Role of the cell recognition molecule, cognin, in GABAergic differentiation in chick retina

Previous work showed that GABAergic differentiation in developing chick retina depends on insulin and cell interactions. Here, we investigated whether it depended on cell signaling mediated by retina cognin, a 50 kDa cell recognition molecule. Cognin mediates cell adhesion in vitro and occurs on retinal neurons that become both GABAergic and cholinergic. We investigated two markers of GABAergic differentiation: glutamate decarboxylase (GAD) activity and high-affinity GABA uptake. Both increase during differentiation of retinal neurons in culture and can be easily measured. We blocked cognin-mediated cell signaling with cognin antibody and found a reduction of the developmental increase in GAD activity in cultures of retinal neurons from 7 and 11 day chick embryos. There was no reduction of high-affinity GABA uptake. This suggested that cognin-mediated signaling was necessary for the normal developmental increase in GAD but not for high-affinity GABA uptake. These results contrasted with our previous observations on cholinergic differentiation in cultured retinal neurons. We found that cognin antibody blocked the normal developmental increase in choline acetyltransferase (ChAT) only if the cells were exposed before embryonic day 7. Thus, while both GAD and ChAT activity appear to be controlled by cell signaling involving cognin, the periods of developmental sensitivity for the two differentiation markers are different. Antibodies to other adhesion molecules, Ng-CAM, and N-cadherin, did not similarly affect GAD activity. Antibodies to laminin at a 10-fold higher concentration inhibited GAD activity only in early embryonic retina. Tests for protein synthesis and “housekeeping” enzyme activity demonstrated that the cognin antibody effect was selective for neuronal differentiation pathways. Thus, GABAergic differentiation in developing retina is sensitive to cell signaling mediated in part by cognin.     

Identification and potential role of PSD-95 in Schwann cells

Postsynaptic density-95 (PSD-95) is one of neuronal nitric oxide synthase (nNOS)-anchoring proteins and plays an important role in specifying the sites of reaction of nitric oxide (NO) in the nervous system. The present study aims to investigate the presence of PSD-95 in rat Schwann cells (SCs) and the association of PSD-95 and nNOS with serum-induced SCs proliferation. The expression of both molecules downregulated significantly after 48 h of serum deprivation, and increased gradually to the peak at 12 h, ultimately returned to the control level at 48 h after serum stimulation. The association of PSD-95 with nNOS was observed in Ki67 and BrdU-positive SCs. The selective nNOS inhibitor arrested the cell cycle progress and decreased the proliferating cell nuclear antigen (PCNA) levels. These findings suggested that PSD-95 and nNOS may collectively participate in the proliferation of SCs, providing further evidence for the role of NO during peripheral nerve regeneration.     

星形胶质细胞与Aβ1-40诱导凋亡的PC12细胞共育条件培养液对神经干细胞分化的影响机制

目的 将星形胶质细胞与β-淀粉样蛋白(Aβ1-40)诱导凋亡的PCI2细胞共育,观察星形胶质细胞条件培养液(ACM)对胚胎大鼠皮层神经干细胞(NSCs)体外定向分化为神经元的比例影响及机制,探讨神经营养素家族蛋白[包括脑源性神经营养因子(BDNF)、神经生长因子(NGF)、神经营养素-3(NT-3)]是否参与此过程. 方法 PC12细胞分别经10 μg/mLAβ1-40诱导不同时间(0、4、6、12、24h)后分为两部分,第一部分应用流式细胞技术检测不同时间点PC12细胞凋亡率;第二部分分别与星形胶质细胞共育2 d,将收集的ACM分为两部分.一部分应用ELISA法检测ACM中BDNF、NGF、NT-3蛋白含量,另一部分以1;3比例同DMEM/F12堵养基混合,对NSCs进行体外诱导分化,应用激光共聚焦显微镜、NSE免疫荧光技术鉴定和计数神经元分化比例. 结果 在Aβ1-40作用6 h时间点,PC12细胞凋亡率达高峰,与其共育的ACM中BDNF蛋白总量明显增高,诱导的NSCs神经元分化比例明显升高,与其他组比较,差异均有统计学意义(P<0.05). 结论 星形胶质细胞与Aβ1-40诱导凋亡的PCI2细胞共育后.ACM提高了NSCs向神经元的分化比例,ACM中BDNF可能参与了这一过程.     

Influence of Scalp Point-through-point Acupuncture on 200 kDa Neurofilament Protein in Rats with Acute Cerebral Infarction

目的研究头穴透刺对急性脑梗死大鼠神经丝蛋白-200(NF-200)的影响,探讨针刺对脑梗死大鼠神经可塑性影响的机制.方法将健康雄性Wistar大鼠随机分为假手术组(A组)、模型组(B组)、针刺组(C组).通过建立大鼠局灶性脑缺血模型(MCAO),用逆转录-聚合酶链反应(RT-PCR)法,测定以上各组在7 d、14 d、28 d不同时间点NF200 mRNA变化情况.结果头穴透刺组脑组织NF-200的表达与假手术组、造模组相比差异有统计学意义(P＜0.05);而在不同时间窗内头穴透刺组,模型组与假手术组比较差异有统计学意义(P＜0.01).表明头穴透刺可以促进脑组织神经丝蛋白-200的表达.结论头穴透刺能够提高脑缺血后神经功能,促进肢体功能恢复,增加神经丝蛋白-200的表达,发挥对脑组织神经细胞可塑性的调节作用.     

帕金森病内侧苍白球和丘脑腹外侧核神经细胞放电特点与临床症状的关系

目的：探讨帕金森病（PD）患者内侧苍白球（GPi）和丘脑腹外侧核团（Vop／Vim）细胞电活动与PD症状的关系。方法：24例患者在接受手术的同时采集细胞电活动（GPi：12个,Vop／Vim：12个）和记录肢体肌电图（EMG）。应用单细胞分析,峰阃隔（ISI）、ISI变异系数（CV）和ISI直方图等方法进行分析。用统一帕金森评分量表（UPDRS）进行疗效评估。结果：199个GPi神经元中,33个（16．6％）为与震颤相关放电活动,136个（68．3％）为紧张性放电活动,30个（15．1％）为不规则放电活动。223个Vop／Vim神经元中,110个（49．3％）为与震颤相关的放电活动,49个（22％）为紧张性放电活动,64个（28．7％）为不规则放电活动。ISI分析发现GPi神经元放电频率为78Hz（n=92）而Vop／Vim为24Hz（n=107）。方差分析显示GPi和Vop／Vim的上述三种不同放电模式神经元的数量之间比较差异有统计学意义（P〈0．05）。UPDRS显示,术后GPi对震颤、僵直和运动迟缓的疗效分别为63％、83％和64％;而Vop／Vim术后对震颤、僵直和运动迟缓的疗效分别为94％、66％和49％,提示GPi对僵直改善明显,而Vim对震颤改善显著（P〈0．05）。结论：GPi和Vop／Vim中不同放电模式的神经元可能与PD运动症状有内在联系,支持PD病理生理模型。     

依达拉奉对惊厥持续状态大鼠海马IRE1 mRNA表达及神经元凋亡的影响

目的：探讨依达拉奉（EDA）对惊厥持续状态（SC）后大鼠海马内质网应激关键标志分子IRE1表达及神经元凋亡的影响。方法：将19~21 d日龄的Sprague-Dawley大鼠随机分为SC组、EDA组、对照组。其中SC组、EDA组再按SC后处死时间点不同分别分为4,12,24,48,72 h 5个亚组;每组均8只。用RT-PCR检测SC后海马IRE1 mRNA的表达。用原位细胞凋亡检测法（TUNEL）观察神经元凋亡细胞数。电镜观察海马CA1区神经元超微结构变化。结果：①RT-PCR 结果：SC组4 h和12 h时间点IRE1 mRNA含量较对照组明显升高,差异有非常显著性（P<0.01）;EDA组4,12,24 h时间点IRE1 mRNA含量显著高于SC组对应时间点及对照组的含量,差异有非常显著性（P<0.01）。②TUNEL结果：SC组12~72 h时间点TUNEL阳性细胞数多于对照组,差异有显著性（P<0.01）,且SC组TUNEL阳性细胞数随惊厥持续时间延长而增加。EDA组12~72 h时间点TUNEL阳性细胞数较SC组明显减少,差异有显著性（P<0.05或P<0.01）,但仍高于对照组,差异有显著性（P<0.05或P<0.01）。③ 电镜观察结果：SC组及EDA组4 h后即开始出现核周细胞器的改变,12 h后出现明显细胞核的改变。其中SC组细胞凋亡严重,EDA组凋亡较轻。结论：EDA可能通过上调IRE1的表达及维持其活性而缓解内质网压力而发挥对神经元的保护作用,有望成为在体抑制内质网应激的有效药物。 ［中国当代儿科杂志,2009,11（6）：471-475］     

W-7对惊厥持续状态幼鼠海马GRP78表达及神经元凋亡的影响

目的：探讨钙调蛋白抑制剂W-7 对幼年大鼠惊厥持续状态（SC）后 GRP78 表达及神经元凋亡的影响。方法：将19～21日龄Sprague-Dawley大鼠117只随机分为生理盐水对照（NS）组、惊厥持续状态（SC）组、W-7 预处理（W-7）组;各组再按不同时间点分4 h、24 h、48 h 3个亚组（n=13）。应用氯化锂 匹鲁卡品建立大鼠SC模型,W-7组在制模前15 min予尾静脉注射W-7。逆转录-聚合酶链反应（RT-PCR）和免疫组织化学法检测每组各时间点大鼠海马GRP78 RNA 和蛋白的表达情况;原位末端标记法（TUNEL）检测海马CA1区的神经元凋亡情况。结果：SC组幼年大鼠海马24 h GRP78 mRNA 的表达量较 NS 组显著升高（P<0.01）,SC组24 h和48 h GRP78 蛋白表达量较NS 组相应时间点也显著升高（P<0.01）;W-7组24 h和48 h的GRP78 mRNA及蛋白表达量较SC和NS组明显升高（P<0.05或P<0.01）;SC组在24 h 、48 h海马CA1区TUNEL阳性细胞数（21.0±2.5,29.4±2.8）显著高于NS组（7.1±1.4,7.3±1.6;P<0.01）;W-7组在24 h、48 h海马 CA1 区 TUNEL 阳性细胞数（15.0±2.5,20.0±2.9）较SC组显著降低（P<0.01）,但仍显著高于 NS 组（P<0.01）。结论：钙调蛋白抑制剂 W-7 可通过上调 GRP78 的表达,减轻神经元凋亡, 具有脑保护作用。     

灵芝孢子对大鼠脊神经腹根切断后脊髓运动神经元存活及其NT-3、NOS表达的影响

目的探讨灵芝孢子（萌动激活赤灵芝孢子）对大鼠脊髓受损伤运动神经元存活和表达神经营养素-3（NT-3）及一氧化氮合酶（NOS）的影响.方法对单侧腹根切断后的大鼠胃饲不同剂量的灵芝孢子,计算受损伤运动神经元存活率;用免疫组织化学及原位杂交方法检测NT-3的表达;用酶组织化学方法检测NOS的活性.结果腹根切断后35 d,对照组运动神经元存活率为47.32%,灵芝孢子低、中、高剂量组的运动神经元存活率分别为67.11%、72.67%和81.67%;腹根切断后高剂量组存活的运动神经元NT-3和NOS的表达都高于对照组. 结论灵芝孢子促进大鼠脊髓前角受损伤的运动神经元存活,其存活率与用药剂量有关;灵芝孢子促进大鼠脊髓存活的运动神经元表达NT-3和NOS.     

Contextual modulation of synchronization to random dots in the cat visual cortex

Synchronization of neuronal activity has been proposed as a binding mechanism for integration of image properties into one coherent percept. In the present study, we investigated the contextual modulation of synchronization to random dot patterns. Coherent motion of random dots evoked well synchronized responses in area 17 of anaesthetized cats when the stimulus was presented in the compound receptive field of recorded sites. Gradually changing the directional coherence of random dots in the surround while maintaining fully coherent motion of the stimulus in the receptive field significantly suppressed synchronization of neuronal activity for some stimulus conditions. However, usually one or two peaks of increased synchronization were found in the surround coherence tuning curves with low (8–12%) and/or moderate (25–50%) coherence in the surround. At the population level, synchronization was significantly depressed with incoherent motion in the receptive field and when both the surround and the receptive field were jointly stimulated with 0% coherence. The intriguing finding was the discovery of two distinct groups of cells with opposite synchronization changes dependent on the presence or absence of significant synchronization in their spontaneous activity. The latter group of neurons showed peaks of increased synchronization with lower surround coherence, thus probably being more sensitive to the direction of the surround motion. Overall, our findings support the notion that binding of stimulus properties can be achieved by synchronized activity of cortical cells. However, our findings go further than the original hypothesis of feature binding by synchrony to show that synchronization of cortical activity may be directly related to the decision making processes, which in turn are related to the threshold of perception of coherent motion.