Glial Cells In Central Nervous System Research Articles

Localization of sodium/potassium adenosine triphosphatase in multiple cell types of the murine nervous system with antibodies raised against the enzyme from kidney

This report describes the development and characterization of a battery of highly specific antibodies to sodium/potassium (Na+ + K+)-ATPase and their use in localizing this enzyme in nervous tissue. The immunolabeling characteristics of polyclonal antibodies and monoclonal antibodies (Schenk, D. B., and H. L. Leffert (1983) Proc. Natl. Acad. Sci. U. S. A. 80: 5281-5285) raised against rat renal (Na+ + K+)-ATPase were compared. The interspecies cross-reactivity of the polyclonal anti-rat antibodies was examined by determining their binding to purified rat, eel, or dog enzyme. The immunostaining characteristics of the IgG fraction of the polyclonal antibody preparations, their affinity-purified derivatives, and the monoclonal antibodies were compared. The results obtained with each of these were similar, providing information about where focal concentrations of the enzyme exist within nervous tissue. The IgG fraction of the polyclonal antibody preparations provided the most sensitive probe, facilitating localization of the (Na+ + K+)-ATPase in the tissue sections from various regions of the nervous system. (Na+ + K+)-ATPase-like immunoreactivity was observed along the plasmalemma of alpha-motor neurons and at the nodal axolemma of myelinated axons from the central or peripheral nervous system. It was determined that the absence of labeling for the enzyme along the paranodal or internodal regions of the axolemma was not an artifact due to a limited accessibility of antibody to these regions. Some central nervous system glial cells demonstrated abundant amounts of plasmalemmal and intracellular (Na+ + K+)-ATPase-like immunoreactivity. These cells were identified as astroglia by positive labeling of cells in serial sections for glial fibrillary acid protein immunoreactivity in the soma and radial processes in optic nerve, or velous processes in the cerebellum. Astrocyte processes overlying the nodal axolemma also stained positively for the enzyme. (Na+ + K+)-ATPase-like immunoreactivity was not observed in association with oligodendroglia cell bodies or their processes forming myelin sheaths. In contrast, the plasmalemma of myelinating Schwann cells showed greatest immunoreactivity in the region of the node of Ranvier. Although a focal concentration of immunoreactivity was observed along node- and paranode-associated regions of Schwann cells, a lower level of uniform staining was noted along the entire Schwann cell surface membrane.(ABSTRACT TRUNCATED AT 400 WORDS)

Neuropeptides modulate the beta-adrenergic response of purified astrocytes in vitro.

Neuropeptides may have functions in the central nervous system (CNS) other than altering neuronal excitability. For example, they may act as regulators of brain metabolism by affecting glycogenolysis. Since it has been suggested that glial cells might provide metabolic support for neuronal activity, they may well be one of the targets for neuropeptide regulation of metabolism. Consistent with this view are reports that peptide-containing nerve terminals have been seen apposed to astrocytes, but it is also quite possible that peptides could act at sites lacking morphological specialization. Primary cultures containing CNS glial cells have been shown to respond to beta-adrenergic agonists with an increase in cyclic AMP and, as a result, with an increase in glycogenolysis and have also been shown to respond to a variety of peptides with changes in cyclic AMP. In the study reported here, we have examined the effects of several peptides on relatively pure cultures of rat astrocytes. We demonstrate that the increase in intracellular cyclic AMP induced by noradrenaline is markedly enhanced by somatostatin and substance P and is inhibited by enkephalin, even though these peptides on their own have little or no effect on the basal levels of cyclic AMP. Vasoactive intestinal peptide (VIP) on the other hand increases cyclic AMP in the absence of noradrenaline. These results suggest that neuropeptides influence glial cells as well as neurones in the CNS and, in the case of somatostatin and substance P, provide further examples of neuropeptides modulating the response to another chemical signal without having a detectable action on their own.

Immunohistochemical study of myelin sheaths formed by oligodendrocytes interacting with dissociated dorsal root ganglion neurons in culture

The addition of central nervous system (CNS) glial cells to dissociated networks of rat dorsal root ganglion neurons in tissue culture provided a useful system for the study of CNS myelin sheath formation. The CNS myelin basic proteins (BP) and proteolipid protein (PLP) were demonstrable in these cultures by immunoperoxidase techniques. Both BP and PLP were detectable in myelinating oligodendrocytes and CNS myelin sheaths. Anti-BP serum and anti-PLP serum were useful immunohistochemical staining reagents for the identification of myelinating oligodendrocytes and CNS myelin sheaths in tissue culture.

Immunofluorescent Visualization of 100 Å Filaments in Different Cultured Chick Embryo Cell Types

Antibody prepared against the 55,000 dalton subunit of reconstituted chick gizzard 100 A filaments (anti-G55K) bound to the 100 A filaments of chick smooth muscle, cardiac muscle, and skeletal muscle cells, and to the 100 A filaments of Schwann cells and satellite glial cells of the peripheral nervous system. Anti-G55K did not bind to replicating presumptive myoblasts, fibroblasts, chondroblasts, pigment cells, neurons, or to central nervous system glial cells. This contrasted with the wider range of binding of antibody to the 58,000 dalton subunit of chick fibroblast 100 A filaments (anti-F58K) which bound to the 100 A filaments of all cell types examined except hepatocytes and skin epithelial cells. Anti-G55K) staining revealed a morphologically distinct distribution of 100 A filaments in the three types of muscle cells. Spindle shaped smooth muscle cells exhibited dense fluorescent staining near the poles of the cells, and also exhibited unique patches of fluorescent material after cytochalasin B and Colcemid treatment. In myotubes, the fluorescence was limited to longitudinal bundles of filaments between the striated myofibrils. Cardiac cells contained uniformly distributed fine filaments. Lastly, smooth muscle cells in various phases of mitosis bound the anti-G55K, whereas replicating presumptive skeletal myoblasts failed to bind the anti-G55K.

On the Role of Glial Cells in the Mammalian Nervous System: UPTAKE, EXCRETION, AND METABOLISM OF PUTATIVE NEUROTRANSMITTERS BY CULTURED GLIAL TUMOR CELLS

Abstract The synthesis, uptake, and efflux of some putative neurotransmitters by cultured rat glial tumor cells were studied. Three glial cell clones were capable of pyridoxal-dependent synthesis of γ-aminobutyrate both in cell-free homogenates and in intact cells in monolayers. Substantial catabolism of γ-aminobutyrate was not found. Synthesis of taurine and isethionic acid, but not β-alanine, by one of the glioma lines was also shown. Glioma lines were found to take up glutamate and exhibited Na+-dependent uptake of γ-aminobutyrate. The uptake of γ-aminobutyrate consisted of a slow saturable component (Kt ∼ 13 to 30 µm) and a rapid nonsaturable component. Both of these were antagonized by some structural analogs of γ-aminobutyrate as well as by taurine, β-alanine, bicuculline, and low temperature. Similar kinetic parameters were found for three different glioma lines. Fibroblast-like cells obtained from rat brain cell cultures had only the nonsaturable component of γ-aminobutyrate uptake. Taurine uptake also consisted of two Na+-dependent and temperature-dependent components: a rapid saturable component (Kt ∼ 10 to 17 µm) and a nonsaturable component which varied in magnitude between cell lines. These uptakes were antagonized by β-alanine but not by γ-aminobutyrate. The glioma lines also excreted the concentrated γ-aminobutyrate into the extracellular milieu, but could maintain cell to medium concentration ratios of g80-fold. In taurine efflux experiments, cell to medium concentration ratios in excess of 1500-fold could be maintained by one of the gliomas. The data are consistent with a possible role of central nervous system glial cells in the modulation of neuronal excitability via control of the levels of neuroactive substances in the extracellular milieu of neurons.