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Biomedical subjects

K Ito

Publications and source records attributed to K Ito.

At least 235 records · Page 13Linked to original sources
PubMed2001

Secretion monitor, SecM, undergoes self-translation arrest in the cytosol.

The product of the Escherichia coli secM gene (secretion monitor, formerly gene X), upstream of secA, is involved in secretion-responsive control of SecA translation. In wild-type cells, SecM is rapidly degraded by the periplasmic tail-specific protease. It is also subject to a transient translation pause at a position close to the C terminus. The elongation arrest was strikingly prolonged when translocation of SecM was impaired. SRP was not required for this arrest. Instead, the nascent SecM product itself may participate, as the arrest was diminished when it incorporated a proline analog, azetidine. We propose that cytosolically localized nascent SecM undergoes self-translation arrest, thereby enhancing translation of secA through an altered secondary structure of the secM-secA messenger RNA.

Adenosine Triphosphatases↗
PubMed2001

Post-transfusion alloimmunization to granulocytes and platelets in Japanese patients as determined by the MPHA method.

The current occurrence of alloimmunization to granulocytes and platelets after blood transfusion is unclear due to the fact that antibody assays are cumbersome. Using the MPHA method with extracted granulocyte and platelet antigens, a randomized, blinded trial was conducted to investigate three types of alloantibodies in 431 Japanese patients receiving leukocyte-depleted blood transfusions prepared with or without our latest leukocyte-reduction filter. The frequency of granulocyte, platelet and HLA class I alloantibodies was 0.44%, 0.44% and 16.74%, respectively, in patients receiving non-filtered products and 0%, 0% and 0.49%, respectively, in patients receiving filtered products. The granulocyte antibody reacted with an antigen approximately of 51 KDa. The platelet-specific alloantibody was associated with GPIIb/IIIa and GPIa/IIa. The important factors affecting alloimmunization were the transfusion dose and the use of unfiltered platelet products.

Antibody Formation↗
PubMed2001

Functional mapping of ribosome-contact sites in the ribosome recycling factor: a structural view from a tRNA mimic.

Ribosome recycling factor (RRF) is required for disassembly of the posttermination complex of the ribosome after release of polypeptides. The crystal structure of RRF resembles a tRNA shape, with an architecturally different flexibility compared with tRNA, but its structure-and-function relationships are unknown. We here found that an RRF variant defective in ribosome binding regains the binding capacity through 20 independent secondary changes occurring in three topologically distinct regions of RRF. Because two of these regions are equivalent to the tip of the anticodon stem and the upper surface of the acceptor stem of tRNA, RRF may interact with the ribosome in a way similar to tRNA, spanning 30S and 50S subunits, to exert its action for splitting the ribosome.

Binding Sites↗
PubMed2001

Requirement of glutathione and cysteine in guanine-specific oxidation of DNA by carcinogenic potassium bromate.

Potassium bromate (KBrO3), a food additive, induces renal-cell tumors in rats. KBrO3 induced 8-oxo-7, 8-dihydro-2'-deoxyguanosine (8-oxodG) formation in human leukemia cell line HL-60 as well as in its H2O2-resistant clone, HP100, suggesting no involvement of H2O2. Depletion of GSH by buthionine sulfoximine (BSO) had a little inhibitory effect on KBrO3-induced 8-oxodG formation. However, the amount of 8-oxodG was still significantly higher than that in control, suggesting that intracellular Cys can affect KBrO3 to oxidize DNA, when GSH decreased. KBrO3 caused 8-oxodG in isolated DNA in the presence of GSH (tripeptide; gamma-GluCysGly), gamma-GluCys, CysGly, or Cys. Methional completely inhibited 8-oxodG formation induced by KBrO3 plus GSH, but typical hydroxyl radical scavengers, SOD and catalase, had little or no inhibitory effects. When bromine solution (BrO(-)) was used instead of BrO3(-), similar scavenger effects were observed. Experiments with 32P-labeled DNA fragments obtained from the human p53 tumor suppressor gene and the c-Ha-ras-1 protooncogene suggested that KBrO3 induced 8-oxodG formation at 5'-site guanine of GG and GGG sequences of double-stranded DNA in the presence of GSH and that treatment of formamidopyrimidine-DNA glycosylase led to chain cleavages at the guanine residues. ESR spin-trapping studies showed that 1:2:2:1 quartet DMPO (5,5-dimethyl-1-pyrroline N-oxide) spectrum similar to DMPO/hydroxy radical (*OH) adduct, but the signals were not inhibited by ethanol. Therefore, the signal seemed not to be due to *OH but byproduct due to oxidation of DMPO by the reactive species. The signals were suppressed by the addition of dGMP, but not by other mononucleotides, suggesting the specific reactivity with guanine. On the basis of our results and previous literature, it is speculated that reduction of KBrO3 by SH compounds in renal proximal tubular cells yields bromine oxides and bromine radicals, which are the reactive species that cause guanine oxidation, leading to renal carcinogenesis of KBrO3.

Animals↗
PubMed2001

Inhibition of in vitro metabolism of simvastatin by itraconazole in humans and prediction of in vivo drug-drug interactions.

PURPOSE: To evaluate an interaction between simvastatin and itraconazole in in vitro studies and to attempt a quantitative prediction of in vivo interaction in humans. METHODS: The inhibitory effect of itraconazole on simvastatin metabolism was evaluated using human liver microsomes and the Ki values were calculated for the unbound drug in the reaction mixture. A physiologically-based pharmacokinetic model was used to predict the maximum in vivo drug-drug interaction. RESULTS: Itraconazole competitively inhibited the metabolism of simvastatin to M-1 and M-2 with Ki values in the nM range. The area under the curve (AUC) of simvastatin after concomitant dosing with itraconazole was predicted to increase ca. 84-101-fold compared with that without administration of itraconazole. Taking into consideration the fact that this method predicts the maximum interaction, this agrees well with the clinical observation of a 19-fold increase. A similar prediction, based on the Ki value without taking into account the drug adsorption to microsomes, led to an underevaluation of the interaction. CONCLUSIONS: It was demonstrated that the competitive inhibition of CYP3A4-mediated simvastatin metabolism by itraconazole is the main cause of the drug interaction and that a Ki value corrected for drug adsorption to microsomes is the key factor in quantitatively predicting the maximum in vivo drug interactions.

Anticholesteremic Agents↗
PubMed2001

Inherited factor H dysfunction and complement-associated glomerulonephritis in renal grafts of first and second transplantations.

A 38-yr-old man with factor H dysfunction and unknown glomerular disease received first and second renal transplantations (Tx) from living-related donors. His examination showed a low percentage activity of factor H (31%). Factor H dysfunction has been known to be associated with type II or III membranoproliferative glomerulonephritis (MPGN), haemolytic uraemic syndrome and IgA GN. The first graft from his mother showed diffuse mesangial deposit of IgA. His son has had IgA GN and his data also revealed a low percentage activity of factor H (33%). He and his son both showed a low activity of C3. Moreover, his father, who was the donor of the second Tx, had a low percentage activity of factor H (25%), and presented with mild glomerular deposit of C3 at operation, while he has been healthy through his entire 67 yr of life. Each of them had a low percentage activity of factor H. These findings through three generations suggested the inheritance of factor H dysfunction. The patient presented with proteinuria 3 months after the first Tx. At the first biopsy 30 months after the first Tx, light microscopy revealed minor glomerular abnormalities with electron dense deposits in subepithelial, intramembranous and mesangial regions, while immunofluorescence showed massive glomerular deposits of C3. In the second biopsy 51 months after the first Tx, the glomerulonephritis developed mesangial proliferation and crescent formation, accompanied by more massive C3 deposit and intramembranous, mesangial and subepithelial dense deposits. He then required redialysis. At the second and third biopsies within 2 months after the second Tx, the renal graft showed similar findings to the first biopsy after the first Tx. He perhaps presented with a recurrence of complement-associated GN, showing an atypical form of MPGN after Tx. These findings suggest that factor H dysfunction may play an important role of a certain pathogenesis of GN.

Adult↗
PubMed2001

Clinical application of a new compact CT system to assess 3-D images for the preoperative treatment planning of implants in the posterior mandible A case report.

When treatment planning before placing dental implants in the posterior region of the mandible, the locations of the inferior alveolar nerve and mental foramen need to be ascertained, as they determine the bone height available and the implant length selected. The purpose of this study was to introduce the clinical application of a newly developed compact computed tomography system (Ortho-CT) to assess three-dimensional (3-D) images for the preoperative treatment planning of implants in the posterior region of the mandible. To evaluate the 3-D images, we scanned using the Ortho-CT system the mandible with a radiopaque template placed in the posterior region. The Ortho-CT images provided excellent information for evaluating the morphology of the mandible, and for showing the location of the inferior alveolar nerve, mental foramen and the relationship of the template to the bone. We consider that Ortho-CT is a useful aid to preoperative treatment planning of implant therapy in the mandible.

Contrast Media↗
PubMed2001

Palatal radicular multigrooves associated with severe periodontal defects in maxillary central incisors.

BACKGROUND: This case report describes a rare condition of palatal radicular multigrooves on teeth 11 and 21 with severe periodontal defects and the findings at 3-year follow-up. METHOD: Radiculoplasty using hand curettes and rotary burs were used to remove the multigrooves on the root surfaces and change the wrinkled root form to the relatively flat and smooth normal root morphology. Minor tooth movement and frenotomy were performed for a diastema between teeth 11 and 21. Supportive periodontal therapy started immediately after completion of the active treatment. RESULTS: Improved healthy periodontal tissues and adequate plaque control have been maintained.

Adult↗
PubMed2001

Sequential-replenishment mechanism of exocytosis in pancreatic acini.

Here we report exocytosis of zymogen granules, as examined by multiphoton excitation imaging in intact pancreatic acini. Cholecystokinin induces Ca 2+ oscillations that trigger exocytosis when the cytosolic Ca 2+ concentration exceeds 1 microM. Zymogen granules fused with the plasma membrane maintain their Omega-shaped profile for an average of 220 s and serve as targets for sequential fusion of granules that are located within deeper layers of the cell. This secondary exocytosis occurs as rapidly as the primary exocytosis and accounts for most exocytotic events. Granule-granule fusion does not seem to precede primary exocytosis, indicating that secondary fusion events may require a plasma-membrane factor. This sequential-replenishment mechanism of exocytosis allows the cell to take advantage of a large supply of fusion-ready granules without needing to transport them to the plasma membrane.

Animals↗
PubMed2001

Unrelated cord blood transplantation for adult patients with myelodysplastic syndrome-related secondary acute myeloid leukaemia.

Seven adult patients with myelodysplastic syndrome (MDS)-related secondary acute myeloid leukaemia (AML) were treated with total body irradiation (TBI), cytosine arabinoside (Ara-C) and cyclophosphamide (CY), followed by unrelated human leucocyte antigen (HLA)-mismatched cord blood transplantation (CBT). Granulocyte colony-stimulating factor (G-CSF) was infused continuously from 12 h before until the end of Ara-C therapy to enhance the antileukaemia effect of Ara-C. Five patients are alive and free of disease at 7-31 months after transplantation. These preliminary results suggest that adult MDS-related secondary AML patients without suitable related or unrelated bone marrow donors should be considered as candidates for CBT.

Acute Disease↗
PubMed2001

Fas/FasL mediated apoptosis of thyrocytes in Graves' disease.

We examined in the present study the possible involvement of Fas and its ligand (FasL) in the process of Graves' disease. Immunohistochemical analysis showed that few normal thyrocytes expressed Fas but many thyrocytes in Graves' disease expressed this molecule. The percentage of FasL-positive thyrocytes in Graves' thyroids was, however, less than in normal thyroids. Several apoptotic thyrocytes and infiltrating mononuclear cells (MNCs) were detected scattered throughout Graves' thyroid tissues and abundant proliferating cell nuclear antigen (PCNA)-positive thyrocytes were present. Apoptotic cells, as well as PCNA-positive cells, were scarcely detectable in normal thyroid glands, however. In vitro treatment of thyrocytes by IL-1beta a cytokine found to be expressed in Graves' thyroid glands, increased Fas but reduced FasL expression. IL-1beta-stimulated thyrocytes became sensitive to apoptosis by anti-Fas IgM monoclonal antibody (mAb). Activated T cells, which strongly expressed FasL, showed cytotoxic activity toward IL-1beta-stimulated thyrocytes but not toward unstimulated thyrocytes. This cytotoxic activity involved the Fas/FasL pathway. Importantly, unstimulated thyrocytes could kill activated, but not resting, T cells. IL-1beta-stimulated thyrocytes, with down-regulated FasL expression, could not efficiently kill activated T cells. The cytotoxic activity of unstimulated thyrocytes toward activated T cells was inhibited by anti-FasL mAb. Interestingly, unstimulated thyrocytes induced apoptosis in IL-1beta-stimulated thyrocytes but not in unstimulated thyrocytes. These interactions were also blocked by anti-FasL mAb. Our results suggest that the apoptotic cell death of both thyrocytes and infiltrating MNCs found in Graves' thyroid glands is regulated by IL-1beta through Fas/FasL interactions.

Apoptosis↗
PubMed2001

Toxic multinodular goitre in a patient with generalized resistance to thyroid hormone who harbours the R429Q mutation in the thyroid hormone receptor beta gene.

The association of resistance to thyroid hormone (RTH) due to a receptor defect with toxic multinodular goitre or with carcinoma of the thyroid has not been previously reported. Previous histopathological studies of the thyroid gland in patients with RTH have revealed changes similar to multinodular goitre, probably due to continuous stimulation by TSH. We report here a case of generalized resistance to thyroid hormone associated with a multinodular goitre, which became toxic. The patient was a 46-year-old Japanese woman who noticed a goitre although she had no symptoms of thyrotoxicosis. Initial examination revealed elevated serum thyroid hormone levels and a normal TSH level. Ultrasonography disclosed a multinodular goitre with cystic lesions. Three years later, the patient complained that the goitre had become larger and that she had developed symptoms of thyrotoxicosis such as palpitation and hyperhydrosis. Progressive hyperthyroxinaemia with relatively suppressed TSH, increased radioiodine uptake and negative anti-TSH receptor antibodies led to the diagnosis of toxic multinodular goitre. Subtotal thyroidectomy was performed, and pathological examination revealed a micropapillary carcinoma within the multinodular goitre. Occurrence of thyroid carcinoma should be considered in RTH because its incidence is high in multinodular goitre. Molecular examination revealed the R429Q mutation in the thyroid hormone receptor beta gene, which is one of the mutations usually manifesting as the pituitary resistance phenotype. That thyrotoxic manifestations appeared only during toxic stage of multinodular goitre in this case suggests that the phenotype of this type of mutation can be dependent on the amount of thyroid hormone.

Amino Acids↗
PubMed2001

Frequency of appearance of myeloperoxidase-antineutrophil cytoplasmic antibody (MPO-ANCA) in Graves' disease patients treated with propylthiouracil and the relationship between MPO-ANCA and clinical manifestations.

OBJECTIVE: Myeloperoxidase antineutrophil cytoplasmic antibody (MPO-ANCA)-positive vasculitis has been reported in patients with Graves' disease who were treated with propylthiouracil (PTU). The appearance of MPO-ANCA in these cases was suspected of being related to PTU because the titres of MPO-ANCA decreased when PTU was stopped. Nevertheless, there have been no studies on the temporal relationship between the appearance of MPO-ANCA and vasculitis during PTU therapy, or on the incidence of MPO-ANCA in untreated Graves' disease patients. Therefore, we sought to address these parameters in patients with Graves' disease. PATIENTS: We investigated 102 untreated patients with hyperthyroidism due to Graves' disease for the presence of MPO-ANCA, and for the development vasculitis after starting PTU therapy. Twenty-nine of them were later excluded because of adverse effects of PTU or because the observation period was less than 3 months. The remaining 73 patients (55 women and 18 men), all of whom were examined for more than 3 months, were adopted as the subjects of the investigation. The median observation period was 23.6 months (range: 3-37 months). MEASUREMENTS: MPO-ANCA was measured at intervals of 2-6 months. RESULTS: Before treatment, the MPO-ANCA titres of all 102 untreated Graves' disease patients were within the reference range (below 10 U/ml). Three (4.1%) of the 73 patients were positive for MPO-ANCA at 13, 16 and 17 months, respectively, after the start of PTU therapy. In two of them, the MPO-ANCA titres transiently increased to 12.8 and 15.0 U/ml, respectively, despite continued PTU therapy, but no vasculitic disorders developed. In the third patient, the MPO-ANCA titre increased to 204 U/ml and she developed a higher fever, oral ulcers and polyarthralgia, but the symptoms resolved 2 weeks after stopping PTU therapy, and the MPO-ANCA titre decreased to 20.7 U/ml by 4 months after discontinuing PTU. CONCLUSIONS: PTU therapy may be related to the appearance of MPO-ANCA, but MPO-ANCA does not appear to be closely related to vasculitis.

Adolescent↗
PubMed2001

Novel amino acid substitutional mutation, tyrosine-739-aspartic acid, in the androgen receptor gene in complete androgen insensitivity syndrome.

Androgen insensitivity syndrome (AIS) is an X-linked recessive disorder. The molecular mechanism of AIS is reduction or absence of androgen signalling caused by androgen receptor (AR) malfunction or absence. The phenotype of AIS varies from a complete female phenotype (complete AIS, CAIS) to male genitalia with mild hypospadias (partial AIS, PAIS). In the current study, we characterize a novel point mutation in the ligand binding domain of the AR gene in a 50-year-old Japanese CAIS patient. Sequence analysis showed a single point mutation at nucleotide 3359 (Genbank, NM 000044), T to C, in exon E in the AR gene. This mutation led to the conversion of codon 739 tyrosine into aspartic acid in the ligand binding domain. No specific androgen binding was detected in genital fibroblasts isolated from the patient. Transcriptional activating activity of the mutant AR was examined by transient DNA transfection into COS-1 cells. Wild-type AR successfully activated androgen inducible MMTV promoter dose-dependently. In contrast, the mutant AR did not activate MMTV promoter. Thus, we demonstrated the molecular characteristics of the novel point mutation in the ligand binding domain of the AR gene associated with CAIS. This information will provide a further understanding of the structure and function of the AR gene.

Amino Acid Substitution↗
PubMed2001

Identification of a segment of DsbB essential for its respiration-coupled oxidation.

In the Escherichia coli protein disulphide bond formation pathway, membrane-bound DsbB oxidizes periplasmic DsbA, the disulphide bond-introducing enzyme. The Cys-41-Val-Leu-Cys-44 motif in the first periplasmic domain of DsbB is kept strongly oxidized by the respiratory function of the cell. We now show that the characteristic dithiothreitol resistance of the Cys-41-Cys-44 bond was retained even when the flanked Val-Leu combination was replaced by XX sequences from other oxidoreductases. Results of insertion mutagenesis showed that only the insertions (1-31 amino acids) in the region C-terminally adjacent to the CXXC motif impaired the oxidized state of DsbB. Deletion of a single amino acid from this region also rendered DsbB reduced and inactive. However, single amino acid substitutions of the four residues flanked by CXXC and the transmembrane segment did not abolish the oxidation of DsbB. These results suggest that some physical property, such as distance of the CXXC motif from the membrane, is important for the respiration-coupled oxidation of DsbB.

Amino Acid Sequence↗
PubMed2001

N-Terminally extended human ubiquitin-conjugating enzymes (E2s) mediate the ubiquitination of RING-finger proteins, ARA54 and RNF8.

We have previously cloned cDNAs encoding the N-terminally extended class III human ubiquitin-conjugating enzymes (E2s), UBE2E2 and UBE2E3, the biological functions of which are not known. In this study, we performed yeast two-hybrid screening for protein(s) interacting with UBE2E2, and two RING-finger proteins, ARA54 and RNF8, were identified. Both ARA54, a ligand-dependent androgen receptor coactivator, and RNF8 interacted with class III E2s (UBE2E2, UbcH6, and UBE2E3), but not with other E2s (UbcH5, UbcH7, UbcH10, hCdc34, and hBendless) in the yeast two-hybrid assay. The use of various deletion mutants of UBE2E2 and RING-finger proteins and two RING point mutants, ARA54 C(220)S and RNF8 C(403)S, in which the RING structure is disrupted, showed that the UBC domain of UBE2E2 and the RING domain of these RING-finger proteins were involved in this association. Wild-type ARA54 and RNF8, expressed in insect Sf9 cells, catalyzed E2-dependent autoubiquitination in vitro, whereas the point mutated proteins showed markedly reduced activity. Ubiquitination of wild-type ARA54 and RNF8, expressed in COS-7 cells, was also observed, and a proteasome inhibitor, MG132, prevented the degradation of these wild-type proteins, but was much less effective in protecting the RING mutants. Transfection of COS-7 cells with a green fluorescent protein chimera showed that RNF8 was localized in the nucleus, and ARA54 in both the cytoplasm and nucleus. Our results suggest that ARA54 and RNF8 possibly act as Ub-ligases (E3) in the ubiquitination of certain nuclear protein(s).

Amino Acid Sequence↗