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Biomedical subjects

N Shibuya

Publications and source records attributed to N Shibuya.

At least 73 records · Page 4Linked to original sources
PubMed1995

Differences in midazolam-induced breathing patterns in healthy volunteers.

Sex differences, and the influence of drug dosage and additional upper airway obstruction were studied in midazolam-induced breathing patterns and sedation in 30 healthy volunteers (8 males and 22 females). After administration of 0.1 mg.kg-1 midazolam (8 male and 8 female subjects), the rib cage (RC) motion increased in 6 males and the abdominal wall (ABD) motion and SaO2 decreased in all males. In contrast, the RC and ABD motions and SaO2 decreased in all females. Snoring and loss of consciousness occurred in 7 males and in 2 females. There were significant differences in the RC motion, SaO2, the incidence of snoring and the sedative state between male and female subjects. A bolus dose of 0.5 mg of flumazenil completely antagonized the sedative effect of midazolam and restored the breathing pattern, whereas it did not completely restore SaO2. A higher dose (0.2 mg.kg-1) of midazolam was administered to an additional 8 females. It caused a loss of consciousness in all subjects and increased the RC motion in only one subject. Partial obstruction of the nasal cavity was effected with cotton balls in the remaining 6 females who were sedated with 0.1 mg.kg-1 midazolam. An increase in the RC motion occurred similar to that observed in males. These findings suggest a difference in midazolam-induced sedation and breathing patterns between male and female subjects with midazolam administration on a mg.kg-1 basis.

Abdominal Muscles↗
PubMed1995

Conformation of an arabinoxylan isolated from the rice endosperm cell wall by X-ray diffraction and a conformational analysis.

The chain conformation of an arabinoxylan isolated from the rice endosperm cell wall, which was composed of the linear backbone of a 1,4-linked beta-xylose residue highly substituted at the C3 position with alpha-L-arabinofuranose, was studied by X-ray fiber diffraction and a conformational analysis. From the X-ray results the polysaccharide was suggested to take an extended left-handed, three-fold helical structure which is not a desirable conformation to make a complex firmly associated with cellulose or xyloglucan that was elucidated to be present in the cell wall. A conformational analysis, using the PFOS force field for the O-alpha-L-arabinofuranose-(1-->3)-beta-D-xylose residue and O-alpha-L-arabinofuranose-(1-->3)-[(1-->4)-beta-D-xylose residue]3, in which the arabinose residue was linked to the C3 position of the middle residue of the xylotriose residue, and using the PS79 computer program for the arabinoxylan indicated that the backbone xylan chain could not take a two-fold helix similar to that of cellulose because of significant steric interaction between the arabinose side chain and the backbone. Thus, the left-handed, three-fold helix was found to be reasonable.

Carbohydrate Conformation↗
PubMed1995

Establishment and characterization of a cell line (NB-YK) derived from a transplantable rat nephroblastoma.

A new cell line, designated NB-YK, was established from a transplantable rat nephroblastoma (NB-Y) which was derived from a spontaneous nephroblastoma in an aged Fischer 344 rat. NB-YK grew in a piling-up and noncohesive pattern on the plastic surface and formed colonies in a soft agar. The main cell type of NB-YK represented morphology of mesenchymal phenotype and most of the cells contained several secretory granules in their cytoplasm. Immunocytochemically the cells were positive for vimentin, cytokeratin, and laminin. Coexpression of vimentin and cytokeratin in the cells was confirmed by the one-dimensional gel electrophoresis and immunoblotting for intermediate filament proteins. NB-YK cells were tumorigenic and produced fibrosarcoma-like tumor when inoculated subcutaneously or intraperitoneally into syngeneic rats and nude mice. NB-YK seems to be a useful model for studying biological properties of nephroblastoma.

Animals↗
PubMed1995

[Effects of bupivacaine on Na+ and Ca2+ currents in single canine ventricular cells].

The effects of bupivacaine on Na+ and Ca2+ currents in single canine isolated left ventricular cells were examined using whole-cell voltage clamp technique to reveal the mechanism of its negative inotropism. The cells were isolated by enzymatic dispersion and superfused in an oxygenated Tyrode's solution. Bupivacaine 10(-6) M decreased the amplitude of INa and delayed the peak time. These effects were dose and frequency dependent. At a concentration of 10(-3) M, bupivacaine abolished INa. Meanwhile, bupivacaine did not modify ICa at a concentration of 10(-6) M. At 10(-5) M bupivacaine, the amplitude of ICa was depressed by 22% and the depression was dose dependent. These results suggest that low concentration (10(-6) M) of bupivacaine depresses contraction, by reducing intracellular Ca2+ secondary to reduction in intracellular Na+ activity and the Na+-Ca2+ exchange mechanism. At higher concentrations, the reduction in contraction caused by bupivacaine may result partly from a reduced influx of Ca2+.

Animals↗
PubMed1994

Immunoadsorption therapy for myasthenia gravis.

The results of a multicentre trial were analysed to evaluate the efficacy of immunoadsorption therapy for severe generalised myasthenia gravis. Twenty patients with myasthenia gravis who were concurrently receiving high dose prednisolone and azathioprine therapy were treated with an affinity-type adsorbent, using tryptophan-linked polyvinyl alcohol gel (IM-TR), according to a standardised treatment protocol. The 20 patients received five adsorption treatments within a period of 10 days. In 11, pronounced improvement of myasthenic weakness was seen and long-term remission was maintained. The treatment was especially effective in patients with thymic hyperplasia. Circulating acetylcholine receptor (AChR) antibodies were reduced by about 60% by treating one plasma volume. There was no difference in the rate of removal of the AChR antibodies between patients with thymic hyperplasia and patients with thymoma. No serious complications occurred during 100 procedures. It was concluded that the immunoadsorption therapy with IM-TR is useful in controlling symptoms in patients with severe myasthenia gravis who are otherwise unresponsive.

Adolescent↗
PubMed1994

Repulsive contribution of surface sialic acid residues to cell adhesion to substratum.

Roles of surface sialic acid residues in cell adhesion to substratum were investigated in model systems to clarify their contribution to intercellular interactions. Treatment of cells of a fibroblastic cell line, Swiss 3T3, an epithelial cell line, TES-1, and a T lymphoma cell line, BW5147, with a sialylated oligosaccharide binding lectin enhanced adhesion to plastic plates irrespective of the cell lineage. This enhancement was inhibited by the addition of sialyl lactose. Digestion of the cells with sialidase or endoglycoceramidase also augmented adhesion. On the other hand, adhesion was reduced by pre-coating plastic plates with gangliosides but not with desialylated gangliosides. These findings suggest that sialic acid residues exposed to cell surfaces negatively regulate cell adhesiveness.

3T3 Cells↗
PubMed1993

Identification of a novel high-affinity binding site for N-acetylchitooligosaccharide elicitor in the membrane fraction from suspension-cultured rice cells.

Binding experiments using a 125I-labeled tyramine conjugate of N-acetylchitooctaose, a highly potent elicitor for the induction of phytoalexin production in rice cells, and a microsomal membrane preparation from suspension-cultured rice cells showed the presence of a novel high-affinity binding site for this oligosaccharide. The binding of the ligand was saturable and the Scatchard plot analysis of the results indicated the presence of a single class of binding site with a Kd of 5.4 nM which is comparable with that reported for the binding of the hepta-beta-glucoside elicitor in soybean membrane. The ligand binding was inhibited by unlabeled N-acetylchitoheptaose but not by its deacetylated form. These characteristics of this binding site coincide well with the specificity and sensitivity for the elicitor in several assay systems, suggesting the possible involvement of this binding site in the recognition of the elicitor in vivo.

Binding Sites↗
PubMed1993

Direct kinetics of bait region cleavage of alpha-2-macroglobulin by a rapid quenching method.

The rate of bait region cleavage of human alpha-2-macroglobulin by chymotrypsin was determined by a rapid quenching method under conditions where the bimolecular encounter between the two reactants was not rate-limiting. alpha 2M was first mixed with a 30 molar excess of chymotrypsin in a sequential stopped-flow apparatus and after programmed time intervals the activity of chymotrypsin was quenched with 1 N HCl. The fraction of uncleaved subunits was quantitated by SDS-PAGE under reducing conditions. The result indicated that the bait region cleavage proceeded following a two-exponential decay curve with respective rate constants of k1 = 40 s-1 and k2 = 2 s-1.

Binding Sites↗
PubMed1993

Monomeric, monovalent derivative of Maackia amurensis leukoagglutinin. Preparation and application to the study of cell surface glycoconjugates by flow cytometry.

A stable subunit of Maackia amurensis leukoagglutinin (MMAL) was prepared by the selective reduction of disulfide bridges between the subunits followed by alkylation with 4-vinylpyridine. MMAL failed to precipitate fetuin, whereas it retained its ability to bind to the same glycoprotein coated on a plastic plate, indicating the monovalency of this derivative. This binding to immobilized fetuin was inhibited by a haptenic sugar, Neu5Ac alpha 2-3lactose, with the same inhibitory potency as against the native M. amurensis leukoagglutinin. Microscopic observation as well as flow cytometric analyses showed that Chinese hamster ovary cells were clearly stained with fluorescein isothiocyanate-labeled MMAL without any detectable agglutination. This staining was inhibited by the addition of fetuin or by the sugar chains of fetuin. Differences in the types of sialylated glycoconjugates on the cell surface of several cell lines were detected by the combined use of fluorescein isothiocyanate-labeled MMAL and the monomeric derivative of elderberry bark lectin (specific for the Neu5Ac alpha 2-6Gal/GalNAc sequence) by flow cytometry. These results demonstrate the usefulness of these monovalent derivatives of sialylated oligosaccharide-specific lectins as probes for the analysis of cell surface glycoconjugates containing sialic acid by the technique of flow cytometry.

Amino Acids↗
PubMed1993

Actions of benzalkonium chloride as a potent depressant at the neuromuscular junction.

Benzalkonium chloride (BA), a positively charged surface active agent, applied (> 10 nM) in the superfusing solution, produced a concentration-dependent reduction in the amplitude of both evoked endplate potentials (EPPs) and spontaneous miniature EPPs of the frog. Voltage-clamped endplate currents (EPCs) and spontaneous miniature endplate currents (MEPCs) were also diminished in amplitude, in the presence of BA (50-140 nM), whereas their time-course and reversal potential were not obviously affected. No significant change due to the addition of 50 nM BA was observed in apparent properties of the ACh channel estimated from ACh-induced current fluctuations. In the relationship between the amplitude of ACh potentials and the net charge for iontophoretic pulses at a single junction, the principal pattern of action of BA (30-60 nM) appeared to be a parallel shift to the right. At concentrations greater than about 1 microM, BA slightly increased the resting input conductance of the non-synaptic muscle fibre membrane. It was suggested that this increase was attributable to a slight increase in Cl ion conductance of the non-synaptic membrane. These results indicate that BA effectively blocked neuromuscular transmission, acting as an ACh receptor antagonist at smaller concentrations and as a more potent blocker that acts through multiple sites at greater concentrations.

Acetylcholine↗
PubMed1993

Effects of bupivacaine on contraction and membrane potential in isolated canine papillary muscles.

The effects of bupivacaine on myocardial contraction and membrane potential were examined in isolated canine right ventricular papillary muscles. Bupivacaine (10(-6) to 10(-4) mol/l) produced a dose-dependent and reversible decrease in the electrically induced contractile response of canine right ventricular papillary muscles. The inhibitory effects of bupivacaine on contraction were more pronounced at high stimulation frequencies (2 and 3 Hz) than at low frequency (< 1 Hz). The resting membrane potential was not affected by bupivacaine. The maximal upstroke velocity of the action potential was reduced by 10(-6) mol/l bupivacaine (74 +/- 28% of control), and these effects were also dose dependent. At 10(-4) mol/l, bupivacaine blocked fast action potentials in normal Tyrode's solution. Furthermore, bupivacaine (10(-4) and 10(-3) mol/l) decreased both slow action potential duration and associated contractions in high-K+ (26 mmol/l) Tyrode's solution in the presence of isoproterenol. Our results suggest that low concentrations of bupivacaine depress contraction mainly due to an Na+ channel block, whereas at higher concentration, this local anesthetic may block Ca2+ channels.

Action Potentials↗
PubMed1993

Evaluation of myocardial damage in Duchenne's muscular dystrophy with thallium-201 myocardial SPECT.

Myocardial damage and cardiopulmonary functions in patients with Duchenne's muscular dystrophy (DMD) were assessed using thallium-201 myocardial single-photon emission computed tomography (SPECT) and technetium-99m multigated radionuclide angiography. Twenty-five patients with DMD were divided into 4 groups according to percent of perfusion defect (%PD) calculated by the bull's-eye method and age. PD was detected in 24 (96.0%) of 25 patients with DMD, and it spread from the left ventricular lateral wall to the anterior wall and/or interventricular septum. PD was detected even in a 6-year-old DMD boy. Patients in Group I (%PD > or = 10 and age < 15 years old) were shown to have a higher risk of left-sided heart failure without respiratory failure. Patients in Group II (%PD > or = 10 and age > or = 15) showed decreased pulmonary function and worsened arterial blood gas values as compared with Group IV (%PD < 10 and age > or = 15). There was no significant difference in cardiac function among the 4 groups. It is postulated that myocardial damage in Group II patients is dependent primarily on a deficiency of dystrophin and on chronic respiratory failure, and that some of them are at risk of cardiopulmonary failure. It is concluded that myocardial SPECT is useful for the early diagnosis of myocardial damage and evaluation of cardiopulmonary function in DMD patients.

Child↗
PubMed1993

Mutagenicity of activated carbon adsorbate of drinking water in the Ames assay.

Mutagenicity of activated carbon adsorbate from drinking water collected in Niigata City was assayed by the Ames assay. Adsorbate was extracted from activated carbon with benzene, and then with ethanol. Although the benzene extract was not mutagenic, the ethanol one showed the mutagenic activity for Salmonella typhimurium strains TA98 and TA100 with and without S9 mix. The ethanol extract was much more mutagenic on TA100 than TA98 both with and without S9 mix. The mutagenic activity per liter of water was found to be the strongest in winter and the weakest in summer.

Animals↗
PubMed1993

[Inhibitory action of bupivacaine on cardiac contraction].

We studied the effects of bupivacaine on the contractility and membrane potentials in isolated dog papillary muscle. Bupivacaine (10(-6)-10(-4) M) produced dose-dependent depression of twitch tension elicited by electrical stimulation. These inhibitory effects were greater at high frequencies of stimulation (2, 3 Hz) than at low frequencies (less than 1 Hz). Bupivacaine did not alter the resting membrane potential, but produced a reduction in Vmax of the action potentials, in a dose-dependent and reversible manner (concentrations from 10(-6) to 10(-4) M). Bupivacaine 10(-4) M often blocked the fast action potentials in normal Tyrode's solution. In high K+ (26 mM) Tyrode's solution, bupivacaine inhibited both slow action potentials and associated contractions in the presence of isoproterenol. These results suggest that low concentrations of bupivacaine decreases the contraction mainly due to Na+ channel block, whereas at higher concentration, this anesthetic may block Ca2+ channels. In addition, isoproterenol may be clinically effective in the treatment of bupivacaine cardiotoxicity due to stimulation of Ca2+ mediated slow action potentials through beta-receptors.

Animals↗
PubMed1993

[Effect of sevoflurane on contraction and membrane potentials in canine right ventricular myocytes].

The effects of sevoflurane on contraction and membrane potentials were studied in isolated canine ventricular muscle strips. Sevoflurane depressed electrically-induced contraction in a dose-dependent manner. The inhibitory effect was more pronounced in high-K+ Tyrode solution than in normal Tyrode solution suggesting that sevoflurane inhibits transmembrane Ca2+ influx. In electrophysiological studies, sevoflurane depressed both overshoot and the plateau phase of action potentials. Resting membrane potential was not affected by sevoflurane. We conclude that the depression of myocardial contractility by sevoflurane may be due to block of transmembrane calcium influx.

Action Potentials↗