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     

Role of electrical activity in promoting neural repair

The nervous system communicates in a language of electrical activities. The motivation to replace function lost through injury or disease through electrical prostheses has gained traction through steady advances in basic and translational science addressing the interface between electrical prostheses and the nervous system. Recent experiments suggest that electrical activity, signaling through specific molecular pathways, promotes neuronal survival and regeneration. Such data suggests that electrical prostheses, in addition to replacing lost function, may slow underlying degenerative disease or induce regenerative response. Here we review these data with a focus on retinal neurons, and discuss current efforts to translate this effect of electrical activity into clinically applicable treatments.     

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(retinal ganglion cells, RGCs)功能的变化情况。方法:运用多电极阵列(multi-electrode arrays,MEA)记录方法,记录视网膜退变中期(出生后20 d,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:ON sustained、ON transient、ON-OFF sustained、ON-OFF transient、OFF sustained和OFF transient RGCs,但OFF sustained RGCs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。     

基因重组碱性成纤维细胞生长因子对大鼠视网膜神经节细胞的影响

目的:研究基因重组碱性成纤维细胞生长因子(rbFGF)对大鼠视网膜神经节细胞(RGCs)的影响。方法:大鼠在视神经部分损伤后,球后注射生理盐水、维生素B₁₂、rbFGF,伤后4周进行轴突定量、视网膜神经节细胞定量以及RGCs凋亡的检测,观察视神经损伤修复情况。结果:伤后4周时,生理盐水和维生素B₁₂对RGCs无挽救作用,800U、1600U和2400U的rbFGF对RGCs挽救率分别为24.5%、27.3%、28.5%,800UrbFGF组、1600UrbFGF组和2400UrbFGF组未发生溃变的轴突数分别是损伤未治疗组的2.03、2.43、2.31倍。流式细胞仪检测结果显示:rbFGF治疗7d后,RGCs凋亡率显著减少。结论:rbFGF可提高视网膜神经节细胞的存活率,减少轴突溃变,有抗凋亡作用,对视神经损伤有显著的促功能修复作用。     

The size and shape of rod and cone centres of cat retinal ganglion cells

Summary Receptive field centres of cat retinal ganglion cells, as mediated by rod and by cone inputs, were mapped as contours of iso-sensitivity at a mid-mesopic adapting luminance using, respec-tively, 452 nm-blue and 578 nm-yellow narrow-band lights at an intensity 1 log unit above threshold for the most sensitive locus. Based on the sizes and shapes of mapped rod and cone centres for 74 ganglion cells, four receptive field centre categories were distinguished. Cone and rod centres were usually elliptical, and in almost 60% of cells the major axis through the receptive field centre was oriented within ±20 ° of horizontal. In 69%, rod and cone centres were non-concentric, 66% had larger rod than cone centres — area ratios ranging from 0.6 1 to 2.9 1, and in only two cases was the rod centre actually smaller than the cone centre.     

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(retinal ganglion cells,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Hoechst 33258 染色后观察视网膜细胞核形态的变化,Western blotting检测视网膜细胞cleaved caspase-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40 μmol/L时, RGCs活力无明显变化(P>0.05),但Sen浓度达到80和160 μmol/L时,RGCs活力明显下降,差异显著(P<0.01)。25、50、100和200 μmol/L H₂O₂明显降低RGCs活力(P<0.05)。Sen浓度在10、20和40 μmol/L时,对50 μmol/L H₂O₂损伤的RGCs有较好的保护作用(P<0.05),其中40 μmol/L Sen保护作用最为明显。Hoechst 33258染色表明Sen可以减少H₂O₂引起的视网膜细胞凋亡。Western blotting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cleaved caspase-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     

CPT-cAMP对成年金黄地鼠视网膜节细胞存活的影响

目的　探讨眼球玻璃体内注射CPT cAMP对切断视神经后视网膜节细胞存活的影响。方法　用荧光素逆行示踪标记法和定量解剖学技术观察视神经切断 5、7和 14d后成年金黄地鼠视网膜节细胞的密度。结果　 (1)正常视网膜节细胞平均密度为 2 0 0 7± 115 /mm2 ;(2 )视神经切断 5、7、14d后 ,视网膜节细胞平均密度分别下降至 :10 10± 131/mm2 、782± 5 5 /mm2 和2 14± 30 /mm2 ;(3)给予DMSO/生理盐水的对照组在上述各时间段视网膜节细胞平均密度与单纯神经切断组结果相似 ;(4)给予CPT cAMP的实验组在 5、7、14d视网膜节细胞的平均密度分别为 1398± 2 45 /mm2 、12 93± 84/mm2 和 5 0 1± 72 /mm2 ,与视神经切断组和DMSO/生理盐水对照组相比在各时间段上均存在显著性差异 (P <0 0 5 )。结论　CPT cAMP可提高视神经切断后成年金黄地鼠视网膜节细胞的存活。     

Genesis of neurons of the retinal ganglion cell layer in the opossum

Summary In this study, we have examined the genesis of neurons of the retinal ganglion cell layer of the opossum Didelphis marsupialis by [³H]-thymidine autoradiography. Our results suggest that most neurons surviving to adulthood are generated in postnatal life from day 1 to day 23. Cells are generated according to a coarse gradient from the retinal geometric center to the periphery. Regional analysis of soma size distributions in different cohorts suggest that this gradient is actually formed by two partially-overlapping, concentric waves of cell proliferation. Most medium and large ganglion cells are formed during the early wave, whereas most displaced amacrine cells and small ganglion cells are formed during the late wave. Our results confirm the appropriateness of the opossum as a model for studies of development of the mammalian visual system.     

Nogo-A在小鼠胚胎新生视网膜节细胞及其轴突的表达

目的 研究小鼠胚胎阶段Nogo-A在视网膜节细胞(RGCs)及其轴突上的表达及时程变化. 方法 取不同发育阶段的小鼠胚胎,采用免疫荧光染色,以激光扫描共焦显微镜观察Nogo-A在视觉传导通路中的表达.并采用免疫双标染色确定视网膜中表达Nogo-A蛋白的细胞类型. 结果 在视网膜发育的早期阶段(E12),Nogo-A密集表达于具有放射状形态的细胞上,Nogo-A免疫阳性产物出现在胞质、胞膜以及轴突上.Nogo-A与Tuj-1双标染色显示,此阶段的视网膜中几乎所有RGCs及其轴突都表达有Nogo-A;在稍晚的发育阶段(E13),视网膜中表达Nogo-A的RGCs数量明显减少,且仅出现在节细胞层以外的室周带和睫状体边缘区.在视网膜的神经纤维层,大部分RGCs轴突不再表达Nogo-A,仅有少量视觉纤维为Nogo-A免疫阳性;RGCs的神经发生基本完成后(E15), 视网膜中几乎检测不到Nogo-A免疫阳性的细胞,但视网膜纤维层仍有少量表达Nogo-A的节细胞轴突.与之类似,视神经盘、视茎、视交叉和视束都观察到少量Nogo-A免疫阳性的轴突.值得注意的是,视束中表达Nogo-A的纤维集中位于表浅部位,而此处恰为新近到达轴突的通过部位. 结论 Nogo-A在视网膜RGCs以及轴突上表达的时程变化和位置特点提示,新生RGCs及其轴突表达Nogo-A,成熟后RGCs内Nogo-A的表达则下调.推测新生RGCs及其轴突中表达的Nogo-A可能与减少轴突分叉等细胞的内在功能有关.     

酸枣仁皂甙A对急性高眼压大鼠视网膜神经节细胞的保护作用

目的探讨酸枣仁皂甙A对实验性急性高眼压(HIOP)鼠眼视网膜神经节细胞(RGCs)的保护作用。方法36只SD大鼠随机等分为空白对照组、模型组、酸枣仁皂甙A组,除空白对照组外,各组均用生理盐水前房灌注法建立急性高眼压模型。造模成功后酸枣仁皂甙A组给予酸枣仁皂甙A20mg/kg鼠尾静脉注射,每天1次,共7d。模型组予相同体积的生理盐水代替。术后7d,取大鼠眼球通过免疫组化检测和RT-PCR检测THY-1蛋白及mRNA表达。结果(1)空白对照组和对照组视网膜节细胞层的节细胞差异有统计学意义(P0.01);空白对照组和酸枣仁皂甙A组之间差异没有统计学意义。空白对照组、模型组和酸枣仁皂甙A组的视网膜神经节细胞密度分别为(22.0±2.2)个/高倍镜、(16±2.8)个/高倍镜和(21±2.7)个/高倍镜。(2)RT-PCR检测THY-1mRNA的表达在造模7d后明显降低,与正常组的差异有统计学意义(P0.01);酸枣仁皂甙A组跟正常组THY-1mRNA表达差异无统计学意义(P0.05)。结论酸枣仁皂甙A可提高实验性急性高眼压鼠眼RGCs的存活率,对RGCs具有保护作用。     

The survival of neonatal rat retinal ganglion cells in vitro is enhanced in the presence of appropriate parts of the brain

Summary The enzyme horseradish peroxidase (HRP) was injected into the visual centres of the brains of neonatal rats. Following dissociation of retinae into tissue culture, the ganglion cells could be identified by appropriate histochemical staining for HRP reaction product. Cultures were prepared of dissociated retinae from rats aged 2–6 days postnatal. After 3 h the cultures were fixed, and HRP-labelled cells visualized and counted. Estimates were made of the number of ganglion cells per retina at each age. Results indicated a loss of ganglion cells during the first few postnatal days. This loss paralleled that observed in vivo. It was further found the retinal ganglion cells died rapidly in vitro when cultured in a minimal medium. Only 50% of ganglion cells originally plated remained viable after 24 h. However, the survival rate could be increased to 100% by coculturing the cells with diencephalon and mesencephalon; these contain the retinorecipient nuclei. Coculturing with cerebellum did not result in such an enhanced survival rate. Ganglion cells could be maintained over longer periods of time by reinoculating the cultures with additional tissue containing diencephalon and mesencephalon. These results support the hypothesis that developing neurons require trophic factors from their target tissues in order to survive.Supported by the O.P.S.M. Research Foundation, the A.R.G.C. and the N.H. & M.R.C.     

The periphery effect in cat retinal ganglion cells: variation with functional class and eccentricity

Summary We have studied the responses of ganglion cells of the cat retina to visual stimulation remote from the center of their receptive field. Following previous work, this response is termed the periphery effect (PE). Cells were identified as Y-, X- or W-class from the latency of their response to optic chiasm stimulation and from their receptive field properties. The strength of the PE elicited by a rotating windmill or counterphased grating stimulus was measured for ganglion cells of all major classes. The PE was consistently stronger in Y- than in X-cells, and the strength of the effect in both X- and Y-cells increased significantly with retinal eccentricity. A PE was elicited from about 47% of W-cells studied. In some (36%) the effect was excitatory, as for X- and Y- cells; in others (11%) it was inhibitory. Despite this heterogeneity, the PE in W-cells increased significantly with eccentricity. These variations of the PE with eccentricity and cell class have implications for the circuitry of the inner plexiform layer.     

Morphological classification and retinal distribution of large ganglion cells in the retina ofBufo marinus

Summary The retrograde transport of horseradish peroxidase (HRP) and cobaltic-lysine complex (CLC) was used to morphologically characterize large ganglion cells (GCs) and to determine their distribution in retinal wholemounts and in sectioned material in the retina ofBufo marinus. Large GCs, amounting to about 0.5% of total GC population, were defined to be those with very large dendritic field sizes varying between 0.1 mm² to 0.6 mm² and cell soma sizes of between 100 m² to 400 m². These cells were subdivided into 3 major groups, Types I, II and III, on the basis of their dendritic field sizes, arborization patterns and the strata of dendritic branching within the inner plexiform layer (IPL). The majority of large neurons (about 90%) were classified as Type I GCs with symmetrical dendritic arbor. These cells had either bistratified branching in the scierai and vitreal sublaminae of the IPL (65% of Type I Cells) or unistratified branching in the scleral (26%) or in the vitreal (9%) sublamina. Their dendritic field sizes increased linearly from the retinal centre from 0.13 mm±0.02 mm² (mean and S.D.) to 0.58±0.11 mm² in the retinal periphery. Type II GCs (about 9% of the large GC population) were characterized by an asymmetrical dendritic arborization directed towards the ciliary margin with unistratified branching in the scierai sublamina of the IPL. The mean dendritic field sizes of these cells were 0.26±0.09 mm². Type III GCs, the least frequent (about 1%) category of large GCs had sparsely branching, elongated dendritic branching aligned approximately parallel with the nasotemporal axis of the retina. The unistratified dendritic branches of these neurons were located in the vitreal sublamina of the IPL with a mean dendritic field size of 0.42±0.11 mm². The dendritic field sizes of Types II and III GCs did not increase with retinal eccentricity. Type I GCs were distributed unevenly across the retina, the density being greatest in the visual streak, along the nasotemporal meridian of the retina. The dendritic field sizes of these cells increased towards the retinal periphery, resulting in a constant dendritic field coverage factor across the retina. Each retinal point was covered by the dendritic fields of 4–5 adjacent GCs. In contrast, Types II and III GCs had only discontinuous dendritic coverage. The identification of morphological types of large GCs with previously described functional classes of GCs in the anuran retina is discussed.On leave from the Department of Anatomy, University Medical School, Pécs, Hungary     

Morphological classification of retinal ganglion cells in adult Xenopus laevis

Summary Retrograde transport of horseradish peroxidase (HRP) was used to characterise the soma and dendritic arborization of retinal ganglion cells in adultXenopus laevis toad. HRP was administered to the cut end of the optic nerve and the morphological characteristics of HRP-filled ganglion cells were analysed in retinal wholemount preparations using computer assisted morphometry. Ganglion cells were classified according to their soma size, dendritic branching pattern, dendritic field and the number of shaft dendrites. Ganglion cells were divided into 3 major classes on the basis of soma sizes and extent of dendritic field: large (soma size, mean 258.04 μm²±52.03 SD; dendritic field size 0.104 mm²±0.23), medium size (126.7 μm²±37.01; 0.041 mm²±0.013) and small (87.3 μm²±22.69; 0.0061 mm²±0.0035). A more detailed analysis allowed 12 morphologically distinct subgroups to be identified (Types I–XII). Quantitative studies showed that large cells comprise about 1%, medium size about 8–9% and the small cells over 90% of total ganglion cell population. The number of large and medium size ganglion cells corresponded well with the number of myelinated optic fibres and the number of small neurons with the number of unmyelinated optic fibres in the optic nerve. Large ganglion cells were correlated with Class 4 and 5, medium size ganglion cells with Class 3 and small ganglion cells with Class 1 and 2 functionally characterized ganglion cells in the frog retina (Maturana et al. 1960). The retinal distribution of large ganglion cells appear to suggest certain similarities to mammalian alpha type ganglion cells.     

The immune escape in melanoma: role of the impaired dendritic cell function

Melanoma is an immunogenic cancer that overcomes the control of the immune system through the production of tolerogenic cytokines and growth factors in the microenvironment. In melanoma, dendritic cells (DC) show severe alterations in maturation, cross-priming and antigenic presentation, while other accessory cells infiltrating the tumor milieu also suppress DCs through the activation of the STAT pathway by IL-10 and IL-6. Novel immunotherapy strategies blocking cytotoxic T-lymphocyte antigen (CTLA-4) are successful in advanced disease, while melanoma cells carrying the BRAF^V600E mutation further reinforce the immune suppression by activating MAPKs. Here, we review the major mechanisms involved in the cross-talk between melanoma cells and the immune system as well as the issue of defects in DCs in relation to novel studies aimed at restoring their anti-tumor activity.     

The development and the topographic organization of the retinal ganglion cell layer in Bufo marinus

Summary The number and distribution of neurons in the retinal ganglion cell layer were studied from the metamorphic climax to adulthood in the toad Bufo marinus. Retinal wholemounts stained with cresyl violet showed that total neuron numbers increased from 55,000 at metamorphic climax to about 950,000 in adult animals. During the same time the entire retinal area increased 46-fold from an average 3.4 mm² to 157 mm². The morphological character of the neurons and their density across the retina changed during development. In metamorphosing animals, the neurons of the ganglion cell layer had a uniform appearance and their density increased slightly from the centre to the dorsal ciliary margin. After metamorphosis a high neuron density area, the visual streak, evolved in the retinal centre, resulting in the formation of a 6 to 1 density gradient from the visual streak out to the dorsal and ventral retinal poles in adult animals. Optic fibre numbers in juvenile and adult optic nerves were estimated to be 330,000 and 745,000, respectively, corresponding to similar ganglion cell numbers. One optic nerve was sectioned in a few animals and 4 weeks later the number of intact neurons — assumed to be displaced amacrine cells (DA) — was estimated. They amounted to 80,000 in juvenile and 189,000 in adult animals or about 20% of the total neuron population of the retinal ganglion cell layer, the remaining 80% being GC. A 1.7 to 1 density gradient of DA from the visual streak out to the dorsal and ventral retinal periphery was established. These results show that the visual streak evolves after metamorphosis from an originally uniform neuron distribution of the retinal ganglion cell layer. The possible mechanisms of the formation of the visual streak are discussed.     

Transplant of embryonal nervous tissue preserves the responses of rat retinal ganglion cells after section of the optic nerve

Summary We have investigated the effectiveness of embryonal tectal tissue transplants in preserving the physiological activity of lesioned ganglion cells by recording the visual responses from the adult rat retina after section of the optic nerve, with or without transplants of embryonal nervous tissue on the stump. We have found that transplant of embryonal nervous tissue at the level of the optic nerve section has dramatic effects in preserving visual retinal responses to patterned stimuli for times as long as five months after surgery. By this time retinal responses to patterned stimuli have almost completely disappeared in control animals with optic nerve section alone.     

Voltage-dependent currents in isolated cells of the turtle retinal pigment epithelium

The electrophysiological properties of isolated turtle retinal pigment epithelial cells (RPE cells) were investigated using the whole-cell patch-clamp technique. Most RPE cells exhibited a voltage-dependent outward current activated by depolarization beyond about –43 mV that inactivated during a 500-ms voltage step. Tail current measurements indicated that the conductance underlying this current was potassium selective. This current inactivated with prolonged depolarization and was abolished or reduced by extracellular quinidine, barium, tetraethylammonium (TEA) and 4-aminopyridine (4-AP). Steady-state inactivation of the voltage-dependent outward current revealed a time-independent outwardly rectifying current/voltage relationship in many cells. In addition, many cells had an outward current that activated slowly upon depolarization beyond about +40 mV and appeared to reverse near 0 mV in both 3 mM KCl and 30 mM KCl external solutions. This current was often observed in the presence of potassium channel blockers. Hyperpolarizing pulses commonly evoked inward currents that activated slowly and did not inactivate. These currents were commonly observed when fluoride was absent from the pipette, and only occasionally when fluoride was the major pipette anion. Tail current measurements indicated that this current was somewhat anion selective.These currents may play important roles in the homeostatic and phagocytic functions of RPE cells in their interactions with the neural retina.