Biomedical subjects

J Repérant

Publications and source records attributed to J Repérant.

At least 37 records · Page 2Linked to original sources

PubMed2000

A light and electron microscopic study of taurine-like immunoreactivity in the main olfactory bulb of frogs.

The distribution of taurine in the frog olfactory bulb was studied using light and electron microscopic immunohistochemical techniques. At the light microscopic level, taurine-like immunoreactivity (taurine-LI) was found in (i) fibers coursing from the olfactory nerve layer to the glomerular layer, (ii) cell bodies and processes primarily located in the caudal part of the granule cell layer (GCL), and (iii) puncta outlining unstained somata of mitral cells and cells in the GCL. In consecutive sections processed for taurine or GABA, numerous cells of the caudal GCL displayed taurine-LI and GABA-like immunoreactivity (GABA-LI). A bimodal distribution of the cross-sectional cell area for GABA-LI cells implied their morphological diversity, and the peak for larger GABA-LI cells coincided with the maximum for taurine-LI cells. At the electron microscopic level, single immunogold labeling showed that GABA-LI, but not taurine-LI, is present in granule cells, whereas both taurine-LI and GABA-LI were localized in a 'non-granule' type of cell. The double labeling procedure demonstrated coexistence of taurine-LI and GABA-LI in neurons of a 'non-granule' type. These cells had some ultrastructural features typical of short axon cells in the GCL of the mammalian olfactory bulb and were tentatively considered as short axon-like cells. Results suggest that, in the frog olfactory bulb, taurine is contained in primary olfactory afferents and short axon-like cells of the GCL co-localizing GABA and taurine.

Animals↗

PubMed1999

Functional anatomy of the avian centrifugal visual system.

Although first described over a century ago, the centrifugal visual system (CVS) projecting to the retina still remains somewhat of an enigma with regard to its functional role in visually-guided behavior. The highly developed avian CVS has been the most extensively investigated and the anatomical organization of its two component centrifugal structures, the n. isthmo-opticus (NIO) and ectopic neurons (EN), including its afferent brainstem projections is reviewed. The results of double-labeling studies combining axonal tracing techniques and immunohistofluorescence have demonstrated GABA immunoreactivity (-ir) of interneurons within the neuropilar zone of the NIO, choline acetyltransferase (ChAT)-ir and nitric oxide synthase (NOS)-ir in the centrifugal cells of the NIO and EN as well as in the afferent projection neurons of layers 9/10 of the optic tectum. The data are discussed in terms of neurochemical and excitatory/inhibitory mechanisms within the different components of the avian CVS in relation to hypotheses which have implicated this system in visual attention and ground-feeding behavior.

Animals↗

PubMed1999

Retinal projections in two crocodilian species, Caiman crocodilus and Crocodylus niloticus.

The retinal projections of Caiman crocodilus and Crocodylus niloticus were investigated by means of the orthograde axonal transport of either rhodamine beta-isothiocyanate or tritiated proline. In these two species, each tracer revealed contralateral retinal projections to three hypothalamic regions (subventricular gray matter, nucleus suprachiasmaticus, and area optica hypothalami lateralis), five thalamic regions (nuclei ovalis, dorsolateralis anterior, ventrolateralis and ventrobasalis, and lateral geniculate complex, of which six subcomponents can be distinguished), six pretectal regions (nuclei posterodorsalis, lentiformis mesencephali, griseus tectalis, geniculatus pretectalis, area optica commissurae posterior and area optica pretectalis lateroventralis), six outermost layers of the optic tectum, and the nucleus opticus tegmenti. Weak ipsilateral retinal projections have been observed in two hypothalamic nuclei and in the nucleus opticus tegmenti. Comparative analysis with other data show that the contralateral retinal projections of crocodiles are considerably more reptilian than avian. Moreover, crocodiles share with birds an extremely poor contingent of ipsilateral retinal projections.

Alligators and Crocodiles↗

PubMed1999

An investigation of astroglial morphology in torpedo and scyliorhinus.

The distribution and morphology of GFAP-immunoreactive cells was investigated in two elasmobranch species, Scyliorhinus canicula and Torpedo marmorata, in an attempt to distinguish between Horstmann's (1954) hypothesis that the presence of cells resembling mammalian astrocytes is a function of the thickness of the ventricular walls, and Cajal's (1911) hypothesis that astrocytes are a phylogenetic novelty found only in birds and mammals. Two types of GFAP-reactive elements were observed, but the distribution of these differed markedly between the two species. In Scyliorhinus, radial glial cells were predominant and astrocytes relatively rare. In Torpedo, on the other hand, a species in which the ventricles are atrophied and the ventricular walls extremely thick, the overwhelming majority of GFAP-labelled structures strongly resembled astrocytes; occasionally, GFAP-positive cells were observed in the ependyma of the spinal cord. These findings, together with previous results obtained by others in hagfish, provide strong evidence in favour of Horstmann's hypothesis.

Animals↗

PubMed1999

[The colocalization of neurotransmitters in the presynaptic boutons of inhibitory synapses in the lamprey spinal cord].

Using the electron microscopy immunocytochemistry, the GABA and glycine immunoreactivity was studied in presynaptic axon terminals of the spinal cord central gray in the lamprey Lampetra fluviatilis. All immunopositive presynaptic terminals contacting motoneurones or non-identified post-synaptic profiles were divided into only GABA- (44%), only glycine-immunopositive terminals (26%), and both GABA- and glycine-containing terminals (30%). The glycine-immunopositive axon terminals contained flattened synaptic vesicles. Large dense core vesicles were co-localised with conventional synaptic vesicles in 74% of GABA-containing presynaptic terminals.

Animals↗

PubMed1998

Lamprey ganglion cells contact photoreceptor cells.

Lamprey retinal ganglion cells are localized in two separate layers: those close to the vitreous and those at the junction between the inner nuclear and inner plexiform layers, including some others in the inner nuclear layer, close to the photoreceptor cell layer. Whereas most ganglion cell dendrites arborize in the inner plexiform layer and contact amacrine, bipolar and retinopetal cell profiles, some of them, located in the inner nuclear layer, ascend radially through the outer plexiform layer and establish contacts with photoreceptor cells. This ganglion cell type might correspond to the biplexiform ganglion cells already described in gnathostome vertebrate species and could provide a fastforward signal from photoreceptors to ganglion cells, bypassing the usual bipolar cell interneuron.

Animals↗

PubMed1998

Recoverin and hippocalcin distribution in the lamprey (Lampreta fluviatilis) retina.

Recoverin is a calcium-sensing protein which is involved in the transduction of light in vertebrate photoreceptors. It is also detected in other retina cell types in which its function is not yet elucidated, and is an autoantigen in a cancer-associated degenerative disease of the retina. Recently, hippocalcin, an homologous protein of recoverin, belonging to the same family of fatty acylated EF-hand calcium binding proteins was described in mammals. The immunohistochemical studies presented in this paper demonstrate, that, in the retina of the lamprey, an Agnathan considered the living ancestor of actual jawed vertebrates, recoverin was present in all photoreceptors and, to a lesser extent in subpopulations of amacrine and ganglion cells whereas hippocalcin was detected in numerous amacrine and ganglion cells and in the inner segments of long photoreceptors. The existence of these calcium-binding proteins shows that they have a high degree of conservation during evolution. Their presence in the same cells that in jawed vertebrates (photoreceptors and ganglion cells for recoverin; amacrine and ganglion cells for hippocalcin) suggests that some retinal functions are well conserved but because they were also found in different cell types than in other species (amacrine for recoverin; photoreceptors for hippocalcin), they may have functions more specific to the lamprey retina.

Animals↗

PubMed1998

Expression of Kin, a nuclear protein binding to curved DNA, in mammal and avian brains.

Kin is a nuclear protein which presents cross-immunoreactivity with the bacterial RecA protein and which efficiently binds to curved DNA. This genomic interaction could be implied in DNA repair and illegitimate recombination in eukaryotic cells. Using immunocytochemistry with anti-RecA antibodies, we report the ubiquitous presence of the Kin protein in the CNS of mice and quails. However, some brain structures such as the hippocampal area, the locus coeruleus and Purkinje cells are preferentially immunolabelled and show some homologies between the two species. In conclusion, the expression of the Kin protein is preserved in the phylogeny of the brain of higher vertebrates.

Animals↗

PubMed1998

Retinal and cortical afferents to the dorsal lateral geniculate nucleus of the turtle, Emys orbicularis: a combined axonal tracing, glutamate, and GABA immunocytochemical electron microscopic study.

The dorsal lateral geniculate nucleus (GLd) of the turtle Emys orbicularis has been analyzed with axonal tracing methods and immunocytochemical techniques for glutamate (GLU) and gamma-aminobutyric acid (GABA), in combination with a quantitative study of the morphologic characteristics, distribution, and synaptology of the retinofugal and corticofugal terminals. Ultrastructural observations show that the vast majority of retinal terminals (Rtr) have clear, rounded synaptic vesicles and account for 16% of all profiles containing synaptic vesicles (PCSV). Their synaptic index (0.5) is low, and they make three times more contacts with the dendrites of projection cells than with those of interneurons. A low proportion of retinal terminals of a second category contain pleomorphic synaptic vesicles and are highly GABA immunoreactive. Axon terminals, unlabeled after intraocular injection of the tracer (SR), smaller in size and with more rounded clear synaptic vesicles, longer synaptic differentiations, and higher synaptic index than Rtr terminals, account for 19.7% of all PCSV and make asymmetric synaptic contacts with large dendrites of projection cells and less with the dendrites of interneurons. Some SR have been unambiguously identified as corticofugal terminals (Cg), either after cortical injection of the tracer (16%) or cortical lesion (37%). Retinal and Cg/SR terminals are spatially segregated within the GLd. Both are highly GLU immunoreactive, with the highest density of labeling over synaptic vesicles, suggesting that these terminals may use GLU as neurotransmitter. The level of GLU immunoreactivity of GABA-positive profiles is half that of Rtr and Cg/SR terminals and is greatest over mitochondria, possibly reflecting the 'metabolic' pool of GLU that serves as a precursor in the formation of GABA.

Afferent Pathways↗

PubMed1998

Evidence for co-existence of CCK-8 and GnRH in neurons of the mesencephalic tegmentum in the chameleon.

A double-label immunofluorescence technique was used to demonstrate the co-localization of cholecystokinin-8 (CCK-8) and gonadotrophin-releasing hormone (GnRH) in individual neurons and processes of the chameleon brain. Co-localization was limited to a small population of cells in the dorsomedial tegmentum; in other regions of the brain, neurons were observed to be either CCK-8-immunopositive or GnRH-immunopositive but never both. However, double-labeled fibers and terminals were found to be distributed at a low density throughout the thalamus, the medial hypothalamus, the tegmentum and the spinal cord. These data provide the first indication for the co-localization of CCK-8 and GnRH, whose functional significance remains to be established. ON

Animals↗

PubMed1998

An immunohistochemical study of putative neuromodulators and transmitters in the centrifugal visual system of the quail (Coturnix japonica).

The aim of the present study was to analyze the neurochemical properties of the centrifugal visual system (CVS) of the quail using an immunohistochemical approach by testing 16 neuropeptides (angiotensin: ANG, bradykinin: BK, cholecystokinin, dynorphin, L and M-enkephalin, beta-endorphin: beta-END, galanin, alpha-neoendorphin, neurokinin A, neuropeptide Y (NPY), ocytocin, somatostatin, substance P, vasopressin, vasoactive intestinal polypeptide) and three neurotransmitters or their synthetic enzymes (choline acetyltransferase: ChAT, tyrosine hydroxylase: TH, serotonin: 5-HT and nitric oxide synthase: NOS, including the histochemical nicotinamide adenine dinucleotide phosphate diaphorase technique). For each substance, the somatic and afferent fiber and terminal labeling was analyzed within the nucleus isthmo-opticus (NIO) and the ectopic area (EA) and compared with that of retinopetal cell bodies labeled retrogradely with RITC following its intraocular injection (double-labeling procedure). The results showed that none of the centrifugal neurons were reactive to any of the substances tested. In contrast, all with the exception of ANG, BK and beta-END, labeled fibers and terminals within the EA and only four (ChAT, 5-HT, NPY and NOS) within the NIO. Possible sources of these immunoreactive fibers terminating in the NIO and EA were investigated by mapping the somatic immunolabeling of the different substances within brainstem regions previously shown by Miceli and other authors to project upon the centrifugal neurons. The data suggests that, besides the rapid retino-tecto-NIO-retinal loop, which facilitates the transfer of meaningful or more relevant information within particular portions of the visual field, the multiple afferent input which stems from various brainstem regions utilizes a wide range of neuroactive substances. Some of these afferent projections upon the centrifugal neurons appear to belong to nonspecific systems which might play a role in modulating the excitability of centrifugal neurons as a function of arousal.

Animals↗

PubMed1998

Day and night dysfunction in intraretinal melatonin and related indoleamines metabolism, correlated with the development of glaucoma-like disorder in an avian model.

As previous studies have suggested that melatonin and serotonin may be involved in the regulation of intraocular pressure, retinal concentrations of melatonin, 5-HT, and related indoleamines measured at day and at night were studied during the development of a glaucoma-like disorder with increased intraocular pressure in the al mutant quail. Indoleamine levels were determined by HPLC with electrochemical detection in 1-month-, 3-month-, and 7-month-old al mutant and control quails. Morphology and numbers of melatonin-synthesizing and 5-HT-containing cells, labelled immunohistochemically with an anti-hydroxyindol-0-methyltransferase (HIOMT) antibody and an anti-5-HT antibody, respectively, were studied. Major findings were that: (1) no significant changes in morphology of melatonin-synthesizing cells or in the morphology and density of 5-HT-containing amacrine cells were observed during the development of glaucoma: (2) 5-HT metabolism was modified during the night at 1 month of age and during the day after 3 months; and (3) melatonin metabolism was modified during the night at 7 months and during the day after 3 months. These results demonstrate a relationship between the temporal evolution of this avian glaucoma and a dysfunction in indoleamine retinal metabolism.

Acetylserotonin O-Methyltransferase↗

PubMed1998

Expression of the Emx-1 and Dlx-1 homeobox genes define three molecularly distinct domains in the telencephalon of mouse, chick, turtle and frog embryos: implications for the evolution of telencephalic subdivisions in amniotes.

Homologies between vertebrate forebrain subdivisions are still uncertain. In particular the identification of homologs of the mammalian neocortex or the dorsal ventricular ridge (DVR) of birds and reptiles is still a matter of dispute. To get insight about the organization of the primordia of the main telencephalic subdivisions along the anteroposterior axis of the neural tube, a fate map of the dorsal prosencephalon was obtained in avian chimeras at the 8- to 9-somite stage. At this stage, the primordia of the pallium, DVR and striatum were located on the dorsal aspect of the prosencephalon and ordered caudorostrally along the longitudinal axis of the brain. Expression of homeobox-containing genes of the Emx, Dlx and Pax families were used as markers of anteroposterior developmental subdivisions of the forebrain in mouse, chick, turtle and frog. Their expression domains delineated three main telencephalic subdivisions in all species at the onset of neurogenesis: the pallial, intermediate and striatal neuroepithelial domains. The fate of the intermediate subdivisions diverged, however, between species at later stages of development. Homologies between forebrain subdivisions are proposed based on the conservation and divergence of these gene expression patterns.

Animals↗

PubMed1997

Differential glutamate immunoreactivity in glial cells of the retino-recipient layer of the viper optic tectum following retinal ablation. A quantitative EM immunogold study.

In normal conditions, retino-tectal terminals are densely glutamate-immunoreactive. During the degenerative process of these terminals, a significant increase of glutamate immunoreactivity has been exclusively observed in microglial cells. It is suggested that this phenomenon is consecutive to the synthesis of glutamate by these cells after their activation by degenerating optic terminals.

Animals↗

PubMed1997

Immunocytochemical localization of dopamine and its synthetic enzymes in the central nervous system of the lamprey Lampetra fluviatilis.

The distribution of dopamine (DA)-containing cell bodies, fibers, and terminals in the brain and spinal cord of Lampetra fluviatilis was investigated by immunohistochemical means. In order to distinguish dopaminergic neurons from those using other catecholamines as the primary neurotransmitter, the distribution of dopamine-immunoreactive structures was compared to that of cell bodies, fibers, and terminals labelled with antibodies directed against the enzymes tyrosine hydroxylase (TH), aromatic L-amino acid decarboxylase (AADC), dopamine beta-hydroxylase (DBH), and phenylethanolamine-N-methyl transferase (PNMT). We define dopaminergic neurons as those that are simultaneously DA, TH, and AADC immunoreactive and at the same time DBH and PNMT nonreactive. The overall concentrations of dopamine, noradrenaline, and adrenaline and some of their metabolites were also measured via high-performance liquid chromatography of whole-brain extracts. Our results revealed the presence of 10 populations of dopaminergic neurons in the brain of the lamprey in the olfactory bulb, preoptic area, hypothalamus, rhombencephalon, and spinal cord. In addition, uniquely DA-immunoreactive neurons, in contact with the cerebrospinal fluid, were observed in the hypothalamus and spinal cord. Chromatography indicated that dopamine exists in considerably higher concentrations than noradrenaline in the lamprey brain, whereas adrenaline is absent, the latter finding being supported by our failure to observe any PNMT-immunoreactive cell bodies, fibers, or terminals. The dopaminergic system of the lamprey appears to share many features not only with that of other anamniotes but also with that of amniotes; however, as in teleosts, dopaminergic neurons in the midbrain corresponding to the substantia nigra, the retrorubral area, and the ventral tegmental area of other species do not exist in the lamprey.

Animals↗

PubMed1997

Cholecystokinin-like systems in the chameleon brain.

Immunohistochemical techniques were used to determine the distribution of cholecystokinin-8 (CCK8) immunoreactivity in the brain of the chameleon. In the telencephalon, CCK8-immunopositive somata were sparse and observed principally in the olfactory tubercle at the ventromedial edge of the rostral telencephalon and in the medial septum. Immunopositive fibers were observed mainly in the medial septal region and the ventral telencephalon. In the diencephalon, numerous CCK8-reactive fibers were densely concentrated in the periventricular region, the dorsolateral hypothalamus and the external zone of the median eminence. In the thalamus, labelled fibers were restricted to the peri-rotundal nuclei and the lateral part of the habenula. Immunoreactive cell bodies were observed in the medial part of the dorsal lateral geniculate nucleus, in the periventricular, ventral and lateral regions of the hypothalamus. In the mesencephalon, the densest accumulations of immunopositive fibers were observed in the area pretectalis, the periventricular gray matter, the medial tegmentum and the isthmus. Labelled neurons were observed in the deep, and occasionally intermediate, tectal layers and in the laminar nucleus of the torus semicircularis. In the rhombencephalon, labelled fibers were observed at the highest density in the central gray matter and the locus coeruleus; labelled somata were observed only in the nucleus of the tractus solitarius.

Animals↗

PubMed1997

Quantitative and topographical study of retinal ganglion cells in the chameleon (Chameleo chameleon).

Chameleons display a number of well-described physiological peculiarities of their visual system, but there is no information on the topography of the retinal ganglion cell layer. In the present study, ganglion cell density of the chameleon retina was constructed from whole mounts of the retina stained with cresyl violet. For the identification of ganglion cells, these latter cells were labelled retrogradely with horseradish peroxidase applied to the optic nerve. Using this criterion, the proportion of ganglion cells was estimated to represent 80% of retinal cells, while glial cells and amacrine cells represented 14 and 6%, respectively, of the total cell population of the retina. As for the main features of the retinal map, first, ganglion cells were distributed inhomogeneously within the ganglion cell layer, and revealed the existence of a putative area centralis. Second, a horizontal visual streak, which showed two peak density areas, was identified. These features point out the degree of specialisation of the chameleon retina and the complexity of its visual system.

Animals↗

PubMed1997

Enrichment of glutamate-like immunoreactivity in the retinotectal terminals of the viper Vipera aspis: an electron microscope quantitative immunogold study.

A post-embedding immunogold study was carried out to estimate the immunoreactivity to glutamate in retinal terminals, P axon terminals and dendrites containing synaptic vesicles in the superficial layers of the optic tectum of Vipera. Retinal terminals, identified following either intraocular injection of tritiated proline, horseradish peroxidase (HRP) or short-term survivals after retinal ablation, were observed to be highly glutamate-immunoreactive. A detailed quantitative analysis showed that about 50% of glutamate immunoreactivity was localized over the synaptic vesicles, 35.8% over mitochondria and 14.2% over the axoplasmic matrix. The close association of immunoreactivity with the synaptic vesicles could indicate that Vipera retino-tectal terminals may use glutamate as their neurotransmitter. P axon terminals and dendrites containing synaptic vesicles, strongly gamma-aminobutyric (GABA)-immunoreactive, were shown to be also moderately glutamate-immunoreactive, but two to three times less than retinal terminals. Moreover, in P axon terminals, the glutamate immunoreactivity was denser over mitochondria than over synaptic vesicles, possibly reflecting the 'metabolic' pool of glutamate, which serves as a precursor in the formation of GABA.

Animals↗