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Biomedical subjects

T Amagasa

Publications and source records attributed to T Amagasa.

At least 55 records · Page 3Linked to original sources
PubMed1999

Bone regeneration produced in rat femur defects by polymer capsules containing recombinant human bone morphogenetic protein-2.

PURPOSE: This study examines the effect of polymer capsules containing recombinant human bone morphogenetic protein-2 (rhBMP-2) on bone regeneration in a large segmental bone defect in the rat. MATERIALS AND METHODS: Poly(DL-lactide-co-glycolide) (PLGA) capsules containing 3 microg of rhBMP-2 were implanted in a 5-mm segmental femoral defect in rats, and the femurs were harvested at 4 and 8 weeks after implantation and observed by radiographically and microscopically. RESULTS: At 8 weeks after implantation, union of bone was found radiographically and histologically in the femoral defects implanted with the rhBMP-2/PLGA capsules. In contrast, the control animals did not show bridging of the defect. CONCLUSIONS: This study provides evidence that use of rhBMP-2/PLGA capsules is a promising delivery system to regenerate bone.

Animals↗
PubMed1999

Ultrasonography in the diagnosis of palatal tumors.

OBJECTIVE: The purpose of this study was to evaluate the usefulness of ultrasonography for the preoperative evaluation of palatal salivary gland tumors. STUDY DESIGN: Eleven surgically treated patients with salivary gland tumors of the palate were examined retrospectively. Intraoral ultrasonic scanning examinations were performed with a 10-MHz transducer. RESULTS: The ultrasonographically well-delimited tumors had a complete capsule histologically, whereas the poorly delimited tumors had no capsule or only an incomplete capsule. The tumors that had a reinforced posterior wall echo were associated with pressure bone absorption, and the tumors that had a reinforced posterior echo were associated with bone destruction. Echograms of the tumors were classified into 4 types on the basis of the internal echoes. CONCLUSIONS: Intraoral ultrasonography of palatal tumors can be used to determine the localization and condition of the tumors by close analysis of the echogram. The internal echo pattern on the ultrasonogram of a palatal tumor was found to reflect the pathologic structure of the tumor. Ultrasonography can therefore be a quite useful technique for the preoperative evaluation of palatal salivary gland tumors.

Adenocarcinoma↗
PubMed1999

Inactivation patterns of the p16 (INK4a) gene in oral squamous cell carcinoma cell lines.

To determine whether inactivation of the p16 gene mapped to the chromosome 9p21 region is associated with the development of oral squamous cell carcinoma (SCC), we investigated the mutational states of two forms of alternative transcripts (alpha and beta) from the p16 gene in 14 oral SCC cell lines by means of RT-PCR, PCR, direct sequencing and methylation analyses. Alterations of the alpha transcript were detected in all of the cell lines examined: homozygous deletions in three lines; subtle mutations in exons 1 alpha or 2 in four lines; skipping of exon 2 in two lines; hypermethylation of the 5' CpG island of the p16 gene in four lines; and an unknown mechanism in one line. On the other hand, abnormalities of the beta transcript were observed in seven of the 14 cell lines. Nonetheless, the mutations that essentially affect the function of the encoded protein were found only in five cell lines, including three lines with homozygous deletion. There was no cell line having only beta transcript alterations. Thus, alteration of the alpha transcript of the p16 gene was a highly frequent event in oral SCC. Since this type of alteration resulted in gene inactivation through multiple pathways, it may play a major role in the process of oral SCC development.

Carcinoma, Squamous Cell↗
PubMed1999

Genetic polymorphism of drug-metabolizing enzymes and susceptibility to oral cancer.

An individual difference in the susceptibility to chemical carcinogens is one of the most important factors in the estimate of risk of human cancer. Recently, it has been reported that genetic risk for tobacco-related cancers is associated with polymorphisms of the CYP1A1 and GSTM1 genes in terms of genotype frequencies and cigarette smoking dose. In this study, we investigated the inter-individual difference in genetically determined susceptibility to oral squamous cell carcinoma (SCC) in relation to cigarette smoking dose in a Japanese population. DNA samples were obtained from both patients and controls. We identified individuals at high risk genetically for oral SCC in terms of polymorphisms of the CYP1A1 and GSTM1 genes. This study then compared the estimated total number of cigarettes smoked by patients with those smoked by controls. In this case-control study, we estimated the odds ratios of susceptible to non-susceptible individuals. CYP1A1 genotype C and GSTM1 deficiency were frequently found among oral SCC patients. Patients with genotype C and GSTM1 deficiency contracted carcinoma after fewer cigarettes than those with other genotypes. Individuals with these two genotypes were at remarkably high risk at a low dose level of cigarette smoking. Individual differences in polymorphisms of the CYP1A1 and GSTM1 genes is one important factor in the estimate of risk of oral SCC at a low dose level of cigarette smoking.

Base Sequence↗
PubMed1999

Overexpression of nm23-H2/NDP kinase B in a human oral squamous cell carcinoma cell line results in reduced metastasis, differentiated phenotype in the metastatic site, and growth factor-independent proliferative activity in culture.

The metastasis suppressor activity of nm23/nucleoside diphosphate (NDP) kinase was assessed using human oral squamous cell carcinoma (SCC) cell lines. When the expression of nm23/NDP kinase was compared among several SCC cell lines, nm23-H2/NDP kinase B gene product, but not nm23-HI/NDP kinase A gene product, was reduced in the metastatic cells. Transfection of nm23-H2 into the metastatic SCC cell line LMF4 caused reduction in the lung metastasis in an experimental metastasis assay. A histological analysis of the pulmonary metastatic foci revealed that although foci of the control clones were composed of anaplastic squamous cells, those of the nm23-H2-transfected clones consisted of mostly well-differentiated cells mimicking normal stratified epithelial constitution. The transfected cells were morphologically indistinguishable from the control ones in culture, but they differed from each other in that the former cells proliferated faster than the latter, became less serum dependent, and lost responsiveness to growth factors such as platelet-derived growth factor, insulin-like growth factor I, and insulin, although both clones retained sensitivity to transferrin. These results demonstrate that nm23-H2 protein does have metastasis suppressor activity for human SCC cells and suggest that this activity may be elicited by modulating growth and/or differentiation potential in response to environmental factors.

Animals↗
PubMed1998

Functional evidence for involvement of multiple putative tumor suppressor genes on the short arm of chromosome 3 in human oral squamous cell carcinogenesis.

Cytogenetic and restriction fragment length polymorphism (RFLP) analyses have suggested that a putative tumor suppressor genes(s), which may play an important role in the development of human oral squamous cell carcinoma (SCC), is located on the short arm of chromosome 3 (3p). We previously reported that introducing in intact human chromosome 3 into three different oral SCC tumorigenic cell lines completely suppresses the tumorigenicity of each cell line with significant decrease in the in vitro growth rate and morphological changes. To map the tumor suppressor gene(s) on 3p, we have now examined the tumorigenicity of microcell hybrid clones containing various fragments derived from 3p that were introduced by microcell-mediated chromosome transfer. Sixteen hybrid clones were obtained from four successful experiments, and these clones were classified into two groups: 4 fully tumorigenic clones and 12 suppressed phenotype clones. Analyses of the 3p segments in the series of hybrid clones with the use of RFLP or microsatellite markers revealed that the 3p21.2-p21.3 or 3p25 regions or both were consistently retained in the 12 clones with suppressed phenotype but not in the 4 tumorigenic clones. The more proximal 3p13 region also was retained in three nontumorigenic clones. The overall results are fairly compatible with recent evidence that there are three discrete regions on 3p showing frequent allelic losses on oral SCC, and they directly provide functional evidence for the presence of tumor-suppressor genes for oral SCC in these regions. The possibility that three genes, FHIT, VHL, and T beta R-II, recently identified on 3p may be significantly involved in oral SCC development is also discussed.

Animals↗
PubMed1998

Quantitative evaluation of consistency of normal mucosa, leukoplakia and squamous cell carcinoma of the tongue.

The quantitative differences in consistency of normal mucosa, leukoplakia and squamous cell carcinoma of the tongue were studied. Forty-five patients with squamous cell carcinoma of the tongue, 26 with leukoplakia and 80 with normal tongues were examined using an instrument capable of measuring consistency as a function of the load (in grams) needed to displace tongue mucosa by 2.0 mm using a probe 2.0 mm in diameter. The mean value for consistency in tongue carcinoma, leukoplakia and normal tongue was 22.1 +/- 8.0 g, 8.3 +/- 2.0 g and 4.8 +/- 0.7 g, respectively. Differences in consistency among these entities were significant (P < 0.001). Furthermore, consistency in tongue carcinoma was significantly correlated to tumour thickness (r = 0.954, P < 0.001). It was concluded that the consistency in tongue lesions was objectively and quantitatively evaluated by this method, and this technique could measure the thickness of the tumorous lesions preoperatively.

Adult↗
PubMed1998

[Nerve paralysis after third molar extraction].

This paper described the incidence of inferior alveolar nerve paralysis following surgical removal of impacted third molars. The investigated cases were 789 patients with 1,299 teeth that were surgically extracted. Eight (0.6%) patients had the inferior alveolar nerve paralysis and one (0.08%) had lingual nerve paralysis. As for the patients with inferior alveolar nerve paralysis, the incidence was 0.4% in those aged 20 to 29 years, 0.6% in those aged 30 to 39 years, and 3.5% in those aged over 40 years. This study showed that the incidence of inferior alveolar nerve paralysis occurred more frequently in older age cases and in the cases in which the root splitting or the removing the surrounding bone was needed.

Adult↗
PubMed1997

Oral and maxillofacial tumours in children: a review.

This retrospective review presents our experience of oral and maxillofacial tumours in children. The subjects were 250 children under the age of 15 years (out of a total of 2747 patients with oral and maxillofacial tumours), who were treated after histopathological confirmation of their diagnoses during the 28 years 1965-92. Diagnosis, incidence, and age at presentation were the main outcome measures and the results showed that 232 patients (93%) had benign tumours and 18 (7%) were malignant. The most common benign tumour was haemangioma (n = 69) and the most common malignant tumour sarcoma (n = 14). The most common odontogenic tumour was odontoma (n = 47) and non-odontogenic tumour ossifying fibroma (n = 5). The most common site of soft tissue tumours was the tongue (n = 65) and of bony tumours the mandible (n = 62). About a third of the tumours developed in patients between the ages of 6 and 11 years. Most of the angiomas developed in patients less than 6 years old, and most of the ameloblastomas in those over 12 years of age. Children accounted for 55% of patients with lymphangoma, 41% of those with odontoma, and 22% of those with haemangioma. It is concluded that most of these lesions were probably developmental malformations rather than neoplasms, and that the definition of oral and maxillofacial tumours in children should be reconsidered.

Adolescent↗
PubMed1996

Identification of important regions in the cytoplasmic juxtamembrane domain of type I receptor that separate signaling pathways of transforming growth factor-beta.

Proteins in the transforming growth factor-beta (TGF-beta) superfamily exert their effects by forming heteromeric complexes of their type I and type II serine/threonine kinase receptors. The type I and type II receptors form distinct subgroups in the serine/threonine kinase receptor family based on the sequences of the kinase domains and the presence of a highly conserved region called the GS domain (or type I box) located just N-terminal to the kinase domain in the type I receptors. Recent studies have revealed that upon TGF-beta binding several serine and threonine residues in the GS domain of TGF-beta type I receptor (T beta R-I) are phosphorylated by TGF-beta type II receptor (T beta R-II) and that the phosphorylation of GS domain is essential for TGF-beta signaling. Here we investigated the role of cytoplasmic juxtamembrane region located between the transmembrane domain and the GS domain of T beta R-I by mutational analyses using mutant mink lung epithelial cells, which lack endogenous T beta R-I. Upon transfection, wild-type T beta R-I restored the TGF-beta signals for growth inhibition and production of plasminogen activator inhibitor-1 (PAI-1) and fibronectin. A deletion mutant, T beta R-I/JD1(delta 150-181), which lacks the juxtamembrane region preceding the GS domain, bound TGF-beta in concert with T beta R-II and transduced a signal leading to production of PAI-I but not growth inhibition. Recombinant receptors with mutations that change serine 172 to alanine (S172A) or threonine 176 to valine (T176V) were similar to wild-type T beta R-I in their abilities to bind TGF-beta, formed complexes with T beta R-II, and transduced a signal for PAI-1 and fibronectin. Similar to T beta R-I/JD1 (delta 150-181), however, these missence mutant receptors were impaired to mediate a growth inhibitory signal. These observations indicate that serine 172 and threonine 176 of T beta R-I are dispensable for extracellular matrix protein production but essential to the growth inhibition by TGF-beta.

Amino Acid Sequence↗
PubMed1996

Bone morphogenetic protein encapsulated with a biodegradable and biocompatible polymer.

To develop a controlled release system for bone morphogenetic protein (BMP), poly(DL-lactide-co-glycolide) (PLGA) capsules containing BMP were prepared by an interfacial precipitation method using a water-in-oil-in-water emulsion. The surface morphology, particle size distribution, and hydrolytic degradation rate of the PLGA capsules were examined. The encapsulation yield and release rate of BMP in vitro were measured using fluorescein isothiocyanate-labeled BMP. The amount of BMP released from PLGA capsules increased between days 3 and 5. In addition, the effectiveness of BMP encapsulated in PLGA to induce bone formation in vivo was also examined by subcutaneous implantation in rats. Complete digestion of the capsules and new bone formation including bone marrow were identified by histologic examination of harvested tissues at 3 weeks after implantation. These results demonstrated that encapsulation of BMP with PLGA could be a promising method to induce bone in clinics.

Animals↗
PubMed1996

Insulin enhancement of in vitro wound healing in fetal rat parietal bones.

PURPOSE: This study evaluated the effect of insulin on fracture in fetal rat intramembranous bone using an organ culture system in which bone mineralizes in vitro. MATERIALS AND METHODS: Twenty-day-old fetal rat parietal bones were fractured parallel to the frontal plane and cultured in a serum-free medium with or without insulin for 4 to 12 days. They were then processed for light microscopy. RESULTS: In the specimens not treated with insulin, bony bridges were observed in less than 10% on day 4 and 8, and only 45% on day 12. In bones treated with insulin at 10(-6) mol/L, bony bridges were observed in 73% on day 4 and 100% on day 8 and 12. No callus or cartilage formation was observed during the wound repair process, indicating that intramembranous ossification occurred. CONCLUSION: These findings suggest that insulin has a direct effect on bone cells, which enhances the healing of fractures in intramembranous bone.

Animals↗
PubMed1996

Maxillofacial fractures sustained during sports.

PURPOSE: This study investigated the number and type of maxillofacial fractures caused by various athletic activities. PATIENTS AND METHODS: The ninety-eight patients were treated between 1977 and 1993, and the type of sport involved, patient age and sex, cause of accident, site of injury, and mode of treatment were evaluated. RESULTS: Sports-related maxillofacial fractures accounted for 10.4% of all patients with facial bone fractures. The number of different sports was 19, with the incidence of the fractures being most common in rugby and skiing, followed by baseball and soccer. The ratio of males to females was 5.5:1, and most of the patients were between 10 and 29 years of age. Total restriction from sports activity was between 8 and 12 weeks after initial treatment. CONCLUSION: The treatment for sports-related maxillofacial fractures is not different from that for fractures from other causes. However, it is important to establish some standard for deciding the time when it is possible to participate in sports after a fracture.

Adolescent↗
PubMed1996

Orthodontic treatment of a cleft palate patient with surgically assisted rapid maxillary expansion.

Some adult cleft palate patients show severe maxillary transverse contraction and posterior crossbite. This case report demonstrates successful surgical-orthodontic treatment of such a patient. Surgically assisted rapid maxillary expansion (SA-RME) was completed prior to comprehensive orthodontic treatment. The osteotomy was performed on both the buccal and lingual aspects of the posterior maxillary alveolus. A Hyrax-type maxillary-expansion appliance was used, and the screw (0.2 mm, one quarter turn) was turned two or three times per day. Comprehensive orthodontic treatment was initiated after extraction of the mandibular first premolars and four third molars. The maxillary lateral incisors were also extracted after active orthodontic treatment. The amount of expansion achieved using SA-RME was greater at the posterior than at the anterior maxilla. Midpalatal suture opening occurred. After orthodontic treatment, occlusal stability was satisfactory. This case demonstrates the effectiveness of SA-RME in adult cleft palate patients with severe posterior crossbite.

Adult↗
PubMed1995

Analysis by in vitro mutagenesis of PP2A alpha okadaic acid responsive sequences.

It has been shown that the protein serine/threonine phosphatase type 2A alpha catalytic subunit (PP2A alpha) has a mutation consisting of a glycine substitution for cysteine at 269 in the okadaic acid resistant variant of CHO cells, and that the mutant protein is resistant to okadaic acid (Shima, H. et al. Proc. Natl. Acad. Sci. USA 91, 9267-9271, 1994). In this study we analyzed okadaic acid responsive sequences in PP2A alpha by introducing a mutation at around codon 269 of the cDNA strand. The recombinant mutant PP2A alpha proteins Y265F, C266G, Y267G and C269Y were resistant to okadaic acid, with IC50s of 10, 24, 20 and 10 nM, respectively, as opposed to the recombinant wild PP2A alpha protein which had an IC50 of 0.24 nM. This observation suggests that not only cysteine at 269, but also other YCY amino acids, between 265-267, are necessary for the high sensitivity of PP2A to okadaic acid.

Amino Acid Sequence↗
PubMed1995

Expression of bone sialoprotein mRNA during bone formation and resorption induced by colchicine in rat tibial bone marrow cavity.

In the rat tibial bone marrow cavity, following colchicine injection, there is a phase of osteogenesis in which bone trabeculae replace the necrotic bone marrow tissues and fill the marrow cavity. The newly formed bone is subsequently resorbed by osteoclasts and normal bone marrow is restored. In this study, we correlated these morphologic events with the pattern of gene expression of bone sialoprotein (BSP), an extracellular matrix protein in mineralized tissues, to elucidate the possible functions of BSP in bone formation and resorption in vivo. The expressions of osteopontin (OPN) and type I collagen were also examined. Northern hybridization of the tibia demonstrated that OPN mRNA was gradually increased and expressed at a maximal level 10 days after colchicine injection (during the bone resorption process), while BSP mRNA expression already reached a maximal level at day 6 (during the initial process of bone formation). Its expression was, thus, quite temporary at the beginning of bone formation and different from that of type I collagen, which was continually elevated from days 6 to 10. In situ hybridization of the newly formed bone induced in the tibia revealed that BSP mRNA was evenly expressed in most osteoblasts and osteocytes, moreover in interconnecting colonies of spindle-shaped cells, possibly preosteoblasts, at day 6. At day 10, however, its expression became restricted to some cells on the bone surfaces, some osteoblasts, and most osteoclasts. These observations suggest that BSP may play an important role mainly in the initiation of bone formation and is also associated with the functions of osteoclast in vivo.

Amino Acid Sequence↗
PubMed1995

[A case of injured unerupted permanent tooth in a child].

Children with trauma visit frequently the department of oral and maxillofacial surgery. The treatment for injured permanent teeth is different from that for injured deciduous teeth. We have experienced a case of a 9-year-old boy with an injured unerupted immature permanent tooth with tooth crown fracture. When the tooth erupted gradually, fractured pieces were removed three times, and indirect pulp capping was performed. Three years after the injury eruption was almost completed and pulp was alive, even though the dental roentgenograph showed obliteration of the crown pulp cavity.

Child↗