Schwann细胞发生发育过程中和周围神经损伤后的表型表达及其影响因素

Schwann细胞（SCs）起源于胚胎的神经嵴细胞，是周围神经系统（PNS）的髓鞘形成细胞，包绕或包裹PNS的轴突形成有髓或无髓神经纤维。SCs不仅在整个发育过程中与PNS存在着密切联系，如对发育中周围神经元的存活、成熟有髓纤维的跳跃式传导等，而且在周围神经损伤后，还可逆分化为幼稚状态形成Btingner带，分泌神经营养因子，促进离断轴突的出芽再生，并重新包绕再生的轴突形成髓鞘，从而在中枢及周围神经的损伤再生及修复中发挥重要作用。因此，SCs具有广阔的研究及应用前景。本文就SCs的生长发育过程以及各阶段的表型表达和影响因素加以综述。     

细胞因子对少突胶质细胞增殖的调节作用

少突胶质细胞（Oligodendrocyte）是中枢神经系统（CNS）的成髓鞘胶质细胞，包绕神经元轴突形成髓鞘，作为绝缘层保证轴突进行正常快速电传导。近年来研究认为，少突胶质细胞还具有为中枢神经系统提供营养因子和生长因子、表达轴突生长抑制因子等作用，与中枢神经系统的损伤修复具有密切的联系。     

少突胶质细胞增殖和分化的研究进展

少突胶质细胞 ( oligodendrocyte,简称少突胶质 )是中枢神经的成髓鞘神经胶质细胞 ,它包绕神经纤维的轴突而形成髓鞘 ,对轴突正常快速电传导等功能具有重要作用 [1 ]。无论是病理性的髓鞘结构完整性受到破坏 ( demyelination) ,如外伤、多发性硬化症 ( multiple sclerosis) ,还是少突胶质发育紊乱导致髓鞘形成不良 ( dysmyelination) ,如先天性小脑症( congenital microcephaly)和婴儿孤独症 ( infantile autism)等[2 ,3 ] ,都可引起严重的中枢神经系统病变。因而对少突胶质细胞增殖和分化的研究在发育生物学中有重大意义。1.　不同发育时期…     

一种新颖的神经胶质细胞-嗅鞘细胞

嗅鞘细胞(OECs)移植治疗脊髓损伤(SC I)已显示出良好的应用前景,不同来源的OECs体外培养时,在不同发育阶段和不同生长环境中具有不同的生物学特性。OECs具有特异性的标志蛋白,如S-100、p75NTR、GFAP等。体外培养的OECs分泌NGF、BDNF、NT-3/4、GDNF等多种促进神经细胞生长、分化和神经纤维再生的神经营养因子。将OECs植入脊髓损伤部位,该细胞能分裂增殖,并可抑制胶质瘢痕的形成,拮抗Nogo等神经再生抑制性因子的活性,包绕再生轴突形成髓鞘。由于OECs具有上述独特的生物学功能,被认为是继神经干细胞和雪旺氏细胞之后可用于移植治疗脊髓损伤的一种新颖的神经胶质细胞。     

海藻纤维膜片促进大鼠损伤坐骨神经的再生

背景：课题组和青岛大学高分子材料研究所合作研制的海藻纤维生物膜,具有优良的生物相容性,常被用作制备各种复合材料。 目的：观察海藻纤维膜片包绕覆盖神经断端吻合口对大鼠坐骨神经损伤后再生的影响。 方法：切断36只雄性Wistar大鼠右侧坐骨神经,随机分组：对照组行神经外膜端端吻合;实验组行神经外膜端端缝合,将海藻纤维膜片包绕并覆盖神经吻合口远近端各约0.5 cm,形成封闭再生室。术后观察海藻纤维膜片降解吸收规律及缝合处粘连情况,组织学切片行苏木精-伊红染色、锇酸染色、白细胞介素2及白细胞介素4免疫组织化学染色。 结果与结论：术后4-6周,实验组海藻纤维膜片逐渐被降解吸收,与周围组织粘连较少,炎性细胞浸润程度较轻,纤维组织增生较少。两组术后1,7,14 d的白细胞介素2及白细胞介素4含量比较差异无显著性意义。实验组术后6周再生神经纤维分布规则且大小较为均一,其神经纤维数量、轴突大小及髓鞘厚度等指标均显著优于对照组(P < 0.05)。表明海藻纤维膜片具有良好的生物降解性和组织相容性,其包绕覆盖坐骨神经形成的神经再生密闭室可促进大鼠损伤坐骨神经再生。中国组织工程研究杂志出版内容重点：生物材料;骨生物材料; 口腔生物材料; 纳米材料; 缓释材料; 材料相容性;组织工程全文链接：     

PDLLA/NGF复合膜用于自体神经移植促进神经再生实验研究

目的：探讨外消旋聚乳酸／神经生长因子(PDLLA／NGF)复合膜用于自体神经移植是否具有促进神经再生作用。方法：雌性Wistar大白鼠16只，随机分为2组：A组(自体神经移植)8只；B组(自体神经移植并包绕PDLLA／NGF复合膜)8只。显露每只动物的右侧坐骨神经，A组将坐骨神经切除10mm长一段，以外膜缝合法行原位移植；B组与A组同样行神经原位移植并在远近两个神经缝接部位各包绕1块PDLLA／NGF复合膜(含NGF总量为400u)。6个月后观察比较两组神经再生情况。结果：B组的小腿三头肌湿重恢复率、运动神经传导速度、再生的有髓神经纤维数量、直径、轴突直径、髓鞘厚度均优于A组：结论：PDLLA／NGF复合膜包绕自体神经移植的神经缝接部位具有促进神经再生作用.     

大鼠视网膜内髓鞘形成模型的建立与研究

目的研究体外培养的大鼠纹状体神经干细胞在植入同种视网膜后,向少突胶质细胞分化并产生髓鞘的过程,观察髓鞘形成对视网膜结构的可能影响,建立一种中枢神经髓鞘体内发育的新模型.方法将体外传代培养的胚胎纹状体神经干细胞植入新生大鼠的玻璃体腔内,在移植后不同时期观察视网膜内髓鞘的出现部位以及扩展趋势,利用不同染色方法对标本进行检验分析,利用透射电镜进行超微结构观察.结果移植细胞4周后部分视网膜内开始出现成束髓鞘,只分布于神经纤维层.髓鞘束出现的比例、分布面积和形态变化与移植后动物的存活时间相关.电镜观察可见节细胞轴突外包绕有结构正常的中枢神经样髓鞘.较厚的髓鞘束对视网膜节细胞的分布产生一定影响.结论大鼠纹状体神经干细胞可在同种视网膜内向成熟少突胶质细胞分化,视网膜神经纤维层具有促使髓鞘形成的作用;本实验可能为研究少突胶质细胞分化及髓鞘生成机制提供新的在体模型.     

鉴定干细胞及描述已分化细胞类型特征时的常用标志(二)

神经系统CD1 33神经干细胞、HSC 识别神经干细胞的一种细胞表面蛋白 ,神经干细胞可形成神经元和神经胶质细胞。胶质纤维酸性蛋白 (glialfibrillaryacidicprotein ,GFAP) 星形胶质细胞星形胶质细胞特异性产生的一种蛋白。微管相关蛋白 2 (microtubule associatedprotein 2 ,MAP 2 ) 神经元 树突特异性的MAP ,是神经元树突上发现的一种特异性蛋白。髓鞘碱性蛋白 (myelinbasicprotein ,MPB) 少突胶质细胞 由成熟少突胶质细胞产生的一种蛋白 ,位于包绕神经元结构的髓鞘中。巢蛋白 (nestin)神经祖细胞原始神经组织表达的一种中间丝结构…     

老年大鼠视上核胶质突起包绕轴突和终末的电镜观察

在透射电下观察了老年大鼠视上核中胶质突起对神经元成分的包绕。发现胶质突起形成１～５层的多层状鞘样结构，主要包绕于轴突，终末和突触等，被包绕的这类神经元成分中常聚集有神经分泌颗粒，各种突触沁泡等。文中还对该结构出现的机能意义及其发生年龄性变化的可能性作了探讨。     

桡神经鞘膜瘤的显微外科治疗1例

<正>神经鞘膜瘤是临床常见的起源于神经鞘细胞(Schwann scell)的良性肿瘤,其生长特点是神经穿入瘤外包膜,其包膜亦成为该段神经鞘膜的一部分,瘤体紧附在神经纤维上,或包绕在神经纤     

A comparison of the density of microtubules in the central and peripheral axonal branches of the pseudounipolar neurons of lizard spinal ganglia

The number and density of microtubules were determined in cross sections of the two branches (central and peripheral) of the bifurcating axon of the pseudounipolar neurons of the lizard thoracic spinal ganglia. In both the central and peripheral branches the average number of microtubules rose, while the microtubular density decreased with an increase in the cross-sectional area of the axonal branch: More precisely, a linear relationship was observed between the logarithm of the microtubular density and the cross-sectional area of the axonal branch. Both the average number of microtubules per cross section of the axonal branch and the microtubular density were found to be significantly lower in the central than in the peripheral branch. Since the amount of material carried by fast transport was found by other authors to be greater in the peripheral than in the central branch, a positive correlation seems to exist between microtubular density and the quantity of material carried by fast transport along the two branches of the axon in pseudounipolar neurons. Such a correlation suggests that microtubules may be somehow involved in the fast transport of material along the axon. The average densities of microtubules were found to be the same comparing two sets of unmyelinated and myelinated central (or peripheral) branches of corresponding size. Therefore, different microtubular densities usually observed in unmyelinated and myelinated axons appear to be correlated with the different size ranges of the two types of axon rather than with the absence or presence of the myelin sheath.     

Myelination and remyelination in the regenerating visual system of the goldfish

Summary The remyelination of regenerated optic axons was investigated in goldfish following either optic nerve crush or ouabain retinal intoxication. Axons grown after nerve crushing acquire thinner myelin sheaths than axons originating from reconstituted ganglion cells. If axons of reconstituted ganglion cells are crushed and allowed to regenerate, the subsequent myelination is weaker than that of control axons not interrupted by crushing, but stronger than that of axons of preexisting retinal ganglion cells.The present results suggest that a neuron is capable of inducing a normally developed myelin sheath when its axon contacts an oligodendrocyte the first time, whereas a neuron whose axon contacts an oligodendrocyte the second time is not capable of forming a normal myelin sheath in the adult animal. The present results also support the notion that the oligodendrocyte requires a neuronal signal for myelin sheath formation.Supported by the Deutsche Forschungsgemeinschaft (Wo 215/5)     

Axonal microtubules: comparative anatomy in vertebrates, including man

The microtubular density was assessed with the electron microscope in 3 microns myelinated fibers, myelin excluded, of 11 species from the following classes: Osteichthyes, Amphibia, Reptilia, Aves, and Mammalia. The average for all species was 20.6 microtubules/microns 2. Dispersion of values was restricted as shown by a coefficient of variation of 15.8. The microtubular content of nonmedullated axons was assessed in trout, lizard, finch, and man. In the four species, the number of microtubules increased with the cross sectional area of the axon. In trout, lizard and finch, the microtubular density decreased from over 100 microtubules/microns 2 in fibers smaller than 0.1 micron 2 to about 30 in 1 micron 2 fibers; in axons of equal size, the packing of microtubules of nonmedullated was similar between them, and with reported values for peripheral axons of cat and rat. In man, the microtubular density of nonmedullated fibers exhibited only a mild decrease with the axonal size. In the finch, myelinated and nonmedullated axons overlapped in the range 0.23-0.60 micron 2 and both groups exhibited similar microtubular densities. We conclude that the packing of microtubules of the vertebrate peripheral axon is a feature largely conserved during evolution.     

实验性变应性脑脊髓炎髓鞘脱失机制的研究

目的：探讨自身免疫性脱髓鞘疾病的中枢神经系统(CNS)髓鞘脱失发生机制。方法：采用同源脑白质匀浆建立猴实验性变应性脑髓炎(EAE)模型，并用流式细胞仪检测血和脑脊液淋巴细胞亚群的变化，用免疫组化技术和电镜观察脑组织病理变化。结果：急性EAE猴脑脊液CD4^ T淋巴细胞明显升高，CD8^ T淋巴细胞和B淋巴细胞轻度升高；颞叶深部白质有大量CD4^ T淋巴细胞和少量CD8^ T淋巴细胞浸润，而对照组均未见变化；髓鞘内板层松解和轴突髓鞘分离，而髓鞘外板层正常，轴突也保存完好，少突胶质细胞(ODC)的部分胞浆明显水肿，线粒体肿胀，嵴模糊或断裂，核部分溶解。结论：提示EAE脱髓鞘免疫因子最早攻击的靶是少突胶质细胞，而不是髓鞘本身。     

Formation of central and peripheral myelin sheaths in the rat: An electron microscopic study

Formation of the myelin sheath in peripheral nerve of the newborn rat is compared with its formation in postnatal cerebral white matter. The unmyelinated central axon is bare and myelination begins by the spiral wrapping of an oligodendrocytic process around the axon. The paired membranes of this process fuse on their inside surfaces, lengthen, and spiral around the axon to make a loose sheath of major dense lines. Compact myelin results after fusion of the outside surfaces to form the intraperiod line. Cytoplasm is sparse in developing central myelin, usually being restricted to inner and outer tongues. Unmyelinated peripheral axons are enclosed within a mesaxon formed by the invagination and fusion of the outside surfaces of the Schwann cell plasma membranes. Loose myelin is produced by lengthening and spiralling of the mesaxon (intraperiod line) around the axon. As Schwann cell cytoplasm is extruded from between the spirals, the major dense line forms and compact myelin results. Trapped cytoplasm, a characteristic of developing peripheral myelin, is found in the internodal compact myelin sheath as the inner and outer collars and the Schmidt-Lanterman clefts.     

Axon-myelin sheath relations of oligodendrocyte unit phenotypes in the adult rat anterior medullary velum

Axon-oligodendrocyte relations of Rip-immunolabelled and dye-injected oligodendrocyte units are characterised in the adult rat anterior medullary velum (AMV). Each oligodendrocyte unit comprised the oligodendrocyte cell body, processes and the internodal myelin segments they support. Oligodendrocyte units corresponded to classically described type I/II or type III/IV unit phenotypes which respectively myelinated discrete populations of small and large diameter axons, delineated by a myelinated fire diameter of 2-4 microns (diameter of the axon plus its myelin sheath). Within units, mean fibre diameter was directly related to mean internodal length and inversely related to the number of myelin sheaths in the unit. The relationship between fibre diameter and internodal length was retained in units which myelinated axons of different diameters, indicating that axon diameter was an important determinant of the longitudinal dimensions of myelin sheaths. We also show that type III/IV units maintained a far greater volume of myelin than type I/II units. It was concluded that type I/II and III/IV oligodendrocytes represent two functionally and morphologically distinct phenotypes whose distribution densities were determined by the diameter and spatial dispersion of axons.     

Structure of rat aortic baroreceptors and their relationship to connective tissue

Summary The ultrastructure of fibres and sensory terminals of the aortic nerve innervating the aorta between the left common carotid and left subclavian arteries was investigated in the rat. This is the region from which most baroreceptor responses are recorded electrophysiologically. The fibres of the aortic nerve enter the adventitia and separate into bundles generally containing one myelinated fibre and four or five unmyelinated fibres of various sizes. The bundles pursue a roughly helical course through the adventitia; when they are close to the aortic media, the myelinated fibre loses its myelin sheath. A complex sensory terminal region is formed, as both the unmyelinated and premyelinated axons become irregularly varicose. The concentration of mitochondria becomes very dense and cytoplasmic deposits of glycogen are observed. Both unmyelinated and premyelinated axons branch, and the unmyelinated axons wind irregularly around the premyelinated axon. The latter may have several loops and small holes. The terminal regions of both types of axon contain clusters of clear 40 nm vesicles. Part of the surface of each terminal region is ensheathed by Schwann cells, but the rest of the axolemma is directly exposed to extracellular connective tissue. There are often several layers of basal lamina around the sensory terminals and parts of the axolemma and Schwann cell membranes are attached to it by fine fibrillar material. The basal laminae are also attached to fibroblasts, fibroblast-like perineurial cells and elastic laminae, and the whole cellular and extracellular system appears to be tightly bound together. No differences between baroreceptors of spontaneously hypertensive and normal rats were found.     

野木瓜皂甙对大鼠神经髓鞘和轴突膜的作用

本文作者等曾发现将镇痛中草药野木瓜注射液 (IS)涂布于大鼠隐神经可导致 C类纤维轴突膜膨胀、边界模糊 ;Aδ类纤维髓鞘出现较多的空洞和髓鞘崩解。本实验从 IS中提取了野木瓜皂甙 (SS)并将 0 .3 % SS涂布于大鼠隐神经 ,经电生理研究和电镜观察发现 :60 min后隐神经复合动作电位 A成分的传导被阻滞 ,并发现 A纤维髓鞘和 C纤维的轴突膜以及神经干的胶原纤维出现类似涂布 IS后出现的黑色斑块 ,并出现了局部的髓鞘崩解和轴突膜增厚并变模糊的现象。表明 SS对髓鞘和轴突膜有亲和力 ,可引起髓鞘和轴突膜结构的变化 ,从而导致神经传导阻滞     

视神经损伤后视神经及其内毛细血管的早期超微结构的变化

目的观察视神经损伤后视神经和神经内毛细血管的超微结构变化,探讨视神经损伤的机制。方法建立家兔视神经损伤的动物模型,利用透射电子显微镜观察视神经及神经内毛细血管超微结构的变化。结果视神经损伤0.5h后,轴突部分肿胀,髓鞘疏松,微管、微丝排列出现紊乱,线粒体肿胀,毛细血管内皮细胞中的吞饮小泡和微绒毛明显减少;损伤6h后,线粒体出现髓样变和空泡样变性,血管内皮细胞肿胀,管腔变窄;损伤12h后,轴突空泡样变性,髓鞘脱失,毛细血管周围间隙增宽;损伤48h后,轴质密度增加,部分髓鞘板层完全分离,微管、微丝及线粒体发生颗粒性溶解,内皮细胞中的线粒体出现广泛变性;损伤96h时,轴索崩解呈空泡状变性,髓鞘更广泛崩解,毛细血管扩张破裂,红细胞外溢。结论视神经损伤早期轴突肿胀、空泡样变性,线粒体水肿变性,微管、微丝数量减少;视神经内毛细血管扩张,通透性增加。     

基于对称区域生长和边缘梯度的视神经纤维的分割

在视神经横切面图像中,将每个神经纤维的内外边界进行精确分割是视神经形态分析的重要环节,提出一种基于对称区域生长和髓鞘边缘梯度的有效分割算法.该算法分两步进行,首先根据交互方式下选取的种子点,由对称区域生长算法实现轴突分割,然后在轴突轮廓模型基础上,髓鞘外轮廓在髓鞘平均边缘梯度引导下进行演化,实现自动分割.与K-均值聚类,局部阈值和水平集等其他算法的实验结果相对照显示,该算法分割获得的轴突和髓鞘轮廓与实际轮廓相吻合,其分割结果可以作为后续神经纤维形态分析的基础.