弥漫性轴突损伤患者血清神经元特异性烯醇化酶的变化及意义

目的 :探讨弥漫性轴突损伤 ( diffuse axonal injury,DAI)患者血清神经元特异性烯醇化酶 ( neuron specificenolase,NSE)浓度的变化及临床意义。　方法 :选择符合 DAI诊断标准的脑外伤患者 13例 ,均行 CT扫描。于入院时或损伤后 12 h左右采血检测血清中 NSE浓度。　结果 :13例 DAI患者中 ,CT扫描显示颅内有组织撕裂出血改变者 7例 ,脑肿胀者 3例 ,阴性者 3例。 DAI患者血清 NSE值较正常对照组明显升高 ,分别为 ( 46 .5 3± 2 4.2 5 )μg/ L和 ( 6 .96± 2 .5 2 )μg/ L。在死亡或植物生存患者 NSE值升高更明显。　结论 :DAI患者血清 NSE值明显升高 ,血清NSE检测有望成为评估 DAI的一个有价值的特异性指标     

Tensile stretching of cervical facet joint capsule and related axonal changes

This study examines axonal changes in goat cervical facet joint capsules (FJC) subjected to low rate loading. Left C5–C6 FJC was subjected to a series of tensile tests from 2 mm to failure using a computer-controlled actuator. The FJC strain on the dorsal aspect was monitored by a stereo-imaging system. Stretched (n = 10) and unstretched (n = 7) capsules were harvested and serial sections were processed by a silver impregnation method. The mean peak actuator displacement was 21.3 mm (range: 12–30 mm). The average peak strain encompassing various regions of the capsule was 72.9 ± 7.1%. Complete failure of the capsule was observed in 70% of the stretched capsules. Silver impregnation of the sections revealed nerve fibers and bundles in all the regions of the capsule. A blinded analysis of digital photomicrographs of axons revealed a statistically significant number of swollen axons with non-uniform caliber in stretched FJCs. Axons with terminal retraction balls, with occasional beaded appearance or with vacuolations were also observed. Stretching the FJC beyond physiological range could result in altered axonal morphology that may be related to secondary or delayed axotomy changes similar to those seen in central nervous system injuries where axons are subjected to stretching and shearing. These may contribute to neuropathic pain and are potentially related to neck pain after whiplash events.     

重组人Semaphorin3A诱导体外培养的大鼠大脑皮层神经元轴突损伤的实验研究

目的探讨外源性Semaphorin3A(Sema3A)对于体外培养神经元轴突生长及神经元生长活性的影响。方法体外培养新生SD大鼠皮质神经元,随机分为正常对照组和Sema3A不同浓度处理组,倒置相差显微镜及微管相关蛋白-2(MAP-2)荧光染色分别观察生长锥及轴突形态学变化;噻唑蓝(MTT)法检测神经元存活率。结果 Sema3A(0.5mg/ml)处理可诱发神经元生长锥崩解;与正常对照组相比,Sema3A(5mg/ml)处理组轴突平均长度缩短(P0.001);经不同浓度Sema3A处理后,神经元存活率呈剂量依赖性下降,其中浓度范围为0.5~5.0mg/ml的处理组与正常组比较均有统计学意义(P0.001)。结论 Sema3A在体外可发挥明显的促生长锥崩解及抑制轴突生长的作用,并且具有一定的神经元毒性。     

细胞型朊蛋白介导的海马神经元轴突延伸障碍可能参与睡眠剥夺后认知障碍

目的 研究快速眼动睡眠剥夺后大鼠空间记忆功能和海马细胞型朊蛋白(cellular prion protein,PrPC)表达的变化及沉默细胞型朊蛋白对体外培养的海马神经元轴突延伸的影响,探讨睡眠剥夺后认知功能变化的机制.方法 成年SD大鼠按体重大小排序,完全随机法分为3组,分别为正常笼养对照组、水槽对照组、睡眠剥夺组.采用改良多平台睡眠剥夺法进行连续72 h快速眼动睡眠剥夺.采用Moms水迷宫评估空间记忆.用蛋白质印迹法检测睡眠剥夺后各组大鼠海马PrPC表达的变化.使用原代培养的海马神经元,用RNA干扰技术沉默PrPC,观察神经元轴突延伸的变化.结果 大鼠睡眠剥夺后空间记忆受损,睡眠剥夺组穿越平台次数(3.17±0.95)较笼养对照组(7.17±0.95)和水槽对照组(6.50 ±0.62)明显减少(Z =2.026 6,Z=2.026 6,P＜0.05),平台接近平均值(mm)睡眠剥夺组(711.74 ±33.99)较笼养对照组(592.32±31.31)和水槽对照组(580.86±11.36)明显增大(Z=-2.001 6,Z=-2.482 0,P＜0.05).睡眠剥夺后海马PrPC的表达睡眠剥夺组(0.33±0.10)较笼养对照组(1.01±0.33)和水槽对照组(0.96±0.27)明显下调(Z =2.152 9,Z=2.152 9,P＜0.05).沉默PrPC导致原代培养的海马神经元轴突延伸障碍,感染组神经元(326.28±12.53)与未感染组(555.00±30.43)和感染阴性对照组(558.70±23.10)比较,轴突长度(μm)明显变短(Z =4.768 4,Z=4.877 0,P＜0.05).结论 睡眠剥夺后PrPC介导的海马新生神经元轴突延伸障碍可能是睡眠剥夺后认知障碍发生的潜在机制之一.     

轴突细胞骨架对非中断性轴索损伤的反应及在亚低温治疗后的早期改变

目的 观察轴索损伤早期轴突细胞骨架超微结构的改变和早期亚低温处理后细胞骨架的改变。为亚低温治疗弥漫性轴索损伤（ＤＡＩ）寻找实验依据。方法 实验组豚鼠右侧视神经受牵拉致伤。伤后常温实验组动物体温维持在３６．０￣３７．５℃，低温实验组动物体温降至３２．０￣３２．５℃，两组于伤后２ｈ和４ｈ各处死一半动物。电镜下观察轴突细胞骨架的变化，并用电脑图像分析系统进行定量分析。结果 常温实验组伤后２ｈ，大、中、小     

Multiple functions for the cadherin/catenin complex during neuronal development

The cadherin/catenin complex is a major transmembrane signaling complex through which extracellular signals can influence the cytoskeleton. It is present in neuronal processes during early development (J. Neurosci. 18 (1998) 6892) and appears to play multiple roles during neural circuit formation and maturation (Nat. Neurosci. 7 (2004) 357; Neuron 35 (2002) 77; Nat. Neurosci. 6 (2003) 1169). In previous work (Nat. Neurosci. 6 (2003) 1169), we showed that molecular manipulation of the cadherin/catenin complex has significant effects on the dendritic aborization of cultured hippocampal neurons at 9 days in vitro (d.i.v.). Here we extend these observations by examining the effects of over-expression of beta-catenin (fused to GFP; GFP-beta-cat(*)) or sequestering endogenous beta-catenin [using the intracellular domain of N-cadherin; Ncad(intra)] in cultured hippocampal neurons at different developmental stages. When transfected at 1 d.i.v. and assayed 48 h later, over-expression of GFP-beta-cat(*) increased axonal length and complexity, while sequestering endogenous beta-catenin had the opposite effect. Dendritic aborization was also enhanced by GFP-beta-cat(*) expression throughout early development although the magnitude of this effect decreased as neurons matured from 3 to 12 d.i.v. Finally, at 12 d.i.v., GFP-beta-cat(*) expression increased the density of dendritic spines although not the relative proportion of different subtypes of spines. These results demonstrate that the cadherin/catenin complex plays multiple roles in the development of neuronal morphology and that these roles change as neurons mature.     

The stellate cells of the rat's cerebellar cortex

Summary Stellate cells were studied in rapid Golgi preparations and in electron micrographs. These small neurons can be classified on the basis of their position in the molecular layer and the patterns of their dendritic and axonal arborizations as follows: (1) superficial cells with short, contorted dendrites and a circumscribed axonal arbor (upper third of the molecular layer); (2) deep stellate cells with radiating, twisted dendrites and with long axons giving rise to thin, varicose collaterals (middle third of the molecular layer); (3) deep stellate cells with similar dendrites and long axons giving collaterals to the basket around the Purkinje cell bodies (middle third of the molecular layer). An important characteristic of the stellate cell axon is that it generates most of its collaterals close to its origin. Even in long axon cells, only a few collaterals issue from the more distant parts of the axon. These forms contrast with the basket cell, which sends out long, straighter dendrites, and an extended axon that first emits branches at some distance from its origin. Furthermore, basket cell axon collaterals are usually stout in contrast to the frail, beaded collaterals of the stellate cell axon. The two cell types are considered to be distinct.In electron micrographs stellate cells display folded nuclei and sparse cytoplasm with the characteristics usual for small neurons. Mitochondria are often the most conspicuous organelles because of their size and pleomorphism. The dendrites cannot be followed for long distances in thin sections because of their irregular caliber and course. Axons can be recognized on the basis of their appearance in Golgi preparations as short stretches of slender fibers distended at close intervals and running athwart the grid of the parallel fibers. These distensions, full of ovoid or flattened vesicles, synapse on the shafts of Purkinje cell dendrites and also on the dendrites of Golgi cells, basket cells, and other stellate cells. In all cases the synaptic complex occupies about a third of the junctional interface, the synaptic cleft is somewhat widened, and the pre- and postsynaptic dense plaques are thin and almost symmetrical.Varicosities in the parallel fibers synapse with the soma and dendrites of stellate cells. These junctions display a widened synaptic cleft and asymmetrical pre- and postsynaptic densities. Junctions with climbing fibers (Scheibel collaterals) have also been seen.The form of the stellate cell indicates that it plays a role in cerebellar circuitry different from that of the basket cell, although both cells are inhibitory. It is probably concerned with local effects on Purkinje cell dendrites within the field of its afferent parallel fibers.Supported by U. S. Public Health Service Research Grant NS03659 and Training Grant NS05591 from the National Institute of Neurological Diseases and Stroke.     

The ansa cervicalis and the infrahyoid muscles of the rat

Summary Perikarya of motoneurons and spinal ganglion cells attributed to infrahyoid muscle nerves of the rat were labelled by retrogradely transported horseradish peroxidase (HRP). For the differentiation of motor and sensory axons cross sections of the nerves were stained for acetylcholinesterase. Numbers and diameter distributions of perikarya and myelinated axons were determined.Motoneuronal perikarya innervating the infrahyoid muscles are located from the transition zone brain stem/spinal cord to the segment C 3. They are found mostly in the medial part of the Rexed laminae VII and VIII at the level of C 1 and C 2 and more ventrolaterally in C 3 and are therefore located to a large extent in areas until now not recognized to contain motoneurons. Our results provide evidence for a somatotopic organization of the motoneurons in the upper cervical spinal cord.The diameter distributions of motoneuronal perikarya and axons are in most cases bimodal, the two modes corresponding to -and -motoneurons. In relation to the diameters of their perikarya -axons are significantly thicker than -axons. In contrast to the motoneurons no clear correlation could be established between the sizes of perikarya of spinal ganglion cells and their peripheral processes.This work was partly supported by the Hartmann Müller-Stiftung Zürich     

Cortical and Subcortical White Matter Damage without Wernicke's Encephalopathy after Recovery from Thiamine Deficiency in the Rat

The relative etiologic roles of ethanol and thiamine deficiency in the cortical atrophy and loss of cerebral white matter in chronic alcoholics are uncertain. The present study examined the distribution of degenerating axons within cortical and subcortical tracts 1 week after recovery from early to late symptomatic stages of thiamine deficiency in the absence of ethanol in Sprague-Dawley rats. The brains of rats exposed to an early symptomatic stage of pyrithiamine-induced thiamine deficiency, 12–13 days of treatment, contained degenerating axons in corpus callosum, anterior commissure, external and internal capsules, optic and olfactory tracts, and fomix and mammillothalamic tracts. A dense pattern of degenerating axons was evident in layers Ill-IV of frontal and parietal cortex. Less intense and more evenly distributed degenerating axons were present in layers IV-VI of frontal, parietal, cingulate, temporal, retrosplenial, occipital, and granular insular cortex. Neuronal counts in mamrnillary body nuclei and areal measurements of the mammillary body were unchanged from controls and the thalamus was relatively undamaged. In animals reversed at later and more advanced symptomatic stages of thiamine deficiency, 14–15 days of treatment, degenerating axons were found in other cortical regions and hippocampus and there was extensive neuronal loss and gliosis within mammillary body and medial thalamus. These results demonstrate that a single episode of thiamine deficiency can selectively damage cortical white matter tracts while sparing the thalamus and mammillary body and may be a critical factor responsible for the pathological and behavioral changes observed in alcoholics without Wernicke's encephalopathy.     

Coculture of elongated neuron axon with poly （D, L-lactide-co-glycolide） biomembrane in vitro

Objective: To elongate human nerve axon in culture and search for suitable support matrices for peripheral nervous system transplantation. Methods: Human embryo cortical neuronal cells, seeded on poly (D, L-lactide-co-glycolide) (PLGA) membrane scaffolds, were elongated with a self-made neuro-axon extending device. The growth and morphological changes of neuron axons were observed to measure axolemmal permeability after elongation. Neurofilament protein was stained by immunohistochemical technique. Results: Human embryo neuron axon could be elongated and cultured on the PLGA membrane and retain their normal form and function. Conclusions: Three dimensional scaffolds with elongated neuron axon have the basic characteristics of artificial nerves, indicating a fundemental theory of nerve repair with elongated neuron axon.