神经垂体内儿茶酚胺能神经与肽能神经相互关系的电镜研究

为了探明神经垂体内神经激素释放的调节机制,本文采用免疫组织化学和化学损毁相结合的方法,在电镜水平分别显示神经垂体内的后叶加压素(VP)能神经和儿茶酚胺(CA)能神经,观察它们的分布和相互关系。结果发现:大鼠神经垂体内不仅有广泛的VP神经终末分布,而且存在着因6-OHDA损毁所致溃变的CA能神经终末。CA能神经终末与垂体细胞和小胶质细胞之间存在着密切关系,甚至可建立突触样连接。CA能终扣与VP能终扣可建立轴-轴突触。在这种情况下,含CA的神经终末为突触前成分,含VP的神经终末为突触后成分。上述结果为神经垂体内神经激素释放的调节机制首次提供了超微结构证据。     

大鼠神经垂体内后叶加压素神经分泌末梢的GABA能神经支配的免疫电镜证实

为了探讨神经垂体内后叶加压素（ＶＰ）释放的γ－氨基丁酸（ＧＡＢＡ）能神经调控，本研究用包埋前ＡＢＣ法结合免疫电镜双标技术，研究了大鼠神经垂体内ＶＰ能神经和ＧＡＢＡ能神经的超微结构分布及其相互联系。先用ＤＡＢ法显示ＧＡＢＡ免疫反应，然后用钼酸铵－ＴＭＢ法显示ＶＰ免疫反应，再用ＤＡＢ－氯化钴稳定后作免疫电镜包埋。电镜观察发现：在神经垂体内ＧＡＢＡ样免疫反应产物呈电子密度高的颗粒状沉淀，定位于神经末梢内的小清亮羹泡周围和线粒体膜上；ＶＰ样免疫反应产物呈电子密度高的不规则形块状或针状散在于神经分泌末梢内。ＧＡＢＡ样神经末梢分布于神经分泌末梢之间或紧贴毛细血管和垂体细胞，可与神经分泌末梢紧密接触甚至形成突触。ＶＰ样神经分泌末梢内含小透亮囊泡和大颗粒囊泡，并可与ＧＡＢＡ样轴突末梢形成突触。在这种情况下，ＧＡＢＡ样轴突为突触前成分，突触前、后膜呈对称性，突触间隙宽度小于２０ｎｍ，内含电子致密物质。以上结果证实，在大鼠神经垂体内ＶＰ释放受到ＧＡＢＡ神经的直接突触调控。     

神经垂体内5-羟色胺的免疫电镜研究

本文用免疫电镜方法研究了大鼠神经垂体内5-HT的超微结构分布。结果表明:神经垂体内的5-HT免疫反应产物定位于神经末梢的大颗粒囊泡内、小透亮囊泡表面和线粒体外膜。有时,垂体细胞胞浆也呈5-HT免疫反应阳性。5-HT免疫反应阳性的神经末梢分布于毛细血管周围和垂体细胞附迈。本文首次报道含5-HT的神经末梢可与非5-HT神经末梢形成对称性轴-轴突触。其中,5-HT末梢为突触前成分。本文结果提示:神经垂体内的5-HT不仅可通过非突触方式而且可通过突触方式释放,参与神经内分泌功能的调节。     

大鼠中缝大核内5-羟色胺样P物质样和亮氨酸脑啡肽样突触结构的免疫电镜观察

用免疫电镜法在大鼠中缝大核内观察到:(1) 5-羟色胺(5-HT)样阳性轴突终末与阴性胞体、阳性和阴性树突以及阴性轴突终末,分别形成轴-体突触、轴-树突触和轴-轴突触;阴性轴突终末与阳性胞体和阳性树突分别形成轴-体和轴-树突触;(2) P物质样(SP样)和亮氨酸脑啡肽(L-Enk)样阳性轴突终末与阳性和阴性的胞体和树突,以及阴性轴突终末与阳性胞体和树突分别形成轴-体突触和轴-树突触,L-Enk样阳性轴突终末之间形成轴-轴突触;(3) 上述5-HT、SP和L-Enk样结构所形成的突触中,阴性轴突终末与阳性树突所形成的轴-树突触最多见;(4) 上述阳性轴突终末内主要含透明圆形小泡。免疫反应产物为电子密度高的物质,主要沉积于膜性细胞器的表面、透明圆形小泡和部分颗粒囊泡内和小泡膜上。     

疼痛对垂体细胞作用的电镜观察

垂体细胞(Pituicytes)是神经垂体内一种特殊分化的神经胶质。多分布在神经叶、漏斗柄及正中隆起。它与丘脑下部-垂体束的神经分泌纤维有密切关系。常见垂体细胞的突起包绕小型神经分泌纤维。有时其胞浆内显示吞噬退化的神经末梢。近来发现,垂体细胞可与神经分泌纤维形成突触。Kiernan认为,垂体细胞可释放激动剂,能促进神经分泌纤维的新生及神经分泌粒的成熟。Hansh报道,垂体细胞可合成和分泌γ-氨基丁酸(GABA)。GABA可与神经分泌纤维膜上的受体结合而发挥作用。GABA为一种抑制性神经递质,可     

三叉神经脊束核内SP神经的单胺神经支配——化学损毁及免疫细胞化学电镜研究

本文应用化学损毁与免疫细胞化学相结合的方法在亚细胞水平研究了SP神经的单胺神经支配。结果证实在大鼠三叉神经脊束核尾侧亚核内广泛存在着因5,7—DHT损毁所致的变性单胺(主要是5-HT)神经纤维和SP样免疫反应的树突和轴突。单胺能神经和SP样神经结构可分别与未标记的结构形成突触联系。而且,在这两种不同化学性质的神经结构之间存在着轴—树和轴—轴突触。在所有这些突触结构中,单胺能神经末梢均为突触前成分,SP终扣则为突触后成分。突触前、后膜大多呈对称性。以上实验结果可以为解释单胺(主要是5-HT)帮SP在三叉神经脊束核尼侧亚核中参与疼痛和镇痛的机制提供超微结构依据。     

家兔心脏房室结区神经终末亚微结构

观察８只家兔心脏病结区神经终末的亚微结构。该区内有丰富的神经末梢;游离神经末,末梢神经束及突触小球（轴－轴突触多联体）。神经末梢彭突与结细胞相贴近形成神经结细胞接点。结细胞膜外有一层基膜,末梢膨突内小泡与轴膜融合,破裂外排,轴膜不完整,轴外有一层深色颗粒带,可能则由小泡外排的递质所成,对心壁内感觉神经及突触小球可能参予构成心脏自律系统外周神经调节环路略加讨论。     

大鼠纹状体边缘区P物质样免疫反应神经终末的超微结构研究

边缘区是用免疫组织化学与束路追踪相结合的方法,在大白鼠纹状体发现的一个新区,其间的P物质、脑啡肽等免疫反应神经终末的数量,比纹状体的其他部分多。本文用包埋前免疫电镜方法,研究了该区的P物质免疫反应神经终末的突触特点。发现4种主要的突触类型,最常见的是轴-树和轴-棘突触,几种由两个以上突触组成的复合型突触群也较常见,偶尔可见轴-轴突触。同时也观察到未标记的轴突终末与P物质样免疫反应树突形成突触。P物质样免疫反应轴突终未形成对称型和非对称型突触。非对称型突触、突触后小型树突以及突触构成的复杂性,证明该区的P物质样免疫反应神经终末的来源可能与纹状体其他部位不同,并且提示该区的功能与纹状体其他部分可能不同。     

孤束核中含生长抑素的神经细胞和神经纤维——免疫电镜研究

本文报道用免疫电镜方法研究大白鼠延髓孤束核联合亚核内含生长抑素(SRIF)的神经细胞及神经末梢。实验结果表明,孤束核内的SRIF样免疫反应阳性胞体为中小型细胞,呈梭形或椭圆形。含SRIF样免疫反应的轴突主要构成轴轴突触,后者为通道突触或终末突触。含SRIF的孤束核神经细胞本身不接受含SRIF的神经纤维支配,但其树突可与未标记的轴突形成轴树突触。     

离体培养鸡胚脑神经细胞的超微结构研究

本文应用扫描电镜和透射电镜,观察离体培养鸡胚脑细胞的超微结构,侧重描述了神经细胞及其突起间突触连接的形态特征。培养4天后,分化发育成为双极和多极的神经细胞及其突起,彼此已连成网络,并出现初期的突触连接,还见有突触前袋样结构和桥粒样细胞连接。培养7天后,神经细胞之间的轴-树、轴-体和轴-轴等类型的突触连接数目增多,透明突触囊泡密集,结构更完善。培养10天和14天后,神经细胞之间的突触连接仍较多,但已出现神经细胞变性,纤维性神经胶质细胞明显增多。     

Microglia in the neurohypophysis associate with and endocytose terminal portions of neurosecretory neurons

The rat neurohypophysis contains a population of microglial cells, the majority of which occupy a pericapillary position in the resting gland. The microglia are immunocytochemically identifiable by the presence of macrophage-associated antigens and resemble microglia of the CNS. Morphometry at light and electron microscopic levels reveals that such cells constitute approximately 19% of the intrinsic cell population, excluding the endothelial cells. Two other populations of neurohypophysial glial cells, parenchymatous pituicytes and fibrous pituicytes, do not express macrophage-associated antigens. The microglia have long processes which surround and, in some cases, engulf apparently viable portions of the magnocellular neurosecretory nerve terminals. A sequence of stages of selective endocytosis and degradation of the engulfed nerve terminals can be visualized within pericapillary microglia. Some phagosomes and secondary lysosomes contain morphologically intact neurosecretory granules; others contain partially destroyed neurosecretory granules or amorphous material all of which are identifiable as originating from the magnocellular neurosecretory terminals by their immunoreactivity for oxytocin- or vasopressin-neurophysin. This finding indicates a novel role for the microglial cells in remodelling terminal aborizations of neurosecretory neurons and in processing or degrading hormones and peptides they contain. Because of their close and selective associations with other cellular elements of the neurohypophysis, any substances produced by microglia also have the potential to influence hormone secretion, pituicyte proliferation and neurohypophysial vasculature.     

Axoglial synaptoid contacts in the neural lobe of the human fetus

Axoglial synaptoid contacts as well as junctional specializations were examined in the neural lobe of five human fetuses ranging from 7.5 to 19 weeks of ovulation age. Because synapselike contacts (SLC), which have both presynaptic and postsynaptic densities, were observed only in the youngest fetus (7.5 weeks), they may be transient structures. Axoglial SLC were also found in older fetuses, but their structural characteristics were different from those found in a 7.5-week fetus in that the cytoplasmic membrane density was found only on the presynaptic side and its extent was decreased. In the youngest fetus observed here (7.5 weeks), puncta adherentia were observed. In the fetuses older than 11 weeks, gap junctions, long adherentia-type junctions with thick filamentous structures, and mixed junctions with both types of contact were found between pituicytes.     

大鼠下丘脑弓状核年龄性变化的电镜观察

电镜观察大鼠下丘脑弓状核超微结构的年龄变化。结果发现:衰老大鼠弓状核的年龄变化主要发生在弓状核中的暗细胞神经元,出现粗面内质网退化变短,排列失序;高尔基氏器缩小;多聚核蛋白体和神经内分泌物质明显减少。特别引人注目的是在部分暗细胞中出现由双层膜缠绕形成的膜性涡旋体结构。此外,在神经毯出现突触结构异常。突触厚度变薄、间断不连续;神经胶质细胞突起增多,并可进一步形成包绕树突、轴突终末、甚至突触的多层膜环绕的髓鞘样结构。上述研究结果提示,下丘脑弓状核超微结构的年龄性变化是导致神经内分泌系统衰老的主要原因之一。     

Immunoreactivity to P2X(6) receptors in the rat hypothalamo-neurohypophysial system: an ultrastructural study with extravidin and colloidal gold-silver labelling

The distribution of the purine receptor P2X(6) subtype was studied in the rat hypothalamo-neurohypophysial system at the electron microscope level. Receptors were visualised with ExtrAvidin peroxidase conjugate and immunogold-silver pre-embedding immunocytochemistry using a polyclonal antibody against an intracellular domain of the receptor. Application of ExtrAvidin labelling revealed P2X(6) receptors in subpopulations of: (i) neurosecretory cell bodies, neurosecretory and non-neurosecretory axons and dendrites of neurones in the paraventricular and supraoptic nuclei; and (ii) pituicytes and neurosecretory axons of the neurohypophysis. Some of the neurosecretory granules observed in the supraoptic and paraventricular nuclei neurone cell bodies, dendrites and axons as well as those in neurohypophysial axons were also positive for the P2X(6) receptors. In the paraventricular nucleus, some axons and dendrites of non-neurosecretory neurones positive for P2X(6) receptors formed synapses between themselves. Using the immunogold-silver method, the electron-dense particles labelling P2X(6) receptors were found in neurosecretory cell bodies of the supraoptic and paraventricular nuclei, in relation to the cytoplasm, endoplasmic reticulum, Golgi complex and neurosecretory granules. The particles indicative of P2X(6) receptors were also located in neurosecretory and non-neurosecretory axons including axonal buttons making synapses with P2X(6)-negative dendrites. In the neurohypophysis, the electron-dense particles were localised in a subpopulation of pituicytes and neurosecretory axons. In neurohypophysial axons, particles were at times seen over the membrane of some neurosecretory granules (immunogold label) or microvesicles (immunoperoxidase label).We speculate that the P2X(6) receptors at the neurohypophysial level may be implicated not only in hormone release from the axon terminals, but also in membrane recycling of the granular vesicles and microvesicles.     

Distribution of serotonin in the caudal neurosecretory complex A light and electron microscopic study

Summary The caudal neurosecretory complex (CNc) of poecilids has previously been shown to receive serotonergic inputs. In the present study, immunohistochemical techniques were applied at the light and electron microscopic levels to characterize serotonergic terminals in the neuroendocrine nucleus. A dense plexus of varicose fibers observed in the rostral CNc neuropil was absent in the spinal cords of deafferented fish, indicating that the origin of this input was extranuclear. Ultrastructural study revealed no direct contacts between labeled structures and neuroendocrine cells. Non-synaptic terminals (varicosities) were the predominantly labeled structures in the neuropil. Synaptic terminals were observed on cellular and axonal targets in the CNc. Small cells containing 70 nm dense-core vesicles received serotonergic input on their perikarya. Labeled synapses were also found on unlabeled axon terminals which made axoaxonal synapses on neuroendocrine processes. Non-synaptic terminals may be responsible for a variety of serotonin-mediated effects in the CNc. Synaptic interactions with local catecholaminergic and afferent cholinergic inputs to the CNc are likely.     

Enkephalin immunoreactivity in synaptoid elements on glial cells in the rat neural lobe

Opioid peptides were localized in fibres of the rat neural lobe using various immunocytochemical methods at the light- and electron-microscopical level. Leu-enkephalin immunoreactivity was present in beaded fibres distributed throughout the neural lobe. These fibres surround the neurohypophyseal glial cells (pituicytes) and make synaptoid contacts upon their soma and processes. The reaction product was localized both in dense-core vesicles of about 100 nm in diameter and diffusely spread over the cytoplasm. No arguments in support of the co-existence of enkephalins and the neurohypophyseal hormones vasopressin and oxytocin in the same terminal were found.It is suggested that pituicytes might mediate the inhibitory effect of opiod peptides on vasopressin and oxytocin release from the neural lobe.     

大鼠孤束核向伏核投射的神经元接受迷走神经的初级传入——溃变与HRP追踪结合法的电镜观察

本文用切断一侧结状神经节近侧端的迷走神经和HRP注入伏核逆行追踪相结合的方法,在电镜水平对孤束核向伏核投射的神经元是否接受迷走神经初级传入纤维终末进行了研究。在孤束核内可见下列突触关系:(1)溃变轴突终末与HRP逆标树突形成轴-树突触;(2)无标记正常轴突终末与HRP逆标胞体或树突分别形成轴-体或轴-树突触;(3)HRP顺标轴突终末与无标记树突形成轴-树突触;(4)溃变轴突终末与无标记树突形成轴-树突触。由上述结果可知:孤束核向伏核投射的神经元接受迷走神经的初级传入终末;伏核神经元的下行终末与孤束核内的神经元之间有突触联系。     

Morphologic features of the caudal neurosecretory system in the blueback herring, Pomolobus aestivalis

The caudal neurosecretory system of the blueback herring, Pomolobus aestivalis, captured in freshwater, was examined. Neurosecretory cells were identified readily in terminal spinal cord segments. The axonal processes of these neurosecretory cells formed a discrete, ventrally placed bundle which terminated in a conspicuous ventral enlargement from the filum terminale. This enlargement comprises the neurohaemal contact zone or urophysis. The neurosecretory terminals were engorged with secretory granules in these fishes from a freshwater environment. The non-neuronal component of the urophysis also was examined in this study. These glial cells were dispersed throughout the urophysis. Most often they were found ensheathing the terminal neurosecretory processes. These cells showed a resemblance to neurohypophysial pituicytes. Although mentioned in the literature, these glial cells have not been examined with the electron microscope. The ultrastructural features of the glial cells and their relation to the neurosecretory constituents are described in this report.