Cellular degeneration and synaptogenesis in the developing retina of the rat

We have investigated the time course and magnitude of cellular degeneration in the ganglion cell layer and the presumptive amacrine and bipolar regions of the inner nuclear layer during the development of the retina in the rat. Pyknotic profiles are present in the ganglion cell layer during the first 2 postnatal weeks, reaching peak numbers during the first 4 postnatal days (corresponding to the time of greatest loss of ganglion cells and their axons: Potts et al., '82; Lam et al., '82; Perry et al., '83). Two observations suggest that the majority of pyknotic profiles present in the ganglion cell layer during the second postnatal week are not ganglion cells. First, following injection of kainic acid into one superior colliculus, degenerating ganglion cells in the contralateral retina are cleared within 24-48 hours. Therefore, since most ganglion cell and axon loss occurs within the first postnatal week, few of the pyknotic profiles present in the second week are likely to be ganglion cells. Second, the time course of cellular degeneration in the ganglion cell layer during the second postnatal week follows a very similar pattern to that seen in the presumptive amacrine sublayer of the inner nuclear layer. Such a correspondence suggests that two phases of cell death occur in the ganglion cell layer: during the first postnatal week the majority of dying cells are ganglion cells, and in the second, most cell death is due to a loss of displaced amacrine cells. In the inner nuclear layer pyknotic profiles are most numerous in the presumptive amacrine region on postnatal days 6 and 7, and in the presumptive bipolar region on day 10. Synaptogenesis in the inner plexiform layer occurs later but reflects the order of cell death. Thus, conventional (presumed amacrine) synapses were first observed on day 11 and synaptic ribbons (indicative of bipolar synapses) on day 13. These observations suggest that amacrine and bipolar cells initiate synapses only after their numbers have stabilized.     

Morphology of retinal ganglion cells in lungless salamanders (fam. Plethodontidae): an HRP and Golgi study

The family Plethodontidae consists of nearly two-thirds of all living urodeles; most of them possess highly developed visual abilities. We investigated the morphology of retinal ganglion cells (RGCs) in four representative species by means of the horseradish peroxidase method in flatmounts and in transverse sections and with the Golgi method in transverse sections. In flatmount preparations, four classes of RGCs were found, differing in dendritic arborization, dendritic field size, and stratification pattern of dendrites in the inner plexiform layer (IPL). Class-1 cells had small dendritic fields (29-44 microns 2) and arborized throughout the entire depth of the IPL. Class-2 cells had medium to large dendritic fields (75-206 microns 2) and mostly arborized in two or three laminae or in a diffuse fashion in the IPL. Class-3 cells had medium to large dendritic fields (72-200 microns 2) but sparse dendritic arborization. They only arborized in the proximal lamina of the IPL. Class-4 cells had large dendritic fields (273-626 microns 2) and branched in the most sclerad stratum of the IPL. No large differences in intraspecific soma size of the different RGC classes were detected (although interspecific soma size varied to a considerable degree) and no "giant" cells typically found in other vertebrate retinas were present. The results suggest that, with respect to the pattern of arborization and stratification of dendrites, lungless salamanders possess morphological classes of RGC similar to those found in frogs, but the morphology of RGCs in lungless salamanders seems to be simplified in comparison to frog RGCs. This simplification might be a consequence of paedomorphosis.     

The role of pioneer neurons in the development of mouse visual cortex and corpus callosum

The primordial plexiform neuropil is very critical to neocortical development. The pioneer neurons, mainly Cajal-Retzius cells in the marginal zone, and subplate neurons in the subplate, differentiate from the primordial plexiform neuropil. In this study, the development of corpus callosum, visual cortex, and subcortical pathways has been observed in C57BL/6 mice with various methods, such as DiI labeling in vitro and in vivo, DiI and DiA in vitro double labeling, immunocytochemistry, and in vivo BrdU and Fast Blue labeling. As early as E14, the primordial plexiform neuropil can be found in the telencephalic wall, and it contains many pioneer neurons. On E15 the primordial plexiform neuropil differentiates into the marginal zone and the subplate. Cajal-Retzius cells exist in the marginal zone, and subplate neurons are in the subplate. Either Cajal-Retzius cells or subplate neurons have long projections toward the ganglionic eminence, suggesting that they migrate tangentially from the ganglionic eminence. Cajal-Retzius cells are involved in radial migration, and subplate neurons participate to guide pathfinding of subcortical pathways. This study reveals how the pioneer neurons, through radial and tangential migration, play an important role in neocortical formation and in the pathfinding of the corpus callosum and subcortical pathways. Furthermore, DiI labeling in vivo has demonstrated the presence of pioneer neurons all along the corpus callosum pathway, especially in the midline. This suggests that pioneer neurons may also play a role in guiding the pathfinding of the corpus callosum. Accepted: 31 July 2001     

Immunohistochemical evidence for epinephrine-containing retinal amacrine cells

The enzyme for the synthesis of epinephrine, phenylethanolamine-N-methyltransferase, has been localized, by an indirect immunofluorescent staining method, to a subpopulation of amacrine cells in the rat retina. The immunoreactive cells are located primarily in the inner nuclear layer and send a single process to the inner plexiform layer. Most of the immunoreactivity is found in the center of the inner plexiform layer. A small percentage of immunoreactive cell bodies were found in the inner plexiform layer and occasionally cells were observed in the ganglion cell layer. These epinephrine-containing amacrine cells are morphologically distinct from the dopamine-containing amacrine cells previously described by formaldehyde fluorescence and we speculate from reports in the literature that epinephrine-containing amacrine cells may play a role in modulating the activity of dopamine-containing amacrine cells.     

Lateral actions at the inner plexiform layer of the carp retina: effects of turning windmill pattern stimulus

Lateral action from amacrine to ganglion cells was studied in the isolated carp retina by using a truncated windmill pattern (TWP). About 25% of ganglion cells of both "on" and "off" center types were suppressed or enhanced in firing activity in response to TWP turning. The suppressed cells were more sensitive to slow turning velocities of TWP than the enhanced cells. In the "on-off" type amacrine cells, a steady depolarizing or hyperpolarizing component (less than several mV) was maintained by stationary TWP, while the cells were exclusively depolarized by turning TWP at a wide range of velocities. These results suggest that individual responses of ganglion cells induced by both stationary and turning TWP are depending on a balance between two factors: the polarizing direction of steady components of the "on-off" amacrine cells and the polarizing direction of ganglion cells synaptically produced by the amacrine cells.     

ICL植入术后黄斑区节细胞-内丛状层及视网膜厚度的变化

目的：应用OCT观察ICL植入术后黄斑区节细胞-内丛状层及中央区视网膜厚度的改变,明确ICL植入术对于眼后节的影响。

方法：前瞻性研究。最终纳入行ICL植入术患者26例41眼,平均年龄28.19±6.48岁。所有受试者均行眼轴长度(AL)、裸眼视力(UCVA)、综合验光、最佳矫正视力(BCVA)、眼压(IOP)及OCT检查。观察术前及术后的中央区视网膜厚度(CRT)和节细胞-内丛状层厚度(GCT),以及UCVA、BCVA和IOP的变化。

结果： ICL植入术后UCVA和BCVA较术前均有提高(P<0.05),而眼压无变化。术前,术后1wk,1、3mo CRT分别为273.20±25.48、274.07±27.64、277.85±25.49、275.99±24.68μm,而GCT分别为85.31±5.19、88.95±6.87、87.73±4.23、87.45±4.59μm(均P<0.05),其中CRT在术后1mo较术前有增加(P<0.01),GCT在术后1wk,1、3mo均比术前有增加(P<0.05)。GCT在术后1wk的变化与AL呈正相关(r_s=0.529, P=0.001)。

结论：ICL植入术具有良好的有效性及一定的安全性,但术后也会发生一定的黄斑区改变,需给予一定的重视。     

Evaluation of spectral domain optical coherence tomography parameters in discriminating preperimetric glaucoma from high myopia

AIM: To evaluate the diagnostic ability of macular ganglion cell-inner plexiform layer (GCIPL) thickness obtained by spectral-domain optical coherence tomography (SD-OCT) in discriminating non-highly myopic eyes with preperimetric glaucoma (PPG) from highly myopic healthy eyes. METHODS: A total of 254 eyes, including 76 normal controls (NC), 116 eyes with high myopia (HM) and 62 non-highly myopic eyes with PPG were enrolled. The diagnostic ability of OCT parameters was accessed by the areas under the receiver operating characteristic (AUROC) curve in two distinguishing groups: PPG eyes with non-glaucomatous eyes including NC and HM (Group 1), and PPG eyes with HM eyes (Group 2). Differences in diagnostic performance between GCIPL and RNFL parameters were evaluated. RESULTS: The minimum (AUROC curve of 0.782), inferotemporal (0.758) and inferior (0.705) GCIPL thickness were the top three GCIPL parameters in discriminating PPG from non-glaucomatous eyes, all of which had statistically significant lower diagnostic ability than average RNFL thickness (0.847). In discriminating PPG from HM, the best GCIPL parameter was minimum (0.689), statistically significant lower in diagnostic ability than average RNFL thickness (0.789) and three other RNFL thickness parameters of temporal and inferotemporal clock-hour sectors. CONCLUSION: The minimum GCIPL thickness is the best GCIPL parameter to detect non-highly myopic PPG from highly myopic eyes, whose diagnostic ability is inferior to that of average RNFL thickness and RNFL thickness of several temporal and inferotemporal clock-hour sectors. The average RNFL thickness is recommended for discriminating PPG from highly myopic healthy eyes in current clinical practice in a Chinese population.