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Biomedical subjects

S Nishimura

Publications and source records attributed to S Nishimura.

At least 343 records · Page 19Linked to original sources
PubMed1995

Correlation of in vivo infectivity of hepatitis C virus to in vitro infectivity and to virion properties.

Serum from an individual who was chronically infected with hepatitis C virus (HCV) was inoculated into chimpanzees and a human T cell line. The serum contained a quasispecies population of HCV consisting of at least six genetic sequences. However, only two sequences (the same two sequences) were recovered both in chimpanzees and in cultured human T cell line, indicating that infection of the culture system reflects infection in vivo.

Amino Acid Sequence↗
PubMed1994

Antitumor effect of ischemia-reperfusion injury induced by transient embolization.

The effect of ischemia-reperfusion, induced by the transient embolic agent degradable starch microspheres (DSMs) on tumor tissue was investigated from the standpoint of active oxygen species. Rabbits with VX2 carcinoma received regional infusion of DSMs by transcatheter angiography, and it was confirmed that DSMs occluded tumor vessels. Blood flow in the tumors decreased rapidly immediately after the DSM treatment and returned to the original level within 40 min. The size of tumors did not change after a single infusion of DMS, while five repeated DSM treatments led to a significant reduction in tumor size. This reduction in tumor size was prevented by the treatment of rabbits with superoxide dismutase and catalase, indicating that the generation of active oxygen species in the tumor was involved in the mechanism of action of DSMs. Thiobarbituric acid-reactive substances also increased in the tumors after DSM infusion, and this increase was also inhibited by treatment with superoxide dismutase and catalase. In conclusion, the antitumor effect of the transient embolic agent DSM is secondary to the phenomenon of ischemia-reperfusion injury. In addition, active oxygen species and lipid peroxidation are possible causes of ischemia-reperfusion injury.

Animals↗
PubMed1994

Involvement of the brain type of ryanodine receptor in T-cell proliferation.

Cloning and sequence analysis of cDNA showed that the brain type of ryanodine receptor (RYR) is expressed in human Jurkat T-lymphocyte cells. Fura-2 measurements revealed that the RYR in T-cells functions as a ryanodine-sensitive, caffeine-insensitive Ca2+ release channel. Furthermore, ryanodine stimulated proliferation and altered the growth pattern of cultured human T-cells when added together with FK506.

Amino Acid Sequence↗
PubMed1994

Inhibition of growth of human tumor cells in nude mice by a metalloproteinase inhibitor.

The effects of a new metalloproteinase inhibitor, BE16627B [L-N-(N-hydroxy-2-isobutylsuccinynamoyl)-seryl-L-valine, MW: 375.2] isolated from microbial cultures, on human tumor cell growth in nude mice were investigated. BE16627B inhibited metalloproteinases in enzyme assays, as well as gelatinolysis and collagenolysis in cell cultures. BE16627B at 100 micrograms/ml showed no apparent cytotoxicity to human tumor cells in culture and its LD50 in mice was more than 1,000 mg/kg (i.p.). The effects of BE16627B on the in vivo growth of 2 human tumor cell lines were examined: HT1080 fibrosarcoma, which overproduces metalloproteinases, and HCT116 colon carcinoma, which barely secretes metalloproteinases. When BE16627B was administered to mice at 2 mg/mouse/day by an osmotic pump implanted s.c. for 3 weeks from 1 week after i.v. inoculation of HT1080 cells, the number and size of nodules of HT1080 cells on the lung surface were reduced to 24.3 and 46.4%, respectively, of those of controls, and the increase in lung weight due to tumor-cell growth was inhibited 85.5% without body-weight loss. Moreover, BE16627B inhibited 71.2% of the growth of HT1080 cells inoculated s.c. into mice under the same conditions, but did not significantly inhibit the s.c. growth of HCT116 human colon-carcinoma cells. Thus, BE16627B inhibited metalloproteinase-dependent human tumor-cell growth as well as lung colonization without showing cytotoxicity in nude mice.

Animals↗
PubMed1994

Conformational analysis of elcatonin in solution.

The conformational characteristics of elcatonin, an analogue of eel calcitonin having a disulfide bond Cys1-Cys7 replaced by an ethylene linkage between residues 1 and 7, have been analyzed in aqueous trifluoroethanol solutions. Circular dichroic spectra of elcatonin and eel calcitonin itself reveal the presence of alpha-helices at trifluoroethanol concentrations above 15%. The spectral changes caused by the trifluoroethanol content of the solutions are interesting. An isosbetic point is detected for eel calcitonin indicating that a conformational transition occurs between two states, namely alpha-helical and random coil states. On the other hand, the CD curves of elcatonin at less than 15% trifluoroethanol deviate from the isosbetic point while those at higher concentration are similar to those of eCT. This can probably be attributed to the third element of the ordered structure of elcatonin which is formed in 15% trifluoroethanol. The solution conformation of elcatonin in a mixture of 60% water and 40% trifluoroethanol has been determined by the combined use of 1H-NMR spectroscopy and distance geometry calculations. The conformation is characterized by an amphiphilic alpha-helix between Thr6 and Thr21, which extends into the constrained cyclic portion of the molecule to Thr6. The third structural element of elcatonin found in the CD analysis is detected by some turn structures in the region between residue 1 and Ser5 in the calculated structure.

Amino Acid Sequence↗
PubMed1994

Cd2+ and Co2+ at micromolar concentrations stimulate catecholamine secretion by increasing the cytosolic free Ca2+ concentration in cat adrenal chromaffin cells.

Cd2+ and Co2+ at micromolar concentrations increased the cytosolic free Ca2+ concentration, which was measured by fura-2 microfluorometry, in cat adrenal chromaffin cells. Simultaneously, these divalent cations stimulated catecholamine secretion from the perfused adrenal. The present findings suggest that these cations increase the Ca2+ influx by depolarizing the cell membrane and consequently stimulate catecholamine secretion.

Adrenal Medulla↗
PubMed1994

Recognition of UUN codons by two leucine tRNA species from Escherichia coli.

Codon recognition by Escherichia coli tRNA(Leu)4 and tRNA(Leu)5 was investigated by analysis of the competition between two aminoacyl-tRNA species in an in vitro protein synthesis. Both tRNA species strictly obey the wobble rule when they are in competition with other tRNA species. This is probably due to the post-transcriptional modifications at the first position of the anticodon of these tRNA(Leu) species, supporting the proposal that the conformational rigidity of post-transcriptionally modified pyrimidine nucleotides guarantees the correct codon recognition.

Amino Acid Sequence↗
PubMed1994

The specific binding site of the volatile anesthetic diiodomethane to purple membrane by X-ray diffraction.

To determine the binding site of volatile anesthetics on purple membrane, diiodomethane (CH2I2) was used as a label in X-ray diffraction experiments. At less than 3 mM diiodomethane, purple membrane retains its two-dimensional crystallinity of bacteriorhodopsin, absorption spectra show only a little blue shift and the decay time of the M-intermediate becomes fast in flash photolysis experiments. These effects are similar to those of other anesthetics previously studied. The position where the anesthetic binds was identified by difference Fourier methods, and refined by model calculations. This study suggests that volatile anesthetics bind specifically to the protein-lipid interfacial region near the surface of membrane.

Anesthetics↗
PubMed1994

Role of the integrin alpha v beta 6 in cell attachment to fibronectin. Heterologous expression of intact and secreted forms of the receptor.

The integrin alpha v beta 6 has been shown to be a fibronectin-binding protein. To determine whether the cytoplasmic and transmembrane domains of alpha v beta 6 are necessary for binding to fibronectin, a truncated, secreted form of the integrin lacking these domains was engineered and expressed in Chinese hamster ovary cells. Fibronectin affinity chromatography demonstrated that the secreted integrin, like its full-length counterpart, was capable of binding fibronectin. Monoclonal antibodies were made to secreted alpha v beta 6 and to beta 6-transfected NIH 3T3 cells. In experiments designed to determine whether alpha v beta 6 can mediate cell attachment to fibronectin, full-length human beta 6 was expressed in Chinese hamster ovary cells and in the human colon carcinoma cell line SW480. beta 6-expressing cells were identified by alpha v beta 6-specific antibodies, and the beta 6-transfectants were used in cell-adhesion assays. In Chinese hamster ovary cells, human beta 6 associated with hamster alpha v but was incapable of mediating cell attachment to fibronectin. However, expression of beta 6 in these cells had the dominant negative effect of decreasing alpha v beta 5-dependent adhesion to vitronectin. In SW480 cells, beta 6 expression conferred the ability to bind to fibronectin even in the presence of inhibitory antibodies against beta 1 integrins. In such cells, fibronectin binding ability could be blocked by an antibody to alpha v integrins. These results constitute the first direct evidence that alpha v beta 6 mediates cell attachment to fibronectin.

3T3 Cells↗
PubMed1994

Chemoenzymic preparation of a glycoconjugate polymer having a sialyloligosaccharide: Neu5Ac alpha (2-->3)Gal beta (1-->4)GlcNAc.

Water-soluble polyacrylamide having 3'-sialyl N-acetyl-lactosamine [Neu5Ac alpha (2-->3)Gal beta (1-->4)GlcNAc] was enzymatically prepared by stepwise sugar-elongation on a water-soluble GlcNAc-bearing polyacrylamide. It was demonstrated that the flexible GlcNAc branches of the polymer chains allow quantitative galactosylation with bovine galactosyl transferase and partial sialylation by Trypanosoma cruzi trans-sialidase. Unsialylated N-acetyl-lactosamine side chains can be removed with beta-D-galactosidase and N-acetyl-beta-D-glucosaminidase to afford the targeted polymer containing 3'-sialyl N-acetyl-lactosamine.

Acetylgalactosamine↗
PubMed1994

Site-directed mutagenesis, fluorescence, and two-dimensional NMR studies on microenvironments of effector region aromatic residues of human c-Ha-Ras protein.

The Tyr residues in positions 32 and 40 of human c-Ha-Ras protein were replaced by site-directed mutagenesis (Y32F, Y32W, Y40K, and Y40W) to examine their roles in the signal-transducing activity and the sensitivity to the GTPase activating protein (GAP). The signal-transducing activity of the oncogenic Ras protein in PC12 cells was lost upon mutations Y32F and Y40K, but retained upon mutations Y32W and Y40W. These results suggest that residues 32 and 40 are both required to have aromatic groups and residue 32 is further required to have a hydrogen donor. On the other hand, three mutations (Y32F, Y32W, and Y40W) caused no appreciable reduction in either GAP-binding affinity or GAP sensitivity. By the Y40K mutation, GAP-binding affinity was slightly lowered, while GAP sensitivity was drastically impaired. Therefore, for residues 32 and 40 of Ras, interactions with GAP appear to be different from those with the target of signal transduction in the PC12 cell. As for the Y32W-Ras protein bound with an unhydrolyzable GTP analogue (GMPPNP), the Trp32 fluorescence is appreciably red-shifted, weaker, and more susceptible to KI quenching as compared to that of the GDP-bound form. Two-dimensional NMR spectroscopy with selectively deuterated Ras proteins revealed fewer and weaker nuclear Overhauser effects on the aromatic protons of Trp32 in the GMPPNP-bound form than in the GDP-bound form. This indicates that the side chain of Trp32 is more exposed to the solvent in the GMPPNP-bound form than in the GDP-bound form.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1994

Serotyping of human rotaviruses in the Tokyo area (1990-1993) by enzyme immunoassay with monoclonal antibodies and by reverse transcription and polymerase chain reaction amplification.

Serotyping of human rotavirus in the Tokyo area was conducted from 1990 to 1993 by enzyme immunoassay with monoclonal antibodies (EIA-MAbs) against VP7 and by reverse transcription and polymerase chain reaction (RT-PCR) amplification of the VP4 and VP7 genes. The results by EIA-MAbs were very similar to those obtained by RT-PCR. Evidence of intraserotypic variations was suggested because strains of undetermined serotypes were detected by either EIA-MAb or RT-PCR. This kind of study is required for vaccine development.

Antibodies, Monoclonal↗
PubMed1994

Chromosome 1q terminal deletion resulting from de novo translocation with an acrocentric chromosome.

Distal deletion of chromosome 1q has been reported in nearly 30 patients, all being associated with a deletion ranging from the 1q42 or q43 band to 1qter region. Here, we describe a girl with 1q terminal deletion resulting from an unbalanced de novo translocation t(1;D or G)(q44;p11), as revealed by the presence of a satellited feature and an NOR-stained region at the tip of 1q. We suggest that most of the phenotypic abnormalities seen in patients with 1q distal deletion are attributable to the monosomy for band 1q44.

Child, Preschool↗
PubMed1994

Noninvasive identification of anthracycline cardiotoxicity: comparison of 123I-MIBG and 123I-BMIPP imaging.

To test the feasibility of myocardial 123I-MIBG and 123I-BMIPP imaging for the early detection of anthracycline cardiotoxicity, 13 patients who had received anthracycline anticancer chemotherapeutic agents were studied. Two-dimensional echocardiography and myocardial imaging with both 123I-MIBG and 123I-BMIPP were performed in 13 patients treated with anthracycline (group A) and 10 normal control subjects (group C). Anterior myocardial images were obtained 15 minutes and 3 hours after the injection of isotopes. The heart-to-mediastinum ratio (H/M ratio) was used to quantify cardiac 123I-MIBG and 123I-BMIPP uptake. The left ventricular shortening fraction (%SF) and the ratio of peak mitral flow velocity in early diastole to that at the time of atrial systole (E/A ratio) were measured by echocardiography. The H/M ratio of 123I-MIBG was lower in group A than in group C (1.5 +/- 0.2 vs. 1.9 +/- 0.2, p < 0.01). The patients in group A had faster clearance of 123I-MIBG from the myocardium than those in group C (27 +/- 10% vs. 22 +/- 4%, p < 0.05). However, the H/M ratio and clearance of 123I-BMIPP were similar between the two groups (H/M ratio: 2.1 +/- 0.2 vs. 2.0 +/- 0.2, clearance: 24 +/- 6% vs. 26 +/- 6%). The %SF (37 +/- 8% vs. 36 +/- 7%) and E/A ratio (1.4 +/- 0.4 vs. 1.6 +/- 0.3) were comparable in groups A and C. The present findings indicated that myocardial imaging with 123I-MIBG could detect myocardial damage in patients treated with anthracycline in the early stage when cardiac systolic and diastolic function was still preserved. Early detection of anthracycline cardiotoxicity by 123I-MIBG would reduce the incidence and severity of heart failure.

3-Iodobenzylguanidine↗
PubMed1994

Biosynthesis of a novel polysaccharide by Acetobacter xylinum.

An Acetobacter xylinum adapted to a medium containing N-acetylglucosamine (GlcNAc) has been used to prepare a novel polysaccharide containing residual GlcNAc in cellulose. The maximum amount of incorporation was found to be 4 mol% in cellulose, when a mixed medium containing 1.4% glucose (Glc) and 0.6% GlcNAc was used for the culture of A. xylinum. The resulting polysaccharide was lysozyme-susceptible. The aminosugar residue incorporated into bacterial cellulose was found to be only GlcNAc, even if galactosamine (GalN) and glucosamine (GlcN) were applied, whereas there was little effect by mannosamine (ManN). As the major component of the resulting polysaccharide was Glc residues, even if the only carbon source in the culture medium was GlcNAc, it was suggested that there must be several enzyme systems to convert GlcNAc into Glc in the bacteria. Several ammonium salts were also found to be effective for the incorporation of GlcNAc residues when the incubation system was converted to rotatory and aerobic incubation from static incubation. The amount of residual GlcNAc was remarkably increased by the addition of lysozyme-susceptible phosphoryl-chitin (P-chitin) and increased slightly with addition of P-chitin that was less lysozyme-susceptible. However, little effect was found on addition of highly substituted P-chitin.

Acetylglucosamine↗