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Biomedical subjects

T Uda

Publications and source records attributed to T Uda.

At least 19 recordsLinked to original sources
PubMed2003

Dopant-pair structures segregated on a hydrogen-terminated Si(100) surface.

Novel atomic structures on a H-terminated Si(100)-(2x1)-H surface were found using scanning tunneling microscopy (STM). The structures are distinguishable only from Si dimers in empty-state STM images. They were observed on arsenic- and phosphorus-doped substrates, but not on boron-doped substrates. Surface density of these structures was found to be proportional to the dopant density in the substrate. First-principles calculations clarify that they are consisting of dopant pairs that are segregated from the bulk material. Hydrogen atoms attached to the dopant pair are found to flip between two positions on the surface due to a quantum effect.

Journal Article↗
PubMed2001

Atomic wire oxidation of H-terminated Si(100)-( 2x1): domino reaction via oxidation and H migration.

We studied oxidation at a dangling bond (DB) on the H-terminated Si(100) surface by the first-principles calculations. We found that oxidation easily occurs at the exposed DB on the H-terminated Si(100) surface. The dissociated O atoms are chemisorbed at a dimer bond and a back bond, resulting in adjacent H atom migration onto the DB. As a consequence of the alternate oxidation and subsequent H atom migration processes, the atomic wire oxidation is actually found to occur on the H-terminated Si(100) surface at low temperatures without desorbing H atoms, as observed in our scanning tunneling microscopy experiment.

Journal Article↗
PubMed2000

Technique for enhanced rare earth separation

A process is demonstrated for the efficient separation of rare earth elements, using a combination of selective reduction and vacuum distillation of halides. The large differences in the redox chemistry of the rare earth elements and in the vapor pressures of rare earth di- and trihalides are exploited for separation. Experimental proof of concept is provided for the binary systems praseodymium-neodymium and neodymium-samarium. This process enhances the separation factor for the isolation of samarium and neodymium from their mixture by more than an order of magnitude.

Journal Article↗
PubMed2000

Atomic and electronic origins of a type- C defect on Si(001)

We present an extensive set of ab initio calculations for a type- C defect on Si(001). Various models belonging to subsurface defects are studied. A substitutional B in the second surface layer is predicted as a possible atomic origin of this defect. However, H and O coupled with second-layer vacancies and a substitutional C are not responsible for a type- C defect. We also discuss how the electronic structure of a type- C defect contributes to its specific scanning tunneling microscopy images.

Journal Article↗
PubMed2000

Analysis of the antigen recognition sites of anti-methamphetamine monoclonal antibodies (II): unique feature of MA-3 antibody.

A monoclonal antibody against methamphetamine (MA-3 mAb) was found to be strongly bound to ephedrine. This feature was quite different from that of other fourteen mAbs against MA. Analyses of cDNA sequence and steric conformation by molecular modeling revealed that one hydrophilic pocket was generated in the heavy chain of MA-3 mAb involving CDRH-1 and CDRH-2. Asn33, Asn35, Asn50 and Asp52 were the main components of the unique pocket capable of binding to the hydroxyl group of ephedrine.

Journal Article↗
PubMed2000

Removal of catalytic activity by EDTA from antibody light chain.

Gp41 peptide antigen of the HIV-1 envelope (TP41-1:TPRGPDRPEGIEEEGGERDR, a highly conserved region) was enzymatically degraded by the antibody light chain 41S-2-L after an induction period. The peptide bond between Glu14 and Gly15 was cleaved early in the reaction. When EDTA was added in the induction period, it inhibited the degradation of TP41-1 thus ceasing the catalytic activity of 41S-2-L. In contrast, when EDTA was added after the induction period, only a small reduction in the catalytic activity was observed. These observations suggest that metal ions are important in stimulating catalytic activity early in the reaction.

Amino Acid Sequence↗
PubMed1999

Cloning, sequencing, and characterization of ribosomal protein and RNA polymerase genes from the region analogous to the alpha-operon of escherichia coli in halophilic archaea, halobacterium halobium.

A determination was made of the nucleotide sequence of the 3215-bp region of a ribosomal protein gene cluster (HS13, HS4, HS11, and HeL18), RNA polymerase (RNA poly D), and tRNA genes (tRNAser and tRNAarg) of halophilic Archaea Halobacterium halobium, which is analogous to the alpha-operon of Escherichia coli (tRNAser-HS13-HS4-HS11-RNA poly D-tRNAarg-HeL18). The seven-gene string was preceded by a pseudoknot-like structure similar to the proposed S4 ribosomal protein binding site of the alpha-operon mRNA leader in E. coli. Using an inducible expression system H. halobium HS4 was produced in large amounts in E. coli, and immunoblot analysis showed the S4 to constitute a 21-kDa polypeptide component of the ribosome. Analysis of the deduced amino acids sequence revealed that the HS13, HS4, and HS11 sequences including the RNA polymerase subunit are more similar to their eukaryotic than to their bacterial counterparts. HeL18, located downstream of the gene cluster analogous to the E. coli alpha-operon (S13-S11-S4-RNA poly D-L17), was similar to both the eukaryotic (eL18) and eubacterial ribosomal protein L15 located in the spc-operon, but not to L17 positioned as the terminal gene of the bacterial alpha-operon.

Amino Acid Sequence↗
PubMed1999

Superoxide dismutase in normal cycling human ovaries: immunohistochemical localization and characterization.

OBJECTIVE: To investigate the expression of manganese (Mn) and copper-zinc (Cu,Zn) superoxide dismutase (SOD) in normal cycling human ovaries throughout the menstrual cycle. DESIGN: Descriptive, controlled study. SETTING: Tohoku University School of Medicine. PATIENT(S): Twenty-four normal cycling human ovaries were obtained from patients who underwent oophorectomy and hysterectomy for squamous cell carcinoma of the uterine cervix. INTERVENTION(S): Immunohistochemistry for Mn-SOD and Cu,Zn-SOD. MAIN OUTCOME MEASURE(S): Immunostaining. RESULT(S): In the follicular stage, Mn-SOD immunoreactivity was detected in granulosa and theca interna cells of steroid-producing follicles, that is, preantral, nondominant, dominant, and atretic follicles, whereas Cu,Zn-SOD was detected in theca interna cells of these follicles and in granulosa cells of dominant follicles. In the luteal stage, immunoreactivity for Mn-SOD and Cu,Zn-SOD was observed in both luteinized granulosa and theca cells of the functioning corpus luteum. In the early degenerating corpus luteum, both Mn-SOD and Cu,Zn-SOD were positive in steroid-producing luteinized theca cells. Mn-SOD immunoreactivity was also detected in nonsteroid-producing luteinized granulosa cells and macrophages. CONCLUSION(S): Our results suggest that the expression of Mn-SOD and Cu,Zn-SOD closely correlates with steroidogenesis in the human ovary. In addition, Mn-SOD may play an important role in the process of luteal regression.

Adult↗
PubMed1999

Super catalytic antibody [I]: decomposition of targeted protein by its antibody light chain.

Obtaining an antibody capable of destroying a targeted protein is the eventual goal in developing superior catalytic antibody. We established a monoclonal antibody recognizing a highly conserved sequence, RGPDRPEGIEEEGGERDRD, of gp41 of the HIV-1 envelope. The obtained antibody reacted with gp41 and gp160 of HIV-1. The isolated and purified light chain not only decomposed the above antigenic peptide but also destroyed the gp41 molecule, indicating a novel ability. The decomposition of the antigen is presumably started by scission of the peptide bond between Arg-Gly in the above sequence. The light chain did not decompose BSA and HSA at all, showing the high specificity to antigens. The antibody light chain is referred to as a super catalytic antibody.

Journal Article↗
PubMed1998

Design of novel porphyrin-binding peptides based on antibody CDR.

Novel porphyrin-binding peptides were designed on the basis of an antigen binding site of an antiheme monoclonal antibody. Synthetic peptides were modified with a pyrene moiety. The spectroscopic measurements revealed that the synthetic peptides bound a porphyrin effectively.

Amino Acid Sequence↗
PubMed1996

Changes in activity of superoxide dismutase in the human endometrium throughout the menstrual cycle and in early pregnancy.

To investigate the possible role of the superoxide radical and its scavenging system in the human endometrium, the immunohistochemical distribution of superoxide dismutase (SOD), activities of SOD and lipid peroxide concentrations were studied in the human endometrium throughout the menstrual cycle and in early pregnancy. The endometrial epithelium showed a positive immunostaining for Cu, Zn-SOD and Mn-SOD throughout the entire menstrual cycle and in early pregnancy. In the stroma, weak immunostaining for Cu,Zn-SOD and moderate immunostaining for Mn-SOD were observed in the predecidual cells in the late secretory phase. Decidual cells in early pregnancy showed strong immunostaining for Cu,Zn-SOD and Mn-SOD. Total SOD activity in the endometrium increased from early proliferative phase to mid-late proliferative phase and further increased in the mid-secretory phase, and decreased in the late secretory phase. The total SOD activity in the endometrium of of early pregnancy was the same level as that in the mid-secretory phase. Cu,Zn-SOD and Mn-SOD activities changed in a similar manner to total SOD activity throughout the menstrual cycle and in early pregnancy. Lipid peroxide concentration in the endometrium increased from early proliferative phase to mid-late proliferative phase and further increased in the late secretory phase. However, lipid peroxide concentration in the endometrium of early pregnancy was the same as that in the mid-secretory phase. These results suggested that the superoxide radical and its scavenging system may play an important role in the regulation of human endometrial function.

Adult↗
PubMed1995

An approach for an immunoaffinity AIDS sensor using the conservative region of the HIV envelope protein (gp41) and its monoclonal antibody.

A monoclonal antibody for the conservative region of gp41, which is one of the HIV envelope proteins, was produced. The antigen determining site of gp41 was examined using the epitope mapping technique, followed by an enzyme linked immunosorbent assay. Some peptides had comparable affinities for the monoclonal antibody, but the peptide EGIEE, having a slightly weaker immunoaffinity than gp41, was the most preferable for the construction of an immunoaffinity AIDS sensor. For the detection of gp41, EGIEE was labelled with catalase and used as a mimic antigen; it was bound to the antibody present on an immuno-membrane and, due to the replacement reaction of the mimic antigen by gp41, indirect quantitative measurement of gp41 was possible using an oxygen electrode. Anti-gp41 antibody was also detected using a mimic antibody, which was chemically modified with polyethylene glycol. An immunoaffinity AIDS sensor was constructed using the mimic molecules which were tailored to have a suitable immunoaffinity for HIV antigen and/or antibody.

Acquired Immunodeficiency Syndrome↗
PubMed1995

Effects of zinc on production of active oxygen species by rat neutrophils.

The effects of zinc on the production of active oxygen species were investigated in rat neutrophils by chemiluminescence and spectrophotometric assays. The luminol-dependent chemiluminescence in unstimulated neutrophils showed a single peak. Zinc at concentrations lower than 0.1 mM augmented the intensity of chemiluminescence and showed a bimodal pattern, the first peak of which was inhibited by superoxide dismutase and catalase, while the second peak disappeared in the presence of catalase, but was unaffected by superoxide dismutase. At the same concentrations of zinc, O2- and H2O2 production increased, but secretion and activity of myeloperoxidase were not affected. Zinc at 0.1 mM enhanced the second peak of luminol-dependent chemiluminescence, and concomitantly O2- and H2O2 production of neutrophils stimulated with formyl-methionyl-leucyl-phenylalanine. Homogenized neutrophils showed a bimodal pattern on induction by zinc, the second peak of which was inhibited slightly by catalase and completely by sodium azide, but was not inhibited by superoxide dismutase. Zinc-induced O2- production was inhibited by pertussis toxin, but was not significantly inhibited by a protein kinase C inhibitor, 1-(5-isoquinolinesulfonyl)-2-methylpiperazine dihydrochloride (H-7), or a calmodulin antagonist, N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide (W-7). These results suggest that zinc can augment luminol-dependent chemiluminescence by increasing O2- production through the classical signal transduction pathway, and by increasing H2O2 not via O2-.

Animals↗
PubMed1994

Application of polymer-protected ultrafine platinum particles to the immunological detection of human serum albumin.

The immunological properties of ultrafine platinum particles protected with poly(methyl acrylate)-co-N-vinyl-2-pyrrolidone, having a group chemically reactive with protein, were examined. Polymer-protected ultrafine particles were able to chemically bond multiple human serum albumin (HSA) molecules on their surface. The particles behaved as a multi-epitope-type antigen for the immunoreaction. In an ELISA, the HSA-bound particles and HSA molecules competitively reacted against the anti-HSA monoclonal antibodies. The limit of detection of HSA was ca. 10 ng/ml in the assay. The particles were used in an immunodot analysis of anti-HSA polyclonal antibody. Within 30 min of the reaction, 1-10 micrograms/ml of HSA was detected. The protein fixed polymer-protected ultrafine particles are a useful new material in immunochemistry.

Animals↗