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  • 1
    Electronic Resource
    Electronic Resource
    Abnormalities in the visual system of xenopus after larval optic nerve section (1977)
    Springer
    Experimental brain research 30 (1977), S. 369-385 
    Details
    ISSN: 1432-1106
    Keywords: Visual development ; Abnormal nerve route ; Intertectal connections
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary One optic nerve was cut in a series of larval Xenopus laevis; in approximately half of these the corresponding eye was also rotated. The resultant primary visual projections were mapped in the adult. Although in most cases the projections were retinotopically normal, some of them were not. These abnormal projections were consistently associated with a very thin optic nerve which reached the tectum via the oculomotor route. Animals with rotated eyes which developed retinotopically organised primary projections had a normal intertectal ipsilateral projection from the rotated eye and a rotated projection from the normal eye, thus confirming earlier findings that a process of binocular interaction determines the formation of intertectal connections. In all frogs with retinotopically abnormal primary projections the intertectal connections from the normal eye were of the type found after enucleation and those from the abnormal side were fragmentary or absent. Since the development of abnormal retinotopic patterns preceded that of intertectal connections the mechanisms of binocular interaction must have broken down in the presence of the abnormal primary projections.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00237263
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  • 2
    Electronic Resource
    Electronic Resource
    Retinal ganglion cell death during regeneration of the frog optic nerve is not accompanied by appreciable cell loss from the inner nuclear layer (1990)
    Springer
    Anatomy and embryology 182 (1990), S. 487-492 
    Details
    ISSN: 1432-0568
    Keywords: Optic nerve regeneration ; Retina ; Ganglion cell death ; Inner nuclear layer ; Frog (Hyla moorei)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary We estimated cell numbers in the ganglion cell and inner nuclear layers of adult frog (Hyla moorei) retinae, examining normal animals and those with regenerated optic nerves. Analysis of sections stained with cresyl violet showed that cell numbers in a nasotemporal strip, which included the area centralis and visual streak, were comparable between sides for both these cellular layers in normal animals. In line with our previous observations, after optic nerve regeneration cell numbers in the ganglion cell layer had fallen by 35–43% compared to the unoperated sides. By contrast cell numbers remained similar for the inner nuclear layers on the two sides. We conclude that retrograde transneuronal degeneration had not taken place in the inner nuclear layer in response to ganglion cell death.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00178914
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  • 3
    Electronic Resource
    Electronic Resource
    Development of visual projections in the marsupial, Setonix brachyurus (1986)
    Springer
    Anatomy and embryology 175 (1986), S. 181-188 
    Details
    ISSN: 1432-0568
    Keywords: Development ; Primary visual projections ; 3H-proline ; Autoradiography ; Marsupial
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Retinal projections to the primary visual centres were studied following injection of tritiated proline into one eye in the Marsupial, Setonix brachyurus between 10 and 100 days postnatal and in adults. Initially, projections from the two eyes overlapped extensively, particularly between 20 and 50 days. There was a gradual refinement thereafter, including a segregation of inputs from the two eyes within both the lateral geniculate nucleus (LGN) and superior colliculus (SC) by 70 days. Such refinement in visual centres is discussed in relation to the concurrent emergence of retinal ganglion cell density gradients, a decrease in ganglion cell numbers, cell death in the ganglion cell layer and loss of optic axonal profiles.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00389594
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  • 4
    Electronic Resource
    Electronic Resource
    Development of topographic connections between the isthmic nuclei and optic tecta in the frog Limnodynastes dorsalis (1990)
    Springer
    Anatomy and embryology 181 (1990), S. 167-176 
    Details
    ISSN: 1432-0568
    Keywords: Tecto-isthmo-tectal pathways ; Binocular projection ; Age gradients ; Horseradish peroxide ; Tadpoles
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In the frog Limnodynastes dorsalis, the pattern of topographic connections between the isthmic nuclei and optic tecta was determined by anterograde and retrograde transport of horseradish peroxidase from localised tectal regions. In both larvae and adults, reciprocal mapping of the uncrossed isthmo-tectal and tecto-isthmal projections was evidenced by the juxtaposition of labelled tecto-isthmal terminations with labelled cells in the cortex and medulla of the ipsilateral isthmic nucleus. The crossed isthmo-tectal projection was revealed by labelled cells in the cortex and medulla of the nucleus contralateral to the injection. In adults, rostral tectal areas projected to rostral and ventral regions of the ipsilateral isthmic nucleus. Following more caudal tectal injections, labelled cells were found in progressively more dorsal locations within the nucleus. Labelled cells in the contralateral nucleus were found in the rim cortex abutting a neuropil and in medullary cells adjacent to this region. Connections between ventral isthmic regions and most rostral tectum and between dorsomedial nucleus and caudomedial tectum were similar in both nuclei. However, for isthmic areas projecting to rostromedial and mid-tectum, the location of labelled cells in the contralateral nucleus was inverted with respect to the ipsilateral nucleus. This inversion would allow both nuclei to project to visually corresponding regions of each tectum. During larval stages the basic adult topography was established despite the continued neurogenesis of both isthmic nuclei and optic tecta. In late larval stages a rim neuropil appeared adjacent to the cortical region in the isthmic nuclei where labelled cells of the crossed isthmotectal projection were found. Prior to this stage labelled cells abutted labelled medullary cells. The appearance of this neuropil was approximately temporally correlated with the onset of electrophysiologically detectable responses in the ipsilateral visuotectal projection. Formation of the rim neuropil may relate to maturation of the tecto-isthmo-tectal connections which underlie this visual projection.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00198956
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  • 5
    Electronic Resource
    Electronic Resource
    Patterns of cytogenesis in the developing retina of the WallabySetonix brachyurus (1987)
    Springer
    Anatomy and embryology 177 (1987), S. 123-130 
    Details
    ISSN: 1432-0568
    Keywords: Development ; Retina ; Mitosis ; Plexiform Layers ; Pigment epithelium ; Marsupial
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Patterns of mitosis were examined during development from embryonic day (E) 19,9 days before birth, for retinae of the wallabySetonix brachyurus, using cresyl violet stained material. For neural retina, mitosis took place at the ventricular surface from the earliest stage of eye formation until postnatal day (P) 100. Numbers of mitotic figures reached a peak of approximately 12000 by P43. Average densities ranged between 300/mm2 and 600/mm2 up to P12 and then fell to below 50/mm2 by P25 before reaching a second peak of over 400/mm2 at P43. Up to P50, mitoses were present across the entire retina. By P60, a ‘cold spot’ lacking mitotic activity had formed in temporal retina and progressively extended to reach peripheral regions by P100; no mitoses were seen at P150. The timing and location of the ‘cold spot’ coincided with our previous description of the appearance of an area centralis in the ganglion cell layer (Dunlop and Beazley 1985). Inner and outer plexiform layers (IPL and OPL) formed between P24–40 and P50–100 respectively and were seen first in temporal retina. Furthermore, the extent of the OPL matched the mitotic ‘cold spot’. By contrast to neural retina, mitosis in the pigment epithelium was panretinal and was largely complete by P3. The data suggest that cell addition to the inner or outer nuclear layers contribute to differential retinal expansion and the establishment of cell density gradients in the ganglion cell layer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00572536
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  • 6
    Electronic Resource
    Electronic Resource
    Displaced retinal ganglion cells in normal frogs and those with regenerated optic nerves (1992)
    Springer
    Anatomy and embryology 185 (1992), S. 431-438 
    Details
    ISSN: 1432-0568
    Keywords: Retina ; Displaced ganglion cells ; Ganglion cells in the inner plexiform layer ; Frog ; Optic nerve ; regeneration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary 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 (±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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00174081
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  • 7
    Electronic Resource
    Electronic Resource
    Disconnected optic axons persist in the visual pathway during regeneration of the retino-tectal projection in the frog (1992)
    Springer
    Experimental brain research 90 (1992), S. 630-634 
    Details
    ISSN: 1432-1106
    Keywords: Optic nerve regeneration ; Axonal degeneration ; Frog
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In this study, we crushed one optic nerve in the frog Litoria (Hyla) moorei and at intervals thereafter anterogradely labelled optic axons with horseradish peroxidase (HRP). For one series, HRP was applied between the eye and the crush site and in a second series between the crush site and the chiasm. A tectal projection of regenerating axons was seen in both series but, in addition, up to 12 weeks post-crush, the second series displayed an additional projection. Its appearance matched that of the disconnected, but persisting, optic axon terminals which are found after enucleation or optic nerve ligation. We conclude that, in the frog, many disconnected optic axons persist throughout the period of optic nerve regeneration and of restoration of an orderly retino-tectal map.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00230948
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  • 8
    Electronic Resource
    Electronic Resource
    Development of intertectal neuronal connections in Xenopus: The effects of contralateral transposition of the eye and of eye removal (1975)
    Springer
    Experimental brain research 23 (1975), S. 505-518 
    Details
    ISSN: 1432-1106
    Keywords: Visual development ; Intertectal connections ; Xenopus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The development of intertectal neuronal connections has been investigated in Xenopus laevis. Contralateral eye grafts and enucleations were performed in embryos and the resultant visual projections to the optic tecta were mapped electrophysiologically after metamorphosis. In enucleated animals the ipsilateral projections were found to be normally organised retinotopically but consisted of visual units with abnormally large multi-unit receptive fields. In 10 animals with contralaterally grafted eyes a normal ipsilateral projection had developed from the abnormal eye and an abnormal projection from the normal eye, to produce congruent maps via the two eyes to one tectum. All the maps in these animals were retinotopically organised. In another 11 animals the ipsilateral projection from the operated eye was fragmentary or absent, while that from the unoperated eye resembled the pattern found after enucleation. Retinotopically abnormal contralateral projections had developed in 5 animals of this group. These results suggest that prefunctional specification determines the initial development of diffuse intertectal visual connections but these may be modified by a process of binocular interaction in the presence of a normal primary contralateral input.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00234918
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  • 9
    Electronic Resource
    Electronic Resource
    Factors determining decussation at the optic chiasma by developing retinotectal fibres in Xenopus (1975)
    Springer
    Experimental brain research 23 (1975), S. 491-504 
    Details
    ISSN: 1432-1106
    Keywords: Development ; Optic nerve ; Decussation ; Amphibia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In Amphibia all primary retinotectal nerve fibres cross at the chiasma. To investigate why this decussation takes place, a series of embryological operations were performed in which one host eye was replaced by an eye from the opposite side of a donor in Xenopus laevis. The visual projections to the optic tecta were mapped electrophysiologically in these animals when adult to reveal to which side of the brain the nerve fibres had become connected. In the majority of cases the contralaterally grafted eyes had developed primary projections to both tecta, in others all the fibres had innervated the contralateral tectum and in 2 animals optic axons were detected only from the ipsilateral side. In 2 other animals optic nerve fibres from both the normal and operated eyes had innervated both tecta. Control experiments showed that section of the optic nerve and stalk without any misalignment of the eye and stalk did not disturb the normal decussation of the fibres. Neither did enucleation in the embryo affect the decussation of the fibres from the remaining eye. It is concluded that no “side specificity” has been shown to exist to determine the side of the brain into which retinotectal fibres develop; rather it seems that complete decussation depends on the developing optic nerve fibres being able to enter a normally aligned optic stalk as they leave the eye.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00234917
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