Well-refined wiring of neural circuits is fundamental to proper brain function. Aberrantly formed neural circuits may induce epileptiform discharges of neurons. Therefore, elucidating the cellular and molecular mechanisms that underlie the development of aberrant neural circuitry will advance the understanding and prevention of epilepsy. The dentate gyrus has been suggested to serve as a gate that prevents the propagation of epileptiform activity from the entorhinal cortex to the hippocampus. Within the dentate gyrus is the dentate granule cell layer, which consists of densely packed granule cells that maintain intrinsically low-firing properties and rarely exhibit burst discharges synchronized with other neurons. Additionally, granule cells form abundant synaptic inputs to inhibitory interneurons in the dentate hilus, a fraction of which provide feedback inhibition back to the granule cells. Network reorganization of the dentate gyrus in patients with temporal lobe epilepsy and in corresponding animal models was reported. Specifically, mossy fiber sprouting and the emergence of ectopic granule cells contribute to the observed phenotypes. This paper reviews the expanding literature on the cellular and molecular mechanisms underlying the formation of aberrant hippocampal networks and their role in epileptogenesis.

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1. 小脳皮質の最外層に存在する星状細胞は, 深い切れこみをもつ核と, 細胞体表面上のシナプスの稀少なことによって, 比較的容易に同定される. 細胞質内に極めて特異な層状構造をもつことも, この細胞の特長としてあげることができる. 星状細胞の神経終末はF-型シナプスを形成する.
2. はプルキンエ細胞層の上に位置し, 細胞の大きさは星状細胞より大きい. この細胞の特長は 細胞体表面に多数のS-型, F-型シナプスをもつこと, 核にいちじるしい切れこみの多数見られることである. の神経終末はプルキンエ細胞の細胞体表面に籠状に多数のF-型 シナプスを形成する. なお一部の神経線維は上行して小脳皮質分子層内にF-型 シナプスを形成する. の細胞体表面に単一線毛の見られることがある.
3. ゴルジ細胞はプルキンエ細胞層の内側に顆粒細胞に混在して存在する. 核はより はなはだしい切れ込みを豊富にもっている. 細胞体表面のシナプスの数はに比していちじるしく少い. 時に細胞体上に shortnecked spine がみられる. ゴルジ細胞の神経終末は顆粒細胞の樹状突起との間にF-型 シナプスを形成する.
4. 顆粒細胞は小脳皮質の もっとも厚い層を形成し, 核は大きく, 細胞層は比較的少いのが特長である. 細胞体表面にはシナプスは形成されず, もっぱら樹状突起の上に ゴルジ細胞の神経終末および苔線維の神経終末をうけ, いわゆる小脳糸球体を形成する. ときに細胞体をとりまく髄鞘構造のみられることがある.

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近年, 難治性てんかんや精神遅滞などの脳病変として皮質形成障害が重視されるようになった.皮質形成障害は一括してニューロン移動障害 (NMD) とも呼ばれている.しかし, 胎生期の様々な侵襲や遺伝子異常による多様な皮質形成障害の発生病理をNMDだけで説明することは不可能である.これまでの神経発生生物学的研究や実験病理学的研究では, ニューロン生成障害, radial glial fiberを含めたニューロン・グリアおよびニューロン・ニューロン接合の障害, 不均衡な可塑的シナプス形成などが皮質形成障害の成立に関与していることが明らかにされている.ここでは, 皮質形成障害の発生病理の研究の現状と多様性を, 主として実験病理学的観点から紹介した.

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Since the last century, histological studies on human tracheal glands have been carried out not infrequently, but nevertheless the cytological details and their changes accompanying the secretory function still remain in perfect obscurity. The author obtained in operations healthy tracheal mucosae from 25 cases, and performed histological and cytological observations on the tracheal glands. The samples were fixed in LEVI's and CHAMPY's fluids, ZENKER-formol, 10% formol and formol-alcohol, embedded in paraffin, and serially sectioned 3-4μ thick. For staining, hematoxylin (HANSEN)-eosin, HEIDENHAIN's iron-hematoxylin, azan, periodic acid-SCHIFF (PAS) reaction and BAUER's reaction were employed. The GOLGI apparatus was visualized by KOLATCHEV's osmic acid method, and sometimes further stained with KULL's method. The results are summarized as follows:
1. The human tracheal gland is mainly found in submucosa, and extends in different ways in the cartilaginous region, intercartilaginous region and paries membranaceus, In the cartilaginous region, it spreads parallel to the surface, and in the intercartilaginous region and paries membranaceus, it spreads in most cases into the deep layers perpendicular or oblique to the surface. In this way, the shape and the location of the gland is dependent on the presence of the tracheal cartilage.
2. The gland opens in the bottom of the tubular or funnel-shaped crypt of the tracheal mucosa, lined by the same pseudostratified columnar ciliated epithelium like the surface of the mucosa. The crypts sometimes show at the bottom simple branching.
3. All the tracheal glands are provided excretory ducts with wide lumina, lined by a simple columnar epithelium consisting of a single layer of high columnar epithelial cells and a layer of basal cells in its base. Sometimes the excretory duct shows a simple branching. The striated portions, as found in the ducts of the large salivary glands, are not visible.
4. Secretory portion directly continuous with the excretory duct is a large mucous glandular tubule which ramifys several times into small mucous branches. In the mucous tubule and its branches open many tubular and alveolar albuminous (serous) secretory portions (terminal portions), which consist of albuminous glandular cells and also ramify. The human tracheal glands are therefore neither pure mucous nor pure serous (or albuminous) glands, but are always mixed glands, and from morphological standpoint they should be called simple and sometimes compound branched tubuloalveolar glands.
5. Concerning the distribution of both mucous and albuminous cells in the branched glandular tree there exists a definite rule: the former being situated near the excretory duct occupying the proximal portion, and the latter being distributed in the more distal part making the terminal portions of the tree. The branched mucous tubule consequently not only secretes mucous secretion but also serves as a part of the excretory duct. Numerous demilunes, consisting of albuminous cells, are found in the wall of the branched mucous tubule.
6. The tracheal gland has many demilunes of variable shapes and sizes, and in some occasions several demilunes are grouped at the end of the mucous tubule. Larger demilunes of alveolar form protrude often from the mucous tubule wall into the interstitial connective tissue, including deep lumina. These findings suggest the transition of demilunes into albuminous tubules or acini. Demilunes are considered to be poorly developed albuminous tubule or acini and present the same cytological changes in secretory function.
7. Between the basal surface of the glandular cells (mucous and albuminous) and the membrana propria of the glandular tubules, there are many myoepithelial cells, which are of smooth muscle fiber type and arranged in parallel with the long axis of the glandular tubule.

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Sprague-Dawley white rats were used for this study. New-born male rats were each radiothyroidectomized by intraperitoneal injection of 100μCi of¹³¹I. The animals were perfused on days 7,15,20,34 and 96 with paraformaldehyde-glutaraldehyde mixture. Cerebellums were removed and chopped sagittally on the midline. The tissues, from cerebellar cortex in the pyramis, embedded in low viscosity epoxy resin. Before thinsectioning, tissue was trimed in the molecular layer. Tissue was ultra-thinsectioned on the ultramicrotome, stained with ulanyl acetate and lead nitrate, and viewed with electron microscope. On the other hand, cerebellum embedded in paraffin, was thinsectioned on the microtome, stained with Hematoxylin-Eosin, Kluver-Barrera and Bodian stain, and observed with light microscope. On light microscopic view, external granular layer remained at 20 days in hypothyroidal animals. But, in normal control rats on the same day, external granular layer already disappeared. The width of the molecular layer of the cerbellar cortex in the pyramis was measured; at 15 days, the data in control was significantly larger than in hypothroid rats, at the other days, not significant in the comparison between hypothyroid rats and normal control. On electron microscopic observation, there was no abnormal structure and no qualitative change in the molecular layer of the cerebellar cortex in both groups. But there was quantitative difference between them. Number of synaptogenesis between parallel fiber and Purkinjedendritic spine in hypothyroid rats was less than in normal control. Morphometric study was tried with computerized digitizer on the electron microscopic photograph in the molecular layer at 35560 magnification, as follows;
(1) Counts of synaptic profiles p er unit area.
(2) Length of post-synaptic thickening.
(3) Area of Purkinje-dendritic spine. Samples for these morphometric items were selected from outer and inner halves of the molecular layer in cerebellum.10 samples were taken from each zone. These were measured from the magnified positives, printed on the quarters at 35560 magnification. Gray type I synapses between parallel fiber terminals and Purkinje-dendritic spines were selected and measured for these three items on each photographs. Several statistical comparison between hypothyroid and control groups were made. As the result, there were many significant differences in the counts of synaptic profiles. For length of post-synaptic thickening and area of Purkinje-dendritic spine, there were some significant differences in comparison between each days, and between inner half and outer half within each groups. On these statistical significant differences, developmental disturbance of the cerebellar cortex in the neonatal hypothyroid rats was clarified.

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Studies have been made of a neurovegetative termination within the large salivary gland in cats and men, using SUZUKI's silver method after 10 days' fixation in a 20% neutral formalin. The results of the observation are summarized as follows:
1. Nerve plexuses with numerous ganglion-cells were found either on the surface or the interior of the gland. They are found accompanied by the ducts of the gland and blood-vessels. By the difference of the affinity for silver-salts, the ganglion-cells on these nerve-plexuses can be classified into two groups, i. e. the argyrophil and argyrophobic cells. In comparison with other nerve-plexuses in the alimentary tract, these plexuses seem to have much similarities to those of MEISSNER in the submucous tissue.
2. a) The nerve-plexuses of the parotid gland are found spreading on the surface of the gland, as reported by many other investigators, they seldom extend to the inside of the gland.
b) Of the submandibular gland, however, they penetrated into the connective tissues of the interlobar or interlobular space.
c) Nerve-plexuses are few in the interlobar space of the sublingual gland, and are rarely found in the interlobular space.
d) Lingual glands, especially serous glands, have a small number of nerve plexuses in their interlobar space or in the surrounding connective tissues.
As a rule, the nerve fibers branching out of the nerve-plexuses become mostly unmyelinated and continue branching and anastomosing to form a terminal reticulum in- and outside the basement membrane of the related acinus.
3. In the serous acinus of the salivary gland there generally exist two kinds of nerve fiber. One has a uniform thickness and smooth surface, and winds its way through one acinus to another without being influenced by the basement membrane of the acinus and arrangment of the gland-cells. The other is a hardly stainable fiber, which has many windings and branches making many anastomoses with those from the neighboring acini to form complicated nets inside the acini. Sometimes its ends show a simple form of nerve-ending.
4. In the mucous part generally there exists also a type of nerve fiber as in the serous acinus. The branches of that fiber pass through intercellular spaces into the lumen and end on the free surface of the gland-cells, showing a rosarylike ending, or a delicate net together with fibers of the same kind.
5. Interstitial cells of RAMON y CAJAL are often found among the mucous cells of the salivary gland. Neurofibrils, with which the cytoplasm of these cells is filled, spread out of the cytoplasm to form a thin periterminal reticulum around the mucous cell, particularly around the middle zone.
6. The striated duct of the submandibular gland in a cat has a specific form of nerve-ending, i. e. thin nerve fibers make their way through the cytoplasm and the basal zone between the nucleus and basement membrane. These nerve fibers have many branches and show some dilatation, like small varices or dots, towards their ends. These fibers penetrate into the ducts in the following three ways: they come directly from the terminal reticulum outside the tube, or through the cytoplasm of the myoepithelium, or through the interstitial cells of RAMON y CAJAL.
The parotid gland has in its striated ducts an another kind of nerve fiber which branches at the point of the entrance to the cell through the basement membrane and seems to innervate some adjacent cylinderic epithelial cells.
7. In the interstitial connective tissue of the anterior lingual gland, especially near the main duct in the center of the gland, there occured a capsulated nerve ending which is very similar to the end bulb of KRAUSE in structure.

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