摘要:

AbstractNeurotransmitters which increase intracellular cAMP levels can cause cultured astroglia to change from a flat, polygonal shape to a stellate morphology. Little is known about how glial stellation can be regulated by other transmitters. In the present study, we demonstrated that L‐glutamate blocked isoproterenol (ISO) or dibutyryl‐cAMP induced stellation in astroglia. The glutamate inhibition was concentration dependent, with its maximal effect on>90% of cells at 500 μM. Glutamate also reversed glial stellation within a short period (<30 min). Glutamate uptake analogues, D‐glutamate and D‐aspartate, rather than receptor agonists, kainate and quisqualate, mimicked the glutamate effect. Likewise, the glutamate uptake blocker, D‐thero‐ß‐hydroxyaspartate, blocked the glutamate effect. The glutamate inhibition was not a result of inhibition of cAMP formation, since norepinephrine, which inhibited 80% of ISO‐stimulated cAMP, also caused glial stellation. Increases in extracellular K+to 50 mM also reduced glial stellation, whereas 25 mM K+had little effect. Since 25 mM K+caused much greater depolarization than 400 μM glutamate, it was unlikely that the effects of both glutamate and high [K+] on glial stellation were due to membrane depolarization. Hypotonic treatment (120 mOsm) enhanced, whereas hypertonic treatment (520 mOsm) prevented, the glutamate reversal of glial stellation. Thus, glial swelling appeared to be a primary mechanism for the inhibitory effect of glutamate and high [K+] on glial stellation. This mechanism could also explain the observation that glutamate inhibited stellation induced by PMA, a PKC activator. Our data suggest that glutamate released from neurons during neuronal activity or pathology can be taken up by astrocytes and alter their morphology. Changes in glial morphology may in turn affect the volume and composition of the extracellular space and, as a result, neuronal activity. © 1

ISSN:0894-1491    

DOI:10.1002/glia.440110103

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractMicroglia develop in cultures initiated from disaggregated neopallial cells of newborn C3H/HeJ mice when the cultures are subjected to nutritional deprivation for 10 or more days (Hao et al: Int J Dev Neurosci 9:1‐14, 1991). In the present experiments, the cultures were pulsed with BrdU for 3 hours at different times during incubation and then the cells were immunoreacted with antibodies against BrdU, GFAP, and CR3 receptor. The dividing cells (BrdU+) were found to be either GFAP+or GFAP−, but not Mac‐1+/BrdU+. Infection of proliferating cells after 2 or more days of incubation with replication‐deficient retroviral vector containingE. colilacZ reporter gene resulted in many labeled astroglia cell clones but no labeled microglia. However, when cells were infected right after disaggregation of neopallium, labeled Mac‐1+microglia were found. When Mac‐1+cells in a suspension of disaggregated neopallial cells were killed using complement mediated lysis before setting up the cultures, Mac‐1+microglia developed, in spite of the treatment. We conclude that in cultures initiated from mouse neopallium there are MAC‐1−/GFAP−microglia progenitor cells which do not divide in nutritionally deprived cultures but can transform into Mac‐1+microglia under the influence of astroglia‐derived trophic factors. Microglia, which become Mac‐1+(i.e., express CR3 receptor), proliferate extensively in the presence of CSF‐1 (which is produced by astrogl

ISSN:0894-1491    

DOI:10.1002/glia.440110104

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractThe neurotoxic drugp‐chloramphetamine (PCA) causes widespread de‐generation offine, unmyelinated serotonergic (5‐HT) axons in the forebrain. PCA toxicity is selective for 5‐HT axon terminals; preterminal axons and cell bodies are spared. Degeneration is followed by slowly progressive axonal sprouting and partial reinnervation. PCA is injected subcutaneously; this route of administration avoids mechanical disruption of the blood brain barrier. The present study analyzed the response of microglia and astrocytes in rat brain to selective ablation of 5‐HT axons by PCA. Several microglial markers were analyzed with immunocytochemical methods. An increase in the number of microglial processes and in immunoreactive staining was observed with antibodies directed against CR‐3, MHC‐I, CD4, and rat LCA. The microglial response was maximal 3 weeks after PCA treatment, became less evident 6 weeks after treatment, and by 9 weeks no difference was observed between treated and control rats. No change was detected in MHC‐II or the macrophage marker ED1, nor in expression of GFAP by astrocytes. Thus, degeneration of 5‐HT axon terminals affects only a subset of the micro‐glial markers examined; in comparison, retrograde reaction to facial nerve transection causes a robust increase in all of these markers and in GFAP. The microglial response to PCA‐induced axon loss is slow in onset and small in magnitude. These findings indicate that CNS microglia are activated by degeneration of fine, unmyelinated 5‐HT axon terminals; furthermore, sensitive microglial markers can detect a subtle axonal lesion that provokes no detectable increase in GFAP expression by astrocytes.

ISSN:0894-1491    

DOI:10.1002/glia.440110105

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractThe HMGCR gene encodes the 3‐hydroxy‐3‐methylglutaryl coenzyme A reductase, which is the key enzyme for cholesterol synthesis. Mice transgenic for the prokaryotic chloramphenicol acetyl transferase (CAT) reporter gene fused with a 5′ Bam H1 fragment including the promoter sequence for murine HMGCR gene have been obtained. Homozygote transgenic mice were derived from a particular line selected for similar regulation of endogenous HMGCR and the transgene expression by nutritional conditions in different tissue. In addition, high expression of the transgene was evidenced in the brain. Cellular expression of the CAT gene in the central nervous system (CNS) was investigated by immunohistochemistry (IHC). This study was performed on frozen sections of the developing and adult brain, using a rabbit anti‐CAT antiserum especially raised for that purpose. CAT expression was observed in some rare individuals in different neural cell types including Purkinje cells and astrocytes. But the most outstanding observation was the high level of CAT expression correlated with differentiated pattern of oligodendrocyte (01) distribution observed in white‐matter tracts. Double and triple labeling for CAT and stage‐specific antigens were performed on transgenic Ol‐enriched preparations and cultures. This study showed a normal sequence of differentiation in the transgenic oligodendroglial cell lineage and demonstrated a strict correlation between late differentiation and activation of the CAT gene in these cells: CAT expression started in transgenic Ols between galactocerebroside (GC)‐positive and myelin basic protein (MBP)‐positive stages and was detected in MBP‐positive cells during the myelination period. After myelination, the number of CAT‐positive Ols decreased in the adult brain. These observations demonstrate a developmental regulation of the CAT transgene in Ols during myelination in CNS and reinforce the hypothesis of endogenous synthesis as major source of cholesterol during myelination.

ISSN:0894-1491    

DOI:10.1002/glia.440110106

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractFibroblast growth factor (FGF) is synthesized and stored by astroglial cells and regulates their proliferation and differentiation in vitro. Its implication in the transformation of quiescent astrocytes into reactive astroglia has been discussed. Using a mouse model of Parkinson's disease, in which FGF‐2 has been shown to exert marked neuroprotection of nigrostriatal dopaminergic neurons, we have studied striatal levels of glial fibrillary acidic protein (GFAP), an established marker for astrocytes, and the distribution and morphologies of GFAP‐immunoreactive cells following treatments with the neurotoxic drug 1‐methyl‐4‐phenyl‐1,2,3,6‐tetrahydropyridine (MPTP), the growth factor FGF‐2, and the non‐trophic control protein cytochrome C (cyt C). Systemic injections of MPTP (30 mg/kg) on 3 consecutive days, which we have previously shown to cause profound and long‐lasting damage to the nigrostriatal system, induced an approximate 20% transient increase in striatal GFAP, determined by enzyme‐linked immunosorbent assay (ELISA), 1 day after the final MPTP injection (= day 4), with subsequent normalization at day 7, which lasted until the end of the experiment (day 18). Morphologically, MPTP elicited a marked increase in number, size, arborization, and stainability of GFAP‐immunoreactive cells at day 4 in a striatal area adjacent to the corpus callosum, which was evaluated throughout all experiments. Even on day 18, astrocytes were still apparently larger and more branched than in unlesioned controls. Administration of 4 μg of either FGF‐2 or cyt C (soaked into a piece of Gelfoam unilaterally to the right striatum in either MPTP‐ or saline‐injected controls) increased striatal GFAP levels bilaterally about 2‐ to 2.5‐fold at 14 days, when FGF‐2 showed marked protection of dopaminergic parameters. Likewise, GFAP immunocytochemistry revealed increased numbers of intensely immunoreactive astrocytes under any experimental situation. Differences in the morphologies of astrocytes in FGF‐2‐ and cyt C‐treated animals were very subtle and only noted at greater distances away from the site of application of the factors. We conclude that FGF‐2, a potent neurotrophic factor for the neurotoxically lesioned nigrostriatal system, does not cause a marked astrogliotic reaction, which might be expected from previous in vitro and in vivo studies in other neural systems. This may limit concerns regarding potential applicability of FGF‐2 to the

ISSN:0894-1491    

DOI:10.1002/glia.440110107

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractWe have studied the behaviour of living, process‐bearing astrocytes in vitro, observing groups of cells at daily intervals for up to 7 days. Each cell initially formed two processes, appearing bipolar in shape, and with further time in culture, grew additional processes and appeared stellate. As their processes grew, the interactions between astrocytes underwent characteristic changes. While bipolar, the cells appeared to avoid making contact, lying parallel to each other. As they became stellate, the astrocytes made extensive contact with neighbours, gradually forming extended, contacting networks in which their somas were regularly spaced (as previously described). The interactions which led to the establishing of such arrays were also evident. If two cells were initially close or adjacent, they extended short processes to contact each other; then, as their processes grew, their somas moved apart, until they were separated by 60‐120 μm. If two cells were initially well separated, each directed processes towards the other until contact was made, often with striking precision, and their somas then moved together, until they were separated by 60‐120 μm. These behaviours of contact, separation, and approach caused astrocytes to form clusters, within which their somas appeared regularly spaced, and may represent the interactions which occur among astrocytes during normal development to produce the regularly spaced arrays of astrocytes described in earlier studies of intact central nervous tissue. © 1994 Wiley

ISSN:0894-1491    

DOI:10.1002/glia.440110108

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractPatch clamp techniques were used to study whole cell ionic currents in Schwann cells (SC) from a tropical marine fish, the bicolor damselfish,Pomacentrus partitus.The bicolor damselfish is affected by a disease termed damselfish neurofibromatosis (DNF), being developed as an animal model of neurofibromatosis‐type 1 (NF1) in humans. NF1 affects SC, fibroblasts, and perineurial cells. The sole depolarization‐activated ionic current present in cultured SC from normal fish peripheral nerve and from neurofibromas of fish with induced or spontaneously occurring DNF was an inactivating K+current (K current), with a strong dependence on the Nernst potential for K+. This K current activated at depolarizations to ‐40 mV and above and inactivated during a maintained test pulse (0.2‐1 s), but inactivation was significantly greater in tumored SC. Both currents were inhibited by 4‐aminopyridine (Kd 1 mM) and by dendrotoxin (15 μM) but were insensitive to extracellular tetraethyammonium (≤ 150 mM), indicating that the whole cell currents were similar pharmacologically. The currents could be distinguished on the basis of their sensitivity to depolarized holding potential, with normal cells less sensitive. Half‐inactivation of the current was ‐32 mV in normal cells and ‐38 mV in tumored cells. Inactivation curves constructed from the average normalized current for many SC were significantly different in normal and tumored cells. When the depolarized holding potential was maintained between test depolarizations, greater voltage‐dependent inactivation in tumored cells was apparent. Normal cells maintained an average of 36% of peak current at a holding voltage of −40 mV, while in tumored cells this average was 12%, a significant difference

ISSN:0894-1491    

DOI:10.1002/glia.440110109

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractRats reared from weaning in a complex environment have an increase in (1) glial surface area, (2) capillary volume, and (3) the number of synapses, per neuron. In that paradigm it has not been possible to determine whether the glial increase more closely correlates with the increase in synaptic numbers or with angiogenesis. More recently we have found that rats that exercised had an increase in the density of capillaries without an increase in the synaptic numbers, whereas rats that learned new motor skills had a greater number of synapses per neuron without an increase in the density of capillaries. Those findings provided the opportunity to investigate whether changes in glial volume in the cerebellum correspond to changes in the number of synapses or in capillary volume. Glial area fraction estimates were obtained using point counts on electron micrographs from the previous studies. The skill learning group had a greater volume of molecular layer per Purkinje cell, and also a greater volume of glia per Purkinje cell, than rats in either an inactive group or rats in two exercise groups. No significant differences were found in glial volume per synapse and glial volume per capillary across groups, although there was a tendency for glial volume per capillary to be lower in the exercise groups. The data indicate that glial volume correlates with synaptic numbers and not with capillary density. © 1994 Wiley‐Liss, I

ISSN:0894-1491    

DOI:10.1002/glia.440110110

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

ISSN:0894-1491    

DOI:10.1002/glia.440110102

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY