Glia

Morcos, Yvette; Shorey, Cedric D.; Chan‐Ling, Tailoi

doi: 10.1002/(SICI)1098-1136(199907)27:1<1::AID-GLIA1>3.0.CO;2-Mpmid: 10401627

The barrier properties and glial ensheathment of blood vessels in the retinal myelinated streak of adult New Zealand White rabbits were characterized at the ultrastructural level by intravascular injection of horseradish peroxidase (HRP) and immuno‐electron microscopy with monoclonal antibody O4 and antibodies to glial fibrillary acidic protein (GFAP). Vessels within the myelinated streak did not leak HRP, and they exhibited tight junctions between adjacent endothelial cells. However, unlike their adult counterparts, the retinal blood vessels at postnatal day 18 exhibited substantial endocytotic activity. Both GFAP+ astrocytes and O4+ cells were evident surrounding the preretinal blood vessels of the myelinated streak. Furthermore, O4+ cells exhibited features indicative of high synthetic activity, including a large proportion of extended chromatin and prominent nucleoli within the nucleus, as well as a well‐developed Golgi apparatus and numerous mitochondria in the cytoplasm. O4+ cells also exhibited variable quantities of heterochromatin, indicative of early stages of cellular differentiation. These observations are consistent with previous data showing that O4+ cells in the myelinated streak include oligodendrocyte precursor cells, pre‐oligodendrocytes, and immature oligodendrocytes (Morcos Y, Chan‐Ling T. Glia 21:163–182, 1997). The present data indicate that the preretinal vessels of the myelinated streak possess barrier properties typical of microvasculature in the central nervous system, and that both O4+ cells and astrocytes contribute to the glial ensheathment of these vessels. These vessels thus differ markedly from the leaky preretinal vessels associated with pathological conditions such as retinopathy of prematurity. GLIA 27:1–14, 1999. © 1999 Wiley‐Liss, Inc.

Anderson, Emma S.; Bjartmar, Carl; Westermark, Gunilla; Hildebrand, Claes

doi: 10.1002/(SICI)1098-1136(199907)27:1<15::AID-GLIA2>3.0.CO;2-Ipmid: N/A

The classical studies by Del Rio Hortega (Mem. Real. Soc. Espan. Hist. Nat. 14:40–122, 1928) suggest that the oligodendrocyte population includes four morphological subtypes. Recent data from the cat and the rat show that the anatomy of oligodendrocytes related to early myelinating prospective large fibers differs from that of oligodendrocytes related to late myelinating prospective small fibers. After application of a polyclonal antiserum to cryostat sections from the chicken CNS, we noted that glial cells in the spinal cord white matter had become labeled. Analysis of the occurrence and cellular localization of this immunoreactivity—the T4‐O immunoreactivity—in the CNS of the adult chicken showed that T4‐O immunoreactive cells are enriched in the ventral funiculus and superficially in the lateral funiculus of the spinal cord, where they are co‐localized with large fibers. Double staining with T4‐O antiserum and anti‐GFAP or the lectin BSI‐B4 revealed that T4‐O immunoreactive cells are not astrocytes or microglia. Staining with anti‐HSP108, a general marker for avian oligodendrocytes, showed that T4‐O immunoreactivity defines an oligodendroglial subpopulation. A search for T4‐O immunoreactivity in spinal cord white matter of some other vertebrates revealed that T4‐O immunoreactive cells are not present in sections from fish, frog, turtle, rat, and rabbit spinal cord white matter. These results suggest the presence of a fiber size‐related molecular heterogeneity among chicken white matter oligodendrocytes. GLIA 27:15–21, 1999. © 1999 Wiley‐Liss, Inc.

Bowman, Charles L.; Yohe, Lori; Lohr, James W.

doi: 10.1002/(SICI)1098-1136(199907)27:1<22::AID-GLIA3>3.0.CO;2-Fpmid: 10401629

We monitored the volume of C6 glioma cells in suspension using a Coulter Counter and exposed the cells to micromolar or nanomolar levels of collagenase or clostripain. In 13 experiments, type IV collagenase (310 units ml−1; ∼3 μM L−1) decreased the volume by 8–12%, 8 min after addition. In 13 of 21 experiments, the volume decrease was followed by a volume regulatory increase (VRI) back to control levels in the continued presence of collagenase. The shrinkage evoked by type IV collagenase was eliminated by heat‐inactivation of the enzyme preparation. A highly purified collagenase (type VII) at the same concentration evoked a relatively minor decrease in volume. A well‐known contaminating protease present in type IV collagenase, clostripain, which specifically cleaves arginyl peptide bonds, evoked a 7 ± 2% shrinkage (100 nM L−1, 7 experiments). Clostripain did not evoke a volume regulatory increase. The initial velocity of shrinkage evoked by clostripain (0.0012 pL min−1, 0.0034 pL min−1, 0.0132 pL min−1; 1 pL = 10−12 liters) scaled with its concentration (1 nM L−1, 10 nM L−1, 100 nM L−1). The effect of clostripain was inhibited by heat‐inactivation of the enzyme. Leupeptin, an inhibitor of clostripain, prevented the decrease in volume evoked by clostripain. The activity of stretch‐activated ion channels was unaffected by type IV collagenase. Barium, cesium, amiloride, DIDS, or bumetanide failed to block the shrinkage evoked by type IV collagenase. These results demonstrate that clostripain, present in crude collagenase enzyme preparations, causes the shrinkage, and that C6 glioma cells can undergo a volume regulatory increase at virtually constant osmotic pressure. In addition, cleavage of a cell surface moiety, which contains arginine, and possibly proline, causes shrinkage. This moiety may be part of the extracellular or intracellular matrix providing mechanical support to the cells. VRI reflect actions of another substance in the type IV crude collagenase preparations, on a receptor independent of the arg–pro moiety. The enzymatic modulation of glioma cell volume by these two receptors may reflect a new mechanism by which such cells, and possibly other glia, regulate their contact area and interactions with other cells in the central nervous system. GLIA 27:22–31, 1999. © 1999 Wiley‐Liss, Inc.

Schmidt, Joachim; Prinz, Petra; Deitmer, Joachim W.

doi: 10.1002/(SICI)1098-1136(199907)27:1<32::AID-GLIA4>3.0.CO;2-9pmid: 10401630

Hyperpolarizing responses in neuropil glial cells evoked by nerve root stimulation were studied in the central nervous system of the leech Hirudo medicinalis using intracellular recording and extracellular stimulation techniques. From a mean resting potential of −60.5 ± 1.0, the glial membrane was hyperpolarized by −8.6 ± 0.8 mV, via stimulation of the dorsal posterior nerve root in an isolated ganglion. Nerve root stimulation evoked biphasic or depolarizing responses in glial cells with resting potentials around −70 mV (Rose CR, Deitmer JW. J. Neurophysiol. 73:125–131, 1995). The hyperpolarizing response was reduced by the ionotropic glutamate receptor antagonist CNQX (50 μM) to 58% of its initial amplitude. In 15 mM Ca2+/15 mM Mg2+‐saline the hyperpolarization was reduced by 44%. The hyperpolarization that persisted in high‐divalent cation saline was not affected by CNQX. Bath‐applied glutamate (500 μM) and kainate (2 μM) elicited glial hyperpolarizations that were sensitive to CNQX and 10 mM Mg2+/1 mM Ca2+‐saline. The 5‐HT‐antagonist methysergide did not affect the hyperpolarizations evoked by nerve root stimulation. The results show that in the leech glial membrane responses to neuronal activity include not only depolarizations, as shown previously, but also hyperpolarizations, which are mediated by direct and indirect neuron–glial communication pathways. In the indirect pathway, glutamate is a transmitter between neurons. GLIA 27:32–38, 1999. © 1999 Wiley‐Liss, Inc.

Mikol, Daniel D.; Hong, Hoylond L.; Cheng, Hsin‐Lin; Feldman, Eva L.

doi: 10.1002/(SICI)1098-1136(199907)27:1<39::AID-GLIA5>3.0.CO;2-#pmid: N/A

Caveolae are non‐clathrin‐coated invaginations of the plasma membrane, which are present in most cell types. An integral component of caveolae is the caveolin family of related proteins, which not only forms the structural framework of caveolae, but also likely subserves its functional roles, including regulation of signal transduction and cellular transport, in particular, cholesterol trafficking. Although caveolae have been identified ultrastructurally in the peripheral nervous system (PNS), caveolin expression has not previously been studied. To date, three caveolin genes have been reported. Here, we show for the first time that caveolin‐1 is expressed by Schwann cells (SC) as well as several SC‐derived cell lines. Caveolin‐1 is enriched in the buoyant, detergent‐insoluble membranes of rat sciatic nerve (SN) and SC, a hallmark of the caveolar compartment. Caveolin‐1 exists as both soluble and insoluble forms in rat SN and SC, and localizes to SC cytoplasm and abaxonal myelin. SC caveolin‐1 decreases after axotomy, when SC revert to a premyelinating phenotype. We speculate that caveolin‐1 may regulate signal transduction and/or cholesterol transport in myelinating SC. GLIA 27:39–52, 1999. © 1999 Wiley‐Liss, Inc.

Liuzzi, Grazia M.; Santacroce, Maria P.; Peumans, Willy J.; Van Damme, Els J.M.; Dubois, Bénédicte; Opdenakker, Ghislain; Riccio, Paolo

doi: 10.1002/(SICI)1098-1136(199907)27:1<53::AID-GLIA6>3.0.CO;2-Xpmid: 10401632

The effects of 25 recently discovered plant lectins on cell proliferation and enzyme release were compared to those of previously known lectins on rat microglia and astrocyte cell cultures. A dose‐dependent proliferation of microglial cells, but not of astrocytes, was induced by seven lectins, whereas five lectins showed dose‐dependent cytotoxicity on both microglia and astrocyte cell cultures. The activity of gelatinase B (MMP‐9) was strongly increased in microglial cells by the aforementioned seven lectins, by concanavalin A, and by phytohemagglutinin (PHA‐E4), whereas gelatinase A (MMP‐2) remained at constitutive levels. The five cytotoxic lectins decreased the activity of gelatinase B in microglia and of gelatinase A in astrocytes, in a dose‐dependent manner. The lectin wheat germ agglutinin induced a decrease in gelatinase B activity in microglia, but stimulated gelatinase A and B activity in astrocytes. These results indicate that lectins possess neuromodulatory effects that may motivate the study of their effects on central nervous system (CNS) function in vivo. This, in turn, may lead to better insight into whether lectin or lectin‐like molecules can interact with glial cells, and whether they have a role in acute toxicity and in multifactorial diseases in which environmental factors may play a role. GLIA 27:53–61, 1999. © 1999 Wiley‐Liss, Inc.

Bechmann, Ingo; Mor, Gil; Nilsen, Jon; Eliza, Mariel; Nitsch, Robert; Naftolin, Frederick

doi: 10.1002/(SICI)1098-1136(199907)27:1<62::AID-GLIA7>3.0.CO;2-Spmid: 10401633

Despite the mechanical blood‐brain barrier, activated T‐cells can cross brain vessels. Thus, the CNS is routinely surveyed by immune competent cells; yet the healthy brain is not a target of antigen‐specific immune reactions. Therefore, mechanisms must exist to prevent brain‐antigen‐specific T‐cells from inducing immune responses. Data indicate that activated T‐cells entering the CNS may undergo apoptosis rather than leaving the brain to induce immune responses. Applying RT‐PCR, Western‐blots, and immunocytochemistry, we have demonstrated expression of the apoptosis‐inducing protein Fas ligand on astrocytes and neurons of apparently normal rat and human brains. FasL‐positive astrocytes were often situated in close vicinity to cerebral blood vessels in vivo and induced apoptosis of Fas expressing Jurkat cells in vitro. We propose that similar to other immune privileged organs FasL‐induced apoptosis of activated T‐cells in the brain protects the tissue from self damaging immune attacks by forming an immunological brain barrier. GLIA 27:62–74, 1999>. © 1999 Wiley‐Liss, Inc.

Lemke, Rainer; Hartlage‐rübsamen, Maike; Schliebs, Reinhard

doi: 10.1002/(SICI)1098-1136(199907)27:1<75::AID-GLIA8>3.0.CO;2-Jpmid: N/A

Interleukins (IL)‐1α, β and IL‐6 may play essential roles in early inflammatory processes in response to degenerating cholinergic cells observed in the basal forebrain of Alzheimer patients. To address this question in vivo, two distinct lesion paradigms were used. A specific and selective basal forebrain cholinergic cell loss was achieved by a single intracerebroventricular application of the cholinergic immunotoxin, 192IgG‐saporin. Intrahippocampal injection of lipopolysaccharide and interferon‐γ was used to produce an exogenously‐induced acute inflammation in the brain. In order to disclose the lesion‐induced temporal cascade of the expression pattern of IL‐1α, IL‐1β, and IL‐6, and the cell types expressing IL‐1α, β/IL‐6 mRNA, Western analysis, RT‐PCR, and double labeling immunocytochemistry were applied. In the intact brain, IL‐6, IL‐1α and IL‐1β demonstrated a constitutive expression in neurons. Following cholinergic lesion neither IL‐1β nor IL‐6 expression could be detected in any of the activated glial cell types, whereas IL‐1α was found to be expressed in astroglial cells only. In contrast, hippocampal administration of lipopolysaccharides/interferon‐γ resulted in expression of IL‐1α in microglial but not astroglial cells. These in vivo studies clearly demonstrate that the cellular expression of IL‐1α, IL‐1β, and IL‐6 in the brain is differentially regulated depending on the kind of injury producing the inflammatory response in the brain. The data suggest that each glial cell seems to be equally capable of expressing a number of various cytokines, but it depends on the kind of stimulus which temporal and cellular cascade of cytokine expression pattern is initiated under a particular pathological condition in the brain. GLIA 27:75–87, 1999. © 1999 Wiley‐Liss, Inc.

Kafitz, Karl W.; Güttinger, Hans R.; Müller, Christian M.

doi: 10.1002/(SICI)1098-1136(199907)27:1<88::AID-GLIA9>3.0.CO;2-Apmid: N/A

In the song control area HVc of the canary, intercellular dye‐coupling among astrocytes was studied by intracellular injection of neurobiotin into identified single astrocytes. Injection of individual astrocytes into acute slices resulted in dye spread to neighboring astrocytes, covering a sphere of up to 1 mm in diameter. The astrocytic nature of the dye‐coupled cells was verified by double labeling of neurobiotin‐filled cells with antisera for the astrocytic filament proteins GFAP or vimentin. The similarity in the number of dye‐coupled cells and the total number of astrocytes labeled by immunocytochemical markers indicate that dye‐coupling is specific for astrocytes and labels almost the entire local astrocytic population. Within the major nucleus for vocal control (HVc), approximately 25% more astroglial cells were present than in the surrounding forebrain tissue. There is no apparent hindrance of dye spread at the border of the HVc. The density of dye‐coupled astrocytes and the expression of cytoskeletal filament proteins differed markedly between the reproductive period in spring and the quiescent period in autumn. While vimentin is the major astroglial filament in autumn, GFAP is strongly expressed in spring. The density of dye‐coupled astrocytes reveals a marked increase in the reproductive period, followed by a reduction in autumn. The data indicate that the astrocytic population in the avian forebrain undergoes significant changes coincident with the known functional changes in the vocal control nuclei during periods of song production. GLIA 27:88–100, 1999. © 1999 Wiley‐Liss, Inc.