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Biomedical subjects

Koichi Ito

Publications and source records attributed to Koichi Ito.

At least 73 records · Page 4Linked to original sources
PubMed2004

Spontaneous correction of pathologic tooth migration and reduced infrabony pockets following nonsurgical periodontal therapy: a case report.

This case report describes the spontaneous correction of pathologic tooth migration and reduced infrabony pockets after nonsurgical periodontal therapy. A 3-mm diastema between the maxillary incisors was closed completely, and the mandibular teeth, which had migrated pathologically, returned to the optimal position. Clinical evaluation showed a significant reduction in probing depth, with increased clinical attachment and bone deposition demonstrated radiologically.

Alveolar Bone Loss↗
PubMed2004

Decreased expression of retinoid X receptor isoforms in human thyroid carcinomas.

Retinoid X receptors (RXRs) are ligand-inducible transcription factors that belong to the superfamily of nuclear hormone receptors. Because RXRs heterodimerize with thyroid hormone receptor, retinoic acid receptor, vitamin D(3) receptor, and peroxisome proliferator-activated receptor, they play central roles in regulating a number of signaling pathways. To understand the roles of RXRs in human thyroid carcinogenesis, we have investigated the immunohistochemical expression of RXRs in normal and neoplastic thyroid tissues. Whereas nontumorous human thyroid cells exhibited distinct nuclear staining for the RXRs, thyroid carcinomas showed decreased nuclear expression of all three RXR isoforms. In particular, some thyroid carcinoma cells showed intense RXR-alpha cytoplasmic staining accompanied by decreased immunoreactivity in their nuclei. This subcellular localization of RXR-alpha was confirmed by Western blot analysis, which showed both lower nuclear expression levels of RXR-alpha and a cytosolic presence of RXR-related protein in neoplastic regions. We present here, for the first time, the histological distribution of each RXR protein (alpha, beta, and gamma) in human thyroid follicular cells. In addition, we found that the nuclear expression of RXRs was lower in thyroid carcinomas than in normal tissue. The differential expressions of these RXRs in thyroid carcinomas might be implicated in the pathogenesis of thyroid cancers.

Blotting, Western↗
PubMed2004

Low frequency of BRAFT1796A mutations in childhood thyroid carcinomas.

A high prevalence of the activating BRAF mutation, BRAF(T1796A), is observed in adult papillary thyroid carcinomas (PTCs). The prognosis of childhood PTCs is generally fairly good despite the fact that distant metastases are often documented in these cases. To investigate the differences between the characteristics of childhood and adult PTCs, we analyzed both BRAF(T1796A) and RAS mutations in 31 Japanese and 48 post-Chernobyl Ukrainian thyroid carcinomas. In the 31 Japanese childhood cases, BRAF(T1796A) was found in only one instance (3.2%), and no RAS mutations were detected. In the Ukrainian subjects, of the 15 childhood and the 33 adolescent and young adult PTCs examined, the BRAF(T1796A) mutation was found in zero and eight cases, respectively, and RAS mutations were found in two of the young adult cases. In addition, 17 of the 48 Ukrainian cases showed expression of the RET tyrosine kinase region, indicating the existence of RET/PTC rearrangements. Unlike adult PTCs, we could detect no positive association between BRAF(T1796A) mutations and clinical parameters in the childhood carcinomas, suggesting that a low prevalence of BRAF(T1796A) is a common feature of PTCs in children regardless of radiation exposure levels. The differences in the prevalence of BRAF(T1796A) mutations between childhood and adult cases of PTC may well reflect inherent differences in the clinical features of these cancers between the two age groups.

Adolescent↗
PubMed2004

Composite metastatic carcinoma in lymph nodes of patients with concurrent medullary and papillary thyroid carcinoma: a report of two cases.

Synchronous occurrence of medullary and papillary carcinoma of the thyroid gland is very rare. We describe two cases of synchronous medullary and papillary carcinoma of the thyroid. In both cases, medullary carcinoma and papillary carcinoma were separate in the thyroid but mixed in some of the lymph node metastases. A review of the literature and our own cases revealed that composite medullary and papillary carcinoma metastases in the lymph nodes is a common feature of patients with synchronous medullary and papillary carcinoma of the thyroid gland.

Adult↗
PubMed2004

The comparative effect of ultrasonic scalers on titanium surfaces: an in vitro study.

BACKGROUND: Professional maintenance is as important for patients with dental implants as it is for patients with natural teeth. However, no proper maintenance instruments have been available for implant patients. The purpose of this in vitro study was to compare the effects of a new ultrasonic scaler (VR), a conventional ultrasonic scaler (SP), and a plastic scaler (PS) on titanium surfaces. METHODS: To simulate subgingival conditions, the implant healing abutments were connected to acrylic resin blocks with artificial gingiva using silicon impression material. The abutments were painted with ink as an artificial form of debris. The ink was removed with the VR, SP, or PS scaler for 60 seconds under standardized conditions, and the removal rate was calculated. The roughness of the abutment surface was measured with a profilometer and observed by scanning electron microscopy (SEM). RESULTS: The removal rate using the VR and SP scalers was higher than that using the PS scaler. No significant differences in the surface roughness or SEM observations were found among the VR, SP, or PS scalers. CONCLUSIONS: In this preliminary study, the new ultrasonic scaler and conventional ultrasonic scaler were shown to be useful for removing artificial debris and produced no significant damage to titanium surfaces compared to plastic scalers. We concluded that new and conventional ultrasonic scalers with a non-metal tip would be suitable for implant maintenance.

Acrylic Resins↗
PubMed2004

Comparison of the effects of various periodontal rotary instruments on surface characteristics of root surface.

The efficacy of scaling and root planing using various periodontal rotary instruments was examined. Eighty extracted human teeth with a history of periodontal disease were divided into four groups of 20 and subjected to one of the following procedures: Use of 1) a Root Burnisher, 2) a Perio Planing Bur (both rotating instruments for contra angle handpieces), 3) a Tooth Planing Bur (rotating instrument for use with an air turbine), or 4) a Gracey Scaler. In each case, the time required for cleaning was measured. Twenty healthy extracted human teeth were used as untreated controls. After treatment, the surface roughness of 10 specimens out of each group were measured using a profilometer and observed by scanning electron microscopy (SEM). Half of the samples were then incubated in dishes with a suspension of fibroblasts. After counting the number of attached cells, the attachment of fibroblasts was observed by SEM. The root surfaces treated with the rotary instruments appeared smooth and there were no significant differences between groups. From the SEM observations, smooth root surfaces with different surface textures were evident and a tight attachment of fibroblasts was observed. The results of this study suggest that use of rotary instruments is superior for periodontal scaling and root planing.

Cell Adhesion↗
PubMed2004

Relationship between Porphyromonas gingivalis, Epstein-Barr virus infection and reactivation in periodontitis.

The aim of this study was to assess the relationship-between Porphyromonas gingivalis, Epstein-Barr virus (EBV) infection and reactivation in periodontitis using real-time PCR. The mean proportion of P. gingivalis cells to total bacterial cells in the saliva from EBV-positive periodontitis patients was significantly higher than that in saliva from EBV-negative patients. An EBV-positive B-cell line was used to determine whether P. gingivalis sonicate induced reactivation of EBV, using real-time PCR to measure the virus genome in the culture medium. A significant increase in EBV numbers was observed after the stimulation with P. gingivalis sonicate. These findings suggest that the interaction between EBV and P. gingivalis is bi-directional, with EBV reactivation suppressing host defenses and permitting overgrowth of P. gingivalis, and P. gingivalis having the potential to induce EBV reactivation.

Adult↗
PubMed2004

Differential gene induction in macrophage-like human cells by two types of Porphyromonas gingivalis: a microarray study.

Several studies have provided clinical evidence that FimA clonal variation may contribute to the periodontopathogenicity of Porphyromonas gingivalis (P.g.). We studied the gene expression profiling of the macrophage-like human cell line U937 after infection of two types of P.g. (fimA type I; Pg-I and fimA type II; Pg-II) using microarray. Of 1088 genes examined, 394 genes were detectable. Bioinformatics algorithms were used to analyze the detectable genes. Hierarchical clustering analysis showed that gene expression patterns of Pg-II and the control (no infection) were grouped together. K-means clustering grouped 79 genes into Pg-II dominance and 88 genes into Pg-I dominance. A large number of genes related to cell signaling, extracellular communication proteins, cell receptors (by ligands), protein turnover and cell adhesion receptors/proteins were grouped into clusters of Pg-I dominance. Our results indicate that compared with Pg-I, Pg-II induces a low host response as measured by its weak induction of gene expression.

Bacteroidaceae Infections↗
PubMed2004

[Examination of occupational exposure to medical staff (primarily nurses) during 131I medical treatments].

Recently, a new amendment to protect against radiation damage to humans has been enacted based on a 1990 recommendation by the ICRP. Consequently, the dose limits of occupational exposure to medical staff were cut down sharply compared with conventional readjustments. This amended bill, however, may be triggering a reduction in the number of applicants, which hope to engage in radiotherapy. This being the case, we measured the dose levels of the occupational exposure to medical staff (doctor's group, nuclear medicine technologist's group, nurse's group and pharmacist's group) from 1999 to 2002. Moreover, we investigated what the main factor is in nurse's occupational exposure to 131I. The highest doses of occupational exposure were 3.640 mSv to doctors, 7.060 mSv to nuclear medicine technologists, 1.486 mSv to nurses and 0.552 mSv to pharmacists. According to our results, it was clear that the highest doses in each group were far below the legally mandated upper limits of exposure doses. Although we investigated the correlations between the factors of nurse's occupational exposure to 131I with the number of inpatients, the amount of 131I and the number of servicing times for patients, there were no correlations found. Furthermore, to analyzing the factors in detail, it became clear that the main factor in the nurse's occupational exposure was due to the existence of patients who needed many more servicing times for their care than ordinary patients.

Humans↗
PubMed2003

Antizyme frameshifting as a functional probe of eukaryotic translational termination.

Translation termination in eukaryotes is mediated by the release factors eRF1 and eRF3, but mechanisms of the interplay between these factors are not fully understood, due partly to the difficulty of measuring termination on eukaryotic mRNAs. Here, we describe an in vitro system for the assay of termination using competition with programmed frameshifting at the recoding signal of mammalian antizyme. The efficiency of antizyme frameshifting in rabbit reticulocyte lysates was reduced by addition of recombinant rabbit eRF1 and eRF3 in a synergistic manner. Addition of suppressor tRNA to this assay system revealed competition with a third event, stop codon readthrough. Using these assays, we demonstrated that an eRF3 mutation at the GTPase domain repressed termination in a dominant negative fashion probably by binding to eRF1. The effect of the release factors and the suppressor tRNA showed that the stop codon at the antizyme frameshift site is relatively inefficient compared to either the natural termination signals at the end of protein coding sequences or the readthrough signal from a plant virus. The system affords a convenient assay for release factor activity and has provided some novel views of the mechanism of antizyme frameshifting.

Animals↗
PubMed2003

DNA immunization via intramuscular and intradermal routes using a gene gun provides different magnitudes and durations on immune response.

We investigated the antibody (Ab) and cytotoxic T lymphocyte (CTL) responses to gene gun (GG)-mediated DNA immunization via the intramuscular (i.m.) and intradermal (i.d.) routes. BALB/c mice were immunized five times at weekly intervals with plasmid DNA encoding enhanced green fluorescent protein (EGFP). EGFP production was rapidly detected in the target tissues after injection via either delivery route. There were significant differences in the magnitude and duration of the Ab and CTL responses according to the route employed. Intradermal injection elicited higher Ab and CTL responses to EGFP than i.m. injection 1 week after the last immunization. However, both immune responses were reduced rapidly 5 weeks after the last immunization via i.d. injection. In contrast, in mice injected via the i.m. routes, Ab and CTL responses 5 weeks after the last immunization remained at levels similar to those detected after 1 week. All mice generated a predominantly IgG1 Ab response via either route. These findings suggest that a combination of these two routes of DNA immunization would provide optimal conditions for induction of a broad immune response, and this information is expected to be very important for future applications of DNA vaccination.

Animals↗
PubMed2003

Making sense of mimic in translation termination.

The mechanism of translation termination has long been a puzzle. Recent crystallographic evidence suggests that the eukaryotic release factor (eRF1), the bacterial release factor (RF2) and the ribosome recycling factor (RRF) all mimic a tRNA structure, whereas biochemical and genetic evidence supports the idea of a tripeptide 'anticodon' in bacterial release factors RF1 and RF2. However, the suggested structural mimicry of RF2 is not in agreement with the tripeptide 'anticodon' hypothesis and, furthermore, recently determined structures using cryo-electron microscopy show that, when bound to the ribosome, RF2 has a conformation that is distinct from the RF2 crystal structure. In addition, hydroxyl-radical probings of RRF on the ribosome are not in agreement with the simple idea that RRF mimics tRNA in the ribosome A-site. All of this evidence seriously questions the simple concept of structural mimicry between proteins and RNA and, thus, leaves only functional mimicry of protein factors of translation to be investigated.

Anticodon↗
PubMed2003

The critical role of the universally conserved A2602 of 23S ribosomal RNA in the release of the nascent peptide during translation termination.

The ribosomal peptidyl transferase center is responsible for two fundamental reactions, peptide bond formation and nascent peptide release, during the elongation and termination phases of protein synthesis, respectively. We used in vitro genetics to investigate the functional importance of conserved 23S rRNA nucleotides located in the peptidyl transferase active site for transpeptidation and peptidyl-tRNA hydrolysis. While mutations at A2451, U2585, and C2063 (E. coli numbering) did not significantly affect either of the reactions, substitution of A2602 with C or its deletion abolished the ribosome ability to promote peptide release but had little effect on transpeptidation. This indicates that the mechanism of peptide release is distinct from that of peptide bond formation, with A2602 playing a critical role in peptide release during translation termination.

Bacterial Proteins↗
PubMed2003

Effects of occlusiveness of a titanium cap on bone generation beyond the skeletal envelope in the rabbit calvarium.

We evaluate the effects of occlusiveness of a titanium cap on bone generation beyond the skeletal envelope. In eight rabbits, the calvarial bone was exposed and a circular groove was prepared with a trephine drill. After marrow penetration, a standardized hemispherical titanium cap, either with or without small holes (1.5 mm in diameter), was then placed into the bone and covered by a cutaneous flap. After 1 month or 3 months of healing, the animals were euthanized and examined histologically. The percentage area of newly generated tissue consisting of mineralized bone and marrow spaces in each section was calculated relative to the area bounded by the hemispherical shape of the titanium cap and the parent bone; this latter volume was taken to be 100%. Furthermore, the cross-sectional areas of generated mineralized bone expressed as percentages of the total tissue area generated within each space were determined. In the 1-month specimens, there was no statistically significant difference between the two caps in the amount of tissue generated, 54.7%+/-12.2% with holes vs. 60.4%+/-8.8% without holes (p=0.225). However, in the 3-month specimens, we observed a significant difference between the caps (55.9%+/-7.4% with holes vs. 89.9%+/-6.5% without holes, P<0.05). Also, there was a statistically significant difference between 1- and 3-month specimens in the amount of tissue generated under the cap without holes (60.4%+/-8.8% vs. 89.9%+/-6.5%, P<0.05). Although there was no significant difference in the relative amount of mineralized bone generated between the caps with holes and those without holes in the 1-month specimens (27.7%+/-4.8% vs. 30.8%+/-6.4%, P=0.225), there was a statistically significant difference between the two caps in the 3-month specimens (24.3%+/-4.1% with holes vs. 34.0%+/-8.6% without holes, P<0.05). A substantial ingrowth of fibrous connective tissue through the holes appeared to prevent further new tissue generation in a defined area adjacent to the bone surface. We concluded that total occlusiveness, sufficient stiffness of the cap, as well as the passage of time will allow predictable mineralized bone augmentation to occur in spaces beyond the skeletal envelope.

Animals↗
PubMed2003

Generation of free radicals and/or active oxygen by light or laser irradiation of hydrogen peroxide or sodium hypochlorite.

Generation of free radical and/or active oxygen by light or laser irradiation of hydrogen peroxide (H2O2) or sodium hypochlorite (NaClO), which have been used for tooth whitening or root canal irrigation, was investigated using electron spin resonance spectroscopy combined with a spin-trapping technique. When H2O2 was exposed to light or laser radiation, the amount of hydroxyl radical generated changed according to the concentration of H2O2 and irradiation time. The amount of 5,5-dimethyl-1-pyrrolidone-(2)-oxyl-(1) (DMPO-X) also changed in accordance with irradiation time. The amounts of hydroxyl radical generated from H2O2 after irradiation were in the order: plasma lamp > halogen lamp > He-Ne laser > Yellow He-Ne laser. On the other hand, the amounts of DMPO-X generated from NaClO after irradiation were in the order: plasma lamp > Yellow He-Ne laser > halogen lamp > He-Ne laser.

Cyclic N-Oxides↗
PubMed2003

Lymph node metastasis from 259 papillary thyroid microcarcinomas: frequency, pattern of occurrence and recurrence, and optimal strategy for neck dissection.

OBJECTIVE: To determine the frequency and pattern of lymph node metastasis (LNM) from papillary thyroid microcarcinoma (PTMC) and the results of node dissection, and to establish the optimal strategy for neck dissection in these patients. SUMMARY BACKGROUND DATA: Most PTMCs carry a favorable prognosis, but a few present with palpable lymphadenopathy. Patients with LNM are at risk for nodal recurrence, although they do not have higher mortality. The frequency and pattern of LNM from PTMC and the results of node dissection are not well established. METHODS: The frequency and pattern of LNM from 259 PTMCs were analyzed according to the size and location of the primary tumor. Of the 259, 24 with palpable nodes underwent therapeutic node dissection and the other 235 patients without palpable nodes underwent prophylactic node dissection. The authors compared the results of node dissection between the therapeutic group and the prophylactic group, and between PTMCs 5 mm or smaller and PTMCs larger than 5 mm. The authors also compared nodal recurrence between the prophylactic group and a no-lymph-node-dissection group (155 PTMCs). RESULTS: Overall, 64.1% (166/259) and 44.5% (93/209) had node involvement of the central and ipsilateral lateral compartment, respectively. Pretracheal (43.2%), ipsilateral central (36.3%), and ipsilateral mid-lower (37.8%) jugular were more commonly involved. LNM was more frequent in the therapeutic group than in the prophylactic group (95.8% vs. 60.9% for central compartment, 83.3% vs. 39.5% for ipsilateral lateral compartment). Nodal recurrence was more common in the therapeutic group than in the prophylactic group (16.7% vs. 0.43%), but did not differ between the prophylactic group and the no-dissection group (0.43% vs. 0.65%). The tumor size did not influence nodal recurrence. Nodal recurrence preferentially occurred in ipsilateral mid-lower jugular nodes. CONCLUSIONS: Patients who have PTMC presenting with palpable lymphadenopathy should have therapeutic node dissection. Prophylactic node dissection is not beneficial in those without palpable lymphadenopathy.

Adolescent↗