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H Nawa

Publications and source records attributed to H Nawa.

At least 55 records · Page 3Linked to original sources
PubMed1999

Regulation of nerve growth factor release by nitric oxide through cyclic GMP pathway in cortical glial cells.

In the present study, we found that S-nitroso-N-acetyl-DL-penicillamine, a spontaneous nitric oxide (NO) generator, dose-dependently inhibited basal nerve growth factor (NGF) release from mixed glial cells. To elucidate the function of endogenous NO in the regulation of NGF release, the mixed glial cells were stimulated with lipopolysaccharide (LPS) or LPS plus interferon-gamma (IFNgamma). The results showed that LPS alone induced NGF release and moderate NO production. However, costimulation with LPS plus IFNgamma greatly enhanced NO production but significantly suppressed LPS-induced NGF release. When N(G)-monomethyl-L-arginine, an NOS inhibitor, was added to the culture, the suppression of NGF release by IFNgamma was significantly reduced. Quantitative reverse transcription-polymerase chain reaction demonstrated S-nitroso-N-acetyl-DL-penicillamine was also able to inhibit the LPS-induced NGF mRNA expression. To understand the different contributions of astroglia and microglia to this phenomenon, both cell types were purified. We found purified astroglia produced high amounts of NGF but low amounts of NO. However, purified microglia produced a large amount of NO but very low amounts of NGF after stimulation with LPS or LPS plus IFNgamma. Our data also indicated the second messenger cyclic GMP, but not cyclic AMP, was able to inhibit basal NGF release. In vivo experiments confirmed that NGF protein level was significantly enhanced in rats treated with L-N(omega)-nitro-arginine methyl ester and in endothelial NO synthase mutant mice. Taken together, we conclude NO derived mainly from microglia down-regulates NGF release from astroglia at the transcriptional level by stimulating cyclic GMP pathway.

Animals↗
PubMed1998

Turnover rates of the AMPA-type glutamate receptor GluR1 measured by transient gene expression.

Protein turnover rates have until now been measured by pulse chasing of the target protein after labeling it with radioactive amino acids. This procedure, however, requires severe amino acid depletion followed by specific immunoprecipitation of the target protein. In the present study, we assessed the turnover rates of an AMPA-type glutamate receptor, GluR1 (or GluRA), with the conventional method and a novel one using gene transfer, and compared both of them. GluR1 cDNA was introduced into PC12 cells and cultured rat hippocampal neurons by electroporation and lipofection, respectively. Expression of its mRNA was transient and had almost ceased 2 days in PC12 cells after transfection, while the receptor protein continued to be detectable by Western blotting for a week. When the levels of the receptor protein in PC12 cells were plotted on a semi-logarithmic scale, the decay curve appeared linear after 2 days: Its decay half time (tau 1/2) was calculated as 41 h. In contrast, the pulse chase experiment revealed that the decay half time was 2-4 h in PC12 cells although cell damage was seen during this procedure. The receptor decay speed was also measured in cultured hippocampal neurons using GluR1 cDNA attached to a tag sequence. Decay of the receptor protein was monitored by Western blotting probed by an anti-tag antibody: tau 1/2 was 52 h in hippocampal neurons, similar to that in PC12. These observations suggest that the transfection procedure is more sensitive and beneficial than the conventional pulse chasing method when measuring protein turnover rates in fragile neural cells.

Animals↗
PubMed1998

Brain derived neurotrophic factor is increased in cerebrospinal fluid of children suffering from asphyxia.

Brain derived neurotrophic factor (BDNF) is a neurotrophic factor that is relatively highly expressed in developing and adult brain. Whereas clinical determinations of nerve growth factor (NGF) in human serum and cerebrospinal fluid (CSF) in different conditions have been undertaken there are no reports on levels of BDNF in human CSF. Here we show that BDNF is increased in CSF of neonatal children suffering from asphyxia which is characterised by periods of brain hypoxic-ischemia. In contrast to BDNF, levels of CSF NGF were largely decreased in these children. The present results show that BDNF can be detected in human CSF and that the levels increase following hypoxic-ischemic brain injury. As suggested by animal studies the increased BDNF might counteract neuronal damage observed in these patients following asphyxia.

Apgar Score↗
PubMed1998

Dynamic changes of brain-derived neurotrophic factor protein levels in the rat forebrain after single and recurring kindling-induced seizures.

Regional levels of brain-derived neurotrophic factor protein were measured in the rat brain using enzyme immunoassay following seizures evoked by hippocampal kindling stimulations. One stimulation, which induced a brief, single episode of epileptiform activity in hippocampus and piriform cortex but not in parietal cortex or striatum, gave rise to a transient increase of brain-derived neurotrophic factor levels in dentate gyrus and CA3 region and a decrease in piriform cortex. After 40 rapidly recurring seizures, with epileptiform activity also involving parietal cortex and striatum, increases were observed in dentate gyrus, CA3 and CA1 regions, piriform cortex and striatum. Maximum levels were reached at 2-24 h and brain-derived neurotrophic factor then returned to baseline except in dentate gyrus, where elevated protein content was sustained for four days. The differential regulation of brain-derived neurotrophic factor protein levels in various forebrain structures, which only partly correlates to messenger RNA changes, could indicate regional differences in protein release, antero- or retrograde transport, or brain-derived neurotrophic factor promotor activation. The dynamic changes of brain-derived neurotrophic factor levels in regions involved in the generation and spread of seizure activity may regulate excitability and trigger plastic responses in the post-seizure period.

Animals↗
PubMed1998

Emerging roles of Dlg-like PDZ proteins in the organization of the NMDA-type glutamatergic synapse.

A group of proteins found at cell-cell junctions have a common structural domain, called PDZ-a stretch of 80-90 amino acid residues initially identified in the three proteins PSD-95, Dlg, and ZO-1. This domain is found in various proteins from bacteria to mammals and is involved in protein-protein interaction. Recently, many proteins containing this domain were identified in the nervous system by molecular cloning and shown to interact with other synaptic proteins, including various transmitter receptors, ion channels, and signal transducers. These PDZ-containing proteins are mostly located near the synaptic membrane and are, therefore, speculated to transport associated proteins to the synapse and/or anchor them at the synaptic sites. Alternatively, as a single molecule often contains multiple PDZ domains that can interact with each other, it may cluster all these synaptic molecules and facilitate their signaling at synaptic sites. This review focuses on the best characterized PDZ-containing proteins that interact with N-methyl-D-aspartate (NMDA)-type glutamate receptors and discusses their functions in synaptic organization.

Amino Acid Sequence↗
PubMed1998

Roles of neurotrophins on synaptic development and functions in the central nervous system.

Evidence is emerging to suggest that in addition to their "classical" neurotrophic involvement in the regulation of the differentiation, maturation and survival of neurons, neurotrophins play crucial roles in neural transmission and succeeding activity-dependent plasticity of synapses. Here we discuss: 1) the regulated synthesis and secretion of neurotrophins in response to neural activity, 2) the short- and long-term effects of neurotrophins on neural transmission, and 3) the neurotrophin-induced rearrangement of synaptic networks.

Brain↗
PubMed1997

Neurotrophic factors in brain synaptic plasticity.

Various intercellular signals influence the strength and mode of synaptic neurotransmission and contribute to synaptic plasticity. Such signals include neurotransmitters, gas molecules, and protein factors. In response to certain neural stimuli, these molecules are liberated from presynaptic and postsynaptic neurons, glial cells, and immune cells and synergistically alter synaptic neurotransmission over the long or short term. The short-term actions often involve presynaptic activities leading to long-term potentiation. However, it is now known that various protein factors including growth factors, cytokines, and neurotrophic factors can produce not only such short-term effects but also long-term synaptic modification of presynaptic and postsynaptic neurons by altering the production of neurotransmitters and the expression of their receptors or synaptic organization. The present review focuses on these intercellular protein factors and discusses the way in which they regulate synaptic plasticity.

Animals↗
PubMed1996

Regional specificity of alterations in NGF, BDNF and NT-3 levels in Alzheimer's disease.

Using two-site enzyme immunoassays (EIAs), we measured the levels of neurotrophins, nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF) and neurotrophin-3 (NT-3) simultaneously in three brain regions (motor cortex, dentate gyrus and entorhinal cortex) of patients with Alzheimer's disease (AD) and control individuals. Significant differences between the neurotrophin levels of these two groups were found in the different brain regions depending on the neurotrophin. The NGF level in the dentate gyrus of AD patients was higher, whereas the BDNF level in the entorhinal cortex and the NT-3 level in the motor cortex were lower than the corresponding control levels. These results indicate that protein levels of individual neurotrophins in different brain regions are affected differently by AD, and such differential changes may contribute to the complex pathology of AD.

Aged↗
PubMed1996

Regional brain-derived neurotrophic factor mRNA and protein levels following transient forebrain ischemia in the rat.

Levels of BDNF mRNA and protein were measured in the rat brain using in situ hybridization and a two-site enzyme immunoassay. Under basal conditions, the highest BDNF concentration was found in the dentate gyrus (88 ng/g), while the levels in CA3 (50 ng/g), CA1 (18 ng/g) and parietal cortex (8 ng/g) were markedly lower. Following 10 min of forebrain ischemia, BDNF protein increased transiently in the dentate gyrus (to 124% of control at 6 h after the insult) and CA3 region (to 131% of control, at 1 week after the insult). In CA1 and parietal cortex, BDNF protein decreased to 73-75% of control at 24 h. In contrast, BDNF mRNA expression in dentate granule cells and CA3 pyramidal layer was transiently elevated to 287 and 293% of control, respectively, at 2 h, whereas no change was detected in CA1 or neocortex. The regional BDNF protein levels shown here correlate at least partly with regional differences in cellular resistance to ischemic damage, which is consistent with the hypothesis of a neuroprotective role of BDNF.

Animals↗
PubMed1996

Differential regulation of hippocampal neurotrophins during aging in rats.

Neurotrophins are a family of neurotrophic factors with considerable structural homology. We used sensitive and specific two-site enzyme immunoassays to assess age-associated changes in levels of three neurotrophins++-+-nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), and neurotrophin-3 (NT-3)--in the hippocampus of Fischer 344 rats. Expressions of these proteins and their mRNAs were compared in the same animals. More than 200 ng of BDNF per gram of tissue was detected in the hippocampus of 2-month-old rats. This amount was two and 100 times greater than that of NT-3 and NGF, respectively. The levels of BDNF and NT-3 increased further 2-6 months after birth, whereas NGF content declined during this period, and the altered protein levels of all three neurotrophins were maintained 6-18 months postnatally. In contrast to the patterns of protein expression, BDNF mRNA levels increased during both of these periods, and the NT-3 mRNA levels appeared to decline. Changes in the expression of BDNF mRNA and NGF protein were opposite to those reported to occur in Alzheimer's disease. These results suggest that, during normal aging in rats, neurotrophin expression is regulated independently at both the mRNA and posttranslational levels. Any deficiency in their regulation might contribute to neurodegenerative disorders.

Aging↗
PubMed1995

Protective effects of brain-derived neurotrophic factor on the development of hippocampal kindling in the rat.

Recent data have suggested the involvement of neurotrophins in the cascade of events occurring during seizure development. In particular, expression of both brain-derived neurotrophic factor (BDNF) and its receptor mRNAs increases in different brain structures after convulsive seizures. The physiological significance of this increase was investigated by chronic intrahippocampal perfusion of BDNF in the model of dorsal hippocampal kindling in the rat. A 7 day perfusion of BDNF, in the region of the stimulating electrode, blocked the development of kindling during the perfusion period and for the following 15 days. These results provide in vivo evidence for a protective role of BDNF in the regulation of plasticity involved in epileptogenesis in adult brain.

Animals↗
PubMed1995

BDNF protein measured by a novel enzyme immunoassay in normal brain and after seizure: partial disagreement with mRNA levels.

Messenger RNA for brain-derived neurotrophic factor (BDNF) is distributed in many brain regions and regulated by excitatory neuronal activity. Despite numerous studies of BDNF mRNA, the distribution and regulation of BDNF protein are poorly understood because of the difficulty of its quantitative measurement. We have established a two-site enzyme immunoassay that detects trace amounts of BDNF protein (> 1 pg/assay) but not other neurotrophins or growth factors. The highest levels of BDNF in adult rat brain were found in the hippocampus, followed by the hypothalamus, neocortex, cerebellum, thalamus and striatum. This pattern is similar, but not identical, to the distribution of BDNF mRNA. A similar disparity between BDNF protein and mRNA levels was observed in their changes after hilus lesion-induced limbic seizures. In limbic structures, BDNF concentrations remained elevated 4 days after seizure onset, whereas BDNF mRNA has been reported previously to return to basal levels within 46 h. The temporal and spatial differences between the dynamics of protein and mRNA levels suggest the importance of post-translational and/or subcellular processes for BDNF production. The persistence of the increases in BDNF content was also reflected in its biological activity, e.g. peptidergic differentiation activity. After limbic seizures, neuropeptide Y content was most markedly and persistently elevated in the entorhinal/amygdaloid region, where the most sustained up-regulation of BDNF protein was observed. These results suggest that the sustained increase of BDNF protein in these limbic structures is involved in prolonged post-seizure phenomena, including peptidergic alterations.

Animals↗
PubMed1995

[Effects of antiseptics against methicillin-resistant Staphylococcus aureus].

Various antiseptics, commonly used in hospital, were tested against methicillin-resistant Staphylococcus aureus (MRSA) at high concentrations (approximately 10(9) CFU/ml) and in short time exposures. The antiseptic solutions of 0.05% alkyldiaminoethylglycine hydrochloride, 0.05% benzalkonium chloride, 0.2% povidone-iodine gargle and 0.03% dominophen bromide produced 1,000 to 1/100,000 reduction after a 30 sec exposure. 7.5 % povidone-iodine scrub and 0.2% benzalkonium chloride in 83% ethanol were most effective, reducing MRSA under detection limits. (less than 10 CFU/ml) 0.05% chlorhexidine gluconate was less effective, producing no evident reduction even after 1 min of exposure. Though 0.2% povidone solution reduced MRSA under detection limits at 37, 24 hrs incubation, colonies of several strains were detected after 48 hrs extended incubation. This suggests the existence of strains resistant to the antiseptic solution of povidone-iodine. We recommend that the disinfection for these strains should be repeated short time disinfection, because repeated short time exposure (15 sec 2 times) of antiseptics was more effective than one long time exposure (30 sec once).

Anti-Infective Agents, Local↗
PubMed1994

Regulation of neuropeptides in adult rat forebrain by the neurotrophins BDNF and NGF.

The expression of neuropeptides and neurotrophic factors is altered in the hippocampus after seizure induction in rats. Because the increase in brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF) mRNAs precede changes in neuropeptide expression after seizure, it is possible that BDNF and NGF mediate subsequent alterations in peptide expression. To test this hypothesis directly, BDNF or NGF was infused into the hippocampus and cortex of adult rats. To ascertain the regional specificity of any observed effects of neurotrophin administration on neuropeptide expression, infusions into the striatum were also studied. To control for specificity, vehicle was also infused into the same sites. Peptide and mRNA alterations were assessed by Northern analysis, immunohistochemistry and radioimmunoassay. BDNF produced elevations of peptide and mRNA for neuropeptide Y and cholecystokinin in hippocampus and cortex, and somatostatin in cortex. BDNF increased mRNAs for neuropeptide Y, cholecystokinin, substance P and dynorphin in striatum. In contrast, BDNF decreased dynorphin peptide and mRNA in hippocampus. NGF's effects were limited to small mRNA increases, without corresponding changes in peptide levels, for neuropeptide Y in hippocampus and striatum, substance P in cortex and cholecystokinin in striatum. The distinct and limited effects of NGF infusion on neuropeptide expression demonstrate that BDNF's effects are not non-specific results of protein infusion into the brain. These findings indicate that BDNF may play a regionally specific role in modulating neuropeptide expression in the normal brain as well as in various pathophysiological states.

Animals↗
PubMed1994

Brain-derived neurotrophic factor promotes differentiation of striatal GABAergic neurons.

The influence of neurotrophins on GABAergic properties of developing striatal neurons was investigated both in vivo and in vitro. Brain-derived neurotrophic factor (BDNF) specifically elevated cellular GABA content in striatal culture without altering neuronal survival. Neurotrophin-5 produced a similar effect on GABA, but nerve growth factor and neurotrophin-3 had no effect. An increase in GABA content in the striatum was also observed following BDNF injections into the cerebroventricle of neonatal rats. The increase of GABA levels in culture mainly resulted from an increase in holoenzyme activity of the GABA synthetic enzyme glutamic acid decarboxylase (GAD) and elevation of GABA uptake activity. In BDNF-treated striatal cultures, the newly differentiated neurons extended elaborate neurites and exhibited strong GAD immunoreactivity. These alterations were presumably caused by the upregulation of mRNA encoding GAD67 and the neuronal GABA transporter GAT-1. BDNF treatment also promoted other phenotypic differentiation of striatal neurons: BDNF increased the frequency of parvalbumin-immunoreactive neurons and calbindin-immunoreactive neurons and neuropeptide content for neuropeptide Y and somatostatin. These observations suggest that neurotrophins may contribute to phenotypic differentiation of GABAergic neurons in the developing striatum.

Animals↗
PubMed1994

Selective up-regulation of an NMDA receptor subunit mRNA in cultured cerebellar granule cells by K(+)-induced depolarization and NMDA treatment.

High KCI or NMDA treatment promotes the survival of cultured neonatal cerebellar granule cells, and these cells become sensitive to NMDA toxicity after prolonged K+ depolarization. Following both treatments, the NMDA receptor increases, as assessed by fura-2 fluorescence analysis of NMDA receptor-mediated intracellular Ca2+ increase. Northern analysis indicates that both treatments specifically up-regulate NMDAR2A subunit mRNA through an increase in resting intracellular Ca2+ concentration. Antisense oligonucleotide analysis further indicates that NMDAR2A mRNA up-regulation is responsible for NMDA receptor induction. Our results demonstrate that regulation of a specific NMDA receptor subunit mRNA governs NMDA receptor induction, which is thought to play an important role in granule cell survival and death.

Animals↗