大鼠脑缺血后突触体素与突触密度的关系

目的：观察脑缺血后，大脑顶叶皮质突触体素的表达与突触密度的关系，为脑缺血后监测突触密度的变化提供了一个间接方法。方法：采用大鼠脑缺血模型，用免疫组化及电镜方法。结果：脑缺血后，随缺血时间的延长，突触体素的表达逐渐减少；神经毡内突触数目逐渐减少。结论：脑缺血后，随缺血时间延长，突触体素表达减少，神经毡内突触数目逐渐减少，二者之间呈正相关，说明突触体素可作为监测突触密度的间接指标。     

帕金森病患者丘脑腹外侧核超微结构观察

利用透射电镜对１６例帕金森病患者丘脑腹外侧核活检组织进行了超微结构观察，结果发现：神经细胞数量减少，胞体变小，核呈浓缩变形，线粒体肿胀变性，嵴突短小或消失。突触末梢水肿，扩大呈空泡样，突触小泡数量减少或消失。星形胶质细胞水肿，膜性细胞器破坏。毛细血管内皮细胞肿胀，管腔狭窄，线粒体肿胀变性。病变随患者病情加重而变化明显。结果提示丘脑腹外侧核超微结构上的改变有可能成为临床判断病变程度的辅助诊断指标。     

红景天苷对局灶性脑缺血再灌注大鼠突触超微结构的影响

目的研究红景天苷对局灶性脑缺血/再灌注损伤后突触结构和数密度的变化。方法采用线栓法制造大鼠大脑局灶缺血(2h)/再灌注模型(I/R模型),于灌注后1d、3d、7d、14d时间点断头取脑,电镜观察突触结构和数密度的变化。结果I/R模型组数目减少,7d降至最低,14d突触数目回升;突触结构随再灌注时间延长损伤加重,14d有所恢复;红景天组突触损害程度减轻,突触数目增加(P<0.05),突触数密度恢复的时间提早至7d。结论红景天苷可以减轻脑缺血再灌注后突触的损伤,易化突触可塑性。     

帕金森病大鼠模型额叶皮质的代谢及形态改变

目的：探讨帕金森病中大脑额叶皮质的形态及代谢改变。方法：大鼠实验组于6-OHDA毁损后用BIOSPEC47／30磁共振波谱仪(4．7T)，采用点分辨波谱法对双侧额叶皮质行H-MRS检测，分析该区N-乙酰天门冬氨酸／肌酸(NAA／Cr)和胆碱／肌酸(Cho／Cr)比值的变化，并用电镜观察该区神经元及突触的形态变化。结果：实验组大鼠损毁侧额叶皮质．NA．A／Cr比值显著低于对侧，对照组两侧无显著差别；Cho／Cr比值在两组的两侧相比均无显著差别。电镜观察显示：损毁侧额叶皮质的突触数量较对侧减少，突触前、后膜和突触小泡结构异常，典型突触结构消失，树突棘出现大片低电子密度区，细胞器消失。结论：帕金森病大鼠模型损毁侧额叶皮质内存在神经元缺失或突触数量的减少，突触结构异常及功能异常。     

血管性痴呆大鼠海马synapsinⅠ及其磷酸化水平的动态变化

目的：观察血管性痴呆大鼠海马区突触结构和突触蛋白synapsin I及其磷酸化水平的变化，探讨血管性痴呆大鼠突触传递障碍的可能机制。方法: 采用双侧颈总动脉夹闭再灌注同时腹腔注射硝普纳建立血管性痴呆模型，在15 d、1月、2月和4月等时点，电镜观察大鼠海马CA1区突触结构的病理改变，应用免疫组织化学染色法测定血管性痴呆大鼠海马synapsinⅠ及其磷酸化水平的变化。结果: 假手术组大鼠海马CA1区未见明显病理改变，突触前小泡聚集成簇，模型组突触前后膜界限不清，突触后致密物减少，突触前囊泡分布分散、聚集囊泡簇减少，并随造模时间的延长，病理改变加重；模型组大鼠海马CA1区synapsin I阳性产物表达明显减少(P<0.01)，DG区分子层无明显变化(P>0.05)；模型组大鼠海马磷酸化synapsin I（p-synapsin I）阳性细胞明显减少(P<0.01,P<0.05)，15 d和1月时点大鼠海马DG区和CA1区p-synapsin I阳性细胞表达较假手术组增强(P<0.01)，2月和4月时点CA1区p-synapsin I阳性细胞表达较假手术组减弱(P<0.01)，而DG区无明显变化(P>0.05)。结论: VD模型大鼠海马突触结构受损，突触小泡簇减少；synapsinⅠ及其磷酸化水平表达降低，突触传递前机制受损可能是VD突触传递障碍的机制之一。     

利多卡因的脑保护机制

利多卡因具有脑保护作用，其机制与下列因素有关：阻断膜Na+-K+交换,ATP的消耗减少,因而减少自由基的产生,同时抑制缺血脑细胞Ｋ+外流及游离脂肪酸释放；抑制膜上电压依赖性Ca2+通道，减轻H2O2诱导的脂质过氧化反应；有效减轻缺血再灌注时神经细胞离子的紊乱,阻止细胞内Na+浓度的升高,降低突触前的谷氨酸释放；抑制线粒体的有氧代谢,降低线粒体内能量物质代谢速率,趋缓乳酸水平的升高,从而减轻细胞内乳酸的堆积,提高细胞对缺氧的耐受力；抑制缺血脑灌注后脑型肌酸激酶的释放,从而使脑缺血时的神经膜保持稳定；改善细胞渗透压和ATP的利用及Ca2+的清除等,从而起到保护神经的作用。     

成年斑马鱼视神经再生期间顶盖表面纤维层和灰质层的突触形态学研究

目的研究斑马鱼视神经再生过程中神经递质的变化，探讨神经递质和神经再生的关系。方法应用斑马鱼视神经再生模型，通过电镜技术观察顶盖表面纤维和灰质层突触的形态变化。结果视神经损伤后顶盖突触变化过程大致可分4个时期：1．视神经损伤后早期顶盖突触结构的退变；突触密度和突触小泡密度均下降，空型终末密度增大，8d时突触小泡密度降到最低水平；而空型终末密度最高。2．损伤后14d再生纤维大量进入顶盖；这一时期大核小泡和小核小泡密度都大量增加，但进入顶盖的纤维还没有或很少形成突触，14d时突触密度降到最低。3．损伤后2ld的特征是突触大量形成和圆形清亮小泡、扁平清亮小泡密度增加。4．再生晚期突触形态和功能恢复及精确化；100d时突触密度和突触小泡密度都大体恢复正常，但大核小泡密度还很高。结论兴奋性神经递质和抑制性神经递质可能对早期神经再生的启动和突触的形成起重要作用，而肽类和胺类可能对再生轴突的投射和精确化有重要作用；神经递质促进神经再生有先后顺序。     

米酵菌酸中毒小鼠顶叶皮质超微结构观察

目的观察米酵菌酸对小鼠顶叶皮质毒性作用的超微结构改变,探讨米酵菌酸的中毒作用机理。方法小鼠腹腔注射米酵菌酸,2h后取其大脑皮质,常规透射电镜样品制备,电镜观察其组织的超微结构。结果米酵菌酸主要损伤皮质神经元、胶质细胞和毛细血管内皮细胞的线粒体、粗面内质网及突触等结构。可见线粒体肿胀,嵴断裂或消失,部分线粒体髓样变和空泡变性;粗面内质网数量减少;核周间隙局部增宽;血脑屏障毛细血管周间隙扩张,呈空亮的囊泡样结构,内皮细胞微绒毛减少;突触小泡减少。结论米酵菌酸可造成脑组织亚细胞结构的损伤,为米酵菌酸中毒引起的神经中毒机理提供形态学依据。     

吗啡对大鼠心理依赖相关脑区超微结构和突触数量的影响

目的：观察不同时程吗啡依赖大鼠心理依赖相关脑区超微结构和突触数量的变化。方法：建立不同时程吗啡依赖大鼠模型，应用透射电镜对相关脑区皮质超微结构和突触进行观察计数。结果：吗啡依赖大鼠海马、杏仁核、豆状核和额叶皮质神经细胞线粒体肿胀、畸形，内质网扩张，多聚核糖体解聚，轴突、树突及突触数量增多；吗啡依赖4周组大鼠突触数量的增多与其他短时期或对照组大鼠相比，具有显著性差异；而8周组则具有高度显著性差异。结论：吗啡依赖大鼠心理依赖相关脑区神经细胞呈缺血缺氧性及退行性改变；突触数量增多，并随吗啡依赖时限的延长而更加明显。     

人胎海马发育的研究 Ⅱ、电镜观察

在电镜下观察了4-10个月人胎儿海马CA_2亚区多形细胞层突触复合体的发育。结果,4个月胎儿即见到含少量、分散的圆形无芯小泡的对称型轴-树突触。数量不多但结构非常典型。突触前成分内还可见到结构不发达的线粒体。此时,在数量上占优势的突触前身结构构成突触样接触,即膜的相接近部分发生特化的增厚,间隙清楚可辨,但无突触小泡。随着胎龄的增大,出现下述一系列变化:(1) 突触前身结构的数量优势逐渐被典型突触所代替;(2) Ⅰ型突触出现,并逐渐增多;(3) 突触形式由低胎龄时的简单突触逐渐出现并联突触和突触群;(4) 突触小泡数量增加,并向突触前膜靠拢,在10个月材料还见到扁平小泡和圆形小泡共存;(5) 线粒体的数量和结构也日趋增多和典型。基于上述发现,作者认为(1)人胎海马CA_2亚区内突触的个体发育经历了突触前身结构和典型突触两个连续过程;(2) 该部的突触具有简单突触、并联突触和突触群等多种形式;(3) 参与海马活动的神经递质至少应具有兴奋和抑制两类。     

Ultrastructure of cortical synapses after failure of presynaptic activity in ischemia,

The fine structure of cerebral cortical synapses was investigated during failure of synaptic transmission produced by ischemia. Presynaptic and postsynaptic potentials evoked in the anterior sigmoid gyrus of the cat by stimulation of the nucleus ventralis lateralis and the DC potential between cortical layer IV and the white matter were recorded with micropipettes during cerebral ischemia produced by arterial hemorrhage in paralyzed, artificially ventilated animals. After failure of the spontaneous electrocorticogram and postsynaptic responses, the presynaptic volley failed with development of depolarization of intracortical fiber terminals and loss of axon terminal excitability. The gyrus was then biopsied and fixed in collidine-buffered OsO₄. An altered pattern of distribution of synaptic vesicles was observed after presynaptic afferent fiber terminal activity was abolished by 3.5 to 4.0 minutes of cerebral ischemia. Clumping of vesicles in a region away from the cynaptic cleft was seen in about 10% of synaptic endings, and there was more than a two-fold increase in the number of presynaptic profiles devoid of vesicles in ischemic cortex.     

Comparative Ultrastructural Analysis of Mitochondria in the CA1 and CA3 Hippocampal Pyramidal Cells Following Global Ischemia in Mongolian Gerbils

Post‐ischemic injury of the hippocampus unrolls at different levels and has both functional and structural implications. The deficiency in neuron energy metabolism is an initiating factor. We performed transmission electron microscopic (TEM) comparative analysis of mitochondria in excitatory spine synapses in CA1 stratum radiatum and CA3 hippocampal areas after 5 min of global cerebral ischemia in Mongolian gerbils, 4 and 7 days after reperfusion. Electron microscopy and unbiased morphometric methods were used to evaluate synaptic plasticity, and the number and size of mitochondria in synaptic terminals. We compared the morphological organization of mitochondria in presynaptic terminals between CA1 and CA3 areas in control and post‐ischemic condition according to the following morphometric parameters: mitochondrial volume fraction, mitochondrial frequency in CA1 and CA3 terminals, mean number of mitochondria per presynaptic terminal, frequency of damaged mitochondria in terminals, and density of presynaptic terminals. Our ultrastructural study revealed statistically significant differences in morphometric parameters between CA1 and CA3 areas in control conditions, as well as in post‐ischemic conditions. Also, we found temporal differences in measured parameters obtained 4 and 7 days after reperfusion. This study showed significant morphological differences in the organization of mitochondria in excitatory spine synapses between CA1 and CA3 areas, which corresponded with already known differences in functionality and sensitivity to the ischemic insult. Our conclusion is that revealed post‐ischemic changes in mitochondrial distribution in presynaptic CA1 and CA3 terminals could be an indicator of hippocampal metabolic dysfunction and synaptic plasticity. Anat Rec,, 2011. © 2011 Wiley‐Liss, Inc.     

Membrane structure of parallel-fibre synaptic terminals in the cerebellum of the jaundiced Gunn rat: freeze-fracture and E-PTA study

Summary Parallel-fibre synaptic membranes were examined by freeze-fracture and ethanolic-phosphotungstic acid methods in the cerebellum of homozygous (j/j) Gunn rats with hereditary jaundice. Parallel-fibre synapses with dendritic spines of Purkinje cell were severely affected since many Purkinje cells degenerated during the early postnatal period. Some parallel-fibre synaptic terminals lacked their postsynaptic partners and faced astrocytic processes from 18 days of age to the adult stage. These parallel-fibre terminals contained clusters of synaptic vesicles adjacent to synaptic membranes, and synaptic membranes and synaptic cleft materials were identical to those of parallel fibres with postsynaptic partners, as visualized by conventional electron microscopy with osmium tetroxide postfixation and staining of sections with uranyl acetate and lead citrate. In freeze-fractured specimens, the presynaptic membrane of parallel fibres had diffusely distributed large particles and tiny pits on the P-face and protuberances on the E-face, together representing synaptic vesicle attachment sites. Such vesicle attachment sites were present on the presynaptic membranes of parallel fibres without postsynaptic partners from day 18 to the adult stage. After ethanolic-phosphotungstic acid staining, parallel-fibre terminals displayed presynaptic dense projections, intercleft materials and postsynaptic thickening, but some parallel fibres lacked postsynaptic thickening. These observations suggest that the presynaptic membrane structure of the parallel fibre is preserved, even in the absence of a postsynaptic partner, in j/j cerebella. A mechanism for persistence of presynaptic membrane structures without postsynaptic partners in j/j cerebella is discussed.     

葛根素对脑缺血再灌注大鼠神经功能与大脑皮质突触形态结构及参数的影响

目的:观察缺血再灌注(IR)大脑皮质突触形态结构及参数的变化,探讨葛根素(Pue)干预的神经保护作用。方法:将69只SD大鼠随机分为假手术组(sham组)、模型组(IR组)、Pue组和尼莫地平(NIM)阳性对照组(NIM组),sham组15只,后3组每组18只。采用线栓法制作局灶性大脑中动脉IR模型,缺血2 h再灌注24 h后,Pue组和NIM组分别注射Pue 8 mg·kg~(-1)·d~(-1)和NIM 1 mg·kg~(-1)·d~(-1),sham组和IR组给予等体积生理盐水。于用药后3、7和14 d进行改良神经功能缺损评分,而后取缺血侧大脑皮质,电镜观察突触超微结构变化,测量分析突触界面曲率、突触间隙宽度、突触后致密物厚度等参数。结果:与IR组相比,相应时点Pue组和NIM组神经功能缺损评分均降低(P0.05),这2组的差异无统计学意义。电镜下观察IR组突触前后膜和突触间隙模糊,突触前成分内突触囊泡减少,突触后致密带密度降低;Pue组和NIM组较IR组突触密集,凹形突触增加,常见2个活性点,突触后致密物增厚,间隙清晰,患侧皮质半暗带突触界面曲率增加,突触后致密物增厚,突触间隙减小(P0.05);7 d组和14 d组的突触各形态结构参数均优于3 d组(P0.05),两者之间的差异无统计学显著性。结论:Pue有可能通过修复突触结构,促进脑IR大鼠神经功能恢复。     

GABAergic neurons in the mouse superficial dorsal horn with special emphasis on their relation to primary afferent central terminals

Immunocytochemical studies were carried out on the morphological relation between primary afferent central terminals (C-terminals) and GABAergic neurons in the mouse superficial dorsal horn. The superficial dorsal horn is composed of many synaptic glomeruli comprising two types: Type I with centrally located CI-terminals surrounded by several dendrites and few axonal endings, and Type II with centrally located CII-terminals surrounded by several dendrites and a few axonal endings. The CI-terminals are sinuous or scalloped with densely packed agranular synaptic vesicles, a few granular synaptic vesicles and mitochondria, and show an electron dense axoplasm, whereas the CII-terminals are large and round or rectangular with evenly distributed agranular synaptic vesicles, a number of granular synaptic vesicles and mitochondria, and show an electron opaque axoplasm. The immunoreaction of GABA was remarkable in the superficial laminae of the dorsal horn. Many interneuronal somata in the substantia gelatinosa showed GABAergic immunoreactivity. The immunoreaction was seen in the entire GABAergic neuroplasm, but not in the nucleus and its envelope. Most GABAergic features appeared as dendrites making postsynaptic contact with CI- or CII-terminals; i.e., numerous C-terminals made presynaptic contact with GABAergic dendrites. GABA immunoreactivity was seen over round synaptic vesicles and mitochondrial membranes. A few CII-terminals made presynaptic contact with GABAergic interneuronal somata. Previous physiological and anatomical studies have suggested that not only the cutaneous nociceptive primary afferent C-terminals but also mechanoreceptive primary afferent C-terminals make presynaptic contact with the GABAergic dendrites, boutons and soma. The presynaptic relation of these primary afferents with GABAergic neurons seems to provide morphological support for the essential feature of the gate control theory: primary afferent fibers may play a part in the modulation of nociceptive information via GABAergic neurons in the superficial dorsal horn. Small GABAergic terminals were found to make contact with blood capillaries suggesting the release of GABA into circulation.     

GABAergic and pallidal terminals in the thalamic reticular nucleus of squirrel monkeys

The ultrastructure of synaptic terminals from the external segment of the globus pallidus and of other synaptic terminals positive for gamma-aminobutyric acid (GABA) was examined in the thalamic reticular nucleus (TRN) of squirrel monkeys. Two GABA-positive terminals types were commonly encountered within the TRN neuropil. The most common type of GABAergic terminals (F terminals) are filled with dispersed pleomorphic synaptic vesicles and clusters of mitochondria. These terminals establish multiple symmetric synapses upon the somata and dendrites of TRN neurons. The external pallidal terminals, labeled with WGA-HRP, arise from thinly myelinated axons and correspond to the medium to large F terminals. A less prevalent population of smaller GABAergic synaptic profiles was also identified. The synaptic profiles in this second group contain considerably fewer pleomorphic synaptic vesicles in small irregular clusters and fewer mitochondria, establish symmetric synapses, are postsynaptic to other axonal terminals, are presynaptic to dendrites and soma, and are unlabeled following pallidal injections of WGA-HRP.     

Synaptic organization of the dorsal lateral geniculate nucleus in the adult hamster

Summary The synaptic organization of the sector of the dorsal lateral geniculate nucleus has been examined by electron microscopy in normal adult hamsters and in adult hamsters subjected to unilateral eye enucleation or intravitreal injection of horseradish peroxidase.Two types of neuropil are apparent. Islands of complex neuropil partially enclosed by astrocyte processes (synaptic glomeruli) are surrounded by a sea of simpler non-glomerular neuropil. The latter is dominated by small axon terminals with spherical synaptic vesicles and Gray type 1 axodendritic contacts (SR-boutons) and also contains axon terminals with flattened synaptic vesicles (F-boutons). The glomerular neuropil contains (i) exclusively postsynaptic dendrites and dendritic protrusions of presumptive projection cells; (ii) pre- and postsynaptic pleomorphic-vesiclecontaining P-boutons (interpreted as appendages of the dendrites of interneurons); (iii) large axon terminals containing spherical synaptic vesicles and large pale mitochondria (R-boutons) which were experimentally identified as retinal terminals and which are presynaptic to both projection cell dendrites and P-boutons at Gray type 1 contacts; (iv) F-boutons (minority component). F-boutons and P-boutons are presynaptic to both projection cell dendrites and P-boutons and P-boutons are the intermediate elements of various serial synapses including triplet (triadic) synapses. Medium-large terminals with spherical synatpic vesicles and dark mitochondria (RLD-boutons) which were commonly invaginated by dendritic spines of projection cells in small glomerulus-like formations were also identified. The origin of RLD-boutons is unknown but SR-boutons probably derive chiefly from ipsilateral visual cortex and possibly also from superior colliculus, and non-glomerular F-boutons probably originate in the ipsilateral thalamic reticular nucleus.No differences in synaptic organization were found between the part of the nucleus which receives uncrossed retinal input and the part which receives crossed input, nor were differences seen in the size, fine structure or relationships between the terminals of identified crossed and uncrossed retinal axons.     

Ultrastructure of Hippocampal Field CA1 in Rats after Status Epilepticus Induced by Systemic Administration of Kainic Acid

The ultrastructure of hippocampal field CA1 in rats was studied 14 days after status epilepticus induced by administration of kainic acid. Structural changes were seen in 40% of cells, predominantly interneurons, which showed both reversible changes (mitochondria with an electron-dense matrix or small numbers of short cristae, moderate dilation of rough endoplasmic reticulum (RER) cisterns, and small numbers of ribosomes) and more significant abnormalities: swollen mitochondria with very small numbers of cristae, which were partially degraded, some with damaged mitochondrial membranes, along with pathologically damaged RER components and focal or peripheral chromatolysis. Chromatolyzed areas sometimes contained membrane-like includes and vacuoles. In addition, the neuropil contained occasional large osmiophilic formations surrounded by astrocyte processes with accumulations of glycogen or gliofibrils. Synaptoarchitectonics were also altered. Asymmetrical synapses were often seen on small dendrites and spines, with highly osmiophilic postsynaptic zones, their synaptic terminals containing numerous synaptic vesicles and large vesicles with electron-dense cores. Some presynaptic endings showed clear signs of classical dark-type degeneration. As the nucleus remained intact in all types of altered neurons, it appears that most cells underwent pathological changes of the necrotic type.