Characterization and Function of Spinal Excitatory Interneurons with Commissural Projections in Xenopus laevis embryos

The multipolar somata of dorsolateral commissural (dlc) interneurons (Roberts and Clarke, 1982) lie in a superficial dorsolateral position in the spinal cord of Xenopus laevis embryos. By applying horseradish peroxidase to one-half of the 100 microm diameter spinal cord, these neurons have been backfilled. Their dendritic branching pattern, commissural axonal projection and distribution near the time of hatching is described. Using Lucifer yellow-filled microelectrodes a population of sensory interneurons with dlc morphology has been identified. They have multipolar somata in a dorsolateral superficial position, obliquely projecting dendrites and a ventral commissural axon. They receive presumed monosynaptic excitation in response to electrical stimulation of sensory neurites in the skin on the same side as the soma. During fictive swimming activity in curarized embryos the dlc interneurons are rhythmically inhibited in time with ventral root discharge on the same side. Dlc interneurons can fire multiple impulses and can turn on fictive swimming when stimulated by intracellular current injection. Skin stimulation is followed by excitatory postsynaptic potentials (EPSPs) in contralateral ventral rhythmic neurons. These EPSPs are reduced by the application of NMDA receptor antagonist. We conclude that dlc interneurons are excited by primary skin afferent Rohon - Beard neurons, carry sensory information across the spinal cord to excite neurons on the opposite side by release of an excitatory amino acid transmitter and participate in reflexes and in the initiation of swimming.     

Comparison of Effects of Various Types of NA and 5-HT Agonists on Transmission from Group II Muscle Afferents in the Cat

A number of noradrenaline and serotonin agonists were tested to investigate which of them replicate the depressive actions of monoamines on transmission from group II muscle afferents in the cat spinal cord. The agonists were applied ionophoretically at the two sites at which maximal monosynaptic focal field potentials are evoked from group II afferents-in the intermediate zone and the dorsal horn of the 4th and 5th lumbar segments. Their effects were estimated from changes in the amplitude of the field potentials. The compounds tested fell into three categories according to the site at which they depressed transmission from group II afferents: one category with highly selective actions in the intermediate zone, a second category with similarly selective actions in the dorsal horn, and a third category with non-selective actions. Drugs in the first category included three noradrenaline agonists (tizanidine, B-HT 933 and clonidine), included in the second were five serotonin agonists (8-OH-DPAT, 5-methoxytryptamine, alpha-methyl serotonin, DOI and 2-methyl-serotonin), and in the third two noradrenaline agonists (phenylephrine and isoproterenol) and two serotonin agonists (RU 24969 and 5-carboxamidotryptamine). Field potentials evoked by group I afferents remained unaffected by all but one compound (8-OH-DPAT). Effects of one noradrenaline agonist and one serotonin agonist (tizanidine and 5-methoxytryptamine) were also tested on responses of single extracellularly recorded neurons. Tizanidine depressed responses induced by stimulation of group II afferents in intermediate zone interneurons, but not in dorsal horn neurons, while 5-methoxytryptamine depressed activation of the latter. Tizanidine had no effect on responses evoked by group I afferents, either in intermediate zone interneurons or in the dorsal spino-cerebellar tract neurons of Clarke's column. It is hypothesized that noradrenaline and serotonin released by descending monoaminergic neurons differ in the potency with which they depress transmission from group II afferents to different functional types of neuron. The results suggest that this depression may involve different membrane receptors at different locations, primarily alpha2 adrenoceptors in the intermediate zone/ventral horn and 5-HT1A serotonin receptors in the dorsal horn.     

大网膜移植抑制大鼠脊髓损伤后神经细胞凋亡的实验研究

目的 探讨脊髓损伤（SCI)后神经细胞凋亡的发生机制和伤后立即行大网膜脊髓移植是否对神经细胞凋亡具有抑制作用。方法 制作程控电磁吸铁棒下落打击脊髓损伤模型,运用末端脱氧核苷酸转移酶介导生物素标记（TUNEL）方法检测细胞凋亡,分别观察SCI后1d、2d、7d组与伤后即刻施行大网膜移植组（存活7d）的细胞凋亡。结果 脊髓灰质区在伤后1d、、2d时TUNEL阳性细胞数最多;脊髓白质区在伤后1d时TUNEL阳性细胞数最多,伤后7d出现第2次高峰;伤后大网膜脊髓移植的TUNEL阳性细胞数较7d明显降低。结论 SCI后白质区和灰质区存在不同演变过程的神经细胞凋亡,SCI后即刻大网膜脊髓移植对细胞凋亡有抑制作用。     

脊髓损伤对大鼠骨细胞凋亡的影响

目的：探讨脊髓损伤（SCI）对骨细胞凋亡的影响及其在SCI后骨质疏松发病中的可能机制,方法：20只3mo龄SD大鼠均分为SCI组与对照组,SCI组于T10 处完全横断脊髓,对照组仅行椎板切除术,3wk后对骨骨进行取材料,应用原位凋亡法计数股骨髁部松质骨骨细胞的凋亡指数,对股骨髁部行透射电镜观察,采用双能线骨密度仪对各组大鼠的股骨髁部骨密度（BMD）进行测定,结果：SCI组BMD较对照组明显降低（P＜0．05）,小梁骨中骨细胞凋亡比率显上升（P＜0．001）,透射电镜观察到SCI组骨细胞异梁色质凝聚,边集等典型的细胞凋亡征象,结论：骨细胞凋亡在SCI后骨质疏松发病中起着重要作用。     

葛根素对兔脊髓缺血再灌注损伤的保护作用

目的：研究葛根素对兔脊髓缺血再灌注损伤的作用。方法：20只雄性新西兰大白兔随机分成缺血组（A组,n=10）及葛根素组（B组,n=10),夹闭腹主动脉肾下段20min,建立兔脊髓腰尾段血模型,B组于夹闭前10min静脉注射葛根素30mg.kg^-1,A组则静脉注射生理盐水,测定夹闭前、后及再灌注后血浆中丙二醛（MDA）浓度及超氧化物歧化酶（SOD)活性,再灌注4,8,12,24及48h分别对动物后肢运动功能评分;再灌注48h后,处死动物,制作切片,观察其组织病理变化。结果缺血及再灌注后B组MDA值明显低于A组（P＜0．05）,而OD活性明显高于A组（P＜0．05）;再灌注后4,8,12,24及48h时的神经功能评分B组明显高于A组（P＜0．05）;光镜下,与A组相比,B组脊髓组织损伤显著减轻,形态基本正常的前角细胞较多。结论葛根素对兔脊髓缺血再灌注损伤有显著的保护作用。     

脊髓损伤的MRI诊断

目的:探讨脊髓损伤的MRI表现。方法：收集脊髓损伤患者90例,其中男68例,女22例,平均年龄35岁。应用GE Signa contour 0.5T(40例）和SIEMENS Open 0.2T（50例）磁共振机,脊柱表面线圈,自旋回波序列做轴位和矢状位T1WI、T2WI扫描,其中10例加作冠状线圈。结果：90例患者共发现各种脊髓损伤106例次,其中脊髓完全、不完全性横断14例次（占13.2％）,水肿11例次（10.4％）,挫伤、出血27例次（25.5％）,受压、扭曲27例次（25.5％）,软化16例次（15.1％）,萎缩11例次（10.4％）。结论：MRI表现能反映脊髓损伤的形态和病理改变,是评价脊髓损伤的好方法,不仅可以指导治疗方案的选择,还有助于判断预后。     

哑铃形椎管肿瘤29例临床分析

回顾性分析我院从 1 990年 3月～ 1 998年 1 1月 2 9例哑铃形椎管肿瘤的诊治。所有病例经CT ,MRI确诊。MRI能提供多时向、多空间图像 ,故可视为诊断哑铃形椎管肿瘤最有价值的方法。除 2例拒绝手术治疗外 ,2 7例采用后正中或后外侧入路作Ⅰ期显微手术切除 ,疗效较满意。本文重点讨论了该肿瘤的临床表现特征 ,CT ,MRI检查和手术治疗的特点     

颈髓段下行传导束诱发电位动物模型研究

目的 :建立 SD鼠脊髓下行传导束诱发电位 ( MEP)模型。 方法 :刺激颈髓段下行传导束 ,于双侧坐骨神经记录电位变化。采用 8个不同刺激强度区间 ,并结合脊髓部分损伤状态 ,评价其潜伏期和波幅的变化。结果 :诱发电位主要由 3个正负波峰组成。 N1的潜伏期 :右侧 ( 2 .89± 0 .2 2 ) ms,左侧 ( 2 .89± 0 .2 4) ms。传导速度 47.9m/s。 N1的波幅 :右侧 ( 3 .61± 2 .10 )μV,左侧 ( 3 .83± 2 .3 2 )μV。不同刺激强度组间潜伏期相差不显著 ,但组间波幅有显著性差异 (右侧 F =2 .2 2 ,df =72 0 1,P=0 .0 3 ;左侧 F =2 .11,df=72 0 6,P=0 .0 4)。 T9平面脊髓部分损伤后 ,潜伏期延长 ,右侧 14 % ,左侧 12 % ;波幅下降 ,右侧5 9 % ,左侧 3 1%。结论 :建立的颈髓段下行传导束诱发电位动物模型有效、可靠 ,重复性好。用此模型可准确地检测脊髓传导束的功能状态     

胶质源性神经营养因子对脊髓损伤后前角运动神经元的保护作用

目的 :探讨胶质细胞源性神经营养因子 (GDNF)对脊髓损伤后运动神经元的保护作用。 方法 :大鼠分为假手术组、生理盐水 (NS)组和 GDNF组 ,改良 Allen法撞击致伤 T1 2 脊髓 ,蛛网膜下腔分别给予 NS和 GDNF,分别取不同时间的伤段脊髓进行切片 ,应用酶组织化学染色方法显示脊髓前角外侧核运动神经元中胆碱酯酶 (Ch E)和酸性磷酸酶 (ACP)活性 ,并结合计算机进行图像分析。结果 :GDNF组较 NS组 Ch E活性显著增加 ,ACP活性显著降低 ;2 1d时 NS组的 ACP及 Ch E活性均高于及低于假手术组 ;GDNF组与假手术组 Ch E和 ACP活性差别不显著。 结论 :GDNF对脊髓损伤后的前角外侧核运动神经元有一定的保护作用