• Applied Microscopy
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• 제24권4호
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• pp.32-40
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• 1994

This study was undertaken to study the morphological changes of rat synapses during early postnatal periods. Neonatal rats were grouped by 1st, 2nd, 3rd, 4th and 6th postnatal weeks, and we observed the ultrastructural pattern of the synapses in the external plexiform layer of olfactory bulbs by electron microscopy. The results were as follows; 1. The numbers of synapses, lengths of synaptic thickenings and amounts of synaptic vesicles were markedly increased in the external plexiform layer during four postnatal weeks. 2. There was a tendency of increasing the proportion of the asymmetric synapse and the curved synapses during maturation. From the above results, it is suggested that the size of synapse is increasing during maturation, and at the same time the asymmetric synapses are formed from the symmetric type and the curved synapses are from the plane type.

• Applied Microscopy
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• 제36권2호
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• pp.83-91
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• 2006

신경연접은 다양한 생리적 또는 병적 상태에 반응하여 구조 및 수적 변화를 보이며, 신경연접의 밀도 변화는 신경세포의 활성 조절에 중요한 역할을 하는 것으로 알려져 있다. 따라서 특정 생리적 또는 병적 상태에서 신경연접의 밀도 변화를 명확히 이해하기 위해서는 정확한 정량방법을 이용한 밀도 측정이 필수적이다. 본 연구에서는 physical disector법을 이용하여 흰쥐 뇌의 치아이랑에 위치하는 과립신경세포의 신경연접 수를 측정하였으며, 이를 통해 physical disector의 방법적 정확성을 확인하고자 하였다. 성체 흰쥐를 관류고정한 후 치아이랑의 연속 절편을 얻어 통상적인 전자현미경 시료제작법을 통해 Epon 혼합용액에 포매하였다. Physical disector법을 이용한 밀도 분석 시 연속절편의 정렬, 비교 및 disector frame이 필요하므로 Reconstruct 프로그램을 사용하였다. 동물 당 40장의 $1{\mu}m$ 연속절편을 제작하여 과립신경세포체의 밀도를 측정하였으며, 15장의 80nm연속절편으로부터 bidirectional disector법을 이용하여 과립신경세포와 내측 관통로(medial perforant path) 간 신경 연접의 밀도를 분석하였다. 과립신경세포의 세포체와 신경연접은 각각 과립층과 분자층에 위치하기 때문에 하나의 신경세포가 가지는 신경연접의 수를 측정하기 위해서는 각 층의 부피를 고려하는 것이 요구된다. 따라서 과립층에 대한 분자층의 부피비율을 측정하였다. 실험결과, 흰쥐 치아이랑에 위치하는 하나의 과립세포당 약 6,500개의 신경연접의 존재한다는 사실을 확인하였으며, 이는 다른 연구자들의 결과와 유사하였다. 본 연구로부터 physical disector법은 특정 생리적 또는 병적 조건에서 나타나는 신경세포 및 신경연접의 수적 변화를 정확히 측정할 수 있는 유용한 정량방법임을 알 수 있었다. 향후 physical disector법을 이용하여 다양한 실험동물모델의 신경연접 변화를 분석하는 것은 신경연접의 형태적 가소성을 이해하는데 이바지할 것으로 생각된다.

• 한국동물학회지
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• 제31권4호
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• pp.334-343
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• 1988

Five types of synaPses were differentiated in the antennal lobe or Pieris rapoe. aev are in general axo-dendritic synapses and have symmetrical contacts. The type I synapses contain the uniformly round vesicles of medium size, and consist of the 11% of all synapses in the antennal lobe. The type synapses are filled with the small flat and densely arranged (19%). The type III synapses possess medium-sized round vesicles and dense core ones(24%). The type IV synapses are characterized by such three kinds of vesicles as small round, small flat and dense core vesicles(33%). The type V synapses exhibit the presence of medium-sized round, large round and dense core vesicles(13%). The removal of the left antenna on its proximal portion caused the type IV boutons of the above ave types in ipsilateral antennal lobe to turn into dark or semidark degenerative changes. Therefore, it was concluded that many of the antennal receptor cells projected into the brain terminate in the antennal lobe to form type IV synapses together with the dendrites. 배추회나비 뇌의 촉각엽에 있는 신경세포들은 5가지의 신경연접을 형성하는 것으로 관찰되었다. 이 신경연접들은 모두 축색과 수상돌기간의 연접으로 대칭연접이었다. 제1형 신경연접은 축색종말내에 중등도크기의 단형 연접소포를 가지고 있었고, 촉각엽에 있는 5가지의 신경연접중 11%의 출현빈도수로 관찰되었다. 제2형 신경연접의 축색종말에는 장형과 도형의 2가지 연접소포가 포함되어 있었는데, 모두 소형이었으며 이같은 연접소포들이 축색 종말내에서 조밀하게 관찰되었다. 제2형 신경연접의 출현 빈도수는 19%이었다. 제3형 신경연접은 축색 종말내에 중등도크기의 도형 연접소포와 DENSE CORE VESICLE을 포함하고 있었고 그 출현빈도수는 24%이었다. 제4형 신경연접은 축색총말내에 소형의 도형, 소형의 장형 연접소포 및 DENSE CORE VESICLE의 3가지 연접소포를 가지고 있었고 출현빈도수는 촉각엽에서 가장 큰 33%이었다. 제5형 신경연접은 축색종말내에 중등도크기의 원형, 대형의 원형연접소포 및 DENSE CORE VESICLE을 포함하였고 13%의 출현빈도수로 관찰되었다. 배추횐나비의 촉각에 있는 지각신경세포가 뇌의 촉각엽으로 뻗어 들어가 위의 5가지 신경연접중 어느 형을 형성하는지를 관찰하기 위하여 좌측 촉각의 기부를 제거하여 지각신경세포를 절단하였는데 그 결과, 좌측 촉각엽에서 제4형의 신경연접이 퇴행성 변화를 나타내었다. 그러므로 촉각의 지각신경세포는 뇌의 같은 족 촉각엽에 뻗어와 제4형 신경연접을 형성한다고 결론되었다.

• Applied Microscopy
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• 제8권1호
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• pp.53-66
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• 1978

An attempt has been made to discriminate the synapses in the striatum consisting caudate nucleus, putamen and fundus striati of the cat with emphasis on the characteristic structures of axon terminals and postsynaptic profiles. The differentiation is based on the size and shape of vesicle in the bouton terminal, and the symmetrical or asymmetrical thickening the pre- and postsynaptic membrane. Four types of synapses could be differentiated: Type I: the bontons with asymmetrical,synaptic thickenings contain round 45 nm diameter vesicles and contact cell soma, dendritic shafts and dendritic spines (74%). Type II : the boutons contain round 45nm diameter vesicles and are associated with symmetrical membrane thickenings. These synapses are formed on the soma and dendritic shafts (6%). Type III: the boutons with symmetrical membrane thickenings contain 50-60 nm diameter pleomorphic vesicles, and contact soma and dendritic shafts (18%). Type IV: the terminals contain flattened vesicles ($25{\times}45 nm$) and are associated with symmetrical membrane thickenings. These synapses are found in contact with soma and dendritic shafts. Additionally, the bouton en passant, which is expanded from myelinated or unmyelinated axons containing round vesicles (45nm diameter) contacts the dendritic shaft or dendritic spine with asymmetrical membrane thickenings. Two unusual types of synapses, axo-axonic and dendro-dendritic, are found occasionally.

• 전자공학회논문지B
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• 제31B권4호
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• pp.155-165
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• 1994

An analog neural network circuit of rhigh density integration is introduced. It's prototype chip is designed in 3 by 3 mm2 die. It uses only one MOSFET to implement a synapse. The number of synapses per neuron can be expanded by cascading several chips. The influence of nonlinearity in synapses is analyzed. A formalization of the back propagation which can be applied to this circuit is shown. Some simulation results are shown and disscussed.

• Applied Microscopy
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• 제25권4호
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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.

• Applied Microscopy
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• 제26권3호
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• pp.329-348
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• 1996

The prenatal development of lateral motor columns in the lumbar spinal cord was studied by electron microscopy in human embryos and fetuses ranging from 9 mm to 260 mm crown-rump length ($5{\sim}30$ weeks of gestational age). At 9 mm embryo, the lateral motor column were developed from ventro-lateral projection into the marginal layer and composed of primitive neuroblasts. At 20 mm embryo the primitive motor neurons were packed closely together and could readly be distinguished from primitive glioblasts by a presence of large nuclei. The primitive multipolar neurons were observed in lateral motor column at 40 mm fetus. At 80 mm fetus multipolar neurons were characterized by their many dendrites and axons in the vicinity of motor neuron perikarya. At 260 mm fetus, the motor neurons were large and contained all intracytoplasmic structures in the cytoplasm which were also found in mature motor neuron in lateral motor column. The first axo-dendritic synapses found at 40 mm fetus and increased in number throughout fetal development. Axo-somatic synapses with spherical vesicles were first observed at 80 mm fetus. A few axo-somatic synapses were found at next prenatal stages. Axo-dendritic and axo-somatic synapses contained mixed populations of spherical and flattened vesicles by 120 mm fetus. These findings indicate that axo-dendritic synapses develop prior to axo-somatic synapses in the spinal cord during neurogenesis.

• BMB Reports
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• 제51권8호
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• pp.369-370
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• 2018

In previous studies, memory storage was localized to engram cells distributed across the brain. While these studies have provided an individual cellular profile of engram cells, their synaptic connectivity, or whether they follow Hebbian mechanisms, remains uncertain. Therefore, our recent study investigated whether synapses between engram cells exhibit selectively enhanced structural and functional properties following memory formation. This was accomplished using a newly developed technique called "dual-eGRASP". We found that the number and size of spines on CA1 engram cells that receive inputs from CA3 engram cells were larger than at other synapses. We further observed that this enhanced connectivity correlated with induced memory strength. CA3 engram synapses exhibited increased release probability, while CA1 engram synapses produced enhanced postsynaptic responses. CA3 engram to CA1 engram projections showed strong occlusion of long-term potentiation. We demonstrated that the synaptic connectivity of CA3 to CA1 engram cells was strengthened following memory formation. Our results suggest that Hebbian plasticity occurs during memory formation among engram cells at the synapse level.

• The Korean Journal of Physiology and Pharmacology
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• 제6권2호
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• pp.81-85
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• 2002

Conventional views of synaptic transmission generally overlook the possibility of 'postfusional-control' the regulation of the speed or completeness of transmitter release upon vesicular fusion. However, such regulation often occurs in non-neuronal cells where the dynamics of fusion-pore opening is critical for the speed of transmitter release. In case of synapses, the slower the transmitter release, the smaller the size and rate-of-rise of postsynaptic responses would be expected if postsynaptic neurotransmitter receptors were not saturated. This prediction was tested at hippocampal synapses where postsynaptic AMPA-type glutamate receptors (AMPAR) were not generally saturated. Here, we found that the small miniature excitatory postsynaptic currents (mEPSCs) showed significantly slower rise times than the large mEPSCs when the sucrose-induced mEPSCs recorded in cyclothiazide (CTZ), a blocker for AMPAR desensitization, were sorted by size. The slow rise time of the small mEPSCs might result from slow release through a non-expanding fusion pore, consistent with postfusional control of neurotransmitter release at central synapses.

• 전자공학회논문지C
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• 제35C권5호
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• pp.50-58
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• 1998

We propose an efficient face recognition system for controllinng the access to the restricted zone using both the face region detectors based on facial symmetry and the extended self-organizing maps (ESOM) which have sensory synapses and descriptive synapses. Based on the visual cues of the facial symmetry, we apply horizontal and vertical projections on elliptic regions detected by GHT(generalized hough transform) to identify all the face regions from the complex background.And we propose an ESOM which can exploit principal components and imitate an elastic similarity matching, to authenticate faces of the enlisted member. In order to cope with changes of facial experession or glasses wearing, etc, the facial descriptions of each member at the time of authentication are simultaneously updated on the discriptive synapses online using the incremental learning of the proposed ESOM. Experimental results prove the feasibility of our approach.