荧光染料在视神经脊髓鞘形成期从轴突至少突胶质细胞的扩散

将真蓝(true blue)混悬液注入出生后7、14、28d大鼠眼球内,经过一定时间后,视神经内的轴突和少突胶质细胞被荧光标记。荧光强度在视神经眼球端强于视神经交叉端;出生后14～28d的幼鼠荧光标记明显强于出生后7d的幼鼠;不同年龄组的动物荧光标记普遍在注射荧光染料后的第5d显著增强。本研究表明,荧光染料可被视网膜的节细胞吸收,经轴突输送,然后,横向扩散到少突胶质细胞,扩散的通路可能是朗氏结旁区的轴胶连接。     

不同磷脂肽段诱导的实验性自身免疫性脑脊髓炎模型病理特征多样性的研究

目的:探索是否不同磷脂肽段可以诱导Lewis大鼠产生不同的病理学表现。方法:采用髓鞘碱性蛋白82-99(MBP82-99)、MBP68-86、髓鞘少突胶质细胞糖蛋白35-55(MOG35-55)免疫Lewis大鼠,每天进行神经功能评分。免疫后取各组大鼠大脑、小脑、脑干和脊髓组织,观察炎性细胞浸润部位和浸润程度、有无脱髓鞘和轴索损害。结果:MBP68-86和MBP82-99两组大鼠的大脑、脑干、小脑和脊髓组织均有炎性细胞浸润,脊髓炎症程度重于其他部位;MBP68-86和MBP82-99诱导的脊髓炎症程度无统计学差异;MOG35-55组大鼠仅脊髓组织受累,且炎症程度明显低于MBP组,其余各组未见炎性细胞浸润。各组大鼠神经组织均未见脱髓鞘和轴索受累。结论:不同磷脂肽段诱导Lewis大鼠神经组织炎性细胞浸润的分布和程度不同。     

Neuron-oligodendroglial interactions during central nervous system development

It is well established that a variety of growth factors influence the differentiation of oligodendroglial lineage cells in culture, although little information is available concerning the role and source of these factors in vivo. Developing oligodendroglia are almost constantly in a neuronal environment and would be expected to respond to a variety of signals from neurons that affect their survival, migration, division, maturation and myelin production. However, very little is known about the specific interactions that occur between these two cell types. Here we review the experimental evidence for the influence of neurons on oligodendroglial differentiation, including studies on the effects of both soluble factors and contact dependent events. We also propose a scheme for the control of myelinogenesis via both internal and external signals. © 1993 Wiley-Liss, Inc.     

The response of optic tract glia during regeneration of the goldfish visual system. II. Tectal factors stimulate optic tract glia

After transection, retinal ganglion cell axons of the goldfish will regenerate by growing into a primary target tissue, the optic tectum. To determine what role the target tissue may play in regulating glial cell growth, we measured biosynthetic activity of optic tract glia following excision of the optic tectum and compared it to activity of glia found in the regenerating visual system. Ablation of the tectum reduced glial incorporation of both [³H]thymidine and [³⁵S]methionine. Tectal ablation also led to nearly 80% reduction of amino acids incorporated by oligodendroglia as well as a decrease in the amount of newly synthetized protein found within multipotential glia and within cytoplasmic projections of astroglia. Since the tectal influence upon optic tract glia was detected at a time when tract and tectum are physically separated, we sought to determine if the optic tectum contained soluble glia-promoting factors. A soluble fraction recovered from tecta of the regenerating visual system increased amino acid incorporation within optic tract glia at 2–3-fold above preparations incubated with fractions from control, intact tecta. Comparisons of radiolabeled proteins separated by sodium dodecyl polyacrylamide gel electrophoresis from regenerating and factor-stimulated optic tract were similar and indicated that a soluble tectal fraction promoted biosynthesis of specific glial proteins. Our findings suggest that during regeneration of the goldfish visual system glia are influenced by humoral factor(s) released from the synaptic target site.     

New oligodendrocytes are generated after neonatal hypoxic-ischemic brain injury in rodents

Neonatal hypoxic-ischemic (HI) white matter injury is a major contributor to chronic neurological dysfunction. Immature oligodendrocytes (OLGs) are highly vulnerable to HI injury. As little is known about in vivo OLG repair mechanisms in neonates, we studied whether new OLGs are generated after HI injury in P7 rats. Rats received daily BrdU injections at P12-14 or P21-22 and sacrificed at P14 to study the level of cell proliferation or at P35 to permit dividing OLG precursors to differentiate. In P14 HI-injured animals, the number of BrdU+ cells in the injured hemisphere is consistently greater than controls. At P35, sections were double-labeled for BrdU and markers for OLGs, astrocytes, and microglia. Double-labeled BrdU+/myelin basic protein+ and BrdU+/carbonic anhydrase+ OLGs are abundant in the injured striatum, corpus callosum, and the infarct core. Quantitative studies show four times as many OLGs are generated from P21-35 in HI corpora callosa than controls. Surprisingly, the infarct core contains many newly generated OLGs in addition to hypertrophied astrocytes and activated microglia. These glia and non-CNS cells may stimulate OLG progenitor proliferation or induce their migration. At P35, astrogliosis and microgliosis are dramatic ipsilaterally but only a few microglia and some astrocytes are BrdU+. This finding indicates microglial and astrocytic hyperplasia occurs shortly after HI but before the P21 BrdU injections. Although the neonatal brain undergoes massive cell death and atrophy the first week after injury, it retains the potential to generate new OLGs up to 4 weeks after injury within and surrounding the infarct.     

Cyclic AMP differentiation of the oligodendroglial cell line N20.1 switches staurosporine-induced cell death from necrosis to apoptosis.

Understanding the regulation of cell death pathways is critical for protecting myelin-producing cells and their associated axons during injury resulting from multiple sclerosis and other degenerative diseases. The immortalized N20.1 oligodendroglial cell line provides a useful model for identifying mechanisms that can be exploited to attenuate cell death in myelin-producing cells and their precursors. In our hands, the N20.1 cell line exhibits different characteristics and morphology depending on temperature (permissive or non-permissive) and the presence of cAMP-elevating agents (Studzinski et al. [1998] Neurochem. Res. 23:435-441; Boullerne et al. [1999] J. Neurochem. 72:1050-1060; Studzinski et al. [1999] J. Neurosci. Res. 57:633-642). Our laboratory previously observed that NO donors cause primarily necrotic death in N20.1 cells grown at permissive temperature, but the NO donor SNP switched a portion of cell death to the apoptic pathway. We have continued our study of apoptotic death in these cells by comparing the effects of staurosporine, a known apoptotic agent, on cells grown at the permissive temperature ("undifferentiated") vs. the non-permissive temperature in the presence of forskolin ("differentiated"). Undifferentiated N20.1 cells exhibit maximal cell death after 24 hr of exposure to 50 nM staurosporine, whereas differentiated cells show delayed cell death, with maximal death seen after 48 hr. Pyknotic nuclei were observed in both growth conditions; however, differentiated cells were protected by caspase inhibitors, whereas undifferentiated cells were not. Increased ssDNA staining and DNA laddering were found following 24-hr staurosporine treatment in the differentiated cells only. These results support the conclusion that N20.1 cells can switch from necrotic to apoptotic cell death when cell division is slowed and cyclic AMP is elevated.     

Morphometric analysis of oligodendrocytes in the adult mouse frontal cortex

Oligodendrocytes (OLs), the myelinating cells of the central nervous system, have specialized morphologies that subserve their function. Numerous qualitative studies suggest that OLs in different brain regions can differ in their morphological characteristics, including number of branches and internodes, internode length, etc. However, progress in identifying and characterizing the diverse types of OLs and their distribution in the brain has been made difficult by several technical constraints. Here we report a new strategy to analyze OL morphology with a high degree of quantitative power and throughput. We used confocal microscopy and three-dimensional cell tracing software to study OLs in the frontal cortex of mice expressing enhanced green fluorescent protein (eGFP) under the control of the proteolipid protein (Plp) gene promoter. Three-dimensional reconstructions were then used to analyze and quantify cell morphology, including total process length, total process surface area, total internode length, number of primary processes, number of branch points, and number of internodes. In addition, these reconstructions were subjected to Sholl analysis, which allows for the quantitative measure of OL arbor complexity. By using this approach, we identified and characterized a previously undescribed population of small OLs with a compact but complex morphology that includes numerous branching processes and a large number of short internodes. Our data suggest that other populations of OLs remain to be identified and characterized and that the tools we have developed could help in the process of characterizing them.     

Oligodendroglial microtubular tangles in multiple system atrophy

Oligodendroglial microtubular tangles (OMT) were observed in the central nervous system in 10 cases of multiple system atrophy (MSA) including eight cases of sporadic olivopontocerebellar atrophy and one case of Shy-Drager syndrome and one of striatonigral degeneration. There was no OMT in two cases of hereditary spinocerebellar degeneration, nor in 46 cases with various neurological and non-neurological diseases. The distribution of OMT was correlated with the location of neurodegenerative changes due to MSA, and the number of OMT with the severity of those changes. Immunoreactivity with anti-ubiquitin and α B-crystallin antibodies was observed by immunohistochemical procedures. It is suggested that the OMT is a pathognomonic change of MSA and confirms the validity of the concept of MSA as a disease entity.     

The long term culture of bulk-isolated bovine oligodendroglia from adult brain

Oligodendroglia isolated from adult bovine brain by the method of Farooq et al. could be plated on polylysine-coated plastic dishes with an efficiency of 55–80%, and maintained in culture for as long as 4 months. The addition of cytosine arabinoside to the nutrient medium resulted in cultures that were approximately 90% oligodendroglia and 10% large fibroblasts. From 50 g of white matter 100 − 160 × 10⁶ oligodendroglia, containing approximately 6–10 mg protein, could be obtained in culture. These small round cells started to send out processes at 5 days in vitro and by 2 weeks they formed an extensive network of processes. By immunofluorescence, all cells of this morphology were positive for galactocerebroside (GC) and myelin basic protein (MBP), and negative for glial filament protein and fibronectin. Most of the large flat cells were positive for fibronectin and negative for GC, MBP and glial filament protein. As the cultures aged the oligodendroglia tented to clump and blebs formed on the surface of both perikarya and processes. By 4 months they showed evidence of degeneration and detached from the substrate. Electron microscopic examination showed that the cells had the appearance typical of oligodendroglia in situ. The somata were round to elliptical, with eccentrically placed nuclei, and were larger than freshly isolated cells. They grew directly on the substrate or on the surface of the fibroblasts. In older cultures the cells formed tight nests. The somata were enveloped by sheets of oligodendrocyte cytoplasm, sometimes having a myelin-like appearance. Gap junctions and small desmosomes were seen between oligodendroglial processes and between oligodendroglia and fibroblasts. The cytoplasm was characterized by a prominent Golgi apparatus, many mitochondria and lysosomes, scattered rough endoplasmic reticulum, free ribosomes, frequent centrioles and an abundance of microtubules. In cells from older cultures large vacuoles were common, and rarely they had multilamellar walls with alternating major and minor dense lines resembling myelin.