Biomedical subjects

N Shibata

Publications and source records attributed to N Shibata.

At least 73 records · Page 4Linked to original sources

PubMed2000

A study of the relationship between the seizure focus and 1H-MRS in temporal lobe epilepsy and frontal lobe epilepsy.

Several studies of temporal lobe epilepsy (TLE) patients have investigated the relationship between the seizure focus and 1H magnetic resonance spectroscopy (1H-MRS). There have also been a few reports in other types of partial epilepsy. We examined the relationship between the seizure focus and the reduction in N-acetylaspartate: creatine (NAA : Cr) ratio using 1H-MRS in both TLE and frontal lobe epilepsy (FLE) patients. We studied 21 patients with unilateral TLE and seven patients with unilateral FLE. We used a 1.5 Tesla magnetic resonance unit (Signa Horizon; General Electric). Approximately 15 x 15 x 20 mm3 voxel of interest (VOI) was placed over the anterior portion of the bilateral hippocampus in the TLE patients, and the anterodorsal position of bilateral frontal lobe in the FLE patients. The seizure focus was identified by interictal scalp electro-encephalogram (EEG). In the TLE patients the NAA : Cr ratios were reduced in the seizure focus, while in the FLE patients they were not always reduced in the seizure focus. In the TLE patients the coincidence rate between the seizure focus and the reduction in the NAA:Cr ratio was 90% (19 of 21 patients), while in the FLE patients the coincidence rate was only 57% (four of seven patients).

Adult↗

PubMed2000

Ictal brain hemodynamics in the epileptic focus caused by a brain tumor using functional magnetic resonance imaging (fMRI).

Using functional magnetic resonance imaging (fMRI) we were able to observe, in detail, ictal brain hemodynamics during epileptic seizure caused by a brain tumor. A 53-year-old man was experencing partial motor seizures of the left side of his face and neck. In a brain MR image a mass lesion was found in the subcortical area of the right frontal lobe. We found focal spikes in his right hemisphere, though dominantly in C4 and T4 regions. fMRI investigations were carried out at 1.5 T (GE Signa Horizon) using gradient-echo echo-planar neuroimaging. We were able to perform the ictal examination twice. The activated regions were focalized and clearly found only on the lateral side of the tumor base. The region was in agreement with the epileptic focus examined using an electrocorticogram (ECOG). The signal intensity in the seizure focus rapidly increased 30 seconds before the convulsion was observed. After the end of the convulsion it also took 30 seconds to restore the signal intensity to the baseline value. fMRI is a very useful tool for various studies such as the identification of the epileptic focus, the mechanism of epileptic seizure, and so on.

Brain Mapping↗

PubMed2000

Superoxide dismutase-1 mutation-related neurotoxicity in familial amyotrophic lateral sclerosis.

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disorder characterized by motor neuron system involvement, and is epidemiologically subclassified into sporadic, familial and endemic forms. About 20% of ALS families are associated with mutations in the gene for superoxide dismutase-1 (SOD1) encoded on chromosome 21q22.1. Several studies have pointed to a variety of functions of mutant SOD1, which has enhanced catalytic activity of the peroxynitrite-mediated tyrosine nitration, readily releases the reactive Cu ions, induces apoptotic cell death, has enhanced peroxidase activity, damages the mitochondria to release Ca2+, and forms SOD1-containing aggregates in the cytoplasm. Many of these studies have obtained evidence for increased oxidative damage in ALS. On the other hand, some reports disagree with oxidative damage involvement in SOD1 mutant ALS. In considering the findings of increased oxidative damage in mutant SOD1-expressing transgenic mice, it should be remembered that overexpression of mutant SOD1 may enhance oxidative stress generation from this enzyme. In this review, we present the clinicopathological features of SOD1 mutant familial ALS and its transgenic mouse model, and also discuss SOD1 mutation-related neurotoxicity, including SOD1 protein aggregation and post-translational protein modification.

Amyotrophic Lateral Sclerosis↗

PubMed2000

New consensus research on neuropathological aspects of familial amyotrophic lateral sclerosis with superoxide dismutase 1 (SOD1) gene mutations: inclusions containing SOD1 in neurons and astrocytes.

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease that primarily involves the motor neuron system. Approximately 5-10% of ALS is familial. Superoxide dismutase 1 (SOD1) gene mutations are shown to be associated with about 20% of familial ALS (FALS) patients. The neuronal Lewy-body-like hyaline inclusion (LBHI) and astrocytic hyaline inclusion (Ast-HI) are morphological hallmarks of certain SOD1-linked FALS patients with SOD1 gene mutant and transgenic mice expressing human SOD1 with G85R mutation. From the detailed immunohistochemical analyses, the essential common protein of both inclusions is SOD1. Ultrastructurally, both inclusions consist of granule-coated fibrils 15-25 nm in diameter. Based on the immuno-electron microscopical finding that these abnormal granule-coated fibrils are positive for SOD1, the formation (or aggregation) of the abnormal fibrils containing SOD1 would be essential evidence in diseases caused by various SOD1 mutations. The granule-coated fibrils are also modified by advanced glycation end products (AGEs). The AGEs themselves are insoluble molecules with direct toxic effects on cells. AGE formation of SOD1 composing the granule-coated fibrils (probable AGE-modified mutant SOD1) may amplify their aggregation and produce a more marked toxicity.

Amyotrophic Lateral Sclerosis↗

PubMed2000

Factors that affect absorption behavior of cyclosporin a in gentamicin-induced acute renal failure in rats.

Factors that affect the absorption of cyclosporin A (CsA) were examined in gentamicin-induced acute renal failure (ARF) rats. In ARF rats, the area under the blood CsA concentration-time curve after oral administration was significantly decreased in comparison with that of control rats; 5.81 +/- 0.55 vs 11.30 +/- 1.59 mg h mL(-1)(mean+/-s.e.m.), respectively, and the relative bioavailabilities in ARF and control rats after oral administration were 15.2% and 43.4%, respectively. The flow rate of bile and the amount of bile acids in ARF rats were markedly decreased to about 61% of control, and 41% of control, respectively. The amount of CsA uptaken into the evened sac of jejunum, transferred to serosal side, and metabolized in tissues was significantly decreased in ARF rats without verapamil, while with 0.3 mM verapamil, the amount in ARF rats recovered to the levels of control rats. The absorption clearance of CsA in ARF rats was significantly decreased, however it was significantly improved by adding bile or bile acid. Adenosine triphosphate released from enterocytes in ARF rats was significantly decreased in the presence of 2.0 microM CsA, 0.3 mM verapamil, or both, in comparison with control rats. From these findings, we concluded that a reduction of CsA bioavailability during ARF is caused by depression in bile excretion and renal function-dependent depression of uptake from intestinal tract via maybe P-gLycoprotein in enterocytes. They are main two factors that reduce the absorbed fraction of CsA in ARF rats.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed2000

Roles of functional loops and the C-terminal segment of a single-stranded DNA binding protein elucidated by X-Ray structure analysis.

The single-stranded DNA (ssDNA) binding protein from Escherichia coli (EcoSSB) plays a central role in DNA replication, recombination and repair. The tertiary structure of EcoSSB was determined at 2.2 A resolution. This is rather higher resolution than previously reported. Crystals were grown from the homogeneous intact protein but the EcoSSB tetramer in the crystals contains truncated subunits lacking a part of the C-terminal. The structure determined includes biologically important flexible loops and C-terminal regions, and revealed the existence of concavities. These concavities include the residues important for ssDNA binding. An ssDNA can be fitted on the concavities and further stabilized through interactions with the loops forming flexible lids. It seems likely to play a central role in the binding of ssDNA.

Amino Acid Sequence↗

PubMed2000

The role of structural intersubunit microheterogeneity in the regulation of the activity in hysteresis of ribulose 1, 5-bisphosphate carboxylase/oxygenase.

Many enzymes are composed of subunits with the identical primary structure. It has been believed that the protein structure of these subunits is the same. Ribulose 1,5-bisphosphate carboxylase/oxygenase (RuBisCO) comprises eight large subunits with the identical amino acid sequence and eight small subunits. Rotation of the side chains of the lysine residues, Lys-21 and Lys-305, in each of the eight large subunits in spinach RuBisCO in two ways produces microheterogeneity among the subunits. These structures are stabilized through hydrogen bonds by water molecules incorporated into the large subunits. This may cause different effects upon catalysis and a hysteretic, time-dependent decrease in activity in spinach RuBisCO. Changing the amino acid residues corresponding to Lys-21 and Lys-305 in non-hysteretic Chromatium vinosum RuBisCO to lysine induces hysteresis and increases the catalytic activity from 8.8 to 15.8 per site per second. This rate is approximately five times higher than that of the higher-plant enzyme.

Catalysis↗

PubMed2000

How do the x-ray structure and the NMR structure of FMN-binding protein differ?

The crystal structure of FMN-binding protein (FMN-bp) from Desulfovibrio vulgaris Miyazaki F was solved by the multiple isomorphous replacement method and refined to an R factor of 15.1% at 1.3 A resolution. FMN-bp exists in a dimeric form in the crystal, in contrast to the monomeric structure determined by NMR. R.m.s. deviations between the crystal structure and the solution structure are more than 2 A, which implies significant differences. There are some hydrophobic residues in the interface between the two monomers. In particular, Leu122 in the C-terminus has a close contact with the o-xylene moiety of FMN, while solvent molecules may cover the o-xylene moiety in the solution structure.

Bacterial Proteins↗

PubMed2000

Valproic acid-induced hyperammonemic encephalopathy with triphasic waves.

PURPOSE: To examine a patient with valproic acid (VPA)-induced hyperammonemic encephalopathy accompanied by triphasic waves. METHODS: A 61-year-old male patient with epilepsy experienced disturbance of consciousness after VPA dose was increased because of poor seizure control. The electroencephalogram (EEG) taken on admission revealed triphasic waves and high-amplitude delta-activity with frontal predominance. Although serum hepatic enzymes, such as AST and ALT, were normal, serum ammonium level was high at 96 microg/dl (normal range, 3-47 microg/dl). Serum amino acid analysis showed multiple minor abnormalities. Administration of VPA was discontinued immediately after admission, while other anticonvulsants were continued. RESULTS: The patient's condition was improved on the fourth day of admission. An EEG, serum ammonium level, and amino acid profile were normal on the eighth day. Based on VPA administration, serum ammonium levels, and results of amino acid analysis, this patient had VPA-induced hyperammonemic encephalopathy. CONCLUSIONS: Our case indicates that caution is required if triphasic waves appear in VPA-induced hyperammonemic encephalopathy.

Amino Acids↗

PubMed2000

Regional differences in arrhythmogenic aftereffects of high intensity DC stimulation in the ventricles.

Regional differences of the aftereffects of high intensity DC stimulation were investigated in isolated rabbit hearts stained with a voltage-sensitive dye (di-4-ANEPPS). Optical action potential signals were recorded from the epicardial surface of the right and left ventricular free wall (RVep, LVep) and from the right endocardial surface of the interventricular septum (IVS). Ten-millisecond monophasic DC stimulation (S2, 20-120 V) was applied to the signal recording spots during the early plateau phase of the action potential induced by basic stimuli (S1, 2.5 Hz). There was a linear relationship between S2 voltage and the S2 field intensity (FI). S2 caused postshock additional depolarization, giving rise to a prolongation of the shocked action potential. With S2 > or = 40 V (FI > or = approximately 20 V/cm), terminal repolarization of action potential was inhibited, and subsequent postshock S1 action potentials for 1-5 minutes were characterized by a decrease in the maximum diastolic potential and a decrease in the amplitude and a slowing of their upstroke phase. The higher the S2 voltage, the larger the aftereffects. The changes in postshock action potential configuration in RVep were significantly greater than those observed in LVep and IVS when compared at the same levels of S2 intensity. In RVep, 12 of 20 shocks of 120 V resulted in a prolonged refractoriness to S1 (> 1 s), and the arrest was often followed by oscillation of membrane potential. Ventricular tachycardia or fibrillation ensued from the oscillation in five cases. No such long arrest or serious arrhythmias were elicited in LVep and IVS. These results suggest that RVep is more susceptible than LVep and IVS for arrhythmogenic aftereffects of high intensity DC stimulation.

Animals↗

PubMed2000

[A SHV-derived extended-spectrum beta-lactamase (SHV-12) produced by an Escherichia coli recovered from wound abscess in post operative case with rectal carcinoma].

A 62-year-old woman admitted for rectal carcinoma suffered from a post-operative bacterial infection. Oxy-imino-beta-lactams including cefotiam (CTM) and cefozopran (CZOP) were prescribed for this case, but the patient developed a wound abscess followed by peritonitis. She recovered from the bacterial infection after drainage and recurrent washing of the abscess. An ephemeral aggravation of infectious signs was observed just after creation of an artificial anus, and CZOP was again administered, and no evident bacterial infection occurred. The patient recovered, then was followed as an outpatient to date. A CAZ-resistant (MIC, > 16 micrograms/ml) E. coli was recovered from pus of her wound abscess. Since the CAZ-resistance decreased (MIC, 64 micrograms/ml-->0.13 microgram/ml) by the presence of clavulanate (CVA) in this isolate, this strain was speculated to be an extended spectrum beta-lactamase (ESBL) producer at an early stage of infection. A similar strain was also isolated from the feces. Therefore, we immediately took measures to block the nosocomial spread of this microorganism, and we succeeded in preventing a nosocomial outbreak of this strain. It was later confirmed by PCR analysis and DNA sequencing analysis that this CAZ-resistant E. coli strain produces an ESBL (SHV-5-2a = SHV-12). This is the first report of a case of infection with SHV-derived ESBL producing E. coli strain in Japan. We are concerned that further dissemination of this kind of microorganism might occur in the near future also in Japan, as it has been widely observed in European countries and the US. We believe that it will be very important to distinguish the type of beta-lactamases for rigorous bacterial infection control with the prudent use of antibiotics. In other words, we in Japan must recall that various gram-negative bacterial species that produce TEM-, SHV-derived ESBLs, Toho-1, AmpC, or IMP-1 are already widespread. Thus, we should take this fact into consideration when we do antibiotic susceptibility tentings and interpretation of the results for promotion of accurate chemotherapy.

Abscess↗

PubMed2000

A new SHV-derived extended-spectrum beta-lactamase (SHV-24) that hydrolyzes ceftazidime through a single-amino-acid substitution (D179G) in the -loop.

A new SHV-derived extended-spectrum beta-lactamase (SHV-24) conferring high-level resistance to ceftazidime but not cefotaxime and cefazolin was identified in Japan. This enzyme was encoded by a transferable 150-kb plasmid from an Escherichia coli clinical isolate. The pI and K(m) for CAZ of this enzyme were 7.5 and 30 microM, respectively. SHV-24 was found to have a D179G substitution in the Omega-loop of the enzyme.

Amino Acid Sequence↗

PubMed2000

Convenient test for screening metallo-beta-lactamase-producing gram-negative bacteria by using thiol compounds.

A simple disk diffusion test was constructed for detection of IMP-1-type metallo-beta-lactamase-producing gram-negative bacteria. Two Kirby-Bauer disks containing ceftazidime (CAZ) and a filter disk containing a metallo-beta-lactamase inhibitor were used in this test. Several IMP-1 inhibitors such as thiol compounds including 2-mercaptopropionic acid, heavy metal salts, and EDTA were evaluated for this test. Two CAZ disks were placed on a Mueller-Hinton agar plate on which a bacterial suspension was spread according to the method recommended by the National Committee for Clinical Laboratory Standards. The distance between the disks was kept to about 4 to 5 cm, and a filter disk containing a metallo-beta-lactamase inhibitor was placed near one of the CAZ disks within a center-to-center distance of 1.0 to 2.5 cm. For IMP-1-producing strains, the growth-inhibitory zone between the two disks expanded, while no evident change in the shape of the growth-inhibitory zone was observed for CAZ-resistant strains producing serine beta-lactamases such as AmpC or SHV-12. As a result, 2 to 3 microliter of undiluted 2-mercaptopropionic acid or mercaptoacetic acid able to block IMP-1 activity gave the most reproducible and clearest results, and CAZ-resistant strains producing AmpC or extended-spectrum beta-lactamases were distinguishable from IMP-1 producers by this test. A similar observation was made with IMP-1-producing clinical isolates such as Serratia marcescens, Klebsiella pneumoniae, Escherichia coli, Enterobacter cloacae, Enterobacter aerogenes, Citrobacter freundii, Proteus vulgaris, Pseudomonas aeruginosa, Pseudomonas putida, Acinetobacter spp., and Alcaligenes xylosoxidans. The specificity and sensitivity of this test were comparable to those of PCR analysis using bla(IMP)-specific primers. Therefore, this convenient test would be valuable for daily use in clinical laboratories.

Bacterial Proteins↗

PubMed2000

Retrospective diagnosis of diphtheria by detection of the Corynebacterium diphtheriae tox gene in a formaldehyde-fixed throat swab using PCR and sequencing analysis.

The tox gene of Corynebacterium diphtheriae was detected in a formaldehyde-fixed throat swab taken from a 68-year-old man who was reported to have died of suffocation due to a pharyngeal tumor. DNA templates prepared from bacterial cells fixed with 10% formaldehyde were subjected to a PCR analysis with tox gene-specific PCR primers. The resultant 112-nucleotide-long PCR product was sequenced using a dye terminator method, and an expected 57-nucleotide-long internal sequence of the tox gene was detected. This method is applicable for retrospective diagnosis in diphtheria cases in which only a formaldehyde-fixed clinical sample is available.

Base Sequence↗

PubMed2000

Increased migration in late G(1) phase in cultured smooth muscle cells.

Migration and proliferation of smooth muscle cells (SMC) contribute to neointimal formation after arterial injury. However, the relation between migration and proliferation in these cells is obscure. To discriminate between migration and proliferation, we employed a migration assay of SMC at different phases of the cell cycle. Serum-deprived SMC were synchronized in different phases of the cell cycle by addition of serum for various periods of time. Migration induced by platelet-derived growth factor B-chain homodimer was maximal in SMC that were predominantly in the late G(1) (G(1b)) phase. In addition, in nonsynchronized SMC, 65-75% of SMC that had migrated were in the G(1b) phase. Phosphorylated myosin light chain was enriched around the cell periphery in SMC in the G(1b) phase compared with SMC in the other cell cycle phases. Interestingly, the Triton X-100-insoluble fraction of myosin was remarkably decreased in G(1b)-enriched SMC. These findings suggest that migratory activity of SMC may be coupled with the G(1b) phase. The phosphorylation and retention of myosin might explain some of the properties responsible for increased migration.

Actins↗

PubMed2000

Colon delivery efficiencies of intestinal pressure-controlled colon delivery capsules prepared by a coating machine in human subjects.

Large quantities of pressure-controlled colon delivery capsules (PCDCs) were prepared by a Hicoater-mini pharmaceutical coating machine and colon delivery efficiencies were evaluated in man. Caffeine powder as a model drug was suspended with a polyethylene glycol (PEG) 1000 suppository base at 50 degrees C, and was hardened in no. 0- and no. 2-sized capsular shapes. The capsule-shaped suppositories were coated with 5% w/v ethanolic ethylcellulose (7G grade) solution using the coating machine. By increasing the coating weight of ethylcellulose from 28.6 +/- 1.1 mg to 45.3 +/- 0.2 mg, the mean coating thickness of no. 0 PCDCs increased from 56 +/- 1 microm to 64 +/- 1 microm. With no. 2 PCDCs, the mean coating thickness increased from 50 micro +/- 1 microm to 57 +/- 1 microm by increasing the coating weight of ethylcellulose from 8.1 +/- 0.5 mg to 11.2 +/- 0.3 mg. The no. 0 PCDCs, having a mean ethylcellulose coating membrane thicknesses of 56 +/- 1 microm (type 1) and 64 +/- 1 microm (type 2), as well as no. 2 PCDCs, having thicknesses of 50 +/- 1 microm (type 3) and 57 +/- 1 microm (type 4), were used for in-vivo evaluation in man. After oral administration of test preparations containing 75 mg of caffeine, saliva samples were obtained and salivary caffeine levels were measured by an HPLC method. The first appearance time, Ti, of caffeine in the saliva was used as a parameter for the estimation of the release time of caffeine from PCDCs in the gastrointestinal tract. The mean Ti values of no. 0 PCDCs were 3.3 +/- 0.3 h for type- 1 and 5.3 +/- 0.3 h for type-2 preparations while the mean Ti values of no. 2 PCDCs were 4.3 +/- 0.5 h for type 3 and 5.3 +/- 0.3 h for type 4. There were good correlations between ethylcellulose coating membrane thicknesses and in-vivo Ti values. A colon arrival time of 5 h was reported in our subjects by gastrointestinal magnetomarkergraphy. PCDCs having a mean coating thickness of 64 +/- 1 microm for no. 0 capsules and of 57 +/- 1 microm for no. 2 capsules were thought to deliver caffeine to the human colon efficiently.

Adult↗

PubMed2000

Pharmacokinetic interactions between HIV-1 protease inhibitors in rats: study on combinations of two kinds of HIV-1 protease inhibitors.

The drug interactions between four human immune deficiency virus (HIV-1) protease inhibitors have been characterized by in-vitro metabolic studies using rat liver microsomal fractions and in-vivo oral administration. In this study, a new HPLC analytical method developed by us was used for the simultaneous determination of saquinavir and nelfinavir in rat plasma and microsomes. The metabolic clearance rates (Vmax/Km) of saquinavir, nelfinavir, and indinavir were 170.9 +/- 10.9, 126.1 +/- 4-4, and 73.0 +/- 2.0 microL min(-1) (mg protein)(-1), respectively. Ritonavir was the strongest inhibitor with inhibition constants (Ki) of 1.64 microM for saquinavir, 0.95 microM for indinavir, and 1.01 microM for nelfinavir. Nelfinavir was the second strongest inhibitor with Ki's of 2.35 microM for saquinavir and 2.14 microM for indinavir. Indinavir was the third strongest inhibitor with Ki's of 2.76 microM for nelfinavir and 3.55 microM for saquinavir. Saquinavir was the weakest inhibitor for the other three HIV- 1 protease inhibitors. After oral co-administration in combination with another HIV-1 protease inhibitor, the AUCs of saquinavir, indinavir, and nelfinavir were significantly increased compared with mono-treatment. The AUCs of saquinavir were increased about 10.1-, 3.1- and 45.9-fold in the presence of indinavir, nelfinavir and ritonavir, respectively. The AUCs of indinavir were increased about 6.8-, 5.9- and 9.4-fold in the presence of nelfinavir, saquinavir and ritonavir, respectively. The AUCs of nelfinavir were increased about 2.2-, 6.6- and 8.5-fold in the presence of indinavir, saquinavir and ritonavir, respectively. The in-vivo effects observed after co-administration of two kinds of HIV-1 protease inhibitor were not always expected from in-vitro data, suggesting the presence of other interaction processes besides metabolism in the liver. These results provide useful information for the treatment of AIDS patients receiving combination therapy with two HIV-1 protease inhibitors.

Animals↗

PubMed2000

Novel enantioselective fluorinating agents, (R)- and (S)-N-fluoro-3-tert-butyl-7-nitro-3,4-dihydro-2H-benzo[e][1,2]thiazine 1,1-dioxides.

Enantioselective fluorinating agents, (R)- and (S)-,N-fluoro-3-tert-butyl-7-nitro-3,4-dihydro-2H-benzo[e][1,2]thiazine 1,1-dioxides (BNBT-F, 2) are readily prepared in 3 steps from racemic 3-tert-butyl-7-nitro-3,4-dihydro-2H-benzo[e][1,2]thiazine 1,1-dioxides (5) via optical resolution and fluorination. These agents make accessible both enantiomers of optically active quaternary alpha-fluoro carbonyl compounds in modest to high enantioselectivities. X-ray crystallographic analysis of chiral 2 reveals a unique structure wherein the nitrogen atom is highly pyramidalized and fluorine occupies an axial position.

Crystallography, X-Ray↗