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Biomedical subjects

A Privat

Publications and source records attributed to A Privat.

At least 163 records · Page 9Linked to original sources
PubMed1990

Catecholaminergic systems and amygdala kindling development. Effects of bilateral lesions of substantia nigra dopaminergic or locus coeruleus noradrenergic neurones.

The effects of the bilateral and selective destruction of substantia nigra (SN) dopaminergic or locus coeruleus (LC) noradrenergic neurones, consecutive to a local injection of 6-hydroxydopamine, were studied on the development of amygdala kindling. Immunohistochemical controls of lesions were performed using selective dopamine (DA) or norepinephrine (NE) antibodies. The results demonstrated that a massive destruction of SN pars compacta neurones did not modify the rate of kindling development. Conversely, the lesions of LC neurones (sparing lateral tegmental nuclei) markedly facilitated the development of amygdala kindling. This effect was related to the extent of NE denervation. Together, these results suggest that DA is not strongly involved in the development of kindling, and that the nigrostriatal output does not play a major role in the generalization of kindled seizures. In contrast, they confirm an inhibitory influence exerted by LC noradrenergic ascending pathways on the development of kindling.

Amygdala↗
PubMed1989

Pre- and post-natal ontogeny of serotonergic projections to the rat spinal cord.

The development of 5-hydroxytryptamine (5-HT) innervation in the spinal cord was studied from embryonic day 14 (E14) to adulthood. Sprague-Dawley rats were fixed by perfusion with 5% glutaraldehyde in cacodylate-sodium metabisulfite buffer, and vibratome sections were processed for immunocytochemistry with a 5-HT antiserum. For electron microscopy, the sections were flat-embedded in araldite, and thin sectioning was performed. 5-HT neurons caudally directed from raphe nuclei invade the spinal cord at E14 and reach the caudalmost levels by E16-E17. In longitudinal sections, axons are seen by E15, at cervical and upper thoracic levels, to invade the presumptive gray matter from the anterior and lateral funiculi. The invasion process occurred either by sharp angulation of the axon or by branching of a collateral. By E16, at thoracic level the anterior horn and the intermediolateral columns are profusely innervated by very thin, varicose fibers; synapses are seen at E17 and E18 using EM. 5-HT immunoreactive boutons are involved here. After birth, 5-HT innervation of these two areas evolves progressively from a diffuse network to a more restricted pattern, especially at the thoracic level for the intermediolateral column and at cervical and lumbar levels for the anterior horn. The adult pattern is reached by postnatal day 21 (P21). The growth of axons toward the dorsal horn becomes noticeable by E19 at all spinal levels, when fibers invade the neck of the horn from the lateral funiculus, and innervation proceeds diffusely until P5. At P7, thin fibers course dorsally and laterally along the border of the gray matter and ramify profusely in layers I and II. The adult pattern is also reached in the dorsal horn by P21. These results are discussed in relation to the postnatal maturation of motor and sensory circuits and to the development of transplanted raphe neurons in the rat spinal cord.

Aging↗
PubMed1989

Locomotion in rats transplanted with noradrenergic neurons.

It is known that catecholaminergic drugs can induce both locomotion and a late flexion reflex in spinalized animals. We studied spinal reflexes and locomotor activity in five adult spinal rats which had received a suspension of fetal noradrenergic (NA) neurons below the transection and in three control spinal rats. A rhythmical activity similar to the one of locomotion was regularly observed in three of the grafted rats held above a moving belt. In two of them, the step frequency was increased when the velocity of the moving belt was increased. This was not observed in control rats. A late flexion reflex was obtained in grafted rats that displayed locomotor activity, as well as in two controls. In the two rats which exhibited locomotor activity, analysis showed numerous immunoreactivite (against NA) cells and processes with terminals concentrated around the perikarya of motoneurones.

Animals↗
PubMed1989

Intraspinal transplants of serotonergic neurons in the adult rat.

Adult male Sprague-Dawley rats were made paraplegic by a complete transection of the spinal cord at lower thoracic level. One week later they were transplanted, below the level of the section, with a cell suspension prepared from the raphe region of 14-day embryos. After survival periods of 10 days to 1 year, the animals were sacrificed and the spinal cord processed for the immunocytochemical detection of 5-HT. Axons from grafted cells grew extensively into the grey matter of the host, and established axosomatic and axodendritic synapses in the anterior horn and intermediolateral column, similar to those of the intact animal. In addition, a group of transplanted animals was tested for sexual reflexes which are under the control of serotonin. It was found that ejaculation reflexes, which are absent in paraplegic rats, are restored in transplanted animals.

Animals↗
PubMed1989

Modulation of GFAP mRNA levels following toxic lesions in the basal ganglia of the rat.

GFAP mRNA levels were quantified by Northern blot analysis using a human GFAP (glial fibrillary acidic protein) cDNA probe in association with immunocytochemistry. Ten days after a unilateral lesion of substantia nigra with 6-hydroxydopamine (6-OHDA), GFAP mRNA level is increased 1.4-fold in the ipsilateral striatum; thereafter it declined continuously to reach the control level 4 months later. This effect contrasted with the lower and more sustained increase of preproenkephalin (PPE) mRNA, a marker of neuronal target of nigrostriatal pathway. Following ibotenic acid-induced neuronal degeneration of the neostriatum in the rat, we observed a sharp elevation of the GFAP transcripts (4-fold) as soon as 2 days after the lesion both in the striatum and in the substantia nigra. Whereas in the striatum GFAP mRNA level already declined at 5 days postlesion, it remained stable in the substantia nigra. In comparison GFAP immunoreactivity was slightly delayed. No obvious modification was observed in the contralateral side to the lesion whatever the denervation condition studied. Implication of these results on the understanding and the therapeutic approach of glial scarring is discussed.

Animals↗
PubMed1989

Influence of GM1 gangliosides on the growth of cultured rat embryonic serotonergic neurons.

GM1 gangliosides were added to the medium of cultured raphe neurons enriched in the serotonergic phenotype in order to study their influence on biochemical and morphological growth parameters of serotonergic neurons. After 2 days of culture in the presence of GM1, specific uptake of serotonin measured by scintillation counting exhibited a moderate but significant increase for a GM1 concentration of 5 X 10(-8) M. Morphological parameters of 5-HT neurons were measured after immunocytochemical staining with specific serotonin antiserum, and digitalization of immunoreactive cells. Eight parameters were studied; for concentrations of 5 X 10(-8) and 10(-7) M of GM1, the absolute neuritic field area and the total length of the segments were significantly increased, whereas the number of neuritic segments, and their mean length were not modified. We conclude that GM1 ganglioside has a significant influence on the growth of serotonergic neurons. Moreover, electron microscopy showed, on treated cultures, a dramatic increase of the number of spicules all along the neuron's process, suggesting that GM1 could act by modifying the attachment of cells to their substrate. The possible molecular mechanisms of the action of GM1 are discussed.

Animals↗
PubMed1989

[First transplantation of embryonic serotonergic neurons in primate spinal cord].

Three adult monkeys (Macaca fascicularis) underwent a total section of the spinal cord at thoracic level (T6). 1 week later, two of them received at T8 level an injection of a cellular suspension prepared from the raphe region of a foetal macaque 39 days old. The third animal received one injection of buffer solution. 1 month later, the animals were sacrificed, and their spinal cord was processed for the immunocytochemical detection of serotonin with light and electron microscopy. Serotonergic neurons had survived after transplantation, and had grown axons and dendrites. Afferent and efferent synapses to serotonergic neurons were readily identified.

Animals↗
PubMed1988

Non-competitive antagonists of N-methyl-D-aspartate receptors protect cortical and hippocampal cell cultures against glutamate neurotoxicity.

Brief exposure of cortical or hippocampal cell cultures to glutamate (500 microM) resulted in a progressive neuronal necrosis which is maximal 18-24 h later. Pretreatment of the cultures by a phencyclidine derivative: thienylphencyclidine (TCP), or the TCP precursor: GK86, or MK801 protected against glutamate toxicity. Non-competitive antagonists of N-methyl-D-aspartate receptors appear as potent tools for the in vitro protection of neuronal cells against excitatory amino acid toxicity.

Animals↗
PubMed1988

Identification of a human glial fibrillary acidic protein cDNA: a tool for the molecular analysis of reactive gliosis in the mammalian central nervous system.

Two clones encoding human glial fibrillary acidic protein (GFAP) were isolated from a human astrocytoma cDNA library. The clones pHGFAP1 and pHGFAP2 were selected by the combined use of differential colony hybridization and hybridization-selection technique with polyclonal anti GFAP antiserum. The longer one, pHGFAP1, encompasses 3.0 kb and includes the 1.8 kb long 3' untranslated region specific to the human mRNA. Sequence data disclosed an extensive homology within the coding region of human and mouse GFAP cDNAs even in the end domains. Blot hybridization analysis of RNAs from human, rat and mouse brain revealed a single GFAP mRNA species of 3.1, 2.8 and 2.7 kb respectively and Southern blot experiments indicated that this mRNA is most probably transcribed from a unique gene. In situ hybridization performed with biotinylated probes on cultured mouse brain cells suggests both the sorting and the transport of GFAP mRNA throughout the cytoplasm and processes of the astrocytes. As a model of reactive gliosis secondary to degenerative disorders, 6-hydroxydopamine (6-OHDA) lesion of the substantia nigra in the rat was performed. GFAP mRNA increased 1.4 fold in the ipsilateral striatum on day 10 after the lesion. It then declined to the control level 4 months later contrasting with the lower and more sustained increase in preproenkephalin (PPE) mRNA. The interspecies cross-reactivity of the HGFAP probes make them useful as a tool for the molecular analysis of reactive gliosis in various experimental models.

Amino Acid Sequence↗
PubMed1988

Experimental modifications of postnatal differentiation and fate of glial cells related to axo-glial relationships.

The fate of glial cell lines following Wallerian degeneration in the rat optic nerve was analysed after pulse labelling with [3H]thymidine. The rats were unilaterally enucleated at the key stages 2, 5, 8 and 20 days after birth. Three hours later, they were injected intraperitoneally with [3H]thymidine and killed after 1, 3, 5, 10 and 20 days survival. Oligodendrocytes were the most affected, being unable to differentiate after 2 days enucleation, dying rapidly or transforming into another cell type after 5, 8 and 20 days enucleation. The apparent stability of the astrocyte population is due to an equilibrium between increased differentiation from glioblasts and increased death, the latter being preponderant at the key stage 2 days. Finally, the steady increase in the number of microglia may be due to the transformation from other cells, either glioblasts for the early time intervals or oligodendrocytes later on. It appears, then, that the interrelation between glial cell lines during differentiation is more intricate than previously suspected and is closely dependent, for each line, upon the integrity of axons.

Animals↗
PubMed1988

Immunocytochemical localization by electron microscopy of 2'3'-cyclic nucleotide 3'-phosphodiesterase in developing oligodendrocytes of normal and mutant brain.

Oligodendrocytes or their putative progenitors were the only cells found to be immunoreactive to polyclonal antisera against the enzyme 2'3'-cyclic nucleotide 3'-phosphodiesterase (CNP) in developing and mature brains of rats and mice, as visualized by light and electron microscopy. Prior to myelination (day 6), oligodendrocytes of the corpus callosum have reticular networks of CNP-containing filopodia, in addition to abundant CNP throughout the cytoplasm. Some glioblast-like cells of the subventricular zone are also immunoreactive to anti-CNP, suggesting that, as progenitors of oligodendroglia, they express this myelination-related protein as one of the earliest events in myelinogenesis. Following the commencement of myelination (day 15), many oligodendrocytes lose much of their lacelike network of fine projections, possessing, instead, larger CNP-filled processes that extend to myelin-bearing fibers. CNP was always found only in the cytoplasm-containing compartments of the cells and myelin sheaths; neither lamellae nor cellular membranes were immunostained. These data support our contention that CNP is not an intrinsic membrane protein, despite its strong interaction with membrane components when cells are disrupted. In mutant (mld) mice (day 25), the many distended and uncompacted oligodendroglial processes that invest axons with only a few turns of membrane contained cytoplasmic CNP, accounting for the elevated levels of CNP activity previously noted in tissue fractions.

2',3'-Cyclic-Nucleotide Phosphodiesterases↗