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J Repérant

Publications and source records attributed to J Repérant.

At least 73 records · Page 4Linked to original sources
PubMed1993

Retrograde transneuronal transport of the fluorescent dye rhodamine beta-isothiocyanate from the primary and centrifugal visual systems in the pigeon.

The transneuronal labeling properties of the fluorescent dye Rhodamine beta-isothiocyanate (RITC) were investigated in the pigeon following the intraocular injection of the tracer either alone or in combination with kainic acid (RITC/KA). The RITC was transported bidirectionally from the eye producing both orthograde axonal and terminal labeling of the primary visual system (PVS) and retrograde labeling of the centrifugal visual system (CVS) comprising the n. isthmo-opticus (NIO) and associated ectopic neurons (EN) as well as the tractus isthmo-opticus (TIO). In addition, RITC-positive cell bodies were identified in layers 9/10 of the optic tectum, n. isthmi parvocellularis (Ipc) and the hyperstriatum accessorium (HA) subdivision of the telencephalic visual Wulst. In the RITC/KA experiments, the orthograde transport of the dye within the PVS was selectively suppressed and this coincided with the absence of somatic labeling in n. Ipc and HA. The results are explained in terms of transneuronal transport of RITC, involving the terminal uptake and subsequent retrograde axonal transport of the tracer within second-order neurons in n. Ipc and HA which project to the PVS and in tectal layers 9/10 projecting to the CVS. Moreover, the transneuronal transport of RITC, as demonstrated using the present experimental conditions, appears to be very specific and only labeled distant cell populations known to project to either the PVS or CVS.

Animals↗
PubMed1993

Presumptive GABAergic centrifugal input to the lamprey retina: a double-labeling study with axonal tracing and GABA immunocytochemistry.

The distribution of GABA-like immunoreactivity (GABA-LI) was performed in the lamprey retinopetal system which was previously identified by either anterograde or retrograde axonal tracing methods. This study was carried out at the ultrastructural level for the retina and under both the light and electron microscope for the mesencephalic retinopetal centers (M5 and RMA). The GABA-LI was distributed in about 40% of anterogradely HRP-labeled axon terminals in the inner retina. These made synaptic contacts upon either HRP-labeled ganglion cell dendrites or mostly on GABA-LI or on immunonegative amacrine cell dendrites and somata. The other immunonegative HRP-labeled axon terminals also established synaptic contacts on amacrine cell dendrites and somata. The mesencephalic retinopetal neurons, retrogradely labeled with HRP or [3H]proline, were GABA-LI in 65% of M5 somata and only in 15% of RMA neurons. M5 and RMA retinopetal neurons and dendrites, either GABA-LI or immunonegative, were contacted: (1) asymmetrically by HRP-labeled or unlabeled axon terminals containing rounded synaptic vesicles, always immunonegative and (2) symmetrically by HRP-unlabeled axon terminals containing pleiomorphic synaptic vesicles, which were either GABA-LI or immunonegative. The role of GABA as a putative neurotransmitter in the centrifugal visual system is discussed.

Afferent Pathways↗
PubMed1993

The primary visual system of flatfish: an evolutionary perspective.

The retinal projections of two species of flatfish (Scophthalmus maximus, Scophthalmidae; Platichthys flesus, Pleuronectidae) were investigated by autoradiography and by a HRP technique. Contralateral projections to five hypothalamic centres (area optica preoptica ventralis, nucleus opticus preopticus parvocellularis posterior pars lateralis, n. suprachiasmaticus, n. opticus hypothalami ventromedialis and area optica hypothalami posterior), thirteen thalamo-pretectal centres (nucleus opticus dorsolateralis (partes medialis, ventralis and lateralis), n. opticus ventrolateralis, n. opticus commissurae posterioris (partes dorsalis and ventralis), n. opticus accessorius, n. geniculatus lateralis mesencephali, nn. opticus pretectalis dorsalis, medialis and ventralis and n. corticalis), three layers of the optic tectum (stratum opticum pars externa, stratum fibrosum et griseum superficiale, stratum album centrale), and a single target in the tegmentum (n. opticus tegmenti mesencephali dorsalis), were identified in both species. Interspecific variation of the contralateral visual projections is relatively small. Ipsilateral visual projections of fibres which recross the midline in the minor and transverse commissures were also identified; in S. maximus this ipsilateral contingent is poorly developed and concerns principally hypothalamic structures, while in P. flesus the ipsilateral projections are considerably more extensive and involve both hypothalamic and thalamo-pretectal primary visual centres. No differences in the projections from the fixed and from the migrated eye were observed in either species. The findings are discussed in the general context of the existing literature on the visual projections of teleosts, in an attempt to characterize the primary visual system of the Pleuronectiformes in an evolutionary context.

Animals↗
PubMed1993

Dopaminergic interplexiform cells in the retina of pigmented and hypopigmented quails (Coturnix coturnix japonica).

Interplexiform cells (IPCs) have not been previously described as a component of the population of tyrosine hydroxylase (TH) immunoreactive (presumably dopaminergic) cells in the avian retina. In this study, carried out in both pigmented and imperfect albino mutant quails (Coturnix coturnix japonica), we initially describe TH immunoreactive cells in the inner nuclear layer whose internal dendritic arborization extends into strata 1, 3 and 4/5 of the inner plexiform layer. Then, we describe ascending processes arising from the somata or proximal dendrites of these cells. These sclerally directed processes (100-1,000 microns long) run across the inner nuclear layer to terminate within the outer plexiform layer, sometimes even reaching the outer nuclear layer. Hence, the cells bearing such processes correspond well with the definition of IPCs. The number of scleral processes is higher in mutant (48 +/- 19/retina) than in normal (12 +/- 10/retina) quails and are distributed throughout the retina except the area surrounding the pecten. Comparison of biochemical assays for dopamine in the two strains reveals a significantly higher dopamine content in the mutant quails which could be related to its increased number of dopaminergic IPC processes.

Animals↗
PubMed1993

The embryological development of primary visual centres in the turtle Emys orbicularis.

The development of the primary visual centres was studied in a series of embryos of the turtle, Emys orbicularis, incubated at 25 degrees C. The differentiation of both visual and nonvisual diencephalic and mesencephalic structures takes place entirely within the 2nd quarter of the period of incubation; this finding appears to be consistent with previous descriptions of the embryology of 2 other chelonian species, Lepidochelys and Chelydra. Two successive waves of migration, each dividing into internal and external sheaves, are involved in the formation of the structures of the diencephalon and mesencephalon. The primary visual centres, which comprise 2 hypothalamic, 5 thalamic and 5 pretectal zones of retinal projections, together with the 2 superficial layers of the tectum and a single tegmental projection zone, all have their origin in the external sheaf of the 1st wave of migration. The finding that the adult nucleus geniculatus lateralis dorsalis, pars ventralis arises from one of the migrations of the dorsal thalamus is discussed in the context of the debate over the possible homologues of the mammalian geniculostriate visual pathway.

Animals↗
PubMed1992

Presumptive GABAergic feedback input to the frog olfactory bulb: a double labelling study with retrograde axonal tracing and GABA immunohistochemistry.

The localization of gamma-aminobutyric acid (GABA)-immunoreactive neurons that project to the main olfactory bulb in the frog was studied by combining GABA immunohistochemistry with retrograde axonal tracing. Double-labelled neurons were observed in the dorsal, medial and lateral pallial areas involved in reciprocal connections with the main olfactory bulb. GABA-immunoreactive cell bodies constituted only a part of the population of bulbopetal neurons in each pallial region. This suggests that bulbopetal neurons in the frog pallium belong to neuronal populations which differ in their neurotransmitter specificities. The bulbopetal GABA-immunoreactive pallial neurons may be the source of GABAergic feedback input to the frog main olfactory bulb.

Animals↗
PubMed1992

A reconsideration of the primary visual system of the turtle Emys orbicularis.

The retinocerebral projections of Emys orbicularis were investigated by means of [3H]-proline or HRP, administered by intraocular injection. Two newly-hatched, two juvenile and seven adult specimens were examined. The results reveal contralateral retinal projections to fifteen sites: two in the hypothalamus (the nuclei suprachiasmaticus and periventricularis), five in the thalamus (the nuclei ovalis, geniculatus lateralis ventralis, geniculatus laleralis dorsalis, dorsolateralis anterior and ventrolateralis), five in the pretectal region (the nuclei geniculatus pretectalis, opticus pretectalis ventrolateralis, lentiformis mesencephali, posterodorsalis and griseus tectalis), two in the optic tectum (the stratum opticum and the stratum fibrosum et griseum superficiale), and one in the tegmentum (the nucleus opticus tegmenti). Ipsilateral projections to nine of these sites at thalamic, pretectal, tectal and tegmental levels, while weak, could be clearly demonstrated. These results differ considerably from those obtained in a previous investigation using a Nauta-paraffin technique; it is suggested that the differences are due to limitations of the latter technique. A review of the existing literature on the Chelonian primary visual system reveals considerable terminological diversity, and a standard nomenclature for the primary visual centres of turtles is proposed.

Afferent Pathways↗
PubMed1991

Divergence and collateral axon branching in subsystems of visual cortical projections from the cat lateral posterior nucleus.

The projections from the lateral (LPl), intermediate (LPi) and medial (LPm) subdivisions of the cat lateral posterior nucleus (n. LP) to visual areas 17, the posteomedial (PMLS) and posterolateral (PLLS) lateral suprasylvian and anterior ectosylvian (AEV) were studied using the retrograde labeling technique following concomitant injections of fluorescent dyes (Fast blue, Nuclear yellow, Evans blue and Rhodamine beta-isothiocyanate) into the different cortical loci. The results showed a medial-lateral topographical reversal of the visual n. LP-cortical connections: The ventral portion of LPl projects to area 17 whereas more dorsolateral regions of LPl and lateral LPi provide input to PMLS. Cells in medial LPi project mainly to the PLLS cortex and AEV receives afferents from the LPm. Areas of overlap were identified within the ventral LPl which projects to both area 17 and PMLS and within the LPi/LPm border region at the origin of connections to both PLLS and AEV. Furthermore, some single neurons within the areas of overlap were found to be double-labeled indicating divergent projections to their respective cortical targets via collateral axon branching. The data show that divergence and axonal branching are common features of the different n.LP-visual cortical subsystems and support the notion of the existence of families of thalamo-cortical systems which are distinct in their connection patterns and underlying functional properties.

Animals↗
PubMed1990

Reorganization of GABAergic synapses in the viper optic tectum following retinal deafferentation.

The immunocytochemical analysis of the viper optic tectum was carried out with an anti-gamma-aminobutyric acid (anti-GABA) antiserum following retinal deafferentation for survival times ranging from 10 to 90 days. The ultrastructure of the SGFS neuropil revealed that among the two types of axon terminals, namely pleiomorphic (P) and spherical (S) boutons, a subtype of the latter (S2), corresponding to the retinal terminals, was found to degenerate at varying rates. In most cases, this resulted in the glial engulfment of the presynaptic partner, leaving the postsynaptic differentiation free (FPSD). Beyond the two first months, the asymmetrical freed postsynaptic differentiations (FPSDs) were progressively and partly reafferented by GABA-positive P axon terminals through a sliding process. Three months postoperative, the number of GABA-positive P axon terminals which, in normal animals, establish asymmetrical contacts (1-2%), was found to increase to approximately 10%. The postsynaptic differentiation may represent a mismatched receptor area for the new competing presynaptic partners. The functional implications of such 'axonal terminal sprouting' are discussed.

Afferent Pathways↗
PubMed1990

Projections of the dorsolateral anterior complex and adjacent thalamic nuclei upon the visual Wulst in the pigeon.

The distinctive patterns of thalamic input to the rostral (R), intermediate (I) and caudal (C) divisions of the pigeon Wulst were determined using the retrograde multiple label technique following concomitant injections of various fluorescent tracers into different Wulst loci. The results showed topographical projections from components of the visual thalamic n. dorsolateralis anterior complex. Major ipsilateral and contralateral projections upon the R and I Wulst stem from the pars lateralis ventralis and dorsalis nuclei, respectively. The nuclei pars lateralis rostralis, pars magnocellularis and n. suprarotundus provide weak bilateral projections to all of the Wulst divisions sampled. Lastly, bilateral connections from the n. superficialis parvocellularis upon I and C, and from n. dorsolateralis posterior upon the posterior C Wulst were also demonstrated. Based upon their patterns of terminal distribution upon the Wulst, some of these thalamic nuclei are compared to specific components of the mammalian geniculate and extrageniculate visual systems.

Animals↗
PubMed1990

Localisation of GABA-immunopositive cells in the river lamprey spinal cord.

Using the immunohistochemical PAP method GABA-immunopositive cells were revealed in horizontal and transverse sections of lamprey spinal cord. The most numerous intensively stained small oval cells were located in the dorsal part of the spinal cord. The larger cells with 2-3 long nonbranching processes were located at the border of lateral column, the main part of which is composed of GABA-immunonegative cells. Some of the largest, but less intensively stained cells were observed in the lateral part of the spinal cord beyond the cell column and in the ventrolateral corner of transverse sections. The latter are identified as previously described edge cells. Functional identification of the remaining GABA-immunopositive cells is rather difficult. Some of them may be glial elements.

Animals↗
PubMed1990

An experimental study of the retinal projections of the European eel (Anguilla anguilla), carried out at the catadromic migratory silver stage.

A radioautographic study of the European eel (Anguilla anguilla) was carried out in ten female specimens at the catadromic migratory silver stage. Terminal arborizations of contralaterally projecting visual fibres were identified in ten hypothalamic structures (area optica preoptica ventralis and the nuclei suprachiasmaticus, opticus hypothalamicus ventromedialis, preopticus magnocellularis lateralis, posterioris lateralis, posterioris dorsalis periventricularis posterioris dorsalis lateralis, posterioris dorsalis medialis, posterioris ventralis lateralis, and posterioris ventralis periventricularis), ten thalamo-pretectal structures (Areas C1 and C2, area optica tractus opticus ventrolateralis and the nuclei dorsolateralis thalami, ventrolateralis thalami pars ventralis, opticus ventralis thalami, geniculatus lateralis, opticus pretectalis partes dorsalis et ventralis, and opticus commissurae posterioris), and in the tectal strata opticum partes externa et interna, fibrosum et griseum superficiale, griseum centrale and album centrale. An accessory optic system was identified, and a contralateral retinal projection to the anterior region of the anterior semicircular torus (n. opticus dorsolateralis mesencephali) was identified. Ipsilateral projections to hypothalamic and thalamopretectal structures were also observed. Apart from the retinal projection to the preoptic area, which is exceptionally important in the silver eel, the general plan of organization of the primary visual centres of this form is comparable to that described in other species of teleost. However, the architecture of some primary visual centres shows characteristics similar to those described in more primitive Actinopterygians.

Anguilla↗
PubMed1990

Regeneration of the retinotectal system in a flatfish, Scophthalmus maximus L.

Regenerating retinotectal fibres were visualized by radioautography in turbots (Scophthalmus maximus L.) maintained at 10 degrees-14 degrees C either after crushing one optic nerve or after crushing one nerve and removing the contralateral eye. Regeneration was found to be more extensive 2 days after crushing the right optic nerve than after crushing the left and was further enhanced by contralateral enucleation. The difference between experimental groups was markedly less pronounced by 113 days postoperatively and by 293 days the specimens resembled normal material. Between 113 and 222 days, a transient projection to the ipsilateral tectum was found, which disappeared by 293 days whether or not the contralateral eye had been removed. The differences between the present results and previous findings in symmetrical Cyprinid fish are discussed.

Animals↗
PubMed1989

Centrifugal innervation of the lamprey retina. Light- and electron microscopic and electrophysiological investigations.

Centrifugal fibers and their synaptic connections were studied in retinas of the lamprey Lampetra fluviatilis. The morphological analysis of retinofugal and retinopetal elements was performed after their horseradish peroxidase (HRP) filling through either the cut optic nerve in isolated retina preparations or after intracerebral HRP injections. In flat-mounted retinas, labeled ganglion cell bodies with their dendritic arborizations as well as centrifugal axons were found. The topography of labeled ganglion cell bodies and fibers in semi-thin plastic sections is described. The electron microscopic analysis revealed that the centrifugal terminals synapse either upon unlabeled somata or profiles containing synaptic vesicles (PCSVs). In more rare cases these boutons seem to establish synaptic contacts on ganglion cell dendrites. The target cell bodies were located within the inner part of the inner nuclear layer, whereas postsynaptic dendrites and PCSVs were mainly observed in the outer portion of the internal synaptic layer. Stimulation of the optic nerve in isolated retinas produced antidromic responses in 23 neurons and in 9 of these cells, an antidromic spike was followed by a postsynaptic potential (PSP). Ten cells yielded no antidromic response, but showed PSPs sometimes associated with spikes. The morphological and physiological evidence obtained indicate that these PSP-generating cells were activated synaptically by centrifugal fibers and that in the lamprey retina, these fibers make contacts either with dendrites or somata of amacrine cells and probably with ganglion cell dendrites.

Animals↗
PubMed1989

A preliminary description of the regeneration of optic nerve fibers in a reptile, Vipera aspis.

Crushing or freezing the optic nerve of the viper leads initially to the anterograde degeneration of the optic nerve fibers and to an extensive retrograde demyelination process associated with the degeneration of some retinal ganglion cells. By the 45th postoperative day, regenerating unmyelinated axons can be identified in the damaged region of the optic nerve. These fibers reach the chiasm and the marginal optic tract by the third postoperative month. The radioautographic tracing method shows that some nuclei of the primary visual system begin to be reinnervated by about the 5th postoperative month; this reinnervation was not, however, completely restored in those specimens with the longest postoperative survival of 220 days.

Animals↗
PubMed1989

The optic nerve of the viper, Vipera aspis.

A quantitative investigation of the optic nerves of eight adult vipers was carried out, both at the level of resolution of the light microscope by stereological methods, and at the level of resolution of the electron microscope. The majority (87%) of axons are myelinated, and the fibers are organized in fascicles; each bundle of axons is disposed around a central column of glial cells of which the greater proportion (62%) are oligodendrocytes, 33% are astrocytes and the remaining 5% are microglial cells. Estimations of the total number of fibers varied, from 5.37 X 10(4) to 6.96 X 10(4), among the eight specimens. The distribution of diameters of myelinated fibers is well characterized (chi 2 = 16.84, df = 22, 0.9 greater than p greater than 0.5) by a three-parameter lognormal distribution with a mean of 0.735 micron, standard deviation of 0.239 micron, and origin of 0.21 micron. Axon diameter is linearly related (r = 0.60) to the number of electron-dense layers in the myelin sheath. The diameters of unmyelinated fibers are distributed (chi 2 = 1.95, df = 4, 0.9 greater than p greater than 0.5) as a two-parameter lognormal distribution with mean of 0.25 micron and standard deviation of 0.067 micron. A surprisingly large number of myelinated fibers, apparently dispersed at random throughout the nerve, showed anomalies of myelination; two possible explanations, between which it is impossible to discriminate on the basis of the available data, are offered for this state of affairs.

Animals↗