A syringe modification for the simple and rapid dissociation of post-natal rat cerebral tissue for preparing primary cultures of mixed glial cells

Microglia Are Derived from Peripheral Blood Mononuclear Cells After Pseudorabies Infection in Mice

Pseudorabies virus (PRV) can spread along the peripheral nerves near the site of infection in the animals, and gradually migrates into the central nervous system, where it leads to the development of brain lesions. The aim of this study was to investigate the dynamics of microglia after PRV inoculation. A mouse model inoculated with PRV was established to study the interactions between PRV and microglia, microglial recruitment, and polarization effects. The mice were subcutaneously inoculated with different doses of PRV-Bartha K61 vaccine strain. The obtained results showed that mouse mortality rates increased with the applied doses of virus, and brain lesions, located in the brain tail and brain stem, were observed in each investigated group. Inflammatory cells were shown to infiltrate through the vasculature into perivascular cuff, and the number of microglia was increased as well. Mouse group treated with a medium infection dose demonstrated a high survival rate while developing serious brain lesions, and therefore, this dose was selected for further experiments. Immunohistochemistry, flow cytometry, and confocal laser scanning microscopy were used to analyze PRV-microglia interactions. After PRV inoculation, proliferating cell nuclear antigen (Pcna) and Iba1 double-positive cells were observed in the brain lesions, together with the activated microglia, suggesting that PRV can induce microglial proliferation and activation. Furthermore, 5-bromo-deoxy-uridine (BrdU) labeling demonstrated that microglial cells did not proliferate in situ and the proliferating cells originated from peripheral blood monocytes, mainly from the inflammatory monocytes (Ly6C^high). In addition, microglia polarized into both M1 and M2 phenotypes by PRV infection. The results obtained in this study may help understand the development of pseudorabies infection and help improve the treatment, by recruiting and enhancing immune response.

The role of calcium in rat oligodendrocyte injury and repair

The role of intracellular calcium in oligodendrocyte injury is investigated using cultured rat oligodendrocytes. Calcium ionophores A23187 and ionomycin mimic both complement and perforin attack, causing oligodendrocyte lysis at concentrations which do not lyse other glia. Membrane vesiculation, the mechanism by which oligodendrocytes resist and recover from complement and perforin attack, is also induced by A23187. Oligodendrocytes are more susceptible to complement attack in the presence of a calmodulin inhibitor (W7), which also inhibits vesiculation. These results imply that calmodulin is involved in membrane repair from complement attack, and indicate that changes in intracellular calcium play an important yet paradoxical role in the oligodendrocyte response to injury, dictating both susceptibility and cellular recovery.

Complement mediated serum cytotoxicity against oligodendrocytes: a comparison with other cells of the oligodendrocyte-type 2 astrocyte lineage

Rat oligodendrocytes are known to be susceptible to complement attack when exposed to homologous serum as a consequence of anti-myelin antibody independent classical pathway complement activation and attack. We have now compared this susceptibility with that of other cells of the oligodendrocyte-type 2 astrocyte (O-2A) lineage, and show that while type 2 astrocytes are not sensitive, O-2A progenitors are only relatively resistant to serum cytotoxicity, higher concentrations of complement resulting in cell damage. The implications of these findings for the pathogenesis of demyelinating disease are discussed.

Discrimination between different types of low-level luminescence in mammalian cells: the biophysical radiation

Cellular low-level luminescence was measured after various disintegrative processes in brain cell preparations. In addition to known origins of low-level luminescence, e.g. oxygen radical reactions or enzymatic and non-enzymatic redox systems, a further source of photon emission is reported which is independent of external oxygen, oxygen radicals and enzyme activities. Vital cells from rat brain homogenates or pig oligodendrocytes could be kept for hours at 37 degrees C without any photon emission. Only after disintegrative processes a cellular photon emission could be induced. The maximal intensity of about 400 impulses/s/mg protein and a total radiation of about 6 X 10(6) l/mg depended on the type of cells. The signal could be retained completely at 4 degrees C or in frozen samples. Heating (10 min, 90 degrees C) did not suppress the photon emission. Luminol and lucigenin did not amplify the signal as is usually observed in oxygen radical-producing cells. Non-specific radical scavengers as well as detergents suppressed the cellular photon emission completely. It is suggested that this cellular luminescence represents a biophysical radiation which originates from the interruption of an intermolecular radiationless energy transfer.

Normal rat serum cytotoxicity against syngeneic oligodendrocytes. Complement activation and attack in the absence of anti-myelin antibodies

The role of complement in mediating oligodendrocyte and myelin injury has been investigated by studying the effects of normal adult rat serum on syngeneic cultured neonatal glial cells. Rat serum has cytotoxic activity directed against oligodendrocytes but not astrocytes, the potency of which increases with cell maturation. The effects of heat inactivation, decomplemented rat serum, EGTA treatment, removal of any possible anti-myelin antibody by absorption using syngeneic myelin and absence of surface staining for immunoglobulins on serum-treated oligodendrocytes, C9 depletion and reconstitution, and oligodendrocyte staining for surface C9 demonstrate that this cytotoxicity is mediated by complement via antibody independent activation of the classical pathway and is membrane attack complex dependent. These findings significantly extend the previous demonstration of complement activation by extracted myelin, and may have significance for the pathogenesis of demyelinating diseases.

Experimental production of leptomeningeal heterotopias from dissociated fetal tissue

Subarachnoid heterotopias were produced experimentally in rats by intracisternal injection of dissociated fetal brain tissue. Heterotopias contained neurons and glial tissue and also mesodermal tissue including striated skeletal muscle. The data show that particles of disintegrated germinal tissue can survive, redistribute, settle and mature within the CSF spaces.

Biosynthesis of the neural cell adhesion molecule: characterization of polypeptide C

The biosynthesis of the neural cell adhesion molecule (N-CAM) was studied in primary cultures of rat cerebral glial cells, cerebellar granule neurons, and skeletal muscle cells. The three cell types produced different N-CAM polypeptide patterns. Glial cells synthesized a 135,000 Mr polypeptide B and a 115,000 Mr polypeptide C, whereas neurons expressed a 200,000 Mr polypeptide A as well as polypeptide B. Skeletal muscle cells produced polypeptide B. The polypeptides synthesized by the three cell types were immunochemically identical. The membrane association of polypeptide C was investigated with methods that distinguish peripheral and integral membrane proteins. Polypeptide C was found to be a peripheral membrane protein, whereas polypeptides A and B were integral membrane proteins with cytoplasmic domains of approximately 50,000 and approximately 25,000 Mr, respectively. The affinity of the membrane binding of polypeptide C increased during postnatal development. The posttranslational modifications of polypeptide C were investigated in glial cell cultures, and it was found to be N-linked glycosylated and sulfated.

Glial cells express N-CAM/D2-CAM-like polypeptides in vitro

The joining together of neurites to form fascicles and the growth of axons along glial surfaces during early development suggest that neurone-neurone and neurone-glial adhesion interactions are of considerable importance for defining nerve tracts. In vitro studies have indicated that adhesion between neurones involves a glycoprotein that has been independently studied under the names of N-CAM (for neural cell adhesion molecule), D2-CAM and BSP-2 (refs 10, 11). As N-CAM/D2-CAM appears to be a homophilic ligand that binds to N-CAM/D2-CAM polypeptide on adjacent cells, this glycoprotein is potentially important in adhesion interactions between any two N-CAM/D2-CAM-expressing cells. While it has been suggested that neurone-glial adhesion involves molecules other than N-CAM/D2-CAM, it is known that N-CAM/D2-CAM antigenic determinants are expressed by glial cells in vivo and that injection of anti-N-CAM antibodies into the eye-cup of chick embryos disrupts normal patterns of neuritic apposition to glial endfeet in the developing optic stalk. Do the molecules expressed by glia share restricted antigenic determinants, or binding domains, with N-CAM/D2-CAM, or are N-CAM/D2-CAM polypeptides expressed by glia? Here we present immunocytochemical evidence which suggests that all classes of macroglia express N-CAM/D2-CAM antigenic determinants on their surfaces and immunochemical analyses which indicate that the molecules expressed by purified astrocytes are closely similar, or identical, to at least some forms of N-CAM/D2-CAM obtained from whole brain or purified neurones. However, our results also suggest that different N-CAM/D2-CAM polypeptides may be separately expressed by neurones and astrocytes.

Immunocytochemical characterisation of cell cultures grown from dissociated 1-2-day post-natal rat cerebral tissue. A developmental study

A range of cell-specific markers have been employed with immunocytochemical methods to characterise and quantitate the cell types present in mixed brain cell cultures derived from dissociated 1-2-day post-natal rat cerebral hemispheres and grown in the presence of FCS. Protoplasmic astrocytes (GFAP+, A2B5-) were the major cell type to develop in culture, a confluent monolayer forming in 5-8 days. A population of smaller round cells of oligodendrocyte-like morphology appeared on this astrocyte layer. Greater than 70% of these smaller cells were GC- and thus were not oligodendrocytes. The GC- cells were A2B5+ and, in early cultures, may therefore be progenitor glial cells. Examination of GFAP and A2B5 co-expression by these smaller cells was difficult due to the dense underlying GFAP+ astrocyte layer. In less dense areas of older cultures these smaller cells with processes were GFAP+ and A2B5+: these are Type 2, fibrous astrocytes. GC+ oligodendrocytes, comprising 5-10% of the total identified cell population, were initially distributed over the astrocyte monolayer; in older cultures (after about 8 days) GC+ cells were observed in clumps over places where NF+ cells were identifiable. Such GC+ cells mostly became MBP+. Neurones accounted for about 6% of the identifiable cells in early cultures but a lower percentage in older cultures. Minor populations of ependymal cells and macrophages were present; cells displaying fibronectin, fibroblasts, were rarely identified. Use of horse serum in place of FCS gave lower yields of GC+ cells in cultures, slowed down astrocyte development, and resulted in the formation of trunks of GFAP+ cells throughout cultures. Other sera gave lower numbers of GC+ cells.

Infection of rat brain primary cell cultures with an avirulent A7 strain of Semliki Forest virus

The ability of A7 Semliki Forest Virus (SFV) to infect primary brain cell cultures has been examined using cultures prepared from 1-2-day neonatal rat cerebral hemispheres. These cultures, characterised immunocytochemically using cell-specified markers, contain mainly GFAP+ protoplasmic astrocytes and smaller multiprocessed A2B5+ cells, probably fibrous astrocytes. 10% of the cells are GC+ oligodendrocytes and some neurones are also present. These cultures support virus growth and a cytopathic effect was observed. Using double labelling techniques with the cell-specific markers and anti-SFV antibody A7 has been shown to readily infect cells which carry either the A2B5+ antigen or galactocerebroside marker. Protoplasmic astrocytes (GFAP+/A2B5-) are not readily infected under the conditions used. The protein labelling studies using [35S]methionine show that host cell protein synthesis is not completely shut off and continues in the astrocyte protein region. These results suggest that cells derived from a common A2B5+, GFAP-, GC- progenitor glial cell, i.e. GC+ oligodendrocytes and A2B5+/GFAP+ fibrous astrocytes, are more readily infected than other brain cell types including the protoplasmic astrocytes.

A novel myelin-associated glycoprotein defined by a mouse monoclonal antibody

A novel myelin antigen has been defined by a mouse monoclonal antibody (8-18C5) raised against rat cerebellar glycoproteins. By immunohistochemistry, the antigen was detected in white matter tracts of the central nervous system, but was absent from peripheral myelin. Western blotting followed by immunostaining revealed that the antigen was a glycoprotein of Mr 51 000 daltons which was degraded on storage to cross-reacting products of 20-26 000 daltons. Antigen was detected in central but not peripheral nervous system samples. Products of identical Mr were obtained by affinity chromatography of iodinated cerebellar glycoproteins on a column of immobilised 8-18C5.