Biomedical subjects

Y Asai

Publications and source records attributed to Y Asai.

At least 109 records · Page 6Linked to original sources

PubMed1999

Functional interaction between PomA and PomB, the Na(+)-driven flagellar motor components of Vibrio alginolyticus.

Four proteins, PomA, PomB, MotX, and MotY, appear to be involved in force generation of the sodium-driven polar flagella of Vibrio alginolyticus. Among these, PomA and PomB seem to be associated and to form a sodium channel. By using antipeptide antibodies against PomA or PomB, we carried out immunoprecipitation to verify whether these proteins form a complex and examined the in vivo stabilities of PomA and PomB. As a result, we could demonstrate that PomA and PomB functionally interact with each other.

Antibodies, Bacterial↗

PubMed1999

Hybrid motor with H(+)- and Na(+)-driven components can rotate Vibrio polar flagella by using sodium ions.

The bacterial flagellar motor is a molecular machine that converts ion flux across the membrane into flagellar rotation. The coupling ion is either a proton or a sodium ion. The polar flagellar motor of the marine bacterium Vibrio alginolyticus is driven by sodium ions, and the four protein components, PomA, PomB, MotX, and MotY, are essential for motor function. Among them, PomA and PomB are similar to MotA and MotB of the proton-driven motors, respectively. PomA shows greatest similarity to MotA of the photosynthetic bacterium Rhodobacter sphaeroides. MotA is composed of 253 amino acids, the same length as PomA, and 40% of its residues are identical to those of PomA. R. sphaeroides MotB has high similarity only to the transmembrane region of PomB. To examine whether the R. sphaeroides motor genes can function in place of the pomA and pomB genes of V. alginolyticus, we constructed plasmids including both motA and motB or motA alone and transformed them into missense and null pomA-paralyzed mutants of V. alginolyticus. The transformants from both strains showed restored motility, although the swimming speeds were low. On the other hand, pomB mutants were not restored to motility by any plasmid containing motA and/or motB. Next, we tested which ions (proton or sodium) coupled to the hybrid motor function. The motor did not work in sodium-free buffer and was inhibited by phenamil and amiloride, sodium motor-specific inhibitors, but not by a protonophore. Thus, we conclude that the proton motor component, MotA, of R. sphaeroides can generate torque by coupling with the sodium ion flux in place of PomA of V. alginolyticus.

Amiloride↗

PubMed1999

Control of the dispersing process and pharmacokinetics in rats for lipid A analogue, E5531.

E5531 is a synthetic disaccharide analogue of lipid A which has a low toxicity but retains the ability to reduce production of tumour necrosis factor. This analogue has potential for use in the treatment of septic shock. An injectable formulation of E5531 would be useful, but dispersion in aqueous solution is a problem. In the present study the dispersing process for E5531 was evaluated using the pH-jump method (pH 11.0-->7.3). The size of the aggregates was decreased (reaching 20 nm) with increasing dispersing time in 0.003 M NaOH (pH 11.0). The membrane fluidity of the aggregates increased with increasing dispersing time. When prepared by the normal dilution method (pH 7.3-->7.3), the size of the aggregates remained constant at 140 nm and the membrane fluidity was smaller than that of samples prepared by the pH-jump method. This indicates that during dispersing at basic pH, the hydration proceeded in a normal manner, but then stopped, just after adjustment of the pH to 7.3. This suggests that the degree of hydration of the membrane is dependent on the dispersing time at pH 11.0. Using samples with different degrees of hydration and different membrane fluidity prepared by the pH-jump method, the pharmacokinetics and stability of the aggregates were evaluated after intravenous injection into rats. The data thus obtained confirmed that the membrane fluidity was correlated with the pharmacokinetics and stability in rat plasma. It was concluded that the pharmacokinetics of E5531 in rats can be controlled by changing the degree of hydration and membrane fluidity by means of using different dispersing times in alkaline solution (pH 11.0).

Animals↗

PubMed1999

The effect of the lipid A analog, E5531 on fever induced by endotoxin from Escherichia coli.

E5531 is a specific lipid A antagonist and is expected to be a drug for the treatment of septic shock. The LAL (limulus amebocyte lysate) activity and pyrogenicity of E5531 were determined. The LAL activity of E5531 is large and confirmed that E5531 had a high affinity to the lipopolysaccharide receptor. The pyrogenic activity of E5531 is weak and the pyrogenic profile of E5531 is different from that of USP (United States Pharmacopoeia) reference standard endotoxin (ETX). E5531 suppressed the pyrogenicity of ETX in rabbits, indicating that E5531 is expected to be useful for the treatment of fever induced by ETX.

Analgesics, Non-Narcotic↗

PubMed1999

Effect of a Dynorphin A analog, E2078, on phospholipid membrane properties.

The effect of the Dynorphin A analog, E2078, on the physicochemical properties of lipid membranes was investigated. E2078 induces the leakage of calcein, especially out of negatively-charged vesicles. The peptide binds to dipalmitoylphosphatidylglycerol sonicated vesicles according to the Lamgmuir isotherm, with a binding constant of 4.0x10(5) M(-1) and a binding-site number of 0.14 per lipid molecule. The leakage seems to occur at a critical binding-site number of approx. 0.025 per lipid molecule. In addition, E2078 increased the membrane fluidity of the acidic lipid bilayer. In conclusion, E2078 interacts with acidic lipids through electrostatic interactions, inducing leakage and increasing membrane fluidity.

Dynorphins↗

PubMed1999

TMC-171A,B,C and TMC-154, novel polyketide antibiotics produced by Gliocladium sp. TC 1304 and TC 1282.

Four new antibiotics, TMC-171A (2), B (3), C (4) and TMC-154 (5) have been isolated from the fermentation of fungal strains Gliocladium sp. TC 1304 and TC 1282, respectively. Spectroscopic and degradation studies have shown that TMC-171s and TMC-154 were new members of the TMC-151 class of antibiotics, unique polyketides modified with a D-mannose and a D-mannitol or a D-arabitol. These compounds showed moderate cytotoxicity to various tumor cell lines.

Anti-Bacterial Agents↗

PubMed1999

TMC-66, a new endothelin converting enzyme inhibitor produced by Streptomyces sp. A5008.

A new endothelin converting enzyme (ECE) inhibitor, TMC-66 was isolated from the fermentation broth of Streptomyces sp. A5008. The structure of TMC-66 was elucidated by spectroscopic analyses to be a new member of benzo[a]naphthacenequinone class of antibiotics. TMC-66 had a highly selective inhibitory activity for ECE with an IC50 value of 2.9 microM. Taxonomy of the producing strain is also described.

Animals↗

PubMed1999

Home hypertension'.

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Blood Pressure Determination↗

PubMed1998

The effect of the lipid A analog E5531 on phospholipid membrane properties.

In order to determine the effect of the lipid A analog, E5531, on phospholipid membranes, we used dipalmitoylphosphatidylcholine (DPPC) and investigated the physicochemical interaction between E5531 and DPPC membranes. E5531 and DPPC are miscible in the bulk phase at 25 degrees C. Within the E5531 mole fraction range (X(E5531)) of 0-0.5, E5531 decreased the zeta potentials of DPPC membranes but did not change the size of the DPPC liposomes. E5531/DPPC mixtures formed liposome-like structures. E5531 increased the fluidity of the DPPC membrane and decreased pyrene diffusion in the membrane. E5531 decreased the phase transition temperature and the cooperative interactions between DPPC molecules. These effects of E5531 on phospholipid membranes were different from those of lipid A from Escherichia coli and Salmonella minnesota.

1,2-Dipalmitoylphosphatidylcholine↗

PubMed1998

A study of clinical features and treatment of acute bronchitis by Japanese primary care physicians.

OBJECTIVE: This study aimed to examine the factors affecting prescription of antibiotics for acute bronchitis in ambulatory care settings in Japan. METHOD: A prospective study was conducted on 92 physicians engaged in primary care regarding their prescription behaviour for a series of 20 new patients with acute respiratory diseases seen during November 1996 and the background factors affecting the behaviour. RESULTS: A total of 1755 patients were registered during the study period, 302 (17.2%) of whom were diagnosed with acute bronchitis and 1165 (66.4%) with upper respiratory tract infection. Independent background factors related to diagnosis of acute bronchitis included self-care prior to visit (odds ratio 1.93, 95% CI 1.33-2.80), complaints such as cough (8.80, 4.77-16.2), sputum (2.24, 1.59-3.14) and purulent sputum (6.47, 3.02-13.9). The odds ratio was high in patients with more severe findings of the chest (5.00, 3.64-6.85), given chest X-ray (2.68, 1.33-5.38) while it was low in those feeling cold (0.68, 0.48-0.96), and those with a sore throat (0.63, 0.45-0.90), nasal symptoms (0.75, 0.54-1.04) and more severe findings of the pharynx (0.74, 0.58-0.92). In those with an upper respiratory tract infection, the odds ratio was high for complaints such as feeling cold (1.51, 1.11-2.05) and nasal symptoms (1.39, 1.04-1.86), while it was low for complaints such as cough (0.67, 0.48-0.95), sputum (0.43, 0.30-0.62), purulent sputum (0.19, 0.08-0.44), wheeze (0.34, 0.13-0.92), in those with more severe findings of the tonsil (0.36, 0.29-0.44) and the chest (0.30, 0.19-0.47) and given chest X-rays (0.29, 0.12-0.66). For acute bronchitis, antibiotics were administered to 67.5% and symptomatic therapy concurrently given to 64.9%. As for independent background factors related to prescription of antibiotics for acute bronchitis, the odds ratio was higher in physicians denying the efficacy of antibiotics for treating a cold (4.58, 1.94-10.8), and the patients with complaints such as purulent sputum (22.9, 2.66-197.2), more severe findings of the pharynx (2.26, 1.34-3.79) and of the chest (2.73, 1.53-4.88), and those who had a body temperature measurement taken (4.42, 1.71-11.4) and a chest X-ray (6.11, 1.07-34.9), but was lower in those complaining of chills (0.16, 0.04-0.66) and diarrhoea (0.11, 0.01-1.11). CONCLUSIONS: A majority of patients receiving medical care for acute bronchitis are given an unnecessary antibiotic prescription. The result of this study may be useful for the finding of appropriate forms of intervention for changing physicians' prescription behaviour.

Acute Disease↗

PubMed1998

Optimum tube voltage for chest radiographs obtained by psychophysical analysis.

Many kinds of x-ray films having various characteristic curves have been developed for chest radiographs. In general, a phototiming device for determination of a mAs value which gives a proper exposure has been used for a chest radiography. For each film, however, the x-ray tube voltage has been determined by the subjective evaluation of radiologists or radiological technologists. In this paper, we propose a new method for determining the optimum tube voltage for chest radiographs using psychophysical analysis. The optimum density and the optimum density range of a screen/film system are obtained from the gradient curve of film and the minimum perceptible contrast delta Dmin [Acta Radiol. Diagnos. 4, 463-476 (1966)]. The optimum tube voltage, by which the lowest density of a mediastinum and the highest density of a lung field just cover the optimum density range, is obtained using the x-ray photon spectrum and sensitivity spectrum of the screen. This objective method does not depend on personal subjective evaluation, therefore it is available for the determination of optimum tube voltage for chest radiographs to be observed by many doctors of various departments.

Humans↗

PubMed1998

TMC-49A, a novel transcriptional up-regulator of low density lipoprotein receptor, produced by Streptomyces sp. AS1345.

Microbial metabolites were screened for a transcriptional up-regulator of low density lipoprotein (LDL) receptor by a reporter assay. TMC-49A was discovered as an up-regulator obtained from the fermentation broth of Streptomyces sp. AS1345. The structure of TMC-49A was elucidated to be butyl N-phenethylcarbamate by spectroscopic analyses. This compound enhanced the synthesis of LDL receptor in human hepatoma HepG2 cells as assessed by a receptor binding assay. Taxonomy of the producing strain is also described.

Carbamates↗

PubMed1998

Home blood pressure elevation by self-measurement.

OBJECTIVE: To determine whether self-measurement could raise the blood pressure of a patient whose home blood pressure is higher than the office blood pressure measurements taken by a physician. DESIGN: Case report: a 78-year-old woman measured her own blood pressure at office using a home blood pressure monitor (test). The control data were taken when no self-measurement was made. Under test and control conditions, her blood pressure and pulse rate recordings were taken at 2 min intervals using an ambulatory blood pressure monitor. RESULTS: The patient's blood pressure and pulse rate rose transiently and reproducibly as a result of self-measurement but did not rise during the control measurements. CONCLUSION: Self-measurement could increase blood pressure in this patient. This case suggests that blood pressure in some hypertensive patients could be elevated by self-measurement.

Journal Article↗

PubMed1998

Case reports on a porous alumina ceramics implant: observations at 14 years after treatment.

Bioceram Porous Implants using alumina are manufactured by Kyocera Corp. We started to use this implant in September of 1984. The subjects were 18 men and 42 women 20 to 70 years of age. We have followed up 65 implants in 60 patients for up to 13 years and 6 months. One implant in 1 patient had to be removed because of post-operative infection and 4 implants in 4 patients had to be removed due to fracturing or detachment. The clinical progress has been good in all the other 60 implants in 55 patients.

Adult↗

PubMed1997

Molecular cloning and tissue distribution of an alternatively spliced variant of an A-type K+ channel alpha-subunit, Kv4.3 in the rat.

We describe here (1) the heterogeneous expression of Ca2+-independent transient (A-type) K+ channel alpha-subunits (Kv1.4, Kv3.3, Kv3.4, Kv4.2 and Kv4.3) in rat smooth muscle, heart and brain, (2) the molecular cloning and tissue distribution of a novel alternatively spliced variant of an A-type K+ channel alpha-subunit, Kv4.3, and (3) the functional expression of A-type K+ channels in HEK293 cells by the transfection with the novel splice variant of Kv4.3. A cDNA encoding this splice variant was identified from rat vas deferens by RT-PCR cloning. This cDNA clone contains a 1965 bp open reading frame that encodes for a protein of 655 amino acids. It has a 19 amino acid insertion in comparison with Kv4.3 previously reported in rat brain. RT-PCR analyses showed that the mRNAs of this longer variant are abundantly expressed in a number of smooth muscles of the rat, and that the mRNAs of the previously reported clones are absent. The longer splice variant is very weakly expressed in brain, but is the major product in heart.

4-Aminopyridine↗

PubMed1997

Gene cloning and characterization of maleate cis-trans isomerase from Alcaligenes faecalis.

Maleate cis-trans isomerase, which catalyses the conversion of maleate to fumarate, was purified and characterized from Alcaligenes faecalis IFO13111. The molecular weight of maleate isomerase was estimated as 60 kDa, consisting of a 28 kDa dimer as shown by gel-filtration chromatography and SDS-PAGE analysis. Kinetic studies showed that the Michaelis constant for maleate was 4.0 x 10(-5) M. The reverse reaction (fumarate to maleate) activity of the enzyme was detected even though it was quite weak. The maleate isomerase gene (maiA) was cloned by hybridization using the oligonucleotide DNA probes designed on the basis of the determined N-terminal amino acid sequences of the purified enzyme. The determined DNA sequence of the maiA gene contains an open reading frame which encodes a 254-amino-acid sequence. The amino acid sequence of the maiA gene product shows no significant homology to any amino acid sequences in the protein data base.

Alcaligenes↗

PubMed1997

Cloning, sequencing, and characterization of the ftsZ gene from coryneform bacteria.

Taking advantage of highly conserved domains present in the ftsZ genes from Escherichia coli, Rhizobium meliloti, and Bacillus subtilis, we designed degenerate oligonucleotides (oligos) corresponding to these regions. These oligos were used as primers in PCR in order to amplify DNA sequences from Brevibacterium flavum MJ233 chromosomal DNA. The PCR product was used as a probe to recover genomic fragments from a lambda library of Br. flavum MJ233. The complete nucleotide sequence (nt) of the cloned 4.2-kb EcoRI fragment containing the ftsZ homolog from Br. flavum MJ233 indicated that the deduced gene product of the Br. flavum ftsZ homolog is composed of 438 amino acids (aa) with a deduced molecular weight of 46.9 kDa. This size of molecular weight was also confirmed by the in vitro protein synthesis assay. Comparison of this aa sequence to the corresponding sequences from E. coli, Rh. meliloti, B. subtilis, and Streptomyces coelicolor revealed a high degree of conservation and suggested that the Br. flavum ftsZ homolog has a putative GTP binding motif and a GTP hydrolizing region. Expression of Br. flavum ftsZ gene in E. coli, JM109 inhibited its cell division, leading to filamentation. This suggested that the Br. flavum ftsZ product competed with the E. coli ftsZ product.

Amino Acid Sequence↗

PubMed1997

Oxidative injury of synapse and alteration of antioxidative defense systems in rats, and its prevention by vitamin E.

In order to define whether active oxygen species actually induce oxidative damage to the nervous system, and how antioxidative defense systems are changed by oxidative stress, morphological and functional changes in the nervous system and antioxidant status were investigated. When rats were exposed to 100% oxygen in a chamber, many morphological changes, e.g. swollen astrocytes around vessels, deformed nuclei in nerve cells, pigmentation, swollen mitochondria, and abnormal accumulation of synaptic vesicles in swollen nerve terminals, were observed by electron microscopy. When synaptosomes isolated from oxygen-exposed rats were stimulated by KCl, acetylcholine release from the terminal was decreased more significantly than in synaptosomes from unexposed rats (P < 0.01). Synaptic plasma membrane fluidity decreased in response to oxygen exposure, and plasma membrane permeability to sucrose was increased significantly (P < 0.05). The cholesterol/phospholipid ratio of the plasma membranes was increased by oxidative stress and the content of unsaturated fatty acids, especially arachidonic acid and docosahexaenoic acid, decreased. The levels of thiobarbituric-acid-reactive substances in the plasma membranes of oxygen-exposed rats were significantly higher than in unexposed rats (P < 0.01). These results suggest that free radicals derived from oxygen may attack nerve terminals and peroxidize the plasma membrane. It was found that in response to the oxidative stress, the status of the defense system in synapse, i.e. the concentration of vitamin E, activities of superoxide dismutase and glutathione peroxidase changed, and that many of the changes observed were reduced remarkably by the intraperitoneal administration of vitamin E prior to stress. Data support the idea that vitamin E contributes to the protection against nerve dysfunction caused by oxidative stress.

Acetylcholine↗