we use the gephyrin (Gphnb) protein, a central inhibitory synapse organizer, as a fluorescent post-synaptic marker of inhibitory synapses. Double labeling showed that Gphnb-tagRFP and collybistin-EGFP clusters co-localized in dendritic inhibitory synapses. Using a transgenic hcrt:Gphnb-EGFP zebrafish, we showed that the number of inhibitory synapses in the dendrites of Hcrt neurons was increased during development. To determine the effect of sleep on the inhibitory synapses, we performed two-photon live imaging of Gphnb-EGFP in Hcrt neurons during day and night, under light/dark and constant light and dark conditions, and following sleep deprivation (SD). We found that synapse number increased during the night under light/dark conditions but that these changes were eliminated under constant light or dark conditions. SD reduced synapse number during the night, and the number increased during post-deprivation daytime sleep rebound. These results suggest that rhythmic structural plasticity of inhibitory synapses in Hcrt dendrites is independent of the circadian clock and is modulated by consolidated wake and sleep.

  10. Synaptic strength is bidirectionally controlled by opposing activity-dependent regulation of Nedd4-1 and USP8.

    PubMed

    Scudder, Samantha L; Goo, Marisa S; Cartier, Anna E; Molteni, Alice; Schwarz, Lindsay A; Wright, Rebecca; Patrick, Gentry N

    2014-12-10

    The trafficking of AMPA receptors (AMPARs) to and from synapses is crucial for synaptic plasticity. Previous work has demonstrated that AMPARs undergo activity-dependent ubiquitination by the E3 ubiquitin ligase Nedd4-1, which promotes their internalization and degradation in lysosomes. Here, we define the molecular mechanisms involved in ubiquitination and deubiquitination of AMPARs. We report that Nedd4-1 is rapidly redistributed to dendritic spines in response to AMPAR activation and not in response to NMDA receptor (NMDAR) activation in cultured rat neurons. In contrast, NMDAR activation directly antagonizes Nedd4-1 function by promoting the deubiquitination of AMPARs. We show that NMDAR activation causes the rapid dephosphorylation and activation of the deubiquitinating enzyme (DUB) USP8. Surface AMPAR levels and synaptic strength are inversely regulated by Nedd4-1 and USP8. Strikingly, we show that homeostatic downscaling of synaptic strength is accompanied by an increase and decrease in Nedd4-1 and USP8 protein levels, respectively. Furthermore, we show that Nedd4-1 is required for homeostatic loss of surface AMPARs and downscaling of synaptic strength. This study provides the first mechanistic evidence for rapid and opposing activity-dependent control of a ubiquitin ligase and DUB at mammalian CNS synapses. We propose that the dynamic regulation of these opposing forces is critical in maintaining synapses and scaling them during homeostatic plasticity.

  11. Emergence of network structure due to spike-timing-dependent plasticity in recurrent neuronal networks IV: structuring synaptic pathways among recurrent connections.

    PubMed

    Gilson, Matthieu; Burkitt, Anthony N; Grayden, David B; Thomas, Doreen A; van Hemmen, J Leo

    2009-12-01

    In neuronal networks, the changes of synaptic strength (or weight) performed by spike-timing-dependent plasticity (STDP) are hypothesized to give rise to functional network structure. This article investigates how this phenomenon occurs for the excitatory recurrent connections of a network with fixed input weights that is stimulated by external spike trains. We develop a theoretical framework based on the Poisson neuron model to analyze the interplay between the neuronal activity (firing rates and the spike-time correlations) and the learning dynamics, when the network is stimulated by correlated pools of homogeneous Poisson spike trains. STDP can lead to both a stabilization of all the neuron firing rates (homeostatic equilibrium) and a robust weight specialization. The pattern of specialization for the recurrent weights is determined by a relationship between the input firing-rate and correlation structures, the network topology, the STDP parameters and the synaptic response properties. We find conditions for feed-forward pathways or areas with strengthened self-feedback to emerge in an initially homogeneous recurrent network.

  12. Attenuation of stress waves in single and multi-layered structures. [mitigation of elastic and plastic stress waves during spacecraft landing

    NASA Technical Reports Server (NTRS)

    Yang, J. C. S.; Tsui, C. Y.

    1972-01-01

    Analytical and experimental studies were made of the attenuation of the stress waves during passage through single and multilayer structures. The investigation included studies on elastic and plastic stress wave propagation in the composites and those on shock mitigating material characteristics such as dynamic stress-strain relations and energy absorbing properties. The results of the studies are applied to methods for reducing the stresses imposed on a spacecraft during planetary or ocean landings.

  13. Plastic Surgery Statistics

    MedlinePlus

    ... PRS GO PSN PSEN GRAFT Contact Us News Plastic Surgery Statistics Plastic surgery procedural statistics from the ... Plastic Surgery Statistics 2005 Plastic Surgery Statistics 2016 Plastic Surgery Statistics Stats Report 2016 National Clearinghouse of ...

  14. Impairments of Synaptic Plasticity in Aged Animals and in Animal Models of Alzheimer's Disease

    PubMed Central

    Balietti, Marta; Tamagnini, Francesco; Fattoretti, Patrizia; Burattini, Costanza; Casoli, Tiziana; Platano, Daniela; Lattanzio, Fabrizia

    2012-01-01

    Abstract Aging is associated with a gradual decline in cognitive functions, and more dramatic cognitive impairments occur in patients affected by Alzheimer's disease (AD). Electrophysiological and molecular studies performed in aged animals and in animal models of AD have shown that cognitive decline is associated with significant modifications in synaptic plasticity (i.e., activity-dependent changes in synaptic strength) and have elucidated some of the cellular mechanisms underlying this process. Morphological studies have revealed a correlation between the quality of memory performance and the extent of structural changes of synaptic contacts occurring during memory consolidation. We briefly review recent experimental evidence here. PMID:22533439

  15. Occipital TMS has an activity-dependent suppressive effect

    PubMed Central

    Perini, Francesca; Cattaneo, Luigi; Carrasco, Marisa; Schwarzbach, Jens V.

    2012-01-01

    The effects of transcranial magnetic stimulation (TMS) vary depending on the brain state at the stimulation moment. Four mechanisms have been proposed to underlie these effects: (i) virtual lesion–TMS suppresses neural signals; (ii) preferential activation of less active neurons–TMS drives up activity in the stimulated area, but active neurons are saturating, (iii) noise generation–TMS adds random neuronal activity and its effect interacts with stimulus-intensity; (iv) noise generation–TMS adds random neuronal activity and its effect depends on TMS-intensity. Here we explore these hypotheses by investigating the effects of TMS on early visual cortex on the contrast response function while varying adaptation state of the observers. We tested human participants in an orientation discrimination task, in which performance is contingent upon contrast sensitivity. Before each trial, neuronal activation of visual cortex was altered through contrast adaptation to two flickering gratings. In a factorial design, with or without adaptation, a single TMS pulse was delivered simultaneously with targets of varying contrast. Adaptation decreased contrast sensitivity. The effect of TMS on performance was state-dependent: TMS decreased contrast sensitivity in the absence of adaptation but increased it after adaptation. None of the proposed mechanisms can account for the results in their entirety, in particular, for the facilitatory effect at intermediate to high contrasts after adaptation. We propose an alternative hypothesis: TMS effects are activity-dependent, so that TMS suppresses the most active neurons and thereby changes the balance between excitation and inhibition. PMID:22956826

  16. The pseudokinase CaMKv is required for the activity-dependent maintenance of dendritic spines

    PubMed Central

    Liang, Zhuoyi; Zhan, Yi; Shen, Yang; Wong, Catherine C. L.; Yates, John R.; Plattner, Florian; Lai, Kwok-On; Ip, Nancy Y.

    2016-01-01

    Dendritic spine stabilization depends on afferent synaptic input and requires changes in actin cytoskeleton dynamics and protein synthesis. However, the underlying molecular mechanism remains unclear. Here we report the identification of ‘calmodulin kinase-like vesicle-associated' (CaMKv), a pseudokinase of the CaMK family with unknown function, as a synaptic protein crucial for dendritic spine maintenance. CaMKv mRNA localizes at dendrites, and its protein synthesis is regulated by neuronal activity. CaMKv function is inhibited upon phosphorylation by cyclin-dependent kinase 5 (Cdk5) at Thr345. Furthermore, CaMKv knockdown in mouse hippocampal CA1 pyramidal neurons impairs synaptic transmission and plasticity in vivo, resulting in hyperactivity and spatial memory impairment. These findings collectively indicate that the precise regulation of CaMKv through activity-dependent synthesis and post-translational phosphorylation is critical for dendritic spine maintenance, revealing an unusual signalling pathway in the regulation of synaptic transmission and brain function that involves a pseudokinase. PMID:27796283

  17. Neuronal activity-dependent membrane traffic at the neuromuscular junction

    PubMed Central

    Miana-Mena, Francisco Javier; Roux, Sylvie; Benichou, Jean-Claude; Osta, Rosario; Brûlet, Philippe

    2002-01-01

    During development and also in adulthood, synaptic connections are modulated by neuronal activity. To follow such modifications in vivo, new genetic tools are designed. The nontoxic C-terminal fragment of tetanus toxin (TTC) fused to a reporter gene such as LacZ retains the retrograde and transsynaptic transport abilities of the holotoxin itself. In this work, the hybrid protein is injected intramuscularly to analyze in vivo the mechanisms of intracellular and transneuronal traffics at the neuromuscular junction (NMJ). Traffic on both sides of the synapse are strongly dependent on presynaptic neural cell activity. In muscle, a directional membrane traffic concentrates β-galactosidase-TTC hybrid protein into the NMJ postsynaptic side. In neurons, the probe is sorted across the cell to dendrites and subsequently to an interconnected neuron. Such fusion protein, sensitive to presynaptic neuronal activity, would be extremely useful to analyze morphological changes and plasticity at the NMJ. PMID:11880654

  18. Morphological and structural plasticity of grassland species in response to a gradient in saline-sodic soils.

    PubMed

    Huang, Y; Song, Y; Li, G; Drake, P L; Zheng, W; Li, Z; Zhou, D

    2015-11-01

    The abundance and distribution of species can be ascribed to both environmental heterogeneity and stress tolerance, with the latter measure sometimes associated with phenotypic plasticity. Although phenotypic plasticity varies predictably in response to common forms of stress, we lack a mechanistic understanding of the response of species to high saline-sodic soils. We compared the phenotypic plasticity of three pairs of high and low saline-sodic tolerant congeners from the families Poaceae (Leymus chinensis versus L. secalinus), Fabaceae (Lespedeza davurica versus L. bicolor) and Asteraceae (Artemisia mongolica versus A. sieversiana) in a controlled pot experiment in the Songnen grassland, China. The low tolerant species, L. secalinus and A. sieversiana exhibited higher plasticity in response to soil salinity and sodicity than their paired congeners. Highly tolerant species, L. chinensis and A. mongolica, had higher values for several important morphological traits, such as shoot length and total biomass under the high saline-sodic soil treatment than their paired congeners. In contrast, congeners from the family Fabaceae, L. davurica and L. bicolor, did not exhibit significantly different plasticity in response to soil salinity and sodicity. All species held a constant reproductive effort in response to saline-sodic soil stress. The different responses between low and high tolerant species offer an explanation for the distribution patterns of these species in the Songnen grassland. Highly tolerant species showed less morphological plasticity over a range of saline-sodic conditions than their paired congeners, which may manifest as an inability to compete with co-occurring species in locations where saline-sodic soils are absent.

  19. Structure of the iSH2 domain of Human phosphatidylinositol 3-kinase p85 beta Subunit Reveals Conformational Plasticity in the Interhelical Turn Region

    SciTech Connect

    C Schauder; L Ma; R Krug; G Montelione; R Guan

    2011-12-31

    Phosphatidylinositol 3-kinase (PI3K) proteins actively trigger signaling pathways leading to cell growth, proliferation and survival. These proteins have multiple isoforms and consist of a catalytic p110 subunit and a regulatory p85 subunit. The iSH2 domain of the p85 {beta} isoform has been implicated in the binding of nonstructural protein 1 (NS1) of influenza A viruses. Here, the crystal structure of human p85 {beta} iSH2 determined to 3.3 {angstrom} resolution is reported. The structure reveals that this domain mainly consists of a coiled-coil motif. Comparison with the published structure of the bovine p85 {beta} iSH2 domain bound to the influenza A virus nonstructural protein 1 indicates that little or no structural change occurs upon complex formation. By comparing this human p85 {beta} iSH2 structure with the bovine p85 {beta} iSH2 domain, which shares 99% sequence identity, and by comparing the multiple conformations observed within the asymmetric unit of the bovine iSH2 structure, it was found that this coiled-coil domain exhibits a certain degree of conformational variability or 'plasticity' in the interhelical turn region. It is speculated that this plasticity of p85 {beta} iSH2 may play a role in regulating its functional and molecular-recognition properties.

  20. Crystal Structures and Phase Sequences of Metallocenium Salts with Fluorinated Anions: Effects of Molecular Size and Symmetry on Phase Transitions to Ionic Plastic Crystals.

    PubMed

    Mochida, Tomoyuki; Funasako, Yusuke; Ishida, Mai; Saruta, Shingo; Kosone, Takashi; Kitazawa, Takafumi

    2016-10-24

    Sandwich compounds often exhibit various phase transitions, including those to plastic phases. To elucidate the general features of the phase transitions in metallocenium salts, the thermal properties and crystal structures of [Fe(C5 Me5 )2 ]X ([1]X), [Co(C5 Me5 )2 ]X ([2]X), and [Fe(C5 Me4 H)2 ]X ([3]X) have been investigated, where the counter anions (X) are Tf2 N (=(CF3 SO2 )2 N(-) ), OTf (=CF3 SO3(-) ), PF6 , and BF4 . The Tf2 N salts commonly undergo phase transitions from an ordered phase at low temperatures to an anion-disordered phase, followed by a plastic phase and finally melt at high temperatures. All these salts exhibit a phase transition to a plastic phase, and the transition temperature generally decreases with decreasing cation size and increasing anion size. The crystal structures of these salts comprise an alternating arrangement of cations and anions. About half of these salts exhibit phase transitions at low temperatures, which are mostly correlated with the order-disorder of the anion.

  1. Polysialic Acid Acute Depletion Induces Structural Plasticity in Interneurons and Impairs the Excitation/Inhibition Balance in Medial Prefrontal Cortex Organotypic Cultures

    PubMed Central

    Castillo-Gómez, Esther; Pérez-Rando, Marta; Vidueira, Sandra; Nacher, Juan

    2016-01-01

    The structure and function of the medial prefrontal cortex (mPFC) is affected in several neuropsychiatric disorders, including schizophrenia and major depression. Recent studies suggest that imbalances between excitatory and inhibitory activity (E/I) may be responsible for this cortical dysfunction and therefore, may underlie the core symptoms of these diseases. This E/I imbalance seems to be correlated with alterations in the plasticity of interneurons but there is still scarce information on the mechanisms that may link these phenomena. The polysialylated form of the neural cell adhesion molecule (PSA-NCAM) is a good candidate, because it modulates the neuronal plasticity of interneurons and its expression is altered in schizophrenia and major depression. To address this question, we have developed an in vitro model using mPFC organotypic cultures of transgenic mice displaying fluorescent spiny interneurons. After enzymatic depletion of PSA, the spine density of interneurons, the number of synaptic puncta surrounding pyramidal neuron somata and the E/I ratio were strongly affected. These results point to the polysialylation of NCAM as an important factor in the maintenance of E/I balance and the structural plasticity of interneurons. This may be particularly relevant for better understanding the etiology of schizophrenia and major depression. PMID:27445697

  2. Computer program: Jet 3 to calculate the large elastic plastic dynamically induced deformations of free and restrained, partial and/or complete structural rings

    NASA Technical Reports Server (NTRS)

    Wu, R. W.; Witmer, E. A.

    1972-01-01

    A user-oriented FORTRAN 4 computer program, called JET 3, is presented. The JET 3 program, which employs the spatial finite-element and timewise finite-difference method, can be used to predict the large two-dimensional elastic-plastic transient Kirchhoff-type deformations of a complete or partial structural ring, with various support conditions and restraints, subjected to a variety of initial velocity distributions and externally-applied transient forcing functions. The geometric shapes of the structural ring can be circular or arbitrarily curved and with variable thickness. Strain-hardening and strain-rate effects of the material are taken into account.

  3. Finite element analysis of large transient elastic-plastic deformations of simple structures, with application to the engine rotor fragment containment/deflection problem

    NASA Technical Reports Server (NTRS)

    Wu, R. W.; Witmer, E. A.

    1972-01-01

    Assumed-displacement versions of the finite-element method are developed to predict large-deformation elastic-plastic transient deformations of structures. Both the conventional and a new improved finite-element variational formulation are derived. These formulations are then developed in detail for straight-beam and curved-beam elements undergoing (1) Bernoulli-Euler-Kirchhoff or (2) Timoshenko deformation behavior, in one plane. For each of these categories, several types of assumed-displacement finite elements are developed, and transient response predictions are compared with available exact solutions for small-deflection, linear-elastic transient responses. The present finite-element predictions for large-deflection elastic-plastic transient responses are evaluated via several beam and ring examples for which experimental measurements of transient strains and large transient deformations and independent finite-difference predictions are available.

  4. Structure and mechanical properties of aging Al-Li-Cu-Zr-Sc-Ag alloy after severe plastic deformation by high-pressure torsion

    NASA Astrophysics Data System (ADS)

    Kaigorodova, L. I.; Rasposienko, D. Yu.; Pushin, V. G.; Pilyugin, V. P.; Smirnov, S. V.

    2015-04-01

    The structural and phase transformations have been studied in aging commercial aluminum-lithium alloy Al-1.2 Li-3.2 Cu-0.09 Zr-0.11 Sc-0.4 Ag-0.3 Mg in the as-delivered state and after severe plastic deformation by torsion for 1, 5 and 10 revolutions under a high pressure of 4 GPa. Deformation-induced nanofragmentation and dynamic recrystallization have been found to occur in the alloy. The degree of recrystallization increases with deformation. Nanofragmentation and recrystallization processes are accompanied by the deformation-induced decomposition of solid solution and changes in both the nucleation mechanism of precipitation and the phase composition of the alloy. The influence of a nanostructured nanophase state of the alloy on its mechanical properties (microhardness, plasticity, elastic modulus, and stiffness) is discussed.

  5. ANTEC '86: Plastic-value through technology

    SciTech Connect

    Not Available

    1986-01-01

    This book contains 23 sections, each containing several papers. There are also papers under a general category and a student category. The section titles are: Plastics in Automotive Division; Thermoplastic Materials and Foams Division; Injection Molding Division; Mold Making and Mold Design Division; Electrical and Electronic Division; Plastics Analysis Division and Electrical and Electronic Division Joint Sessions; Plastics Analysis Division and Engineering Properties and Structure Division; Plastics Analysis Division; Engineering Properties and Structure Division and Plastics Analysis Division Joint Session; Engineering Properties and Structure Division; Blow Molding Division; Extrusion Division and Thermoforming Division Joint Session; Extrusion Division; Thermoforming Division; Plastics Education and Training; Marketing Division; Medical Plastics Division; Decorating Division; Polymer Modifiers and Additives Division; Color and Appearance Division; Vinyl Division; Thermoset Division; and Computers and the Plastics Industry.

  6. Solution NMR characterization of chemokine CXCL8/IL-8 monomer and dimer binding to glycosaminoglycans: structural plasticity mediates differential binding interactions.

    PubMed

    Joseph, Prem Raj B; Mosier, Philip D; Desai, Umesh R; Rajarathnam, Krishna

    2015-11-15

    Chemokine CXCL8/interleukin-8 (IL-8) plays a crucial role in directing neutrophils and oligodendrocytes to combat infection/injury and tumour cells in metastasis development. CXCL8 exists as monomers and dimers and interaction of both forms with glycosaminoglycans (GAGs) mediate these diverse cellular processes. However, very little is known regarding the structural basis underlying CXCL8-GAG interactions. There are conflicting reports on the affinities, geometry and whether the monomer or dimer is the high-affinity GAG ligand. To resolve these issues, we characterized the binding of a series of heparin-derived oligosaccharides [heparin disaccharide (dp2), heparin tetrasaccharide (dp4), heparin octasaccharide (dp8) and heparin 14-mer (dp14)] to the wild-type (WT) dimer and a designed monomer using solution NMR spectroscopy. The pattern and extent of binding-induced chemical shift perturbation (CSP) varied between dimer and monomer and between longer and shorter oligosaccharides. NMR-based structural models show that different interaction modes coexist and that the nature of interactions varied between monomer and dimer and oligosaccharide length. MD simulations indicate that the binding interface is structurally plastic and provided residue-specific details of the dynamic nature of the binding interface. Binding studies carried out under conditions at which WT CXCL8 exists as monomers and dimers provide unambiguous evidence that the dimer is the high-affinity GAG ligand. Together, our data indicate that a set of core residues function as the major recognition/binding site, a set of peripheral residues define the various binding geometries and that the structural plasticity of the binding interface allows multiplicity of binding interactions. We conclude that structural plasticity most probably regulates in vivo CXCL8 monomer/dimer-GAG interactions and function.

  7. Plastic Bronchitis.

    PubMed

    Rubin, Bruce K

    2016-09-01

    Plastic bronchitis is an uncommon and probably underrecognized disorder, diagnosed by the expectoration or bronchoscopic removal of firm, cohesive, branching casts. It should not be confused with purulent mucous plugging of the airway as seen in patients with cystic fibrosis or bronchiectasis. Few medications have been shown to be effective and some are now recognized as potentially harmful. Current research directions in plastic bronchitis research include understanding the genetics of lymphatic development and maldevelopment, determining how abnormal lymphatic malformations contribute to cast formation, and developing new treatments.

  8. NRC-interacting factor directs neurite outgrowth in an activity-dependent manner.

    PubMed

    Zhao, X-S; Fu, W-Y; Hung, K-W; Chien, W W Y; Li, Z; Fu, A K; Ip, N Y

    2015-03-19

    Nuclear hormone receptor coregulator-interacting factor 1 (NIF-1) is a zinc finger nuclear protein that was initially identified to enhance nuclear hormone receptor transcription via its interaction with nuclear hormone receptor coregulator (NRC). NIF-1 may regulate gene transcription either by modulating general transcriptional machinery or remodeling chromatin structure through interactions with specific protein partners. We previously reported that the cytoplasmic/nuclear localization of NIF-1 is regulated by the neuronal Cdk5 activator p35, suggesting potential neuronal functions for NIF-1. The present study reveals that NIF-1 plays critical roles in regulating neuronal morphogenesis at early stages. NIF-1 was prominently expressed in the nuclei of developing rat cortical neurons. Knockdown of NIF-1 expression attenuated both neurite outgrowth in cultured cortical neurons and retinoic acid (RA)-treated Neuro-2a neuroblastoma cells. Furthermore, activity-induced Ca(2+) influx, which is critical for neuronal morphogenesis, stimulated the nuclear localization of NIF-1 in cortical neurons. Suppression of NIF-1 expression reduced the up-regulation of neuronal activity-dependent gene transcription. These findings collectively suggest that NIF-1 directs neuronal morphogenesis during early developmental stages through modulating activity-dependent gene transcription.

  9. Dense small molecule labeling enables activator-dependent STORM by proximity mapping.

    PubMed

    Chen, Ye; Gu, Min; Gunning, Peter W; Russell, Sarah M

    2016-09-01

    Stochastic optical reconstruction microscopy (STORM) enables high-resolution imaging, but multi-channel 3D imaging is problematic because of chromatic aberrations and alignment errors. The use of activator-dependent STORM in which spectrally distinct activators can be coupled with a single reporter can circumvent such issues. However, the standard approach of linking activators and reporters to a single antibody molecule is hampered by low labeling density and the large size of the antibody. We proposed that small molecule labels might enable activator-dependent STORM if the reporter or activator were linked to separate small molecules that bound within 3.5 nm of each other. This would greatly increase the labeling density and therefore improve resolution. We tested various mixtures of phalloidin- or mCling-conjugated fluorophore to demonstrate this feasibility. The specific activation was dependent on the choice of activator, its density, a matching activating laser and its power. In addition to providing an effective means of multi-channel 3D STORM imaging, this method also provides information about the local proximity between labels, potentially enabling super-resolved mapping of the conformation of the labeled structures.

  10. Plastics Technician.

    ERIC Educational Resources Information Center

    Ohio State Univ., Columbus. Center on Education and Training for Employment.

    This document contains 16 units to consider for use in a tech prep competency profile for the occupation of plastics technician. All the units listed will not necessarily apply to every situation or tech prep consortium, nor will all the competencies within each unit be appropriate. Several units appear within each specific occupation and would…

  11. Evaluation of drug release profile from patches based on styrene-isoprene-styrene block copolymer: the effect of block structure and plasticizer.

    PubMed

    Wang, ChengXiao; Han, Wei; Tang, XiuZhen; Zhang, Hao

    2012-06-01

    We prepared pressure-sensitive adhesive (PSA) patches based on styrene-isoprene-styrene (SIS) thermoplastic elastomer using hot-melt coating method. The liquid paraffine is added in the PSA matrices as a plasticizer to moderate the PSA properties. Three drugs, methyl salicylate, capsaicin, and diphenhydramine hydrochloride are selected as model drugs. The Fourier transform infrared spectroscopy, differential scanning calorimetry test, and wide-angle X-ray diffraction test indicate a good compatibility between drugs and matrices. Peppas equation is used to describe drug release profile. Different drug-matrix absorption, as indicative of drug-matrix interaction, accounts for the variation in release profiles of different drugs. Furthermore, atomic force microscopy and rheological studies of the PSA samples are performed to investigate the effect of SIS structure and plasticizer of PSA on drug release behaviors. For methyl salicylate and capsaicin, drug diffusion in the PSA matrices is the main factor controlled by the release kinetic constant k. The high [SI] diblock content and high plasticizer amount in matrix provide the PSA with a homogeneous and soften microstructure, resulting in a high diffusion rate. But for water-soluble drugs such as diphenhydramine hydrochloride, the release rate is governed by water penetration with the competition from diffusion mechanisms.

  12. Characterization via atomic force microscopy of discrete plasticity in collagen fibrils from mechanically overloaded tendons: Nano-scale structural changes mimic rope failure.

    PubMed

    Baldwin, Samuel J; Kreplak, Laurent; Lee, J Michael

    2016-07-01

    Tendons exposed to tensile overload show a structural alteration at the fibril scale termed discrete plasticity. Serial kinks appear along individual collagen fibrils that are susceptible to enzymatic digestion and are thermally unstable. Using atomic force microscopy we mapped the topography and mechanical properties in dehydrated and hydrated states of 25 control fibrils and 25 fibrils displaying periodic kinks, extracted from overloaded bovine tail tendons. Using the measured modulus of the hydrated fibrils as a probe of molecular density, we observed a non-linear negative correlation between molecular density and kink density of individual fibrils. This is accompanied by an increase in water uptake with kink density and a doubling of the coefficient of variation of the modulus between kinked, and control fibrils. The mechanical property maps of kinked collagen fibrils show radial heterogeneity that can be modeled as a high-density core surrounded by a low-density shell. The core of the fibril contains the kink structures characteristic of discrete plasticity; separated by inter-kink regions, which often retain the D-banding structure. We propose that the shell and kink structures mimic characteristic damage motifs observed in laid rope strands.

  13. Epigenetic Basis of Neuronal and Synaptic Plasticity.

    PubMed

    Karpova, Nina N; Sales, Amanda J; Joca, Samia R

    2017-01-01

    Neuronal network and plasticity change as a function of experience. Altered neural connectivity leads to distinct transcriptional programs of neuronal plasticity-related genes. The environmental challenges throughout life may promote long-lasting reprogramming of gene expression and the development of brain disorders. The modifications in neuronal epigenome mediate gene-environmental interactions and are required for activity-dependent regulation of neuronal differentiation, maturation and plasticity. Here, we highlight the latest advances in understanding the role of the main players of epigenetic machinery (DNA methylation and demethylation, histone modifications, chromatin-remodeling enzymes, transposons, and non-coding RNAs) in activity-dependent and long- term neural and synaptic plasticity. The review focuses on both the transcriptional and post-transcriptional regulation of gene expression levels, including the processes of promoter activation, alternative splicing, regulation of stability of gene transcripts by natural antisense RNAs, and alternative polyadenylation. Further, we discuss the epigenetic aspects of impaired neuronal plasticity and the pathogenesis of neurodevelopmental (Rett syndrome, Fragile X Syndrome, genomic imprinting disorders, schizophrenia, and others), stressrelated (mood disorders) and neurodegenerative Alzheimer's, Parkinson's and Huntington's disorders. The review also highlights the pharmacological compounds that modulate epigenetic programming of gene expression, the potential treatment strategies of discussed brain disorders, and the questions that should be addressed during the development of effective and safe approaches for the treatment of brain disorders.

  14. Theoretical models of synaptic short term plasticity

    PubMed Central

    Hennig, Matthias H.

    2013-01-01

    Short term plasticity is a highly abundant form of rapid, activity-dependent modulation of synaptic efficacy. A shared set of mechanisms can cause both depression and enhancement of the postsynaptic response at different synapses, with important consequences for information processing. Mathematical models have been extensively used to study the mechanisms and roles of short term plasticity. This review provides an overview of existing models and their biological basis, and of their main properties. Special attention will be given to slow processes such as calcium channel inactivation and the effect of activation of presynaptic autoreceptors. PMID:23626536

  15. GLASS FIBER REINFORCED PLASTICS,

    DTIC Science & Technology

    Contents: Fibrous glass fillers Binders used in the glass plastic industry Method of manufacturing glass plastics and glass plastic articles Properties of fiberglass Primary areas for use of glass fibre reinforced plastics

  16. Modulation of Synaptic Plasticity by Glutamatergic Gliotransmission: A Modeling Study

    PubMed Central

    De Pittà, Maurizio; Brunel, Nicolas

    2016-01-01

    Glutamatergic gliotransmission, that is, the release of glutamate from perisynaptic astrocyte processes in an activity-dependent manner, has emerged as a potentially crucial signaling pathway for regulation of synaptic plasticity, yet its modes of expression and function in vivo remain unclear. Here, we focus on two experimentally well-identified gliotransmitter pathways, (i) modulations of synaptic release and (ii) postsynaptic slow inward currents mediated by glutamate released from astrocytes, and investigate their possible functional relevance on synaptic plasticity in a biophysical model of an astrocyte-regulated synapse. Our model predicts that both pathways could profoundly affect both short- and long-term plasticity. In particular, activity-dependent glutamate release from astrocytes could dramatically change spike-timing-dependent plasticity, turning potentiation into depression (and vice versa) for the same induction protocol. PMID:27195153

  17. Genetic Feedback Regulation of Frontal Cortical Neuronal Ensembles Through Activity-Dependent Arc Expression and Dopaminergic Input

    PubMed Central

    Mastwal, Surjeet; Cao, Vania; Wang, Kuan Hong

    2016-01-01

    Mental functions involve coordinated activities of specific neuronal ensembles that are embedded in complex brain circuits. Aberrant neuronal ensemble dynamics is thought to form the neurobiological basis of mental disorders. A major challenge in mental health research is to identify these cellular ensembles and determine what molecular mechanisms constrain their emergence and consolidation during development and learning. Here, we provide a perspective based on recent studies that use activity-dependent gene Arc/Arg3.1 as a cellular marker to identify neuronal ensembles and a molecular probe to modulate circuit functions. These studies have demonstrated that the transcription of Arc is activated in selective groups of frontal cortical neurons in response to specific behavioral tasks. Arc expression regulates the persistent firing of individual neurons and predicts the consolidation of neuronal ensembles during repeated learning. Therefore, the Arc pathway represents a prototypical example of activity-dependent genetic feedback regulation of neuronal ensembles. The activation of this pathway in the frontal cortex starts during early postnatal development and requires dopaminergic (DA) input. Conversely, genetic disruption of Arc leads to a hypoactive mesofrontal dopamine circuit and its related cognitive deficit. This mutual interaction suggests an auto-regulatory mechanism to amplify the impact of neuromodulators and activity-regulated genes during postnatal development. Such a mechanism may contribute to the association of mutations in dopamine and Arc pathways with neurodevelopmental psychiatric disorders. As the mesofrontal dopamine circuit shows extensive activity-dependent developmental plasticity, activity-guided modulation of DA projections or Arc ensembles during development may help to repair circuit deficits related to neuropsychiatric disorders. PMID:27999532

  18. Genetic Feedback Regulation of Frontal Cortical Neuronal Ensembles Through Activity-Dependent Arc Expression and Dopaminergic Input.

    PubMed

    Mastwal, Surjeet; Cao, Vania; Wang, Kuan Hong

    2016-01-01

    Mental functions involve coordinated activities of specific neuronal ensembles that are embedded in complex brain circuits. Aberrant neuronal ensemble dynamics is thought to form the neurobiological basis of mental disorders. A major challenge in mental health research is to identify these cellular ensembles and determine what molecular mechanisms constrain their emergence and consolidation during development and learning. Here, we provide a perspective based on recent studies that use activity-dependent gene Arc/Arg3.1 as a cellular marker to identify neuronal ensembles and a molecular probe to modulate circuit functions. These studies have demonstrated that the transcription of Arc is activated in selective groups of frontal cortical neurons in response to specific behavioral tasks. Arc expression regulates the persistent firing of individual neurons and predicts the consolidation of neuronal ensembles during repeated learning. Therefore, the Arc pathway represents a prototypical example of activity-dependent genetic feedback regulation of neuronal ensembles. The activation of this pathway in the frontal cortex starts during early postnatal development and requires dopaminergic (DA) input. Conversely, genetic disruption of Arc leads to a hypoactive mesofrontal dopamine circuit and its related cognitive deficit. This mutual interaction suggests an auto-regulatory mechanism to amplify the impact of neuromodulators and activity-regulated genes during postnatal development. Such a mechanism may contribute to the association of mutations in dopamine and Arc pathways with neurodevelopmental psychiatric disorders. As the mesofrontal dopamine circuit shows extensive activity-dependent developmental plasticity, activity-guided modulation of DA projections or Arc ensembles during development may help to repair circuit deficits related to neuropsychiatric disorders.

  19. Activity-dependent peptidergic modulation of the plateau-generating neuron B64 in the feeding network of Aplysia.

    PubMed

    Koh, Hae-Young; Weiss, Klaudiusz R

    2007-02-01

    Many behaviors display various forms of activity-dependent plasticity. An example of such plasticity is the progressive shortening of the duration of protraction phase of feeding responses of Aplysia that occurs when feeding responses are repeatedly elicited. A similar protraction-duration shortening is observed in isolated ganglia of Aplysia when feeding-like motor programs are elicited through a prolonged stimulation of the command-like neuron CBI-2. Here, we investigate a cellular mechanism that may underlie this activity-dependent shortening of protraction duration of feeding motor programs. CBI-2 contains two neuropeptides, CP2 and FCAP. Previous work showed that CP2 shortens protraction duration of CBI-2 elicited programs. We show here that the same is true for FCAP. We also show that both CP2 and FCAP modulated the biophysical properties of a plateau-generating neuron, B64, that plays an important role in terminating the protraction phase of feeding motor programs. We find that prestimulation of CBI-2, as well as superfusion of CP2 and FCAP, lowered the threshold for activation of the plateau potential in B64. The threshold-lowering actions of CBI-2 prestimulation were occluded by superfusion of FCAP and CP2. Furthermore, at elevated temperature, conditions under which peptide release is prevented in Aplysia, prestimulation of CBI-2 does not lower the plateau-potential threshold, whereas superfusion of CP2 and FCAP does. Our findings are consistent with the hypothesis that peptides released from CBI-2 lower the threshold for activation of plateau potential in B64, thereby contributing to the shortening of protraction duration when CBI-2 is repeatedly activated.

  20. Activity-dependent Notch signalling in the hypothalamic-neurohypophysial system of adult mouse brains.

    PubMed

    Mannari, T; Miyata, S

    2014-08-01

    Notch signalling has a key role in cell fate specification in developing brains; however, recent studies have shown that Notch signalling also participates in the regulation of synaptic plasticity in adult brains. In the present study, we examined the expression of Notch3 and Delta-like ligand 4 (DLL4) in the hypothalamic-neurohypophysial system (HNS) of the adult mouse. The expression of DLL4 was higher in the supraoptic nucleus (SON) and paraventricular nucleus (PVN) compared to adjacent hypothalamic regions. Double-labelling immunohistochemistry using vesicular GABA transporter and glutamate transporter revealed that DLL4 was localised at a subpopulation of excitatory and inhibitory axonal boutons against somatodendrites of arginine vasopressin (AVP)- and oxytocin (OXT)-containing magnocellular neurones. In the neurohypophysis (NH), the expression of DLL4 was seen at OXT- but not AVP-containing axonal terminals. The expression of Notch3 was seen at somatodendrites of AVP- and OXT-containing magnocellular neurones in the SON and PVN and at pituicytes in the NH. Chronic physiological stimulation by salt loading, which remarkably enhances the release of AVP and OXT, decreased the number of DLL4-immunoreactive axonal boutons in the SON and PVN. Moreover, chronic and acute osmotic stimulation promoted proteolytic cleavage of Notch3 to yield the intracellular fragments of Notch3 in the HNS. Thus, the present study demonstrates activity-dependent reduction of DLL4 expression and proteolytic cleavage of Notch3 in the HNS, suggesting that Notch signalling possibly participates in synaptic interaction in the hypothalamic nuclei and neuroglial interaction in the NH.

  1. Activation-Dependent Rapid Postsynaptic Clustering of Glycine Receptors in Mature Spinal Cord Neurons

    PubMed Central

    Eto, Kei; Murakoshi, Hideji; Watanabe, Miho; Hirata, Hiromi; Moorhouse, Andrew J.; Ishibashi, Hitoshi

    2017-01-01

    Abstract Inhibitory synapses are established during development but continue to be generated and modulated in strength in the mature nervous system. In the spinal cord and brainstem, presynaptically released inhibitory neurotransmitter dominantly switches from GABA to glycine during normal development in vivo. While presynaptic mechanisms of the shift of inhibitory neurotransmission are well investigated, the contribution of postsynaptic neurotransmitter receptors to this shift is not fully elucidated. Synaptic clustering of glycine receptors (GlyRs) is regulated by activation-dependent depolarization in early development. However, GlyR activation induces hyperpolarization after the first postnatal week, and little is known whether and how presynaptically released glycine regulates postsynaptic receptors in a depolarization-independent manner in mature developmental stage. Here we developed spinal cord neuronal culture of rodents using chronic strychnine application to investigate whether initial activation of GlyRs in mature stage could change postsynaptic localization of GlyRs. Immunocytochemical analyses demonstrate that chronic blockade of GlyR activation until mature developmental stage resulted in smaller clusters of postsynaptic GlyRs that could be enlarged upon receptor activation for 1 h in the mature stage. Furthermore, live cell-imaging techniques show that GlyR activation decreases its lateral diffusion at synapses, and this phenomenon is dependent on PKC, but neither Ca2+ nor CaMKII activity. These results suggest that the GlyR activation can regulate receptor diffusion and cluster size at inhibitory synapses in mature stage, providing not only new insights into the postsynaptic mechanism of shifting inhibitory neurotransmission but also the inhibitory synaptic plasticity in mature nervous system. PMID:28197549

  2. Drawing dependent structures, mechanical properties and cyclization behaviors of polyacrylonitrile and polyacrylonitrile/carbon nanotube composite fibers prepared by plasticized spinning.

    PubMed

    Li, Xiang; Qin, Aiwen; Zhao, Xinzhen; Liu, Dapeng; Wang, Haiye; He, Chunju

    2015-09-14

    Drawing to change the structural properties and cyclization behaviors of the polyacrylonitrile (PAN) chains in crystalline and amorphous regions is carried out on PAN and PAN/carbon nanotube (CNT) composite fibers. Various characterization methods including Fourier transform infrared spectroscopy, differential scanning calorimetry, X-ray diffraction and thermal gravimetric analysis are used to monitor the structural evolution and cyclization behaviors of the fibers. With an increase of the draw ratio during the plasticized spinning process, the structural parameters of the fibers, i.e. crystallinity and planar zigzag conformation, are decreased at first, and then increased, which are associated with the heat exchange rate and the oriented-crystallization rate. A possible mechanism for plasticized spinning is proposed to explain the changing trends of crystallinity and planar zigzag conformation. PAN and PAN/CNT fibers exhibit various cyclization behaviors induced by drawing, e.g., the initiation temperature for the cyclization (Ti) of PAN fibers is increased with increasing draw ratio, while Ti of PAN/CNT fibers is decreased. Drawing also facilitates cyclization and lowers the percentage of β-amino nitrile for PAN/CNT fibers during the stabilization.

  3. Mechanistic insights into neurotransmitter release and presynaptic plasticity from the crystal structure of Munc13-1 C1C2BMUN

    PubMed Central

    Xu, Junjie; Camacho, Marcial; Xu, Yibin; Esser, Victoria; Liu, Xiaoxia; Trimbuch, Thorsten; Pan, Yun-Zu; Ma, Cong; Tomchick, Diana R; Rosenmund, Christian; Rizo, Josep

    2017-01-01

    Munc13–1 acts as a master regulator of neurotransmitter release, mediating docking-priming of synaptic vesicles and diverse presynaptic plasticity processes. It is unclear how the functions of the multiple domains of Munc13–1 are coordinated. The crystal structure of a Munc13–1 fragment including its C1, C2B and MUN domains (C1C2BMUN) reveals a 19.5 nm-long multi-helical structure with the C1 and C2B domains packed at one end. The similar orientations of the respective diacyglycerol- and Ca2+-binding sites of the C1 and C2B domains suggest that the two domains cooperate in plasma-membrane binding and that activation of Munc13–1 by Ca2+ and diacylglycerol during short-term presynaptic plasticity are closely interrelated. Electrophysiological experiments in mouse neurons support the functional importance of the domain interfaces observed in C1C2BMUN. The structure imposes key constraints for models of neurotransmitter release and suggests that Munc13–1 bridges the vesicle and plasma membranes from the periphery of the membrane-membrane interface. DOI: http://dx.doi.org/10.7554/eLife.22567.001 PMID:28177287

  4. Effect of various kinds of severe plastic deformation on the structure and electromechanical properties of precipitation-strengthened CuCrZr alloy

    NASA Astrophysics Data System (ADS)

    Belyaeva, A. I.; Galuza, A. A.; Khaimovich, P. A.; Kolenov, I. V.; Savchenko, A. A.; Solodovchenko, S. I.; Shul'gin, N. A.

    2016-11-01

    The effect of various kinds of severe plastic deformation (equal-channel angular pressing and quasi-hydrostatic extrusion at 77 and 300 K) on the structural formation of precipitation-strengthened CuCrZr alloy has been studied. A combination of experimental methods has been used. Sputtering by deuterium ions was used as the tool for the layer-by-layer study of the alloy structure. The difference between the sputtering yields of the matrix (copper) and precipitates (Cr and Zr) allowed us to visualize the alloy structure to a total depth of 0.5-1 μm. The effect of severe plastic deformation on the precipitate distribution is considered. It has been shown that the main peculiarity of the microstructure is related to the high density of precipitates enriched in chromium, which completely determine the surface roughness. Their distribution is not related to the grain size. The combination of equal-channel angular pressing and quasi-hydrostatic extrusion was shown to lead to the increase in the microhardness of the CuCrZr alloy to 2300 MPa in the case of low-temperature quasi-hydrostatic extrusion (at 77 K) and to the retained high conductivity. It has been proved that the high anisotropy of precipitate shape, microhardness, and sputtering yield of the CuCrZr alloy is determined by equal-channel angular pressing.

  5. Comparative Analysis of Zones of Plastic Strain, Dynamic Crack Resistance, Structure and Micromechanisms of Crack Propagation in Structural Steels 09G2S, 25 and 40 in High-Toughness Condition

    NASA Astrophysics Data System (ADS)

    Simonov, M. Yu.; Georgiev, M. N.; Shaimanov, G. S.; Simonov, Yu. N.; Zaporozhan, R. S.

    2016-05-01

    Comparative analysis of zones of plastic strain, dynamic crack resistance, structure, and micromechanisms of crack propagation in structural steels 09G2S, 25 and 40 in high-toughness condition is performed. The structure, the micromechanisms of crack growth, and the dynamic crack resistance of steels 09G2S, 25 and 40 are studied. Complete zones of plastic stain (CPSZ) under fracture surfaces are plotted after quenching and high tempering at 650°C. The levels of microhardness in the CPSZ are mapped for specially-designed specimens with additional 1-mm-deep side notches and relative crack length of 0.4 - 0.5. The sizes of the zones of plastic strain in the starting region are determined. Special features of the distribution of microhardness in local volumes of the CPSZ are determined. The structure under fracture surfaces of steels 09G2S, 25 and 40 is studied over the whole of the path of propagation of a dynamic crack.

  6. Plastic bronchitis

    PubMed Central

    Singhi, Anil Kumar; Vinoth, Bharathi; Kuruvilla, Sarah; Sivakumar, Kothandam

    2015-01-01

    Plastic bronchitis, a rare but serious clinical condition, commonly seen after Fontan surgeries in children, may be a manifestation of suboptimal adaptation to the cavopulmonary circulation with unfavorable hemodynamics. They are ominous with poor prognosis. Sometimes, infection or airway reactivity may provoke cast bronchitis as a two-step insult on a vulnerable vascular bed. In such instances, aggressive management leads to longer survival. This report of cast bronchitis discusses its current understanding. PMID:26556975

  7. An X-ray absorption spectroscopy investigation of the local atomic structure in Cu-Ni-Si alloy after severe plastic deformation and ageing

    NASA Astrophysics Data System (ADS)

    Azzeddine, H.; Harfouche, M.; Hennet, L.; Thiaudiere, D.; Kawasaki, M.; Bradai, D.; Langdon, T. G.

    2015-08-01

    The local atomic structure of Cu-Ni-Si alloy after severe plastic deformation (SPD) processing and the decomposition of supersaturated solid solution upon annealing were investigated by means of X-ray absorption spectroscopy. The coordination number and interatomic distances were obtained by analyzing experimental extend X-ray absorption fine structure data collected at the Ni K-edge. Results indicate that the environment of Ni atoms in Cu-Ni-Si alloy is strongly influenced by the deformation process. Moreover, ageing at 973 K affects strongly the atomic structure around the Ni atoms in Cu-Ni-Si deformed by equal channel angular pressing and high pressure torsion. This influence is discussed in terms of changes and decomposition features of the Cu-Ni-Si solid solution.

  8. A multi-surface plasticity model for clear wood and its application to the finite element analysis of structural details

    NASA Astrophysics Data System (ADS)

    Mackenzie-Helnwein, P.; Eberhardsteiner, J.; Mang, H. A.

    Recent biaxial experiments on spruce wood show that consideration of an elliptic failure surface according to Tsai and Wu, and of an elastic model for stress states within this envelope, gives an insufficient description of the mechanical behavior. As compression perpendicular to grain occurs, a nonlinear stress path results from a proportional biaxial strain path. Moreover, a phenomenological single-surface model does not permit easy identification of failure modes and thus renders the description of different post-failure mechanisms very difficult. Investigation of characteristic samples for various biaxial loading conditions enables the identification of four basic mechanisms covering the behavior of wood under plane stress conditions. The experimentally observed mechanical behavior will be described by means of a multi-surface plasticity model. It consists of four surfaces representing four basic failure modes. The first is a modified tension cut-off for the description of fiber rupture. The second is a mixed mode radial tension-shear model by Weihe applied to the perpendicular to grain direction. The third is an extension of the authors' prior model for perpendicular to grain compression, and the fourth surface covers the compressive failure parallel to grain. The model represents the orthotropic multi-surface elasto-plastic material clear wood. The aim of this paper is to present and discuss selected experimental data from biaxial tests with respect to distinct failure modes, and to develop an orthotropic plasticity model for its mathematical description. Since available experimental data cover only plane stress in the LR-plane,, both orthotropic failure and yield surfaces, respectively, are restricted to this case.

  9. Locality and Word Order in Active Dependency Formation in Bangla

    PubMed Central

    Chacón, Dustin A.; Imtiaz, Mashrur; Dasgupta, Shirsho; Murshed, Sikder M.; Dan, Mina; Phillips, Colin

    2016-01-01

    Research on filler-gap dependencies has revealed that there are constraints on possible gap sites, and that real-time sentence processing is sensitive to these constraints. This work has shown that comprehenders have preferences for potential gap sites, and immediately detect when these preferences are not met. However, neither the mechanisms that select preferred gap sites nor the mechanisms used to detect whether these preferences are met are well-understood. In this paper, we report on three experiments in Bangla, a language in which gaps may occur in either a pre-verbal embedded clause or a post-verbal embedded clause. This word order variation allows us to manipulate whether the first gap linearly available is contained in the same clause as the filler, which allows us to dissociate structural locality from linear locality. In Experiment 1, an untimed ambiguity resolution task, we found a global bias to resolve a filler-gap dependency with the first gap linearly available, regardless of structural hierarchy. In Experiments 2 and 3, which use the filled-gap paradigm, we found sensitivity to disruption only when the blocked gap site is both structurally and linearly local, i.e., the filler and the gap site are contained in the same clause. This suggests that comprehenders may not show sensitivity to the disruption of all preferred gap resolutions. PMID:27610090

  10. Locality and Word Order in Active Dependency Formation in Bangla.

    PubMed

    Chacón, Dustin A; Imtiaz, Mashrur; Dasgupta, Shirsho; Murshed, Sikder M; Dan, Mina; Phillips, Colin

    2016-01-01

    Research on filler-gap dependencies has revealed that there are constraints on possible gap sites, and that real-time sentence processing is sensitive to these constraints. This work has shown that comprehenders have preferences for potential gap sites, and immediately detect when these preferences are not met. However, neither the mechanisms that select preferred gap sites nor the mechanisms used to detect whether these preferences are met are well-understood. In this paper, we report on three experiments in Bangla, a language in which gaps may occur in either a pre-verbal embedded clause or a post-verbal embedded clause. This word order variation allows us to manipulate whether the first gap linearly available is contained in the same clause as the filler, which allows us to dissociate structural locality from linear locality. In Experiment 1, an untimed ambiguity resolution task, we found a global bias to resolve a filler-gap dependency with the first gap linearly available, regardless of structural hierarchy. In Experiments 2 and 3, which use the filled-gap paradigm, we found sensitivity to disruption only when the blocked gap site is both structurally and linearly local, i.e., the filler and the gap site are contained in the same clause. This suggests that comprehenders may not show sensitivity to the disruption of all preferred gap resolutions.

  11. Constrained Self-adaptive Solutions Procedures for Structure Subject to High Temperature Elastic-plastic Creep Effects

    NASA Technical Reports Server (NTRS)

    Padovan, J.; Tovichakchaikul, S.

    1983-01-01

    This paper will develop a new solution strategy which can handle elastic-plastic-creep problems in an inherently stable manner. This is achieved by introducing a new constrained time stepping algorithm which will enable the solution of creep initiated pre/postbuckling behavior where indefinite tangent stiffnesses are encountered. Due to the generality of the scheme, both monotone and cyclic loading histories can be handled. The presentation will give a thorough overview of current solution schemes and their short comings, the development of constrained time stepping algorithms as well as illustrate the results of several numerical experiments which benchmark the new procedure.

  12. Neural stem cells and neuro/gliogenesis in the central nervous system: understanding the structural and functional plasticity of the developing, mature, and diseased brain.

    PubMed

    Yamaguchi, Masahiro; Seki, Tatsunori; Imayoshi, Itaru; Tamamaki, Nobuaki; Hayashi, Yoshitaka; Tatebayashi, Yoshitaka; Hitoshi, Seiji

    2016-05-01

    Neurons and glia in the central nervous system (CNS) originate from neural stem cells (NSCs). Knowledge of the mechanisms of neuro/gliogenesis from NSCs is fundamental to our understanding of how complex brain architecture and function develop. NSCs are present not only in the developing brain but also in the mature brain in adults. Adult neurogenesis likely provides remarkable plasticity to the mature brain. In addition, recent progress in basic research in mental disorders suggests an etiological link with impaired neuro/gliogenesis in particular brain regions. Here, we review the recent progress and discuss future directions in stem cell and neuro/gliogenesis biology by introducing several topics presented at a joint meeting of the Japanese Association of Anatomists and the Physiological Society of Japan in 2015. Collectively, these topics indicated that neuro/gliogenesis from NSCs is a common event occurring in many brain regions at various ages in animals. Given that significant structural and functional changes in cells and neural networks are accompanied by neuro/gliogenesis from NSCs and the integration of newly generated cells into the network, stem cell and neuro/gliogenesis biology provides a good platform from which to develop an integrated understanding of the structural and functional plasticity that underlies the development of the CNS, its remodeling in adulthood, and the recovery from diseases that affect it.

  13. Diacylglycerol Kinases in the Coordination of Synaptic Plasticity

    PubMed Central

    Lee, Dongwon; Kim, Eunjoon; Tanaka-Yamamoto, Keiko

    2016-01-01

    Synaptic plasticity is activity-dependent modification of the efficacy of synaptic transmission. Although, detailed mechanisms underlying synaptic plasticity are diverse and vary at different types of synapses, diacylglycerol (DAG)-associated signaling has been considered as an important regulator of many forms of synaptic plasticity, including long-term potentiation (LTP) and long-term depression (LTD). Recent evidences indicate that DAG kinases (DGKs), which phosphorylate DAG to phosphatidic acid to terminate DAG signaling, are important regulators of LTP and LTD, as supported by the results from mice lacking specific DGK isoforms. This review will summarize these studies and discuss how specific DGK isoforms distinctly regulate different forms of synaptic plasticity at pre- and postsynaptic sites. In addition, we propose a general role of DGKs as coordinators of synaptic plasticity that make local synaptic environments more permissive for synaptic plasticity by regulating DAG concentration and interacting with other synaptic proteins. PMID:27630986

  14. Solar activity dependence of low-and mid-latitude ionosphere

    NASA Astrophysics Data System (ADS)

    Chen, Yiding; Liu, Libo; Wan, Weixing

    Solar activity dependence of low-and mid-latitude ionosphere is investigated using ionosonde and the ROCSAT-1 satellite (600 km) observations. The pattern in the solar activity varia-tion of the electron density shows significant local time, seasonal, latitudinal, and altitudinal dependences. Noontime NmF2 saturates with F107 in all seasons in low-latitude regions, while it saturates with F107 in equinoxes and local summer and linearly increases with F107 in local winter in mid-latitude regions. Nighttime NmF2 nearly increases with F107 linearly in equinox seasons and saturates with F107 in local summer, what is peculiar is that there is an amplifica-tion trend of nighttime NmF2 with F107 in local winter. We discussed the possible mechanisms which affect the solar activity variation trend of NmF2 and argued that the changes of neutral atmosphere and ionospheric dynamics are important for the solar activity variation trend of NmF2. Solar activity variations of the plasma density at 600 km present three kinds of patterns (linearity, amplification, and saturation), the pattern depends on local time, season, and lati-tude. That is different from the case at higher altitudes, e.g., 800 km, where the amplification trend prevails. In particular, saturation effect is found in the dip equator region at equinox sunset. Latitudinal distribution of the plasma density at 600 km also depends on local time, season, and solar activity level. Around sunset, a profound double-peak structure is found in the latitudinal distribution of the plasma density in solar maximum equinox and December solstice months. Solar activity dependence of the low-latitude topside ionosphere at 600 km is strongly related to the low-latitude dynamics processes.

  15. Excitation-inhibition balance in the CA3 network--neuronal specificity and activity-dependent plasticity.

    PubMed

    Treviño, Mario; Vivar, Carmen; Gutiérrez, Rafael

    2011-05-01

    Activation of the axons of the granule cells, the mossy fibers, excites pyramidal cells and interneurons in the CA3 area, which, in turn, inhibit pyramidal cells. The integration of the various inputs that converge onto CA3 cells has been studied by pharmacological dissection of either the excitatory or inhibitory components. This strategy has the disadvantage of partially isolating the recorded cell from the network, ignoring the sources and the impact of concurrent inputs. To overcome this limitation, we dissociated excitatory and inhibitory synaptic conductances by mathematical extraction techniques, and analysed the dynamics of the integration of excitatory and inhibitory inputs in pyramidal cells and stratum lucidum interneurons (Sl-Ints) of CA3. We have uncovered a shunting mechanism that decreases the responsiveness of CA3 output cells to mossy fiber input after a period of enhanced excitability. The activation of the dentate gyrus (DG) after applying a kindling-like protocol in vitro, or after producing one or several seizures in vivo, results in a graded and reversible increase of inhibitory conductances in pyramidal cells, while in Sl-Ints, an increase of excitatory conductances occurs. Thus, interneurons reach more depolarized membrane potentials on DG activation yielding a high excitatory postsynaptic potential-spike coupling, while the contrary occurs in pyramidal cells. This effective activation of feedforward inhibition is synergized by the emergence of direct DG-mediated inhibition on pyramidal cells. These factors force the synaptic conductance to peak at a potential value close to resting membrane potential, thus producing shunt inhibition and decreasing the responsiveness of CA3 output cells to mossy fiber input.

  16. The NAP motif of activity-dependent neuroprotective protein (ADNP) regulates dendritic spines through microtubule end binding proteins.

    PubMed

    Oz, S; Kapitansky, O; Ivashco-Pachima, Y; Malishkevich, A; Giladi, E; Skalka, N; Rosin-Arbesfeld, R; Mittelman, L; Segev, O; Hirsch, J A; Gozes, I

    2014-10-01

    The NAP motif of activity-dependent neuroprotective protein (ADNP) enhanced memory scores in patients suffering from mild cognitive impairment and protected activities of daily living in schizophrenia patients, while fortifying microtubule (MT)-dependent axonal transport, in mice and flies. The question is how does NAP fortify MTs? Our sequence analysis identified the MT end-binding protein (EB1)-interacting motif SxIP (SIP, Ser-Ile-Pro) in ADNP/NAP and showed specific SxIP binding sites in all members of the EB protein family (EB1-3). Others found that EB1 enhancement of neurite outgrowth is attenuated by EB2, while EB3 interacts with postsynaptic density protein 95 (PSD-95) to modulate dendritic plasticity. Here, NAP increased PSD-95 expression in dendritic spines, which was inhibited by EB3 silencing. EB1 or EB3, but not EB2 silencing inhibited NAP-mediated cell protection, which reflected NAP binding specificity. NAPVSKIPQ (SxIP=SKIP), but not NAPVAAAAQ mimicked NAP activity. ADNP, essential for neuronal differentiation and brain formation in mouse, a member of the SWI/SNF chromatin remodeling complex and a major protein mutated in autism and deregulated in schizophrenia in men, showed similar EB interactions, which were enhanced by NAP treatment. The newly identified shared MT target of NAP/ADNP is directly implicated in synaptic plasticity, explaining the breadth and efficiency of neuroprotective/neurotrophic capacities.

  17. Respiratory muscle plasticity.

    PubMed

    Rowley, Katharine L; Mantilla, Carlos B; Sieck, Gary C

    2005-07-28

    Plasticity of respiratory muscles must be considered in the context of their unique physiological demands. The continuous rhythmic activation of respiratory muscles makes them among the most active in the body. Respiratory muscles, especially the diaphragm, are non-weight-bearing, and thus, in contrast to limb muscles, are not exposed to gravitational effects. Perturbations in normal activation and load known to induce plasticity in limb muscles may not cause similar adaptations in respiratory muscles. In this review, we explore the structural and functional properties of the diaphragm muscle and their response to alterations in load and activity. Overall, relatively modest changes in diaphragm structural and functional properties occur in response to perturbations in load or activity. However, disruptions in the normal influence of phrenic innervation by frank denervation, tetrodotoxin nerve block and spinal hemisection, induce profound changes in the diaphragm, indicating the substantial trophic influence of phrenic motoneurons on diaphragm muscle.

  18. Synaptic plasticity along the sleep-wake cycle: implications for epilepsy.

    PubMed

    Romcy-Pereira, Rodrigo N; Leite, João P; Garcia-Cairasco, Norberto

    2009-01-01

    Activity-dependent changes in synaptic efficacy (i.e., synaptic plasticity) can alter the way neurons communicate and process information as a result of experience. Synaptic plasticity mechanisms involve both molecular and structural modifications that affect synaptic functioning, either enhancing or depressing neuronal transmission. They include redistribution of postsynaptic receptors, activation of intracellular signaling cascades, and formation/retraction of dendritic spines, among others. During the sleep-wake cycle, as the result of particular neurochemical and neuronal firing modes, distinct oscillatory patterns organize the activity of neuronal populations, modulating synaptic plasticity. Such modulation, for example, has been shown in the visual cortex following sleep deprivation and in the ability to induce hippocampal long-term potentiation during sleep. In epilepsy, synchronized behavioral states tend to contribute to the initiation of paroxystic discharges and are considered more epileptogenic than desynchronized states. Here, we review some of the current understandings of synaptic plasticity changes in wake and sleep states and how sleep may affect epileptic seizures.

  19. [Neuronal plasticity and gene expression].

    PubMed

    Sokolova, O O; Shtark, M B; Lisachev, P D

    2010-01-01

    Neuronal plasticity--a fundamental feature of brain--provides adequate interactions with dynamic environment. One of the most deeply investigated forms of the neuronal plasticity is a long-term potentiation (LTP)--a phenomenon underlying learning and memory. Signal paths activated during LTP converge into the nuclear of the neuron, giving rise to launch of the molecular-genetic programs, which mediate structural and functional remodeling of synapses. In the review data concerning involvement of multilevel gene expression into plastic change under neuronal activation are summarized.

  20. Patterns in the quinary structures of proteins: plasticity and inequivalence of individual molecules in helical arrays of sickle cell hemoglobin and tubulin

    SciTech Connect

    Edelstein, S.J.

    1980-10-01

    The four recognized levels of organization of protein structure (primary through quaternary) are extended to add the designation quinary structure for the interactions within helical arrays, such as found for sickle cell hemoglobin fibers of tubulin units in microtubules. For sickle cell hemoglobin the main quinary structure is a 14-filament fiber, with a number of other minor forms also encountered. Degenerate forms of the 14-filament fibers can be characterized that lack specific pairs of filaments; evidence is presented which suggests an overall organization of the 14 filaments in pairs, with particular pairs aligned in an antiparallel orientation. For tubulin, a range of quinary structures can be detected depending on the number of protofilaments and whether adjacent protofilaments composed of alternating ..cap alpha..- and ..beta..-subunits are aligned with contacts between like or unlike subunits and with parallel or antiparallel polarity. Thus, in contrast to quarternary structure, which generally involves a fixed number of subunits, the quinary structures of proteins can exhibit marked plasticity and inequivalence in the juxtaposition of constituent molecules.

  1. The short-time structural plasticity of dendritic spines is altered in a model of Rett syndrome.

    PubMed

    Landi, Silvia; Putignano, Elena; Boggio, Elena Maria; Giustetto, Maurizio; Pizzorusso, Tommaso; Ratto, Gian Michele

    2011-01-01

    The maturation of excitatory transmission comes about through a developmental period in which dendritic spines are highly motile and their number, form and size are rapidly changing. Surprisingly, although these processes are crucial for the formation of cortical circuitry, little is known about possible alterations of these processes in brain disease. By means of acute in vivo 2-photon imaging we show that the dynamic properties of dendritic spines of layer V cortical neurons are deeply affected in a mouse model of Rett syndrome (RTT) at a time around P25 when the neuronal phenotype of the disease is still mild. Then, we show that 24h after a subcutaneous injection of IGF-1 spine dynamics is restored. Our study demonstrates that spine dynamics in RTT mice is severely impaired early during development and suggest that treatments for RTT should be started very early in order to reestablish a normal period of spine plasticity.

  2. Orientation relationship, plasticity, twin relationship, and interfacial structure of the ???' isothermal martensitic transformation in Pu-Ga alloys

    SciTech Connect

    Moore, K; Krenn, C; Wall, M; Schwartz, A

    2006-01-24

    The orientation relationship, habit plane, parent-product interface at the atomic level, twin relationship, and plastic deformation resulting from the {delta} {yields} {alpha}{prime} isothermal martensitic transformation in Pu-Ga alloys are examined using optical microscopy, transmission electron microscopy, and finite element calculations. The {delta} {yields} {alpha}{prime} transformation exhibits a {approx}20% volume collapse when the face-centered cubic {delta} phase transforms to the monoclinic {alpha}{prime} phase, which results in unique and intriguing crystallography and morphology. Here, we show that the orientation relationship is very close to that previously reported by Zocco et al. (1990), but has small rotational misalignments between the two phases both parallel and perpendicular to the [110]{sub {delta}} {parallel}[100]{sub {alpha}{prime}} direction. The amount of plastic deformation is exceedingly large due to the {approx}20% volume collapse and transmission electron microscopy is used to quantify the difference in dislocation density between untransformed {delta}-matrix and regions of {delta} adjacent to the transformed {alpha}{prime}. The twins contained in {alpha}{prime} plates are shown to have a (205){sub {alpha}} orientation as the lattice invariant deformation and are found to be composed of two alternating variants that share a common <020>{sub {alpha}{prime}} direction, but differ by a 60 degree rotation about <020>{sub {alpha}{prime}}. A combination of electron diffraction and optical microscopy has been employed to examine the macroscopic habit plane and the analysis suggests that a large fraction of the observed habit planes are on or near {l_brace}111{r_brace}{sub {delta}}. Finally, high resolution transmission electron microscopy reveals that the interface is faceted on {l_brace}111{r_brace}{sub {delta}}, exhibiting a series of terrace and ledges.

  3. Molecular kinesis in cellular function and plasticity.

    PubMed

    Tiedge, H; Bloom, F E; Richter, D

    2001-06-19

    Intracellular transport and localization of cellular components are essential for the functional organization and plasticity of eukaryotic cells. Although the elucidation of protein transport mechanisms has made impressive progress in recent years, intracellular transport of RNA remains less well understood. The National Academy of Sciences Colloquium on Molecular Kinesis in Cellular Function and Plasticity therefore was devised as an interdisciplinary platform for participants to discuss intracellular molecular transport from a variety of different perspectives. Topics covered at the meeting included RNA metabolism and transport, mechanisms of protein synthesis and localization, the formation of complex interactive protein ensembles, and the relevance of such mechanisms for activity-dependent regulation and synaptic plasticity in neurons. It was the overall objective of the colloquium to generate momentum and cohesion for the emerging research field of molecular kinesis.

  4. A Lesson Plan to Develop Structured Discussion of the Benefits and Disadvantages of Selected Plastics Using the Product-Testing Method

    ERIC Educational Resources Information Center

    Burmeister, Mareike; Eilks, Ingo

    2014-01-01

    People use many different products made from plastics every day. But conventional plastics such as polyvinyl chloride (PVC) do not always have a good reputation in society at large. Bioplastics such as thermoplastic starch (TPS) promise to be better alternatives but are they really better than conventional plastics? This article presents a new…

  5. A Possible Role of Prolonged Whirling Episodes on Structural Plasticity of the Cortical Networks and Altered Vertigo Perception: The Cortex of Sufi Whirling Dervishes

    PubMed Central

    Cakmak, Yusuf O.; Ekinci, Gazanfer; Heinecke, Armin; Çavdar, Safiye

    2017-01-01

    Although minutes of a spinning episode may induce vertigo in the healthy human, as a result of a possible perceptional plasticity, Sufi Whirling Dervishes (SWDs) can spin continuously for an hour without a vertigo perception.This unique long term vestibular system stimulation presents a potential human model to clarify the cortical networks underlying the resistance against vertigo. This study, therefore, aimed to investigate the potential structural cortical plasticity in SWDs. Magnetic resonance imaging (MRI) of 10 SWDs and 10 controls were obtained, using a 3T scanner. Cortical thickness in the whole cortex was calculated. Results demonstrated significantly thinner cortical areas for SWD subjects compared with the control group in the hubs of the default mode network (DMN), as well as in the motion perception and discrimination areas including the right dorsolateral prefrontal cortex (DLPFC), the right lingual gyrus and the left visual area 5 (V5)/middle temporal (MT) and the left fusiform gyrus. In conclusion, this is the first report that warrants the potential relationship of the motion/body perception related cortical networks and the prolonged term of whirling ability without vertigo or dizziness. PMID:28167905

  6. Anaerobic digestion of municipal solid waste composed of food waste, wastepaper, and plastic in a single-stage system: performance and microbial community structure characterization.

    PubMed

    Wan, Shungang; Sun, Lei; Douieb, Yaniv; Sun, Jian; Luo, Wensui

    2013-10-01

    The performance of municipal organic solid waste anaerobic digestion was investigated using a single-stage bioreactor, and the microbial community structures were characterized during the digestion. The results showed that the biogas and methane production rates were 592.4 and 370.1L/kg with volatile solid added at the ratio of 2:1:1 for food waste, wastepaper, and plastic based on dry weight. The methane volume concentration fluctuated between 44.3% and 75.4% at steady stage. Acetic acid, propionic acid, and butyric acid were the major volatile fatty acids produced during the digestion process. The anaerobic process was not inhibited by the accumulation of ammonia and free ammonia. The bacterial community was found to consist of at least 21 bands of bacteria and 12 bands of archaea at the steady state. All of the results indicated that the mixture of food waste, wastepaper, and plastic could be efficiently co-digested using the anaerobic digestion system.

  7. A dynamic model of plant growth with interactions between development and functional mechanisms to study plant structural plasticity related to trophic competition

    PubMed Central

    Mathieu, A.; Cournède, P. H.; Letort, V.; Barthélémy, D.; de Reffye, P.

    2009-01-01

    Background and Aims The strong influence of environment and functioning on plant organogenesis has been well documented by botanists but is poorly reproduced in most functional–structural models. In this context, a model of interactions is proposed between plant organogenesis and plant functional mechanisms. Methods The GreenLab model derived from AMAP models was used. Organogenetic rules give the plant architecture, which defines an interconnected network of organs. The plant is considered as a collection of interacting ‘sinks’ that compete for the allocation of photosynthates coming from ‘sources’. A single variable characteristic of the balance between sources and sinks during plant growth controls different events in plant development, such as the number of branches or the fruit load. Key Results Variations in the environmental parameters related to light and density induce changes in plant morphogenesis. Architecture appears as the dynamic result of this balance, and plant plasticity expresses itself very simply at different levels: appearance of branches and reiteration, number of organs, fructification and adaptation of ecophysiological characteristics. Conclusions The modelling framework serves as a tool for theoretical botany to explore the emergence of specific morphological and architectural patterns and can help to understand plant phenotypic plasticity and its strategy in response to environmental changes. PMID:19297366

  8. Glutamatergic synapses are structurally and biochemically complex because of multiple plasticity processes: long-term potentiation, long-term depression, short-term potentiation and scaling.

    PubMed

    Lisman, John

    2017-03-05

    Synapses are complex because they perform multiple functions, including at least six mechanistically different forms of plasticity. Here, I comment on recent developments regarding these processes. (i) Short-term potentiation (STP), a Hebbian process that requires small amounts of synaptic input, appears to make strong contributions to some forms of working memory. (ii) The rules for long-term potentiation (LTP) induction in CA3 have been clarified: induction does not depend obligatorily on backpropagating sodium spikes but, rather, on dendritic branch-specific N-methyl-d-aspartate (NMDA) spikes. (iii) Late LTP, a process that requires a dopamine signal (and is therefore neoHebbian), is mediated by trans-synaptic growth of the synapse, a growth that occurs about an hour after LTP induction. (iv) LTD processes are complex and include both homosynaptic and heterosynaptic forms. (v) Synaptic scaling produced by changes in activity levels are not primarily cell-autonomous, but rather depend on network activity. (vi) The evidence for distance-dependent scaling along the primary dendrite is firm, and a plausible structural-based mechanism is suggested.Ideas about the mechanisms of synaptic function need to take into consideration newly emerging data about synaptic structure. Recent super-resolution studies indicate that glutamatergic synapses are modular (module size 70-80 nm), as predicted by theoretical work. Modules are trans-synaptic structures and have high concentrations of postsynaptic density-95 (PSD-95) and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor. These modules function as quasi-independent loci of AMPA-mediated transmission and may be independently modifiable, suggesting a new understanding of quantal transmission.This article is part of the themed issue 'Integrating Hebbian and homeostatic plasticity.'

  9. Activity-Regulated Genes as Mediators of Neural Circuit Plasticity

    PubMed Central

    Leslie, Jennifer H.; Nedivi, Elly

    2011-01-01

    Modifications of neuronal circuits allow the brain to adapt and change with experience. This plasticity manifests during development and throughout life, and can be remarkably long lasting. Many electrophysiological and molecular mechanisms are common to the seemingly diverse types of activity-dependent functional adaptation that take place during developmental critical periods, learning and memory, and alterations to sensory map representations in the adult. Experience-dependent plasticity is triggered when neuronal excitation activates cellular signaling pathways from the synapse to the nucleus that initiate new programs of gene expression. The protein products of activity-regulated genes then work via a diverse array of cellular mechanisms to modify neuronal functional properties. They fine-tune brain circuits by strengthening or weakening synaptic connections or by altering synapse numbers. Their effects are further modulated by posttranscriptional regulatory mechanisms, often also dependent on activity, that control activity-regulated gene transcript and protein function. Thus, the cellular response to neuronal activity integrates multiple tightly coordinated mechanisms to precisely orchestrate long-lasting, functional and structural changes in brain circuits. PMID:21601615

  10. Binding of TFIIIC to SINE Elements Controls the Relocation of Activity-Dependent Neuronal Genes to Transcription Factories

    PubMed Central

    Crepaldi, Luca; Policarpi, Cristina; Coatti, Alessandro; Sherlock, William T.; Jongbloets, Bart C.; Down, Thomas A.; Riccio, Antonella

    2013-01-01

    In neurons, the timely and accurate expression of genes in response to synaptic activity relies on the interplay between epigenetic modifications of histones, recruitment of regulatory proteins to chromatin and changes to nuclear structure. To identify genes and regulatory elements responsive to synaptic activation in vivo, we performed a genome-wide ChIPseq analysis of acetylated histone H3 using somatosensory cortex of mice exposed to novel enriched environmental (NEE) conditions. We discovered that Short Interspersed Elements (SINEs) located distal to promoters of activity-dependent genes became acetylated following exposure to NEE and were bound by the general transcription factor TFIIIC. Importantly, under depolarizing conditions, inducible genes relocated to transcription factories (TFs), and this event was controlled by TFIIIC. Silencing of the TFIIIC subunit Gtf3c5 in non-stimulated neurons induced uncontrolled relocation to TFs and transcription of activity-dependent genes. Remarkably, in cortical neurons, silencing of Gtf3c5 mimicked the effects of chronic depolarization, inducing a dramatic increase of both dendritic length and branching. These findings reveal a novel and essential regulatory function of both SINEs and TFIIIC in mediating gene relocation and transcription. They also suggest that TFIIIC may regulate the rearrangement of nuclear architecture, allowing the coordinated expression of activity-dependent neuronal genes. PMID:23966877

  11. Respiratory muscle plasticity.

    PubMed

    Gransee, Heather M; Mantilla, Carlos B; Sieck, Gary C

    2012-04-01

    Muscle plasticity is defined as the ability of a given muscle to alter its structural and functional properties in accordance with the environmental conditions imposed on it. As such, respiratory muscle is in a constant state of remodeling, and the basis of muscle's plasticity is its ability to change protein expression and resultant protein balance in response to varying environmental conditions. Here, we will describe the changes of respiratory muscle imposed by extrinsic changes in mechanical load, activity, and innervation. Although there is a large body of literature on the structural and functional plasticity of respiratory muscles, we are only beginning to understand the molecular-scale protein changes that contribute to protein balance. We will give an overview of key mechanisms regulating protein synthesis and protein degradation, as well as the complex interactions between them. We suggest future application of a systems biology approach that would develop a mathematical model of protein balance and greatly improve treatments in a variety of clinical settings related to maintaining both muscle mass and optimal contractile function of respiratory muscles.

  12. A light-stimulated synaptic transistor with synaptic plasticity and memory functions based on InGaZnOx-Al2O3 thin film structure

    NASA Astrophysics Data System (ADS)

    Li, H. K.; Chen, T. P.; Liu, P.; Hu, S. G.; Liu, Y.; Zhang, Q.; Lee, P. S.

    2016-06-01

    In this work, a synaptic transistor based on the indium gallium zinc oxide (IGZO)-aluminum oxide (Al2O3) thin film structure, which uses ultraviolet (UV) light pulses as the pre-synaptic stimulus, has been demonstrated. The synaptic transistor exhibits the behavior of synaptic plasticity like the paired-pulse facilitation. In addition, it also shows the brain's memory behaviors including the transition from short-term memory to long-term memory and the Ebbinghaus forgetting curve. The synapse-like behavior and memory behaviors of the transistor are due to the trapping and detrapping processes of the holes, which are generated by the UV pulses, at the IGZO/Al2O3 interface and/or in the Al2O3 layer.

  13. Nontargeted multicomponent analytical screening of plastic food contact materials using fast interpretation of deliverables via expert structure-activity relationship software.

    PubMed

    Rothenbacher, Thorsten; Schwack, Wolfgang

    2009-01-01

    Plastic packaging materials may release compounds into packed foodstuffs. To identify potential migrants of toxicological concern, resins, and multilayer foils (mainly polyethylene) intended for the production of food contact materials were extracted and analyzed by GC/mass spectrometry. To identify even compounds of low concentrations, AMDIS software was used and data evaluation was safeguarded by the Kovats retention index (RI) system. In this way, 46 compounds were identified as possible migrants. The expert structure-activity relationship software DEREK for Windows was utilized to evaluate all identified substances in terms of carcinogenicity, genotoxicity, thyroid toxicity, and miscellaneous endpoints for humans. Additionally, a literature search for these compounds was performed with Sci-Finder, but relevant data were missing for 28 substances. Seven compounds with adverse toxicological effects were identified. In addition, the RIs of 24 commercial additive standards, measured with a GC capillary column of intermediate polarity, are given.

  14. New approach to the boundary-parallel plastic / viscous diapiric flow patterns in the curvilinear boundary zones: an implication for structural geology studies

    NASA Astrophysics Data System (ADS)

    Sarkarinejad, Khalil

    2010-05-01

    New approach to the boundary-parallel plastic / viscous diapiric flow patterns in the curvilinear boundary zones: an implication for structural geology studies Khalil Sarkarinejad and Abdolreza Partabian Department of Earth Sciences, College of Sciences, Shiraz University, Shiraz, Iran (Sarkarinejad@geology.susc.ac.ir). In the oceanic diverging away plates, the asthenospheric flow at solidus high-temperature conditions typically produces mineral foliations and lineations in peridotites. Foliation and lineation of mantle are defined by preferred flattening and alignment of olivine, pyroxene and spinel. In the areas with steep foliations trajectories which are associated with the steeply plunging stretching lineation trajectories, reflecting localized vertical flow and has been related to mantle diapir. The mantle flow patterns are well documented through detail structural mapping of the Neyriz ophiolite along the Zagros inclined dextral transpression and Oman ophiolite. Such models of the diverging asthenaspheric mantle flow and formation of mantle diapir are rarely discussed and paid any attention in the mathematical models of transpressional deformation in converging continental crusts. Systematic measurements of the mineral preferred orientations and construction of the foliation and lineation trajectories of the Zagros high-strain zone reveal two diapers with the shape of the inclined NW-SE boundary-parallel semi-ellipses shape and one rotated asymmetric diapir. These diapers made of quartzo-feldspathic gneiss and garnet amphibolite core with phyllite, phyllonite, muscovite schist and deformed conglomerate as a cover sequences. These boundary-parallel and rotated diapirs are formed by the interaction of Afro-Arabian lower to middle continental detachment and hot subdacting Tethyan oceanic crust, due to increasing effective pressure and temperature. The plastic/viscous gneissic diapers were squeezed between in Zagros transpression curvilinear boundary zones in an

  15. Effects of bursting dynamic features on the generation of multi-clustered structure of neural network with symmetric spike-timing-dependent plasticity learning rule.

    PubMed

    Liu, Hui; Song, Yongduan; Xue, Fangzheng; Li, Xiumin

    2015-11-01

    In this paper, the generation of multi-clustered structure of self-organized neural network with different neuronal firing patterns, i.e., bursting or spiking, has been investigated. The initially all-to-all-connected spiking neural network or bursting neural network can be self-organized into clustered structure through the symmetric spike-timing-dependent plasticity learning for both bursting and spiking neurons. However, the time consumption of this clustering procedure of the burst-based self-organized neural network (BSON) is much shorter than the spike-based self-organized neural network (SSON). Our results show that the BSON network has more obvious small-world properties, i.e., higher clustering coefficient and smaller shortest path length than the SSON network. Also, the results of larger structure entropy and activity entropy of the BSON network demonstrate that this network has higher topological complexity and dynamical diversity, which benefits for enhancing information transmission of neural circuits. Hence, we conclude that the burst firing can significantly enhance the efficiency of clustering procedure and the emergent clustered structure renders the whole network more synchronous and therefore more sensitive to weak input. This result is further confirmed from its improved performance on stochastic resonance. Therefore, we believe that the multi-clustered neural network which self-organized from the bursting dynamics has high efficiency in information processing.

  16. Crystal Structure of the Nephila clavipes Major Ampullate Spidroin 1A N-terminal Domain Reveals Plasticity at the Dimer Interface.

    PubMed

    Atkison, James H; Parnham, Stuart; Marcotte, William R; Olsen, Shaun K

    2016-09-02

    Spider dragline silk is a natural polymer harboring unique physical and biochemical properties that make it an ideal biomaterial. Artificial silk production requires an understanding of the in vivo mechanisms spiders use to convert soluble proteins, called spidroins, into insoluble fibers. Controlled dimerization of the spidroin N-terminal domain (NTD) is crucial to this process. Here, we report the crystal structure of the Nephila clavipes major ampullate spidroin NTD dimer. Comparison of our N. clavipes NTD structure with previously determined Euprosthenops australis NTD structures reveals subtle conformational alterations that lead to differences in how the subunits are arranged at the dimer interface. We observe a subset of contacts that are specific to each ortholog, as well as a substantial increase in asymmetry in the interactions observed at the N. clavipes NTD dimer interface. These asymmetric interactions include novel intermolecular salt bridges that provide new insights into the mechanism of NTD dimerization. We also observe a unique intramolecular "handshake" interaction between two conserved acidic residues that our data suggest adds an additional layer of complexity to the pH-sensitive relay mechanism for NTD dimerization. The results of a panel of tryptophan fluorescence dimerization assays probing the importance of these interactions support our structural observations. Based on our findings, we propose that conformational selectivity and plasticity at the NTD dimer interface play a role in the pH-dependent transition of the NTD from monomer to stably associated dimer as the spidroin progresses through the silk extrusion duct.

  17. Effects of bursting dynamic features on the generation of multi-clustered structure of neural network with symmetric spike-timing-dependent plasticity learning rule

    NASA Astrophysics Data System (ADS)

    Liu, Hui; Song, Yongduan; Xue, Fangzheng; Li, Xiumin

    2015-11-01

    In this paper, the generation of multi-clustered structure of self-organized neural network with different neuronal firing patterns, i.e., bursting or spiking, has been investigated. The initially all-to-all-connected spiking neural network or bursting neural network can be self-organized into clustered structure through the symmetric spike-timing-dependent plasticity learning for both bursting and spiking neurons. However, the time consumption of this clustering procedure of the burst-based self-organized neural network (BSON) is much shorter than the spike-based self-organized neural network (SSON). Our results show that the BSON network has more obvious small-world properties, i.e., higher clustering coefficient and smaller shortest path length than the SSON network. Also, the results of larger structure entropy and activity entropy of the BSON network demonstrate that this network has higher topological complexity and dynamical diversity, which benefits for enhancing information transmission of neural circuits. Hence, we conclude that the burst firing can significantly enhance the efficiency of clustering procedure and the emergent clustered structure renders the whole network more synchronous and therefore more sensitive to weak input. This result is further confirmed from its improved performance on stochastic resonance. Therefore, we believe that the multi-clustered neural network which self-organized from the bursting dynamics has high efficiency in information processing.

  18. Effects of bursting dynamic features on the generation of multi-clustered structure of neural network with symmetric spike-timing-dependent plasticity learning rule

    SciTech Connect

    Liu, Hui; Song, Yongduan; Xue, Fangzheng; Li, Xiumin

    2015-11-15

    In this paper, the generation of multi-clustered structure of self-organized neural network with different neuronal firing patterns, i.e., bursting or spiking, has been investigated. The initially all-to-all-connected spiking neural network or bursting neural network can be self-organized into clustered structure through the symmetric spike-timing-dependent plasticity learning for both bursting and spiking neurons. However, the time consumption of this clustering procedure of the burst-based self-organized neural network (BSON) is much shorter than the spike-based self-organized neural network (SSON). Our results show that the BSON network has more obvious small-world properties, i.e., higher clustering coefficient and smaller shortest path length than the SSON network. Also, the results of larger structure entropy and activity entropy of the BSON network demonstrate that this network has higher topological complexity and dynamical diversity, which benefits for enhancing information transmission of neural circuits. Hence, we conclude that the burst firing can significantly enhance the efficiency of clustering procedure and the emergent clustered structure renders the whole network more synchronous and therefore more sensitive to weak input. This result is further confirmed from its improved performance on stochastic resonance. Therefore, we believe that the multi-clustered neural network which self-organized from the bursting dynamics has high efficiency in information processing.

  19. Manifestation of the shape-memory effect in polyetherurethane cellular plastics, fabric composites, and sandwich structures under microgravity

    NASA Astrophysics Data System (ADS)

    Babaevskii, P. G.; Kozlov, N. A.; Agapov, I. G.; Reznichenko, G. M.; Churilo, N. V.; Churilo, I. V.

    2016-09-01

    The results of experiments that were performed to test the feasibility of creating sandwich structures (consisting of thin-layer sheaths of polymer composites and a cellular polymer core) with the shapememory effect as models of the transformable components of space structures have been given. The data obtained indicate that samples of sandwich structures under microgravity conditions on board the International Space Station have recovered their shape to almost the same degree as under terrestrial conditions, which makes it possible to recommend them for creating components of transformable space structures on their basis.

  20. Plastic deformation of single crystals of WSi{sub 2} with the C11{sub b} structure

    SciTech Connect

    Ito, K.; Yano, T.; Nakamoto, T.; Inui, H.; Yamaguchi, M.

    1999-02-05

    The deformation behavior of single crystals of WSi{sub 2} has been investigated as a function of crystal orientation in the temperature range from room temperature to 1500 C in compression. Single crystals of WSi{sub 2} can be deformed only at high temperatures above 1100 C, in contrast to MoSi{sub 2} in which plastic flow is possible even at room temperature. Four slip systems, {l_brace}110{r_brace}{l_angle}111{r_angle}, {l_brace}011{r_brace}{l_angle}100{r_angle}, {l_brace}023{r_brace}{l_angle}100{r_angle} and (001){l_angle}100{r_angle}, are identified. While the former three slip systems are operative also in MoSi{sub 2}, the (001){l_angle}100{r_angle} slip is only operative in WSi{sub 2}. The (001){l_angle}100{r_angle} slip in WSi{sub 2} is the alternative to {l_brace}013{r_brace}{l_angle}331{r_angle} slip in MoSi{sub 2} since they are operative in the same orientation range. Slip on {l_brace}110{r_brace}{l_angle}331{r_angle} is hardly observed in WSi{sub 2}. The values of critical resolved shear stress (CRSS) for the commonly observed slip systems are much higher in WSi{sub 2} than in MoSi{sub 2} with the largest difference for {l_brace}110{r_brace}{l_angle}111{r_angle} slip. The higher CRSS values in WSi{sub 2} are not only due to the intrinsic difference in the deformation behavior but also due to the existence of numerous grown-in stacking faults on (001).

  1. Tracking the activity-dependent diffusion of synaptic proteins using restricted photoconversion of Dendra2

    PubMed Central

    Cassé, Frédéric; Martin, Stéphane

    2015-01-01

    Spines are small protrusions on dendritic membranes receiving inputs from axonal termini. They consist in a head connected to the dendritic shaft by a narrow neck and contain multiple synaptic proteins that interact in a coordinated manner to allow for synaptic communication. This process involves many proteins that are moving in and out spines. However, comparing this synaptodendritic movement in basal and stimulated conditions is very challenging. Here we describe an elegant method to measure the activity-dependent diffusion of synaptic proteins using Dendra2 photoconversion. We provide a successful method to obtain Dendra2-photoconverted images and a step-by-step procedure to analyze the data. This live-imaging approach may also apply to investigate the diffusion of proteins across other subcellular compartments or organelles including but not restricted to, nucleus, nucleolus, ER, or vesicular structures. Once the imaging system is set up, data can be acquired in 1–30 min and analyzed in approximately 1–4 h. PMID:26441538

  2. Release activity-dependent control of vesicle endocytosis by the synaptic adhesion molecule N-cadherin.

    PubMed

    van Stegen, Bernd; Dagar, Sushma; Gottmann, Kurt

    2017-01-20

    At synapses in the mammalian brain, continuous information transfer requires the long-term maintenance of homeostatic coupling between exo- and endocytosis of synaptic vesicles. Because classical endocytosis is orders of magnitude slower than the millisecond-range exocytosis of vesicles, high frequency vesicle fusion could potentially compromise structural stability of synapses. However, the molecular mechanisms mediating the tight coupling of exo- and endocytosis are largely unknown. Here, we investigated the role of the transsynaptic adhesion molecules N-cadherin and Neuroligin1 in regulating vesicle exo- and endocytosis by using activity-induced FM4-64 staining and by using synaptophysin-pHluorin fluorescence imaging. The synaptic adhesion molecules N-cadherin and Neuroligin1 had distinct impacts on exo- and endocytosis at mature cortical synapses. Expression of Neuroligin1 enhanced vesicle release in a N-cadherin-dependent way. Most intriguingly, expression of N-cadherin enhanced both vesicle exo- and endocytosis. Further detailed analysis of N-cadherin knockout neurons revealed that the boosting of endocytosis by N-cadherin was largely dependent on preceding high levels of vesicle release activity. In summary, regulation of vesicle endocytosis was mediated at the molecular level by N-cadherin in a release activity-dependent manner. Because of its endocytosis enhancing function, N-cadherin might play an important role in the coupling of vesicle exo- and endocytosis.

  3. Release activity-dependent control of vesicle endocytosis by the synaptic adhesion molecule N-cadherin

    PubMed Central

    van Stegen, Bernd; Dagar, Sushma; Gottmann, Kurt

    2017-01-01

    At synapses in the mammalian brain, continuous information transfer requires the long-term maintenance of homeostatic coupling between exo- and endocytosis of synaptic vesicles. Because classical endocytosis is orders of magnitude slower than the millisecond-range exocytosis of vesicles, high frequency vesicle fusion could potentially compromise structural stability of synapses. However, the molecular mechanisms mediating the tight coupling of exo- and endocytosis are largely unknown. Here, we investigated the role of the transsynaptic adhesion molecules N-cadherin and Neuroligin1 in regulating vesicle exo- and endocytosis by using activity-induced FM4–64 staining and by using synaptophysin-pHluorin fluorescence imaging. The synaptic adhesion molecules N-cadherin and Neuroligin1 had distinct impacts on exo- and endocytosis at mature cortical synapses. Expression of Neuroligin1 enhanced vesicle release in a N-cadherin-dependent way. Most intriguingly, expression of N-cadherin enhanced both vesicle exo- and endocytosis. Further detailed analysis of N-cadherin knockout neurons revealed that the boosting of endocytosis by N-cadherin was largely dependent on preceding high levels of vesicle release activity. In summary, regulation of vesicle endocytosis was mediated at the molecular level by N-cadherin in a release activity-dependent manner. Because of its endocytosis enhancing function, N-cadherin might play an important role in the coupling of vesicle exo- and endocytosis. PMID:28106089

  4. Tracking the activity-dependent diffusion of synaptic proteins using restricted photoconversion of Dendra2.

    PubMed

    Cassé, Frédéric; Martin, Stéphane

    2015-01-01

    Spines are small protrusions on dendritic membranes receiving inputs from axonal termini. They consist in a head connected to the dendritic shaft by a narrow neck and contain multiple synaptic proteins that interact in a coordinated manner to allow for synaptic communication. This process involves many proteins that are moving in and out spines. However, comparing this synaptodendritic movement in basal and stimulated conditions is very challenging. Here we describe an elegant method to measure the activity-dependent diffusion of synaptic proteins using Dendra2 photoconversion. We provide a successful method to obtain Dendra2-photoconverted images and a step-by-step procedure to analyze the data. This live-imaging approach may also apply to investigate the diffusion of proteins across other subcellular compartments or organelles including but not restricted to, nucleus, nucleolus, ER, or vesicular structures. Once the imaging system is set up, data can be acquired in 1-30 min and analyzed in approximately 1-4 h.

  5. Effect of heat treatment and plastic deformation on the structure and the mechanical properties of nitrogen-bearing 04N9Kh2A steel

    NASA Astrophysics Data System (ADS)

    Blinov, V. M.; Bannykh, O. A.; Lukin, E. I.; Kostina, M. V.; Blinov, E. V.

    2014-11-01

    The effect of the conditions of heat treatment and plastic deformation on the structure and the mechanical properties of low-carbon martensitic nickel steel (9 wt % Ni) with an overequilibrium nitrogen content is studied. The limiting strain to failure of 04N9Kh2A steel is found to be 40% at a rolling temperature of 20°C and 80% at a rolling temperature of 900°C. Significant strengthening of the steel (σ0.2 = 1089 MPa) is obtained after rolling at a reduction of 40% at 20°C. The start and final temperatures of the α → γ transformation on heating and those of the γ → α transformation on cooling are determined by dilatometry. The specific features of the formation of the steel structure have been revealed as functions of the annealing and tempering temperatures. Electron-microscopic studies show that, after quenching from 850°C and tempering at 600°C for 1 h, the structure contains packet martensite with thin interlayers of retained austenite between martensite crystals. The strength of the nitrogen-bearing 04N9Kh2A steel after quenching from 850 and 900°C, cooling in water, and subsequent tempering at 500°C for 1 h is significantly higher than that of carboncontaining 0H9 steel used in cryogenic engineering.

  6. Evolution of the Structural-Phase State of a Ti-Al- V-Mo Alloy During Severe Plastic Deformation and SubSequent Annealing

    NASA Astrophysics Data System (ADS)

    Grabovetskaya, G. P.; Ratochka, I. V.; Mishin, I. P.; Zabudchenko, O. V.; Lykova, O. N.

    2016-05-01

    The effect of the initial phase composition of a Ti-Al-V-Mo alloy (VT16 according to Russian classification) on the evolution of its structural-phase state during the formation of ultrafine-grained structure and subsequent annealing is investigated by methods of optical and transmission electron microscopy and x-ray diffraction analysis. The structure is produced by cyclic pressing with a change of the deformation axis in each cycle combined with a gradual decrease of the pressing temperature from 1073 to 723 K. As this takes place, α″ → α + β and β → α phase transitions are found to develop in the test alloy. The phase state of the ultrafinegrained material thus produced depends for the most part on its elemental composition and severe plastic deformation regime. Annealing below the recrystallization temperature is shown to give rise to a β→α phase transition and alloying element redistribution. The foregoing processes allow for retaining a high level of the strength properties of the alloy.

  7. In vivo BDNF modulation of adult functional and morphological synaptic plasticity at hippocampal mossy fibers.

    PubMed

    Gómez-Palacio-Schjetnan, Andrea; Escobar, Martha L

    2008-11-07

    Brain-derived neurotrophic factor (BDNF) has been proposed as a key regulator and mediator of long-term synaptic modifications related to learning and memory maintenance. Our previous studies show that application of high-frequency stimulation (HFS) sufficient to elicit LTP at the dentate gyrus (DG)-CA3 pathway produces mossy fiber structural modifications 7 days after tetanic stimulation. In the present study, we show that acute intrahippocampal microinfusion of BDNF induces a lasting potentiation of synaptic efficacy in the DG-CA3 projection of anesthetized adult rats. Furthermore, we show that BDNF functional modifications in synaptic efficacy are accompanied by a presynaptic structural long-lasting reorganization at the hippocampal mossy fiber pathway. These findings support the idea that BDNF plays an important role as synaptic messenger of activity-dependent synaptic plasticity in the adult mammalian brain, in vivo.

  8. Crack Detection in Fibre Reinforced Plastic Structures Using Embedded Fibre Bragg Grating Sensors: Theory, Model Development and Experimental Validation

    PubMed Central

    Pereira, G. F.; Mikkelsen, L. P.; McGugan, M.

    2015-01-01

    In a fibre-reinforced polymer (FRP) structure designed using the emerging damage tolerance and structural health monitoring philosophy, sensors and models that describe crack propagation will enable a structure to operate despite the presence of damage by fully exploiting the material’s mechanical properties. When applying this concept to different structures, sensor systems and damage types, a combination of damage mechanics, monitoring technology, and modelling is required. The primary objective of this article is to demonstrate such a combination. This article is divided in three main topics: the damage mechanism (delamination of FRP), the structural health monitoring technology (fibre Bragg gratings to detect delamination), and the finite element method model of the structure that incorporates these concepts into a final and integrated damage-monitoring concept. A novel method for assessing a crack growth/damage event in fibre-reinforced polymer or structural adhesive-bonded structures using embedded fibre Bragg grating (FBG) sensors is presented by combining conventional measured parameters, such as wavelength shift, with parameters associated with measurement errors, typically ignored by the end-user. Conjointly, a novel model for sensor output prediction (virtual sensor) was developed using this FBG sensor crack monitoring concept and implemented in a finite element method code. The monitoring method was demonstrated and validated using glass fibre double cantilever beam specimens instrumented with an array of FBG sensors embedded in the material and tested using an experimental fracture procedure. The digital image correlation technique was used to validate the model prediction by correlating the specific sensor response caused by the crack with the developed model. PMID:26513653

  9. Crack Detection in Fibre Reinforced Plastic Structures Using Embedded Fibre Bragg Grating Sensors: Theory, Model Development and Experimental Validation.

    PubMed

    Pereira, G F; Mikkelsen, L P; McGugan, M

    2015-01-01

    In a fibre-reinforced polymer (FRP) structure designed using the emerging damage tolerance and structural health monitoring philosophy, sensors and models that describe crack propagation will enable a structure to operate despite the presence of damage by fully exploiting the material's mechanical properties. When applying this concept to different structures, sensor systems and damage types, a combination of damage mechanics, monitoring technology, and modelling is required. The primary objective of this article is to demonstrate such a combination. This article is divided in three main topics: the damage mechanism (delamination of FRP), the structural health monitoring technology (fibre Bragg gratings to detect delamination), and the finite element method model of the structure that incorporates these concepts into a final and integrated damage-monitoring concept. A novel method for assessing a crack growth/damage event in fibre-reinforced polymer or structural adhesive-bonded structures using embedded fibre Bragg grating (FBG) sensors is presented by combining conventional measured parameters, such as wavelength shift, with parameters associated with measurement errors, typically ignored by the end-user. Conjointly, a novel model for sensor output prediction (virtual sensor) was developed using this FBG sensor crack monitoring concept and implemented in a finite element method code. The monitoring method was demonstrated and validated using glass fibre double cantilever beam specimens instrumented with an array of FBG sensors embedded in the material and tested using an experimental fracture procedure. The digital image correlation technique was used to validate the model prediction by correlating the specific sensor response caused by the crack with the developed model.

  10. Compensatory plasticity: time matters

    PubMed Central

    Lazzouni, Latifa; Lepore, Franco

    2014-01-01

    Plasticity in the human and animal brain is the rule, the base for development, and the way to deal effectively with the environment for making the most efficient use of all the senses. When the brain is deprived of one sensory modality, plasticity becomes compensatory: the exception that invalidates the general loss hypothesis giving the opportunity of effective change. Sensory deprivation comes with massive alterations in brain structure and function, behavioral outcomes, and neural interactions. Blind individuals do as good as the sighted and even more, show superior abilities in auditory, tactile and olfactory processing. This behavioral enhancement is accompanied with changes in occipital cortex function, where visual areas at different levels become responsive to non-visual information. The intact senses are in general used more efficiently in the blind but are also used more exclusively. New findings are disentangling these two aspects of compensatory plasticity. What is due to visual deprivation and what is dependent on the extended use of spared modalities? The latter seems to contribute highly to compensatory changes in the congenitally blind. Short-term deprivation through the use of blindfolds shows that cortical excitability of the visual cortex is likely to show rapid modulatory changes after few minutes of light deprivation and therefore changes are possible in adulthood. However, reorganization remains more pronounced in the congenitally blind. Cortico-cortical pathways between visual areas and the areas of preserved sensory modalities are inhibited in the presence of vision, but are unmasked after loss of vision or blindfolding as a mechanism likely to drive cross-modal information to the deafferented visual cortex. The development of specialized higher order visual pathways independently from early sensory experience is likely to preserve their function and switch to the intact modalities. Plasticity in the blind is also accompanied with

  11. Castable plastic mold with electroplatable base

    DOEpatents

    Domeier, Linda A.; Morales, Alfredo M.; Gonzales, Marcela G.; Keifer, Patrick M.

    2004-01-20

    A sacrificial plastic mold having an electroplatable backing is provided as are methods of making such a mold via the infusion of a castable liquid formulation through a porous metal substrate (sheet, screen, mesh or foam) and into the features of a micro-scale master mold. Upon casting and demolding, the porous metal substrate is embedded within the cast formulation and projects a plastic structure with features determined by the mold tool. The plastic structure provides a sacrificial plastic mold mechanically bonded to the porous metal substrate, which provides a conducting support suitable for electroplating either contiguous or non-contiguous metal replicates. After electroplating and lapping, the sacrificial plastic can be dissolved, leaving the desired metal structure bonded to the porous metal substrate. Optionally, the electroplated structures may be debonded from the porous substrate by selective dissolution of the porous substrate or a coating thereon.

  12. Sacrificial Plastic Mold With Electroplatable Base

    DOEpatents

    Domeier, Linda A.; Hruby, Jill M.; Morales, Alfredo M.

    2005-08-16

    A sacrificial plastic mold having an electroplatable backing is provided. One embodiment consists of the infusion of a softened or molten thermoplastic through a porous metal substrate (sheet, screen, mesh or foam) and into the features of a micro-scale molding tool contacting the porous metal substrate. Upon demolding, the porous metal substrate will be embedded within the thermoplastic and will project a plastic structure with features determined by the mold tool. This plastic structure, in turn, provides a sacrificial plastic mold mechanically bonded to the porous metal substrate which provides a conducting support suitable for electroplating either contiguous or non-contiguous metal replicates. After electroplating and lapping, the sacrificial plastic can be dissolved to leave the desired metal structure bonded to the porous metal substrate. Optionally, the electroplated structures may be debonded from the porous substrate by selective dissolution of the porous substrate or a coating thereon.

  13. Sacrificial plastic mold with electroplatable base

    DOEpatents

    Domeier, Linda A.; Hruby, Jill M.; Morales, Alfredo M.

    2002-01-01

    A sacrificial plastic mold having an electroplatable backing is provided. One embodiment consists of the infusion of a softened or molten thermoplastic through a porous metal substrate (sheet, screen, mesh or foam) and into the features of a micro-scale molding tool contacting the porous metal substrate. Upon demolding, the porous metal substrate will be embedded within the thermoplastic and will project a plastic structure with features determined by the mold tool. This plastic structure, in turn, provides a sacrificial plastic mold mechanically bonded to the porous metal substrate which provides a conducting support suitable for electroplating either contiguous or non-contiguous metal replicates. After electroplating and lapping, the sacrificial plastic can be dissolved to leave the desired metal structure bonded to the porous metal substrate. Optionally, the electroplated structures may be debonded from the porous substrate by selective dissolution of the porous substrate or a coating thereon.

  14. Distinct roles for Cav2.1–2.3 in activity-dependent synaptic dynamics

    PubMed Central

    Ricoy, Ulises M.

    2014-01-01

    Synaptic transmission throughout most of the CNS is steeply dependent on presynaptic calcium influx through the voltage-gated calcium channels Cav2.1–Cav2.3. In addition to triggering exocytosis, this calcium influx also recruits short-term synaptic plasticity. During the complex patterns of presynaptic activity that occur in vivo, several forms of plasticity combine to generate a synaptic output that is dynamic, in which the size of a given excitatory postsynaptic potential (EPSP) in response to a given spike depends on the short-term history of presynaptic activity. It remains unclear whether the different Cav2 channels play distinct roles in defining these synaptic dynamics and, if so, under what conditions different Cav2 family members most effectively determine synaptic output. We examined these questions by measuring the effects of calcium channel-selective toxins on synaptic transmission at the Schaffer collateral synapse in hippocampal slices from adult mice in response to both low-frequency stimulation and complex stimulus trains derived from in vivo recordings. Blockade of Cav2.1 had a greater inhibitory effect on synaptic transmission during low-frequency components of the stimulus train than on synaptic transmission during high-frequency components of the train, indicating that Cav2.1 had a greater fractional contribution to synaptic transmission at low frequencies than at high frequencies. Relative to Cav2.1, Cav2.2 had a disproportionately reduced contribution to synaptic transmission at frequencies >20 Hz, while Cav2.3 had a disproportionately increased contribution to synaptic transmission at frequencies >1 Hz. These activity-dependent effects of different Cav2 family members shape the filtering characteristics of GABAB receptor-mediated presynaptic inhibition. Thus different Cav2 channels vary in their coupling to synaptic transmission over different frequency ranges, with consequences for the frequency tuning of both synaptic dynamics and

  15. a Study on the Structural Stress Analysis of Plastic Ankle Foot Orthosis (afo) Under Dorsiflexion and Plantarflextion Conditions

    NASA Astrophysics Data System (ADS)

    Lee, Young-Shin; Choi, Young-Jin; Kim, Hyun-Soo; Lee, Hyun-Seung; Cho, Kang-Hee

    The ankle foot orthosis (AFO) is used as the gait assistive tool for hemiplegic patients. The structural characteristics of the AFO are applied to the state of the patient. However, the prescription guide for hemiplegic patients is not well established. The purpose of this study is to develop design guide to find out the structural characteristics of polypropylene of AFO used for hemiplegics. In this study, the rigidities of dorsiflexion and plantarflexion of the AFO with varied types of ankle widths are investigated and performed by using FEM code.

  16. DISLOCATIONS AND PLASTIC BEHAVIOR OF IRON SINGLE CRYSTALS

    DTIC Science & Technology

    IRON , CRYSTAL STRUCTURE , CRYSTALLIZATION, DEFORMATION, ELASTIC PROPERTIES, GRAIN STRUCTURES(METALLURGY), GROWTH(PHYSIOLOGY), HEAT TREATMENT, METALLURGY, MICROSTRUCTURE, PLASTIC PROPERTIES, SPECTROGRAPHY.

  17. Providing plastic zone extrusion

    DOEpatents

    Manchiraju, Venkata Kiran; Feng, Zhili; David, Stan A.; Yu, Zhenzhen

    2017-04-11

    Plastic zone extrusion may be provided. First, a compressor may generate frictional heat in stock to place the stock in a plastic zone of the stock. Then, a conveyer may receive the stock in its plastic zone from the compressor and transport the stock in its plastic zone from the compressor. Next, a die may receive the stock in its plastic zone from the conveyer and extrude the stock to form a wire.

  18. Effect of plastic deformation on the electrophysical properties and structure of YBa2Cu3O y ceramics subjected to low-temperature treatment

    NASA Astrophysics Data System (ADS)

    Bobylev, I. B.; Zyuzeva, N. A.; Degtyarev, M. V.; Pilyugin, V. P.

    2015-12-01

    The electrophysical properties and structure of HTSC YBa2Cu3O y compound (123) subjected to plastic deformation by shear under a pressure of 1.7 GPa have been studied. After deformation, the electrophysical properties of samples prepared using the traditional ceramic technology were found to deteriorate. Subsequent annealing at 930°C cannot restore the critical current density ( j c) in low magnetic fields to initial magnitudes; however, in magnetic fields of more than 0.1 T, the j c magnitude increases compared to that for the starting state. The deformation of 123 ceramics treated at 200°C in a humid atmosphere that has undergone phase transformation into the 124 tetragonal phase allows its structure and electrophysical properties to be restored. In this case, the reverse transformation of phase 124 into 123, which is accompanied by the recrystallization of the material, takes place. The combination of low-temperature treatment and high shearing deformation leads to the appearance of texture and an increase of j c, in particular in high magnetic fields.

  19. Streptozotocin diabetic mice display depressive-like behavior and alterations in the structure, neurotransmission and plasticity of medial prefrontal cortex interneurons.

    PubMed

    Castillo-Gómez, Esther; Coviello, Simona; Perez-Rando, Marta; Curto, Yasmina; Carceller, Héctor; Salvador, Alicia; Nacher, Juan

    2015-07-01

    Diabetes mellitus patients are at increased risk of developing depression, although the neurobiological bases of this comorbidity are not yet fully understood. These patients show CNS alterations, similar to those found in major depression, including changes in the structure and neurotransmission of excitatory neurons. However, although depressive patients and animal models also display alterations in inhibitory networks, little is known about the effects of diabetes on interneurons. Our main objective was to study the impact of diabetes on interneurons of the medial prefrontal cortex (mPFC), one of the regions most affected by major depression. For this purpose we have induced diabetes with high-dose streptozotozin in transgenic mice displaying fluorescent interneurons. These animals showed a depressive-like behavior (increased immobility time in tail suspension test) in parallel with reductions in interneuronal dendritic arborization and in the expression of GAD67, the enzyme that synthetizes the inhibitory neurotransmitter GABA. However, the levels of PSA-NCAM, a plasticity-related molecule exclusively expressed by interneurons in the mPFC, were unaltered in the different regions and layers of this cortical area. Interestingly, diabetic mice also showed increased levels of synaptophysin, a synaptic vesicle protein. These results indicate that the structure and neurotransmission of interneurons is altered in the mPFC of diabetic mice and suggest that these changes may play a key role in the depressive symptoms associated to diabetes.

  20. The effects of gestational stress and SSRI antidepressant treatment on structural plasticity in the postpartum brain - a translational model for postpartum depression

    PubMed Central

    Haim, Achikam; Albin-Brooks, Christopher; Sherer, Morgan; Mills, Emily; Leuner, Benedetta

    2015-01-01

    Postpartum depression (PPD) is a common complication following childbirth experienced by one in every five new mothers. Although the neural basis of PPD remains unknown previous research in rats has shown that gestational stress, a risk factor for PPD, induces depressive-like behavior during the postpartum period. Moreover, the effect of gestational stress on postpartum mood is accompanied by structural modifications within the nucleus accumbens (NAc) and the medial prefrontal cortex (mPFC) – limbic regions that have been linked to PPD. Mothers diagnosed with PPD are often prescribed selective serotonin reuptake inhibitor (SSRI) antidepressant medications and yet little is known about their effects in models of PPD. Thus, here we investigated whether postpartum administration of Citalopram, an SSRI commonly used to treat PPD, would ameliorate the behavioral and morphological consequences of gestational stress. In addition, we examined the effects of gestational stress and postpartum administration of Citalopram on structural plasticity within the basolateral amygdala (BLA) which together with the mPFC and NAc forms a circuit that is sensitive to stress and is involved in mood regulation. Our results show that postpartum rats treated with Citalopram do not exhibit gestational stress-induced depressive-like behavior in the forced swim test. In addition, Citalopram was effective in reversing gestational stress-induced structural alterations in the postpartum NAc shell and mPFC. We also found that gestational stress increased spine density within the postpartum BLA, an effect which was not reversed by Citalopram treatment. Overall, these data highlight the usefulness of gestational stress as a valid and informative translational model for PPD. Furthermore, they suggest that structural alterations in the mPFC-NAc pathway may underlie stress-induced depressive-like behavior during the postpartum period and provide much needed information on how SSRIs may act in the

  1. The effects of gestational stress and Selective Serotonin reuptake inhibitor antidepressant treatment on structural plasticity in the postpartum brain--A translational model for postpartum depression.

    PubMed

    Haim, Achikam; Albin-Brooks, Christopher; Sherer, Morgan; Mills, Emily; Leuner, Benedetta

    2016-01-01

    This article is part of a Special Issue "Parental Care". Postpartum depression (PPD) is a common complication following childbirth experienced by one in every five new mothers. Although the neural basis of PPD remains unknown, previous research in rats has shown that gestational stress, a risk factor for PPD, induces depressive-like behavior during the postpartum period. Moreover, the effect of gestational stress on postpartum mood is accompanied by structural modifications within the nucleus accumbens (NAc) and the medial prefrontal cortex (mPFC)-limbic regions that have been linked to PPD. Mothers diagnosed with PPD are often prescribed selective serotonin reuptake inhibitor (SSRI) antidepressant medications and yet little is known about their effects in models of PPD. Thus, here we investigated whether postpartum administration of Citalopram, an SSRI commonly used to treat PPD, would ameliorate the behavioral and morphological consequences of gestational stress. In addition, we examined the effects of gestational stress and postpartum administration of Citalopram on structural plasticity within the basolateral amygdala (BLA) which together with the mPFC and NAc forms a circuit that is sensitive to stress and is involved in mood regulation. Our results show that postpartum rats treated with Citalopram do not exhibit gestational stress-induced depressive-like behavior in the forced swim test. In addition, Citalopram was effective in reversing gestational stress-induced structural alterations in the postpartum NAc shell and mPFC. We also found that gestational stress increased spine density within the postpartum BLA, an effect which was not reversed by Citalopram treatment. Overall, these data highlight the usefulness of gestational stress as a valid and informative translational model for PPD. Furthermore, they suggest that structural alterations in the mPFC-NAc pathway may underlie stress-induced depressive-like behavior during the postpartum period and provide

  2. Effect of rolling-assisted deformation on the formation of an ultrafine-grained structure in a two-phase titanium alloy subjected to severe plastic deformation

    NASA Astrophysics Data System (ADS)

    Demakov, S. L.; Elkina, O. A.; Illarionov, A. G.; Karabanalov, M. S.; Popov, A. A.; Semenova, I. P.; Saitova, L. R.; Shchetnikov, N. V.

    2008-06-01

    The effect of rolling in the temperature range 450 650°C on the fragmentation of the primary phase in a hot-rolled VT6 alloy rod preliminarily subjected to severe plastic deformation by equal-channel angular pressing at 700°C (scheme B c, the angle between the channels is 135°, 12 passes) is studied. Rolling at 450°C without preliminary ECAP is shown not to cause α-phase fragmentation and to favor intense cold working of the alloy due to multiple slip. ECAP provides partial fragmentation of the initial structure of the α phase and changes the morphology of the retained β phase: it transforms from a continuous matrix phase into separated precipitates located between α particles. This transformation activates the fragmentation of the α phase during rolling at 550°C owing to the development of twinning and polygonization processes apart from multiple slip. Both a decrease (to 450°C) and an increase (to 625 650°C) in the rolling temperature as compared to 550°C lead to the formation of a less homogeneous and fragmented structure because of weakly developed recovery and intense cold working in the former case and because of the beginning of recrystallization and the suppression of twinning in the latter case. A relation between the structure that forms upon SPD followed by rolling and the set of its properties is found. A general scheme is proposed for the structural transformations that occur during ECAP followed by rolling at various temperatures.

  3. Activity-dependent regulation of release probability at excitatory hippocampal synapses: a crucial role of FMRP in neurotransmission

    PubMed Central

    Wang, Xiao-Sheng; Peng, Chun-Zi; Cai, Wei-Jun; Xia, Jian; Jin, Daozhong; Dai, Yuqiao; Luo, Xue-Gang; Klyachko, Vitaly A.; Deng, Pan-Yue

    2014-01-01

    Transcriptional silencing of the Fmr1 gene encoding fragile X mental retardation protein (FMRP) causes Fragile X Syndrome (FXS), the most common form of inherited intellectual disability and the leading genetic cause of autism. FMRP has been suggested to play important roles in regulating neurotransmission and short-term synaptic plasticity at excitatory hippocampal and cortical synapses. However, the origins and the mechanisms of these FMRP actions remain incompletely understood, and the role of FMRP in regulating synaptic release probability and presynaptic function remains debated. Here we used variance-mean analysis and peak scaled nonstationary variance analysis to examine changes in both pre- and postsynaptic parameters during repetitive activity at excitatory CA3-CA1 hippocampal synapses in a mouse model of FXS. Our analyses revealed that loss of FMRP did not affect the basal release probability or basal synaptic transmission, but caused an abnormally elevated release probability specifically during repetitive activity. These abnormalities were not accompanied by changes in EPSC kinetics, quantal size or postsynaptic AMPA receptor conductance. Our results thus indicate that FMRP regulates neurotransmission at excitatory hippocampal synapses specifically during repetitive activity via modulation of release probability in a presynaptic manner. Our study suggests that FMRP function in regulating neurotransmitter release is an activity-dependent phenomenon that may contribute to the pathophysiology of FXS. PMID:24646437

  4. Activity-dependent synaptic GRIP1 accumulation drives synaptic scaling up in response to action potential blockade.

    PubMed

    Gainey, Melanie A; Tatavarty, Vedakumar; Nahmani, Marc; Lin, Heather; Turrigiano, Gina G

    2015-07-07

    Synaptic scaling is a form of homeostatic plasticity that stabilizes neuronal firing in response to changes in synapse number and strength. Scaling up in response to action-potential blockade is accomplished through increased synaptic accumulation of GluA2-containing AMPA receptors (AMPAR), but the receptor trafficking steps that drive this process remain largely obscure. Here, we show that the AMPAR-binding protein glutamate receptor-interacting protein-1 (GRIP1) is essential for regulated synaptic AMPAR accumulation during scaling up. Synaptic abundance of GRIP1 was enhanced by activity deprivation, directly increasing synaptic GRIP1 abundance through overexpression increased the amplitude of AMPA miniature excitatory postsynaptic currents (mEPSCs), and shRNA-mediated GRIP1 knockdown prevented scaling up of AMPA mEPSCs. Furthermore, knockdown and replace experiments targeting either GRIP1 or GluA2 revealed that scaling up requires the interaction between GRIP1 and GluA2. Finally, GRIP1 synaptic accumulation during scaling up did not require GluA2 binding. Taken together, our data support a model in which activity-dependent trafficking of GRIP1 to synaptic sites drives the forward trafficking and enhanced synaptic accumulation of GluA2-containing AMPAR during synaptic scaling up.

  5. Anion exchange resins: Structure, formulation, and applications. (Latest citations from the Rubber and Plastics Research Association database). Published Search

    SciTech Connect

    Not Available

    1994-07-01

    The bibliography contains citations concerning the formulation and synthesis of anion exchange resins based on such resins as amides, polyethylenes, and styrenes. Osmotic, sorption, and electrical properties; exchange kinetics behavior; structure studies; and temperature related performance effects on anion exchange resins are considered. Anion exchange chromatography of liquids, and applications in water purification, pollution control, and protein and metallic ion separation are included. (Contains a minimum of 222 citations and includes a subject term index and title list.)

  6. Babesia divergens and Neospora caninum apical membrane antigen 1 structures reveal selectivity and plasticity in apicomplexan parasite host cell invasion

    PubMed Central

    Tonkin, Michelle L; Crawford, Joanna; Lebrun, Maryse L; Boulanger, Martin J

    2013-01-01

    Host cell invasion by the obligate intracellular apicomplexan parasites, including Plasmodium (malaria) and Toxoplasma (toxoplasmosis), requires a step-wise mechanism unique among known host–pathogen interactions. A key step is the formation of the moving junction (MJ) complex, a circumferential constriction between the apical tip of the parasite and the host cell membrane that traverses in a posterior direction to enclose the parasite in a protective vacuole essential for intracellular survival. The leading model of MJ assembly proposes that Rhoptry Neck Protein 2 (RON2) is secreted into the host cell and integrated into the membrane where it serves as the receptor for apical membrane antigen 1 (AMA1) on the parasite surface. We have previously demonstrated that the AMA1-RON2 interaction is an effective target for inhibiting apicomplexan invasion. To better understand the AMA1-dependant molecular recognition events that promote invasion, including the significant AMA1-RON2 interaction, we present the structural characterization of AMA1 from the apicomplexan parasites Babesia divergens (BdAMA1) and Neospora caninum (NcAMA1) by X-ray crystallography. These studies offer intriguing structural insight into the RON2-binding surface groove in the AMA1 apical domain, which shows clear evidence for receptor–ligand co-evolution, and the hyper variability of the membrane proximal domain, which in Plasmodium is responsible for direct binding to erythrocytes. By incorporating the structural analysis of BdAMA1 and NcAMA1 with existing AMA1 structures and complexes we were able to define conserved pockets in the AMA1 apical groove that could be targeted for the design of broadly reactive therapeutics. PMID:23169033

  7. Structural plasticity within highly specific neuronal populations identifies a unique parcellation of motor learning in the adult brain

    PubMed Central

    Wang, Ling; Conner, James M.; Rickert, Jessica; Tuszynski, Mark H.

    2011-01-01

    Cortical networks undergo adaptations during learning, including increases in dendritic complexity and spines. We hypothesized that structural elaborations during learning are restricted to discrete subsets of cells preferentially activated by, and relevant to, novel experience. Accordingly, we examined corticospinal motor neurons segregated on the basis of their distinct descending projection patterns, and their contribution to specific aspects of motor control during a forelimb skilled grasping task in adult rats. Learning-mediated structural adaptations, including extensive expansions of spine density and dendritic complexity, were restricted solely to neurons associated with control of distal forelimb musculature required for skilled grasping; neurons associated with control of proximal musculature were unchanged by the experience. We further found that distal forelimb-projecting and proximal forelimb-projecting neurons are intermingled within motor cortex, and that this distribution does not change as a function of skill acquisition. These findings indicate that representations of novel experience in the adult motor cortex are associated with selective structural expansion in networks of functionally related, active neurons that are distributed across a single cortical domain. These results identify a distinct parcellation of cortical resources in support of learning. PMID:21257908

  8. A review of plastic waste biodegradation.

    PubMed

    Zheng, Ying; Yanful, Ernest K; Bassi, Amarjeet S

    2005-01-01

    With more and more plastics being employed in human lives and increasing pressure being placed on capacities available for plastic waste disposal, the need for biodegradable plastics and biodegradation of plastic wastes has assumed increasing importance in the last few years. This review looks at the technological advancement made in the development of more easily biodegradable plastics and the biodegradation of conventional plastics by microorganisms. Additives, such as pro-oxidants and starch, are applied in synthetic materials to modify and make plastics biodegradable. Recent research has shown that thermoplastics derived from polyolefins, traditionally considered resistant to biodegradation in ambient environment, are biodegraded following photo-degradation and chemical degradation. Thermoset plastics, such as aliphatic polyester and polyester polyurethane, are easily attacked by microorganisms directly because of the potential hydrolytic cleavage of ester or urethane bonds in their structures. Some microorganisms have been isolated to utilize polyurethane as a sole source of carbon and nitrogen source. Aliphatic-aromatic copolyesters have active commercial applications because of their good mechanical properties and biodegradability. Reviewing published and ongoing studies on plastic biodegradation, this paper attempts to make conclusions on potentially viable methods to reduce impacts of plastic waste on the environment.

  9. Effects of organic selenium on lead-induced impairments of spatial learning and memory as well as synaptic structural plasticity in rats.

    PubMed

    Han, Xiao-jie; Xiao, Yong-mei; Ai, Bao-min; Hu, Xiao-xia; Wei, Qing; Hu, Qian-sheng

    2014-01-01

    To study the effect of organic Se on spatial learning and memory deficits induced by Pb exposure at different developmental stages, and its relationship with alterations of synaptic structural plasticity, postnatal rat pups were randomly divided into five groups: Control; Pb (Weaned pups were exposed to Pb at postnatal day (PND) 21-42); Pb-Se (Weaned pups were exposed to Se at PND 43-63 after Pb exposure); maternal Pb (mPb) (Parents were exposed to Pb from 3 weeks before mating to the weaning of pups); mPb-Se (Parents were exposed to Pb and weaned pups were exposed to Se at PND 43-63). The spatial learning and memory of rat pups was measured by Morris water maze (MWM) on PND 63. We found that rat pups in Pb-Se group performed significantly better than those in Pb group (p<0.05). However, there was no significant difference in the ability of spatial learning and memory between the groups of mPb and mPb-Se (p>0.05). We also found that, before MWM, the numbers of neurons and synapses significantly decreased in mPb group, but not in Pb group. After MWM, the number of synapses, the thickness of postsynaptic density (PSD), the length of synaptic active zone and the synaptic curvature increased significantly in Pb-Se and mPb-Se group; while the width of synaptic cleft decreased significantly (p<0.05), compared to Pb group and mPb group, respectively. However, the number of synapses in mPb-Se group was still significantly lower than that in the control group (p<0.05). Our data demonstrated that organic Se had protective effects on the impairments of spatial learning and memory as well as synaptic structural plasticity induced by Pb exposure in rats after weaning, but not by the maternal Pb exposure which reduced the numbers of neurons and synapses in the early neural development.

  10. Plastic and Failure Analysis of Composites

    NASA Technical Reports Server (NTRS)

    Bigelow, C. A.; Johnson, W. S.

    1985-01-01

    Three-dimensional finite-element computer program called PAFAC (Plastic and Failure Analysis of Composites) developed for elastic/plastic analysis of fiber-reinforced composite materials and structures. PAFAC written in FORTRAN IV for batch execution. Particularly suited for analyzing laminated metal-matrix composites.

  11. Tunable plasticity in amorphous silicon carbide films.

    PubMed

    Matsuda, Yusuke; Kim, Namjun; King, Sean W; Bielefeld, Jeff; Stebbins, Jonathan F; Dauskardt, Reinhold H

    2013-08-28

    Plasticity plays a crucial role in the mechanical behavior of engineering materials. For instance, energy dissipation during plastic deformation is vital to the sufficient fracture resistance of engineering materials. Thus, the lack of plasticity in brittle hybrid organic-inorganic glasses (hybrid glasses) often results in a low fracture resistance and has been a significant challenge for their integration and applications. Here, we demonstrate that hydrogenated amorphous silicon carbide films, a class of hybrid glasses, can exhibit a plasticity that is even tunable by controlling their molecular structure and thereby leads to an increased and adjustable fracture resistance in the films. We decouple the plasticity contribution from the fracture resistance of the films by estimating the "work-of-fracture" using a mean-field approach, which provides some insight into a potential connection between the onset of plasticity in the films and the well-known rigidity percolation threshold.

  12. Activity-Dependent Palmitoylation Controls SynDIG1 Stability, Localization, and Function

    PubMed Central

    Kaur, Inderpreet; Yarov-Yarovoy, Vladimir; Kirk, Lyndsey M.; Plambeck, Kristopher E.; Barragan, Eden V.; Ontiveros, Eric S.

    2016-01-01

    Synapses are specialized contacts between neurons. Synapse differentiation-induced gene I (SynDIG1) plays a critical role during synapse development to regulate AMPA receptor (AMPAR) and PSD-95 content at excitatory synapses. Palmitoylation regulates the localization and function of many synaptic proteins, including AMPARs and PSD-95. Here we show that SynDIG1 is palmitoylated, and investigate the effects of palmitoylation on SynDIG1 stability and localization. Structural modeling of SynDIG1 suggests that the membrane-associated region forms a three-helical bundle with two cysteine residues located at positions 191 and 192 in the juxta-transmembrane region exposed to the cytoplasm. Site-directed mutagenesis reveals that C191 and C192 are palmitoylated in heterologous cells and positively regulates dendritic targeting in neurons. Like PSD-95, activity blockade in a rat hippocampal slice culture increases SynDIG1 palmitoylation, which is consistent with our prior demonstration that SynDIG1 localization at synapses increases upon activity blockade. These data demonstrate that palmitoylation of SynDIG1 is regulated by neuronal activity, and plays a critical role in regulating its stability and subcellular localization, and thereby its function. SIGNIFICANCE STATEMENT Palmitoylation is a reversible post-translation modification that has recently been recognized as playing a critical role in the localization and function of many synaptic proteins. Here we show that activity-dependent palmitoylation of the atypical AMPA receptor auxiliary transmembrane protein SynDIG1 regulates its stability and localization at synapses to regulate function and synaptic strength. PMID:27445135

  13. Modular community structure suggests metabolic plasticity during the transition to polar night in ice-covered Antarctic lakes.

    PubMed

    Vick-Majors, Trista J; Priscu, John C; Amaral-Zettler, Linda A

    2014-04-01

    High-latitude environments, such as the Antarctic McMurdo Dry Valley lakes, are subject to seasonally segregated light-dark cycles, which have important consequences for microbial diversity and function on an annual basis. Owing largely to the logistical difficulties of sampling polar environments during the darkness of winter, little is known about planktonic microbial community responses to the cessation of photosynthetic primary production during the austral sunset, which lingers from approximately February to April. Here, we hypothesized that changes in bacterial, archaeal and eukaryotic community structure, particularly shifts in favor of chemolithotrophs and mixotrophs, would manifest during the transition to polar night. Our work represents the first concurrent molecular characterization, using 454 pyrosequencing of hypervariable regions of the small-subunit ribosomal RNA gene, of bacterial, archaeal and eukaryotic communities in permanently ice-covered lakes Fryxell and Bonney, before and during the polar night transition. We found vertically stratified populations that varied at the community and/or operational taxonomic unit-level between lakes and seasons. Network analysis based on operational taxonomic unit level interactions revealed nonrandomly structured microbial communities organized into modules (groups of taxa) containing key metabolic potential capacities, including photoheterotrophy, mixotrophy and chemolithotrophy, which are likely to be differentially favored during the transition to polar night.

  14. Crystal structure and MD simulation of mouse EndoV reveal wedge motif plasticity in this inosine-specific endonuclease

    NASA Astrophysics Data System (ADS)

    Nawaz, Meh Sameen; Vik, Erik Sebastian; Ronander, Mia Elise; Solvoll, Anne Marthe; Blicher, Pernille; Bjørås, Magnar; Alseth, Ingrun; Dalhus, Bjørn

    2016-04-01

    Endonuclease V (EndoV) is an enzyme with specificity for deaminated adenosine (inosine) in nucleic acids. EndoV from Escherichia coli (EcEndoV) acts both on inosines in DNA and RNA, whereas the human homolog cleaves only at inosines in RNA. Inosines in DNA are mutagenic and the role of EndoV in DNA repair is well established. In contrast, the biological function of EndoV in RNA processing is largely unexplored. Here we have characterized a second mammalian EndoV homolog, mouse EndoV (mEndoV), and show that mEndoV shares the same RNA selectivity as human EndoV (hEndoV). Mouse EndoV cleaves the same inosine-containing substrates as hEndoV, but with reduced efficiencies. The crystal structure of mEndoV reveals a conformation different from the hEndoV and prokaryotic EndoV structures, particularly for the conserved tyrosine in the wedge motif, suggesting that this strand separating element has some flexibility. Molecular dynamics simulations of mouse and human EndoV reveal alternative conformations for the invariant tyrosine. The configuration of the active site, on the other hand, is very similar between the prokaryotic and mammalian versions of EndoV.

  15. Ubiquitous transcription factors display structural plasticity and diverse functions: NusG proteins - Shifting shapes and paradigms.

    PubMed

    NandyMazumdar, Monali; Artsimovitch, Irina

    2015-03-01

    Numerous accessory factors modulate RNA polymerase response to regulatory signals and cellular cues and establish communications with co-transcriptional RNA processing. Transcription regulators are astonishingly diverse, with similar mechanisms arising via convergent evolution. NusG/Spt5 elongation factors comprise the only universally conserved and ancient family of regulators. They bind to the conserved clamp helices domain of RNA polymerase, which also interacts with non-homologous initiation factors in all domains of life, and reach across the DNA channel to form processivity clamps that enable uninterrupted RNA chain synthesis. In addition to this ubiquitous function, NusG homologs exert diverse, and sometimes opposite, effects on gene expression by competing with each other and other regulators for binding to the clamp helices and by recruiting auxiliary factors that facilitate termination, antitermination, splicing, translation, etc. This surprisingly diverse range of activities and the underlying unprecedented structural changes make studies of these "transformer" proteins both challenging and rewarding.

  16. Effect of ethylene carbonate as a plasticizer on CuI/PVA nanocomposite: Structure, optical and electrical properties

    PubMed Central

    Mohamed, Shaimaa A.; Al-Ghamdi, A.A.; Sharma, G.D.; El Mansy, M.K.

    2013-01-01

    Layers of ethylene carbonate (EC) modified CuI/PVA polymer composites were prepared by growth of CuI nano-particles in an aqueous solution of PVA followed by casting at room temperature. The structural, thermal, optical, electrical and di-electrical characterization of polymer composites was investigated using different techniques. These investigations confirm the growth of CuI nano-particles and reduction of PVA crystallinity by increasing ethylene carbonate concentration. These results show that energy band gap and bulk conductivity increase while activation energy reduces with the increase of EC concentration in the composite. Moreover, the variation of the dielectric permittivity and dielectric loss with EC content are found to obey Debye dispersion relations. PMID:25685474

  17. Dolphin changes in whistle structure with watercraft activity depends on their behavioral state.

    PubMed

    May-Collado, Laura J; Quiñones-Lebrón, Shakira G

    2014-04-01

    Dolphins rely on whistles to identify each other and to receive and convey information about their environment. Although capable of adjusting these signals with changing environments, there is little information on how dolphins acoustically respond to different watercraft activities and if this response depends on dolphin behavioral state. Bottlenose dolphin whistles were recorded in the presence of research and dolphin-watching boats. Dolphins emitted lower frequency and longer whistles when interacting with dolphin-watching boats, particularly during foraging activities. This study suggests that dolphin-watching boat traffic significantly hinders dolphin communication during important behavioral states.

  18. Identifying Structure-Property Relationships Through DREAM.3D Representative Volume Elements and DAMASK Crystal Plasticity Simulations: An Integrated Computational Materials Engineering Approach

    NASA Astrophysics Data System (ADS)

    Diehl, Martin; Groeber, Michael; Haase, Christian; Molodov, Dmitri A.; Roters, Franz; Raabe, Dierk

    2017-03-01

    Predicting, understanding, and controlling the mechanical behavior is the most important task when designing structural materials. Modern alloy systems—in which multiple deformation mechanisms, phases, and defects are introduced to overcome the inverse strength-ductility relationship—give raise to multiple possibilities for modifying the deformation behavior, rendering traditional, exclusively experimentally-based alloy development workflows inappropriate. For fast and efficient alloy design, it is therefore desirable to predict the mechanical performance of candidate alloys by simulation studies to replace time- and resource-consuming mechanical tests. Simulation tools suitable for this task need to correctly predict the mechanical behavior in dependence of alloy composition, microstructure, texture, phase fractions, and processing history. Here, an integrated computational materials engineering approach based on the open source software packages DREAM.3D and DAMASK (Düsseldorf Advanced Materials Simulation Kit) that enables such virtual material development is presented. More specific, our approach consists of the following three steps: (1) acquire statistical quantities that describe a microstructure, (2) build a representative volume element based on these quantities employing DREAM.3D, and (3) evaluate the representative volume using a predictive crystal plasticity material model provided by DAMASK. Exemplarily, these steps are here conducted for a high-manganese steel.

  19. Effects of curcumin on chronic, unpredictable, mild, stress-induced depressive-like behaviour and structural plasticity in the lateral amygdala of rats.

    PubMed

    Zhang, Lin; Luo, Junxia; Zhang, Minghua; Yao, Wei; Ma, Xuelian; Yu, Shu Yan

    2014-05-01

    Depression is a neuropsychiatric disease associated with wide ranging disruptions in neuronal plasticity throughout the brain. Curcumin, a natural polyphenolic compound of curcuma loga, has been demonstrated to be effective in the treatment of depressive-like disorders. The present study aimed to investigate the mechanisms underlying the antidepressant-like effects of curcumin in a rat model of chronic, unpredictable, mild, stress (CUMS) -induced depression. The results showed that CUMS produced depressive-like behaviours in rats, which were associated with ultra-structural changes in neurons within the lateral amygdala (LA). In addition, the expression of synapse-associated proteins such as brain-derived neurotrophic factor (BDNF), PSD-95 and synaptophysin were significantly decreased in the LA of CUMS-treated rats. Chronic administration of curcumin (40 mg/kg, i.p. 6 wk) before stress exposure significantly prevented these neuronal and biochemical alterations induced by CUMS, and suppressed depressive-like behaviours, suggesting that this neuronal dysregulation may be related to the depressive-like behaviours caused by CUMS. Together with our previous results, the current findings demonstrate that curcumin exhibits neuroprotection and antidepressant-like effects in the CUMS-induced depression model. Furthermore, this antidepressant-like action of curcumin appears to be mediated by modulating synapse-associated proteins within the LA. These findings provide new insights into the underlying mechanisms leading to neural dysfunction in depression and reveal the therapeutic potential for curcumin use in clinical trials.

  20. Magic Angle Spinning NMR Reveals Sequence-Dependent Structural Plasticity, Dynamics, and the Spacer Peptide 1 Conformation in HIV-1 Capsid Protein Assemblies

    SciTech Connect

    Han, Yun; Hou, Guangjin; Suiter, Christopher L.; Ahn, Jinwoo; Byeon, In-Ja L.; Lipton, Andrew S.; Burton, Sarah D.; Hung, Ivan; Gorkov, Peter L.; Gan, Zhehong; Brey, William W.; Rice, David M.; Gronenborn, Angela M.; Polenova, Tatyana E.

    2013-11-27

    Maturation of HIV-1 virus into an infectious virion requires cleavage of the Gag polyprotein into its constituent domains and formation of a conical capsid core that encloses viral RNA and a small complement of proteins for replication. The final step of this process is the cleavage of the SP1 peptide from the CA-SP1 maturation intermediate, which triggers the condensation of the CA protein into a conical capsid. The mechanism of this step, including the conformation of the SP1 peptide in CA-SP1, is under intense debate. In this report, we examine the tubular assemblies of CA and the CA-SP1 maturation intermediate using Magic Angle Spinning NMR spectroscopy. At the magnetic fields of 19.9 T and above, tubular CA and CA-SP1 assemblies yield outstanding-quality 2D and 3D MAS NMR spectra, which are amenable to resonance assignments and detailed structural characterization. Dipolar- and scalar-based correlation experiments unequivocally indicate that SP1 peptide is in a random coil conformation and mobile in the assembled CA-SP1. Analysis of two sequence variants reveals that remarkably, the conformation of SP1 tail, of the functionally important CypA loop, and of the loop preceding helix 8 are sequence dependent and modulated by the residue variations at distal sites. These findings challenge the role of SP1 as a conformational switch in the maturation process and establish sequence-dependent conformational plasticity in CA.

  1. Plasticity, synaptic strength, and epilepsy: what can we learn from ultrastructural data?

    PubMed

    Leite, João Pereira; Neder, Luciano; Arisi, Gabriel Maisonnave; Carlotti, Carlos Gilberto; Assirati, João Alberto; Moreira, Jorge Eduardo

    2005-01-01

    Central nervous system synapses have an intrinsic plastic capacity to adapt to new conditions with rapid changes in their structure. Such activity-dependent refinement occurs during development and learning, and shares features with diseases such as epilepsy. Quantitative ultrastructural studies based on serial sectioning and reconstructions have shown various structural changes associated with synaptic strength involving both dendritic spines and postsynaptic densities (PSDs) during long-term potentiation (LTP). In this review, we focus on experimental studies that have analyzed at the ultrastructural level the consequences of LTP in rodents, and plastic changes in the hippocampus of experimental models of epilepsy and human tissue obtained during surgeries for intractable temporal lobe epilepsy (TLE). Modifications in spine morphology, increases in the proportion of synapses with perforated PSDs, and formation of multiple spine boutons arising from the same dendrite are the possible sequence of events that accompany hippocampal LTP. Structural remodeling of mossy fiber synapses and formation of aberrant synaptic contacts in the dentate gyrus are common features in experimental models of epilepsy and in human TLE. Combined electrophysiological and ultrastructural studies in kindled rats and chronic epileptic animals have indicated the occurrence of seizure- and neuron loss-induced changes in the hippocampal network. In these experiments, the synaptic contacts on granule cells are similar to those described for LTP. Such changes could be associated with enhancement of synaptic efficiency and may be important in epileptogenesis.

  2. Plastic encapsulated parts

    SciTech Connect

    Castillo, T.

    1994-10-01

    Plastic semiconductor packages were characterized as possible alternatives for canned devices, which are susceptible to internal shorts caused by conductive particles. Highly accelerated stress testing (HAST) as well as electrical and mechanical testing were conducted on plastic technology devices.

  3. Plastic casting resin poisoning

    MedlinePlus

    Epoxy poisoning; Resin poisoning ... Epoxy and resin can be poisonous if they are swallowed or their fumes are breathed in. ... Plastic casting resins are found in various plastic casting resin products.

  4. Activity-dependent fluorescent labeling of bacterial cells expressing the TOL pathway

    SciTech Connect

    William K. Keener; Mary E. Watwood

    2005-01-01

    3-Ethynylbenzoate functions as an activity-dependent, fluorogenic and chromogenic probe for Pseudomonas putida mt-2, which is known to degrade toluene via conversion to benzoate, followed by meta ring fission of the intermediate, catechol. This direct physiological analysis allows the fluorescent labeling of cells whose toluene-degrading enzymes have been induced by an aromatic substrate.

  5. Recovering automotive plastics

    SciTech Connect

    Not Available

    1993-10-01

    This article reports on the results of a study on increasing the recycling of plastics in automobiles. Plastics are being used in increasing amounts in vehicles and new methods of retrieving these plastics for recycling are needed to reduce the amount of automotive shredder residue that is currently being sent to residues. The study concentrated on increasing the ease of disassembly and contaminant removal.

  6. Plastics in Building.

    ERIC Educational Resources Information Center

    Skeist, Irving, Ed.

    The evaluation and use of plastics in the construction industry are explained. The contributors offer extensive, timely, and thoroughly researched data on the chemistry, properties, functions, engineering behavior, and specific applications of plastics to building requirements. The major subjects discussed in depth are--(1) the role of plastics in…

  7. Processing of plastics

    PubMed Central

    Spaak, Albert

    1975-01-01

    An overview is given of the processing of plastic materials from the handling of polymers in the pellet and powder form to manufacturing of a plastic fabricated product. Various types of equipment used and melt processing ranges of various polymer formulations to make the myriad of plastic products that are commercially available are discussed. PMID:1175556

  8. Tomorrow's Plastic World

    ERIC Educational Resources Information Center

    Macdonald, Averil

    2005-01-01

    Far from being just cheap packaging materials, plastics may be the materials of tomorrow. Plastic can conduct electricity, and this opens up a host of high-tech possibilities in the home and in energy generation. These possibilities are discussed here along with how plastic can be recycled and perhaps even grown.

  9. Structures of a pan-specific antagonist antibody complexed to different isoforms of TGFβ reveal structural plasticity of antibody-antigen interactions.

    PubMed

    Moulin, Aaron; Mathieu, Magali; Lawrence, Catherine; Bigelow, Russell; Levine, Mark; Hamel, Christine; Marquette, Jean-Piere; Le Parc, Josiane; Loux, Christophe; Ferrari, Paul; Capdevila, Cecile; Dumas, Jacques; Dumas, Bruno; Rak, Alexey; Bird, Julie; Qiu, Huawei; Pan, Clark Q; Edmunds, Tim; Wei, Ronnie R

    2014-12-01

    Various important biological pathways are modulated by TGFβ isoforms; as such they are potential targets for therapeutic intervention. Fresolimumab, also known as GC1008, is a pan-TGFβ neutralizing antibody that has been tested clinically for several indications including an ongoing trial for focal segmental glomerulosclerosis. The structure of the antigen-binding fragment of fresolimumab (GC1008 Fab) in complex with TGFβ3 has been reported previously, but the structural capacity of fresolimumab to accommodate tight interactions with TGFβ1 and TGFβ2 was insufficiently understood. We report the crystal structure of the single-chain variable fragment of fresolimumab (GC1008 scFv) in complex with target TGFβ1 to a resolution of 3.00 Å and the crystal structure of GC1008 Fab in complex with TGFβ2 to 2.83 Å. The structures provide further insight into the details of TGFβ recognition by fresolimumab, give a clear indication of the determinants of fresolimumab pan-specificity and provide potential starting points for the development of isoform-specific antibodies using a fresolimumab scaffold.

  10. Structures of a pan-specific antagonist antibody complexed to different isoforms of TGFβ reveal structural plasticity of antibody–antigen interactions

    PubMed Central

    Moulin, Aaron; Mathieu, Magali; Lawrence, Catherine; Bigelow, Russell; Levine, Mark; Hamel, Christine; Marquette, Jean-Piere; Le Parc, Josiane; Loux, Christophe; Ferrari, Paul; Capdevila, Cecile; Dumas, Jacques; Dumas, Bruno; Rak, Alexey; Bird, Julie; Qiu, Huawei; Pan, Clark Q; Edmunds, Tim; Wei, Ronnie R

    2014-01-01

    Various important biological pathways are modulated by TGFβ isoforms; as such they are potential targets for therapeutic intervention. Fresolimumab, also known as GC1008, is a pan-TGFβ neutralizing antibody that has been tested clinically for several indications including an ongoing trial for focal segmental glomerulosclerosis. The structure of the antigen-binding fragment of fresolimumab (GC1008 Fab) in complex with TGFβ3 has been reported previously, but the structural capacity of fresolimumab to accommodate tight interactions with TGFβ1 and TGFβ2 was insufficiently understood. We report the crystal structure of the single-chain variable fragment of fresolimumab (GC1008 scFv) in complex with target TGFβ1 to a resolution of 3.00 Å and the crystal structure of GC1008 Fab in complex with TGFβ2 to 2.83 Å. The structures provide further insight into the details of TGFβ recognition by fresolimumab, give a clear indication of the determinants of fresolimumab pan-specificity and provide potential starting points for the development of isoform-specific antibodies using a fresolimumab scaffold. 4KV5; 4KXZ PMID:25209176

  11. Plastic matrix composites with continuous fiber reinforcement

    SciTech Connect

    1991-09-19

    Most plastic resins are not suitable for structural applications. Although many resins are extremely tough, most lack strength, stiffness, and deform under load with time. By mixing strong, stiff, fibrous materials into the plastic matrix, a variety of structural composite materials can be formed. The properties of these composites can be tailored by fiber selection, orientation, and other factors to suit specific applications. The advantages and disadvantages of fiberglass, carbon-graphite, aramid (Kevlar 49), and boron fibers are summarized.

  12. Structural and Functional Plasticity within the Nucleus Accumbens and Prefrontal Cortex Associated with Time-Dependent Increases in Food Cue Seeking Behavior.

    PubMed

    Dingess, Paige M; Darling, Rebecca A; Derman, Rifka C; Wulff, Shaun S; Hunter, Melissa L; Ferrario, Carrie R; Brown, Travis E

    2017-03-15

    Urges to consume food can be driven by stimuli in the environment that are associated with previous food experience. Identifying adaptations within brain reward circuits that facilitate cue-induced food seeking is critical for understanding and preventing the overconsumption of food and subsequent weight gain. Utilizing electrophysiological, biochemical, and DiI labeling we examined functional and structural changes in the nucleus accumbens (NAc) and prefrontal cortex (PFC) associated with time-dependent increases in food craving ('incubation of craving'). Rats self-administered 60% high-fat or chow 45 mg pellets and were then tested for incubation of craving either 1 or 30 days after training (1d, 30d). High-fat was chosen for comparison to determine if palatability differentially affected incubation and/or plasticity. Rats showed robust incubation of craving for both food rewards, although responding for cues previously associated with high-fat was greater than chow at both 1d and 30d. In addition, previous experience with high-fat consumption reduced dendritic spine density in the PFC at both time points. In contrast, incubation was associated with an increase in NAc spine density and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR)-mediated transmission at 30d in both groups. Finally, incubation of craving for chow and high-fat was accompanied by an increase in calcium-permeable and calcium-impermeable AMPARs, respectively. Our results suggest that incubation of food craving alters brain reward circuitry and macronutrient composition specifically induces cortical changes in a way that may facilitate maladaptive food seeking behaviors.Neuropsychopharmacology accepted article preview online, 15 March 2017. doi:10.1038/npp.2017.57.

  13. A Neuronal Activity-Dependent Dual Function Chromatin-Modifying Complex Regulates Arc Expression1,2,3

    PubMed Central

    Oey, Nicodemus E.; Leung, How Wing; Ezhilarasan, Rajaram; Zhou, Lei; Beuerman, Roger W.; VanDongen, Hendrika M.A.

    2015-01-01

    Abstract Chromatin modification is an important epigenetic mechanism underlying neuroplasticity. Histone methylation and acetylation have both been shown to modulate gene expression, but the machinery responsible for mediating these changes in neurons has remained elusive. Here we identify a chromatin-modifying complex containing the histone demethylase PHF8 and the acetyltransferase TIP60 as a key regulator of the activity-induced expression of Arc, an important mediator of synaptic plasticity. Clinically, mutations in PHF8 cause X-linked mental retardation while TIP60 has been implicated in the pathogenesis of Alzheimer’s disease. Within minutes of increased synaptic activity, this dual function complex is rapidly recruited to the Arc promoter, where it specifically counteracts the transcriptionally repressive histone mark H3K9me2 to facilitate the formation of the transcriptionally permissive H3K9acS10P, thereby favoring transcriptional activation. Consequently, gain-of-function of the PHF8−TIP60 complex in primary rat hippocampal neurons has a positive effect on early activity-induced Arc gene expression, whereas interfering with the function of this complex abrogates it. A global proteomics screen revealed that the majority of common interactors of PHF8 and TIP60 were involved in mRNA processing, including PSF, an important molecule involved in neuronal gene regulation. Finally, we proceeded to show, using super-resolution microscopy, that PHF8 and TIP60 interact at the single molecule level with PSF, thereby situating this chromatin modifying complex at the crossroads of transcriptional activation. These findings point toward a mechanism by which an epigenetic pathway can regulate neuronal activity-dependent gene transcription, which has implications in the development of novel therapeutics for disorders of learning and memory. PMID:26464965

  14. Slow recovery from inactivation of Na+ channels underlies the activity-dependent attenuation of dendritic action potentials in hippocampal CA1 pyramidal neurons.

    PubMed

    Colbert, C M; Magee, J C; Hoffman, D A; Johnston, D

    1997-09-01

    Na+ action potentials propagate into the dendrites of pyramidal neurons driving an influx of Ca2+ that seems to be important for associative synaptic plasticity. During repetitive (10-50 Hz) firing, dendritic action potentials display a marked and prolonged voltage-dependent decrease in amplitude. Such a decrease is not apparent in somatic action potentials. We investigated the mechanisms of the different activity dependence of somatic and dendritic action potentials in CA1 pyramidal neurons of adult rats using whole-cell and cell-attached patch-clamp methods. There were three main findings. First, dendritic Na+ currents decreased in amplitude when repeatedly activated by brief (2 msec) depolarizations. Recovery was slow and voltage-dependent. Second, Na+ currents decreased much less in somatic than in dendritic patches. Third, although K+ currents remained constant during trains, K+ currents were necessary for dendritic action potential amplitude to decrease in whole-cell experiments. These results suggest that regional differences in Na+ and K+ channels determine the differences in the activity dependence of somatic and dendritic action potential amplitudes.

  15. Isolation of CA1 nuclear enriched fractions from hippocampal slices to study activity-dependent nuclear import of synapto-nuclear messenger proteins.

    PubMed

    Yuanxiang, Pingan; Bera, Sujoy; Karpova, Anna; Kreutz, Michael R; Mikhaylova, Marina

    2014-08-10

    Studying activity dependent protein expression, subcellular translocation, or phosphorylation is essential to understand the underlying cellular mechanisms of synaptic plasticity. Long-term potentiation (LTP) and long-term depression (LTD) induced in acute hippocampal slices are widely accepted as cellular models of learning and memory. There are numerous studies that use live cell imaging or immunohistochemistry approaches to visualize activity dependent protein dynamics. However these methods rely on the suitability of antibodies for immunocytochemistry or overexpression of fluorescence-tagged proteins in single neurons. Immunoblotting of proteins is an alternative method providing independent confirmation of the findings. The first limiting factor in preparation of subcellular fractions from individual tetanized hippocampal slices is the low amount of material. Second, the handling procedure is crucial because even very short and minor manipulations of living slices might induce activation of certain signaling cascades. Here we describe an optimized workflow in order to obtain sufficient quantity of nuclear enriched fraction of sufficient purity from the CA1 region of acute hippocampal slices from rat brain. As a representative example we show that the ERK1/2 phosphorylated form of the synapto-nuclear protein messenger Jacob actively translocates to the nucleus upon induction of LTP and can be detected in a nuclear enriched fraction from CA1 neurons.

  16. Modulation of BK channels contributes to activity-dependent increase of excitability through MTORC1 activity in CA1 pyramidal cells of mouse hippocampus

    PubMed Central

    Springer, Steven J.; Burkett, Brian J.; Schrader, Laura A.

    2015-01-01

    Memory acquisition and synaptic plasticity are accompanied by changes in the intrinsic excitability of CA1 pyramidal neurons. These activity-dependent changes in excitability are mediated by modulation of intrinsic currents which alters the responsiveness of the cell to synaptic inputs. The afterhyperpolarization (AHP), a major contributor to the regulation of neuronal excitability, is reduced in animals that have acquired several types of hippocampus-dependent memory tasks and also following synaptic potentiation by high frequency stimulation. BK channels underlie the fast AHP and contribute to spike repolarization, and this AHP is reduced in animals that successfully acquired trace-eyeblink conditioning. This suggests that BK channel function is activity-dependent, but the mechanisms are unknown. In this study, we found that blockade of BK channels with paxilline (10 μM) decreased IAHP amplitude and increased spike half-width and instantaneous frequency in response to a +100 pA depolarization. In addition, induction of long term potentiation (LTP) by theta burst stimulation (TBS) in CA1 pyramidal neurons reduced BK channel’s contribution to IAHP, spike repolarization, and instantaneous frequency. This result indicates that BK channel activity is decreased following synaptic potentiation. Interestingly, blockade of mammalian target of rapamycin (MTORC1) with rapamycin (400 nM) following synaptic potentiation restored BK channel function, suggesting a role for protein translation in signaling events which decreased postsynaptic BK channel activity following synaptic potentiation. PMID:25628536

  17. Brain-derived neurotrophic factor controls activity-dependent maturation of CA1 synapses by downregulating tonic activation of presynaptic kainate receptors.

    PubMed

    Sallert, Marko; Rantamäki, Tomi; Vesikansa, Aino; Anthoni, Heidi; Harju, Kirsi; Yli-Kauhaluoma, Jari; Taira, Tomi; Castren, Eero; Lauri, Sari E

    2009-09-09

    Immature hippocampal synapses express presynaptic kainate receptors (KARs), which tonically inhibit glutamate release. Presynaptic maturation involves activity-dependent downregulation of the tonic KAR activity and consequent increase in release probability; however, the molecular mechanisms underlying this developmental process are unknown. Here, we have investigated whether brain derived neurotrophic factor (BDNF), a secreted protein implicated in developmental plasticity in several areas of the brain, controls presynaptic maturation by regulating KARs. Application of BDNF in neonate hippocampal slices resulted in increase in synaptic transmission that fully occluded the immature-type KAR activity in area CA1. Conversely, genetic ablation of BDNF was associated with delayed synaptic maturation and persistent presynaptic KAR activity, suggesting a role for endogenous BDNF in the developmental regulation of KAR function. In addition, our data suggests a critical role for BDNF TrkB signaling in fast activity-dependent regulation of KARs. Selective acute inhibition of TrkB receptors using a chemical-genetic approach prevented rapid change in synapse dynamics and loss of tonic KAR activity that is typically seen in response to induction of LTP at immature synapses. Together, these data show that BDNF-TrkB-dependent maturation of glutamatergic synapses is tightly associated with a loss of endogenous KAR activity. The coordinated action of these two receptor mechanisms has immediate physiological relevance in controlling presynaptic efficacy and transmission dynamics at CA3-CA1 synapses at a stage of development when functional contact already exists but transmission is weak.

  18. Some reminiscences on studies of age-dependent and activity-dependent degeneration of sensory and motor endings in mammalian skeletal muscle

    PubMed Central

    Ribchester, Richard R

    2015-01-01

    I present here an overview of research on the biology of neuromuscular sensory and motor endings that was inspired and influenced partly by my educational experience in the Department of Zoology at the University of Durham, from 1971 to 1974. I allude briefly to neuromuscular synaptic structure and function in dystrophic mice, influences of activity on synapse elimination in development and regeneration, and activity-dependent protection and degeneration of neuromuscular junctions in WldS mice. PMID:26179026

  19. [Survey of plasticizers in polyvinyl chloride toys].

    PubMed

    Abe, Yutaka; Yamaguchi, Miku; Mutsuga, Motoh; Hirahara, Yoshichika; Kawamura, Yoko

    2012-01-01

    Plasticizers in 101 samples of polyvinyl chloride (PVC) toys on the Japanese market were surveyed. No phthalates were detected in designated toys, though bis(2-ethylhexyl)phthalate, diisononyl phthalate, diisobutyl phthalate, dibutyl phthalate, diisodecyl phthalate and benzyl butyl phthalate were detected in more than half of other toys. 2,2,4-Tributyl-1,3-pentanediol diisobutylate, o-acetyl tributyl citrate, adipates and diacetyl lauroyl glycerol, which are alternative plasticizers to phthalates, were detected. The results of structural analysis confirmed the presence of di(2-ethylhexyl)terephthalate, tributyl citrate, diisononyl 1,2-cyclohexanedicarboxylate and neopentyl glycol esters; these have not previonsly been reported in Japan. There appears to be a shift in plasticizers used for designated toys from phthalates to new plasticizers, and the number of different plasticizers is increasing.

  20. Activity-dependent signal changes in neurons by fiber-coupled microscopy

    NASA Astrophysics Data System (ADS)

    Sakurai, Takashi; Koida, Kowa

    2014-03-01

    To study neuronal functions in brain, we developed a higher resolution type fiber-coupled microscope (FCM), and measured the activity-dependent fluorescence intensity of the excitable cells over time. FCM was constructed by combining a fluorescence microscope with the high density type of fiber bundle, which consisted of 1.5 x 104 unit fiber in the assemble less than 0.5 mm tip. The spatial resolution was calculated to be 2.4 mm with the 5 mm focal depth. The activity-dependent Ca signals were detectable in each cell of either the pancreatic spheroids or the brain slices. The present FCM is very promising for detailed studies with the live imaging of signal molecules in the body at a single cell level.

  1. Evolutionary plasticity determination by orthologous groups distribution

    PubMed Central

    2011-01-01

    Background Genetic plasticity may be understood as the ability of a functional gene network to tolerate alterations in its components or structure. Usually, the studies involving gene modifications in the course of the evolution are concerned to nucleotide sequence alterations in closely related species. However, the analysis of large scale data about the distribution of gene families in non-exclusively closely related species can provide insights on how plastic or how conserved a given gene family is. Here, we analyze the abundance and diversity of all Eukaryotic Clusters of Orthologous Groups (KOG) present in STRING database, resulting in a total of 4,850 KOGs. This dataset comprises 481,421 proteins distributed among 55 eukaryotes. Results We propose an index to evaluate the evolutionary plasticity and conservation of an orthologous group based on its abundance and diversity across eukaryotes. To further KOG plasticity analysis, we estimate the evolutionary distance average among all proteins which take part in the same orthologous group. As a result, we found a strong correlation between the evolutionary distance average and the proposed evolutionary plasticity index. Additionally, we found low evolutionary plasticity in Saccharomyces cerevisiae genes associated with inviability and Mus musculus genes associated with early lethality. At last, we plot the evolutionary plasticity value in different gene networks from yeast and humans. As a result, it was possible to discriminate among higher and lower plastic areas of the gene networks analyzed. Conclusions The distribution of gene families brings valuable information on evolutionary plasticity which might be related with genetic plasticity. Accordingly, it is possible to discriminate among conserved and plastic orthologous groups by evaluating their abundance and diversity across eukaryotes. Reviewers This article was reviewed by Prof Manyuan Long, Hiroyuki Toh, and Sebastien Halary. PMID:21586164

  2. Modeling activity-dependent changes of axonal spike conduction in primary afferent C-nociceptors

    PubMed Central

    Tigerholm, Jenny; Petersson, Marcus E.; Obreja, Otilia; Lampert, Angelika; Carr, Richard; Schmelz, Martin

    2013-01-01

    Action potential initiation and conduction along peripheral axons is a dynamic process that displays pronounced activity dependence. In patients with neuropathic pain, differences in the modulation of axonal conduction velocity by activity suggest that this property may provide insight into some of the pathomechanisms. To date, direct recordings of axonal membrane potential have been hampered by the small diameter of the fibers. We have therefore adopted an alternative approach to examine the basis of activity-dependent changes in axonal conduction by constructing a comprehensive mathematical model of human cutaneous C-fibers. Our model reproduced axonal spike propagation at a velocity of 0.69 m/s commensurate with recordings from human C-nociceptors. Activity-dependent slowing (ADS) of axonal propagation velocity was adequately simulated by the model. Interestingly, the property most readily associated with ADS was an increase in the concentration of intra-axonal sodium. This affected the driving potential of sodium currents, thereby producing latency changes comparable to those observed for experimental ADS. The model also adequately reproduced post-action potential excitability changes (i.e., recovery cycles) observed in vivo. We performed a series of control experiments replicating blockade of particular ion channels as well as changing temperature and extracellular ion concentrations. In the absence of direct experimental approaches, the model allows specific hypotheses to be formulated regarding the mechanisms underlying activity-dependent changes in C-fiber conduction. Because ADS might functionally act as a negative feedback to limit trains of nociceptor activity, we envisage that identifying its mechanisms may also direct efforts aimed at alleviating neuronal hyperexcitability in pain patients. PMID:24371290

  3. Evidence for evolutionary divergence of activity-dependent gene expression in developing neurons

    PubMed Central

    Qiu, Jing; McQueen, Jamie; Bilican, Bilada; Dando, Owen; Magnani, Dario; Punovuori, Karolina; Selvaraj, Bhuvaneish T; Livesey, Matthew; Haghi, Ghazal; Heron, Samuel; Burr, Karen; Patani, Rickie; Rajan, Rinku; Sheppard, Olivia; Kind, Peter C; Simpson, T Ian; Tybulewicz, Victor LJ; Wyllie, David JA; Fisher, Elizabeth MC; Lowell, Sally; Chandran, Siddharthan; Hardingham, Giles E

    2016-01-01

    Evolutionary differences in gene regulation between humans and lower mammalian experimental systems are incompletely understood, a potential translational obstacle that is challenging to surmount in neurons, where primary tissue availability is poor. Rodent-based studies show that activity-dependent transcriptional programs mediate myriad functions in neuronal development, but the extent of their conservation in human neurons is unknown. We compared activity-dependent transcriptional responses in developing human stem cell-derived cortical neurons with those induced in developing primary- or stem cell-derived mouse cortical neurons. While activity-dependent gene-responsiveness showed little dependence on developmental stage or origin (primary tissue vs. stem cell), notable species-dependent differences were observed. Moreover, differential species-specific gene ortholog regulation was recapitulated in aneuploid mouse neurons carrying human chromosome-21, implicating promoter/enhancer sequence divergence as a factor, including human-specific activity-responsive AP-1 sites. These findings support the use of human neuronal systems for probing transcriptional responses to physiological stimuli or indeed pharmaceutical agents. DOI: http://dx.doi.org/10.7554/eLife.20337.001 PMID:27692071

  4. Activity-Dependent Callosal Axon Projections in Neonatal Mouse Cerebral Cortex

    PubMed Central

    Tagawa, Yoshiaki; Hirano, Tomoo

    2012-01-01

    Callosal axon projections are among the major long-range axonal projections in the mammalian brain. They are formed during the prenatal and early postnatal periods in the mouse, and their development relies on both activity-independent and -dependent mechanisms. In this paper, we review recent findings about the roles of neuronal activity in callosal axon projections. In addition to the well-documented role of sensory-driven neuronal activity, recent studies using in utero electroporation demonstrated an essential role of spontaneous neuronal activity generated in neonatal cortical circuits. Both presynaptic and postsynaptic neuronal activities are critically involved in the axon development. Studies have begun to reveal intracellular signaling pathway which works downstream of neuronal activity. We also review several distinct patterns of neuronal activity observed in the developing cerebral cortex, which might play roles in activity-dependent circuit construction. Such neuronal activity during the neonatal period can be disrupted by genetic factors, such as mutations in ion channels. It has been speculated that abnormal activity caused by such factors may affect activity-dependent circuit construction, leading to some developmental disorders. We discuss a possibility that genetic mutation in ion channels may impair callosal axon projections through an activity-dependent mechanism. PMID:23213574

  5. CYCLIC-LOADING TESTS OF TWO GLASSREINFORCED PLASTIC CYLINDERS,

    DTIC Science & Technology

    SUBMARINE HULLS, *LAMINATED PLASTICS , COMPOSITE MATERIALS, GLASS TEXTILES, PRESSURE VESSELS, HYDROSTATIC PRESSURE, FATIGUE(MECHANICS), MODEL TESTS, LOADS(FORCES), RINGS, TAPES, CREEP, SHELLS(STRUCTURAL FORMS).

  6. How Plastics Work

    NASA Astrophysics Data System (ADS)

    Bloomfield, Louis

    2013-03-01

    We encounter plastics every day, but despite their widespread use, amazing range of properties, and basic scientific underpinnings, most physicists--like most people--know relatively little about plastics. In contrast to hard crystalline and amorphous solids (e.g., metals, salts, ceramics, and glasses), we take plastics for granted, select them carelessly, and examine them more closely only on a need-to-know basis. By ignoring plastics until we need them, however, we risk not knowing what we don't know and using the wrong ones. To repurpose a familiar advertisement, ``there's a plastic for that.'' This talk will review some of the basic physics and science of plastics. It will examine the roles of temperature, order, intermolecular forces, entanglements, and linkages in plastics, and how those issues affect the properties of a given plastic. We'll stop along the way to recognize a few of the more familiar plastics, natural and synthetic, and explain some of their mechanical, chemical, and optical properties. The talk will conclude by explaining the remarkable properties of a plastic that has been largely misunderstood since its discovery 70 years ago: Silly Putty.

  7. Influence of the number of passes under equal-channel angular pressing on the elastic-plastic properties, durability, and defect structure of the Al + 0.2 wt % Sc alloy

    NASA Astrophysics Data System (ADS)

    Betekhtin, V. I.; Sklenicka, V.; Saxl, I.; Kardashev, B. K.; Kadomtsev, A. G.; Narykova, M. V.

    2010-08-01

    The regularities of the influence of the number of passes under equal-channel angular pressing on the mechanical properties and defect structure of an aluminum alloy have been elucidated. It has been established that the degradation of the mechanical properties (a decrease in the durability) is associated with the formation of nanoregions of an excess free volume in the course of severe plastic deformation under equalchannel angular pressing. A correlation between the nucleation of excess free volume regions and the formation of high-angle grain boundaries under equal-channel angular pressing has been revealed. The nature of the influence of severe plastic deformation on the elastic modulus, the vibration decrement, and the microplastic flow stress has been analyzed.

  8. Our plastic age.

    PubMed

    Thompson, Richard C; Swan, Shanna H; Moore, Charles J; vom Saal, Frederick S

    2009-07-27

    Within the last few decades, plastics have revolutionized our daily lives. Globally we use in excess of 260 million tonnes of plastic per annum, accounting for approximately 8 per cent of world oil production. In this Theme Issue of Philosophical Transactions of the Royal Society, we describe current and future trends in usage, together with the many benefits that plastics bring to society. At the same time, we examine the environmental consequences resulting from the accumulation of waste plastic, the effects of plastic debris on wildlife and concerns for human health that arise from the production, usage and disposal of plastics. Finally, we consider some possible solutions to these problems together with the research and policy priorities necessary for their implementation.

  9. Investigation of hippocampal synaptic transmission and plasticity in mice deficient in the actin-binding protein Drebrin

    PubMed Central

    Willmes, Claudia G.; Mack, Till G. A.; Ledderose, Julia; Schmitz, Dietmar; Wozny, Christian; Eickholt, Britta J.

    2017-01-01

    The dynamic regulation of the actin cytoskeleton plays a key role in controlling the structure and function of synapses. It is vital for activity-dependent modulation of synaptic transmission and long-term changes in synaptic morphology associated with memory consolidation. Several regulators of actin dynamics at the synapse have been identified, of which a salient one is the postsynaptic actin stabilising protein Drebrin (DBN). It has been suggested that DBN modulates neurotransmission and changes in dendritic spine morphology associated with synaptic plasticity. Given that a decrease in DBN levels is correlated with cognitive deficits associated with ageing and dementia, it was hypothesised that DBN protein abundance instructs the integrity and function of synapses. We created a novel DBN deficient mouse line. Analysis of gross brain and neuronal morphology revealed no phenotype in the absence of DBN. Electrophysiological recordings in acute hippocampal slices and primary hippocampal neuronal cultures showed that basal synaptic transmission, and both long-term and homeostatic synaptic plasticity were unchanged, suggesting that loss of DBN is not sufficient in inducing synapse dysfunction. We propose that the overall lack of changes in synaptic function and plasticity in DBN deficient mice may indicate robust compensatory mechanisms that safeguard cytoskeleton dynamics at the synapse. PMID:28198431

  10. Plastics and health risks.

    PubMed

    Halden, Rolf U

    2010-01-01

    By 2010, the worldwide annual production of plastics will surpass 300 million tons. Plastics are indispensable materials in modern society, and many products manufactured from plastics are a boon to public health (e.g., disposable syringes, intravenous bags). However, plastics also pose health risks. Of principal concern are endocrine-disrupting properties, as triggered for example by bisphenol A and di-(2-ethylhexyl) phthalate (DEHP). Opinions on the safety of plastics vary widely, and despite more than five decades of research, scientific consensus on product safety is still elusive. This literature review summarizes information from more than 120 peer-reviewed publications on health effects of plastics and plasticizers in lab animals and humans. It examines problematic exposures of susceptible populations and also briefly summarizes adverse environmental impacts from plastic pollution. Ongoing efforts to steer human society toward resource conservation and sustainable consumption are discussed, including the concept of the 5 Rs--i.e., reduce, reuse, recycle, rethink, restrain--for minimizing pre- and postnatal exposures to potentially harmful components of plastics.

  11. Additives in plastics.

    PubMed Central

    Deanin, R D

    1975-01-01

    The polymers used in plastics are generally harmless. However, they are rarely used in pure form. In almost all commercial plastics, they are "compounded" with monomeric ingredients to improve their processing and end-use performance. In order of total volume used, these monomeric additives may be classified as follows: reinforcing fibers, fillers, and coupling agents; plasticizers; colorants; stabilizers (halogen stabilizers, antioxidants, ultraviolet absorbers, and biological preservatives); processing aids (lubricants, others, and flow controls); flame retardants, peroxides; and antistats. Some information is already available, and much more is needed, on potential toxicity and safe handling of these additives during processing and manufacture of plastics products. PMID:1175566

  12. Additives in plastics.

    PubMed

    Deanin, R D

    1975-06-01

    The polymers used in plastics are generally harmless. However, they are rarely used in pure form. In almost all commercial plastics, they are "compounded" with monomeric ingredients to improve their processing and end-use performance. In order of total volume used, these monomeric additives may be classified as follows: reinforcing fibers, fillers, and coupling agents; plasticizers; colorants; stabilizers (halogen stabilizers, antioxidants, ultraviolet absorbers, and biological preservatives); processing aids (lubricants, others, and flow controls); flame retardants, peroxides; and antistats. Some information is already available, and much more is needed, on potential toxicity and safe handling of these additives during processing and manufacture of plastics products.

  13. Optical sensors based on plastic fibers.

    PubMed

    Bilro, Lúcia; Alberto, Nélia; Pinto, João L; Nogueira, Rogério

    2012-01-01

    The recent advances of polymer technology allowed the introduction of plastic optical fiber in sensor design. The advantages of optical metrology with plastic optical fiber have attracted the attention of the scientific community, as they allow the development of low-cost or cost competitive systems compared with conventional technologies. In this paper, the current state of the art of plastic optical fiber technology will be reviewed, namely its main characteristics and sensing advantages. Several measurement techniques will be described, with a strong focus on interrogation approaches based on intensity variation in transmission and reflection. The potential applications involving structural health monitoring, medicine, environment and the biological and chemical area are also presented.

  14. Neuronal Plasticity: Increasing the Gain in Pain

    NASA Astrophysics Data System (ADS)

    Woolf, Clifford J.; Salter, Michael W.

    2000-06-01

    We describe those sensations that are unpleasant, intense, or distressing as painful. Pain is not homogeneous, however, and comprises three categories: physiological, inflammatory, and neuropathic pain. Multiple mechanisms contribute, each of which is subject to or an expression of neural plasticity-the capacity of neurons to change their function, chemical profile, or structure. Here, we develop a conceptual framework for the contribution of plasticity in primary sensory and dorsal horn neurons to the pathogenesis of pain, identifying distinct forms of plasticity, which we term activation, modulation, and modification, that by increasing gain, elicit pain hypersensitivity.

  15. The synaptic plasticity and memory hypothesis: encoding, storage and persistence

    PubMed Central

    Takeuchi, Tomonori; Duszkiewicz, Adrian J.; Morris, Richard G. M.

    2014-01-01

    The synaptic plasticity and memory hypothesis asserts that activity-dependent synaptic plasticity is induced at appropriate synapses during memory formation and is both necessary and sufficient for the encoding and trace storage of the type of memory mediated by the brain area in which it is observed. Criteria for establishing the necessity and sufficiency of such plasticity in mediating trace storage have been identified and are here reviewed in relation to new work using some of the diverse techniques of contemporary neuroscience. Evidence derived using optical imaging, molecular-genetic and optogenetic techniques in conjunction with appropriate behavioural analyses continues to offer support for the idea that changing the strength of connections between neurons is one of the major mechanisms by which engrams are stored in the brain. PMID:24298167

  16. Activity Dependent Protein Degradation Is Critical for the Formation and Stability of Fear Memory in the Amygdala

    PubMed Central

    Jarome, Timothy J.; Helmstetter, Fred J.

    2011-01-01

    Protein degradation through the ubiquitin-proteasome system [UPS] plays a critical role in some forms of synaptic plasticity. However, its role in memory formation in the amygdala, a site critical for the formation of fear memories, currently remains unknown. Here we provide the first evidence that protein degradation through the UPS is critically engaged at amygdala synapses during memory formation and retrieval. Fear conditioning results in NMDA-dependent increases in degradation-specific polyubiquitination in the amygdala, targeting proteins involved in translational control and synaptic structure and blocking the degradation of these proteins significantly impairs long-term memory. Furthermore, retrieval of fear memory results in a second wave of NMDA-dependent polyubiquitination that targets proteins involved in translational silencing and synaptic structure and is critical for memory updating following recall. These results indicate that UPS-mediated protein degradation is a major regulator of synaptic plasticity necessary for the formation and stability of long-term memories at amygdala synapses. PMID:21961035

  17. Activity-dependent transmission and integration control the timescales of auditory processing at an inhibitory synapse.

    PubMed

    Ammer, Julian J; Siveke, Ida; Felmy, Felix

    2015-06-15

    To capture the context of sensory information, neural networks must process input signals across multiple timescales. In the auditory system, a prominent change in temporal processing takes place at an inhibitory GABAergic synapse in the dorsal nucleus of the lateral lemniscus (DNLL). At this synapse, inhibition outlasts the stimulus by tens of milliseconds, such that it suppresses responses to lagging sounds, and is therefore implicated in echo suppression. Here, we untangle the cellular basis of this inhibition. We demonstrate with in vivo whole-cell patch-clamp recordings in Mongolian gerbils that the duration of inhibition increases with sound intensity. Activity-dependent spillover and asynchronous release translate the high presynaptic firing rates found in vivo into a prolonged synaptic output in acute slice recordings. A key mechanism controlling the inhibitory time course is the passive integration of the hyperpolarizing inhibitory conductance. This prolongation depends on the synaptic conductance amplitude. Computational modeling shows that this prolongation is a general mechanism and relies on a non-linear effect caused by synaptic conductance saturation when approaching the GABA reversal potential. The resulting hyperpolarization generates an efficient activity-dependent suppression of action potentials without affecting the threshold or gain of the input-output function. Taken together, the GABAergic inhibition in the DNLL is adjusted to the physiologically relevant duration by passive integration of inhibition with activity-dependent synaptic kinetics. This change in processing timescale combined with the reciprocal connectivity between the DNLLs implements a mechanism to suppress the distracting localization cues of echoes and helps to localize the initial sound source reliably.

  18. Developmental experience-dependent plasticity in the first synapse of the Drosophila olfactory circuit.

    PubMed

    Golovin, Randall M; Broadie, Kendal

    2016-12-01

    Evidence accumulating over the past 15 years soundly refutes the dogma that the Drosophila nervous system is hardwired. The preponderance of studies reveals activity-dependent neural circuit refinement driving optimization of behavioral outputs. We describe developmental, sensory input-dependent plasticity in the brain olfactory antennal lobe, which we term long-term central adaption (LTCA). LTCA is evoked by prolonged exposure to an odorant during the first week of posteclosion life, resulting in a persistently decreased response to aversive odors and an enhanced response to attractive odors. This limited window of early-use, experience-dependent plasticity represents a critical period of olfactory circuit refinement tuned by initial sensory input. Consequent behavioral adaptations have been associated with changes in the output of olfactory projection neurons to higher brain centers. Recent studies have indicated a central role for local interneuron signaling in LTCA presentation. Genetic and molecular analyses have implicated the mRNA-binding fragile X mental retardation protein and ataxin-2 regulators, Notch trans-synaptic signaling, and cAMP signal transduction as core regulatory steps driving LTCA. In this article, we discuss the structural, functional, and behavioral changes associated with LTCA and review our current understanding of the molecular pathways underlying these developmental, experience-dependent changes in the olfactory circuitry.

  19. Synaptic plasticity and neuronal refractory time cause scaling behaviour of neuronal avalanches

    NASA Astrophysics Data System (ADS)

    Michiels van Kessenich, L.; de Arcangelis, L.; Herrmann, H. J.

    2016-08-01

    Neuronal avalanches measured in vitro and in vivo in different cortical networks consistently exhibit power law behaviour for the size and duration distributions with exponents typical for a mean field self-organized branching process. These exponents are also recovered in neuronal network simulations implementing various neuronal dynamics on different network topologies. They can therefore be considered a very robust feature of spontaneous neuronal activity. Interestingly, this scaling behaviour is also observed on regular lattices in finite dimensions, which raises the question about the origin of the mean field behavior observed experimentally. In this study we provide an answer to this open question by investigating the effect of activity dependent plasticity in combination with the neuronal refractory time in a neuronal network. Results show that the refractory time hinders backward avalanches forcing a directed propagation. Hebbian plastic adaptation plays the role of sculpting these directed avalanche patterns into the topology of the network slowly changing it into a branched structure where loops are marginal.

  20. Synaptic plasticity and neuronal refractory time cause scaling behaviour of neuronal avalanches.

    PubMed

    Michiels van Kessenich, L; de Arcangelis, L; Herrmann, H J

    2016-08-18

    Neuronal avalanches measured in vitro and in vivo in different cortical networks consistently exhibit power law behaviour for the size and duration distributions with exponents typical for a mean field self-organized branching process. These exponents are also recovered in neuronal network simulations implementing various neuronal dynamics on different network topologies. They can therefore be considered a very robust feature of spontaneous neuronal activity. Interestingly, this scaling behaviour is also observed on regular lattices in finite dimensions, which raises the question about the origin of the mean field behavior observed experimentally. In this study we provide an answer to this open question by investigating the effect of activity dependent plasticity in combination with the neuronal refractory time in a neuronal network. Results show that the refractory time hinders backward avalanches forcing a directed propagation. Hebbian plastic adaptation plays the role of sculpting these directed avalanche patterns into the topology of the network slowly changing it into a branched structure where loops are marginal.

  1. Synaptic plasticity and neuronal refractory time cause scaling behaviour of neuronal avalanches

    PubMed Central

    Michiels van Kessenich, L.; de Arcangelis, L.; Herrmann, H. J.

    2016-01-01

    Neuronal avalanches measured in vitro and in vivo in different cortical networks consistently exhibit power law behaviour for the size and duration distributions with exponents typical for a mean field self-organized branching process. These exponents are also recovered in neuronal network simulations implementing various neuronal dynamics on different network topologies. They can therefore be considered a very robust feature of spontaneous neuronal activity. Interestingly, this scaling behaviour is also observed on regular lattices in finite dimensions, which raises the question about the origin of the mean field behavior observed experimentally. In this study we provide an answer to this open question by investigating the effect of activity dependent plasticity in combination with the neuronal refractory time in a neuronal network. Results show that the refractory time hinders backward avalanches forcing a directed propagation. Hebbian plastic adaptation plays the role of sculpting these directed avalanche patterns into the topology of the network slowly changing it into a branched structure where loops are marginal. PMID:27534901

  2. Shape optimization of a pressure vessel under plastic flow, plastic instability, weight and fatigue life criteria

    NASA Astrophysics Data System (ADS)

    El Abdi, R.; Touratier, M.; Convert, P.; Lalanne, B.

    1994-06-01

    The structural shape optimization of a complex shell under complex criteria is presented. The shell is one of various cases of a turboshaft, and optimization criteria are associated with the cost, the technology, and above all the working conditions for the turboshaft. Optimization criteria involved are of course the weight of the structure, but also the plastic flow, plastic instability and fatigue life. The fatigue life criterion is an extension to the three-dimensional state of the one-dimensional Lemaitre-Chaboche rule, taking into account the elasto-plastic Neuber correction. All computations have been made with the ANSYS finite element program in which an optimization module exists.

  3. Detecting plastics in seedcotton

    Technology Transfer Automated Retrieval System (TEKTRAN)

    To increase global market share and value the US cotton industry needs to supply cotton lint that is free of contamination. Removing plastic contamination first requires developing a means to detect plastics in seedcotton. This study was conducted to validate a custom Ion Mobility Spectrometer (IM...

  4. Detecting plastics in seedcotton

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The US cotton industry wants to increase market share and value by supplying pure cotton. Removing contamination requires developing a means to detect plastics in seedcotton. This study was conducted to determine if Ion Mobility Spectrometry (IMS) could be used to find small amounts of plastic in ...

  5. Biodegradation of plastics.

    PubMed

    Shimao, M

    2001-06-01

    Widespread studies on the biodegradation of plastics have been carried out in order to overcome the environmental problems associated with synthetic plastic waste. Recent work has included studies of the distribution of synthetic polymer-degrading microorganisms in the environment, the isolation of new microorganisms for biodegradation, the discovery of new degradation enzymes, and the cloning of genes for synthetic polymer-degrading enzymes.

  6. Track recording plastic compositions

    NASA Technical Reports Server (NTRS)

    Tarle, Gregory (Inventor)

    1983-01-01

    Improved nuclear track recording plastic compositions are provided which exhibit greatly decreased surface roughness when etched to produce visible tracks of energetic nuclear particles which have passed into and/or through said plastic. The improved compositions incorporate a small quantity of a phthalic acid ester into the major plastic component which is derived from the polymerization of monomeric di-ethylene glycol bis allyl carbonate. Di-substituted phthalic acid esters are preferred as the added component, with the further perference that the ester substituent has a chain length of 2 or more carbon atoms. The inclusion of the phthalic acid ester to an extent of from about 1-2% by weight of the plastic compositions is sufficient to drastically reduce the surface roughness ordinarily produced when the track recording plastic is contacted by etchants.

  7. Smart film actuators using biomass plastic

    NASA Astrophysics Data System (ADS)

    Yoneyama, Satoshi; Tanaka, Nobuo

    2011-04-01

    This paper presents a novel smart film actuator based on the use of a biomass plastic as a piezoelectric film. Conventional polymeric smart sensors and actuators have been based upon synthetic piezoelectric polymer films such as PVDF. Almost all synthetic polymers are made from nearly depleted oil resources. In addition combustion of their materials releases carbon dioxide, thereby contributing to global warming. Thus at least two important sustainability principles are violated when employing synthetic polymers: avoiding depletable resources and avoiding ecosystem destruction. To overcome such problems, industrial plastic products made from synthetic polymers were developed to replace oil-based plastics with biomass plastics. This paper applies a biomass plastic with piezoelectricity such as poly-L-lactic acid (PLLA). As a result, PLLA film becomes a distributed parameter actuator per se, hence an environmentally conscious smart film actuator is developed. Firstly, this paper overviews the fundamental properties of piezoelectric synthetic polymers and biopolymers. The concept of carbon neutrality using biopolymers is mentioned. Then a two-dimensional modal actuator for exciting a specific structural mode is proposed. Furthermore, a biomass plastic-based cantilever beam with the capability of modal actuation is developed, the validity of the proposed smart film actuator based upon a biomass plastic being analytically as well as experimentally verified.

  8. American Society of Plastic Surgeons

    MedlinePlus

    ... that instill confidence. Do Your Homework Patient Safety Plastic Surgery When you choose a doctor who is ... to procedure selector Why Choose A Board Certified Plastic Surgeon Choose a board-certified plastic surgeon and ...

  9. MeCP2 regulates activity-dependent transcriptional responses in olfactory sensory neurons

    PubMed Central

    Lee, Wooje; Yun, Jung-Mi; Woods, Rima; Dunaway, Keith; Yasui, Dag H.; Lasalle, Janine M.; Gong, Qizhi

    2014-01-01

    During postnatal development, neuronal activity controls the remodeling of initially imprecise neuronal connections through the regulation of gene expression. MeCP2 binds to methylated DNA and modulates gene expression during neuronal development and MECP2 mutation causes the autistic disorder Rett syndrome. To investigate a role for MeCP2 in neuronal circuit refinement and to identify activity-dependent MeCP2 transcription regulations, we leveraged the precise organization and accessibility of olfactory sensory axons to manipulation of neuronal activity through odorant exposure in vivo. We demonstrate that olfactory sensory axons failed to develop complete convergence when Mecp2 is deficient in olfactory sensory neurons (OSNs) in an otherwise wild-type animal. Furthermore, we demonstrate that expression of selected adhesion genes was elevated in Mecp2-deficient glomeruli, while acute odor stimulation in control mice resulted in significantly reduced MeCP2 binding to these gene loci, correlating with increased expression. Thus, MeCP2 is required for both circuitry refinement and activity-dependent transcriptional responses in OSNs. PMID:25008110

  10. Secreted frizzled-related protein 3 regulates activity-dependent adult hippocampal neurogenesis.

    PubMed

    Jang, Mi-Hyeon; Bonaguidi, Michael A; Kitabatake, Yasuji; Sun, Jiaqi; Song, Juan; Kang, Eunchai; Jun, Heechul; Zhong, Chun; Su, Yijing; Guo, Junjie U; Wang, Marie Xun; Sailor, Kurt A; Kim, Ju-Young; Gao, Yuan; Christian, Kimberly M; Ming, Guo-li; Song, Hongjun

    2013-02-07

    Adult neurogenesis, the process of generating mature neurons from adult neural stem cells, proceeds concurrently with ongoing neuronal circuit activity and is modulated by various physiological and pathological stimuli. The niche mechanism underlying the activity-dependent regulation of the sequential steps of adult neurogenesis remains largely unknown. Here, we report that neuronal activity decreases the expression of secreted frizzled-related protein 3 (sFRP3), a naturally secreted Wnt inhibitor highly expressed by adult dentate gyrus granule neurons. Sfrp3 deletion activates quiescent radial neural stem cells and promotes newborn neuron maturation, dendritic growth, and dendritic spine formation in the adult mouse hippocampus. Furthermore, sfrp3 reduction is essential for activity-induced adult neural progenitor proliferation and the acceleration of new neuron development. Our study identifies sFRP3 as an inhibitory niche factor from local mature dentate granule neurons that regulates multiple phases of adult hippocampal neurogenesis and suggests an interesting activity-dependent mechanism governing adult neurogenesis via the acute release of tonic inhibition.

  11. Evidence supporting the existence of an activity-dependent astrocyte-neuron lactate shuttle.

    PubMed

    Pellerin, L; Pellegri, G; Bittar, P G; Charnay, Y; Bouras, C; Martin, J L; Stella, N; Magistretti, P J

    1998-01-01

    Mounting evidence from in vitro experiments indicates that lactate is an efficient energy substrate for neurons and that it may significantly contribute to maintain synaptic transmission, particularly during periods of intense activity. Since lactate does not cross the blood-brain barrier easily, blood-borne lactate cannot be a significant source. In vitro studies by several laboratories indicate that astrocytes release large amounts of lactate. In 1994, we proposed a mechanism whereby lactate could be produced by astrocytes in an activity-dependent, glutamate-mediated manner. Over the last 2 years we have obtained further evidence supporting the notion that a transfer of lactate from astrocytes to neurons might indeed take place. In this article, we first review data showing the presence of mRNA encoding for two monocarboxylate transporters, MCT1 and MCT2, in the adult mouse brain. Second, by using monoclonal antibodies selectively directed against the two distinct lactate dehydrogenase isoforms, LDH1 and LDH5, a specific cellular distribution between neurons and astrocytes is revealed which suggests that a population of astrocytes is a lactate 'source' while neurons may be a lactate 'sink'. Third, we provide biochemical evidence that lactate is interchangeable with glucose to support oxidative metabolism in cortical neurons. This set of data is consistent with the existence of an activity-dependent astrocyte-neuron lactate shuttle for the supply of energy substrates to neurons.

  12. KIF4 motor regulates activity-dependent neuronal survival by suppressing PARP-1 enzymatic activity.

    PubMed

    Midorikawa, Ryosuke; Takei, Yosuke; Hirokawa, Nobutaka

    2006-04-21

    In brain development, apoptosis is a physiological process that controls the final numbers of neurons. Here, we report that the activity-dependent prevention of apoptosis in juvenile neurons is regulated by kinesin superfamily protein 4 (KIF4), a microtubule-based molecular motor. The C-terminal domain of KIF4 is a module that suppresses the activity of poly (ADP-ribose) polymerase-1 (PARP-1), a nuclear enzyme known to maintain cell homeostasis by repairing DNA and serving as a transcriptional regulator. When neurons are stimulated by membrane depolarization, calcium signaling mediated by CaMKII induces dissociation of KIF4 from PARP-1, resulting in upregulation of PARP-1 activity, which supports neuron survival. After dissociation from PARP-1, KIF4 enters into the cytoplasm from the nucleus and moves to the distal part of neurites in a microtubule-dependent manner. We suggested that KIF4 controls the activity-dependent survival of postmitotic neurons by regulating PARP-1 activity in brain development.

  13. Reducing diffusion induced stress in planar electrodes by plastic shakedown and cyclic plasticity of current collector

    NASA Astrophysics Data System (ADS)

    Song, Yicheng; Li, Zongzan; Zhang, Junqian

    2014-10-01

    This paper proposes a strategy to reduce the diffusion induced stress and enhance the capacity of a layered electrode by allowing the plastic deformation of current collector. Based on analytical formulations of the stress in whole electrode, three types of elastoplastic behaviors of current collector, i.e. pure elastic deformation, plastic shakedown and cyclic plasticity, are identified. Criterions separating the three cases are proposed. It is found applying a thin current collector and allowing it to plastically yield in the charge/discharge cycles is beneficial not only to capacity as more space can be provided for active materials but also to electrochemical stability because the stress in active layer is significantly reduced. Structural design corresponding to plastic shakedown shows good balance between the said improvements and structural safety, whereas the case of cyclic plasticity further enhances the improvements. Therefore, structural designing scheme is provided for the former case according to the criterion of plastic shakedown but for the latter one based on the Coffin-Manson relation with expected cycle life.

  14. Short-Term Synaptic Plasticity at Interneuronal Synapses Could Sculpt Rhythmic Motor Patterns

    PubMed Central

    Jia, Yan; Parker, David

    2016-01-01

    The output of a neuronal network depends on the organization and functional properties of its component cells and synapses. While the characterization of synaptic properties has lagged cellular analyses, a potentially important aspect in rhythmically active networks is how network synapses affect, and are in turn affected by, network activity. This could lead to a potential circular interaction where short-term activity-dependent synaptic plasticity is both influenced by and influences the network output. The analysis of synaptic plasticity in the lamprey locomotor network was extended here to characterize the short-term plasticity of connections between network interneurons and to try and address its potential network role. Paired recordings from identified interneurons in quiescent networks showed synapse-specific synaptic properties and plasticity that supported the presence of two hemisegmental groups that could influence bursting: depression in an excitatory interneuron group, and facilitation in an inhibitory feedback circuit. The influence of activity-dependent synaptic plasticity on network activity was investigated experimentally by changing Ringer Ca2+ levels, and in a simple computer model. A potential caveat of the experimental analyses was that changes in Ringer Ca2+ (and compensatory adjustments in Mg2+ in some cases) could alter several other cellular and synaptic properties. Several of these properties were tested, and while there was some variability, these were not usually significantly affected by the Ringer changes. The experimental analyses suggested that depression of excitatory inputs had the strongest influence on the patterning of network activity. The simulation supported a role for this effect, and also suggested that the inhibitory facilitating group could modulate the influence of the excitatory synaptic depression. Short-term activity-dependent synaptic plasticity has not generally been considered in spinal cord models. These results

  15. Activity-dependent dendritic spine neck changes are correlated with synaptic strength

    PubMed Central

    Araya, Roberto; Vogels, Tim P.; Yuste, Rafael

    2014-01-01

    Most excitatory inputs in the mammalian brain are made on dendritic spines, rather than on dendritic shafts. Spines compartmentalize calcium, and this biochemical isolation can underlie input-specific synaptic plasticity, providing a raison d’etre for spines. However, recent results indicate that the spine can experience a membrane potential different from that in the parent dendrite, as though the spine neck electrically isolated the spine. Here we use two-photon calcium imaging of mouse neocortical pyramidal neurons to analyze the correlation between the morphologies of spines activated under minimal synaptic stimulation and the excitatory postsynaptic potentials they generate. We find that excitatory postsynaptic potential amplitudes are inversely correlated with spine neck lengths. Furthermore, a spike timing-dependent plasticity protocol, in which two-photon glutamate uncaging over a spine is paired with postsynaptic spikes, produces rapid shrinkage of the spine neck and concomitant increases in the amplitude of the evoked spine potentials. Using numerical simulations, we explore the parameter regimes for the spine neck resistance and synaptic conductance changes necessary to explain our observations. Our data, directly correlating synaptic and morphological plasticity, imply that long-necked spines have small or negligible somatic voltage contributions, but that, upon synaptic stimulation paired with postsynaptic activity, they can shorten their necks and increase synaptic efficacy, thus changing the input/output gain of pyramidal neurons. PMID:24982196

  16. Neural plasticity and implications for hand rehabilitation after neurological insult.

    PubMed

    Westlake, Kelly P; Byl, Nancy N

    2013-01-01

    Experience dependent plasticity refers to ability of the brain to adapt to new experiences by changing its structure and function. The purpose of this paper is to provide a brief review the neurophysiological and structural correlates of neural plasticity that occur during and following motor learning. We also consider that the extent of plastic reorganization is dependent upon several key principals and that the resulting behavioral consequences can be adaptive or maladaptive. In light of this research, we conclude that an increased understanding of the complexities of brain plasticity will translate into enhanced treatment opportunities for the clinician to optimize hand function.

  17. Activity-dependent regulation of calcium and ribosomes in the chick cochlear nucleus.

    PubMed

    Call, C L; Hyson, R L

    2016-03-01

    Cochlea removal results in the death of 20-30% of neurons in the chick cochlear nucleus, nucleus magnocellularis (NM). Two potentially cytotoxic events, a dramatic rise in intracellular calcium concentration ([Ca(2+)]i) and a decline in the integrity of ribosomes are observed within 1h of deafferentation. Glutamatergic input from the auditory nerve has been shown to preserve NM neuron health by activating metabotropic glutamate receptors (mGluRs), maintaining both normal [Ca(2+)]i and ribosomal integrity. One interpretation of these results is that a common mGluR-activated signaling cascade is required for the maintenance of both [Ca(2+)]i and ribosomal integrity. This could happen if both responses are influenced directly by a common messenger, or if the loss of mGluR activation causes changes in one component that secondarily causes changes in the other. The present studies tested this common-mediator hypothesis in slice preparations by examining activity-dependent regulation of [Ca(2+)]i and ribosomes in the same tissue after selectively blocking group I mGluRs (1-Aminoindan-1,5-dicarboxylic acid (AIDA)) or group II mGluRs (LY 341495) during unilateral auditory nerve stimulation. Changes in [Ca(2+)]i of NM neurons were measured using fura-2 ratiometric calcium imaging and the tissue was subsequently processed for Y10B immunoreactivity (Y10B-ir), an antibody that recognizes a ribosomal epitope. The group I mGluR antagonist blocked the activity-dependent regulation of both [Ca(2+)]i and Y10B-ir, but the group II antagonist blocked only the activity-dependent regulation of Y10B-ir. That is, even when group II receptors were blocked, stimulation continued to maintain low [Ca(2+)]i, but it did not maintain Y10B-ir. These results suggest a dissociation in how calcium and ribosomes are regulated in NM neurons and that ribosomes can be regulated through a mechanism that is independent of calcium regulation.

  18. VAMP4 Is an Essential Cargo Molecule for Activity-Dependent Bulk Endocytosis.

    PubMed

    Nicholson-Fish, Jessica C; Kokotos, Alexandros C; Gillingwater, Thomas H; Smillie, Karen J; Cousin, Michael A

    2015-12-02

    The accurate formation of synaptic vesicles (SVs) and incorporation of their protein cargo during endocytosis is critical for the maintenance of neurotransmission. During intense neuronal activity, a transient and acute accumulation of SV cargo occurs at the plasma membrane. Activity-dependent bulk endocytosis (ADBE) is the dominant SV endocytosis mode under these conditions; however, it is currently unknown how ADBE mediates cargo retrieval. We examined the retrieval of different SV cargo molecules during intense stimulation using a series of genetically encoded pH-sensitive reporters in neuronal cultures. The retrieval of only one reporter, VAMP4-pHluorin, was perturbed by inhibiting ADBE. This selective recovery was confirmed by the enrichment of endogenous VAMP4 in purified bulk endosomes formed by ADBE. VAMP4 was also essential for ADBE, with a cytoplasmic di-leucine motif being critical for this role. Therefore, VAMP4 is the first identified ADBE cargo and is essential for this endocytosis mode to proceed.

  19. Blurring the boundaries: developmental and activity-dependent determinants of neural circuits

    PubMed Central

    Wolfram, Verena; Baines, Richard A.

    2013-01-01

    The human brain comprises approximately 100 billion neurons that express a diverse, and often subtype-specific, set of neurotransmitters and voltage-gated ion channels. Given this enormous complexity, a fundamental question is how is this achieved? The acquisition of neurotransmitter phenotype was viewed as being set by developmental programs ‘hard wired’ into the genome. By contrast, the expression of neuron-specific ion channels was considered to be highly dynamic (i.e., ‘soft wired’) and shaped largely by activity-dependent mechanisms. Recent evidence blurs this distinction by showing that neurotransmitter phenotype can be altered by activity and that neuron type-specific ion channel expression can be set, and perhaps limited by, developmental programs. Better understanding of these early regulatory mechanisms may offer new avenues to avert the behavioral changes that are characteristic of many mental illnesses. PMID:23876426

  20. Activity-Dependent Synaptic Competition in Vitro: Heterosynaptic Suppression of Developing Synapses

    NASA Astrophysics Data System (ADS)

    Lo, Yi-Jiuan; Poo, Mu-Ming

    1991-11-01

    The development and stability of synaptic connections in the nervous system are influenced by the pattern of electrical activity and the competitive interaction between the adjacent nerve terminals. To investigate this influence, a culture system of nerve and muscle cells has been developed in which a single embryonic muscle cell is coinnervated by two spinal neurons. The effect of electrical activity on the synaptic efficacy was examined after repetitive electrical stimulation was applied to one or both neurons. Brief tetanic stimulation of one neuron resulted in immediate functional suppression of the synapse made by the unstimulated neuron innervating the same muscle cell. This heterosynaptic suppression was largely absent when the tetanic stimulation was applied concurrently to both neurons. This result demonstrates that activity-dependent synaptic competition can be studied in vitro at a cellular level.

  1. Timothy syndrome is associated with activity-dependent dendritic retraction in rodent and human neurons.

    PubMed

    Krey, Jocelyn F; Paşca, Sergiu P; Shcheglovitov, Aleksandr; Yazawa, Masayuki; Schwemberger, Rachel; Rasmusson, Randall; Dolmetsch, Ricardo E

    2013-02-01

    L-type voltage gated calcium channels have an important role in neuronal development by promoting dendritic growth and arborization. A point mutation in the gene encoding Ca(V)1.2 causes Timothy syndrome, a neurodevelopmental disorder associated with autism spectrum disorders (ASDs). We report that channels with the Timothy syndrome alteration cause activity-dependent dendrite retraction in rat and mouse neurons and in induced pluripotent stem cell (iPSC)-derived neurons from individuals with Timothy syndrome. Dendrite retraction was independent of calcium permeation through the mutant channel, was associated with ectopic activation of RhoA and was inhibited by overexpression of the channel-associated GTPase Gem. These results suggest that Ca(V)1.2 can activate RhoA signaling independently of Ca(2+) and provide insights into the cellular basis of Timothy syndrome and other ASDs.

  2. Slow State Transitions of Sustained Neural Oscillations by Activity-Dependent Modulation of Intrinsic Excitability

    PubMed Central

    Fröhlich, Flavio; Bazhenov, Maxim; Timofeev, Igor; Steriade, Mircea; Sejnowski, Terrence J.

    2010-01-01

    Little is known about the dynamics and mechanisms of transitions between tonic firing and bursting in cortical networks. Here, we use a computational model of a neocortical circuit with extracellular potassium dynamics to show that activity-dependent modulation of intrinsic excitability can lead to sustained oscillations with slow transitions between two distinct firing modes: fast run (tonic spiking or fast bursts with few spikes) and slow bursting. These transitions are caused by a bistability with hysteresis in a pyramidal cell model. Balanced excitation and inhibition stabilizes a network of pyramidal cells and inhibitory interneurons in the bistable region and causes sustained periodic alternations between distinct oscillatory states. During spike-wave seizures, neocortical paroxysmal activity exhibits qualitatively similar slow transitions between fast run and bursting. We therefore predict that extracellular potassium dynamics can cause alternating episodes of fast and slow oscillatory states in both normal and epileptic neocortical networks. PMID:16763023

  3. Activity-dependent modulation of inhibitory synaptic kinetics in the cochlear nucleus

    PubMed Central

    Nerlich, Jana; Keine, Christian; Rübsamen, Rudolf; Burger, R. Michael; Milenkovic, Ivan

    2014-01-01

    Spherical bushy cells (SBCs) in the anteroventral cochlear nucleus respond to acoustic stimulation with discharges that precisely encode the phase of low-frequency sound. The accuracy of spiking is crucial for sound localization and speech perception. Compared to the auditory nerve input, temporal precision of SBC spiking is improved through the engagement of acoustically evoked inhibition. Recently, the inhibition was shown to be less precise than previously understood. It shifts from predominantly glycinergic to synergistic GABA/glycine transmission in an activity-dependent manner. Concurrently, the inhibition attains a tonic character through temporal summation. The present study provides a comprehensive understanding of the mechanisms underlying this slow inhibitory input. We performed whole-cell voltage clamp recordings on SBCs from juvenile Mongolian gerbils and recorded evoked inhibitory postsynaptic currents (IPSCs) at physiological rates. The data reveal activity-dependent IPSC kinetics, i.e., the decay is slowed with increased input rates or recruitment. Lowering the release probability yielded faster decay kinetics of the single- and short train-IPSCs at 100 Hz, suggesting that transmitter quantity plays an important role in controlling the decay. Slow transmitter clearance from the synaptic cleft caused prolonged receptor binding and, in the case of glycine, spillover to nearby synapses. The GABAergic component prolonged the decay by contributing to the asynchronous vesicle release depending on the input rate. Hence, the different factors controlling the amount of transmitters in the synapse jointly slow the inhibition during physiologically relevant activity. Taken together, the slow time course is predominantly determined by the receptor kinetics and transmitter clearance during short stimuli, whereas long duration or high frequency stimulation additionally engage asynchronous release to prolong IPSCs. PMID:25565972

  4. Activity-Dependent Degradation of Synaptic Vesicle Proteins Requires Rab35 and the ESCRT Pathway

    PubMed Central

    Sheehan, Patricia; Zhu, Mei; Beskow, Anne; Vollmer, Cyndel

    2016-01-01

    Synaptic vesicle (SV) pools must maintain a functional repertoire of proteins to efficiently release neurotransmitter. The accumulation of old or damaged proteins on SV membranes is linked to synaptic dysfunction and neurodegeneration. However, despite the importance of SV protein turnover for neuronal health, the molecular mechanisms underlying this process are largely unknown. Here, we have used dissociated rat hippocampal neurons to investigate the pathway for SV protein degradation. We find that neuronal activity drives the degradation of a subset of SV proteins and that the endosomal sorting complex required for transport (ESCRT) machinery and SV-associated GTPase Rab35 are key elements of this use-dependent degradative pathway. Specifically, neuronal activity induces Rab35 activation and binding to the ESCRT-0 protein Hrs, which we have identified as a novel Rab35 effector. These actions recruit the downstream ESCRT machinery to SV pools, thereby initiating SV protein degradation via the ESCRT pathway. Our findings show that the Rab35/ESCRT pathway facilitates the activity-dependent removal of specific proteins from SV pools, thereby maintaining presynaptic protein homeostasis. SIGNIFICANCE STATEMENT Synaptic transmission is mediated by the release of chemical neurotransmitters from synaptic vesicles (SVs). This tightly regulated process requires a functional pool of SVs, necessitating cellular mechanisms for removing old or damaged proteins that could impair SV cycling. Here, we show that a subset of SV proteins is degraded in an activity-dependent manner and that key steps in this degradative pathway are the activation of the small GTPase Rab35 and the subsequent recruitment of the endosomal sorting complex required for transport (ESCRT) machinery to SV pools. Further, we demonstrate that ESCRT-0 component Hrs is an effector of Rab35, thus providing novel mechanistic insight into the coupling of neuronal activity with SV protein degradation and the

  5. Mechanical plasticity of cells

    NASA Astrophysics Data System (ADS)

    Bonakdar, Navid; Gerum, Richard; Kuhn, Michael; Spörrer, Marina; Lippert, Anna; Schneider, Werner; Aifantis, Katerina E.; Fabry, Ben

    2016-10-01

    Under mechanical loading, most living cells show a viscoelastic deformation that follows a power law in time. After removal of the mechanical load, the cell shape recovers only incompletely to its original undeformed configuration. Here, we show that incomplete shape recovery is due to an additive plastic deformation that displays the same power-law dynamics as the fully reversible viscoelastic deformation response. Moreover, the plastic deformation is a constant fraction of the total cell deformation and originates from bond ruptures within the cytoskeleton. A simple extension of the prevailing viscoelastic power-law response theory with a plastic element correctly predicts the cell behaviour under cyclic loading. Our findings show that plastic energy dissipation during cell deformation is tightly linked to elastic cytoskeletal stresses, which suggests the existence of an adaptive mechanism that protects the cell against mechanical damage.

  6. Shape-Shifting Plastic

    SciTech Connect

    2015-05-20

    A new plastic developed by ORNL and Washington State University transforms from its original shape through a series of temporary shapes and returns to its initial form. The shape-shifting process is controlled through changes in temperature

  7. A Plastic Menagerie

    ERIC Educational Resources Information Center

    Hadley, Mary Jane

    2010-01-01

    Bobble heads had become quite popular, depicting all sorts of sports figures, animals, and even presidents. In this article, the author describes how her fourth graders made bobble head sculptures out of empty plastic drink bottles. (Contains 1 online resource.)

  8. Strain avalanches in plasticity

    NASA Astrophysics Data System (ADS)

    Argon, A. S.

    2013-09-01

    Plastic deformation at the mechanism level in all solids occurs in the form of discrete thermally activated individual stress relaxation events. While there are clear differences in mechanisms between dislocation mediated events in crystalline solids and by individual shear transformations in amorphous metals and semiconductors, such relaxation events interact strongly to form avalanches of strain bursts. In all cases the attendant distributions of released energy as amplitudes of acoustic emissions, or in serration amplitudes in flow stress, the levels of strain bursts are of fractal character with fractal exponents in the range from -1.5 to -2.0, having the character of phenomena of self-organized criticality, SOC. Here we examine strain avalanches in single crystals of ice, hcp metals, the jerky plastic deformations of nano-pillars of fcc and bcc metals deforming in compression, those in the plastic flow of bulk metallic glasses, all demonstrating the remarkable universality of character of plastic relaxation events.

  9. Dreaming in plastic

    NASA Astrophysics Data System (ADS)

    Korzhov, Marianna; Andelman, David; Shikler, Rafi

    2008-07-01

    Plastic is one of the most versatile materials available. It is cheap, flexible and easy to process, and as a result it is all around us - from our computer keyboards to the soles of our shoes. One of its most common applications is as an insulating coating for electric wires; indeed, plastic is well known for its insulating characteristics. It came as something of a surprise, therefore, when in the late 1970s a new generation of plastics was discovered that displayed exactly the opposite behaviour - the ability to conduct electricity. In fact, plastics can be made with a whole range of conductivities - there are polymer materials that behave like semiconductors and there are those that can conduct as well as metals. This discovery sparked a revolution in the electronics community, and three decades of research effort is now yielding a range of stunning new applications for this ubiquitous material.

  10. How plastic can phenotypic plasticity be? The branching coral Stylophora pistillata as a model system.

    PubMed

    Shaish, Lee; Abelson, Avigdor; Rinkevich, Baruch

    2007-07-25

    Phenotypic plasticity enables multicellular organisms to adjust morphologies and various life history traits to variable environmental challenges. Here, we elucidate fixed and plastic architectural rules for colony astogeny in multiple types of colonial ramets, propagated by cutting from genets of the branching coral Stylophora pistillata from Eilat, the Red Sea. We examined 16 morphometric parameters on 136 one-year old S. pistillata colonies (of seven genotypes), originating from small fragments belonging, each, to one of three single-branch types (single tips, start-up, and advanced bifurcating tips) or to structural preparative manipulations (representing a single or two growth axes). Experiments were guided by the rationale that in colonial forms, complexity of evolving phenotypic plasticity can be associated with a degree of structural modularity, where shapes are approached by erecting iterative growth patterns at different levels of coral-colony organization. Analyses revealed plastic morphometric characters at branch level, and predetermined morphometric traits at colony level (only single trait exhibited plasticity under extreme manipulation state). Therefore, under the experimental manipulations of this study, phenotypic plasticity in S. pistillata appears to be related to branch level of organization, whereas colony traits are controlled by predetermined genetic architectural rules. Each level of organization undergoes its own mode of astogeny. However, depending on the original ramet structure, the spherical 3-D colonial architecture in this species is orchestrated and assembled by both developmental trajectories at the branch level, and traits at the colony level of organization. In nature, branching colonial forms are often subjected to harsh environmental conditions that cause fragmentation of colony into ramets of different sizes and structures. Developmental traits that are plastic, responding to fragment structure and are not predetermine in

  11. Laser cutting plastic materials

    SciTech Connect

    Van Cleave, R.A.

    1980-08-01

    A 1000-watt CO/sub 2/ laser has been demonstrated as a reliable production machine tool for cutting of plastics, high strength reinforced composites, and other nonmetals. More than 40 different plastics have been laser cut, and the results are tabulated. Applications for laser cutting described include fiberglass-reinforced laminates, Kevlar/epoxy composites, fiberglass-reinforced phenolics, nylon/epoxy laminates, ceramics, and disposable tooling made from acrylic.