Type-2 Astrocytes Research Articles

Zebrafish Astroglial Morphology in the Olfactory Bulb Is Altered With Repetitive Peripheral Damage.

Zebrafish do not possess the typical astrocytes that are found in mammalian systems. In some brain areas, this teleost has radial glia that appears to perform astrocyte-like functions, but these cells have not been described in the zebrafish olfactory bulb. Mammalian astrocytes facilitate neuroplasticity and undergo astrogliosis after insult. The role of these cells in the zebrafish olfactory system after the damage has been poorly explored. This is important to examine because zebrafish have a high degree of neuroplasticity and the olfactory bulb is a brain area renowned for plasticity. The goal of this study was to explore the potential role of zebrafish astrocytes in the olfactory bulb damage response, with a goal to exploit the high level of regeneration in this system. We found that anti-glial fibrillary acidic protein (GFAP) labels numerous processes in the zebrafish olfactory bulb that are concentrated in the nerve and glomerular layers (GL) and do not show radial glial-like morphology. We propose to term this astroglia, since their location and response to damage suggests that they are similar in function to the mammalian astrocyte. To induce repetitive peripheral damage to the olfactory organ, a wax plug was inserted into the nasal cavity of adult zebrafish every 12 h for up to 7 days; this crushes the olfactory organ and leads to degradation of olfactory sensory neuron axons that project to the olfactory bulb. After 1 day, we found a significant increase in astroglial labeling in the affected bulb when compared to the internal control bulb and astroglial branches appeared to increase in number and size. By the third day of plug insertions there was no significant difference in astroglial labeling between the affected bulb and the internal control bulb. These data lead us to believe that astrogliosis does occur in the presence of peripheral damage, but this process attenuates within 1 week and no glial scar is evident upon recovery from the damage. Further exploration of astrocytes in zebrafish, in particular this apparent attenuation of astrogliosis, has the potential to elucidate key differences in glial function between teleosts and mammals.

Reprogramming Fibroblasts to Neural Stem Cells by Overexpression of the Transcription Factor Ptf1a.

Neural stem cells (NSCs) have the features of both neural progenitors and stem cells, and show great potentials in translational research and regenerative medicine. Studies on NSCs have been greatly accelerated by the introduction of induced neural stem cells (iNSCs). The iNSCs are usually differentiated from induced pluripotent stem cells (iPSCs) or transdifferentiated from somatic cells such as fibroblasts or glial cells. Here, we describe a detailed protocol to reprogram human and mouse fibroblasts into iNSCs by overexpression of a transcription factor Ptf1a delivered by lentiviruses. The obtained iNSC lines have a strong self-renewal ability and are capable of differentiating into various types of neurons, astrocytes, and oligodendrocytes both in vitro and in vivo. The protocol is quite simple but powerful to produce iNSC lines.

Single-Cell Analysis for Glycogen Localization and Metabolism in Cultured Astrocytes

Cerebral glycogen is principally localized in astrocytes rather than in neurons. Glycogen metabolism has been implicated in higher brain functions, including learning and memory, yet the distribution patterns of glycogen in different types of astrocytes have not been fully described. Here, we applied a method based on the incorporation of 2-NBDG, a d-glucose fluorescent derivative that can trace glycogen, to investigate glycogen’s distribution in the brain. We identified two types of astrocytes, namely, 2-NBDGI (glycogen-deficient) and 2-NBDGII (glycogen-rich) cells. Whole-cell patch-clamp and fluorescence-activated cell sorting (FACS) were used to separate 2-NBDGII astrocytes from 2-NBDGI astrocytes. The expression levels of glycogen metabolic enzymes were analyzed in 2-NBDGI and 2-NBDGII astrocytes. We found unique glycogen metabolic patterns between 2-NBDGI and 2-NBDGII astrocytes. We also observed that 2-NBDGII astrocytes were mainly identified as fibrous astrocytes but not protoplasmic astrocytes. Our data reveal cell type-dependent glycogen distribution and metabolism patterns, suggesting diverse functions of these different astrocytes.

Expression Patterns of Inducible Cre Recombinase Driven by Differential Astrocyte-Specific Promoters in Transgenic Mouse Lines.

Astrocytes are the most abundant cell type in the central nervous system (CNS). They provide trophic support for neurons, modulate synaptic transmission and plasticity, and contribute to neuronal dysfunction. Many transgenic mouse lines have been generated to obtain astrocyte-specific expression of inducible Cre recombinase for functional studies; however, the expression patterns of inducible Cre recombinase in these lines have not been systematically characterized. We generated a new astrocyte-specific Aldh1l1-CreERT2 knock-in mouse line and compared the expression pattern of Cre recombinase between this and five widely-used transgenic lines (hGfap-CreERT2 from The Jackson Laboratory and The Mutant Mouse Resource and Research Center, Glast-CreERT2, Cx30-CreERT2, and Fgfr3-iCreERT2) by crossing with Ai14 mice, which express tdTomato fluorescence following Cre-mediated recombination. In adult Aldh1l1-CreERT2:Ai14 transgenic mice, tdTomato was detected throughout the CNS, and five novel morphologically-defined types of astrocyte were described. Among the six evaluated lines, the specificity of Cre-mediated recombination was highest when driven by Aldh1l1 and lowest when driven by hGfap; in the latter mice, co-staining between tdTomato and NeuN was observed in the hippocampus and cortex. Notably, evident leakage was noted in Fgfr3-iCreERT2 mice, and the expression level of tdTomato was low in the thalamus when Cre recombinase expression was driven by Glast and in the capsular part of the central amygdaloid nucleus when driven by Cx30. Furthermore, tdTomato was clearly expressed in peripheral organs in four of the lines. Our results emphasize that the astrocyte-specific CreERT2 transgenic lines used in functional studies should be carefully selected.

Reaction of Human Neocortex Astrocytes to Clinical Death and Reperfusion

The aimof research was to study the effect of clinical death and reperfusion on astrocytes of the human cerebral cortex.Material and methods.Structural types, quantity, shape, size and distribution of cortical layers I–VI astrocytes (fields 4, 10, 17 and 21) were studied in 7 days after 3-minute clinical death (n=3, males) using a confocal microscope, fluorescence immunohistochemistry (GFAP), classical morphometry and fractal analysis. The control group (n=4, males) included patients died from severe traumatic brain injury.Results.A complex integrated system of GFAP-positive cells consisting of translaminar and intralaminar astrocytes of the fibrous, protoplasmic and mixed types, was revealed in the human cerebral cortex. The bodies of translaminar astrocytes were localized in layers I (had smooth long thin processes) and layers V–VI (had processes with varicose thickening). The processes of translaminar astrocytes penetrated towards each other and intertwined at the level of layer I and II. Qualitative and quantitative changes of all types of intralaminar and translaminar astrocytes were revealed in the human cerebral cortex in 7 days after clinical death. The percentage of the GFAP-positive area increased in all layers of the studied cerebral cortex departments. An increase in GFAP expression in cortical astrocytes was accompanied by changes in the fractal distribution and lacunarity of their processes distribution, the fact supporting a spatial reorganization of the astroglial network in response to acute ischemia and reperfusion of the brain. To a greater extent this related to the processes of fibrous perivascular astrocytes. All these manifestations of reactive astrogliosis might be associated with the activation of adaptivereparative processes in astrocytes. No statistically significant differences between the cerebral cortex fields were revealed.Conclusion.The results obtained showed that clinical death and reperfusion resulted in a structuralfunctional reorganization of the neuroglial network of the cerebral cortex accompanied by an increase in the GFAF expression and complication of the spatial distribution of the processes in all types of astrocytes.

Predicting Reactive Astrogliosis Propagation by Bayesian Computational Modeling: the Repeater Stations Model.

Reactive astrogliosis occurs upon focal brain injury and in neurodegenerative diseases. The mechanisms that propagate reactive astrogliosis to distal parts of the brain, in a rapid wave that activates astrocytes and other cell types along the way, are not completely understood. It is proposed that damage-associated molecular patterns (DAMP) released by necrotic cells from the injury core have a major role in the reactive astrogliosis initiation but whether they also participate in reactive astrogliosis propagation remains to be determined. We here developed a Bayesian computational model to define the most probable model for reactive astrogliosis propagation. Starting with experimental data from GFAP-immunostained reactive astrocytes, we defined five types of astrocytes based on morphometrical cues and registered the position of each reactive astrocyte cell type in the hemisphere ipsilateral to the injured site after 3 and 7days post-ischemia. We developed equations for the changes in DAMP concentration (due to diffusion, binding to receptors or degradation), soluble mediators secretion, and for the evolution reactive astrogliosis. We tested four predefined models based on abovementioned previous hypothesis and modifications to it. Our results showed that DAMP diffusion alone has not justified the reactive astrogliosis propagation as previously assumed. Only two models succeeded in accurately reproducing the experimentally measured data and they highlighted the role of microglia and the glial secretion of soluble mediators to sustain the reactive signal and activating neighboring astrocytes. Thus, our in silico analysis proposes that glial cells behave as repeater stations of the injury signal in order to propagate reactive astrogliosis.

Ketamine Within Clinically Effective Range Inhibits Glutamate Transmission From Astrocytes to Neurons and Disrupts Synchronization of Astrocytic SICs.

BackgroundAstrocytes are now considered as crucial modulators of neuronal synaptic transmission. General anesthetics have been found to inhibit astrocytic activities, but it is not clear whether general anesthetics within the clinical concentration range affects the astrocyte-mediated synaptic regulation.MethodsThe effects of propofol, dexmedetomidine, and ketamine within clinically effective ranges on the slow inward currents (SICs) were tested by using the whole-cell recording in acute prefrontal cortex (PFC) slice preparations of rats. Astrocytes culture and HPLC were used to measure the effects of different anesthetics on the glutamate release of astrocytes.ResultsPropofol and dexmedetomidine showed no significant effect on the amplitude or frequency of SICs. Ketamine was found to inhibit the frequency of SICs in a concentration-dependent manner. The SICs synchronization rate of paired neurons was inhibited by 30 μM ketamine (from 42.5 ± 1.4% to 9.6 ± 0.8%) and was abolished by 300 μM ketamine. The astrocytic glutamate release induced by DHPG, an agonist of astrocytic type I metabotropic glutamate receptors, was not affected by ketamine, and ifenprodil, a selective antagonist of GluN1/GluN2B receptor, blocked all SICs and enhanced the inhibitory effect of 30 μM ketamine on the frequency of SICs. Ketamine at low concentration (3 μM) could inhibit the frequency of SICs, not the miniature excitatory postsynaptic currents (mEPSCs), and the inhibition rate of SICs was significantly higher than mEPSCs with 30 μM ketamine (44.5 ± 3% inhibition vs. 28.3 ± 6% inhibition).ConclusionOur data indicated that ketamine, not propofol and dexmedetomidine, within clinical concentration range inhibits glutamatergic transmission from astrocytes to neurons, which is likely mediated by the extrasynaptic GluN1/GluN2B receptor activation.

Intracellular labile zinc is a determinant of vulnerability of cultured astrocytes to oxidative stress

Recently, we found that treatment of cultured mouse astrocytes of ddY-strain mice (ddY-astrocytes) with 400 μM H2O2 for 24 h increased the intracellular labile zinc level without cell toxicity. In contrast, 170 μM H2O2 for 12 h is reported to kill mouse astrocytes obtained from C57BL/6-strain mice (C57BL/6-astrocytes) with an increase in intracellular labile zinc. To clarify this discrepancy, we compared the intracellular zinc levels and cell toxicity in H2O2-treated ddY- and C57BL/6-astrocytes. Exposure of C57BL/6-astrocytes to 170 or 400 μM H2O2 for 12 h dose-dependently decreased the cell viability and administration of plasma membrane-permeable zinc chelator TPEN prevented the 170 μM H2O2-induced astrocyte death, while neither concentration of H2O2 killed ddY-astrocytes. The intracellular zinc level in H2O2-treated C57BL/6-astrocytes was higher than that in H2O2-treated ddY-astrocytes, and this increase was suppressed by TPEN. There was no apparent difference in the expression levels of zinc transporters ZIPs and ZnTs between the two types of astrocytes, while expression of zinc releasable channel TRPM7 was found on the plasma membrane in ddY-astrocytes, but not in C57BL/6-astrocytes, although the total cellular expression levels were almost the same. In addition, a TRPM7 blocker, 2-aminoethoxydiphenyl borate, increased the intracellular zinc level in H2O2-treated ddY-, but not C57BL/6-astrocytes. Collectively, it is suggested that vulnerability of astrocytes to oxidative stress depends on an increased level of intracellular labile zinc, and TRPM7 localized on the plasma membrane contributes, at least in part, to ameliorate the cell injury by decreasing the zinc level.

Effects of FGF2/FGFR1 Pathway on Expression of A1 Astrocytes After Infrasound Exposure.

Two types of reactive astrocytes, A1 and A2 astrocytes, are induced following neuroinflammation and ischemia. In this study, we evaluated the effects of the fibroblast growth factor (FGF)2/FGF receptor (FGFR)1 pathway on A1 and A2 astrocytes in the rat hippocampus using double-labeling immunofluorescence following infrasound exposure. A1 astrocytes were induced in the CA1 region of the hippocampus after exposure to infrasound for 3 days. The number of microglial cells was also increased, and we investigated if these might be responsible for the reactivity of A1 astrocytes. Accordingly, expression levels of C3 and Iba-1, as markers of A1 astrocytes and microglial cells, respectively, were both up-regulated in rat hippocampus following infrasound exposure, as demonstrated by western blot. We also explored the effect of the FGF2/FGFR1 pathway on A1 astrocyte reactivity by pretreating rats with FGF2 or the specific FGFR1 antagonist, PD173074. A1 astrocytes were gradually down-regulated by activation of the FGF2/FGFR1 pathway and were up-regulated by inhibition of the FGF2/FGFR1 pathway after infrasound damage. These results further our understanding of the role of reactive astrocytes in infrasound-induced central nervous system injury and will thus facilitate the development of new treatments for these injuries.

The involvement of astrocytes in early-life adversity induced programming of the brain.

Early‐life adversity (ELA) in the form of stress, inflammation, or malnutrition, can increase the risk of developing psychopathology or cognitive problems in adulthood. The neurobiological substrates underlying this process remain unclear. While neuronal dysfunction and microglial contribution have been studied in this context, only recently the role of astrocytes in early‐life programming of the brain has been appreciated. Astrocytes serve many basic roles for brain functioning (e.g., synaptogenesis, glutamate recycling), and are unique in their capacity of sensing and integrating environmental signals, as they are the first cells to encounter signals from the blood, including hormonal changes (e.g., glucocorticoids), immune signals, and nutritional information. Integration of these signals is especially important during early development, and therefore we propose that astrocytes contribute to ELA induced changes in the brain by sensing and integrating environmental signals and by modulating neuronal development and function. Studies in rodents have already shown that ELA can impact astrocytes on the short and long term, however, a critical review of these results is currently lacking. Here, we will discuss the developmental trajectory of astrocytes, their ability to integrate stress, immune, and nutritional signals from the early environment, and we will review how different types of early adversity impact astrocytes.

The developmental expression of metabotropic glutamate receptor 4 in prenatal human frontal lobe and neurogenesis regions

BackgroundsMetabotropic glutamate receptors, besides ionotropic receptors, mediate the complicated effect of glutamate on neurogenesis. Previous studies showed that metabotropic glutamate receptor 4 (mGluR4) regulated the proliferation and differentiation of neural stem/progenitor cells in vitro. However, little is known about the expression pattern of mGluR4 on prenatal central nervous system in vivo, especially the human being. MethodsThe normal brain tissues of human fetus were collected and divided into 4 groups according to the gestational age: 9–11 W, 14–16 W, 22–24 W and 32–36 W. Then the expression of mGluR4 was evaluated at mRNA and protein levels by means of PCR or immunohistochemistry method, respectively. The type of cell expressing mGluR4 was further investigated using double-labeling immunofluorescence. ResultsRT-PCR showed that the mRNA of mGluR4 could be detected in frontal lobe from 9 W to 32 W and real-time PCR quantificationally demonstrated the mRNA increased with development. Similarly, immnoreactivity was found in all layers of frontal lobe, VZ/SVZ. The intensity scores analysis showed that the staining became stronger and the range extended gradually with development. The double-labeling immunofluorescence showed that mGluR4 was present in neural stem/progenitor cells (nestin-positive cells after 9 W), young neurons (DCX-positive cells after 9 W), mature neurons (NeuN-positive cells in cortex after 32 W), as well as typical astrocytes (GFAP-positive cells in medulla after 32 W). ConclusionThese results supply an important evidence that mGluR4 is expressed in prenatal human cerebrum, and main kinds of cells related to neurogenesis are involved in its expression.

Structural Organization of Astrocytes in the Subgranular Zone of the Rabbit Hippocampal Dentate Fascia

Neurogenesis in the subgranular zone (SGZ) of the mammalian hippocampus is well known to occur throughout the life span. Astrocytes in this specialized proliferative zone are supposed to have properties of progenitor cells. Structural features of these cells and their interspecies differences remain understudied, while data on the structural organization of the SGZ in the rabbit (order Lagomorpha, superorder Glires), which is widely used in medical and biological studies, are lacking at all. The present work was focused on the structural and cytochemical organization of astrocytes in the SGZ of the rabbit hippocampal dentate fascia as studied by laser confocal microscopy. The study was carried out on the brain of adult Chinchilla rabbits compared to that of adult Wistar rats. Two morphological astrocyte types were identified in the rabbit SGZ: radial gliocyte-like (type I) and atypical fibrous astrocyte-like (type II) cells. By contrast, the rat SGZ exhibited a predominance of type II astrocytes which lacked long unramified processes penetrating through the granular layer and reaching the molecular layer. SGZ astrocytes, both in the rabbit and rat, were characterized by intense immunoreactivity for glutamine synthetase, most pronounced in the processes that formed the perivascular glia limitans. Importantly, the peculiarities of the astrocyte organization in the dentate fascia of the rabbit hippocampus allowed SGZ delimitation, whereas astrocytes in the rat SGZ exhibited no local morphological distinctions. The latter finding indicates a more complex organization of the neurogenic zone in the hippocampus of lagomorphs in contrast to the same zone in rodents.

AN INVESTIGATION ON THE ANTICANCER EFFECT OF SPIDER WEB IN HUMAN CERVICAL CELL LINE

Aims: The aim of this study is to investigate the anti-cancer and anti-proliferative effect of spider web extract, and mitochondrial apoptosis signaling response via gene expression levels belonging to caspase-3 depended apoptosis in both healthy Astrocyte and cancerous HeLa cell lines. Methods: We used HeLa and C8-D1A Astrocyte type I clone cell lines as the human cervical cancer and healthy cell line, respectively. We treated the cells with spider web extract and performed MTT assay. IC50 was calculated by probit analysis. Molecular fluorescence staining and TALI cytometer measurements were also applied. The response of the mitochondrial apoptosis pathway to spider web extract treatment was analyzed by the qRT-PCR assay. Results: The spider web extract administered in different concentrations to the HeLa cell line reduced cell viability at a statistically significant level after 24 hours of application. In the astrocyte cell line, the spider web extract did not cause statistically significant cell death. In the analysis of gene expressions, a strong mitochondrial apoptosis signaling was observed. Conclusion: While spider web extract does not cause any cytotoxic effects on healthy cell lines, it causes a strong fatal effect in cancer cell line. In addition, IC50 dose of the spider web extract is satisfying compared to many other natural products in the market which have anti-cancer effects. Spider web extract causes a programmed cell death by following death signaling pathways.

Reactive Astrocytes in Neurodegenerative Diseases.

Astrocytes, the largest and most numerous glial cells in the central nervous system (CNS), play a variety of important roles in regulating homeostasis, increasing synaptic plasticity and providing neuroprotection, thus helping to maintain normal brain function. At the same time, astrocytes can participate in the inflammatory response and play a key role in the progression of neurodegenerative diseases. Reactive astrocytes are strongly induced by numerous pathological conditions in the CNS. Astrocyte reactivity is initially characterized by hypertrophy of soma and processes, triggered by different molecules. Recent studies have demonstrated that neuroinflammation and ischemia can elicit two different types of reactive astrocytes, termed A1s and A2s. However, in the case of astrocyte reactivity in different neurodegenerative diseases, the recently published research issues remain a high level of conflict and controversy. So far, we still know very little about whether and how the function or reactivity of astrocytes changes in the progression of different neurodegenerative diseases. In this review, we aimed to briefly discuss recent studies highlighting the complex contribution of astrocytes in the process of various neurodegenerative diseases, which may provide us with new prospects for the development of an excellent therapeutic target for neurodegenerative diseases.

Neuroglia in the autistic brain: evidence from a preclinical model

BackgroundNeuroglial cells that provide homeostatic support and form defence of the nervous system contribute to all neurological disorders. We analyzed three major types of neuroglia, astrocytes, oligodendrocytes, and microglia in the brains of an animal model of autism spectrum disorder, in which rats were exposed prenatally to antiepileptic and mood stabilizer drug valproic acid; this model being of acknowledged clinical relevance.MethodsWe tested the autistic-like behaviors of valproic acid-prenatally exposed male rats by performing isolation-induced ultrasonic vocalizations, the three-chamber test, and the hole board test. To account for human infancy, adolescence, and adulthood, such tasks were performed at postnatal day 13, postnatal day 35, and postnatal day 90, respectively. After sacrifice, we examined gene and protein expression of specific markers of neuroglia in hippocampus, prefrontal cortex, and cerebellum, these brain regions being associated with autism spectrum disorder pathogenesis.ResultsInfant offspring of VPA-exposed dams emitted less ultrasonic vocalizations when isolated from their mothers and siblings and, in adolescence and adulthood, they showed altered sociability in the three chamber test and increased stereotypic behavior in the hole board test. Molecular analyses indicate that prenatal valproic acid exposure affects all types of neuroglia, mainly causing transcriptional modifications. The most prominent changes occur in prefrontal cortex and in the hippocampus of autistic-like animals; these changes are particularly evident during infancy and adolescence, while they appear to be mitigated in adulthood.ConclusionsNeuroglial pathological phenotype in autism spectrum disorder rat model appears to be rather mild with little signs of widespread and chronic neuroinflammation.

Multiple origins and modularity in the spatiotemporal emergence of cerebellar astrocyte heterogeneity

The morphological, molecular, and functional heterogeneity of astrocytes is under intense scrutiny, but how this diversity is ontogenetically achieved remains largely unknown. Here, by quantitative in vivo clonal analyses and proliferation studies, we demonstrate that the major cerebellar astrocyte types emerge according to an unprecedented and remarkably orderly developmental program comprising (i) a time-dependent decline in both clone size and progenitor multipotency, associated with clone allocation first to the hemispheres and then to the vermis(ii) distinctive clonal relationships among astrocyte types, revealing diverse lineage potentials of embryonic and postnatal progenitors; and (iii) stereotyped clone architectures and recurrent modularities that correlate to layer-specific dynamics of postnatal proliferation/differentiation. In silico simulations indicate that the sole presence of a unique multipotent progenitor at the source of the whole astrogliogenic program is unlikely and rather suggest the involvement of additional committed components.

Fast Generation of Functional Subtype Astrocytes from Human Pluripotent Stem Cells.

SummaryDifferentiation of astrocytes from human pluripotent stem cells (hPSCs) is a tedious and variable process. This hampers the study of hPSC-generated astrocytes in disease processes and drug development. By using CRISPR/Cas9-mediated inducible expression of NFIA or NFIA plus SOX9 in hPSCs, we developed a method to efficiently generate astrocytes in 4–7 weeks. The astrocytic identity of the induced cells was verified by their characteristic molecular and functional properties as well as after transplantation. Furthermore, we developed a strategy to generate region-specific astrocyte subtypes by combining differentiation of regional progenitors and transgenic induction of astrocytes. This simple and efficient method offers a new opportunity to study the fundamental biology of human astrocytes and their roles in disease processes.

Effects of High Intensity Local Exposure of a 10 Ghz-Electromagnetic Field on Glial Activity in Rat Brain

The possibility of radio-frequency electromagnetic fields (RF-EMF) of mobile phones to cause any adverse health effects on the brain is a subject of numerous studies and publications. Our previous studies have shown that no changes in microcirculatory parameters such as blood-brain barrier and leukocyte behaviors in pial microcirculation were found in the rat brain locally exposed to 1439 MHz EMF even at 2.0 W/kg of brain averaged specific absorption rate (BASAR). On the contrary, several recent studies reported that glial cells activated, indicating inflammation level, after the exposure to RF-EMF under non-thermal exposure conditions. However, the intensity level of RF-EMF exposure, which can occur the activation of glial cells, is still arguable. Therefore, it was necessary to define the intensity of local brain exposure to RF-EMF which affects the activation of glial cells. The aim of the present study was to investigate a threshold of the local exposure intensity of RF-EMF for the glial cells activation. Male Sprague-Dawley rats (8-9 weeks old) were used in this experiment. The rats were anesthetized with isoflurane (inhalation). The head of each animal was fixed in the stereotaxic apparatus and locally exposed to 10 GHz RF-EMF for 18 min using a monopole antenna. The field intensity was adjusted to make 0 to 2207 W/kg of averaged SAR in target tissue area. The two types of glial cells, microglia and astrocyte were observed 24 hours after the exposure using immunohistochemistry. As results, obvious morphological difference between sham-exposed and exposed animals were found in microglial cells. The RF-EMF exposure changed their morphology of ramified phase into those of ameboid phase under the high intensity exposure conditions. In contrast, there was no difference in astrocyte between two exposed groups even the same intensity level. We are now investigating the threshold intensity of RF-EMF for the microglial activity and expect to show it in the meeting.

Glutamine Synthetase in Rat Brain Cells

Objective. To use an immunohistochemical method to study glutamine synthetase (GS)-synthesizing brain cells. Materials and methods. Enzyme was detected on frontal rat brain sections (n = 10) using mouse monoclonal antibodies. Specimens were analyzed by light and confocal laser microscopy. Results. GS was found to be expressed in all areas of the brain, mainly by two types of cells, with different structures and topographies. The main type of cell with immunopositive reactions to glial fibrillary acidic protein were identical to astrocytes. The other structural and locational type of cell differed from typical astrocytes. Conclusions. The data obtained here provide evidence that GS is not a selective marker for any particular population of rat brain cells.

Glia and central cardiorespiratory pathology.

Respiration and blood pressure are primarily controlled by somatic and autonomic motor neurones, respectively. Central cardiorespiratory control is critical in moment-to-moment survival, but it also has a role in the development and maintenance of chronic pathological conditions such as hypertension. The glial cells of the brain are non-neuronal cells with metabolic, immune, and developmental functions. Recent evidence shows that glia play an active role in supporting and regulating the neuronal circuitry which drives the cardiorespiratory system. Here we will review the activities of two key types of glial cell, microglia and astrocytes, in assisting normal central cardiorespiratory control and in pathology.