免疫介导豚鼠脊髓运动神经元损伤的超微结构及钙稳衡改变

应用常规透射电镜及草酸盐-焦亚锑酸盐技术原位固定细胞内钙,对豚鼠脊髓前角细胞内的钙分布进行超微定位,探讨钙稳衡改变在免疫介导运动神经元损伤中的作用.结果发现模型组豚鼠脊髓前角运动神经元可见粗面内质网扩张、线粒体肿胀、嵴排列紊乱等.神经元周围胶质细胞增生.在运动神经元扩张的粗面内质网池和线粒体内室可见数量不等颗粒状电子致密的钙沉积物.线粒体内室内钙沉积颗粒与线粒体肿胀的程度相关.星形胶质细胞内肿胀的线粒体内室及扩张的粗面内质网池内也可见电子致密钙沉积颗粒.因此认为,钙稳衡失调参与了免疫介导的运动神经元损伤过程.     

人胎儿脊髓前角运动神经元NLY的电镜观察

人胎儿脊髓前角运动神经元ＮＬＹ的电镜观察＊任昊石玉秀（中国医科大学组胚教研室，沈阳１１０００１）＊国家自然科学基金资助项目（Ｎｏ．３９５７０３７７）我们利用酶细胞化学方法曾对大鼠、豚鼠中枢神经细胞的线状溶酶体（Ｎｅｍａｔｏｌｙｓｏｓｏｍｅ，ＮＬＹ）进...     

实验性免疫介导的运动神经元损伤中神经丝异常的超微结构观察

为了观察免疫介导的神经元损伤过程中脊髓前角运动神经元超微结构的病变特征，将新鲜的猪脊髓前角匀浆加佐剂注入Lewis大鼠的背部皮下，每月一次，连续四个月。在最后一次免疫后2个月，灌注固定取材。制作超薄切片，应用光镜及透射电镜观察脊髓前角运动神经元及其突起的形态学改变。结果发现脊髓前角运动神经元有不同程度的变性、丢失。残存神经元的核周体内有排列紊乱的神经丝异常聚集，构成有界膜包绕的球形或类圆形包涵体，其突起内还有大量线粒体和溶酶体聚集。其次，尚可见线粒体变性及高尔基复合体扁囊和粗面内质网池的扩张。因此认为，在免疫介导的神经元损伤过程中，神经丝的异常聚集可能与神经元的变性、丢失有关。     

脊髓前角运动神经元GR受体免疫电镜观察

近年肾上腺皮质激素的糖皮质激素受体 ( Glucocorticoid receptor.GR)在脑神经细胞分布与作用的研究已倍受关注[1] ,脊髓 GR受体的分布尚未见报道 ,本研究采用免疫组织细胞化学方法对 GR受体在脊髓前角运动神经元的超微结构定位进行了电镜观察 ,为进一步探讨 GR受体对脊髓功能的作用机制提供形态学依据。材料与方法　实验动物为成熟 Wistar大鼠 (体重 2 5 0～ 30 0 g) ,全身麻醉下 ,用 4%多聚甲醛( 0 .1 mol/ L PBS缓冲液配制 )固定液心脏灌流固定 ,摘出脊髓 ,用同种固定液再继续浸泡固定一夜 ,同上缓冲液洗净标本 ,采用 microslicer(…     

去细胞神经移植后再生神经纤维超微结构的观察

应用化学方法去除神经中的细胞成分并经γ射线辐照后进行家兔同种异体移植实验,分别对移植后6、8、12周再生的神经进行超微结构观察。结果表明：去细胞神经中的雪旺氏细胞成分基本缺失,仅残存一些膜状结构碎片。有髓神经纤维髓鞘明显破坏,神经纤维外周胶原纤维及其组成的膜结构基本保持完整。移植术后植入物内可观察到增生的雪旺氏细胞包裹再生的轴突形成有髓神经纤维和无髓神经纤维,其轴突内可见线粒体、神经微管、微丝。再生神经纤维的形态、结构及直径均与正常神经相似。表明植入物逐渐被新生的神经纤维所取代。     

氦-氖激光穴位照射对脊髓后角SP及ENK的影响——免疫组织化学研究

激光照射“穴位”(简称光针)具有镇痛作用,已在临床实践和实验研究中获得广泛证明。光针可以抑制脊髓后角痛敏神经元放电,光针镇痛与其能促进体内吗啡样物质释放有关。 脊髓后角是痛觉调制的初级中枢,有关痛觉传递假说都涉及到脊髓后角内的P物质(SP)和脑啡肽(ENK)。SP与伤害性初级传递有关;ENK是体内吗啡样物质,与痛觉的调制有关。SP与ENK在脊髓后角的形态分布基本相似,提示两者之间在痛觉的传递上存在密切的功能联系。我们观察了光针后大鼠的痛阈变化,并采用免疫组化方法观察了光针后脊髓后角SP和ENK的变化规律,为光针镇痛机理提供了某些依据。     

纳米金-银加强法对大鼠和猴脊髓后角内P物质定位的实验研究

包埋前纳米金－银加强法已较广泛地应用于对神经递质和受体的超微定位研究，被证明是一种敏感和高分辨率的方法。Ｐ物质是在脊髓后角内十分丰富的一种神经肽，我们应用这一技术研究Ｐ物质的定位时，发现当大致密芯泡的泡芯密度高时，其内的神经肽无法被纳米金－银颗粒标记，只在泡膜附近有金－银颗粒标记，这一现象在猴的脊髓后角神经终末中尤为明显，虽然这个缺点不影响研究含这种神经肽的神经终末与其它结构的关系，但据此结果来阐     

激光照射对急性脊髓损伤后脊髓再生的促进作用

建立大鼠皮质脊髓背侧束全横断模型,利用弱激光照射脊髓受损部位的皮肤,观察激光照射对急性脊髓损伤后脊髓再生的促进作用.30只SD大鼠,随机分成对照组和照射组.照射组:急性皮质脊髓背侧束全横断后15 min进行连续14 d采用弱激光照射脊髓受损部位的皮肤.对照组:急性皮质脊髓背侧束全横断后未行弱激光经皮照射治疗.术后两组分别于第3,7,14 d分别取材,用苏木精-伊红染色法(HE)染色和免疫荧光标记染色观察.实验发现,脊髓损伤后14 d,照射组的空洞及瘢痕形成面积小于对照组,有统计学差异(p<0.05);对照神经胶质酸性组蛋白(GFAP)和硫酸软骨素(CS)表达强烈分布紧密,照射组GFAP和CS56表达达微弱且分布稀疏;对照组少量神经微丝蛋白(NF)在损伤区周围,神经生长相关蛋白(GAP43)形态肿大变形分布紊乱,照射组大量成纤维丝状的NF分布在损伤区周围,并与GAP43相伴行.结果表明,脊髓损伤急性期采用弱激光照射脊髓受损部位的皮肤,可减少脊髓损伤后空洞形成,并促进轴突再生.     

大鼠损伤性坐骨神经远侧端中雪旺细胞的超微形态学观察

雪旺细胞是周围神经的胶质细胞 ,不仅与周围神经的髓鞘形成有关 ,近年来的研究发现在周围神经修复过程中亦起着重要的作用。研究周围神经损伤后雪旺细胞的形态结构变化 ,对揭示周围神经的损伤及再生机制有一定的理论意义。材料和方法　雄性或雌性 SD大鼠 ,2 0 0 g± 5 0 g共 1 2只 ,分对照组 4只 ,实验组 8只。实验模型制备按照既往报道。术后 2周处死大鼠 ,取对照组大腿中段之坐骨神经及实验组损伤神经的远侧端 ,按电镜常规制样 ,观察摄片。结果　一、对照组坐骨神经的超微结构观察 :低倍镜下有髓神经纤维之髓鞘均匀规则分布 ;神经纤维间…     

周围神经修复过程的超微结构研究

为了解周围神经损伤后的修复过程，观察了大鼠坐骨神经冷冻损伤当时至４周后的超微结构。发现冷冻损伤后３天，除变性神经纤维外，有新生轴突，皆由雪旺细胞包裹着。１周皇一神经纤维已较丰富，以无髓纤维为多，遥髓纤维罕见，且髓鞘较薄，雪量细胞和巨噬细胞皆吞噬变性的神经纤维。此后，形态正常的雪旺细胞和神经纤维渐多，被吴噬的变性物质渐少，直至损伤４周后，神经组织恢复到基本正常，但仍可见少量被吞噬的髓样结构。这提示，     

Recruitment of dorsal column fibers in spinal cord stimulation:influence of collateral branching

An electrical network model of myelinated dorsal column nerve fibers is presented. The effect of electrical stimulation was investigated using both a homogeneous volume conductor and a more realistic model of the spinal cord. An important feature of dorsal column nerve fibers is the presence of myelinated collaterals perpendicular to the rostro-caudal fibers. It was found that transmembrane potentials, due to external monopolar stimulation, at the node at which a collateral is attached, is significantly influenced by the presence of the collateral. It is concluded that both excitation threshold and blocking threshold of dorsal column fibers are decreased up to 50% compared to unbranched fibers.     

Analysis of calcitonin gene-related peptide (CGRP)-containing nerve fibres in the rat spinal cord using light and electron microscopy.

Calcitonin gene-related peptide (CGRP) content in areas surrounding the central canals of cervical, thoracic, lumbar and sacral spinal cords of rats were investigated by light microscopy, conventional transmission electron microscopy (CTEM) (100-200 kV) and high-voltage transmission electron microscopy (HVTEM) (1000 kV) using immunocytochemistry. Tissues were examined using either the peroxidase-antiperoxidase technique or an immuno-cryoultramicrotomy technique. Light microscopically, more intense CGRP localization was observed ventral to the central canals in the lumbar and sacral cord compared with the dorsal area in the same regions. HVTEM revealed that high levels of CGRP labelling were found adjacent to the basal side of ependymal cells ventral to the central canal. Analysis using CTEM operated at 200 kV demonstrated that the CGRP immunoreactivity was present within unmyelinated nerve fibres in the vicinity of the basal side of ependymal cells ventral to the central canal. Immuno-cryoultramicrotomy revealed that immuno-gold particles indicating CGRP labelling were localized on vesicle-like electron-dense bodies in unmyelinated and some fine caliber myelinated nerve fibres. Existence of CGRP as a primary afferent marker in the area surrounding the central canal suggest that there may be an intimate relationship between the modulation of nociceptive information and the area surrounding the central canal in rat spinal cord.     

Estimation of fiber diameters in the spinal dorsal columns fromclinical data

Lack of human morphometric data regarding the largest nerve fibers in the dorsal columns (DCs) of the spinal cord has lead to the estimation of the diameters of these fibers from clinical data retrieved from patients with a new spinal cord stimulation (SCS) system. These patients indicated the perception threshold of stimulation induced paresthesia in various body segments, while the stimulation amplitude was increased. The fiber diameters were calculated with a computer model, developed to calculate the effects of SCS on spinal nerve fibers. This computer model consists of two parts: (1) a three-dimensional (3-D) volume conductor model of a spinal cord segment in which the potential distribution due to electrical stimulation is calculated and (2) an electrical equivalent cable model of myelinated nerve fiber, which uses the calculated potential field to determine the threshold stimulus needed for activation. It is shown that the largest fibers in the medial DCs are significantly smaller than the largest fibers in the lateral parts. This finding is in accordance with the fiber distribution in cat, derived from the corresponding propagation velocities. Moreover, it is shown that the mediolateral increase in fiber diameter is mainly confined to the lateral parts of the DCs. Implementation of this mediolateral fiber diameter distribution of the DCs in the computer model enables the prediction of the recruitment order of dermatomal paresthesias following increasing electrical stimulation amplitude     

Epidural spinal cord stimulation: calculation of field potentialswith special reference to dorsal column nerve fibers

The effect of electrical stimulation with several electrode combinations on nerve fibers with different orientations in the spinal cord was investigated by computing the steady-state field potentials and activating functions. At first an infinite homogeneous model was used while secondly the spinal cord and its surrounding tissues were modeled as an inhomogeneous anisotropic volume conductor. The effect of mediodorsal epidural stimulation was calculated. It was concluded that with cathodal stimulation, mediodorsally in the epidural space, longitudinal fibers are depolarized, but dorsoventral ones are hyperpolarized. With anodal stimulation the opposite will occur. It was found that parameters substantially affecting the potential distribution in the dorsal columns are the conductivity of the white matter and the width and the conductivity of the csf layer.     

Excitation of dorsal root fibers in spinal cord stimulation: atheoretical study

In epidural spinal cord stimulation it is likely not only that dorsal column fibers are activated, but also that dorsal root fibers will be involved as well. In this investigation a volume conductor model of the spinal cord was used and dorsal root fibers were modeled by an electrical network including fiber excitation. The effects of varying some geometric fiber characteristics, as well as the influence of the dorsal cerebrospinal fluid layer and the electrode configuration on the threshold stimulus for their excitation, were assessed. The threshold values were compared with those of dorsal column fibers. The results of this modeling study predict that, besides the well known influence of fiber diameter, the curvature of the dorsal root fibers and the angle between these fibers and the spinal cord axis are a major influence on their threshold values. Because of these effects, threshold stimuli of dorsal root fibers were relatively low as compared to dorsal column fibers. Excitation of the dorsal root fibers occurred near the entry point of the fibers     

Transformation of cortical motor signals in spinal cord

A review of the neuronal organization of the corticospinal (pyramidal) system is presented. Parameters of pyramidal tract fibers are described; special attention is paid to the existence of pyramidal neurons with fast- and slow-conducting axons which have different locations of somata over the sensorimotor cortex, different locations of terminals on spinal neurons, and different parameters of impulse activity. Two types of pyramidal descending action are considered: direct action of corticifugal signals upon motor units, and control of sensory flow to motor units and higher brain centers. Corticifugal motor signals produce predominantly excitatory postsynaptic potentials in flexor and inhibitory ones--in extensor motoneurons. The following types of connections between pyramidal fibers and motoneurons are distinguished: 1) monosynaptic connections (only in primates), 2) connections via propriospinal interneurons localized in the external basilar region and specialized for transmission of pyramidal fiber activity only, and 3) connections via interneurons of the internal basilar region and intermediate zone which transmit both segmental afferent and pyramidal activity. Evidence is presented that the activity of fast-conducting pyramidal fibers via the first two types of connections creates phasic synaptic processes in motoneurons while slow-conducting fibers via the third type render the tonic action. Properties of corresponding interneuronal groups are specialized for transmission of phasic and tonic signals. The types of pyramidal control of sensory flow considered are: 1) postsynaptic facilitation and inhibition of interneurons of segmental reflex arcs, 2) postsynaptic facilitation and inhibition of transmission via ascending pathways, 3) presynaptic inhibition of primary afferent activity, and 4) postsynaptic influences on γ-motoneurons.     

综合康复措施治疗脊髓损伤中枢性疼痛的临床观察

目的:探讨综合康复治疗措施对脊髓损伤后中枢性疼痛的治疗效果.方法:对31例脊髓损伤后中枢性疼痛患者采用阿米替林、按摩、心理治疗及经皮神经电刺激(TENS)进行治疗.采用McGill疼痛问卷(McGill pain questionnaire,MPQ)、疼痛视觉模拟评分法(Visual Analogous Score,V...     

Microfabricated cylindrical multielectrodes for neural stimulation

The effects of spinal cord injuries are likely to be ameliorated with the help of functional electrical stimulation of the spinal cord, a technique that may benefit from a new style of electrode: the cylindrical multielectrode. This paper describes the specifications for, fabrication techniques for, and in vitro evaluation of cylindrical multielectrodes. Four tip shapes were tested to determine which shape required the lowest peak force and would, therefore, be expected to minimize dimpling during implantation. The impedance of the electrode interface was monitored for changes due to insertion as well as repetitive delivery of current pulses. The charge delivery capacity was determined by testing with safe (< or = 0.6 mC/cm2) and damaging levels (> or = 0.8 mC/cm2) of charge density. The results of these tests suggest that this electrode design could be used to stimulate neurons in the ventral horn of the spinal cord.