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T Yamazaki

Publications and source records attributed to T Yamazaki.

At least 163 records · Page 9Linked to original sources
PubMed2000

Structure of the heterodimeric complex between CAD domains of CAD and ICAD.

We present here the structure of the complex between the CAD domain of caspase activated deoxyribonuclease (CAD) and the CAD domain of its inhibitor (ICAD), determined by nuclear magnetic resonance spectroscopy. The two domains adopt a very similar fold, which consists of an alpha-helix and a beta-sheet, and are aligned side by side in the complex. Notably, the positive charges on the strand beta2 at one end of the beta-sheet of CAD and negative charges around the opposite end of the beta-sheet of ICAD are paired in the complex. Point mutations of the charged amino acids at this interface, on either CAD or ICAD, prevented formation of the functional CAD-ICAD complex. This implies that the interaction between the CAD domains of CAD and ICAD is an essential step in the correct folding of CAD in the complex.

Amino Acid Sequence↗
PubMed2000

Tyramine-induced endogenous noradrenaline efflux from in situ cardiac sympathetic nerve ending in cats.

With the use of dialysis technique, the effects of tyramine on in situ cardiac sympathetic nerve endings were examined in anaesthetized cats. Dialysis probes were implanted in the left ventricular myocardium, and the concentration of dialysate noradrenaline (NA) served as an indicator of NA output at the cardiac sympathetic nerve ending. Locally applied tyramine (600 microM) increased dialysate NA levels from 17 +/- 1 (pg mL-1) to 3466 +/- 209 (pg mL-1). Pretreatment with reserpine (vesicle transport NA blocker 1 microM) did not affect tyramine-induced NA efflux. The tyramine-induced NA efflux was augmented by pretreatment with pargyline (1 mM) but suppressed by pargyline (10 mM). Pretreatment with alpha-methyl-tyrosine suppressed NA efflux evoked by tyramine. These pretreatments did not affect the time course of NA efflux but only altered peak height of NA efflux. The efflux of NA evoked by tyramine was not associated with any reduction of dihydroxyphenylglycol (DHPG). In contrast, in the pretreatment with reserpine, the efflux of NA was associated with a reduction of DHPG. This result suggests that NA graduation between axoplasm and stored vesicle contributes to maintaining the axoplasmic NA level during carrier-mediated outward NA transport. The tyramine-induced NA efflux provides a close reflection of the NA content at the nerve ending. With the use of dialysis, this experimental model is suitable for studying the mechanism of sympathomimetic amine-induced neurotransmitter efflux.

Animals↗
PubMed2000

MBD2-MBD3 complex binds to hemi-methylated DNA and forms a complex containing DNMT1 at the replication foci in late S phase.

BACKGROUND: In vertebrates and plants, DNA methylation is one of the major mechanisms regulating gene expression. Recently, a family of methyl-CpG-binding proteins has been identified, and some members, such as MeCP2 and MBD2, were shown to mediate gene repression by recruiting histone deacetylase complexes to methylated genes. However, the function of another member of this family, MBD3, remained elusive. RESULTS: It was shown that MBD2 and MBD3 form homo- and hetero-dimers (or multimers) in vitro and in vivo. Significantly, the MBD2-MBD3 complex showed an affinity to hemi-methylated DNAs, a property that has never been reported with any member of the family proteins. MBD2 and MBD3 were co-localized with DNMT1 at replication foci in 293 cell nuclei at late S phase. Moreover, by a co-immunoprecipitation experiment, DNMT1 was shown to form a complex with MBD2 and MBD3. Finally, the abundance of MBD3 was highest in the late S phase when the DNMT1 is also most abundant, whereas the MBD2 level was largely constant throughout the cell cycle. CONCLUSIONS: The results suggest that MBD3 may play an important role in the S phase. We hypothesize that the MBD2-MBD3 complex recognizes hemi-methylated DNA concurrent with DNA replication and recruits histone deacetylase complexes, as well as DNMT1, to establish and/or maintain the transcriptionally repressed chromatin.

Chromatin↗
PubMed2000

A new adaptive temporal filter: application to photosensitive seizure patients.

A new adaptive temporal filtering (ATF) technique was developed to prevent heath hazards due to flicker stimuli from televisions, videos or other displays. This ATF method could reduce frame-to-frame or field-to-field flicker stimuli at around 10-30 Hz which are particularly risky for photosensitive individuals. The present ATF efficacy with a computer simulation was studied in 11 photosensitive epilepsy patients. In order to control visual stimuli and induce photoparoxysmal response (PPR), we employed a problematic scene of the Pocket Monster incident containing 12 Hz red/blue flicker images lasting for 4 s. This image, shown with a 14-inch, television set 2 m in front of subjects, promptly elicited generalized PPR in all cases, while the filtered image did not induce any PPR. These results suggest that the present ATF method may be useful as a preventive measure of photosensitive seizures triggered by stimulative images from televisions or other displays.

Adolescent↗
PubMed2000

Structural study of the N-terminal domain of the alpha subunit of Escherichia coli RNA polymerase solubilized with non-denaturing detergents.

The amino-terminal domain of the alpha subunit (alphaNTD) of Escherichia coli RNA polymerase consisting of 235 amino acid residues functions in the assembly of the alpha, beta, and beta' subunits into the core-enzyme. It has a tendency to form aggregates by itself at higher concentrations. For NMR structural analysis of alphaNTD, the solution conditions, including the use of non-denaturing detergents, were optimized by monitoring the translational diffusion coefficients using the field gradient NMR technique. Under the optimal conditions with taurodeoxycholate and with the aid of deuteration of the sample, alphaNTD gave triple-resonance spectra of good quality, which allowed the assignment of a large part of the backbone resonances. Analysis of the pattern of NOEs observed between the backbone amide and alpha-protons demonstrated that alphaNTD has three alpha-helices and two beta-sheets. Although the secondary structure elements essentially coincide with those in the crystal structure, the larger of the two beta-sheets has two additional beta-strands. The irregular NOE patterns observed for the three positions in the beta-sheets suggest the presence of beta-bulge structures. The positions of the three helices coincide with the conserved sequence regions that are responsible for the subunit assembly.

DNA-Directed RNA Polymerases↗
PubMed2000

A new method for dynamical HOLZ calculations

An exact scheme for dynamical HOLZ calculations has been developed with a matrix formula based on the modified Bethe's theory and current flow without the small angle approximation. The HOLZ intensity must be calculated with the current flow for electron beams. For a quantitative intensity calculation at large illumination, not only the current flow in diffracted beams from an exit surface but also the current flow in a primary beam plays an important role.

Journal Article↗
PubMed2000

Simulation of atomic-scale high-angle annular dark field scanning transmission electron microscopy images.

Image simulations for high-angle annular dark field (HAADF) scanning transmission electron microscopy (STEM) based on the Bethe's eigen-value method are presented. The effects of aperture size and defocus of a probe-forming lens, both of which determine the shape of the probe, and the effect of the distortion, influencing the Bloch wave field on atomic columns channelled by electrons, on the HAADF-image intensity are discussed in terms of dynamical effect. These effects are illustrated by our experimental atomic-scale HAADF-STEM images, detected in a detector range of 50-110 mrad. It is emphasized that the image simulations are indispensable for quantification of experimental HAADF-STEM images and as such provide a valuable compositional analysis for every atomic column along the incident beam.

Journal Article↗
PubMed2000

Evolution of nucleotide substitutions and gene regulation in the amylase multigenes in Drosophila kikkawai and its sibling species.

In order to determine evolutionary changes in gene regulation and the nucleotide substitution pattern in a multigene family, the amylase multigenes were characterized in Drosophila kikkawai and its sibling species. The nucleotide substitution pattern was investigated. Drosophila kikkawai has four amylase genes. The Amy1 and Amy2 genes are a head-to-head duplication in the middle of the B arm of the second chromosome, while the Amy3 and Amy4 genes are a tail-to-tail duplication near the centromere of the same chromosome. In the sibling species of D. kikkawai (Drosophila bocki, Drosophila leontia, and Drosophila lini), sequencing of the Amy1, Amy2, Amy3, and Amy4 genes revealed that the Amy1 and Amy2 gene group diverged from Amy3 and Amy4 after duplication. In the Amy1 and Amy2 genes, the divergent evolution occurred in the flanking regions; in contrast, the coding regions have evolved in concerted fashion. The electrophoretic pattern of AMY isozymes was also examined. In D. kikkawai and its siblings, two or three electrophoretically different isozymes are encoded by the Amy1 and Amy2 genes (S isozyme) and by the Amy3 and Amy4 genes (F (M) isozymes). The S and F (M) isozymes show different patterns of band intensity when larvae and flies were fed in different media. Amy1 and Amy2, which encode the S isozyme, are more strikingly regulated than Amy3 and Amy4, which encode the F (M) isozyme. The GC content and codon usage bias were higher for the Amy1 and Amy2 genes than for the Amy3 and Amy4 genes. Although the ratio of synonymous and replacement substitutions within the Amy1 and Amy2 gene group was not significantly different from that within the Amy3 and Amy4 gene group, the synonymous substitution rate in the lineage of Amy1 and Amy2 was lower than that of Amy3 and Amy4. In conclusion, after the first duplication but before speciation of four species, the synonymous substitution rate between the two lineages and the electrophoretic pattern of the isozymes encoded by them changed, although we do not know whether there was any evolutionary relationship between the two.

Amino Acid Substitution↗
PubMed2000

Epithelioid trophoblastic tumor metastatic to the vagina: an immunohistochemical and ultrastructural study.

We describe an epithelioid trophoblastic tumor (ETT) metastatic to the vagina in a 30-year-old Japanese woman. A polypoid tumor in the vaginal orifice was composed of nests of intermediate trophoblastic cells that showed a striking epithelioid appearance. In the hysterectomy specimen, a tumor infiltrated through the myometrium and showed histologic findings similar to those of the vaginal tumor. The tumor cells were positive for cytokeratin, inhibin-alpha, and melanoma cell adhesion molecule (Mel-CAM, CD146) but were only focally positive for human placental lactogen. Electron microscopic examination revealed bundles of well-developed, intermediate-type filaments surrounding the nuclei.

Adult↗
PubMed2000

Chronic adriamycin treatment impairs myocardial interstitial neuronal release of norepinephrine and epinephrine.

Although chronic adriamycin (doxorubicin) treatment is known to induce cardiomyopathic heart failure with sympathetic neurohumoral activation in a dose-dependent manner, its effect on local neuronal catecholamine release at the cardiac sympathetic nerve terminals remains to be clearly determined. Using a cardiac microdialysis technique, we measured dialysate norepinephrine (NE) and epinephrine (Epi) concentrations as indices of myocardial interstitial NE and Epi levels. respectively, in rabbits with chronic adriamycin treatment (ADR) (4 mg/kg/week, 6 weeks, n = 8) and in control rabbits (CNT) (n = 6). Exocytotic release was evoked by the local administration of KCl (100 mM) through the dialysis probe. Basal levels of NE and Epi did not differ between the ADR and CNT groups (NE, 11.6 +/- 6.6 vs. 20.4 +/- 17.2 pg/ml; Epi, 4.0 +/- 0.1 vs. 4.6 +/- 1.7 pg/ml: mean +/- SD). The exocytotic release was suppressed in the ADR compared with the CNT group (NE, 191.4 +/- 144.7 vs. 760.5 +/- 337.8 pg/ml; p < 0.05: Epi, 4.2 +/- 0.4 vs. 20.8 +/- 9.9 pg/ml; p < 0.05). We conclude that chronic adriamycin treatment impairs the neuronal exocytotic release of catecholamine at the cardiac sympathetic nerve terminals.

Animals↗
PubMed2000

A simple and rapid method for purifying staphylococcal exfoliative toxin A.

A rapid and efficient method of purification of staphylococcal exfoliative toxin A, the causative agent of staphylococcal scalded skin syndrome (SSSS), has been developed. It is based on ammonium sulfate precipitation of the culture supernatant and hydrophobic interaction chromatography on Phenyl-Sepharose CL-4B. This procedure results in 87-fold purification of this toxin, which appears as a single band in sodium dodecyl sulfate-polyacrylamide gels.

Ammonium Sulfate↗
PubMed2000

Structure-activity relationship of a novel group of mammalian DNA polymerase inhibitors, synthetic sulfoquinovosylacylglycerols.

We reported previously that sulfolipids in the sulfoquinovosylacylglycerol class from a fern and an alga are potent inhibitors of DNA polymerase alpha and beta and potent anti-neoplastic agents. In developing a procedure for chemical synthesis of sulfolipids, we synthesized many derivatives and stereoisomers of sulfoquinovosylmonoacylglycerol (SQMG) / sulfoquinovosyldiacylglycerol (SQDG). Some of these molecules were stronger inhibitors than the SQMG / SQDG originally reported as natural compounds. In this study, we examined the structure-inhibitory function relationship of synthetic SQMG / SQDG and its relationship to cytotoxic activity. The inhibitory effect is probably mainly dependent on the fatty acid effect, which we reported previously, although each of the SQMG / SQDG was a much stronger inhibitor than the fatty acid alone that was present in the SQMG / SQDG. The inhibitory effect could be influenced by the chain size of fatty acids in the SQMG / SQDG. The sulfate moiety in the quinovose was also important for the inhibition. Lineweaver-Burk plots of SQMG / SQDG indicated that DNA polymerase alpha was non-competitively inhibited, but the SQMG / SQDG were effective as antagonists of both template-primer DNA-binding and nucleotide substrate-binding of DNA polymerase beta. The SQMG had an cytotoxic effect, but the SQDG tested did not. The SQDG might not be able to penetrate into cells. Based on these results, we discuss the molecular action of SQMG / SQDG and propose drug design strategies for developing new anti-neoplastic agents.

Antineoplastic Agents↗
PubMed2000

Effect of age on the relationship between gastric cancer and Helicobacter pylori. Tokyo Research Group of Prevention for Gastric Cancer.

Helicobacter pylori is thought to be involved in the pathogenesis of gastric cancer, but the time point at which it produces its effects (critical time) is unknown. We measured the serum level of H. pylori antibody in 787 gastric cancer patients and 1007 controls aged 20 to 69. Odds ratios for different gastric cancer types and stages were determined for each 10-year age class. The overall odds ratio for gastric cancer decreased with age, being 7.0 for those aged 20 - 29, 14.5 for those aged 30 - 39, 9.1 for those aged 40 - 49, 3.5 for those aged 50 - 59, and 1.5 for those aged 60 - 69 (trend in odds ratios: P < 0.01). However, there was no such age-dependent trend for early diffuse-type cancer; the odds ratios were 12.6, 4.0, 7.2, 6.5, and 18.5 respectively (P = 0.29). Early cancer tended to show higher seroprevalence than advanced cancer, especially in older subjects. No significant difference in seroprevalence was observed between diffuse and intestinal cancers within each age-class. Seroreversion must have occurred in the time interval between the critical time and the diagnosis of the cancer, especially in older patients. The age-dependent relationship between H. pylori and gastric cancer may be due to seroreversion, which itself may be independent of age. This age-independence indicates that prolonged exposure to H. pylori does not increase the magnitude of its influence on gastric carcinogenesis. Possible mechanisms through which H. pylori exerts pathogenic effects are continuous inflammation in adulthood and / or irreversible damage to gastric mucosa in childhood or the teenage years.

Adult↗
PubMed2000

Prevention of metastasis by a polyamine synthesis inhibitor in an animal bone metastasis model.

In order to better understand the development of skeletal metastases, we developed an appropriate animal model, as the natural progression of metastases in humans cannot be studied on the cellular level. In this study, we established a new animal model which developed bone metastasis in a bone grafted subcutaneously. C57BL/6 mice, which had received a bone (femur or tibia) transplanted in the dorsal subcutis, were injected with B16 melanoma cells into the left heart ventricle. Metastasis was found in approximately 70% of the extraskeletal bones. Using this model, the antimetastatic effect of a polyamine synthesis inhibitor was investigated. Inhibitors of the polyamine biosynthetic pathway have received considerable attention for their potential use in the treatment of cancer as they are responsible for the greatly increased production of the polyamines putrescine, spermidine, and spermine. A polyamine synthesis inhibitor, methylglyoxal-bis(cyclopentylamidinohydrazone) MGBCP, was investigated for its inhibitory effects on bone metastases. MGBCP (20 mg/kg) was administered intraperitoneally every day for 4 weeks and demonstrated strong inhibitory effects on bone metastases. MGBCP inhibited angiogenesis in the transplanted bone and the growth of B16 melanoma cells, thus suggesting a preventive mechanism in bone metastasis. No remarkable adverse effects of MGBCP were observed in any animal throughout the experimental period. Our results indicate that MGBCP has a strong potential for use as an anti-metastatic drug.

Animals↗
PubMed2000

NMR structure of ribonuclease HI from Escherichia coli.

The solution structure of ribonuclease HI (RNase HI) from Escherichia coli (E. coli), a protein of 155 residues, was determined. Three-dimensional nuclear Overhauser enhancement spectroscopy (NOESY) was used to obtain 1,424 distance constraints between individually assigned polypeptide chain hydrogen atoms. Supplemental geometric constraints of 90phi angles and 12chi1 angles, and the distance constraints of 66 hydrogen bonds were experimentally derived. Using the DADAS90 program that calculates structures in dihedral angle space, 15 structures satisfying almost all constraints were obtained. The average root mean square deviation (RMSD) from the mean structure was 0.75 A for backbone atoms. The RMSD for backbone atoms between the representative NMR structure with the smallest constraint violation and crystal structures was within 1.2 A. Although the NMR and crystal structures thus resemble one another, a significant discrepancy was observed in a region termed 'basic protrusion.' The discrepancy observed in NMR experiments is explained by fluctuation in this region.

Amino Acid Sequence↗