Search PubMed⌕ Search

Biomedical subjects

N Takeuchi

Publications and source records attributed to N Takeuchi.

At least 19 recordsLinked to original sources
PubMed2000

Characterization and tRNA recognition of mammalian mitochondrial seryl-tRNA synthetase.

Animal mitochondrial protein synthesis systems contain two serine tRNAs (tRNAs(Ser)) corresponding to the codons AGY and UCN, each possessing an unusual secondary structure; the former lacks the entire D arm, and the latter has a slightly different cloverleaf structure. To elucidate whether these two tRNAs(Ser) can be recognized by the single animal mitochondrial seryl-tRNA synthetase (mt SerRS), we purified mt SerRS from bovine liver 2400-fold and showed that it can aminoacylate both of them. Specific interaction between mt SerRS and either of the tRNAs(Ser) was also observed in a gel retardation assay. cDNA cloning of bovine mt SerRS revealed that the deduced amino acid sequence of the enzyme contains 518 amino acid residues. The cDNAs of human and mouse mt SerRS were obtained by reverse transcription-polymerase chain reaction and expressed sequence tag data base searches. Elaborate inspection of primary sequences of mammalian mt SerRSs revealed diversity in the N-terminal domain responsible for tRNA recognition, indicating that the recognition mechanism of mammalian mt SerRS differs considerably from that of its prokaryotic counterpart. In addition, the human mt SerRS gene was found to be located on chromosome 19q13.1, to which the autosomal deafness locus DFNA4 is mapped.

Amino Acid Sequence↗
PubMed2000

Enzymatic properties of sialidase from the ovary of the starfish, Asterina pectinifera.

A sialidase [EC 3.2.1 18] was isolated and highly purified from the ovary of the starfish, Asterina pectinifera, and its enzymatic properties were compared with those of human placental sialidase. The final preparation gave one broad protein band corresponding to sialidase activity on polyacrylamide gel electrophoresis. The molecular weight of the enzyme was 360000 by HPLC on Sigma Chrome GFC-1300 and Sephadex G-150 column chromatography, and 55000 by SDS-PAGE, suggesting the presence of a hexamer in the native protein. The optimum pH was between 3.0 and 4.0, and the enzyme liberated sialyl residues from the following compounds: alpha(2-3) and alpha(2-6) sialyllactose, colominic acid, fetuin, transferrin, gangliosides GM3, GD1a and GD1b. The enzyme was strongly inhibited by 4-aminophenyl and methyl thio-glycosides of sialic acid, but not by those glycosides of 5-amino sialic acid or sialic acid methyl ester. The enzyme was also highly inhibited by sulfated glucan and glycosaminoglycans. The substrate specificity and the effects of inhibitors on starfish sialidase were very similar to those of human placental sialidase.

Animals↗
PubMed2000

Absolute measurement of 166mHo radioactivity and development of sealed sources for standardization of gamma-ray emitting nuclides

Holmium-166m has a long half life (1200 yr) and emits a large number of gamma-rays between 80 and 1400 keV. These characteristics are very suitable for gamma-ray calibration sources, therefore, the absolute activity of 166mHo was measured and several sealed sources were produced to be used as reference sources for the secondary standardization systems for gamma-ray emitting nuclides. In this project, seven metal sealed sources and ten point sources were produced and several of these sources were transferred to the secondary standard laboratories to complete the traceability scheme.

Journal Article↗
PubMed2000

Dexamethasone modifies the effect of Pseudomonas aeruginosa exotoxin A on hearing.

In the present study, the protective effect of dexamethasone was analysed following exposure of the cochlea to Pseudomonas aeruginosa Exotoxin A (PaExoA). Four groups of albino Sprague-Dawley rats were used. 20 microl saline was instilled through the tympanic membrane into the round window niche (group A, n = 4); 1 microg/20 microl dexamethasone sodium 21-phosphate (dexamethasone) solution was instilled (group B, n = 4); 1 microg/20 microl PaExoA solution was initially instilled followed 1 h later by 20 microl saline (group C, n = 6); and 1 microg/20 microl PaExoA solution was initially instilled followed 1 h later by 1 microg/20 microl dexamethasone solution (group D, n = 6). Frequency-specific (4, 8, 10, 12, 16 and 20 kHz) auditory brainstem responses (ABR) were used to ascertain the threshold prior to exposure and 1, 2, 3, and 5 days and 1 and 2 weeks afterwards. No threshold change was observed in groups A and B, whereas the animals in groups C and D showed some threshold elevation, that in D being smaller than that in C. There was a significant difference at the frequencies 12, 16 and 20 kHz, 2 and 5 days after exposure. The intensity-latency (I-L) curve showed that in group D the cochlear component almost disappeared at high frequency one week after exposure. Our results indicate that dexamethasone can modify the effect of PaExoA caused by non-specific inflammation.

Animals↗
PubMed2000

Crystallin proteins in lenses of hereditary cataractous rat, ICR/f.

ICR/f mutation in rat, an inherited disorder, is characterized by the development of cataracts. In this study, we analyzed and compared the crystallins in normal and cataractous rat lenses using gel filtration and two-dimensional gel electrophoresis, and determined the transglutaminase activities and Ca2+ content in the mutant and normal lenses. The Ca2+ content about 10-fold and the activity of transglutaminase was about 1.8-fold higher in the cataractous lenses than in the normal lenses. Analysis of the cataractous lens proteins showed a remarkable decrease in gamma-, betaB1-, betaA3-, and betaA4-crystallin content, accompanied with some increase in alpha-crystallin (or its aggregate). Higher molecular weight proteins were also observed in the cataractous lenses, with molecular masses which correspond to those of cross-linked dimers (43 to 55 kDa) of beta-crystallins. We consider that the mutation accelerates the aggregation of the crystallins, which is associated with their cross-linking by transglutaminase.

Amino Acid Sequence↗
PubMed2000

[A case of angiosarcoma in retroperitoneal cavity].

We report a case of angiosarcoma in the retroperitoneal cavity. A 66-year-old man was admitted to our hospital with the complaint of chest discomfort. Imaging studies including computed tomography scan and magnetic resonance imaging revealed a large solid retroperitoneal mass adjacent to the bladder. There was no evidence of metastasis. The tumor was surgically resected and histopathologically diagnosed as angiosarcoma from the positive staining for VIIIth factor, mitotic figures and abnormal endothelial cells. Six months after surgery, local recurrence adjacent to the bladder appeared. We resected the mass and started adjuvant therapy using Interleukin-2. However, he died of progressed disease one year after the first operation.

Aged↗
PubMed1999

Quantification of two aromatic amine mutagens, PBTA-1 and PBTA-2, in the yodo river system.

The levels of two aromatic amine mutagens, 2-[2-(acetylamino)-4-[bis(2-methoxyethyl)amino]-5-methoxyphenyl]-5-am ino-7-bromo-4-chloro-2H-benzotriazole (PBTA-1) and 2-[2-(acetylamino-4-[N-(2-cyanoethyl)ethylamino]-5-methoxyphenyl]-5-a mino-7-bromo-4-chloro-2H-benzotriazole (PBTA-2), were quantitatively analyzed in the Yodo River system in Japan. The river water samples were collected at nine sampling sites from the Yodo River system twice or three times between May and July in 1997. PBTA-1 and PBTA-2 in the river water samples were concentrated on blue rayon columns, partially purified by high-performance liquid chromatography (HPLC) on reverse-phase columns, then quantified by HPLC with an electrochemical detector. The amounts of PBTA-1 and PBTA-2 in the water samples were < 0.01-1.91 and < 0.01-2.25 ng/L, respectively. High levels of PBTA-1 and PBTA-2 were detected in the samples collected within 4 km downstream of two sewage plants, which are located along the banks of the Nishitakase River, a tributary of the Yodo River system, and these samples showed stronger mutagenicity in Salmonella typhimurium YG1024 with S9 mix than the other water samples. On the other hand, the river water samples from upstream of the sewage plant were weakly or not mutagenic and PBTA-1 and PBTA-2 were not detected. These results confirmed that a major source of PBTA-1 and PBTA-2 in the Yodo River system is effluent from the sewage plants and that discharged mutagens, including PBTA-1 and PBTA-2, are diluted and/or decomposed while moving down the Yodo River system.

Chromatography, High Pressure Liquid↗
PubMed1999

[Usefulness of melatonin for developmental sleep and emotional/behavior disorders--studies of melatonin trial on 50 patients with developmental disorders].

We studied the usefulness of melatonin for sleep disorders and emotional/behavior disturbances of patients with developmental disorders. The efficacy and side effects of melatonin at bedtime were evaluated in 50 children and young adults with sleep disorders (3-28 years old, 41 males and 9 females, autism [AU] in 27 patients, mentally retardation [MR] in 20 patients, and severe motor and intellectual disability [SMID] in 3 patients). The sleep disorders consisted of various types of insomnia in 44 patients and of circadian rhythm sleep disorders in 6 patients. Thirty nine of the insomnia patients and 3 of the circadian rhythm sleep disorder patients experienced improvement in response to melatonin. In some cases, the efficacies were diminished after the daily medication of melatonin. With the emotional/behavior disturbances, excitabilities were often improved in cases whose sleep disorders were also improved. There was almost no change in contrariness, stereotyped behavior and in school/workshop refusal. Melatonin at bedtime was efficacious in 42 of the 50 patients with sleep disorders. In 17 patients, there were side effects (residual drowsiness on the next morning, awakening in the middle of sleep, excitement after awakening and before going to sleep, etc.). But these side effects were not serious. The effects of melatonin were influenced by the type of sleep disturbances, the factors of the environment and the mental conditions. Taking side effects into account, we judged melatonin to be useful in 34 patients.

Adolescent↗
PubMed1998

Expression and characterization of bovine mitochondrial methionyl-tRNA transformylase.

Translational initiation in bacteria and some organelles such as mitochondria and chloroplasts requires formyl-methionyl-tRNA (fMet-tRNA). Methionyl-tRNA (Met-tRNA) undergoes formylation by methionyl-tRNA transformylase (MTF), and the resulting fMet-tRNA is utilized exclusively in the initiation process. The gene encoding mammalian mitochondrial MTF (MTFmt) was cloned recently. When the cDNA corresponding to mature MTFmt was cloned into an expression vector, no expression of MTFmt was observed. However, if the cDNA was fused with the histidine-tag sequence at the N-terminus, MTFmt could be expressed in Escherichia coli. The recombinant enzyme was purified by a single step on a histidine-binding metal affinity column. We previously found that native MTFmt is able to formylate E. coli elongator Met-tRNA as well as the initiator Met-tRNA. The specific formylation of the initiator Met-tRNA by E. coli MTF is quite important in bacterial translational initiation. The purified recombinant MTFmt with the histidine-tag showed almost identical kinetic parameters to those of native MTFmt. This expression system is suitable for the rapid, efficient production of MTFmt in amounts adequate for further biophysical studies, which will provide another approach for elucidating the formylation mechanism, in addition to studies on E. coli MTF.

Animals↗
PubMed1998

Mammalian mitochondrial methionyl-tRNA transformylase from bovine liver. Purification, characterization, and gene structure.

The mammalian mitochondrial methionyl-tRNA transformylase (MTFmt) was partially purified 2,200-fold from bovine liver mitochondria using column chromatography. The polypeptide responsible for MTFmt activity was excised from a sodium dodecyl sulfate-polyacrylamide gel and the amino acid sequences of several peptides were determined. The cDNA encoding bovine MTFmt was obtained and its nucleotide sequence was determined. The deduced amino acid sequence of the mature form of MTFmt consists of 357 amino acid residues. This sequence is about 30% identical to the corresponding Escherichia coli and yeast mitochondrial MTFs. Kinetic parameters governing the formylation of various tRNAs were obtained. Bovine MTFmt formylates its homologous mitochondrial methionyl-tRNA and the E. coli initiator methionyl-tRNA (Met-tRNAfMet) with essentially equal efficiency. The E. coli elongator methionyl-tRNA (Met-tRNAmMet) was also formylated although with somewhat less favorable kinetics. These results suggest that the substrate specificity of MTFmt is not as rigid as that of the E. coli MTF which clearly discriminates between the bacterial initiator and elongator Met-tRNAs. These observations are discussed in terms of the presence of a single tRNAMet gene in mammalian mitochondria.

Amino Acid Sequence↗
PubMed1998

Rabbit models of bucket-handle-like meniscal tear.

After radial tears were artificially created in the periphery of the middle third of the lateral menisci in Japanese white male rabbits, the menisci were sampled postoperatively at 2, 4, 6, 12 and 24 weeks. We noted that radial tears often progressed to longitudinal tears, and the length of longitudinal tears increased with time. On the other hand, the areas in which radial tears had been artificially created were filled with granulation-like tissue. Radial tears thus created may lead to bucket-handle-like tears of the menisci.

Animals↗
PubMed1998

Effects of hyaluronic acid on meniscal injury in rabbits.

Using a model of meniscal injury in rabbit, the effects of hyaluronic acid (HA) injection into the joint on the rate of filling area and the cell shape in the defects were studied. After a cylindrical defect was made in the anterior horn of the lateral meniscus, HA was injected into the joint once a week. At 1 and 6 weeks after the beginning of the weekly injections, the meniscus was compared with a control, which was injected with phosphate buffer instead of HA. The healing in the defect progressed with time. HA administration caused a significant increase in the rate of filling area in the defect. The cell population in the repair tissue changed from fibroblast-like cells to chondrocyte-like cells with the progress of repair. At 6 weeks, the ratio of chondrocyte-like cells to all cells in the repair tissue of the HA-treated meniscus was higher than that of control. These data indicate that HA increases the healing rate of meniscal injury.

Animals↗
PubMed1998

Limb salvage and survival rates among elderly patients with advanced limb ischemia.

The purpose of this study was to clarify the incidence of limb salvage and patient survival rates among elderly patients with advanced leg ischemia. We reviewed the records of 159 patients treated for advanced ischemia over a 15-year period at Aichi Medical University, 74 of whom were aged over 75 years and 85, between 65 and 74 years. There was a collective total of 186 limbs; 82 in the older group and 104 in the younger group. The older group had a greater proportion of women, and a higher incidence of coronary heart disease, pulmonary dysfunction, and acute onset of advanced ischemia than the younger group. Limb salvage was achieved in 73% of the affected limbs in the older group and in 92% of the limbs in the younger group. The poor limb salvage rate in the older group was mainly related to the high initial amputation rate. Early recognition of the sentinel ischemic signs before the ischemia is essential, especially in the elderly. Timely revascularization should be attempted whenever possible, and it should not be abandoned simply because the patient is deemed too old. The 1-, 3-, and 5-year survival rates in the older group were 59%, 28%, and 23%, respectively, which were markedly poorer than the expected survival rates of the age- and sex-matched Japanese population at 1, 3, and 5 years, which were 93%, 79%, and 65%, respectively. Thus, advanced limb ischemia carries a poor prognosis to the point of being life-threatening, and further continuous systemic management with the collaboration of physicians and surgeons must be provided even after the patient has left the hospital.

Aged↗
PubMed1998

Stabilities of N-acetyl-beta-D-glucosaminidase (NAG) isoenzymes in urine: advantage of NAG isoenzyme B measurement in clinical applications.

N-Acetyl-beta-D-glucosaminidase (NAG) is a widely used urinary enzyme for the assessment of renal diseases. We studied the stabilities of NAG isoenzymes in urine at 37 degrees C by enzyme assay and ELISA using a model simulating in vivo conditions. The stabilities were found to be affected by the pH. Under mild acidic condition (about pH 6), there was no significant loss of enzymatic activity of NAG isoenzyme A, enzymatic activity of NAG isoenzyme B and immunological activity of NAG isoenzyme B even after 8 h incubation. In contrast, under alkaline condition (about pH 8), the enzymatic activity of NAG isoenzyme A was rapidly lost, whereas both enzymatic and immunological activities of NAG isoenzyme B were maintained at more than 80% of their initial values. Also, we found that the ratios of endogenous NAG isoenzyme B to total NAG were elevated in alkaline urine samples. These results indicate that NAG isoenzyme A, which is a major isoenzyme in normal urine (pH 5-7), seems to be inactivated in alkaline urine. Our results suggest that for alkaline urine, NAG isoenzyme B should be measured to avoid misinterpretation of total NAG enzymatic activities.

Acetylglucosaminidase↗