Biomedical subjects

K Ishige

Publications and source records attributed to K Ishige.

At least 19 recordsLinked to original sources

PubMed2001

The activation of dopamine D4 receptors inhibits oxidative stress-induced nerve cell death.

Oxidative stress is thought to be the cause of nerve cell death in many CNS pathologies, including ischemia, trauma, and neurodegenerative disease. Glutamate kills nerve cells that lack ionotropic glutamate receptors via the inhibition of the cystine-glutamate antiporter x(c)(-), resulting in the inhibition of cystine uptake, the loss of glutathione, and the initiation of an oxidative stress cell death pathway. A number of catecholamines were found to block this pathway. Specifically, dopamine and related ligands inhibit glutamate-induced cell death in both clonal nerve cell lines and rat cortical neurons. The protective effects of dopamine, apomorphine, and apocodeine, but not epinephrine and norepinephrine, are antagonized by dopamine D4 antagonists. A dopamine D4 agonist also protects, and this protective effect is inhibited by U101958, a dopamine D4 antagonist. Although the protective effects of some of the catecholamines are correlated with their antioxidant activities, there is no correlation between the protective and antioxidant activities of several other ligands. Normally, glutamate causes an increase in reactive oxygen species (ROS) and intracellular Ca(2+). Apomorphine partially inhibits glutamate-induced ROS production and blocks the opening of cGMP-operated Ca(2+) channels that lead to Ca(2+) elevation in the late part of the cell death pathway. These data suggest that the protective effects of apomorphine on oxidative stress-induced cell death are, at least in part, mediated by dopamine D4 receptors via the regulation of cGMP-operated Ca(2+) channels.

Animals↗

PubMed2001

Polyphosphate:AMP phosphotransferase and polyphosphate:ADP phosphotransferase activities of Pseudomonas aeruginosa.

In Pseudomonas aeruginosa PAO1, we have found massive polyphosphate:AMP phosphotransferase activity and polyphosphate:ADP phosphotransferase activity known as the reverse catalytic activity of polyphosphate kinase which participates in polyphosphate synthesis in the bacterium. Biochemical analysis using the partially purified polyphosphate:ADP phosphotransferase has revealed that it is independent of polyphosphate kinase and can function as polyphosphate-dependent nucleoside diphosphate kinase which most prefers GDP to the other three nucleoside diphosphates as a phospho-acceptor. It has been also demonstrated that polyphosphate:AMP phosphotransferase activity marked in the bacterium mainly originates from the combined action of the polyphosphate:ADP phosphotransferase described above and adenylate kinase. Both of the polyphosphate-utilizing activities require short polyP as a phospho-donor whose chain length is <75.

Base Sequence↗

PubMed2001

Flavonoids protect neuronal cells from oxidative stress by three distinct mechanisms.

Flavonoids are a family of antioxidants found in fruits and vegetables as well as in popular beverages such as red wine and tea. Although the physiological benefits of flavonoids have been largely attributed to their antioxidant properties in plasma, flavonoids may also protect cells from various insults. Nerve cell death from oxidative stress has been implicated in a variety of pathologies, including stroke, trauma, and diseases such as Alzheimer's and Parkinson's. To determine the potential protective mechanisms of flavonoids in cell death, the mouse hippocampal cell line HT-22, a model system for oxidative stress, was used. In this system, exogenous glutamate inhibits cystine uptake and depletes intracellular glutathione (GSH), leading to the accumulation of reactive oxygen species (ROS) and an increase in Ca(2+) influx, which ultimately causes neuronal death. Many, but not all, flavonoids protect HT-22 cells and rat primary neurons from glutamate toxicity as well as from five other oxidative injuries. Three structural requirements of flavonoids for protection from glutamate are the hydroxylated C3, an unsaturated C ring, and hydrophobicity. We also found three distinct mechanisms of protection. These include increasing intracellular GSH, directly lowering levels of ROS, and preventing the influx of Ca(2+) despite high levels of ROS. These data show that the mechanism of protection from oxidative insults by flavonoids is highly specific for each compound.

Animals↗

PubMed2001

Repeated administration of CGP 46381, a gamma-aminobutyric acidB antagonist, and ethosuximide suppresses seizure-associated cyclic adenosine 3'5' monophosphate response element- and activator protein-1 DNA-binding activities in lethargic (lh/lh) mice.

To characterize seizure-associated increases in cerebral cortical and thalamic cyclic AMP responsive element (CRE)- and activator protein 1 (AP-1) DNA-binding activities in lethargic (lh/lh) mice, a genetic model of absence seizures, we examined the effects of ethosuximide and CGP 46381 on these DNA-binding activities. Repeated administration (twice a day for 5 days) of ethosuximide (200 mg/kg) or CGP 46381 (60 mg/kg) attenuated both seizure behavior and the increased DNA-binding activities, and was more effective than a single administration of these drugs. These treatments did not affect either normal behavior or basal DNA-binding activities in non-epileptic control (+/+) mice. Gel supershift assays revealed that the increased CRE-binding activity was attributable to activation of the binding activity of CREB, and that the c-Fos-c-Jun complex was a component of the increased AP-1 DNA-binding activity.

Animals↗

PubMed2001

Novel method for enzymatic synthesis of CMP-NeuAc.

A novel method for synthesizing CMP-NeuAc was established. We first confirmed that the putative neuA gene of Haemophilus influenzae, identified by its whole genome sequence project, indeed encodes CMP-NeuAc synthetase (EC 2.7.7.43). The enzyme requires CTP as a cytidylyl donor for cytidylylation of NeuAc. The enzyme was coupled with an enzymatic CTP-generating system from CMP and inorganic polyphosphate as a sole phospho-donor driven by the combination of polyphosphate kinase and CMP kinase, where phosphorylation of CMP is done by the combined activity expressed by both enzymes, and subsequent phosphorylation of CDP by polyphosphate kinase itself occurred efficiently. When CMP-NeuAc synthetase of H. influenzae, polyphosphate kinase, and CMP kinase were added to the reaction mixture containing equimolar concentrations (15 mM) of CMP and NeuAc, and polyphosphate (150 mM in terms of phosphate), CMP-NeuAc was synthesized up to 10 mM in 67% yield.

Cytidine Monophosphate↗

PubMed2000

Inorganic polyphosphate kinase and adenylate kinase participate in the polyphosphate:AMP phosphotransferase activity of Escherichia coli.

Polyphosphate kinase (PPK), responsible for the processive synthesis of inorganic polyphosphate (polyP) from ATP in Escherichia coli, can transfer in reverse the terminal phosphate residue of polyP to ADP to yield ATP. PolyP also serves as a donor in a polyP:AMP phosphotransferase (PAP) activity observed in extracts of Acinetobacter johnsonii and Myxococcus xanthus. We have found that overexpression of the gene encoding PPK results in a large enhancement of PAP activity in E. coli. The PAP activity requires both PPK and adenylate kinase in equimolar amounts. PPK and adenylate kinase form a complex in the presence of polyphosphate. We discuss a phosphotransfer mechanism that involves both enzymes and enables polyP to be a phospho-donor to AMP.

Adenylate Kinase↗

PubMed2000

Morphine augments excitatory synaptic transmission in the dentate gyrus through GABAergic disinhibition.

The present study investigated the effect of morphine on synaptic transmission and long-term potentiation (LTP) in the dentate gyrus using rat hippocampal slice preparations. Field excitatory postsynaptic potential (fEPSP) and population spike (PS), evoked by stimulation of the perforant path, were recorded from the dentate molecular layer and the stratum granulosum, respectively. Following application of 10 microM morphine, PS amplitude increased gradually in 10 min and was eventually potentiated by approximately 50%. The phenomenon showed a concentration-dependent manner and was completely canceled by naloxone, a mu opioid receptor antagonist. Furthermore, morphine-induced PS augmentation was not detected in disinhibited hippocampal slices, which suggests that the inhibitory input to the dentate granule cells was required for the facilitatory effect of morphine. Neither fEPSP nor tetanus-induced LTP of PS was altered by morphine application. The data support the hypothesis that mu opioid receptor activity modulates inhibitory recurrent circuits in the dentate gyrus and thereby, indirectly plays a regulatory role for hippocampal excitatory neurotransmission.

Animals↗

PubMed2000

An efficient method for production of uridine 5'-diphospho-N-acetylglucosamine.

Uridine 5'-diphospho-N-acetylglucosamine (UDP-GlcNAc) has been synthesized by a yeast-based method from 5'-UMP and glucosamine, in which yeast cells catalyze the conversion of 5'-UMP to 5'-UTP and provide enzymes involved in UDP-GlcNAc synthesis using 5'-UTP and glucosamine as substrates. However, this conventional method is not suitable for practical production of UDP-GlcNAc because of the low yield of the product. We found that the yqgR gene product of Bacillus subtilis, which has been identified as a glucokinase, can catalyze the phosphorylation of N-acetylglucosamine (GlcNAc) to give GlcNAc-6-phosphate, an intermediate of UDP-GlcNAc biosynthesis. The addition of the yqgR gene product to the yeast-based reaction system enabled us to synthesize UDP-GlcNAc using GlcNAc in place of glucosamine. The addition of two enzymes, GlcNAc-phosphate mutase and UDP-GlcNAc pyrophosphorylase, increased the yield of UDP-GlcNAc. Using this novel method, UDP-GlcNAc was produced at an amount of 78 mM from 100 mM 5'-UMP and 100 mM GlcNAc.

Amino Acid Sequence↗

PubMed2000

Inorganic polyphosphate and polyphosphate kinase: their novel biological functions and applications.

In this review, we discuss the following two subjects: 1) the physiological function of polyphosphate (poly(P)) as a regulatory factor for gene expression in Escherichia coli, and 2) novel functions of E. coli polyphosphate kinase (PPK) and their applications. With regard to the first subject, it has been shown that E. coli cells in which yeast exopolyphosphatase (poly(P)ase), PPX1, was overproduced reduced resistance to H2O2 and heat shock as did a mutant whose polyphosphate kinase gene is disrupted. Sensitivity to H2O2 and heat shock evinced by cells that overproduce PPX1 is attributed to depressed levels of rpoS expression. Since rpoS is a central element in a regulatory network that governs the expression of stationary-phase-induced genes, poly(P) affects the expression of many genes through controlling rpoS expression. Furthermore, poly(P) is also involved in expression of other stress-inducible genes that are not directly regulated by rpoS. The second subject includes the application of novel functions of PPK for nucleoside triphosphate (NTP) regeneration. Recently E. coli PPK has been found to catalyze the kination of not only ADP but also other nucleoside diphosphates using poly(P) as a phospho-donor, yielding NTPs. This nucleoside diphosphate kinase-like activity of PPK was confirmed to be available for NTP regeneration essential for enzymatic oligosaccharide synthesis using the sugar nucleotide cycling method. PPK has also been found to express a poly(P):AMP phosphotransferase activity by coupling with adenylate kinase (ADK) in E. coli. The ATP-regeneration system consisting of ADK, PPK, and poly(P) was shown to be promising for practical utilization of poly(P) as ATP substitute.

Adenosine Triphosphate↗

PubMed1999

Comparative study of survival signal withdrawal- and 4-hydroxynonenal-induced cell death in cerebellar granule cells.

The lipid peroxidation product, 4-hydroxynonenal (HNE), has been shown to induce apoptosis in PC12 cells and hippocampal neurons. We compared the degree of cell death induced by survival signal withdrawal (K+ and serum deprivation) with that induced by HNE, and investigated whether agents that block survival signal withdrawal-induced apoptosis could also prevent HNE-induced cell death in cultured cerebellar granule cells. Cell death induced by K+ and serum deprivation was inhibited by cycloheximide, a CPP 32-like protease inhibitor (Ac-DEVD-CHO) and a pituitary adenylate cyclase-activating polypeptide (PACAP)-38. In addition, nuclear cyclic AMP responsive element (CRE)- and activator protein 1 (AP-1) DNA-binding activities were increased 2 h after K+ and serum withdrawal, and these increases were inhibited by cycloheximide, Ac-DEVD-CHO and PACAP 38. Although these agents also blocked HNE-induced cell death, consistent with their efficacy in preventing survival signal withdrawal-induced cells death, CRE and AP-1 DNA-binding activities were decreased in a time-dependent manner during HNE-induced cell death. These results suggest that mechanistic differences exist between apoptosis induced by HNE and that induced by withdrawal of survival signals in cerebellar granule neurons.

Activating Transcription Factor 2↗

PubMed1999

The gene for an exopolyphosphatase of Pseudomonas aeruginosa.

In Pseudomonas aeriginosa, a gene, ppx, that encodes exopolyphosphatase [exopoly(P)ase; EC 3.6.1.11] of 506 amino acids (56,419 Da) was found downstream of the gene for polyphosphate kinase, ppk. Since ppx is located in the opposite direction of the ppk gene, they do not constitute an operon. The predicted amino acid sequence of PPX is 41% identical with Escherichia coli PPX. The gene product of ppx (paPPX) was overproduced in E. coli, and its activity was evaluated. Orthophosphate (Pi) is released from polyphosphate [poly(P)], the average chain lengths of which are 79 and 750, respectively. The amount of Pi released matched the amount of poly(P) lost. Thus ppx encodes an enzyme that has exopoly(P)ase activity.

Acid Anhydride Hydrolases↗

PubMed1999

Characterization of absence seizure-dependent cyclic AMP responsive element-and activator protein 1 DNA-binding activities in lethargic (lh/lh) mice.

The characterized nuclear cyclic AMP responsive element (CRE)- and activator protein 1 (AP-1) DNA-binding activities in various brain regions of lethargic (lh/lh) mice, a genetic model of absence seizures. Gel-shift assays showed that nuclear CRE- and AP-1 DNA-binding activities in the thalamus and cerebral cortex, but not in other regions such as the hippocampus and cerebellum of lethargic mice were significantly higher than those of non-epileptic control mice. Furthermore, CRE- and AP-1 DNA-binding activities in lethargic mice, but not control mice, were inhibited by the specific GABA(B) receptor antagonist CGP 46831, at a dose which suppressed seizure behavior and spike and wave discharges. These results suggest that enhanced nuclear CRE- and AP-1 DNA-binding activities in the thalamocortical region are related to generation and/or propagation of absence seizures in lethargic mice.

Animals↗

PubMed1999

Characterization of quinolone antibacterial-induced convulsions and increases in nuclear AP-1 DNA- and CRE-binding activities in mouse brain.

The quinolone antibacterials enoxacin and norfloxacin (2.5 mg/kg, i.v.) provoked clonic convulsions in mice treated concomitantly with biphenylacetic acid (BPAA, 100 mg/kg, i.p.), a major metabolite of the nonsteroidal anti-inflammatory drug fenbufen. Gel-shift assays showed that enoxacin-induced convulsions resulted in increases in nuclear activator protein 1 (AP-1) DNA- and cyclic AMP responsive element (CRE)-binding activities in the cerebral cortex and hippocampus, but not in other regions, such as the cerebellum and thalamus. In contrast, ofloxacin and levofloxacin, at the same doses, in the presence of BPAA did not evoke convulsions or increase these DNA-binding activities. Administration of these quinolones and BPAA alone elicited neither convulsions nor increases in these DNA-binding activities. These results suggest that the increased nuclear AP-1 DNA- and CRE-binding activities in the cerebral cortex and hippocampus induced by quinolones with BPAA correlated with seizure activities and that these brain regions play pivotal roles in quinolone-induced convulsions.

Animals↗

PubMed1999

[Cyclic AMP responsive element- and activator protein 1 DNA-binding activities in epilepsy model mice].

Convulsive seizures caused by many different stimuli have been shown to induce activator protein-1 (AP-1) transcription factors in the brain, particularly in the hippocampus. Previous results from our laboratory demonstrated that thalamic and cerebral cortical AP-1 DNA- and cyclic AMP responsive element (CRE)- binding activities in the absence seizure model mice were significantly higher than those in nonepileptic control mice. In order to characterize further a correlation between convulsive seizures and inducible transcription factors, we investigated convulsive seizure-dependent increases in AP-1 DNA- and CRE-binding activities in various brain regions of the mice. Administration of pentylentetrazole and kainic acid provoked clonic and limbic type seizures, respectively, and increased AP-1 DNA- and CRE- binding activities in the cerebral cortex and hippocampus but not in other regions. Maximal electric shock (MES) induced tonic convulsions and increased hippocampal and cerebral cortical AP-1 DNA- and CRE- binding activities. Sodium phenobarbital (50 mg/kg, i.p.), an anticonvulsant, suppressed both convulsions and increases in these DNA-binding activities induced by MES. In contrast, ethosuximide, an antiabsence drug, did not affect MES-induced convulsions or increases in these DNA-binding activities. These data suggest that convulsive seizures increase not only AP-1 DNA-binding but also CRE-binding activities in the cerebral cortex and hippocampus. These data combined with our previous results also suggest that regional differences in increases in CRE- and AP-1 DNA-binding activities between convulsive seizures and absence seizures are attributable to differences in the regions and pathways which are responsible for the genesis and spreading seizure activities in the central nervous system.

Animals↗

PubMed1998

The polyphosphate kinase gene of Pseudomonas aeruginosa.

We have cloned and sequenced a gene encoding polyphosphate kinase (PPK) from Pseudomonas aeruginosa PAO1. The gene immediately follows the hemB gene encoding porphobilinogen synthase responsible for heme synthesis. The predicted amino acid sequence of P. aeruginosa PPK is similar to those of PPKs previously characterized except that it possesses an extra stretch of 46 amino acids at its N-terminus, which has significant similarity to the Ras-related protein ARA5 of Arabidopsis thaliana. When P. aeruginosa PPK was overproduced in Escherichia coli, ATP-dependent polyphosphate-synthesizing activity was drastically enhanced, confirming that the protein is a PPK.

Amino Acid Sequence↗

PubMed1998

Pharmacological profiles of absence seizure-induced increases in CRE- and AP-1 DNA-binding activities in gamma-butyrolactone-treated mice.

Absence seizures are characterised by a well-defined disturbance of thalamocortical function, and there is no spread to other systems. In this study, we continue our examination of the mechanisms underlying the increased nuclear cyclic AMP responsive element (CRE)- and activator protein 1 (AP-1) DNA-binding activities in a gamma-butyrolactone (GBL)-induced mouse model of absence seizure. The administration of GBL increased CRE- and AP-1 DNA-binding activities in the cerebral cortex and thalamus, but not in other regions such as the hippocampus, cerebellum or pons + medulla oblongata, at doses which induced absence seizures. Not only the absence-seizure behavior but also the increased CRE- and AP-1 DNA-binding activities in the thalamocortical regions were reversibly inhibited by ethosuximide, a typical anti-absence drug, and the GABAB antagonists CGP 35348 and CGP 46381. A gel-supershift assay revealed that the GBL-induced CRE-binding activity was supershifted by an anti-CRE-binding protein (CREB) antibody, and that AP-1 DNA-binding activity was blocked by anti-c-Jun and anti-c-Fos antibodies. These results suggest that increased CRE- and AP-1 DNA-binding activities in the cerebral cortex and thalamus are related to the pathogenesis of generalized absence seizures and that these increases in DNA-binding activity are related to ethosuximide- and GABAB antagonist-sensitive abnormal neuronal activity in the thalamocortical circuit.

4-Butyrolactone↗

PubMed1997

Morphological and biochemical evidence of muscle hyperplasia following weight-lifting exercise in rats.

We used a rat model of weight lifting to examine the serial biochemical and morphological changes following muscle fiber hyperplasia during 14 days of exercise. [3H]thymidine and [14C]leucine labeling were used to determine the serial changes in cellular mitotic activity and the level of amino acid uptake and myosin synthesis. Morphological changes were assessed with light and transmission electron microscopy, whereas proliferation of cells was evaluated immunohistochemically with 5-bromo-2'-deoxyuridine (BrdU). The intensity of the exercise and degree of muscle damage were monitored by serum creatine kinase (CK) activity. Damaged fibers were sparsely distributed, and a significant CK leakage was observed 30-60 min after exercise. Anti-BrdU-positive cells were observed in damaged fibers and at the periphery of undamaged fibers. Changes typical of muscle regeneration were observed; however, the formation of new fibers in the interstitial space was also evident. The mitotic activity also changed and reflected the appearance of anti-BrdU-positive cells and activated satellite cells. Amino acid uptake increased during the first week of exercise, probably reflecting muscle hypertrophy and synthesis of other noncontractile related proteins. The uptake also increased during the second week, probably due to hyperplasia, a finding also supported by electron microscopy. Our results suggest that one bout of weight-lifting exercise in untrained rats induced muscle hyperplasia following regeneration. The process of muscle hyperplasia was activated by muscle fiber damage in our model.

Animals↗

PubMed1996

gamma-Butyrolactone-induced absence-like seizures increase nuclear CRE- and AP-1 DNA-binding activities in mouse brain.

We examined the involvement of the GABAB receptor and the coordinated induction of nuclear transcriptional factors in experimental generalized absence seizures induced by gamma-butyrolactone (GBL) in mice. Although administration of GBL 50 mg/kg did not show any effects on behavior or ECoG pattern, higher doses of GBL (70 and 100 mg/kg, i.p.) induced behavioral changes associated with 3-6-Hz spike and wave discharges in the mice. CGP 35348, a GABAB receptor antagonist, suppressed both the GBL-induced absence seizures and the spike and wave discharges. The antiepileptic effects of CGP 35348 (200 mg/kg, i.p.) were stronger than those of ethosuximide (200 mg/kg, i.p.). Sodium valproate (100 mg/kg, i.p.) attenuated the early phase but not the late phase of the GBL-induced absence seizures. Gel-mobility assay demonstrated that administration of an effective dose of GBL for eliciting spike and wave discharges dose-dependently increased nuclear cyclic AMP-responsive element (CRE)- and activator protein 1 (AP-1) DNA-binding activities in mouse whole brain. The increases in nuclear CRE- and AP-1 DNA-binding were antagonized by CGP 35348 in a dose-dependent fashion. In addition, GABAB receptor binding assay revealed that GBL or antiepileptic drugs did not displace [3H]baclofen binding in cerebral cortical membranes. In contrast, gamma-hydroxybutyrate (GHB), an active metabolite of GBL, inhibited [3H]baclofen binding in a concentration-dependent manner. These results suggest that GABAB receptor-mediated synaptic responses are involved in GBL-induced generalized absence seizures and that the increases in nuclear CRE- and AP-1 DNA-binding activities are correlated with the GBL-induced generalized absence seizures.

4-Butyrolactone↗