Ultrastructural and light‐microscopic studies of the nodal region in large myelinated fibres of the adult feline spinal cord white matter

Hildebrand, Claes

doi:10.1111/j.1365-201x.1971.tb10978.x

Cited by 118 publications

(57 citation statements)

References 88 publications

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“…Ultrastructure studies of CNS tissue have shown that astrocytic processes encircle nodes of Ranvier (Hildebrand, 1971) and there is indirect evidence that at least some of the perinodal astrocyte processes may belong to type-2 astrocytes (ffrench-Constant & Raff, 1986). Our ionophoretic mapping experiments indicate that glutamate receptors occur not only in the soma but also along the entire length of processes, including their extremities in type-2 astrocytes (e.g.…”

Section: Discussionmentioning

confidence: 86%

Activation of glutamate receptors and glutamate uptake in identified macroglial cells in rat cerebellar cultures.

Wyllie

Mathie

Symonds

et al. 1991

The Journal of Physiology

143

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SUMMARY1. Patch-clamp methods have been used to examine the action of excitatory amino acids on three types of glial cell in cultures of rat cerebellum, namely type-ilike astrocytes, type-2 astrocytes and oligodendrocytes. In addition we have examined glutamate sensitivity of the precursor cell (the O-2A progenitor) that gives rise to type-2 astrocytes and oligodendrocytes.2. Glutamate (30 ftM), quisqualate (3-100 ,tM), (S)-a-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid (AMPA, 10-30 /SM) and kainate (10-500 ,uM) were applied to cerebellar type-2 astrocytes examined under whole-cell voltage clamp. Each of these agonists induced inward currents in cells held at negative membrane potentials. The currents reversed direction near 0 mV holding potential. N-Methyl-D-aspartate (NMDA, 30-100 /,M) or aspartate (30 ,tM) in the presence of glycine (1 /1M) did not evoke any whole-cell current changes in type-2 astrocytes.3. The distribution of glutamate receptors in type-2 astrocytes was mapped with single-or double-barrelled ionophoretic pipettes containing quisqualate or kainate. Application of these agonists (current pulses 100 ms, 50-100 nA) to cells held at -60 mV evoked inward currents of 20-120 pA in the cell soma and 10-80 pA in the processes. Responses could also be obtained at the extremities of processes (-% 60 ,um from the soma). D. J. A. WYLLIE AND OTHERS type-1-like astrocytes were inhibited when external Na+ was replaced by Li', although Li+ was found to pass through the glutamate channel in type-2 astrocytes.6. Oligodendrocytes in cerebellar cultures did not respond to glutamate, quisqualate or kainate indicating a lack both of a detectable electrogenic glutamate uptake mechanism and of glutamate receptor ion channels in these cells.7. We conclude that, of the various macroglial cells, only the type-2 astrocyte and its progenitor cell possess 'fast' glutamate receptor channels in short-term ( < 4 day) cultures. Detectable uptake currents were confined to type-i-like astrocytes. However, in older cultures (> 7 day) type-I-like astrocytes also developed glutamate receptor channels, in addition to their uptake currents. The possible involvement of glial glutamate receptors and glutamate uptake in neuronal-glial interaction is considered.

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Section: Discussionmentioning

confidence: 86%

Activation of glutamate receptors and glutamate uptake in identified macroglial cells in rat cerebellar cultures.

Wyllie

Mathie

Symonds

et al. 1991

The Journal of Physiology

143

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“…However, in normal mammalian CNS (unlike in the peripheral nervous system), gap junctions between oligodendrocytic paranodal loops have been documented (Sandri et al, 1982). Moreover, Schmidt-Lanterman incisures of the kind seen in peripheral nerve have been described in CNS myelin (Blakemore, 1969;Conradi, 1969;Hildebrand, 1971;McDonald and Ohlrich, 1971;Hildebrand et al, 1993). Consequently, it remains uncertain whether Cx32 along myelinated fibers is responsible solely for formation of gap junctions between oligodendrocyte tongue processes and other oligodendrocytic or astrocytic elements at the outer surface of myelin, or is also contained within CNS myelin where it serves to mediate radial junctional coupling.…”

Section: Oligodendrocytic Gap Junctionsmentioning

confidence: 96%

Connexin32 in oligodendrocytes and association with myelinated fibers in mouse and rat brain

Hertzberg

Nagy

1997

J. Comp. Neurol.

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The distribution and cellular localization of connexin32 (Cx32) in the brain and spinal cord of the mouse and rat was investigated by light microscope (LM) and electron microscope (EM) immunohistochemistry by using several different antibodies against Cx32. By double immunofluorescence staining for Cx32 and either the oligodendrocyte markers cyclic nucleotide phosphodiesterase (CNPase) or Rip, Cx32 was consistently found in oligodendrocyte cell bodies and proximal processes. Cx32 immunoreactivity was also clearly visualized along CNPase- and Rip-positive myelinated fibers. Both immunopositive cells and fibers were heterogeneously distributed and were often more intensely labeled when dispersed in or associated with regions of gray matter than when concentrated in major white matter tracts. Labeling of myelin sheaths along fibers was restricted to subpopulations of myelinated axons. In the cerebellar cortex, for example, it was selectively localized to sheaths around Purkinje cell axons. Punctate staining, distinct from that corresponding to cells or fibers, was evident in the olfactory bulb and hippocampus. By EM, oligodendrocytes exhibited cytoplasmic labeling associated with rough endoplasmic reticulum and Golgi apparatus. Their processes were intermittently stained, most intensely when surrounding myelinated fibers and occasionally in paranodal loops. Cx32-immunoreactive gap junctions with symmetric labeling (staining on both junctional membranes) were observed between oligodendrocytic somata and processes as well as between presumptive oligodendrocytic processes. Unidentifiable elements forming asymmetrically labeled gap junctions (staining only one side of junctional membranes) were less frequently encountered. Western blot analysis confirmed anti-Cx32 antibody detection of Cx32 in whole brain homogenates and an enrichment of the protein in isolated myelin fractions. These results are consistent with earlier ultrastructural studies showing the occurrence of inter-oligodendrocytic gap junctions, but indicate that these may be more prevalent than previously thought. Furthermore, the results suggest a specialized role of gap junctions composed of Cx32 along myelinated fibers belonging to subpopulations of neurons.

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“…1994b;H~rtig et al, 1994; reviewed by Bignami et at., 1992b;Celio & Blumcke, 1994). In the white matter, an extracellular compartmentation is well documented for nodes of Ranvier as indicated by accumulations of extracellular matrix proteoglycans, the perinodal gap substance (Langley, 1969;Hildebrand, 1971, Hildebrand & Skoglund, 1971Delpech et al, 1982;Bjartmar et al, 1994). Thus the distribution of the extracellular matrix components appears not random but associated with region-and cell type-dependent neuronal functions.…”

Section: Introductionmentioning

confidence: 94%

Extracellular matrix organization in various regions of rat brain grey matter

et al. 1996

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Previous studies revealed the concentration of extracellular matrix proteoglycans in the so-called perineuronal nets on the one hand and in certain zones of the neuropil on the other. This nonhomogeneous distribution suggested a non-random chemical and spatial heterogeneity of the extracellular space. In the present investigation, regions dominated by one of both distribution patterns, i.e. piriform and parietal cortex, reticular thalamic nucleus, medial septum/diagonal band complex and cerebellar nuclei, were selected for correlative light and electron microscopic analysis. The labelling was performed by the use of the N-acetylgalactosamine-binding plant lectin Wisteria floribunda agglutinin visualized by peroxidase staining and additionally by photoconversion of red carbocyanine fluorescence labelling for electron microscopy. The intense labelling of the neuropil of a superficial piriform region, presumably identical with sublayer Ia, was confined to a fine meshwork spreading over the extracellular space between non-myelinated axons, dendrites and glial profiles. In the reticular thalamic nucleus the neuronal cell bodies were embedded in zones of labelled neuropil. In contrast to these patterns, the labelled extracellular matrix in different cortical layers and in the other subcortical regions was concentrated in perineuronal nets as large accumulations at surface areas of the neuronal perikarya and dendrites and the attached presynaptic boutons. Astrocytic processes usually were separated from the neuronal surface by the interposed extracellular material. Despite a great variability, the width of the extracellular space containing the labelled matrix components in all perineuronal nets appeared to be considerably larger than that in the labelled zones of neuropil and the non-labelled microenvironment of other neurons. Our results support the view that differences expressed in topographical and spatial peculiarities of the extracellular matrix constituents are related to neuron-type and system-specific functional properties.

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Ultrastructural and light‐microscopic studies of the nodal region in large myelinated fibres of the adult feline spinal cord white matter

Cited by 118 publications

References 88 publications

Activation of glutamate receptors and glutamate uptake in identified macroglial cells in rat cerebellar cultures.

Activation of glutamate receptors and glutamate uptake in identified macroglial cells in rat cerebellar cultures.

Connexin32 in oligodendrocytes and association with myelinated fibers in mouse and rat brain

Extracellular matrix organization in various regions of rat brain grey matter

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