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A Derouiche

Publications and source records attributed to A Derouiche.

28 records · Page 2Linked to original sources
PubMed1994

Regeneration of axons into the trochlear rootlet after anterior medullary lesions in the rat is specific for ipsilateral IVth nerve motoneurones.

The fibre projection from the IVth nerve nucleus to the superior oblique muscle was determined quantitatively in the normal rat by defining fibre numbers in transverse sections of the IVth nerve, and neurone numbers after retrograde labelling by horseradish peroxidase (HRP) injection into the muscle. There were 183 +/- 27 (S.E.) labelled neurones in the nucleus contralateral to the injected muscle and only 2 +/- 1 ipsilateral. The ipsilateral fibre number was 234 +/- 7 and the cell/axon ratio 0.8 +/- 0.1. Extensive analysis of all HRP retrogradely labelled material revealed no central fibre contribution to the IVth nerve other than from neurones resident in the trochlear nucleus. The central portion of the trochlear nerve tract was severed at its point of decussation in the anterior medullary velum. Ninety days after lesion, 10 +/- 4 (6% of control) neurones were labelled in the ipsilateral trochlear nucleus; none were labelled in the contralateral nucleus or in any other part of the midbrain, pons, medulla, or cerebellum. The number of myelinated fibres in the IVth nerve had decreased to 21 +/- 5 (9% of control) so that the cell/axon ratio was 0.4 +/- 0.2, thus suggesting that a single motoneurone has more fibres after lesion. In electron micrographs of the IVth nerve, larger than normal numbers of unmyelinated fibres were seen. Many myelinated fibres displayed signs of abnormal myelination. After regeneration, the projection was exclusively ipsilateral and not crossed as in the normal. These findings establish that there is a high degree of specificity after regeneration since no myelinated central nervous system axons other than trochlear fibres select the IVth nerve root as a trajectory over which to regenerate.

Animals↗
PubMed1994

Glutamine synthetase immunoreactivity in the human hippocampus is lamina-specific.

Vibratome sections of immersion-fixed (4% paraformaldehyde) hippocampi from four autoptic cases without neuropathological findings were immunostained with a polyclonal anti-glutamine synthetase antibody. Immunoreactivity is restricted to astrocytes and has a layer-specific distribution: The highest levels are observed in the outer molecular layer of the fascia dentata, in the pyramidal cell layer and in the upper stratum oriens. The stratum radiatum displays particularly low immunoreaction. A conspicuous drop in immunoreactivity from the heavily stained outer molecular layer to its inner portion is marked by a clear-cut dividing line. The layer-specific staining pattern found corresponds to the laminated distribution of glutamate binding sites described by others.

Adult↗
PubMed1994

An immunocytochemical investigation of glial morphology in the Pacific hagfish: radial and astrocyte-like glia have the same phylogenetic age.

This study attempts to reconstruct the early phylogenetic history of macroglial cells among craniates. Since glia does not fossilize, such a reconstruction must be based on a cladistic comparison of glial characters in the Recent craniate taxa (hagfishes, lampreys, and gnathostomes); however, there are only few data on glial morphology and none on glial immunocytochemistry in hagfishes. Therefore, we investigated the presence and localization of various macroglia-specific epitopes in the brain and spinal cord of the Pacific hagfish, Eptatretus stouti (Myxinoidea) by means of immunocytochemistry. Antibodies directed against S100-protein and vimentin showed no cross reactivity. Antibodies directed against glial fibrillary acidic protein and glutamine synthetase labelled various glial structures. Glial fibrillary acidic protein-like immunoreactivity was observed in ependymal cells with radially oriented processes in some regions. However, throughout the entire CNS, labelling of non-ependymal cells and their processes prevailed. The processes of these cells made occasional vascular contacts and they also made contacts with neuronal perikarya. Glutamine synthetase-like immunoreactivity was also found in some processes with radial orientation and in ependymal cells; but the antibody stained mainly non-ependymal cells which gave rise to a felt-like meshwork of interdigitating fine and very fine processes penetrating the neuropil of the entire brain. Additionally, there was labelling in the walls of blood vessels and in processes enwrapping individual neurons. The occurrence of glial fibrillary acidic protein- and glutamine synthetase-like immunoreactivity in non-ependymal glial elements in the brain of hagfishes and the relative scarcity of labelling in radial glial elements necessitates a re-interpretation of the evolutionary history of glial cells. Non-ependymal macroglia with immunocytochemical and morphological characters resembling typical (mammalian) astrocytes appears to be as primitive as the various forms of radial ependymal glia.

Animals↗
PubMed1993

Loss of layer-specific astrocytic glutamine synthetase immunoreactivity in slice cultures of hippocampus.

Glutamine synthetase (GS) supposedly inactivates the excitatory neurotransmitter glutamate. By using immunocytochemistry for GS, we recently demonstrated a layer-specific, perisynaptic distribution of GS-immunoreactive astrocytes and their processes in perfusion-fixed rat hippocampi. Highest levels of immunoreactivity were found in well defined termination zones of glutamatergic hippocampal afferents. In the present study we analysed the developmental aspect of this neuron-glia interaction by using hippocampal slice cultures lacking all extrinsic afferents. Under these conditions, no layer-specific distribution of astrocytic GS immunoreactivity could be demonstrated. This suggests that the laminated distribution of GS immunoreactivity is formed in parallel with the segregated termination of hippocampal afferents. Thus, there is no predetermined pattern of GS-containing astrocytes playing a role in the segregation of extrinsic fibres. The ultrastructural localization of GS immunoreactivity in fine astrocytic processes around asymmetric, probably glutamatergic excitatory spine synapses confirms earlier in situ findings, which suggests that this arrangement is a global phenomenon of glutamatergic systems.

Animals↗
PubMed1993

Perineuronal nets provide a polyanionic, glia-associated form of microenvironment around certain neurons in many parts of the rat brain.

The nature and function of previously described perineuronal nets are still obscure. In the present study their polyanionic components were demonstrated in the rat brain using colloidal iron hydroxide (CIH) staining. In subcortical regions, such as the red nucleus, cerebellar, and vestibular nuclei, most neurons were ensheathed by CIH-binding material. In the cerebral cortex perineuronal nets were seen around numerous nonpyramidal neurons. Biotinylated hyaluronectin revealed that hyaluronan occurs in perineuronal nets. Two plant lectins [Wisteria floribunda agglutinin (WFA) and Vicia villosa agglutinin (VVA)] with affinity for N-acetylgalactosamine visualized perineuronal nets similar to those rich in anionic components. Glutamic acid decarboxylase (GAD)-immunoreactive synaptic boutons were shown to occupy numerous meshes of perineuronal VVA-positive nets. Electron microscopically, VVA binding sites were scattered throughout perisynaptic profiles, but accumulated at membranes and in the extracellular space except not in synaptic clefts. To investigate the spatial relationship between glial cell processes and perineuronal nets, two astrocytic markers (S100-protein and glutamine synthetase) were visualized at the light and electron microscopic level. Two methods to detect microglia by the use of Griffonia simplicifolia agglutinin (GSA I-B4) and the monoclonal antibody, OX-42, were also applied. Labelled structures forming perineuronal nets were observed with both astrocytic, but not with microglial, markers. It is concluded that perineuronal nets are composed of a specialized type of glia-associated extracellular matrix rich in polyanionic groups and N-acetylgalactosamine. The net-like appearance is due to perisynaptic arrangement of the astrocytic processes and these extracellular components. Similar to the ensheathment of nodes of Ranvier, perineuronal nets may provide a special ion buffering capacity required around various, perhaps highly active, types of neurons.

Acetylgalactosamine↗
PubMed1991

Astroglial processes around identified glutamatergic synapses contain glutamine synthetase: evidence for transmitter degradation.

Glutamate is the main excitatory transmitter in the cerebral cortex. The physiologically high spatial and temporal resolution in glutamatergic transmission requires effective transmitter removal. Thus, a close topochemical relation to the glutamatergic synapse is a prerequisite for an enzyme involved in glutamate transmitter degradation. Here we report that immunoreactivity against glutamine synthetase (GS), one of the glutamate metabolizing enzymes, is localized in the fine astrocytic processes associated with identified glutamatergic synapses in the rat hippocampus. We suggest that glutamate transmitter is rapidly taken up by these fine perisynaptic astrocytic processes and degraded by GS.

Animals↗
PubMedDate not supplied

Anatomical aspects of glia-synapse interaction: the perisynaptic glial sheath consists of a specialized astrocyte compartment.

Amongst several forms of glia-neuronal communication, glia-synaptic interaction appears particularly interesting in the light of the well-known examples of two-way signaling between neurons and astrocytes. We review recent structural and physiological evidence showing that the structural correlate of glia-synaptic interaction is the peripheral astrocyte process (PAP) positioned next to the synaptic cleft. The structural and functional properties of these processes suggest that the PAP represents a separate astroglial compartment, in particular since it is characterized by the restricted localization of the actin-binding ERM protein ezrin. The structural properties of PAPs and this protein form the basis of rapid morphological changes of PAPs. The physiological relevance of PAP plasticity is illustrated by the example of the suprachiasmatic nucleus, where astrocytes display a high degree of activity-dependent plasticity reflecting circadian time.

Animals↗