• Title, Summary, Keyword: synapse

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Actin Engine in Immunological Synapse

  • Piragyte, Indre;Jun, Chang-Duk
    • IMMUNE NETWORK
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    • v.12 no.3
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    • pp.71-83
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    • 2012
  • T cell activation and function require physical contact with antigen presenting cells at a specialized junctional structure known as the immunological synapse. Once formed, the immunological synapse leads to sustained T cell receptor-mediated signalling and stabilized adhesion. High resolution microscopy indeed had a great impact in understanding the function and dynamic structure of immunological synapse. Trends of recent research are now moving towards understanding the mechanical part of immune system, expanding our knowledge in mechanosensitivity, force generation, and biophysics of cell-cell interaction. Actin cytoskeleton plays inevitable role in adaptive immune system, allowing it to bear dynamic and precise characteristics at the same time. The regulation of mechanical engine seems very complicated and overlapping, but it enables cells to be very sensitive to external signals such as surface rigidity. In this review, we focus on actin regulators and how immune cells regulate dynamic actin rearrangement process to drive the formation of immunological synapse.

A Study on the Linearity Synapse Transistor in Self Learning Neural Network (자기인지 신경회로망에서 선형 시냅스 트랜지스터에 관한 연구)

  • 강창수;김동진;김영호
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • pp.59-62
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    • 2000
  • A VLSI implementation of a self-learning neural network integrated circuits using a linearity synapse transistor is investigated. The thickness dependence of oxide current density, stress current, transient current and channel current has been measured in oxides with thicknesses between 41 and 112 $\AA$, which have the channel width$\times$length 10$\times$1${\mu}{\textrm}{m}$ respectively. The transient current will affect data retention in synapse transistors and the stress current is used to estimate to fundamental limitations on oxide thicknesses. The synapse transistor has represented the neural states and the manipulation which gave unipolar weights. The weight value of synapse transistor was caused by the bias conditions. Excitatory state and inhitory state according to weighted values affected the drain source current.

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A Study on the Linearity Synapse Transistor of Analog Memory Devices in Self Learning Neural Network Integrated Circuits (자기인지 신경회로망에서 아날로그 기억소자의 선형 시냅스 트랜지스터에 관한연구)

  • 강창수
    • Electrical & Electronic Materials
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    • v.10 no.8
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    • pp.783-793
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    • 1997
  • A VLSI implementation of a self-learning neural network integrated circuits using a linearity synapse transistor is investigated. The thickness dependence of oxide current density stress current transient current and channel current has been measured in oxides with thicknesses between 41 and 112 $\AA$, which have the channel width $\times$ length 10 $\times$1${\mu}{\textrm}{m}$, 10 $\times$ 0.3${\mu}{\textrm}{m}$ respectively. The transient current will affect data retention in synapse transistors and the stress current is used to estimate to fundamental limitations on oxide thicknesses. The synapse transistor has represented the neural states and the manipulation which gaves unipolar weights. The weight value of synapse transistor was caused by the bias conditions. Excitatory state and inhitory state according to weighted values affected the drain source current.

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A Study on the Synaptic Characteristics of SONOS memories for the Artificial Neural Networks (인공신경망을 위한 SONOS 기억소자의 시냅스특성에 관한 연구)

  • 이성배;김주연;서광열
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.11 no.1
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    • pp.7-11
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    • 1998
  • In this paper, a new synapse cell with nonvolatile SONOS semiconductor memory device is proposed and it's fundamental function electronically implemented SONOS NVSM has shown characteristics that the memory value, synaptic weights, can be increased or decreased incrementally. A novel SONOS synapse is used to read out the stored analog value. For the purpose of synapse implementation using SONOS NVSM, this work has investigated multiplying characteristics including weight updating characteristics and neuron output characteristics. It is concluded that SONOS synapse cell has good agreement for use as a synapse in artificial neural networks.

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Ultrastructural Pattern of Synapses in the Rat Neostriatum during Postnatal Development (출생후 성장과정의 흰쥐 새줄무늬체에서 신경연접의 구조적 변동)

  • Lee, Hee-Lai
    • Applied Microscopy
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    • v.25 no.4
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    • pp.1-8
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    • 1995
  • This study was performed to analyze the morphological changes of synapses during early postnatal periods. Neonatal rats were grouped by 3, 7, 14, 21, 28 and 42day old, and observed the ultrastructural pattern of the synapses in the neostriatum by transmission electron microscope. 1. The number of synapse, the length of postsynaptic thickening and the amount of synaptic vesicles markedly increase during postnatal development 2. The proportion of asymmetric and curved synapses gradually increase by developmental periods. From the above results, it is suggested that the size of synapse increase during post-natal period, and asymmetric synapse are formed from the symmetric type and curved synapse are formed from the plane type.

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Silver Impregnation and Electron Microscopic Studies on the Synapse in the Visual Cortex of Rat during Postnatal Development (성장기 흰쥐 시각피질의 신경연접에 대한 도은법 및 전자현미경적 연구)

  • Lee, Hee-Lai
    • Applied Microscopy
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    • v.27 no.4
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    • pp.347-355
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    • 1997
  • These studies were performed to observe the morphological changes of synapses in the visual cortex of rat during early postnatal development. Specimens of the visual cortex were taken from rats (Sprague Dawley) at 1, 3, 7, 14 and 21 days of age, and prepared for silver impregnation and electron microscopy. The number of synapse and the length of postsynaptic thickening were increased progressively with age, especially 14 and 21 days. The number of dendritic spine was increased conspicuously on postnatal days 14-21. And asymmetic, curved and axo-spinous synapses were increased markedly at the same ages. The present findings suggest that spurt of synaptogenesis in the rat visual cortex occurs during early postnatal development, especially in second to 3rd week period and asymmetric and/or curved axo-spinous synapse is a matured form of synapse with advanced age.

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TAGLN2-mediated actin stabilization at the immunological synapse: implication for cytotoxic T cell control of target cells

  • Na, Bo-Ra;Jun, Chang-Duk
    • BMB Reports
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    • v.48 no.7
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    • pp.369-370
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    • 2015
  • Actin dynamics is critical for the formation and sustainment of the immunological synapse (IS) during T cell interaction with antigen-presenting cells (APC). Thus, many actin regulating proteins are involved in spatial and temporal actin remodeling at the IS. However, little is known whether or how actin stabilizing protein controls IS and the consequent T cell functions. TAGLN2 − an actin-binding protein predominantly expressed in T cells − displays a novel function to stabilize cortical F-actin, thereby augmenting F-actin contents at the IS, and acquiring leukocyte function-associated antigen-1 activation following T cell activation. TAGLN2 also competes with cofilin to protect F-actin in vitro and in vivo. During cytotoxic T cell interaction with cancer cells, the expression level of TAGLN2 at the IS correlates with the T cell adhesion to target cancer cells and production of lytic granules such as granzyme B and perforin, thus expressing cytotoxic T cell function. These findings identify a novel function for TAGLN2 as an actin stabilizing protein that is essential for stable immunological synapse formation, thereby regulating T cell immunity. [BMB Reports 2015; 48(7): 369-370]

The Characteristics of Silicon Oxides for Artificial Neural Network Design (인공신경회로망 설계를 위한 실리콘 산화막 특성)

  • Kang, C.S.
    • Proceedings of the IEEK Conference
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    • pp.475-476
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    • 2007
  • The stress induced leakage currents will affect data retention in synapse transistors and the stress current, transient current is used to estimate to fundamental limitations on oxide thicknesses. The synapse transistor made by thin silicon oxides has represented the neural states and the manipulation which gaves unipolar weights. The weight value of synapse transistor was caused by the bias conditions. Excitatory state and inhibitory state according to weighted values affected the channel current. The stress induced leakage currents affected excitatory state and inhibitory state.

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Molecular Mechanisms of Synaptic Specificity: Spotlight on Hippocampal and Cerebellar Synapse Organizers

  • Park, Dongseok;Bae, Sungwon;Yoon, Taek Han;Ko, Jaewon
    • Molecules and Cells
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    • v.41 no.5
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    • pp.373-380
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    • 2018
  • Synapses and neural circuits form with exquisite specificity during brain development to allow the precise and appropriate flow of neural information. Although this property of synapses and neural circuits has been extensively investigated for more than a century, molecular mechanisms underlying this property are only recently being unveiled. Recent studies highlight several classes of cell-surface proteins as organizing hubs in building structural and functional architectures of specific synapses and neural circuits. In the present minireview, we discuss recent findings on various synapse organizers that confer the distinct properties of specific synapse types and neural circuit architectures in mammalian brains, with a particular focus on the hippocampus and cerebellum.

Swiprosin-1 Expression Is Up-Regulated through Protein Kinase $C-{\theta}$ and $NF-{\kappa}B$ Pathway in T Cells

  • Kim, Young-Dae;Kwon, Min-Sung;Na, Bo-Ra;Kim, Hye-Ran;Lee, Hyun-Su;Jun, Chang-Duk
    • IMMUNE NETWORK
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    • v.13 no.2
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    • pp.55-62
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    • 2013
  • Swiprosin-1 exhibits the highest expression in $CD8^+$ T cells and immature B cells and has been proposed to play a role in lymphocyte biology through actin remodeling. However, regulation of swiprosin-1 gene expression is poorly understood. Here we report that swiprosin-1 is up-regulated in T cells by PKC pathway. Targeted inhibition of the specific protein kinase C (PKC) isotypes by siRNA revealed that $PKC-{\theta}$ is involved in the expression of swiprosin-1 in the human T cells. In contrast, down-regulation of swiprosin-1 by A23187 or ionomycin suggests that calcium-signaling plays a negative role. Interestingly, swiprosin-1 expression is only reduced by treatment with $NF-{\kappa}B$ inhibitors but not by NF-AT inhibitor, suggesting that the $NF-{\kappa}B$ pathway is critical for regulation of swiprosin-1 expression. Collectively, these results suggest that swiprosin-1 is a $PKC-{\theta}$-inducible gene and that it may modulate the late phase of T cell activation after antigen challenge.