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Biomedical subjects

D Miceli

Publications and source records attributed to D Miceli.

At least 37 records · Page 2Linked to original sources
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

A quantitative study of cerebrovascular variation in inbred mice.

The arteries of the base of the mouse brain were examined after perfusion with India ink. A qualitative difference exists between inbred mice of three strains (C57BL/6J, 129/J and BALB/cCF) on the one hand, and genetically defined heterogeneous mice on the other; the latter consistently show anomalies similar to those previously described in genetically undefined rodents, whereas inbred mice do not. A quantitative morphometric analysis of the Circle of Willis of inbred mice was undertaken. The results of this analysis are consistent with the notion that the differences in shape between the circles of Willis of different strains of inbred mice are due to additive genetic variation between these strains.

Animals↗
PubMed1990

[Immunohistochemical analysis of the serotonin system in the brain of lizard Ophisaurus apodus].

The distribution of serotoninergic neurons (localization of somata, principal fiber tracts and projection zones) was investigated in the brain of the lizard Ophisaurus apodus using a specific antibody directed against serotonin (5-HT). A comparison of the results with those of the literature revealed that in spite of minor variations in the distribution of 5-HT in the different reptiles examined there exist common features which correspond to a general organizational pattern.

Animals↗
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↗
PubMed1988

Visual system degeneration in the glaucomatous albino quail.

The peripheral (eye, retina, optic nerve) and central (primary optic tracti and centers, centrifugal visual tractus and nucleus) visual system of an imperfect albino quail mutant with a sex linked recessive gene was examined in 32 specimens ages 1 week - 16 months-hatch using various histological techniques. During the first weeks the visual system was normal and comparable in its overall organization to that found in the pigmented quail. However, the ipsilateral retinal projections were observed to be weaker in the young mutant, then completely disappeared two months after birth. Initial signs of the bupthalmos, a form of spontaneous glaucoma, appeared between the 3rd and 5th months. This was characterized by a distention of the eye linked to an increase in intraocular pressure. The pathological process was progressive and at 16 months the eye was very prominent, the anterior chamber deep and a large and globular cornea was noted. The glaucoma progressively induced different histopathological changes in the visual system including: cupping of the optic disc, degeneration of optic axons and their parent ganglion and centrifugal cells and cavernous degeneration. All of these phenomena were identifiable at about the 10th post-natal month and progressed in a relatively constant and orderly manner. The retinal projections to the nucleus ectomamillaris, ventral and lateral optic tectum and ventral pretectum were the first to degenerate. The degeneration of optic fibers attaining the dorsal pretectum and dorsal thalamus occurred later. Furthermore the retrograde degeneration in the centrifugal isthmo-optic nucleus progressed from the external to the internal pole. The mechanisms involved in the selective degeneration of centrifugal and centripetal optic fibers is discussed.

Age Factors↗
PubMed1987

Nuclear origin of the centrifugal visual pathway in birds of prey.

The isthmo-optic nucleus (NIO) at the origin of the retinopetal pathway was examined in 12 birds of prey (strigiforms and falconiforms) using cytoarchitectonic methods and after the intraocular injection of the regrograde tracers Rhodamine beta-isothiocyanate and Fast blue. The NIO was found to be poorly differentiated and reticular in appearance and depending on the species contained between 900 and 1400 neurons. These values are approximately 10 times less than those recorded in the pigeon and chicken. As in the latter species, the experimental data obtained in the strigiform Tyto alba showed the presence of retinopetal ectopic neurons bilaterally. However the ipsilateral contingent was proportionally larger in the nocturnal raptor. The functional significance of the poorly developed centrifugal visual system in birds of prey is discussed.

Animals↗
PubMed1987

Time course of degeneration of the visual system induced by spontaneous glaucoma in the albino quail (Coturnix coturnix japonica).

The retinal projection of an imperfect albino quail mutant with a sex-linked recessive gene was examined 2 weeks-16 months post-hatch using various histological methods. During the first weeks the visual system was normal. Initial signs of buphthalmos, a form of spontaneous glaucoma, appeared between the 3d and 5th months. Its development induced a degeneration of the retinal projections according to a relatively precise sequence progressing from the mesencephalic tegmentum to the optic tectum, then from the pretectum to the thalamus. The data suggest that the degeneration of the optic axons results from their mechanical compression due to the increased intraocular pressure.

Age Factors↗
PubMed1987

The primary optic system in a microphthalmic snake (Calabaria reinhardti).

The retinal projections in the microphthalmic snake Calabaria reinhardti were investigated by means of the radioautographic method following intraocular injections of [3H]proline. The results demonstrated the existence of a general pattern of organization of the primary visual system comparable to that observed in macrophthalmic snakes. However, most of the primary optic centers appeared reduced and showed varying signs of atrophy, whereas others were completely absent. Elsewhere, the ipsilateral visual component appeared as well developed as that found in macrophthalmic snakes. The evolutionary significance of the differential microphthalmic pattern of organization of the primary visual system is discussed.

Animals↗
PubMed1987

Extratelencephalic projections of the avian visual Wulst. A quantitative autoradiographic study in the pigeon Columbia livia.

The efferent projections of the pigeon visual Wulst upon the diencephalon and mesencephalon were investigated using the autoradiographic technique following the combined injection of [3H] proline and [3H] leucine into the rostral hyperstriatum accessorium. Repeated measures of silver grain densities were performed bilaterally in different brain structures using a computer-assisted system of image analysis. The density values were compared (Mann-Whitney U-Test) with those recorded in three homolateral control structures (tractus opticus, n. rotundus, n. pretectalis principalis) and in corresponding contralateral areas and nuclei. The data showed ipsilateral projections from the visual Wulst and via the tractus septomesencephalicus upon the dorsal thalamus (n.: dorsolateralis anterior superficialis parvocellularis), ventral thalamus (n.: intercalatus, ventrolateralis, geniculatus lateralis pars ventralis--GLv), pretectum (n.: superficialis synencephali, geniculatus pretectalis, griseus tectalis, pretectalis: diffusus, pars lateralis and pars medialis, area pretectalis) as well as to the nucleus of the basal optic root, n. spiriformis medialis and optic tectum (layer 2-4, 6, 7, 12 and 13). Crossed projections were observed to pass through the supraoptic decussation and the posterior commissure, however only the contralateral n. GLv was found to be significantly labeled. Interspecies variations in the organization of descending visual Wulst projections, related to the terminal distribution and relative size of the crossed components may be linked to differences in the degree of overlap of the binocular fields. Correspondingly, this may reflect the degree of bilateralization upon the Wulst of direct input from the visual thalamus.

Animals↗
PubMed1987

Distribution of visual callosal projection neurons in the siamese cat: an HRP study.

In this experiment we studied the distribution of callosal cells in various visual cortical areas of both common and siamese cats using the HRP method. The results showed that the most notable difference between the two strains concerned the primary visual areas. Indeed, labeling in areas 17 and 18 was significantly lower in siamese cats and only a few scattered cells were encountered at the 17/18 border. In general, the number of callosal cells forming interhemispheric connections within areas 17, 18 and the 17/18 border was dramatically reduced in the siamese. For all other visual areas (19, lateral suprasylvian subdivisions, 20 a, b and 21 a, b) the distribution was comparable for both species. A study of the laminar distribution indicated that, for common and siamese cats, medium and large pyramidal cells were mainly concentrated in layers III and IV whereas in deeper layers we found a mixture of small pyramidal and fusiform neurons.

Animals↗
PubMed1986

The anatomical organization of retinal projections in the shark Scyliorhinus canicula with special reference to the evolution of the selachian primary visual system.

The retinal projections of the shark Scyliorhinus canicula were investigated using both the degeneration technique after eye removal and the radioautographic method following the intraocular injection of various tritiated tracers (proline, leucine, fucose, adenosine). The results showed contralateral projection via different optic tract components (TOM, AOT, TOm, TOl, ROVm, RODm) to various areas and nuclei of the hypothalamus (NSC), thalamus (NODLAT, NODMAT, NTTOM, NOVT, NODPT), pretectum (NOPC, NOCPd, NOCPv), tectum (SFGS, SGI) and mesencephalic tegmentum (AOTMd, NOTMv). Ipsilateral retinal projections were found to arborize within 7 distinct zones at the hypothalamic (NSC), thalamo-pretectal (NODLAT, NTTOM, NOVT, NOPC, NOCpd) and tectal (SFGS) levels. A comparison of the data with those previously obtained in different species of elasmobranchs and batoids indicate the existence of a common and consistent pattern of organization of the primary visual system in all selachians. Many of the discrepancies reported in studies on the organization of selachian retinal projection may be listed to methodological differences and/or interspecies variations in the cytoarchitecture of the different visual centers. Moreover, a comparison of the primary visual system of more primitive squalomorph sharks with that of the more advanced galeomorph sharks and batoids suggests that this system evolved through an increase in the neuronal density of the target structures and transformations in the dendritic configurations of the postsynaptic neurons rather than through an increase in the total number of projection zones.

Animals↗
PubMed1986

[Course of the degeneration of the primary visual system in albino quails with glaucoma].

In the quail, a sex-linked albino mutation is associated with buphthalmic glaucoma. This progressive disorder is detectable 3 to 6 months after hatching. Its development leads to a degeneration of retinal projection according to a relatively orderly sequence progressing from the tegmentum to the tectum and from the pretectum to the thalamus. We suggest that the degeneration of visual axons might be produced by mechanical compression resulting from an increase in intraocular pressure.

Albinism↗
PubMed1985

A comparative radioautographic study of the bidirectional axonal and transcellular transport of different amino acids and sugars in the lamprey visual system.

Following recent radioautographic evidence for the bidirectional axonal transport of [3H]proline from the eye of Lampetra fluviatilis, the present study examined the anterograde and/or retrograde labeling properties of 11 other amino acids and two sugars after intraocular injections of these tritiated substances in the lamprey. The intraocular injections of aspartic acid, glutamic acid, gamma-aminobutyric acid, arginine, phenylalanine, fucose and acetyl glucosamine resulted in a weak labeling of the primary visual centers: there was no evidence of either the transcellular transport of these tracers or the retrograde labeling of the retinopetal neurons. The primary visual system was found to be heavily labeled 24 h after eye injections of alanine, leucine, glycine, lysine, serine and valine. Among the latter only glycine produced a retrograde somatic labeling of retinopetal neurons. With a longer survival period (7 days), a specific transneuronal labeling was also noted after glycine injections. The significance of the differential uptake and transport of these different tracers in the lamprey visual system and possible mechanisms involved in the axonal retrograde transport of [3H]glycine and [3H]proline in the centrifugal pathways are discussed.

Acetylglucosamine↗
PubMed1985

Intracortical connections of the anterior ectosylvian and lateral suprasylvian visual areas in the cat.

Intra- and interhemispheric connections between the anterior ectosylvian visual area (AEV) and other visual cortical areas including the lateral suprasylvian (LSS) were examined in the cat using the retrograde double-label fluorescence technique. The areal and laminar distributions of labeled neurons were mapped following injections of different tracers: Evans Blue (EB), Fast Blue (FB) and Nuclear Yellow (NY) made separately into AEV and LSS of the same or opposite hemispheres. The results indicated: (1) reciprocal and bilateral AEV-LSS connections stemming from layers V and VI in addition to a predominant efferent LSS projection upon AEV from both layer III and the posterior lateral (PLLS) subdivision of LSS; (2) homotopic interhemispheric connections to AEV arising from layers III, V and VI and from layers III and V of ipsilateral areas 20 and 21a; (3) differential laminar distributions of the cell populations projecting to the two cortical sites injected including neurons in layer III of LSS which project to contralateral LSS and AEV of either hemisphere via collateral axon branching (double-labeled). The anatomical findings support the functional similarities between AEV and LSS and the possible role of AEV in interhemispheric transfer of visual information is discussed.

Animals↗