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PubMed1990

Differential growth and remodelling of ganglion cell dendrites in the postnatal rabbit retina.

The postnatal dendritic maturation of small field type 1 (SF1), medium field type 1 (MF1) and type 2 (MF2), and large field type 1 (alpha) ganglion cells in the rabbit retina was compared qualitatively and quantitatively. Dendritic tree structure was revealed by intracellular injection of the fluorescent dye Lucifer yellow, and the stained cells were then morphologically separated on the basis of some area, dendritic field size, total dendritic length, number of nodes, and mean internodal distance. Cells in the visual streak and an area inferior to the streak were sampled from retinae between birth and adulthood. The dendrites of all studied classes of rabbit ganglion cells were extensively covered by short spine-like appendages. As in cat retina, many dendritic spines disappeared by the end of the third postnatal week, at which stage the adult dendritic form could be recognised. However, there was differential loss in the number of spines from the dendrites of the four cell classes. In both the streak and inferior retina, adult SF1 cells had the same number of spines/dendritic unit length throughout postnatal life, whereas MF1 and MF2 ganglion cells lost at least half of their number of spines/unit dendritic length by maturity. Alpha ganglion cells lost virtually all their dendritic spines by adulthood. In both retinal locations, there were small changes in the number of nodes (dendritic branch points) of small field and medium field ganglion cells but alpha cells lost between 70 to 80% of their nodes by adulthood. The dendrites of ganglion cells with contrasting morphology thus undergo differential remodelling during postnatal maturation. The completion of the period of dendritic remodelling coincided with the first appearance of adult receptive field organisation, suggesting that structural remodelling, in particular that involving dendritic spines, may be associated with the development of the cell's synaptic circuitry. The dendrites of neighbouring postnatal ganglion cells in the rabbit retina also grow by different amounts; the increase in dendritic tree area, total dendritic length, and mean internodal distances of alpha cells exceeded that of small field and medium field cells in corresponding retinal positions. This implies that retinal dendrites elongate by active growth rather than by "passive stretching."

Aging↗
PubMed1991

Quantitative study of the tectally projecting retinal ganglion cells in the adult frog. II. Cell survival and functional recovery after optic nerve transection.

It is known from previous work that ganglion cells disappear from the retina in significant numbers during optic nerve regeneration in the adult frog. In the present study, the population size of surviving ganglion cells that have returned axon terminals to the correct tectal loci was estimated by counts of retrogradely labeled cells in retina-flat-mounts after tectal injections of HRP. Bilaterally symmetric injections were delivered to allow comparison of the normal and affected retinas. The frogs studied had regenerated the left optic nerve and had visually guided behaviors initiated by the recovered eye (see below). The proportion of tectally projecting ganglion cells in the normal retinas and in retinas of normal frogs studied in parallel ranged from 83-86% (Singman and Scalia: J. Comp. Neurol. 302:792-809, 1991). In the affected retinas, the subpopulation of tectally projecting cells was reduced by 40-90% after regeneration, and the relative size of this subpopulation ranged from 67-86%. The optic tectum was injected unilaterally in one specimen, on the side ipsilateral to the regenerated (left) optic nerve. The HRP-labeled ganglion cells in the ipsilateral (left) retina accounted for only 0.8% of the surviving ganglion cells in this animal, whereas it was previously found that the ipsilateral tectally projecting ganglion cells normally amount to 0.9-2.3% (Singman and Scalia, op. cit.) In frogs recovering from transection of the left optic nerve, the frequency, latency, and accuracy of the prey-acquisition responses initiated by the recovering eye were compared with those initiated by the normal eye. Mealworms or lure dummies were used to stimulate prey acquisition. In one experiment, the stimuli were presented unilaterally in the monocular fields of frogs permitted to use both eyes. Prior to the fourteenth postoperative week, the affected eye initiated responses of abnormally long latency and low frequency. In contrast, responses initiated by the affected eye after 14 weeks appeared to be normal in all respects. In another experiment, the normal eye was sutured shut in some frogs recovering for at least 24 weeks and then the affected eye was retested. The affected eye was capable of consistently initiating brisk and accurate prey acquisition. In a final experiment, two stimuli were presented simultaneously in bilaterally symmetric regions of the monocular fields of frogs surviving at least 42 weeks. These fully recovered frogs showed no preference for using either the normal or the recovered eye. Despite severe loss of tectally projecting ganglion cells during optic nerve regeneration, frogs are capable of apparently normal visual responses in prey acquisition tests.

Animals↗
PubMed1992

Biphasic retinal neurogenesis in the brush-tailed possum, Trichosurus vulpecula: further evidence for the mechanisms involved in formation of ganglion cell density gradients.

We investigated cell generation in the retina of the brush-tailed possum (Trichosurus vulpecula) by using tritiated (3H)-thymidine labelling of newly generated cells. Animals aged between postnatal day (P) 5 and 85 each received a single injection of 3H-thymidine. Following autoradiographic processing, maps of labelled cells were constructed from retinal sections. Retinal cell generation takes place in two phases, the first is concluding in the retinal periphery at P53 as the second is seen to commence in midtemporal retina. In the first phase, cells in central retina are generated earlier than those in peripheral regions. In the second phase, cells complete their final division in midtemporal retina first and in the periphery last. Cells generated in the first phase comprise virtually all cells in the ganglion cell layer, amacrine cells, horizontal cells, and cones. Ganglion cells are produced at a slightly earlier stage than displaced amacrine cells, horizontal cells, or cones. Amacrine cells in the inner nuclear layer are the final cells produced in the first phase. When ganglion cells and amacrine cells are pooled, their combined rate of production matches that of the other cell types. These data indicate that the ratio of displaced amacrine cells: horizontal cells: cones: combined ganglion cells and amacrine cells does not change throughout development. However, the ratio of ganglion cells:macrines changes steadily as development proceeds to favour amacrine cells. In the second phase, sparse numbers of nonganglion cells in the ganglion cell layer and large numbers of bipolar and Müller cells are produced along with all rods. The two phases in the possum are similar to those seen in the wallaby, the quokka. However, fewer cells are added in central retina in the possum than in the quokka and cell addition continues for a more extended period in the periphery in the possum. We suggest that this difference in cell addition could account for the development of a more pronounced visual streak of retinal ganglion cells in the possum than in the quokka. A comparison of possum retinal cell generation with that of other marsupials adds support for the "homochrony theory."

Aging↗
PubMed1993

Spatial organization of inner hair cell synapses and cochlear spiral ganglion neurons.

The morphological organization of the central projections of the cat cochlear spiral ganglion into the cochlear nucleus was previously investigated by creating restricted lesions in the anteroventral cochlear nucleus (AVCN) to ablate selectively either the lateral or the medial aspect of isofrequency projection laminae. Such lesions resulted in highly selective retrograde degeneration of spiral ganglion cells. Ablation of the lateral part of the AVCN caused degeneration of cells within the scala tympani part of the ganglion, whereas medial ablations within the AVCN induced degeneration of the scala vestibuli aspect of the ganglion. The peripheral axons also degenerated and this fiber loss exhibited selective topographies that paralleled the cell loss within the spiral ganglion, although this phenomenon was more prominent in the proximal part of the osseous spiral lamina near the ganglion and less obvious more distally near the habenula perforata. In this investigation, inner hair cells (IHCs) from these selective lesion cases were evaluated by electron microscopy of serial sections through the basal synaptic regions. Results demonstrated differential degeneration of afferent synapses, with greater (but not completely selective) loss of pillar synapses after lateral AVCN lesions and greater loss of modiolar synapses after medial lesions. Because auditory nerve fibers of different spontaneous discharge rates (SRs) have different spatial distributions on the IHC (Liberman, Science 216:1239, 1982), our results suggest that this SR-based organization is maintained in a topographic organization across the vertical (scala tympani-to-scala vestibuli) dimension of the spiral ganglion cell cluster and carried into the ventral cochlear nuclei (VCN). Thus, in addition to the spiral frequency organization represented by the dorsal-to-ventral frequency map in the VCN, there is also an orderly organization of inputs from high- and low-SR fibers across the lateral-to-medial dimension of the VCN such that the lateral isofrequency laminae receive a proportionately greater input from high-SR fibers, whereas medial isofrequency laminae receive preferential input from low- and medium-SR fibers.

Animals↗
PubMed1993

Survey of the morphology of macaque retinal ganglion cells that project to the pretectum, superior colliculus, and parvicellular laminae of the lateral geniculate nucleus.

In common with other vertebrates, the primate retina contains a number of different ganglion cell types that project to different regions in the brain. We wanted to determine how the different ganglion cell types, distinguished morphologically, mapped to these regions of the brain. We injected a fluorescent dye into one of three regions of a macaque brain: the superior colliculus (SC), the pretectal region, and the parvicellular laminae of the lateral geniculate nucleus. By means of an in vitro preparation, the retrogradely labelled ganglion cells were intracellularly injected with horseradish peroxidase, so as to reveal their dendritic morphology. When the dendritic-field diameters of the injected cells were plotted against retinal eccentricity, each of the three regions was found to receive input from a distinctive population of cells. The pretectal projection was dominated by cells with large dendritic fields. The SC projection was composed of a number of distinct types, with smaller dendritic fields. Parasol cells project to SC but are extremely rare. In addition to midget ganglion cells, the parvicellular laminae receive inputs from at least two additional groups. Parvicellular bistratified (PB) cells have bistratified dendritic fields, slightly larger than those of parasol cells. Parvicellular giant (PG) cells have dendritic-field diameters larger than that of any parasol cell, ranging from 250 microns to greater than 850 microns--the largest of any primate ganglion cells. In contrast to the retinal projections of the cat, in which a specific ganglion cell type can project to different regions of the brain, each of the regions in this survey appears to receive inputs from its own distinct group of ganglion cells.

Animals↗
PubMed1995

The retinohypothalamic tract originates from a distinct subset of retinal ganglion cells.

The retinal ganglion cells giving rise to retinohypothalamic projections in the rat were identified using retrograde transport of horseradish peroxidase (HRP) or FluoroGold injected into the suprachiasmatic nucleus (SCN), and using transneuronal transport of the Bartha strain of the swine herpesvirus (PRV-Bartha). When PRV-Bartha is injected into one eye, it is taken up by retinal ganglion cells, replicated, transported to axon terminals in the SCN, and released. There the virus may take one, or both, of two paths to retinal ganglion cells in the contralateral eye: 1) uptake by SCN neurons, replication, and release from the neurons with uptake and retrograde transport in retinal afferents originating in the contralateral retina; 2) transneuronal passage through axo-axonic appositions between retinal afferents in the SCN with subsequent retrograde transport of virus to the contralateral retina. The ganglion cells thus labeled are a homogeneous population of small neurons (mean diameter, 12.8 +/- 2.2 microns and mean area, 81.8 +/- 21.8 microns 2) with sparsely branching dendrites that are widely distributed over the retina. This population is best identified when virus labeling of retinal projections in areas beyond the hypothalamus is eliminated by lateral geniculate lesions that transect the optic tract at its entry into the geniculate complex. The same population is labeled with retrograde tracers but, with both HRP and FluoroGold, other ganglion cells are labeled, presumably from uptake by fibers of passage, indicating that the virus is a more reliable marker for ganglion cells giving rise to retinohypothalamic projections. The ganglion cells identified correspond to a subset of type III, or W, cells.

Animals↗
PubMed2004

Target-derived and locally derived neurotrophins support retinal ganglion cell survival in the neonatal rat retina.

Brain-derived neurotrophic factor (BDNF) and neurotrophin-4/5 (NT-4/5) protein and mRNA are found in the neonatal rat retina and also in target sites such as the superficial layers of the superior colliculus. Both neurotrophins support neonatal retinal ganglion cell survival in vitro. In vivo, injections of recombinant BDNF and NT-4/5 reduce naturally occurring cell death as well as death induced by removal of the contralateral superior colliculus. In the latter case, the peak of retinal ganglion cell death occurs about 24 h postlesion. We wished to determine: whether a similar time-course of degeneration occurs after selective removal of target cells or depletion of target-derived trophic factors, and whether ganglion cell viability also depends on intraretinally derived neurotrophins. Retinal ganglion cell death was measured 24 and 48 h following injections of kainic acid or a mixture of BDNF and NT-4/5 blocking antibodies into the superior colliculus and 24 h after intraocular injection of the same antibodies. Retinotectally projecting ganglion cells were identified by retrograde labeling with the nucleophilic dye diamidino yellow. We show that collicular injections of either kainic acid or BDNF and NT-4/5 blocking antibodies significantly increased retinal ganglion cell death in the neonatal rat 24 h postinjection, death rates returning to normal by 48 h. This increase in death was greatest following collicular injections; however, death was also significantly increased 24 h following intravitreal antibody injection. Thus retinal ganglion cell survival during postnatal development is not only dependent upon trophic factors produced by central targets but may also be influenced by local intraretinal neurotrophin release.

Amidines↗
PubMed1996

Hypoxic and excitotoxic damage to cultured rat retinal ganglion cells.

The cytotoxic effects of hypoxia and excitatory amino acids on cultured retinal ganglion cells were studied. The influence of coculture with retinal Müller glia and cortical astrocytes on cell survival was evaluated, as were the effects of the N-methyl-DL-aspartate inhibitor, MK-801. Dissociated retinal neurons from 7-day-old Sprague-Dawley rats were plated on a laminin substrate, neocortex-derived glial monolayers, or Müller cell monolayers. Ganglion cells were labeled by injection of DiI into the superior colliculus 2 days prior to dissociation. Exposure of cultured ganglion cells to glutamate and N-methyl-DL-aspartate showed a time- and concentration-dependent survival rate. Exposure of cells to hypoxia demonstrated a survival rate that was dependent on time and O2 concentration. Excitotoxic and hypoxic damage was entirely blocked by the specific non-competitive inhibitor of N-methyl-DL-aspartate, MK-801. Retinal ganglion cells cultured on cortical astrocytes and retina-derived Müller glia showed significantly better survival rates (P < 0.001) than cells cultured on laminin-coated dishes under control conditions, in hypoxia (9% to 15% O2), and after exposure to 200 microM glutamate. Retinal ganglion cells cultured on Müller glia showed significantly better survival rates (P < 0.01) than those cultured on cortical astrocytes under conditions of hypoxia (9% to 15% O2) and exposure to 200 microM glutamate. The results demonstrate that excitotoxic and hypoxic damage to cultured retinal ganglion cells is moderated by NMDA receptor blockade and by the presence of glial cells, especially retinal Müller cells. This system may provide a useful model for studying the pathophysiology of excitotoxicity and hypoxia on cultured retinal ganglion cells, and may be used to help identify potentially clinically useful therapeutic agents.

Animals↗
PubMed2002

Phenytoin blocks retinal ganglion cell death after partial optic nerve crush.

Phenytoin is a well-characterized sodium channel blocker in widespread use as an anticonvulsant. In 1972, Becker and co-workers reported that phenytoin could reverse visual field loss from glaucoma. The authors therefore explored whether phenytoin could protect retinal ganglion cells from optic nerve crush. The optic nerve of Long-Evans rats was partially crushed; animals were given a single dose of either intraperitoneal phenytoin or vehicle. A third group underwent sham optic nerve crush. In a second set of experiments, the effect of phenytoin was compared to the N -methyl- D -receptor antagonist, memantine. Retinal ganglion survival was evaluated 1 week later. In addition, the effect of memantine and phenytoin on glutamate-induced intracellular calcium fluxes was evaluated.Phenytoin and memantine significantly reduced ganglion cell loss after optic nerve crush, and blunted the rise in intracellular calcium seen after administration of glutamate. Co-administration of the two agents, however, did not increase ganglion cell survival, and had no effect on ganglion cell calcium fluxes. Phenytoin can preserve retinal ganglion cells after partial optic nerve crush. This effect was not additive with a glutamate antagonist, suggesting that both agents alone are equally protective at saving the same population of ganglion cells at risk. In fact, the neuroprotective effect of the combined administration of phenytoin and memantine was significantly less than either of the two drugs alone. Phenytoin is known to decrease neuronal firing and neurotransmitter release; this may underlie its ability to serve as a neuro-protectant in this experimental paradigm.

Analysis of Variance↗
PubMed1986

The projection of different retinal ganglion cell classes to the dorsal lateral geniculate nucleus in the hooded rat.

The morphology of retinal ganglion cells which project to different parts of the dorsal lateral geniculate nucleus (DLG) in the hooded rat has been investigated. Small amounts of a retrograde tracer (horseradish peroxidase) were injected into the DLG, then labelled retinal ganglion cells were examined in retinal wholemounts. After injections into different parts of the DLG, differences were noted in the size, morphology and retinal distribution of labelled retinal ganglion cells. Specifically, after injections into the antero-ventral part of the DLG labelled retinal ganglion cells were spread sparsely across the retina, had large cell somas, and many were identified with Class I or Class III morphology. After injections into the postero-dorsal part of the DLG, labelled cells were more densely packed, had smaller somas, and more were identified with Class IIa and Class III morphology. The density of labelled cells was estimated to be no more than 37% of the total retinal ganglion cell density at any retinal position examined. These results show that in the rat, as in other species such as the cat or monkey, the terminals of different classes of retinal ganglion cells are segregated within different subdivisions of the DLG. However, unlike these other species, only a minority of the total retinal ganglion cell population projects to the DLG.

Animals↗
PubMed1984

Cell populations of the ganglion cell layer: displaced amacrine and matching amacrine cells in the pigeon retina.

The proportion and size distribution of ganglion and non-ganglion cells in the ganglion cell layer of different areas of the pigeon retina was examined in whole-mounts of the retina by retrograde axonal transport of horseradish peroxidase (HRP) from large brain injections. A maximum of 98% of cells were labelled in the red field and a maximum of 77% in the peripheral yellow field. Unlabelled cell bodies were 30% smaller than labelled ganglion cells and had a mean diameter of 6.2 microns and a size range of 4 to 9 microns. The morphology of cells in the ganglion cell layer was examined by Golgi staining of retinal whole-mounts. Small glia, displaced amacrine and ganglion cells were found. Displaced amacrine cell bodies were about 30% smaller than ganglion cells and their size distribution was similar to the unlabelled cells in HRP preparations. Displaced amacrine cells had small rounded cell bodies (mean diameter 6.2 microns) increasing in size with eccentricity, and a unistratified dendritic tree of fine, nearly radial, varicose dendrites in sublamina 4 of the inner plexiform layer. They had elliptical dendritic fields (mean diameter 66 micron) aligned parallel to the retina's horizontal meridian. A population of amacrine cells was found with somas at the inner margin of the inner nuclear layer and soma and dendritic morphology matching those of displaced amacrines. These amacrine cells had unistratified dendritic trees at the junction of sublaminae 1 and 2 of the inner plexiform layer. Pigeon displaced amacrine cells and their matching amacrines are similar to starburst cells of the rabbit retina.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

Large retinal ganglion cells in the rat: their distribution and laterality of projection.

The distributions of the ipsilaterally and contralaterally projecting large ganglion cells in the retina of the rat were determined, using the retrograde transport of Horseradish peroxidase (HRP) following injections into one optic tract. Labelled large retinal ganglion cells occur throughout the contralateral retina and throughout the temporal crescent of the ipsilateral retina, but there is a noticeable decrease in their density in the contralateral retina's temporal crescent. This retinal region was identified in these same retinae by injecting a retrogradely transported fluorescent tracer into the optic tract opposite that receiving the HRP. The density of large retinal ganglion cells increases in both the contralateral retina and the ipsilateral temporal crescent in the upper temporal periphery such that, together, these two populations of large cells combine to produce a peak density centred on the retinal representation of the visual field's vertical midline. This peak density of large retinal ganglion cells must therefore be further peripheral than the peak density for the total population of retinal ganglion cells, since all evidence indicates that the latter is positioned nasal to the vertical midline's representation. This was verified in one rat, in which the density distribution of the total population of retinal ganglion cells was determined and compared with the distribution of the large cell population. The results suggest that the rat possesses a specialized retinal focus of large ganglion cells for viewing the visual field directly in front of the animal.

Animals↗
PubMed1987

Freeze fracture and numerical analyses of the spiral ganglion cells.

The freeze-fracture technique was used to study the spiral ganglion cell population in the adult mouse. The majority of the ganglion cells (type I) had a smooth cell surface. Interspersed among these first ganglion cells, a small number of other ganglion cells (type II) showed considerable membrane specializations and were morphologically reminiscent of nerve terminals previously described only in human temporal bones. Calculations of the number of the two types of spiral ganglion cells in sectioned material showed that the adult mouse spiral ganglion comprises of 3%-4% unmyelinated type II ganglion cells.

Animals↗
PubMed1992

Beta-like ganglion cells in the South American opossum retina: a Golgi study.

Using the Golgi technique we investigated the morphology of the ganglion cells of the South American opossum retina. We focused our attention on a type of ganglion cell which has a relatively small dendritic field diameter and a medium-sized soma, making it a morphological equivalent of beta ganglion cells of cat retina. Both radial sections of the retina, where the stratification level of ganglion cells dendrites can be observed in the inner plexiform layer (IPL), and flat preparations of the retina, where the whole dendritic field of the ganglion cells can be examined and quantified, have been studied. Usually these cells have one to three primary dendrites, giving rise to short spiny branches. The dendrites of these cells are segregated in two groups, one with dendritic trees arborizing in the inner two thirds and another group arborizing in the outer third of the IPL. The two groups of beta-like cells probably represent the physiological ON- and OFF-center types of ganglion cell as found in cat retina. The mean cell body and dendritic field diameters of 47 cells were 18.5 +/- 1.6 microns, (size range 16-21 microns) and 91.5 +/- 16 microns (range 54-133 microns), respectively. Cell body and dendritic fields sizes were homogeneous across the retina of the opossum. In the opossum the relatively large dendritic fields of the beta-like ganglion cells in the area centralis are consistent with the poor visual acuity of this species.

Animals↗
PubMed1988

A morphometric study of the retinal ganglion cell response to optic nerve severance in the frog Rana pipiens.

This study examines the cell body response to axotomy of retinal ganglion cells in the frog Rana pipiens. Cell soma sizes were measured in carefully matched regions of Nissl-stained wholemounted retinae after either nerve crush, nerve cut with stump separation, nerve crush with intraocular nerve growth factor (NGF) or nerve cut with NGF applied to the proximal stump. The state of axonal regeneration was also assessed in each case by anterograde transport of HRP. Following nerve crush axons crossed the lesion by 7 days, reached the chiasma by 14 days and entered the tectum around 20-30 days. The normally evenly stained ganglion cells exhibited granular Nissl staining at 7 and 10 days but very little change in soma size. From 10 to 28 days the mean retinal ganglion cell area increased by 102% and maintained this size until at least 75 days. By 102 days soma size had nearly returned to normal. A population of displaced amacrine cells retained a normal appearance and soma size throughout regeneration. Following nerve cut and stump separation the retinal ganglion cells were slightly more reactive in appearance at 7 days after crush but otherwise the soma reaction developed in a similar manner. Axon tracing revealed no extension beyond the lesion site in these animals and therefore the state of axonal growth did not affect the early soma response. NGF applied at the time of the lesion had no detectable effect on the soma reaction. Although many retinal ganglion cells re-establish contact with visual centres after axotomy in the frog, a considerable proportion die. This contrasts with both the goldfish, where all cells regenerate successfully, and various mammals, where none do so and all retinal ganglion cells die. All retinal ganglion cells in the frog undergo reactive changes similar to those of goldfish and there is no sign of the cell shrinkage seen in mammals. Therefore the cell death in frog would appear to be different from that in mammalian retina but similar to that of mammalian peripheral nerve in which chromatolysis generally preceeds death.

Animals↗
PubMed1991

Regenerated synapses persist in the superior colliculus after the regrowth of retinal ganglion cell axons.

Synapse formation by retinal ganglion cell axons was sought in the superior colliculus of four adult rats 16-18 months after the optic nerve was transected and replaced by a peripheral nerve graft that guided regenerating RGC axons from the eye to the superior colliculus. The terminals of retinal ganglion cell axons were labelled by intravitreal injections of tritiated amino acids and studied by light and electron microscopic autoradiography. We found that (i) retinal ganglion cell axons had extended from the tips of the peripheral nerve grafts into the superior colliculus for approximately 350 microns; (ii) within the superior colliculus, some regenerated retinal ganglion cell axons became ensheathed by CNS myelin; (iii) retinal ganglion cell terminals formed asymmetric synapses with dendrites of neurons in the superficial layers of the superior colliculus, mainly the stratum griseum superficialis. Regenerated (n = 418) and normal retinal ganglion cell terminals (n = 1775) in the superior colliculus were compared in terms of their size (area, perimeter, and maximum diameter), contacts per terminal, contacts per 10 microns terminal perimeter, and post-synaptic structure contacted (dendritic spine, shaft, or soma). No statistically significant differences in the ultrastructural characteristics of the pre-synaptic profiles were apparent between the two groups. The post-synaptic structures contacted by axon terminals were similar in regenerated and control animals, although there were quantitative differences in the distributions of these contacts among dendritic spines and shafts. These results suggest that the regeneration of retinal ganglion cell axons in adult rats can lead to the formation of ultrastructurally normal synapses in the appropriate layers of the superior colliculus. The re-formed connections appear to persist for the life-span of these animals.

Animals↗
PubMed2002

Displaced retinal ganglion cells project to the accessory optic system in the chameleon ( Chamaeleo calyptratus).

Retinal ganglion cells were successfully labelled in the chameleon by retrograde axonal transport of dextran amines that were applied to the nucleus of the basal optic root (nBOR) in an in vitro preparation. Labelled ganglion cells were restricted to the contralateral eye. Many cells were completely stained including their dendritic trees. With few exceptions, all cells had displaced somata that were located at the inner margin of the inner nuclear layer. The labelled ganglion cells had two to six primary dendrites that branched frequently and formed large unistratified dendritic trees within sublamina 1 of the inner plexiform layer. There was extensive overlap of the dendritic trees of neighbouring cells leading to an estimated coverage factor of 2-4. The dendritic field areas varied in size according to the retinal position of the cells and were highest in the central retina around the fovea with a maximum of 0.14 mm(2) and reached a second maximum at the retinal margin with values of 0.08-0.1 mm(2). The smallest dendritic areas (0.04-0.06 mm(2)) were measured midway between the fovea and retinal margin. The size of the soma area was not correlated to the dendritic field size and increased from 100 to 150 microm(2) near the fovea to 150-300 microm(2) at the retinal margin. There was no evidence for a retinotopic organisation of ganglion cell fibres within the nBOR. All cells were of uniform morphology that was identical to the type of nBOR-projecting displaced ganglion cell (DGC) described previously for the bird retina. Similar to birds, the labelled DGCs were the only source of retinal projection to the nBOR. A small fraction of cells had orthotopic somata located in the ganglion cell layer but were otherwise identical to the labelled DGCs. The similarity of chameleon nBOR-projecting ganglion cells to those described in avian retinas mirrors the close phylogenetic relationship of birds and lizards.

Animals↗
PubMed2006

The clinico-anatomic explanation for tibial intraneural ganglion cysts arising from the superior tibiofibular joint.

OBJECTIVE: To demonstrate that tibial intraneural ganglia in the popliteal fossa are derived from the posterior portion of the superior tibiofibular joint, in a mechanism similar to that of peroneal intraneural ganglia, which have recently been shown to arise from the anterior portion of the same joint. DESIGN: Retrospective clinical study and prospective anatomic study. MATERIALS: The clinical records and MRI findings of three patients with tibial intraneural ganglion cysts were analyzed and compared with those of one patient with a tibial extraneural ganglion cyst and one volunteer. Seven cadaveric limbs were dissected to define the articular anatomy of the posterior aspect of the superior tibiofibular joint. RESULTS: The condition of the three patients with intraneural ganglia recurred because their joint connections were not identified initially. In two patients there was no cyst recurrence when the joint connection was treated at revision surgery; the third patient did not wish to undergo additional surgery. The one patient with an extraneural ganglion had the joint connection identified at initial assessment and had successful surgery addressing the cyst and the joint connection. Retrospective evaluation of the tibial intraneural ganglion cysts revealed stereotypic features, which allowed their accurate diagnosis and distinction from extraneural cases. The intraneural cysts had tubular (rather than globular) appearances. They derived from the postero-inferior portion of the superior tibiofibular joint and followed the expected course of the articular branch on the posterior surface of the popliteus muscle. The cysts then extended intra-epineurially into the parent tibial nerves, where they contained displaced nerve fascicles. The extraneural cyst extrinsically compressed the tibial nerve but did not directly involve it. All cadaveric specimens demonstrated a small single articular branch, which derived from the tibial nerve to the popliteus. The branch coursed obliquely across the posterior surface of the popliteus muscle before innervating the postero-inferior aspect of the superior tibiofibular joint. CONCLUSIONS: The clinical, MRI and anatomic features of tibial intraneural ganglion cysts are the posterior counterpart of the peroneal intraneural ganglion cysts arising from the anterior portion of the superior tibiofibular joint. These predictable features can be exploited and have implications for the pathogenesis of these intraneural cysts and treatment outcomes. These ganglion cysts are joint-related and provide further evidence to support the unifying articular theory. In each case the joint connection needs to be identified preoperatively, and the articular branches and the superior tibiofibular joint should be addressed operatively to prevent cyst recurrence.

Adult↗