Biomedical subjects

T Mizushima

Publications and source records attributed to T Mizushima.

At least 19 recordsLinked to original sources

PubMed2003

Beliaev damping and Kelvin mode spectroscopy of a Bose-Einstein condensate in the presence of a vortex line.

It is demonstrated theoretically that the counter-rotating quadrupole mode in a vortex of Bose-Einstein condensates can decay into a pair of Kelvin modes via the Beliaev process. We calculate the spectral weight of a density-response function within the Bogoliubov framework, taking account of both Beliaev and Landau processes. Good agreement with experiment on 87 Rb by Bretin et al. [Phys. Rev. Lett., 100403 (2003)]] allows us to unambiguously identify the decayed mode as the Kelvin wave propagating along a vortex line.

Journal Article↗

PubMed2003

Muscle endurance and power spectrum of the triceps brachii in wheelchair marathon racers with paraplegia.

OBJECTIVE: To investigate differences in triceps brachii endurance and electrical activity between elite marathon and recreational wheelchair athletes with paraplegia. DESIGN AND METHODS: Nine male elite wheelchair athletes between 20 and 46 years of age (average 29.0 +/- 8.2 years) with complete (ASIA-A) T4-L1 paraplegia were compared to a group of six male height- and weight-matched recreational wheelchair athletes with similar ages and injuries. Right triceps brachii maximum voluntary contraction (MVC), as well as the duration of the ability to maintain a 50% MVC were determined for all subjects. Median frequency (MF) and mean power frequency (MPF) were evaluated with fast Fourier transform spectrum analysis. MF and MPF rates of change were calculated and compared with the Student's t-test. SETTING: : Department of Rehabilitation Medicine, University of Occupational and Environmental Health, Japan. RESULTS: Right triceps brachii MVCs of the marathoners (42.4 +/- 8.8 N m (range 33-55 N m)) and recreational athletes (41.6 +/- 9.3 N m (range 32-56 N m)) did not differ significantly (P = 0.63). Endurance, however, did. All of the athletes, but none of the control subjects, were able to maintain a 50% MVC contraction of the right triceps brachii for 2 min (the average contraction duration in the latter group was 75.5+/-16.2 s). MF and MPF of the triceps brachii decreased linearly in both groups, but the slopes in the marathoners (-8.9 +/- 4.6 (-3.8 to -16.4) and -9.7 +/- 4.6 (-4.0 to -17.2)%/min, respectively) were statistically less steep than those in the recreational athletes (-22.3 +/- 8.2 (-9.6 to -31.4) and -21.2 +/- 6.4 (-11.4 to -28.6)%/min, respectively). CONCLUSION: Elite marathoners and active wheelchair users have similar triceps brachii strength. The marathoner's triceps brachii, however, display a significantly improved endurance and a slower decline of MF and MPF with time than do those of their recreational athlete control group.

Adult↗

PubMed2002

Mermin-ho vortex in ferromagnetic spinor Bose-Einstein condensates.

The Mermin-Ho and Anderson-Toulouse coreless vortices are demonstrated to be thermodynamically stable in ferromagnetic F = 1 spinor Bose-Einstein condensates under rotation. We have carried out extensive calculations of the Gross-Pitaevskii equations by assuming uniform density along the z axis and comparing the energies of other competing non-axis-symmetric or singular vortices. The phase diagram is thereby established in a plane of the rotation drive vs the total magnetization. Their stability is also checked by calculating collective modes based on the Bogoliubov equations.

Journal Article↗

PubMed2002

The relationship between consumption of antimicrobial agents and the prevalence of primary Helicobacter pylori resistance.

BACKGROUND: Primary and acquired resistance to the antimicrobial agents is a primary reason for the failure of Helicobacter pylori eradication therapies. We assessed the primary antibiotic resistance rates of H. pylori to three different antibiotics and its relationship due to the annual antibiotic consumption in Japan during the period prior to approval of anti-H. pylori therapy in Japan. MATERIALS AND METHODS: Antibiotic susceptibility was tested using the agar dilution method for clarithromycin, amoxicillin and metronidazole. Isolates were considered resistant when the MIC value was > 8 mg/l for metronidazole, > 1 mg/l for clarithromycin and < 0.5 mg/l for amoxicillin. RESULTS: Helicobacter pylori isolates were obtained from 593 Japanese patients from 1995 to 2000. Primary resistance of H. pylori to clarithromycin, metronidazole and amoxicillin was found in 11%, 9% and 0.3% strains, respectively. The proportion with clarithromycin resistance significantly increased from 7% in 1997-98 to 15.2% in 1999-2000 (p =.003). During the same period the metronidazole resistance rate also increased from 6.6% in 1997-98 to 12% in 1999-2000 (p =.02). The prevalence of clarithromycin and metronidazole was related to the annual consumption of these antimicrobial agents. CONCLUSION: Resistance rates for both clarithromycin and metronidazole appear to reflect the annual consumption of these agents. The high rate of clarithromycin resistance in Japan suggests that the effectiveness of clarithromycin-based therapies may be compromised in the near future.

Anti-Bacterial Agents↗

PubMed2001

The first direct oxidative conversion of a selenol to a stable selenenic acid: experimental demonstration of three processes included in the catalytic cycle of glutathione peroxidase.

[structure: see text]. A stable selenenic acid was synthesized by direct oxidation of a selenol bearing a novel bowl-type substituent with H2O2, and its structure was established by X-ray crystallographic analysis. Selenenyl sulfides obtained by the reaction of the selenenic acid with 1,4-dithiols were reduced to the corresponding selenol by treatment with a tertiary amine, thus achieving the experimental demonstration of three processes included in the catalytic cycle of glutathione peroxidase.

Catalysis↗

PubMed2001

Na+-driven multidrug efflux pump VcmA from Vibrio cholerae non-O1, a non-halophilic bacterium.

A chromosomal DNA fragment from Vibrio cholerae non-O1 containing a drug resistance determinant was cloned and sequenced. The deduced amino acid sequence suggested that the determinant gene encodes a multidrug efflux pump. We designated the pump VcmA. Escherichia coli cells transformed with a plasmid carrying the vcmA gene showed increased resistance against norfloxacin, ciprofloxacin, ofloxacin, daunomycin, doxorubicin, streptomycin, kanamycin, ethidium bromide, 4',6-diamidino-2-phenylindole dihydrochloride, Hoechst 33342 and acriflavine. Na+ (or Li+)-dependent efflux of ethidium bromide was detected in transformant cells. Efflux of Na+, elicited by ethidium bromide, was observed from transformant cells. Thus, we concluded that the VcmA is a Na+/drug antiporter.

Anti-Bacterial Agents↗

PubMed2001

Construction of a series of mutants lacking all of the four major mex operons for multidrug efflux pumps or possessing each one of the operons from Pseudomonas aeruginosa PAO1: MexCD-OprJ is an inducible pump.

We constructed a series of deletion mutants lacking all of the four major mex operons for Mex multidrug efflux pumps or possessing each one of the operons from Pseudomonas aeruginosa PAO1. The drug specificity of MexAB-OprM, MexXY-OprM and MexCD-OprJ was investigated. Surprisingly, we found that the MexCD-OprJ was an inducible pump, inducers of which were tetraphenylphosphonium chloride, ethidium bromide, rhodamine 6G and acriflavine. Fluoroquinolones, chloramphenicol, erythromycin and tetracycline were not inducers although they were substrates of MexCD-OprJ.

Anti-Bacterial Agents↗

PubMed2001

Attributable risk of H. pylori in peptic ulcer disease: does declining prevalence of infection in general population explain increasing frequency of non-H. pylori ulcers?

Recent reports in the United States have found that fewer peptic ulcers are due to Helicobacter pylori than previously believed. The aim of this study is to determine if the declining prevalence of H. pylori infection in the general population can account for the apparent increase in the frequency of non-H. pylori ulcers. A total of 396 patients with peptic ulcer or ulcer scar were enrolled in this study. The pre-1950 population consisted of 149 patients with gastric ulcers and with 44 duodenal ulcers. The post-1950 population consisted of 96 patients with gastric ulcers and 107 with duodenal ulcers. The frequency of H. pylori-negative gastric ulcers was 5.4% in patients born before 1950 and 4.2% in patients born after 1950, and the frequency of H. pylori-negative duodenal ulcers was 0% and 1.9%, respectively. There are no statistical differences between the two populations in gastric and duodenal ulcers. H. pylori seropositivity was 74.9% in asymptomatic volunteers born before 1950 and 20.7% in those born after 1950 (P < 0.01) in the general population. The attributable risk of H. pylori infection in peptic ulcer diseases was not affected by the prevalence of H. pylori infection in the general population in Japan. This suggests that the apparent increase in frequency of non-H. pylori ulcers in the United States is not simply due to the declining prevalence of infection. Other explanations for non-H. pylori ulcers should be sought.

Adult↗

PubMed2001

Efficacy of triple therapy with rabeprazole for Helicobacter pylori infection and CYP2C19 genetic polymorphism.

BACKGROUND: Rabeprazole is a new, potent, proton pump inhibitor. The metabolism of rabeprazole is less dependent on CYP2C19 genetic polymorphism. METHODS: A total of 102 Helicobacter pylori-positive patients with gastric ulcer were randomly allocated to three groups: rabeprazole 10 mg (RAC10), rabeprazole 20 mg (RAC20) or rabeprazole 40 mg (RAC40) plus amoxicillin 750 mg and clarithromycin 200 mg twice daily for 7 days. CYP2C19 genotype was determined by the polymerase chain reaction-restriction fragment length polymorphism method. RESULTS: All-patients-treated-based eradication rates in patients treated with RAC10, RAC20 and RAC40 were 83%, 77% and 90%, respectively, and per protocol-based eradication rates were 83%, 80% and 90%, respectively. The eradication rates in the three groups were not significantly different. There was also no significant difference between the all-patients-treated-based eradication rate in CYP2C19 extensive metabolizers and that in poor metabolizers (86% vs. 77%). Adverse events were 12% in extensive metabolizers and 23% in poor metabolizers, and the difference in these incidence rates was also not statistically significant. CONCLUSIONS: Triple therapy with 10 mg of rabeprazole combined with amoxicillin/clarithromycin is effective for Japanese patients with H. pylori infection, and the H. pylori eradication rate is not affected by CYP2C19 genetic polymorphism.

2-Pyridinylmethylsulfinylbenzimidazoles↗

PubMed2001

X-ray crystalline structures of pyrrolidone carboxyl peptidase from a hyperthermophile, Pyrococcus furiosus, and its cys-free mutant.

In order to elucidate the mechanism of the thermostability of proteins from hyperthermophiles, X-ray crystalline structures of pyrrolidone carboxyl peptidase from a hyperthermophile, Pyrococcus furiosus (PfPCP), and its mutant protein with Ser substituted at Cys142 and Cys188 were determined at 2.2 and 2.7 A resolution, respectively. The obtained structures were compared with those previously reported for pyrrolidone carboxyl peptidases from a hyperthermophilie, Thermococcus litoralis (TlPCP), and from a mesophile, Bacillus amyloliquefaciens (BaPCP). The PfPCP structure is a tetramer of four identical subunits similar to that of the TlPCP and BaPCP. The largest structural changes among the three PCPs were detected in the C-terminal protrusion, which interacts with that of another subunit. A comparison of the three structures indicated that the high stability of PfPCP is caused by increases in hydrophobic interactions and hydrogen bonds, the formation of an intersubunit ion-pair network, and improvement to an ideal conformation. On the basis of the structures of the three proteins, it can be concluded that PfPCP does not have any special factors responsible for its extremely high stability and that the conformational structure of PfPCP is superior in its combination of positive and negative stabilizing factors compared with BaPCP.

Amino Acid Sequence↗

PubMed2001

nhaG Na(+)/H(+) antiporter gene of Bacillus subtilis ATCC9372, which is missing in the complete genome sequence of strain 168, and properties of the antiporter.

We cloned a gene which enabled Escherichia coli mutant host cells lacking all of the major Na(+)/H(+) antiporters to grow in the presence of 0.2 M NaCl from chromosomal DNA of Bacillus subtilis ATCC9372. An Na(+)/H(+) antiport activity was observed with membrane vesicles prepared from E. coli cells possessing the cloned gene, but not with vesicles from the host cells. Lithium ion was also a substrate for the antiporter. We sequenced the cloned DNA and found one open reading frame (designated nhaG) preceded by a promoter-like sequence and a Shine-Dalgarno sequence, and followed by a terminator-like sequence. The deduced amino acid sequence of NhaG suggested that it consisted of 524 residues and that the calculated molecular mass was 58.1 kDa. None of the bacterial Na(+)/H(+) antiporters so far reported, except NhaP of Pseudomonas aeruginosa and SynNhaP (NhaS1) of Synechocystis sp., showed significant sequence similarity with the NhaG. However, the NhaP, the SynNhaP, animal NHEs (Na(+)/H(+) exchangers), and some hypothetical Na(+)/H(+) antiporters of several organisms showed significant sequence similarities with the NhaG. Interestingly, the entire DNA region corresponding to the nhaG gene is missing in the reported complete genome sequence of B. subtilis strain 168. We detected a band that hybridized with the nhaG DNA in chromosomal DNA from B. subtilis ATCC9372 but not with that from strain 168. The missing DNA region (1,774 base pairs) is sandwiched by two identical sequences, TTTTCTT.

Animals↗

PubMed2001

Study on free radicals and pancreatic fibrosis--pancreatic fibrosis induced by repeated injections of superoxide dismutase inhibitor.

The exact mechanisms of the development of pancreatic fibrosis are still unknown. To clarify the relationship between pancreatic fibrosis and free radicals, the effect of the administration of a superoxide dismutase (SOD) inhibitor, diethyldithiocarbamate (DDC), on pancreatic fibrosis in rats was studied. A single intraperitoneal injection of 500 mg/kg of DDC significantly reduced SOD activity and significantly increased lipid peroxidation products in the pancreas, showing no histologic changes of inflammation or necrosis. Repeated administration of 500 mg/kg DDC, twice a week, caused inter- and intralobular fibrosis with atrophy of acinar cells in the pancreas for at least 2 weeks without fibrosis of the liver and kidney. Administration of allopurinol showed preventive effects against DDC-induced pancreatic fibrosis. In conclusion, repeated administration of DDC, which caused pancreatic fibrosis, is a new experimental model of pancreatic fibrosis from the viewpoint of oxidative stress.

Allopurinol↗

PubMed2001

Marked potentiation of activity of beta-lactams against methicillin-resistant Staphylococcus aureus by corilagin.

We found that an extract of Arctostaphylos uva-ursi markedly reduced the MICs of beta-lactam antibiotics, such as oxacillin and cefmetazole, against methicillin-resistant Staphylococcus aureus. We isolated the effective compound and identified it as corilagin. Corilagin reduced the MICs of various beta-lactams by 100- to 2,000-fold but not the MICs of other antimicrobial agents tested. The effect of corilagin and oxacillin was synergistic. Corilagin showed a bactericidal action when added to the growth medium in combination with oxacillin.

Anti-Bacterial Agents↗

PubMed2001

Clinical relevance of the babA2 genotype of Helicobacter pylori in Japanese clinical isolates.

Genotypic variation of Helicobacter pylori is speculated to associate with different clinical outcomes. In Western countries, the gene encoding blood group antigen-binding adhesin (BabA), babA2, is of high clinical relevance and is a useful marker to identify patients who are at higher risk for peptic ulceration and gastric adenocarcinoma, as are vacA and cagA. We investigated the presence of babA2 and cagA in 179 Japanese clinical isolates by PCR and Southern blot analysis and looked for correlations with various clinical outcomes (nonulcer dyspepsia, duodenal ulcers, gastric ulcers gastric adenocarcinoma, and mucosa-associated lymphoid tissue lymphoma). The prevalence of the babA2 genotype was 84.9% and that of the cagA genotype was 96.1%. There was no correlation between the babA2 and cagA genotypes, and there was no association between the babA2 or cagA status and clinical outcome. These results indicate that babA2 status is not of high clinical relevance in Japan and that Japanese strains are different from those infecting Western populations.

Adhesins, Bacterial↗

PubMed2001

NSAIDs induce both necrosis and apoptosis in guinea pig gastric mucosal cells in primary culture.

A major clinical problem encountered with the use of nonsteroidal anti-inflammatory drugs (NSAIDs) such as indomethacin is gastropathy. In this study, we examined, using guinea pig gastric mucosal cells in primary culture, how NSAIDs damage gastric mucosal cells. The short-term treatment of cells with high concentrations of indomethacin decreased cell viability in the absence of apoptotic DNA fragmentation, chromatin condensation, or caspase activation. Cells lost membrane integrity with this short-term indomethacin treatment, suggesting that indomethacin induced necrosis under these conditions. In contrast, the long-term treatment of cells with low concentrations of indomethacin decreased cell viability and was accompanied by apoptotic DNA fragmentation, chromatin condensation, and caspase activation. Pretreatment of cells with inhibitors of caspases or protein synthesis suppressed cell death caused by long-term indomethacin treatment, suggesting that apoptosis was induced when the inhibitors were not present. These results imply that NSAIDs cause gastric mucosal damage through both necrosis and apoptosis of gastric mucosal cells.

Amino Acid Chloromethyl Ketones↗

PubMed2001

Geranylgeranylacetone protects guinea pig gastric mucosal cells from gastric stressor-induced necrosis by induction of heat-shock proteins.

Gastric mucosal cell death due to various gastric stressors can cause several types of gastric diseases, such as gastric ulcers. In this study, we examined cell death following the short-term treatment of guinea pig gastric mucosal cells in primary culture with various gastric stressors. The short-term treatment of cells with ethanol, hydrogen peroxide or hydrochloric acid caused, in a dose-dependent manner, cell death in the absence of apoptotic DNA fragmentation and chromatin condensation. Cells lost membrane integrity following the treatment with each of these gastric stressors, suggesting that necrosis was induced in gastric mucosal cells by short-term treatment of the cells with gastric stressors. Geranylgeranylacetone, an anti-ulcer drug with heat-shock protein inducing properties, protected gastric mucosal cells from the necrotic cell death caused by each of these gastric stressors. Pretreatment of cells with low concentrations of ethanol (3%), which also induced heat-shock protein, made cells resistant to the necrotic cell death caused by the gastric stressors. These results suggest that heat-shock proteins is involved in the cytoprotective effect of geranylgeranylacetone against necrotic cell death.

Animals↗

PubMed2001

[Virulence gene of H. pylori].

H. pylori is a well-recognized pathogen that infects up to 50% of humans in the world. H. pylori lives for decades in the hostile environment of the human stomach. H. pylori is closely associated with histologic gastritis, gastric ulceration, duodenal ulceration, gastric cancer and MALT lymphoma. These various clinical outcomes are considered by 1) different virulence, 2) host response, 3) other environmental factors, and their interactions. Since the whole genome was sequenced in 1997, the virulence genes have been investigated in molecular genetic aspects. The cag pathogenicity island (cagPAI) is a complex of virulence genes, which code approximately 30 proteins. The cagPAI acquired by horizontal transfer and is coding for type 4 secretion machinery system. Via this system, many virulence gene products or other interactive proteins are transferred into the host cells.

Adhesins, Bacterial↗

PubMed2001

[Perioperative management of a child with congenital nephrogenic diabetes insipidus].

The key point in perioperative management of a patient with congenital nephrogenic diabetes insipidus is fluid and electrolytes management. Since the urine of these patients consists mainly of solute free water, replacement fluids should be fluids which provide free water. A 2-year-old girl with congenital nephrogenic diabetes insipidus was scheduled for dental extraction. Her daily fluid intake was 10 liter. She had a history of recurrent fever, polyuria and polydipsia since 2 months of age. Her previous perioperative course for gastric volvulus at another hospital was complicated with postoperative hyponatremia and convulsion. A venous line was secured the day before surgery and 5% dextrose in water was infused at a rate of 12 ml.kg-1.hr-1. Intraoperative infusion was mainly with 5% dextrose in water combined with maintenance fluid. Five hours after surgery oral intake was started. Her intraoperative electrolytes levels were low (Na 133 mEq.l-1, K 2.8 mEq.l-1), but otherwise her perioperative course was uneventful.

Anesthesia, Inhalation↗