PubMed Health⌕ Search

Biomedical subjects

R Marchand

Publications and source records attributed to R Marchand.

At least 55 records · Page 3Linked to original sources
PubMed1991

Immunocytochemical localization of thyroid hormone receptors in the adult rat brain.

It is generally accepted that thyroid hormones act at the genomic level through an interaction with specific nuclear receptors. Using a monoclonal antibody raised against the rat liver nuclear L-T3 receptor (NTR), we report here the immunocytochemical localization of T3 receptors in the adult rat brain. The strongest NTR immunoreactivity was found in the olfactory bulb, the hippocampus, the dentate gyrus, the amygdala areas, and the neocortex (layers III-VI). An intermediate NTR immunoreactivity was found in the hypothalamus, whereas the thalamus, the caudate-putamen, and the pallidum were weakly NTR-immunoreactive. In the cerebellum, a strong NTR immunoreactivity was found in the nuclei of Purkinje cells, in the internal granular layer, and in some nuclei of cells located in the molecular layer. In the brainstem, a strong NTR immunoreactivity was found in the lateral mamillary nucleus and the interstitial nucleus. A weak to moderate NTR immunoreactivity was observed in the central gray matter, while the substantia nigra and the interpeduncular nucleus were weakly stained. Furthermore, we also found NTR immunoreactivity in the nuclei of ependymocytes, epithelial cells of the choroid plexus, and cells located in the white matter. At the electron microscope level, we confirm that the immunoreactivity was not only localized in the nuclei of neurons but also in the nuclei of astrocytes and medium oligodendrocytes. This study provides new information concerning the distribution of NTR in the rat brain: (1) NTR are present not only in neurons but also in glial and ependymal cells, and (2) there is a regional and cellular heterogeneity in the distribution of NTR in the central nervous system.

Animals↗
PubMed1990

Intracerebral implantation of synthetic polymer/biopolymer matrix: a new perspective for brain repair.

Various poly (2-hydroxyethyl methacrylate)-collagen and poly (glyceryl methacrylate)-collagen composite hydrogels with varying porosities and cross-linking densities were implanted into the cortex of adult rat brains to provide mechanical guiding substrates for wound healing and tissue ingrowth. The hydrogels were well tolerated by the neural tissue. After 2 and 3 month, hyper- and macroporous hydrogels (poly(glyceryl methacrylate)) with interconnected channel systems were penetrated by neural tissue and elements of extracellular matrices, with differences in the degree and the topographic patterning of tissue ingrowth according to the type of samples. These differences were ascribed to the geometry, size of the pore interconnections and the mechanical properties of the polymers. Hyper- and microporous hydrogels (poly(2-hydroxyethyl methacrylate)) and hydrogels without collagen were not penetrated by the host tissue. The compatibility of the polymers with the neural tissue was also tested in vitro. This study suggests a new approach to repair brain lesions consisting of loss of tissue volume.

Animals↗
PubMed1990

Transected spinal cords grafted with in situ self-assembled collagen matrices.

The purpose of this work was to evaluate if the implantation into the gap of a transected spinal cord of a biomaterial providing a scaffolding structure for tissue ingrowth would favor the permeation and the growth of regenerating axons across the spinal-bioimplant interface. The interstump gap of rat transected spinal cords was injected with an ice-cold neutral solution of collagen, either alone or mixed with glyoxal, a harmless tanning agent. Upon warming to the temperature of the tissue, the fluid implant self-assembled forming a loose fibrillar network which simultaneously re-established a physical continuity to the transected organ. At various post-implantation timepoints, the bioimplants were studied by light microscopy, with the picrosirius-polarization method and with scanning electron microscopy. We observed that the bioimplants evolved following three overlapping phases: first a massive inflammatory response characterized by the invasion of cells of heterogeneous nature, then, a phase where microcysts predominated and during which, there is a major remodeling of the biomatrix by the deposition of newly synthesized collagen and of a periodic acid Schiff-positive material. Finally, a regeneration phase occurred where astroglial processes followed by regenerating axons invaded the biomatrix. Three months after implantation, spinal axons had grown from the two spinal stumps and penetrated the bioimplant across at least one lesion interface. However, the glyoxal-tanned collagen matrices showed a better biostability and durability than collagen alone. We conclude that the histopathological reaction of the mammalian lesioned spinal cord, when adequately directed by a scaffolding structure can be beneficial for the expression of the intrinsic regenerative capacity of the spinal cord tissue.

Animals↗
PubMed1990

[A century of neurotransplantation in mammals].

The transplantation of neural tissue into the mammalian brain has been studied for a century. Although the experimental foundations of neurotransplantation were limited to basic biological issues, the progress made over the last decade in the use of foetal neurotransplants to replace interrupted neuronal pathways or to correct induced functional deficit of the central nervous system (C.N.S.), has opened a new field of research for repair of the damaged C.N.S. This review summarizes three major topics: (1) the major developments in the field of neurotransplantation since the first attempt in 1890, (2) the global field of application of grafting techniques of autologous, homologous and heterologous transplants to particular neuroaxonal systems in animal models (sensory, endocrine, motor, cognitive systems), (3) the specific applications of neurotransplantation to experimental forms of human neurological disorders in rodents and non human primates as a potential treatment for neurodegenerative diseases, and the future directions of neural grafting techniques (in vitro and transgenic techniques, artificial substrates) in the context of the scientific and the ethical problems which have been recently addressed.

Animals↗
PubMed1989

A fluorescence histochemical method for the demonstration of central catecholamine neurons in young embryonic tissues.

A simple fluorescence histochemical technique is described for the production of catecholamine histofluorescence in the developing brain of rat embryos. The procedure combines the magnesium-formaldehyde-glutaraldehyde perfusion technique, with polyethylene glycol dehydration and embedding. Several examples illustrate the sensitivity of the technique and the good preservation of tissue sections. The tissue can also be stored for several weeks without an appreciable loss of fluorescence.

Animals↗
PubMed1989

Complications of heparin therapy after total joint arthroplasty.

The cases of 112 patients who were treated intravenously with heparin for thromboembolic disease after total joint arthroplasty were reviewed. The over-all frequency of bleeding complications that were associated with therapy with heparin was approximately 30 per cent. In patients who were treated within six days after total joint replacement, the frequency of bleeding complications was 45 per cent. The prevalence of bleeding problems declined to 15 per cent in patients who were treated more than one week after arthroplasty. In roughly 35 per cent of the patients, therapy with heparin had to be discontinued because of complications. Thrombocytopenia developed in fewer than 5 per cent of the patients. It was concluded that anticoagulation therapy with heparin for clinically unimportant thromboembolic problems in the immediate postoperative period is not justified.

Female↗
PubMed1987

Histogenesis of the subthalamic nucleus.

Literature presents divergent hypotheses on the histogenesis of the subthalamic nucleus. The basal plate of the mesencephalon, the dorsal hypothalamus (or the longitudinal subthalamic zone) and an area closely related to the mammillary nucleus have all been proposed as the site of origin of the neurons of the subthalamic nucleus. However, based on the selective labelling of neurons of this nucleus by the [3H]thymidine ARG technique, our results clearly show that a germinative zone lying caudally along the dorsal aspect of the mammillary recess is responsible for the formation of the neurons of the subthalamic nucleus. From this site of origin, the neurons migrate radially and then tangentially and dorsally along the marginal layer of the ventral diencephalon. The present study gives a detailed account of the histogenesis of the subthalamic nucleus of the rat through successive stage of development. Our data also show that the same proliferative neuroepithelial matrix that gives rise to the subthalamic neurons is also responsible for the genesis of the neurons of the supramammillary and submammillothalamic nuclei. Some aspects of the cytological maturation of the neurons of the subthalamic nucleus are also given.

Animals↗
PubMed1986

Histogenesis of the striopallidal system in the rat. Neurogenesis of its neurons.

This study discusses the histogenesis of the structures of the extrapyramidal system. The first part based on [3H]thymidine autoradiography provides data on the time of origin of the various neuronal populations that characterize different structures of the extrapyramidal system. Such data are essential to any further study dealing with the localization of the different sites of origin of the neurons along the ependymal matrix and with their migration during the histogenetic sequences leading to their definitive pattern of adult distribution. The neurons of globus pallidus and of the entopeduncular nucleus are generated on days 12-15 and days 11-14, respectively. A peak of neurogenesis occurs on day 12 for the entopeduncular nucleus and on day 14 for the globus pallidus. In the pallidum, the first neurons to form on day 12 settle caudally, while neurons generated on day 15 settle in the rostral extremity. The genesis of the medium-sized neurons of the neostriatum extends from day 12 to at least postnatal day 2. A peak is obvious on day 15. Although the neurogenesis of these neurons follows a mild caudorostral gradient, a more careful examination reveals four different patterns of settlement according to the area involved and the period of gestation. At the level of the caudal neostriatum, the neurons display a clear mediolateral spatiotemporal gradient. More rostrally, the neurons generated on days 13, 14 and 15 show two patterns of settlement. On the one hand, many neurons settle rather densely along the external capsule on day 13, occupying more rostral levels on days 14 and 15. On the other hand, in the body of the neostriatum, clusters of isochronically generated neurons are obvious. Later, newly generated neurons display a rather homogeneous distribution in the structure. A parallel is drawn between these patterns of development and the patterns of distribution of afferent terminals or neurotransmitters. The large chromophilic neurons of the neostriatum appear exclusively during the early period. Two peaks of neurogenesis are apparent. The one on day 13 comprises neurons that settle caudally. It is contemporaneous to the neurogenesis of the adjacent basal nucleus. The second peak occurs on day 15 and corresponds to that of the medium-sized neurons.

Aging↗
PubMed1986

Histogenesis at the level of the basal forebrain: the entopeduncular nucleus.

This study shows that the neurons of the entopeduncular nucleus are derived from a longitudinal slab of isochronically generated neurons on day 11 and 15 h of gestation. Many neurons of this longitudinal slab which we have named the basal forebrain cell column, originate from an ependymal matrix closely associated with the ventral diencephalic sulcus and later become associated with the basal forebrain bundle. Other neurons also originate from the ependymal matrix at the site of emergence of the optic recess and keep close relationships with the optic chiasma through the following stages of development to form the retrochiasmatic nucleus. During the second half of day 12 of gestation, the mantle layer of the forebrain shows an early zone of differentiation along its ventrolateral aspect. At this stage, the basal forebrain cell column extends unbroken from the tuberculum posterius to the chiasmatic plate primordium (site of generation of the retrochiasmatic nucleus). At the level of the caudal aspect of the optic stalk however, the basal forebrain cell column divides in two limbs associated to the ventral and dorsal edges of the optic stalk as it emerges from the forebrain. On day 14 of gestation, the neurons of the dorsal limb of the basal forebrain cell column occupy the mantle layer of the neural tube at least as far rostrally as the ventricular elevation in front of the optic stalk in the floor of the foramen of Monro. The neurons derived from the basal forebrain cell column begin breaking up into a series of more definite nuclei at later stages of development. The main finding of this study is the disclosure of the fact that the entopeduncular nucleus as well as other cell groups as dissimilar as the lateral preoptic area, the central, medial and anterior cortical amygdaloid complex and neurons of the dorsal hypothalamic area appear to be embryologically related, as they are all derived from a common longitudinal slab of the matrix of the forebrain.

Animals↗
PubMed1984

The nigrostriatal nervous pathways in the brain of the cat. An autoradiographic study.

By comparing the findings obtained in these series of cats with injections of 3H-leucine involving different areas of the SN and adjacent neurons of the VTA, some conclusions may be drawn concerning the origins, courses, and terminations of the nigrostriatal fibers. Three main bundles of nigrostriatal fibers originating from different groups of neurons of the SN may be identified. The main cluster of neurons of the compacta type, corresponding to the more abundant and larger neurons of this group in the caudal part of the SN and above (pars dorsalis of the SN), gives rise to fibers that leave the latter structure through its dorsomedial lip. They course successively in the VTA and in the area of Tsai and proceed rostralward through the lateral hypothalamus, subthalamus, and the internal capsule. At the level of the anterior limb of the internal capsule, they undergo an important arborization before ending in the putamen and caudate nucleus. Fibers from the main cluster of compacta neurons terminate more dorsally and those from the dorsal part of the SN end more ventrally in the neostriatum. These findings generally agree with those of VanderMaelen et al. (12) and Szabo (9), who applied the HRP technique, and Usunoff et al. (11), who used a selective silver impregnation method in cat brains. In the caudate nucleus, endings from the compacta type neurons are more abundant in certain areas, forming islands of dense silver grains. These areas of dense endings appear to correspond to the areas of greater cellular density of the striatum as more easily recognizable in the caudate nucleus of the newborn cat (Fig. 9).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1983

Isthmic origin of neurons of the rat substantia nigra.

This study provides new data on the time of origin, the generation site and the migration route of the young neurons of the substantia nigra of the rat during embryogenesis. The neurons of the substantia nigra are generated on day 12, 13, 14 and 15 of gestation. They settle following a light spatiotemporal rostrocaudal gradient from day 12 to 15. The neurons of the substantia nigra are generated at two different points of the basal plate at the level of the fovea isthmi (meso-isthmic junction) and migrate in radial pattern as two definite streams toward the ventral mesencephalon. From this point they move rostralwards along the surface towards their final site. The main findings of this work are the disclosure that the neurons of the substantia nigra are generated in the region of the isthmus rhombencephali and that its cells do not migrate between existing cells of the mesencephalic tegmentum but first migrate ventralwards in a radial pattern and then rostrally towards their definite site. Numerous neurons of the basal mesencephalon and of the midline structures of the caudal mesencephalon are apparently derived from the region of the fovea isthmi.

Animals↗
PubMed1983

Comparative morphology of the substantia nigra and ventral tegmental area in the monkey, cat and rat.

Four types of neurons were identified in the substantia nigra (SN) of the monkey, cat, and rat. The compacta-type neurons, characterized by unevenly distributed and intensely stained Nissl substance, display many shapes and sizes. The reticulata-type neurons, characterized by the presence of discrete Nissl bodies, are triangular or round. The intermediary-type neurons contain less intensely stained but more diffusely distributed Nissl substance. These triangular or fusiform neurons have thinner processes than the compacta- and reticulata-type cells. The globular-type neurons, characterized by a high nuclear/cytoplasmic ratio, are much smaller than the three other types of SN neurons. The total number of neurons of the SN, which is much greater in the macaque (n=73,508) than in the cat (n=38,366) and the rat (n=22,532), is comprised mainly of the compacta type neurons (n=62,624; 22,323; and 9.925 in the three species, respectively). The reticulata-type neurons are more abundant in the cat, and the intermediary and globular types are more numerous in the rat. The compacta-type neurons have a particular distribution in each species. The ventral tegmental area (VTA) contains numerous globular-type neurons and a number of compacta-like or transitional type neurons which constitute the foyer pédiculaire of the central linear nucleus and the paranigral nucleus. The rostral linear nucleus is unique to the cat brain.

Animals↗
PubMed1982

Vertically oriented alternating acetylcholinesterase rich and poor territories in laminae VI, VII, VIII of the lumbosacral cord of the rat.

The pharmaco-histochemical method for the demonstration of acetylcholinesterase has been applied to study the spinal cord of the rat. Twenty rats were treated with di-isopropylphosphofluoridate at various time intervals before death and their lumbosacral cord sectioned in either the sagittal, horizontal or transverse plane. Under such conditions, the acetylcholinesterase activity of the neuropile which normally masks many neurons is minimal. The distribution of acetylcholinesterase-containing neurons corresponds to that described previously by various authors, but now the acetylcholinesterase-containing perikarya and their processes may be visualized to a degree not previously attained. This aspect of the technique has allowed us to observe very clearly some features of the internal organization of the spinal cord at the lumbosacral level. The original finding of the present work is the disclosure of alternating bands of dark and light acetylcholinesterase activity at the level of the intermediate grey (laminae VI, VII and VIII) along the rostrocaudal extent of the lumbosacral segments of the rat spinal cord. Dendritic bundling extending over long distances has also been observed at different sites in the ventral horn and in the intermediolateral cell column.

Acetylcholinesterase↗
PubMed1982

Autoradiographic study of the neurogenesis of the inferior olive, red nucleus and cerebellar nuclei of the rat brain.

This study provides basic data on the time of origin as well as on the spatio-temporal setting pattern of the neurons of the red nucleus, the inferior olivary complex and the cerebellar nuclei during ontogenesis of the rat brain. The first neurons of the olive form on day 12. In the adult they set in the rostral part of the dorsal accessory olive and in the minor subgroups associated with the medial accessory olive. On day 13, neurogenesis is intense in both divisions of the red nucleus, in all areas of the inferior olivary complex, in the medial and interpositus cerebellar nuclei and in the small-celled part of the lateral cerebellar nucleus. On day 14, neurogenesis is completed in the magnocellular division of the red nucleus and in the dorsal accessory olive but the neurons of the principal and medial accessory olives, of the rostral and caudal poles of the medial cerebellar nuclei, of the interpositus and lateral cerebellar nuclei as well as those of the parvocellular division of the red nucleus are still formed. Our study suggests that in the rat brain the neurons of the nuclei involved in the rubro (parvo)-olivo-cerebello-rubral and rubro (magno)-reticulo-cerebello-rubral loops develop on days 13 and 14 of gestation. Maturation, cytoarchitecture and phylogeny are also discussed.

Animals↗
PubMed1979

[Histopathologic and neurochemical correlations as a function of lesions of the locus coeruleus region in the cat (I)].

Unilateral lesions in the area of the loci coeruleus and subcoeruleus in the cat are associated with a significant and sustained decrease of noradrenaline (NA) in the ipsilateral cerebral cortex without any important change in the concentrations of NA in the contralateral cortex and in the spinal cord of both sides. The serotonin (5-HT) concentrations of the spinal cord and cerebral cortex of both sides remained unchanged in the same groups of animals. Bilateral lesions in the same area result also in a marked decrease of NA in the cerebral cortex of both sides. The latter lesions also result in slight decreases of NA in the hypothalamus and of NA and 5-HT in the spinal cord but the NA and 5-HT concentrations of the striatum and thalamus and the 5-HT concentrations of the cerebral cortex and hypothalamus are unmodified by such lesions. Unilateral lesions of the area immediately rostral to the locus coeruleus (praelocus lesions) result in a very significant decrease of NA in the ipsilateral cerebral cortex without any change of NA in the contralateral cerebral cortex and spinal cord of both sides. Similar lesions produced bilaterally in another group of cats resulted in marked decreases of NA in the cerebral cortex of both sides and a slight decrease of NA in the thalamus without any change of NA in the striatum, hypothalamus and spinal cord and of 5-HT in the cerebral cortex. In the same group of animals with lesions which, however, extended more closely to the midline than in cats with locus coeruleus lesions, 5-HT is markedly decreased in the striatum and thalamus and slightly decreased in the hypothalamus and spinal cord. These results support the view that the noradrenergic coeruleo-cortical pathway is made up of fibers which originate in the loci coeruleus and subcoeruleus and predominantly end ipsilaterally to their origin in the cerebral cortex. Ascending NA fibers ending in the thalamus appear to originate from NA neurons located more laterally in the upper pons and more specifically at the level of the parabrachial nuclei.

Animals↗