Microglia: activation and their significance in the central nervous system

Microglia are resident monocyte-lineaged cells in the brain. Their characteristic feature is that they react to injury and diseases of the brain and become morphologically and functionally activated. Although some trigger molecules which activate microglia are predicted to be released from injured or affected cells, such molecules have not yet been identified. The main role of activated microglia is believed to be in brain defense, as scavengers of dead cells, and as immune or immunoeffector cells. Recent biochemical and neurobiological studies have further indicated that they significantly affect the pathological state and/or regulate the regenerative state and remodeling of the brain by producing a variety of biologically active molecules including cytotoxic and neurotrophic molecules.

Microglia and the early phase of immune surveillance in the axotomized facial motor nucleus: impaired microglial activation and lymphocyte recruitment but no effect on neuronal survival or axonal regeneration in macrophage-colony stimulating factor-deficient mice

Activation of microglia is among the first cellular changes in the injured CNS. However, little is known about their specific contribution to secondary damage or repair processes in neighboring neurons and nonneuronal cells or to the immune surveillance of the damaged tissue. Animal models with defective microglial response such as osteopetrosis provide an approach to explore these effects. Osteopetrosis (op) is an autosomal recessive mutation with a complete deficiency of the macrophage-colony stimulating factor (MCSF; CSF-1), an important mitogen for brain microglia. In the current study we examined the effects of this MCSF deficiency on the microglial reaction and the overall cellular response to nerve injury in the mouse axotomized facial motor nucleus. In the brain, MCSF receptor immunoreactivity was found only on microglia and was strongly up-regulated following injury. MCSF deficiency led to a failure of microglia to show a normal increase in early activation markers (thrombospondin, MCSF receptor, alpha M beta 2- and alpha 5 beta 1-integrins), to spread on the surface of axotomized motoneurons, and to proliferate after injury. Early recruitment of CD3(+) T-lymphocytes to the facial nucleus 24 hours after injury was reduced by 60%. In contrast, the neuronal and astrocyte response was not affected. There was a normal increase in the neuropeptides calcitonin gene-related peptide and galanin, neuronal c-JUN, and NADPH-diaphorase and a decrease in choline acetyltransferase and acetylcholinesterase. Astrocyte glial fibrillary acidic protein immunoreactivity also showed a normal increase. There was a normal influx of macrophages and granulocytes into the injured facial nerve. Synaptic stripping, neuronal survival, and speed of axonal regeneration were also not affected. The current results show a strong, selective effect of MCSF on the early activation of microglia and, indirectly, on lymphocyte recruitment. This early phase of microglial activation appears not to be involved in the process of repair following peripheral nerve injury. However, it is important in the initiation of inflammatory changes in the brain and in the interaction with the immune system.

Ability of rat microglia to uptake extracellular glutamate

Since it has been suggested that microglia in vivo act as glutamate scavengers, this possibility was investigated in primary cultured microglia. The microglia showed specific abilities to uptake (14)C-glutamate depending on incubation time and numbers of cells used. The activity was suppressed by a specific inhibitor for a glial cell-type transporter, glutamate transporter-1 (GLT-1) (EAAT2). However, that of cultured astrocytes was not affected. These results suggest that microglia uptake glutamate by means of GLT-1. Supporting these results, immunoblotting revealed the presence of GLT-1 in the microglia, while only glutamate-aspartate transporter (GLAST) (EAAT1: another glial cell-type transporter) was detected in the astrocytes. All together, these results indicate that microglia can act as glutamate scavengers in vivo by expressing the glutamate transporter GLT-1.

Co-induction of argininosuccinate synthetase, cationic amino acid transporter-2, and nitric oxide synthase in activated murine microglial cells

Nitric oxide (NO) produced by activated microglia has been implicated in many pathophysiological events in the brain including neurodegenerative diseases. Cellular NO production depends absolutely on the availability of arginine, a substrate of NO synthase (NOS). Murine microglial MG5 cells were treated with bacterial lipopolysaccharide (LPS) and interferon-gamma (IFN-gamma), and expression of inducible NO synthase (iNOS) and arginine-supplying enzymes was investigated by RNA blot analysis. iNOS mRNA was strongly induced after treatment and reached a maximum at 6-12 h. mRNA for argininosuccinate synthetase (AS), a citrulline-arginine recycling enzyme, increased at 6 h and reached a maximum at 12 h. Immunoblot analysis showed that iNOS and AS proteins were also induced. In addition, mRNA encoding the cationic amino acid transporter-2 (CAT-2) was strongly induced shortly after treatment. Induction of mRNAs for iNOS, AS, and CAT-2 by LPS/IFN-gamma was also observed following stimulation of rat primary microglial cells. These results strongly suggest that both arginine transport by CAT-2 and citrulline-arginine recycling are important for high-output production of NO in activated microglial cells.

Brainstem activates paroxysmal discharge in human generalized epilepsy

In nine patients with generalized epilepsy of convulsive seizures, the excitability change of the brainstem was evaluated over the course of the interictal paroxysmal discharge (poly spike-and-wave complex, poly SWC). The evaluation was carried out by a sequential analysis of brainstem auditory evoked potentials (BAEPs) before and during one sequence of poly SWC. The characteristics of BAEPs, i.e. far-field evoked potentials, allowed the evaluation of the excitability change in the brainstem, which was not influenced by the cortical activity. The excitability in the ventral brainstem, measured with the parameters of wave-III, showed a biphasic fluctuation (deceleration--acceleration) before the onset of poly SWC (minima at -0.7+/-0.4 s). On the other hand, the excitability in the dorsal brainstem, measured with the parameters of wave-V, showed no significant difference over the course of poly SWC. The results suggest that the biphasic excitability change in the ventral brainstem is conveyed to the cortex through the ascending activating system. The excitability acceleration preceded by deceleration in the ventral brainstem probably synchronizes the cortical activity profoundly enough to produce poly SWC through the activation of intralaminar thalamic neurons.

Effects of bright light exposure on heart rate variability during sleep in young women

To investigate the effects of evening bright light on the autonomic nervous system, heart rate variability (HRV) during sleep was analyzed in dim light (DL) and bright light (BL) conditions. We recorded polysomnography in nine healthy young women aged 20-21 years. Time series of % delta power was calculated in the 0.49-2.20 Hz band. Heart rate variability was analyzed from a 10-min segment of slow wave sleep. The low- to high-frequency ratio and the low-frequency component decreased significantly in the BL conditions compared with the DL conditions. However, the power of the high-frequency component did not change in the two conditions. These results indicate that evening BL affects the autonomic nervous system during slow wave sleep.

Intact microglia are cultured and non-invasively harvested without pathological activation using a novel cultured cell recovery method

Because spontaneous host regeneration of damaged tissues is limited, novel therapeutics utilizing cultured cells with the aid of tissue engineering methods are promising alternatives for tissue replacement. One critical shortcoming is current requirement for invasive cell harvest from culture to fabricate cell-based devices. Although microglia that secrete neurotrophic factors are attractive candidates for novel cell transplantation therapy for damaged central nervous system tissue, the intact harvest of cultured microglia is presently not achievable. Therefore, primary microglia were plated onto culture surfaces grafted with the temperature-responsive polymer, poly(N-isopropylacrylamide) (PIPAAm). This surface undergoes rapid, reversible temperature-dependent changes in its hydration state and surface hydrophilicity. Microglia attached and proliferated on PIPAAm-grafted dishes at 37 degrees C. By reducing culture temperature, more than 90% of the cells spontaneously detached from the dishes within several minutes without trypsin or EDTA treatment. Recovered and replated microglia exhibited phenotypic properties comparable to those of primary microglia freshly isolated from brain. By contrast, less than 60% of the cells were harvested by trypsin digestion, and exhibited significant alteration of characteristic cellular properties as monitored by pathological states in vivo. This new technology exhibits utility for the preparation of cell sources required for cell transplantation as well as microglial function analysis.

Extracellular ATP or ADP induce chemotaxis of cultured microglia through Gi/o-coupled P2Y receptors

The initial microglial responses that occur after brain injury and in various neurological diseases are characterized by microglial accumulation in the affected sites of brain that results from the migration and proliferation of these cells. The early-phase signal responsible for this accumulation is likely to be transduced by rapidly diffusible factors. In this study, the possibility of ATP released from injured neurons and nerve terminals affecting cell motility was determined in rat primary cultured microglia. Extracellular ATP and ADP induced membrane ruffling and markedly enhanced chemokinesis in Boyden chamber assay. Further analyses using the Dunn chemotaxis chamber assay, which allows direct observation of cell movement, revealed that both ATP and ADP induced chemotaxis of microglia. The elimination of extracellular calcium or treatment with pyridoxalphosphate-6-azophenyl-2',4'-disulphonic acid, suramin, or adenosine-3'-phosphate-5'-phosphosulfate did not inhibit ATP- or ADP-induced membrane ruffling, whereas AR-C69931MX or pertussis toxin treatments clearly did so. As an intracellular signaling molecule underlying these phenomena, the small G-protein Rac was activated by ATP and ADP stimulation, and its activation was also inhibited by pretreatment with pertussis toxin. These results strongly suggest that membrane ruffling and chemotaxis of microglia induced by ATP or ADP are mediated by G(i/o)-coupled P2Y receptors.

Upregulated expression of Iba1 molecules in the central nervous system of mice in response to neurovirulent influenza A virus infection

The present study deals with the expression of Iba1 molecules, a novel EF-hand Ca2+-binding protein, in the brain after stereotaxic introduction of the neurovirulent WSN strain of influenza A virus into the olfactory bulb of C57BL/6 mice. The virus selectively targeted the paraventricular and anterior olfactory nuclei. Infected neurons appeared as early as at day 3 post infection and degenerated and vanished by day 12. The Iba1 molecule was normally expressed in resting microglia. The overexpression of the Iba1 in microglial cells was detected at day 3 post infection, culminating at day 7 with a morphological activation. Iba1-immunopositive macrophages outnumbered microglia in the paraventricular and anterior olfactory nuclei, where the infected neurons had degenerated. Macrophages totally disappeared by day 12, and the Iba1-expression in microglia was reduced to a normal level by day 35. Lack of perforin predisposed the mice to long-term virus infection of the brain, leading to the prolonged Iba1-overexpression. These results show that the Iba1 is upregulated in the mouse brain in response to influenza virus infection and may play significant roles in the regulation of some immunological and pathophysiological functions of microglia during virus infection.

Early immunohistochemical detection of axonal damage and glial activation in extremely immature brains with periventricular leukomalacia

Extremely low birth weight (ELBW) infants, who died at 12 hours to 7 days after birth, with periventricular leukomalacia (PVL), were examined by means of neuropathological and immunohistochemical methods. Fourteen infants without PVL were used as controls. Anti-beta-amyloid precursor protein (APP), glial fibrillary acidic protein (GFAP), and ionized calcium-binding adaptor molecule 1 (Iba1) antibodies were used as markers for axonal damage, reactive astrocytes and activated microglia, respectively. Thirteen of 14 ELBW infants with PVL showed a widespread distribution of leukomalacia and 10 showed postnatal-onset of leukomalacia. In 12 of the 14 infants with PVL, regions of APP-reactive axons were found multifocally in the cerebral white matter, but 8 of them did not show coagulation necrosis on HE staining. GFAP-positive cells and Iba1-positive cells were markedly found in the white matter of all cases with PVL and slightly in all 14 controls. These results indicated that in ELBW infants, the distribution and formation of PVL foci are widespread and characteristic and so may involve motor and intellectual abilities in ELBW infants. Therefore, the perinatal management to maintain an appropriate cerebral circulation and oxygenation may be very important.

Fibulin-1 binds the amino-terminal head of beta-amyloid precursor protein and modulates its physiological function

Genetic studies have implicated amyloid precursor protein (APP) in the pathogenesis of Alzheimer's disease. While accumulating lines of evidence indicate that APP has various functions in cells, little is known about the proteins that modulate its biological activity. Toward this end, we employed a two-hybrid system to identify potential interacting factors. We now report that fibulin-1, which contains repetitive Ca(2+)-binding EGF-like elements, binds to APP at its amino-terminal growth factor-like domain, the region that is responsible for its neurotrophic activities. Fibulin-1 expression in the brain is confined to neurons, and is not expressed significantly by astrocytes or microglia. Direct binding of fibulin-1 to the secreted form of APP (sAPP) was demonstrated with a pull-down assay using fragments of both fibulin-1 fused with glutathione-S transferase and sAPP, produced in bacteria and yeast, respectively. The fibulin-1/sAPP heteromer was shown to form in the conditioned medium of transfected COS-7 cells. Furthermore, fibulin-1 blocks sAPP-mediated proliferation of primary cultured rat neural stem cells. These results suggest that fibulin-1 may play a significant role in modulating the neurotrophic activities of APP.

Real-time, two-dimensional visualization of ischaemia-induced glutamate release from hippocampal slices

The involvement of excitatory amino acid (EAA) toxicity in ischaemia-induced neuronal cell death has long been suggested. However, in the hippocampus, the brain site most vulnerable to ischaemia, the detailed spatial and temporal patterns of EAA release are not yet known. To address this issue, we have developed a novel strategy for the continuous, real-time, two-dimensional monitoring of EAA release from brain slices. As EAA detector, we used a cell line transformed with the N-methyl-D-aspartate (NMDA) receptor, which is exclusively activated by EAAs, leading to an increase in the intracellular Ca(2+) level. Combined with a calcium imaging technique, the use of this cell line allowed the temporal and regional analysis of EAA release from a brain slice placed directly on top of the clonal cells in a culture dish. Using this strategy, we demonstrated ischaemia-induced EAA release in rat hippocampal slices. Increased EAA release was seen initially in the CA1 region, about 3 min after the beginning of ischaemia, then in the CA3 region and dentate gyrus, and, finally, throughout the hippocampal slice. Regional differences in extracellular EAA levels were also seen, with more EAA being released from the CA1 region than from the middle dentate gyrus. The present results are especially interesting as neurons in the CA1 region are more vulnerable to ischaemia than those in the CA3 region and dentate gyrus.

Ceramide-enhanced urokinase-type plasminogen activator (uPA) release is mediated by protein kinase C in cultured microglia

As described previously, a relatively high dose of neurotrophins increased the release of urokinase-type plasminogen activator (uPA) from cultured microglia. This biological response is suggested to be caused by ceramide, which is a metabolite of nerve growth factor low-affinity receptor (NGFRp75)-associated sphingomyelin turnover. Therefore, in the present study, we examined the effect of ceramide on the release of uPA from cultured microglia. Treatment of the cells with permeable C8-ceramide (D-erythro-Sphingosine, N-octanoyl-) enhanced uPA release in a dose-dependent manner. This effect of C8-ceramide was mimicked by treatment with bacterial sphingomyelinase. A pharmacological study using a specific PKC activator, phorbol-12-myristate-13-acetate, and a protein kinase C (PKC) inhibitor, bisindolylmaleimide, showed that PKC activation is required in order to release uPA from ceramide-stimulated microglia as well as from nonstimulated microglia. Further study using a specific conventional PKC (cPKC) activator, 1-oleoyl-2-acetyl-sn-glycerol (OAG), and a specific cPKC inhibitor, Gö 6976, suggested that PKC-delta and/or -epsilon is involved in uPA release. As opposed to the apoptotic pathway, however, no activation of c-Jun N-terminal kinase and nuclear factor kappa B was observed in C8-ceramide-stimulated microglia. The findings suggest that uPA release from microglia is regulated by a mechanism in which PKC-delta and/or -epsilon are activated and further signals are transduced subsequently.

Dual control of the brainstem on the spindle oscillation in humans

In human subjects, the excitability change of the brainstem was investigated over the course of the spindle oscillation. The investigation was carried out by a sequential analysis of brainstem auditory evoked potentials (BAEPs) with reference to one sequence of spindle oscillation. The method was based on the characteristics of BAEPs, i.e. far-field evoked potential. The brainstem revealed two types of excitability change: one in the lower ventral brainstem (wave-III components), and the other in the upper dorsal brainstem (wave-V components). The excitability in the dorsal brainstem showed an oscillation with one cycle period of about 1.5 s, whereas in the ventral brainstem, the excitability showed a long-range biphasic (decaying-growing) fluctuation. Both excitability changes in the brainstem preceded the spindle oscillation, and the phase was reversed during the emerging period of spindle oscillation. The results suggest a primary triggering mechanism of the brainstem for the spindle oscillation, which is independent of preceding cortical drives (K-complexes) upon the thalamus. The difference of the excitability change between the spindle oscillation and the paroxysmal discharge (spike-and-wave complex) was also discussed.

Hepatocyte growth factor-induced differential activation of phospholipase cgamma 1 and phosphatidylinositol 3-kinase is regulated by tyrosine phosphatase SHP-1 in astrocytes

Hepatocyte growth factor (HGF) elicits pleiotropic effects on various types of cells through the c-Met receptor tyrosine kinase. However, the mechanisms underlying the diverse responses of cells remain unknown. We show here that HGF promoted chemokinesis of rat primary astrocytes through the activation of phosphatidylinositol 3 (PI3)-kinase without any influence on mitogenesis of the cells. Under the same condition, phospholipase Cgamma1 (PLCgamma1), which is another signal mediator of c-Met, was not tyrosine-phosphorylated during HGF stimulation. However, treatment of the cells with orthovanadate, a tyrosine phosphatase inhibitor, restored the HGF-induced tyrosine phosphorylation of PLCgamma1. A tyrosine phosphatase, SHP-1, was associated with both PI3-kinase and PLCgamma1 before HGF stimulation, but it was dissociated only from PI3-kinase after the stimulation. Furthermore, transfectants of catalytically inactive mutant of SHP-1 showed tyrosine phosphorylation of PLCgamma1 and mitogenic responses to HGF, and the mitogenic response was blocked with, an inhibitor of phosphatidylinositol-specific PLC, and calphostin C, an inhibitor of protein kinase C downstream of the PLCgamma1. These results indicate that PLCgamma1 is selectively prevented from being a signal mediator by constitutive association of SHP-1, and that this selective inhibition of PLCgamma1 may determine the cellular response of astrocytes to HGF.

Extracellular ATP triggers tumor necrosis factor-alpha release from rat microglia

Brain microglia are a major source of inflammatory cytokines, such as tumor necrosis factor-alpha (TNF-alpha), which have been implicated in the progression of neurodegenerative diseases. Recently, microglia were revealed to be highly responsive to ATP, which is released from nerve terminals, activated immune cells, or damaged cells. It is not clear, however, whether released ATP can regulate TNF-alpha secretion from microglia. Here we demonstrate that ATP potently stimulates TNF-alpha release, resulting from TNF-alpha mRNA expression in rat cultured brain microglia. The TNF-alpha release was maximally elicited by 1 mM ATP and also induced by a P2X(7) receptor-selective agonist, 2'- and 3'-O-(4-benzoylbenzoyl)adenosine 5'-triphosphate, suggesting the involvement of P2X(7) receptor. ATP-induced TNF-alpha release was Ca(2+)-dependent, and a sustained Ca(2+) influx correlated with the TNF-alpha release in ATP-stimulated microglia. ATP-induced TNF-alpha release was inhibited by PD 098059, an inhibitor of extracellular signal-regulated protein kinase (ERK) kinase 1 (MEK1), which activates ERK, and also by SB 203580, an inhibitor of p38 mitogen-activated protein kinase. ATP rapidly activated both ERK and p38 even in the absence of extracellular Ca(2+). These results indicate that extracellular ATP triggers TNF-alpha release in rat microglia via a P2 receptor, likely to be the P2X(7) subtype, by a mechanism that is dependent on both the sustained Ca(2+) influx and ERK/p38 cascade, regulated independently of Ca(2+) influx.

Involvement of Iba1 in membrane ruffling and phagocytosis of macrophages/microglia

Ionized calcium binding adaptor molecule 1, Iba1, is an EF hand calcium binding protein whose expression is restricted to macrophages/microglia. In this study, Iba1 was shown to colocalize with F-actin in membrane ruffles induced by macrophage colony-stimulating factor and in phagocytic cups formed during zymosan phagocytosis. Expression of mutant Iba1 carrying either N- or C-terminal deletions or carrying a substitution in the calcium binding domain, suppressed the membrane ruffling and the phagocytosis. These results indicate that Iba1 is a key molecule in membrane ruffling and the phagocytosis of macrophages/microglia. Furthermore, Iba1 colocalized with a small GTPase Rac in the membrane ruffles and the phagocytic cups. The Iba1 mutants also suppressed membrane ruffling induced by dominant active Rac1V12, but do not affect microspikes by Cdc42V12 and stress fibers by RhoAV14. These observations suggest that Iba1 is involved in Rac and calcium signaling pathways.

Association of osteopontin with ischemic axonal death in periventricular leukomalacia

Osteopontin (OPN) is a bone matrix protein expressed my macrophages and related to the process of tissue calcification, and is also known to protect ischemic cells. To understand how OPN is involved in the process of ischemic axonal death in periventricular leukomalacia (PVL), we examined the immunoreactivity of OPN and ionized calcium binding adaptor molecule 1 (Iba1; microglia/macrophage marker) at various stages of PVL. OPN immunoreactivity paralleled the number of Iba1-positive foam cells; a finding which suggests the production of OPN protein by foam cells. OPN immunoreactivity was not found in either normal white matter or acute PVL lesions, but was detected at the subacute and chronic stages in swollen and calcified axons bordering the ischemic zone. These findings suggest that OPN is closely associated with death of swollen axons at the periphery of the ischemic zone, regulating the presence or absence of calcification.

Modification of glial-neuronal cell interactions prevents photoreceptor apoptosis during light-induced retinal degeneration

Prolonged or high-intensity exposure to visible light leads to photoreceptor cell death. In this study, we demonstrate a novel pathway of light-induced photoreceptor apoptosis involving the low-affinity neurotrophin receptor p75 (p75NTR). Retinal degeneration upregulated both p75NTR and the high-affinity neurotrophin receptor TrkC in different parts of Müller glial cells. Exogenous neurotrophin-3 (NT-3) increased, but nerve growth factor (NGF) decreased basic fibroblast growth factor (bFGF) production in Müller cells, which can directly rescue photoreceptor apoptosis. Blockade of p75NTR prevented bFGF reduction and resulted in both structural and functional photoreceptor survival in vivo. Furthermore, the absence of p75NTR significantly prevented light-induced photoreceptor apoptosis. These observations implicate glial cells in the determination of neural cell survival, and suggest functional glial-neuronal cell interactions as new therapeutic targets for neurodegeneration.

Glutamate transporter GLT-1 is highly expressed in activated microglia following facial nerve axotomy

Glutamate transporters play an important role in the re-uptake of glutamate after its release from glutamatergic synapses. So far five of such transporters subtypes have been cloned from rodent and human brains. The densities of glutamate transporters are recognised to be developmentally regulated, but the role of glutamate transporters in the mechanisms underlying the occurrence of neuronal traumatic injury has not been widely studied. In the present study quantitative Western blotting and immunohistochemical technique were employed to study the expression of GLT-1/EAAT2 in the facial nuclei of adult rats following unilateral facial nerve axotomy. The total content of GLT-1 protein decreased in the ipsilateral axotomised rat facial nucleus. However, activated microglia surrounding motoneurons showed high expression of GLT-1 after facial nerve axotomy. Parallel studies revealed that primary cultured microglial cells also showed GLT-1-immunoreactivity. To our knowledge, this is the first direct demonstration of the expression of GLT-1 protein in activated microglial cells, suggesting a neuroprotective role of microglia against glutamate excitotoxicity following nerve axotomy.

Plasminogen enhances the secretion of plasminogen activator inhibitor-1 from cultured rat astrocytes

To investigate the physiological significance of microglia-derived plasminogen (PGn) in the central nervous system, we determined the effects of rat PGn on the secretion of plasminogen activator inhibitor (PAI) in cultured rat astrocytes by reverse zymography and Western blotting. The cultured astrocytes normally produce only a limited amount of PAI-1. After stimulation with PGn, however, the amount of active PAI-1 in the astrocyte-conditioned medium was significantly increased in a time-dependent manner. PGn was also proved to activate p38 MAP kinase and c-Jun N-terminal kinase in these astrocytes. Taken together, these results suggest that microglia-derived PGn increases the secretion of PAI-1 in astrocytes through the activation of MAP kinases, and that enhanced PAI-1 regulates various physiological phenomena including tissue remodeling, neuronal plasticity and neurotoxicity.

Neuronal adhesion molecule telencephalin induces rapid cell spreading of microglia

Telencephalin (TLCN) is a neuronal surface glycoprotein whose expression is restricted to the telencephalon, the most rostral segment of the brain. TLCN binds to lymphocyte function-associated antigen-1 (LFA-1) integrin. In the central nervous system, LFA-1 is selectively and constitutively expressed by microglia, suggesting that TLCN/LFA-1 binding may mediate cell-cell interactions between telencephalic neurons and microglia. In the present study, we investigated the effects of recombinant TLCN protein on the morphology of microglia. TLCN induced an intensive spreading of lamellipodia, causing a rapid change in microglial morphology. In contrast, TLCN induced no significant change in morphology of neuroblastoma and fibroblasts. Furthermore, the TLCN-induced spreading of microglia was accompanied by a clustering of LFA-1 on cell surface membrane. These results provide evidence that TLCN binding to the surface of microglia transduces signals into microglia that mediate or accelerate cell spreading and LFA-1 redistribution, implying that neuronal TLCN may control the state and/or function of microglia in both physiological and pathological conditions.

Rat primary cultured microglia express glial cell line-derived neurotrophic factor receptors

The neurotrophic effect of glial cell line-derived neurotrophic factor (GDNF) has been well documented in both the central and peripheral nervous systems. From the histological findings, target cells of GDNF have been considered to be neurons. In the present study, the expression of GDNF receptors, ret and GFRalpha-1, was demonstrated in rat primary cultured microglia by reverse transcription-polymerase chain reaction and the protein-level expression of Ret was also confirmed by Western-blotting analyses. Moreover, GDNF stimulated the phosphorylation of MAP kinase (ERK1/2) in the cells. These results suggest that GDNF regulates not only neuronal survival and maturation but also certain functions of microglia in the brain.

Analysis of human error in nursing care

Analysis of reports about incidental and accidental events in nursing care were made using a reliability engineering method. Unnatural working hours, such as evening duty, night duty falling next to a holiday, two consecutive night-duty shifts, and two consecutive evening-duty shifts were major factors in the occurrence of errors. In a mixed-division ward (a ward containing patients belonging to different divisions), rule-based errors happened more frequently than in a single-division ward. Also, less experienced nursing staffs made errors more frequently than experienced nursing staffs.

Brainstem triggers absence seizures in human generalized epilepsy

Simultaneous analysis of brainstem auditory evoked potentials (BAEPs) with reference to electroencephalography (EEG) was designed to examine the brainstem function corresponding to the EEG event. With this method, we investigated the brainstem function pre- and during the paroxysmal discharge in human absence seizures classified as primary generalized epilepsy (PGE). Two types of functional change in the lower brainstem were revealed as parameters of wave-III components (amplitude and area) of BAEPs without significant change in the upper brainstem. One was long-range biphasic fluctuation (acceleration followed by abrupt deceleration with the maximum -6.4+/-3.2 s before the seizure onset), and the other was rhythmic oscillation with 3 Hz. The latter, synchronized with the cortical spike-and-wave complex, imposed on the descending slope of the former. One important point is that both preceded the onset of cortical paroxysmal discharge. The results reappraise the classical hypothesis of "centrencephalic system" on seizure generating mechanism in human PGE. The results prove the primary triggering role of the lower brainstem that is independent of sleep-related synchronizations. The method is applicable to other types of EEG event for the investigation of brainstem involvement.