Retinal growth and cell addition during embryogenesis in the teleost, Haplochromis burtoni.

Neurogenesis of the developing embryonic retina is described for the African cichlid fish, Haplochromis burtoni, from 4 days post fertilization until all cell phenotypes are generated (day 7). Cell addition and differentiation both begin at the same absolute location which later becomes the central retina. As observed in most other vertebrates, cones and ganglion cells differentiate first, followed by amacrine and bipolar cells. Rod photoreceptors, which are added late, differentiate last. Changes in retinal thickness, retinal stretching, cell size, and cell density were measured during development. From day 4 through 7, there is an increase in retinal thickness largely due to the expansion of the inner plexiform layer (IPL) and outer nuclear layer (ONL). The inner nuclear layer (INL) decreases in thickness and there is a transient decrease in the density of cells in the scleral portion of the INL. Cells increase in size in the ganglion cell layer (GCL) and the vitread INL, decrease in size in the sclerad INL, and remain the same in the ONL. Changes in the density of the cell layers were observed: the density of ONL cells increased, the density of GCL cells decreased, and INL cells increased then decreased. From day 4 to day 6, eye growth is entirely due to cell addition because no retinal stretching was observed in the ONL or the horizontal layer. During this same developmental period, the pattern and rate of neurogenesis were measured in the differentiated portion of the retina by means of 3H-thymidine labeling. A small number of cell divisions within the differentiated INL precede the onset of cell divisions in the ONL. The number of 3H-thymidine labeled cells within the INL increases at a low rate consistent with an asymmetric pattern of cell division characteristic of stem cells. In contrast, cell divisions in the ONL increase exponentially, consistent with a symmetric pattern of cell division characteristic of progenitor cells. Double-label experiments (3H-thymidine and a rod specific opsin antibody) show that some of the symmetrically dividing cells in the ONL express the rod specific opsin within 2 days, suggesting that these dividing cells are rod progenitors. Although we do not hae conclusive evidence, these developmental processes support the hypothesis that stem cells within the INL could be the source of rod precursors in the embryonic teleost retina.     

Differential effect of taurine and serotonin on the outgrowth from explants or isolated cells of the retina

The sulfur amino acid taurine and the indoleamine serotonin increases and decreases, respectively, the outgrowth from goldfish retinal explants. Taurine seems to be acting, at least partially, through an increase in calcium fluxes, and the serotonin-inhibiting effect appears to be mediated by serotonin_1A receptors and cAMP. Isolated cells of postcrush goldfish retina and of retina from 5-day-old rats were cultured in the presence of taurine or serotonin. In the goldfish, the classical morphology of postcrush ganglion cells was observed. An antibody against the glycoprotein Thy-1 labelled three types of cells in the cultures of goldfish retina. The number of cells outgrowing and the length of the main neurite was measured at 5 days in culture in both species. The number of cells presenting neurites was increased in the goldfish retina by the addition of taurine, and decreased by serotonin. However, the length of the neurites was unaffected by the addition of the modulators. In the rat, only a slight decrease in the number of cells outgrowing was observed in the presence of serotonin. The incorporation of [³H]thymidinewas not modified after 5 days in culture in the presence of taurine or serotonin, either in the goldfish or in the rat retina. The antibody Thy 1.1 can label retinal cells of the goldfish invitro, one of them being ganglion cells. The trophic effect exerted by taurine in the postcrush goldfish retina needs the integrity of the tissue favoring the interaction of cells and factors, because outgrowth increases in retinal explants, but not in isolated cells.     

Influence of picrotoxin and strychnine on the spectral sensitivity of the turtle ERG b- and d-waves: II. Light adaptation

The aim of the present work was to investigate the role of GABA and glycine, the two main inhibitory neurotransmitters in the retina, in the spectral sensitivity coding under conditions of light adaptation. To study this question, spectral sensitivity curves, based on the turtle ERG responses to stimuli of different wavelengths, were constructed. The spectral sensitivity curves, obtained before and during treatment with picrotoxin (PT), a GABA_A antagonist, or with strychnine (ST), a glycine antagonist, were compared. Both PT and ST increased the b- and d-wave absolute sensitivity in a wavelength-dependent manner. PT significantly changed the shape of the b- and d-wave spectral sensitivity curves and the latter lost their peaks. It is concluded that, under conditions of light adaptation, GABA and glycine took part in the formation of the b- and d-wave spectral sensitivity curves, that both of them exerted an effect on the gain and that, furthermore, GABA had a well pronounced effect on the tuning of the spectral sensitivity curves.     

Autosomal dominant juvenile vitreoretinal degeneration and retinal detachment

To study the inheritance and clinical picture of a new form of vitreoretinal dystrophy I examined 18 family members of a family with six generations. Seven patients, three male and four female, in three consecutive generations were observed to be affected indicating autosomal dominant inheritance. The disease was characterized by juvenile degeneration of the vitreous with detachment of the vitreous body and some floating vitreous opacities, cystoid degeneration of the peripheral retina with whitish glistening stippled areas of superficial retinal degeneration, spotty hyperpigmentation, patches of retinal atrophy with pigmentations, occasional atrophic retinal holes, and in four family members at the age of 4 to 12 years, unilateral or bilateral retinal detachment with breaks in the peripheral retina. Most patients had hyperopia with or without astigmatism. In eyes without detached retina, the disease did not show any marked progression, the lens was clear, the posterior fundus and the retinal and choroidal vessels were normal, and the visual acuity, visual fields, dark adaptation, colour vision, electroretinograms, and visually evoked response findings were normal.     

中度视网膜冲击伤后血视网膜屏障改变兔模型的评价

应用ＢＳＴ－Ⅲ型生物激波管致伤建立的中度视网膜冲击伤兔模型，研究视网膜冲击伤后血视网膜屏障（ＢＲＢ）的改变，结果显示，中度视网膜冲击后除有炎症性反应外，可致视网膜细胞部分变性和坏死，ＢＲＢ轻度损害和视网膜电图（ＥＲＧ）ｂ波波幅下降４０％。由于受损细胞在某些因素如自由基的作用下可进一步导致ＢＲＢ严重继发性损害。如早期进行正确处理，可能阻止这种“不稳定”受损细胞的继发性损害。因此，该模型可用于研究视网     

New metrics for analysis of dendritic branching patterns demonstrating similarities and differences in ON and ON-OFF directionally selective retinal ganglion cells.

The morphology and dendritic branching patterns of retinal ganglion cells have been studied in Golgi-impregnated, whole-mount preparations of rabbit retina. Among a large number of morphological types identified, two have been found that correspond to the morphology of ON and ON-OFF directionally selective (DS) ganglion cells identified in other studies. These two kinds of DS ganglion cell are compared with each other, as well as with examples of class I, class II, and class III cells, defined here with reference to our previous studies. Cell body, dendritic field size and branching pattern are analyzed in this paper and levels of dendritic stratification are examined in the following paper. ON DS ganglion cells are about 10% larger in soma size and about 5 times the dendritic field area of ON-OFF DS ganglion cells, when compared at the same retinal location. These two morphological types of ganglion cell can be said to define the upper and lower bounds of an intermediate range of cell body and dendritic field sizes within the whole population of ganglion cells. Nevertheless, in previous physiological studies receptive field sizes of the two types were shown to be similar. This discrepancy between morphological and physiological evidence is considered in the Discussion in terms of a model of the excitatory receptive field of ON-OFF DS ganglion cells incorporating starburst amacrine cells. A new set of metrics is introduced here for the quantitative analysis and characterization of the branching pattern of neuronal arborizations. This method compares the lengths of terminal and preterminal dendritic branches (treated separately), as a function of the distances of their origins from the soma, viewed graphically in a two-dimensional scatter plot. These values are derived from computer-aided 3D logging of the dendritic trees, and distance from the soma is measured as the shortest distance tracked along the dendritic branches. From these metrics of the "branch length distributions," scale-independent branching statistics are derived. These make use of mean branch lengths and distances, slopes of lines fitted to the distributions, and elliptical indices of scatter in the distributions. By these measures, ON and ON-OFF DS ganglion cells have similar branching patterns, which they share to varying degrees with functionally unrelated class III.1 ganglion cells. The scale of the branching patterns of ON and ON-OFF DS cells and their degree of uniformity are different, however.(ABSTRACT TRUNCATED AT 400 WORDS)     

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 light microscopic localization of substance P- and somatostatin-like immunoreactive cells in the larval tiger salamander retina

Summary Light microscopic immunocytochemistry was utilized to localize the populations of substance P (SP)- and somatostatin (SOM)-like immunoreactive cells in the larval tiger salamander retina. Of 104 SP-immunostained cells observed, 82% were Type 1 amacrine cells. Another 8% of the SP-cells were classified as Type 2 amacrine cells, while 10% of the SP-cells had their cell bodies located in the ganglion cell layer and were designated as displaced amacrine cells. Each type of SP-like immunoreactive cell was observed in the central and peripheral retina. SP-immunopositive processes were observed in the inner plexiform layer as a sparse plexus in sublamina 1 and as a denser network of fibers in sublamina 5. Seventy-eight percent of the 110 somatostatin-immunopositive cells observed were designated as Type 1 amacrine cells. Another 12% of SOM-cells were classified as displaced amacrine cells, while only two SOM-immunopositive Type 2 amacrine cells were observed. Nine percent of the SOM-cells were designated as interplexiform cells, based on their giving rise to processes distributing in the outer plexiform layer as well as processes ramifying in the inner plexiform layer. Each type of SOM-immunoreactive cell was observed in the central and peripheral retina, with the exception of the Type 2 amacrine cells, whose somas were only found in the central retina. Lastly, SOM-immunopositive processes in the inner plexiform layer appeared as a fine plexus in sublamina 1 and as a somewhat denser network of fibers in sublamina 5.