轴突损伤距离对成年金黄地鼠视网膜节细胞轴突在正常或预先溃变周围神经移

目的 系统研究轴突损伤的距离与轴突再生之间的关系,以及预先溃变周围神经移植物对视网膜节细胞（简称节细胞）轴突在不同距离损伤后再生的影响。方法 在距成年金黄地鼠眼球后极０．５、１．５、２、３或７ｍｍ处切断左侧视神经,视神经眶侧断端同正常（正常组）或预先溃变（溃变组）的周围神经移植物吻合。结果 移植术后２８ｄ,两组荧光金逆行标记的发出再生轴突的节细胞数量均随轴突损伤距离的增加而下降,并以０．５～３ｍｍ距离点之间下降最为明显。比较两组对应距离点,溃变组标记节细胞数量在２、３ｍｍ距离点较正常组显著增多。结论 成年金黄地鼠节细胞轴突损伤的距离,决定了发生再生轴突的节细胞数量。预先溃变周围神经移植物对节细胞轴突再生具有促进作用,并以轴突损伤距离为条件。     

轴突损伤距离对成年金黄地鼠视网膜节细胞轴突在正常或预先溃变周围神经移植物中再生的影响

目的　系统研究轴突损伤的距离与轴突再生之间的关系 ,以及预先溃变周围神经移植物对视网膜节细胞 (简称节细胞 )轴突在不同距离损伤后再生的影响。　方法　在距成年金黄地鼠眼球后极 0 .5、1、1.5、2、3或7m m处切断左侧视神经 ,视神经眶侧断端同正常 (正常组 )或预先溃变 (溃变组 )的周围神经移植物相吻合。　结果　移植术后 2 8d,两组荧光金逆行标记的发出再生轴突的节细胞数量均随轴突损伤距离的增加而下降 ,并以 0 .5～3m m距离点之间下降最为明显。比较两组对应距离点 ,溃变组标记节细胞数量在 2、3mm距离点较正常组显著增多。　结论　成年金黄地鼠节细胞轴突损伤的距离 ,决定了发出再生轴突的节细胞数量。预先溃变周围神经移植物对节细胞轴突再生具有促进作用 ,并以轴突损伤距离为条件。     

新生犊牛视网膜节细胞的形态分布

目的:研究比较新生犊牛视网膜节细胞(RGCs)的数量、大小和密度的形态学变化。方法:采用Nissl染色、荧光染料DiI逆行标记技术和计算机图像处理方法。结果:RGCs在视神经乳头下方形成一个沿鼻颞侧轴方向伸展的高密度区(P1,2608/mm2;P21,2174/mm2),即视条纹。由视条纹至周边部细胞密度递减,颞侧周边部最低(P1,mm2;P21,217/mm2);细胞大小则呈递增的变化,这种变化趋势在颞侧最明显。由P1到P21,RGCs总数和平均细胞密度均递减而细胞大小递增。结论:RGCs大小由视条纹至周边部递增而细胞密度递减,并且由P1到P21,RGCs总数和细胞大小递增而细胞密度递减。     

小鼠脊髓损伤后Nogo-A的免疫组织化学研究

目的研究小鼠脊髓损伤后Nogo-A的表达情况。方法 C57小鼠分为脊髓损伤组、假手术组和正常对照组,每组均在损伤后不同时间点（损伤后1 h,12 h,24 h）取材,然后行Nogo-A免疫组织化学染色。结果 Nogo-A明显表达于神经元胞体及其突起形成的神经纤维。随着损伤后存活时间的延长,Nogo-A阳性细胞数量和免疫反应强度均逐渐升高。结论脊髓损伤后24 h内Nogo-A在神经元的表达逐渐升高,导致神经再生困难。     

大鼠胚胎视网膜节细胞神经诱向因子及其受体的免疫组织化学定位及原位定量研究

用视网膜节细胞神经诱向因子(RGNTF)单克隆抗体及RGNTF抗独特型单克隆抗体对大鼠胚胎16～18d眼球切片进行了免疫组织化学定位及定量研究。结果表明,鼠胚视网膜节细胞的RGNTF含量从胚16～20d非常显著地减少(P<0.01),RGNTF受体的数量从胚16d到18d显著增加(P<0.05),从胚18d到20d又非常显著减少(P<0.01)。以上提示,16～18d的鼠胚视网膜节细胞既含大量RGNTF,又有大量RGNTF的受体,RGNTF对胚胎视网膜节细胞的存活及分化可能有自调节功能。20d的鼠胚视网膜节细胞的RGNTF及其受体都非常显著减少,提示节细胞在形态上分化完成后,其对RGNTF的自分泌立即显著降低,这可能是节细胞自然死亡的主要原因。     

哺乳动物视网膜节细胞中神经营养因子的主要生物学作用

哺乳动物视网膜节细胞的存活和再生受许多神经营养因子的调节。本文综述了神经营养素家族、细胞因子家族及玻璃体内移植外周神经节段等因素促进视网膜节细胞存活的作用 ;同时也分析了它们对视网膜节细胞的轴突生长和再生的影响 ,并提出这些神经营养因子可能通过升高cAMP水平起作用。     

钠尿肽受体A在小鼠视网膜发育过程中的表达

目的检测钠尿肽受体(NPR)在不同年龄小鼠视网膜内的表达,探讨其在视网膜发育过程中的作用。方法收集从受孕16日(E16)到出生90日(P90)小鼠眼球标本共127只,对NPR-A进行免疫荧光检测。结果NPR-A广泛存在于视网膜神经元中,例如,在外核层,NPR-A于P7开始高表达在视锥、视杆细胞内、外突起上,于P14减弱,P30之后持续稳定弱表达;在内核层,从P7开始NPR-A持续弱表达在双极细胞的突起中,而在水平细胞中未见NPR-A表达;在神经节细胞层,NPR-A于E16开始高表达在神经节细胞胞体中,P14明显减弱,而在神经纤维层,即神经节细胞的轴突中,NPR-A从胚胎期至成年持续高表达;在外网状层和内网状层,NPR-A于P14均高表达,但于P30之后逐渐减弱。此外,NPR-A还广泛的存在于Müller细胞的突起中。结论 NPR-A参与了视网膜的发育,可能是小鼠视网膜神经元发育过程中的关键分子,并对Müller细胞的功能活动起着重要的调节作用。     

神经元Nogo-A的表达与其髓鞘化关系的研究

目的探讨神经元表达Nogo鄄A蛋白的情况,对Nogo鄄A的功能作初步了解。方法采用免疫组织化学方法,观察神经元表达Nogo鄄A的情况,并设置对照组。结果成年大鼠脊髓内神经元和背根神经节的大﹑中﹑小细胞中都出现Nogo鄄A阳性免疫反应,在胞浆和胞核中表达。结论大鼠神经组织中神经元都可能有Nogo鄄A的表达,表明神经元表达Nogo鄄A与该神经元轴突的髓鞘化没有联系,提示神经元中的Nogo鄄A的功能可能不参与髓鞘形成。     

Behavioral correlates of focal hippocampal X-irradiation in rats II

Summary The summing properties of the surround response mechanism of cat retinal ganglion cells were assessed by determining area-sensitivity and area-adaptation curves. The two curves were found to be similar for X and Y cells but for many Y cells adaptive sensitivity was found to be dependent upon the size of the test target. These results suggest that, for X cells, the retinal area over which the surround integrates signals and adaptation are spatially coextensive. Most Y cells appear to pool adaptive effects over a smaller region than they pool signals.Supported by NEI grant No. EY 00701     

Response of X and Y cat retinal ganglion cells to moving stimuli

Summary Single optic tract fibers in the cat were classified as X or Y cells by a contrast reversal stimulus. A slit of light was then moved across the receptive field at velocities from 10–1000 ° /s. The preferred velocity was that velocity which elicited the strongest response from the cell. The maximum velocity was the highest velocity target to which a cell could respond. Y cells as a group both preferred and could follow faster targets than X cells, and were more broadly tuned to the preferred velocity.This study was supported by Public Health Service Grant EY 00701 and NEI Grant EY 00376     

Metallothionein-IIA promotes neurite growth via the megalin receptor

Metallothionein (MT)-I/II has been shown to be neuroprotective and neuroregenerative in a model of rat cortical brain injury. Here we examine expression patterns of MT-I/II and its putative receptor megalin in rat retina. At neonatal stages, MT-I/II was present in retinal ganglion cells (RGCs) but not glial or amacrine cells; megalin was present throughout the retina. Whilst MT-I/II was absent from adult RGC in normal animals and after optic nerve transection, the constitutive megalin expression in RGCs was lost following optic nerve transection. In vitro MT-IIA treatment stimulated neuritic growth: more RGCs grew neurites longer than 25 μm (P < 0.05) in dissociated retinal cultures and neurite extension increased in retinal explants (P < 0.05). MT-IIA treatment of mixed retinal cultures increased megalin expression in RGCs, and pre-treating cells with anti-megalin antibodies prevented MT-IIA-stimulated neurite extension. Our results indicate that MT-IIA stimulates neurite outgrowth in RGCs and may do so via the megalin receptor; we propose that neurite extension is triggered via signal transduction pathways activated by the NPxY motifs of megalin’s cytoplasmic tail.     

远志皂苷元对氧化应激损伤的视网膜神经节细胞的保护作用

目的:观察远志皂苷元(senegenin,Sen)对氧化应激损伤的视网膜神经节细胞(retinalganglioncells,RGCs)的影响并初步探讨其作用机制。方法:采用上丘荧光金逆行标记RGCs后,体外原代RGCs混合细胞培养,随机分为control组、H2O2组、Sen+H2O2和Sen组。检测带荧光金荧光细胞的活力。同上述分组处理视网膜,用Hoechst33258染色后观察视网膜细胞核形态的变化,Westernblotting检测视网膜细胞cleavedcaspase-3、细胞色素C及Bcl-2蛋白的表达。结果:与control组比较,Sen浓度在10、20和40μmol/L时,RGCs活力无明显变化(P>0.05),但Sen浓度达到80和160μmol/L时,RGCs活力明显下降,差异显著(P<0.01)。25、50、100和200μmol/LH2O2明显降低RGCs活力(P<0.05)。Sen浓度在10、20和40μmol/L时,对50μmol/LH2O2损伤的RGCs有较好的保护作用(P<0.05),其中40μmol/LSen保护作用最为明显。Hoechst33258染色表明Sen可以减少H2O2引起的视网膜细胞凋亡。Westernblotting结果表明Sen促进Bcl-2蛋白的表达,降低线粒体细胞色素C的释放,下调cleavedcaspase-3的表达。结论:Sen保护RGCs对抗氧化应激引起的损伤,其机制可能与其增强Bcl-2蛋白表达和减少氧化应激引起的细胞凋亡有关。     

Maintained activity of cells in the tree shrew's optic tract

Summary The maintained activity of different types of ganglion cells in the tree shrew's retina has been investigated in darkness and different adaptation luminances, with particular reference to on-centre sustained and transient cells.The firing rate of on-centre sustained cells rises with increasing luminance up to 5.10^–2 W/m² (human photopic equivalent 5.10⁴ cd/m²) whereas, for on-centre transient cells no simple relationship between luminance and activity could be found.The ratio of mean and standard deviation (regularity) of the interval length of sustained cells increases with light intensity, while in most transient cells a constant ratio is observed.Various kinds of interval histograms are observed for sustained units: exponential, gamma, bimodal and other types. Transient cells tend to fire in bursts with correspondent bimodal interval histograms.The first order serial correlation coefficient is positive for the majority of sustained cells and negative for most transient cells.It is argued that the final statistical properties of the maintained activity of retinal ganglion cells are mainly determined by the retinal circuitry between photoreceptors and ganglion cells.Now at the Institute of Pharmacology, University of NijmegenNow at the Institute of Neurology, University of Nijmegen     

The retinal input to cells in area 17 of the cat's cortex

Summary The activity of retinal ganglion cells and cortical cells with overlapping receptive fields was simultaneously recorded. The responses to moving stimuli of individual simple cortical cells could be accounted for on the basis of the cell receiving either on-centre or off-centre afferents; instances in which it was necessary to postulate a mixed on- and off-centre input were not found. In six instances cross correlograms of ganglion cell and cortical cell activity showed that the ganglion cell was afferent, via a relay cell in the LGN, to the cortical neurone. The receptive fields of such pairs were almost completely overlapping and concentric. In three cases a sustained ganglion cell projected to a simple cortical cell. In one case a transient ganglion cell projected to a simple cell, and in one case a sustained and a transient ganglion cell projected to the same simple cell.On leave from the Department of Physiology, John Curtin School of Medical Research, Australian National University, P.O. B. 334, Canberra City ACT 2601, Australia     

rd1小鼠视网膜退变中期节细胞功能的变化

目的:探讨视网膜色素变性模型rd1小鼠视网膜退变中期各类视网膜节细胞(retinalganglioncells,RGCs)功能的变化情况。方法:运用多电极阵列(multi-electrodearrays,MEA)记录方法,记录视网膜退变中期(出生后20d,P20)的rd1小鼠或正常对照小鼠视网膜中多个节细胞动作电位的发放,并比较自发发放和光反应特征等指标,评价幸存的节细胞功能变化。另外,采用免疫组化染色方法验证视网膜感光细胞的退化情况。结果:免疫组化的结果表明rd1小鼠视网膜感光层的厚度显著低于正常小鼠。根据节细胞光反应特性的不同,可以将其分成6类:ONsustained、ONtransient、ON-OFFsustained、ON-OFFtransient、OFFsustained和OFFtransientRGCs,但OFFsustainedRGCs所占比重极小(1.0%~3.1%)。rd1小鼠视网膜中保持光反应的节细胞比例显著低于正常小鼠。rd1小鼠节细胞的自发发放显著高于正常小鼠,而不同类型的节细胞变化情况有所不同。rd1小鼠视网膜各类节细胞的光反应强度及光敏感度均显著低于正常小鼠。结论:在rd1小鼠退变的中期,视网膜感光层明显退变;rd1小鼠退变中期的视网膜节细胞发生明显的功能退变,而且不同类型的节细胞变化情况有所不同。     

Classification of cat retinal ganglion cells into X- and Y-cells with a contrast reversal stimulus

Summary A contrast reversal (alternating phase) stimulus was used to study the responses of 150 retinal ganglion cells from 15 adult cats. Because the majority of the cells did not show perfect linear spatial summation, a ratio of the firing rates at two time periods was used to express the degree of nonlinearity. Y-cells showed a high degree of nonlinearity, and their mean null ratio was significantly lower than that of X-cells. With the stimulus at the null position, X-cells had an unmodulated discharge rate which was significantly higher than maintained activity, while the firing rate of Y-cells was lower than maintained activity. With the stimulus placed at an eccentric position in the receptive field, X-cells responded in a sustained manner, while Y-cells respond transiently. Because of these observations, we conclude that X-cells correspond to the sustained cells, while Y-cells correspond to the transient cells.     

Adaptation and dynamics in X-cells and Y-cells of the cat retina

Summary On the basis of the spatial summation properties of their receptive fields, cat retinal ganglion cells were classified as either X-cells (linear) or Y-cells (non-linear). Responses were then obtained to a small, centered spot, square-wave modulated in time and superimposed on various levels of diffuse, steady background illumination. When fully dark-adapted, both X-cells and Y-cells produced responses that were entirely sustained. When well lightadapted but still in the scotopic range, both cell types produced largely transient responses with only a very small sustained component. The sustained or transient nature of responses is, therefore, not an invariant characteristic of X-cells and Y-cells in the scotopic range. We also conclude that the mechanism which controls the center's sensitivity in the scotopic range is similar though not identical in the two types of cells.