Cell distributions in the retinal ganglion cell layer of adult Leptodactylid frogs after premetamorphic eye rotation (original) (raw)
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Visual Neuroscience, 1999
Population-based methods were used to study labeled retinal ganglion cells from the cane toad Bufo marinus and the treefrog Litoria moorei, two visually competent bufonoid neobatrachians with contrasting habitats. In both, cells with large somata and thick dendrites formed distinct types with independent mosaics. The a a , a ab , and a c mosaics of Bufo in all major respects resembled those of ranids, studied previously, and could be provisionally matched to the same functional classes. As in other frogs, some a a cells were displaced and many a-cells of all types were asymmetric, but within each type all variants belonged to one mosaic. Nearest-neighbor analyses and spatial correlograms confirmed that all three mosaics were regular and independent. In Litoria, monostratified a a cells were not found. Instead, two bistratified types were present, distinguished individually by soma size and dendritic caliber and collectively by membership of independent mosaics: the larger (;0.8% of all ganglion cells) was termed a1 ab and the smaller (;2.2%) a2 ab . An a c cell type was also present, although too inconstantly labeled for mosaic analysis. Nearest-neighbor analyses and spatial correlograms confirmed that the two a ab mosaics were regular and independent. Densities, proportions, soma sizes, and mosaic statistics are tabulated for each species. The emergence of a consensus pattern of a-cell types in fishes and frogs, from which this treefrog partly diverges, offers new possibilities for studying correlations between function, phylogeny, ecology, and neuronal form.
Vision Research, 1980
In the frog, as in many other vertebrates, the eye and, consequently the retina, continues to increase in size throughout life. In this paper ganglion cell densities in the retina of a Brasilian tree frog, Hyla raniceps, have been measured from methylene blue stained whole mounts. From a series of retinae, taken from individuals with body sizes ranging from that of a post-metamorphic juvenile to sexually mature adult, isodensity maps of cell density across the whole retina have been prepared. Concomitant measurement of the extent of the visual field of these animals allowed cell counts per mm2 to be converted to cells per unit visual angle. Changes in both cell density and distribution were observed with increasing body size and in central retina these changes resulted in an increasing number of cells representing each degree of visual field. In contrast, in the inferior and superior periphery the angular separation of ganglion cells remained approximately constant. The developmental, physiological and ecological significance of these findings is discussed.
Visual Neuroscience, 1997
Population-based methods were used to study labeled retinal ganglion cells from the cane toad Bufo marinus and the treefrog Litoria moorei, two visually competent bufonoid neobatrachians with contrasting habitats. In both, cells with large somata and thick dendrites formed distinct types with independent mosaics. The a a , a ab , and a c mosaics of Bufo in all major respects resembled those of ranids, studied previously, and could be provisionally matched to the same functional classes. As in other frogs, some a a cells were displaced and many a-cells of all types were asymmetric, but within each type all variants belonged to one mosaic. Nearest-neighbor analyses and spatial correlograms confirmed that all three mosaics were regular and independent. In Litoria, monostratified a a cells were not found. Instead, two bistratified types were present, distinguished individually by soma size and dendritic caliber and collectively by membership of independent mosaics: the larger (;0.8% of all ganglion cells) was termed a1 ab and the smaller (;2.2%) a2 ab . An a c cell type was also present, although too inconstantly labeled for mosaic analysis. Nearest-neighbor analyses and spatial correlograms confirmed that the two a ab mosaics were regular and independent. Densities, proportions, soma sizes, and mosaic statistics are tabulated for each species. The emergence of a consensus pattern of a-cell types in fishes and frogs, from which this treefrog partly diverges, offers new possibilities for studying correlations between function, phylogeny, ecology, and neuronal form.
Visual Neuroscience, 1997
Population-based studies of retinal neurons have helped to reveal their natural types in mammals and teleost fishes. In this, the first such study in a frog, labeled ganglion cells of the mesobatrachian Xenopus laevis were examined in flatmounts. Cells with large somata and thick dendrites could be divided into three mosaic-forming types, each with its own characteristic stratification pattern. These are named αa, αab, and αc, following a scheme recently used for teleosts. Cells of the αa mosaic (~0.4% of all ganglion cells) had very large somata and trees, arborizing diffusely within sublamina a (the most sclerad). Their distal dendrites were sparsely branched but achieved consistent coverage by intersecting those of their neighbors. Displaced and orthotopic cells belonged to the same mosaic, as did cells with symmetric and asymmetric trees. Cells of the αab mosaic (~1.2%) had large somata, somewhat smaller trees that appeared bistratified at low magnification, and dendrites that b...
The role of visual experience in the formation of binocular projections in frogs
Cellular and Molecular Neurobiology, 1985
1. Many parts of the visual system contain topographic maps of the visual field. In such structures, the binocular portion of the visual field is generally represented by overlapping, matching projections relayed from the two eyes. One of the developmental factors which helps to bring the maps from the two eyes into register is visual input.
Displaced retinal ganglion cells in normal frogs and those with regenerated optic nerves
Anatomy and Embryology, 1992
We have analysed the number and spatial distribution of displaced retinal ganglion cells in the frog Litoria (Hyla) moorei. A series of normal animals was compared with one in which the optic nerve was crushed and allowed to regenerate. Ganglion cells were labelled with horseradish peroxidase (HRP) applied to the optic nerve, and retinae were examined as sections or whole mounts. We analysed separately ganglion cells with somata displaced to the inner nuclear (Dogiel cells, DGCs) and to the inner plexiform layer (IPLGCs). These findings were related to data for the orthotopic ganglion cells (OGCs). The mean number of DGCs in the normal series was 2,550 (• 281) and fell to 1,630 (_+ 321) after regeneration, representing a mean loss of 36%. This reduction was not significantly different from the mean loss of 43% from the OGC population in which mean values fell from 474,700 (+47,136) to 268,700 (-t-54,395). In both the normal and the regenerate series, DGCs were estimated to represent means of only 0.6% of the OGC population. Densities of DGCs were highest in the nasoventral and temporo-dorsal peripheries; densities of both DGCs and OGCs were lower after optic nerve regeneration. We conclude that the factors which affect ganglion cell death during optic nerve regeneration, do so to similar extents amongst the DGC and the OGC populations. The IPLGCs were very rare in normal animals with a mean of 420 (_+ 95). However, their numbers increased after regeneration to a mean of 3,350 (_+ 690), estimated to be 1.2% of the OGC population. These cells normally favoured peripheral retina but became pan-retinal after regeneration. The primary dendrites of the majority of IPLGCs were oriented in the same direction as those of OGCs. We conclude that most IPLGCs were OGCs which had relocated their somata to the inner plexiform layer.
The Journal of Comparative Neurology, 1974
The order of production of retinal cells and the time when retinal cells become post-mitotic was studied in Runa pipiens embryos using 3Hthymidine autoradiography. Cell division stops first in the fundus of the retinal rudiment between embryonic stages 17 and 18 and gradually becomes restricted to the retinal margin. The ganglion cells in the fundus are among the first cells to become post-mitotic. The specification of the central connections of ganglion cells was studied by rotating the eye primordium at embryonic stages 16-21. After metamorphosis, the visual projection from the rotated eye to the contralateral optic tectum was mapped electrophysiologically and compared with the normal retinotectal map. In all cases, the visual projection map was rotated through the same angle as was indicated by the position of the choroidal fissure. It appears that ganglion cell connections with the tectum were specified by stage 17. These results indicate that ganglion cell central connections are specified before the first ganglion cells become post-mitotic.
Neuroscience Letters, 1997
The loss of a free-living larval stage during the evolution of directly developing frogs of the genus Eleutherodactylus resulted in dramatic alterations in ontogeny. Immunostaining for proliferating cell nuclear antigen reveals that in the directly developing frog Eleutherodactylus coqui pervasive cell proliferation occurs throughout the retina even after the plexiform layers have formed. In striking contrast to biphasically developing frogs (e.g. Discoglossus pictus or Xenopus laevis), in E. coqui proliferation becomes restricted to the ciliary margin only after the eye has reached the size typical of a postmetamorphic froglet and after its laminar structure has developed. As a consequence, the retina of E. coqui develops rapidly without recapitulating larva-typical stages. Our results suggest that dissociation of cell proliferation and differentiation can lead to the abbreviation of ontogenies during evolution.
The Journal of Comparative Neurology, 1983
The mode of entry of retinal ganglion cell (RGC) axons and the detailed morphology of their arbors has been studied in the tectal lobes of the frog Rana pipiens. These tecta were subjected intact to H R P histochemistry and subsequently flat-mounted for examination under a compound microscope. Subsets of RGC axons were labelled by inserting small pellets of solidified HRP into the optic chiasm region or into the tectal neuropil itself. Annular or semiannular patterns of retinal ganglion cell arbors were always observed after placement of HRP in the chiasm region. HRP pellets in the tectal neuropil labelled segments of annuli in caudal tectal regions. These tectal patterns corresponded to a similar annular distribution of HRP-filled RGC bodies in the topographically appropriate regions of the contralateral retina.
Article, 2009
The topography and morphology of retinal ganglion cells (RGCs) in the eastern newt were studied. Cells were retro-gradely labeled with tetramethylrhodamine-conjugated dextran amines or horseradish peroxidase and examined in retinal wholemounts. Their total number was 18,025 3,602 (mean SEM). The spatial density of RGCs varied from 2,100 cells/mm 2 in the retinal periphery to 4,500 cells/mm 2 in the dorsotemporal retina. No prominent retinal specializa-tions were found. The spatial resolution estimated from the spatial density of RGCs varied from 1.4 cycles per degree in the periphery to 1.95 cycles per degree in the region of the peak RGC density. A sample of 68 cells was camera lucida drawn and subjected to quantitative analysis. A total of 21 parameters related to RGC morphology and stratification in the retina were estimated. Partitionings obtained by using different clustering algorithms combined with automatic variable weighting and dimensionality reduction techniques were compared, and an effective solution was found by using silhouette analysis. A total of seven clusters were identified and associated with potential cell types. Kruskal-Wallis ANOVA-on-Ranks with post hoc Mann-Whitney U tests showed significant pairwise between-cluster differences in one or more of the clustering variables. The average silhouette values of the clusters were reasonably high, ranging from 0.52 to 0.79. Cells assigned to the same cluster displayed similar morphology and stratification in the retina. The advantages and limitations of the methodology adopted are discussed. The present classification is compared with known morphological and physiological RGC classifications in other salamanders. J. Comp. Neurol. 516:533–552, 2009. Understanding how the nervous system works is impossible without identification of its elementary blocks, neuron types. Knowing neuron types is also essential for establishing their evolutionary relationships in homologous lineages and elucidating the mechanisms of neuron ontogeny. The concept of neuron type is not as straightforward as it might seem at first glance (Cook, 1998, 2003). The key to the discovery of neuron types is to distinguish between within-and between-type variation of certain parameters related to neuron structure, function, or development (Rodieck and Brening, 1983). An obvious way to identify neuron types would be to use type-specific molecular markers. At present, however, it is not practicable because such markers are known for a limited number of neuron types and even these seem to be only partially specific (Masland and Raviola, 2000). Neuronal morphology therefore remains an adequate means for neuron classification. It has long been realized that neuron classification should be based on a set of nonsubjective parameters and should be made by using automated algorithms (Rodieck and Brening, 1983; Schweitzer and Renehan, 1997). Despite certain difficulties and limitations of this approach (Ertö z et al., 2003; Ivá ncsy et al., 2005), an increasing number of papers using it have been published in recent years. Retinal ganglion cells (RGCs) comprise the last relay in the retinal signal circuitry. They send axons to a variety of brain centers providing a link between the eye and the brain. The number of studies addressing the morphological diversity of