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Shinichi Nakamura

Publications and source records attributed to Shinichi Nakamura.

At least 37 records · Page 2Linked to original sources
PubMed2003

Clostridium absonum alpha-toxin: new insights into clostridial phospholipase C substrate binding and specificity.

Clostridium absonum phospholipase C (Caa) is a 42.7 kDa protein, which shows 60% amino acid sequence identity with the Clostridium perfringens phospholipase C, or alpha-toxin (Cpa), and has been isolated from patients suffering from gas gangrene. We report the cloning and sequencing, purification, characterisation and crystal structure of the Caa enzyme. Caa had twice the phospholipid-hydrolysing (lecithinase) activity, 1.5 times the haemolytic activity and over seven times the activity towards phosphatidylcholine-based liposomes when compared with Cpa. However, the Caa enzyme had a lower activity than Cpa to the free (i.e. not in lipid bilayer) substrate para-nitrophenylphosphorylcholine, towards sphingomyelin-based liposomes and showed half the cytotoxicity. The lethal dose (LD(50)) of Caa in mice was approximately twice that of Cpa. The crystal structure of Caa shows that the 72-93 residue loop is in a conformation different from those of previously determined open-form alpha-toxin structures. This conformational change suggests a role for W84 in membrane binding and a possible route of entry into the active site along a hydrophobic channel created by the re-arrangement of this loop. Overall, the properties of Caa are compatible with a role as a virulence-determinant in gas gangrene caused by C.absonum.

Amino Acid Sequence↗
PubMed2003

Sequence of the gene for Clostridium botulinum type B neurotoxin associated with infant botulism, expression of the C-terminal half of heavy chain and its binding activity.

Previously, we demonstrated that the neurotoxin of strain 111 (111/NT) associated with type B infant botulism showed antigenic and biological properties different from that (Okra/NT) produced by a foodborne botulism-related strain, Okra. In this study, the neurotoxin genes of 111/NT and Okra/NT were amplified and the sequences determined. The nucleotide sequences of the genes for both neurotoxins possessed an open reading frame of 3873 bp that encoded 1291 amino acids. The identities of nucleotide sequences and amino acid sequences were 97.6% and 95.7%, respectively. The ratio of nonsynonymous to synonymous substitutions was 0.47. The amino acid substitutions between 111/NT and Okra/NT occurred mainly in the domain of the C-terminal half of heavy chain (H(C)) responsible for binding to its receptor complex of protein and ganglioside. To characterize the binding capability of the H(C), recombinant genes for the H(C) and two hybrid H(C) in which one half of Okra/NT was replaced by the homologous half of 111/NT were constructed and expressed in Escherichia coli. The binding activity of the recombinant H(C) of 111/NT to the protein receptor synaptotagmin II, in the presence of ganglioside GT1b, was 4.2-fold less than Okra/NT, consistent with the corresponding two NTs. The use of hybrid H(C) revealed that mutation of 23 residues in carboxy terminal half of H(C) (1029-1291) of Okra/NT could be attributed to the lower binding activity of 111/NT and thus the differences in binding affinity between the two BoNT/B.

Amino Acid Sequence↗
PubMed2003

Measurement of fractional anisotropy using diffusion tensor MRI in supratentorial astrocytic tumors.

In vivo, water diffusion displays directionality due to presence of complex microstructural barriers in tissue. The extent of directionality of water diffusion can be expressed as a fractional anisotropy (FA) value, using diffusion tensor MR imaging (DTI). The aim of this study was to determine whether FA values indicate microstructures in astrocytic tumors. We performed DTI in 31 patients with astrocytic tumor, and measured the FA values of tumor and normal brain regions prior to CT-guided stereotactic biopsy. After biopsy, FA values were compared to assess the cellularity and vascularity of tumor tissue. Although mean FA values trended to differ among histological types, all mean tumor FA values were lower than those of normal brain regions. Positive correlation was observed between FA values and both cellularity (r = 0.65, p < 0.05) and vascularity (r = 0.45, p < 0.05). We had hypothesized that the FA value of an astrocytic tumor would be determined by a balance between factors increasing the directionality of water diffusion, such as high cellularity and/or vascularity, and factors decreasing the directionality of water diffusion, such as fiber destruction. However, our results suggest that the FA values of glioblastoma, anaplastic astrocytoma, diffuse astrocytoma and pilocytic astrocytoma are largely affected by cellularity and/or vascularity, whereas that of gliomatosis cerebri are largely affected by the preservation of nerve fibers. Measurement of FA value using DTI will allow prediction of histological characteristics such as cellularity, vascularity and/or fiber structure in astrocytic tumors.

Adult↗
PubMed2003

Comparative analysis of apoptosis-inducing activity of codeine and codeinone.

BACKGROUND: There are relatively few studies about the antiproliferative effects of codeine-related compounds on human cancer cell lines, compared with those of morphine-related compounds. The authors previously found that codeinone, an oxidation metabolite of codeine, among 10 opioids, showed the highest cytotoxic activity (DNA fragmentation-inducing activity) against human promyelocytic leukemic cell lines (HL-60). This was counteracted by an antioxidant, N-acetyl-L-cysteine (NAC). These findings prompted us to perform a more detailed study of apoptosis induction after codeinone treatment. METHODS: Apoptosis was induced by treating HL-60 cells for 1-6 h with codeine or codeinone. DNA fragmentation was assessed by both agarose gel electrophoresis and fluorometric determination of the fragmented DNA after staining with diamidinophenylindole (DAPI). The appearance of apoptotic cells was monitored by microscopic observation after staining with Hoechst (H)-33342, and fluorescence activated cell sorter (FACS) after staining with Annexin. The release of cytochrome c and cytochrome oxidase from mitochondria and activation of caspase 3 were monitored by Western blot analysis. Intracellular caspase 3-like activity was confirmed by FACS, using cell permeable substrate. Mitochondrial manganese-containing superoxide dismutase (MnSOD) activity and mRNA expression were assayed by activity staining after separation on the polyacrylamide gel electrophoresis, and reverse transcriptase-polymerase chain reaction (RT-PCR), respectively. RESULTS: Codeinone induced internucleosomal DNA fragmentation and production of Annexin-positive apoptotic cells more potently than codeine in HL-60 cells. Codeinone stimulated the release of both cytochrome c and cytochrome oxidase, and cleavage of procaspase 3 without significant changes in both the activity and expression of MnSOD. CONCLUSIONS: Codeinone was found to possess both apoptosis and necrosis-inducing activity, in addition to the reported antinociceptive activity, further substantiating its antitumor potential.

Analgesics, Opioid↗
PubMed2003

Clostridium sordellii phospholipase C: gene cloning and comparison of enzymatic and biological activities with those of Clostridium perfringens and Clostridium bifermentans phospholipase C.

The gene encoding Clostridium sordellii phospholipase C (Csp) was cloned and expressed as a histidine-tagged (His-tag) protein, and the protein was purified to compare its enzymatic and biological activities with those of Clostridium perfringens phospholipase C (Cpa) and Clostridium bifermentans phospholipase C (Cbp). Csp was found to consist of 371 amino acid residues in the mature form and to be more homologous to Cbp than to Cpa. The egg yolk phospholipid hydrolysis activity of the His-tag Csp was about one-third of that of His-tag Cpa, but the hemolytic activity was less than 1% of that of His-tag Cpa. His-tag Csp was nontoxic to mice. Immunization of mice with His-tag Cbp or His-tag Csp did not provide effective protection against the lethal activity of His-tag Cpa. These results indicate that Csp possesses similar molecular properties to Cbp and suggest that comparative analysis of toxic and nontoxic clostridial phospholipases is helpful for characterization of the toxic properties of clostridial phospholipases.

Amino Acid Sequence↗
PubMed2003

[Propofol depresses the activity of hypoglossal nerve more than that of phrenic nerve in rabbits].

BACKGROUND: Respiratory depression, such as obstruction of upper airway and inadequate ventilation, often appears during sedation and anesthesia. We studied the effect of propofol on the upper airway patency and the inspiratory drives. METHODS: Experiments were performed on the adult rabbits vagotomized, paralyzed and ventilated with nitrous oxide-oxygen-sevoflurane. We evaluated and compared depressant effect of propofol on the peak amplitude of both hypoglossal nerve (AMP-HG) and phrenic nerve (AMP-PH) activities, inspiratory time (Ti), expiratory time (Te) and respiratory cycle (Tc). RESULTS: Bolus injections of propofol transiently reduced AMP-HG more than AMP-PH (18 and 70% of control, respectively). But AMPs returned to the control levels about 10-15 min after the injection. For 0.5 mg.kg-1.min-1 continuous infusion, propofol soon began to reduce both AMPs. AMP-HG was reduced to about 20% and AMP-PH to 60% of control. Administration of propofol with 1.0 mg.kg-1.min-1 caused more reduction in AMPs with respiratory slowing and AMP-HG disappeared in some animals. CONCLUSION: During the sedation with low dose of propofol, we need to pay attention to potential upper airway obstruction. In addition to the above, high doses of propofol could reduce spontaneous inspiratory drive, and we need to keep both upper airway patency and sufficient ventilation.

Anesthetics, Intravenous↗
PubMed2003

[How do diazepam and flumazenil influence respiratory control by the activities of both hypoglossal and phrenic nerves in rabbits?].

BACKGROUND: Upper airway obstruction and inadequate ventilation often arise during sedation and anesthesia by benzodiazepines. To estimate the influence of benzodiazepines on the respiratory control, we studied the effect of diazepam and flumazenil on the neural activity and the respiratory response caused by a brief (60 sec) respiratory arrest (RA) observed in the hypoglossal nerve (HG) and phrenic nerve (PH) in rabbits. METHODS: Experiments were preformed on adult rabbits vagotomized, paralyzed and ventilated artificially with 50% N2O, 50% oxygen and 0.3-0.5% sevoflurane. We evaluated and compared the effects of diazepam and flumazenil on the peak amplitude (AMP-HG&PH) and the root mean square (RMS-HG&PH) of HG and PH, and respiratory cycle (Tc). RESULTS: Diazepam depressed HG activity more than PH activity with no influence on Tc. But it did not cause dose-related depression. Flumazenil 0.2 mg.kg-1 completely reversed the respiratory depressions caused by diazepam with the increased Tc. In addition to augmentation of the hypoglossal activity in inspiration, flumazenil caused a rise in its activity in pan-expiratory period in some cases. Additional administration of diazepam 6 mg.kg-1 following flumazenil depressed PH activity again, but did not affect HG activity any more. There was no significant depression in cardiovascular parameters with tested dosages of diazepam and flumazenil. RA response was characterized by raised AMPs and augmented RMSs (delta AMPs, delta RMSs) with marked prolongation in Tc (delta Tc). Diazepam depressed RA response dose dependently, but flumazenil did not seem to antagonize this depression. CONCLUSIONS: These results suggest that 1) flumazenil is not only a specific antagonist of benzodiazepines but also a potential excitatory agent of hypoglossal nerve activity, and that 2) there is some functional diversity in disposition of benzodiazepine-receptor binding GABAA-receptor responsible for neural respiratory control system.

Action Potentials↗
PubMed2002

Accumulation of 14-3-3 proteins in glial cytoplasmic inclusions in multiple system atrophy.

Glial cytoplasmic inclusions are the pathological hallmark of multiple system atrophy. However, the molecular mechanisms underlying the formation of glial cytoplasmic inclusions remain unclear. Alpha-synuclein, a major component of glial cytoplasmic inclusions, has the ability to interact with 14-3-3 proteins, which mediate several types of signal transduction pathways. To elucidate the role of these 14-3-3 proteins in patients with multiple system atrophy, we performed immunohistochemical studies on 14-3-3 in brain tissue specimens from 7 control subjects and from 15 patients with multiple system atrophy. In both control and multiple system atrophy cases, 14-3-3 immunoreactivity was observed mainly in the neuronal somata and proximal processes, as well as the nerve fibers. Even in the severely affected regions of patients with multiple system atrophy, 14-3-3 immunoreactivity generally was spared in the surviving neurons, some of which were strongly immunolabeled. In addition, numerous glial cytoplasmic inclusions were intensely immunostained, and neuronal cytoplasmic inclusions and dystrophic neurites were also immunoreactive for 14-3-3. Our results suggest that an aberrant accumulation of 14-3-3 proteins may occur in brains affected by multiple system atrophy, and that 14-3-3 proteins may be associated with the pathogenesis of multiple system atrophy.

14-3-3 Proteins↗
PubMed2002

14-3-3 proteins in Lewy bodies in Parkinson disease and diffuse Lewy body disease brains.

Several components of Lewy bodies have been identified, but the precise mechanism responsible for the formation of Lewy bodies remains undetermined. The 14-3-3 protein family is involved in numerous signal transduction pathways and interacts with alpha-synuclein, which is a major constituent of Lewy bodies. To elucidate the role of 14-3-3 proteins in neuro-degenerative disorders associated with Lewy bodies, we performed immunohistochemical studies on 14-3-3 in brains from 5 elderly control subjects and from 10 patients with Parkinson disease (PD) or diffuse Lewy body disease (DLBD). In the normal controls, 14-3-3-like immunoreactivity was mainly observed in the neuronal somata and processes in various cortical and subcortical regions. In the PD and DLBD cases, a similar immunostaining pattern was found and immunoreactivity was generally spared in the surviving neurons from the severely affected regions. In addition, both classical and cortical Lewy bodies were intensely immunolabeled and some dystrophic neurites were also immunoreactive for 14-3-3. Our results suggest that 14-3-3 proteins may be associated with Lewy body formation and may play an important role in the pathogenesis of PD and DLBD.

14-3-3 Proteins↗
PubMed2002

Linkage between toxin production and purine biosynthesis in Clostridium difficile.

The production of toxins A and B by Clostridium difficile was greatly enhanced under biotin-limited conditions, in which a 140-kDa protein was expressed strongly. Gene cloning revealed that this protein was a homologue of formylglycinamidine ribonucleotide synthetase (FGAM synthetase, EC 6.3.5.3), which is known as PurL in Escherichia coli and catalyses the fourth step of the de novo purine biosynthesis pathway. This enzyme consisted of a single polypeptide, although FGAM synthetases of gram-positive bacteria usually consist of two subunits. Inhibition of the enzymic activity of C. difficile PurL by O-diazoacetyl-L-serine (azaserine) resulted in enhanced toxin B production even in biotin-sufficient conditions. In contrast, blockade of the preceding step of the PurL catalysing step by sulfamethoxazole inhibited toxin B production almost completely. These results suggest that accumulation of formylglycinamide ribonucleotide (FGAR), a substrate of FGAM synthetase, enhances toxin production by C difficile and depletion of FGAR reduces toxin production.

Amino Acid Sequence↗
PubMed2002

emm Typing of group A streptococcus clinical isolates: identification of dominant types for throat and skin isolates.

T and emm types were determined for group A streptococci isolated from patients with various infections during 1990-1999 in Toyama Prefecture, Japan. Out of 906 isolates, 872 isolates were divided into 20 T serotypes, and 34 isoltes were T nontypeable (TNT). T12, T1, and T4 were dominant among 699 throat isolates; on the other hand, T11, T28, TB3264, and TNT were dominant among 80 skin isolates. The emm types of 190 isolates were determined following specific PCR amplification and sequencing of the products. Twenty T serotypes were divided into 34 T type/emm type combinations. Thirty-four TNT isolates were divided into 14 emm types, in which emm58 was the most common (38%). Among 82 throat isolates randomly selected, predominant T types T12, T1, and T4 isolates were of the respective same numbers in emm type. T11/emm89, T28/emm28, TB3264/emm13w, and TNT/emm58 were predominant among 80 skin isolates. emm-type distribution observed in the present study was that usually reported in the western world. To our knowledge, 3 T/emm is a novel combination. These results show that emm typing allows the characterization of group A streptococci from various sources.

Antigens, Bacterial↗
PubMed2002

[Reflux esophagitis].

There are some factors which influence reflux esophagitis, in our country atrophic gastritis is important for the degree of it especially. Helicobacter pylori(H.P.) infection is popular in aged patients, so atrophic gastritis is also popular in such patients, then the frequency of reflux esophagitis is low comparing with other countries. But because of the late of H.P. infection comes to be higher and the eradication therapy for the peptic ulcer diseases has been done in these days, the late of atrophic gastritis comes to be lower and reflux esophagitis comes to be higher. In aged patients medication and physical factors influence reflux esophagitis and these factors are different in each patient. So it is very important to treat the patient of reflux esophagitis considering of each factor.

2-Pyridinylmethylsulfinylbenzimidazoles↗
PubMed2002

Characterization of Clostridium butyricum neurotoxin associated with food-borne botulism.

The neurotoxin of Clostridium butyricum strain LCL155 (BuNT/LCL155) associated with type E food-borne botulism showed antigenic and biological properties different from those of C. botulinum type E (BoNT/E) andC. butyricum strain BL5262 (BuNT/BL5262). The specific toxicity of BuNT/LCL155 was found to be about 10% those of BoNT/E and BuNT/BL5262. Immunological analysis with monoclonal antibodies against BoNT/E showed that the heavy chain of BuNT/LCL155 differs partially from those of BoNT/E and BuNT/BL5262. Binding experiments with rat brain synaptic membrane revealed that BuNT/LCL155 possesses a binding activity lower than either BoNT/E or BuNT/BL5262. There was no difference in the catalytic activity of the three neurotoxins, which had been determined with a recombinant of the intracellular target protein SNAP-25. These data suggest that the BuNT/LCL155 shares the receptor-recognition site structurally different from BoNT/E and BuNT/BL5262, perhaps causing a decreased specific toxicity.

Amino Acid Sequence↗
PubMed2001

Differential expression between synaptic vesicle proteins and presynaptic plasma membrane proteins in the anterior horn of amyotrophic lateral sclerosis.

This study concerns the immunohistochemical investigation of synaptic proteins in the anterior horn of amyotrophic lateral sclerosis (ALS). Antibodies against synapsin 1 and synaptophysin (i.e. synaptic vesicle proteins), and those against syntaxin and the synaptosomal-associated, 25 kDa protein, SNAP25 (i.e. presynaptic plasma membrane proteins) were used for immunostaining, respectively. Lumbar spinal cords from five ALS and eight control patients were examined. In the controls, all four synaptic proteins exhibited fine granular immunoreactivities, distributed throughout the spinal gray matter almost uniformly. In contrast, in all five ALS patients, two of the synaptic vesicle proteins examined decreased in the anterior horn neuropil diffusely, while in the same lumbar segments of these cases the immunoreactivities of the two presynaptic plasma membrane proteins showed no apparent decrease, or were only mildly diminished in the same gray matter area. These results indicate that, during the presynaptic terminal degeneration in the anterior horn of ALS, synaptic vesicle involvement may precede that of the presynaptic plasma membrane.

Adult↗