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Biomedical subjects

M Shimono

Publications and source records attributed to M Shimono.

At least 37 records · Page 2Linked to original sources
PubMed2001

The in vitro and in vivo influence of 4-META/MMA-TBB resin components on dental pulp tissues.

The purpose of this study was to qualitate the penetration of the major components of 4-META/MMA-TBB adhesive resin (4-META resin) and to characterize their influence on the in vitro and in vivo wound healing of dental pulp tissues. Fresh 4-META resin was applied to rabbit mesentery; its components penetrated the mesentery to form three of layers, depending on the amounts of monomer components in the tissue. The superficial layer was a soft-tissue hybrid layer (STHL), the intermediate layer contained small particles of polymerized 4-META resin, while the deepest layer contained unpolymerized monomer components including MMA and butanol, which were detected by gas chromatography (GC). To characterize the in vivo effects of the deepest layer, we immersed the pulp tissue in MMA or in 5% 4-META/MMA and autotransplanted it to placement beneath a rabbit kidney capsule. The MMA-immersed pulp was positive for osteocalcin and presented osteodentin formation at 7 days, as did the untreated control pulp tissue. In contrast, the 5% 4-META/MMA-immersed pulp collapsed into the cell-deficient fibrous connective tissue, with slight calcification by 7 days and less osteodentin formation at 14 days. Analysis of these data suggests that MMA does not inhibit osteogenic activity of pulp tissue, while 5% 4-META/MMA does inhibit osteogenic activity to some extent.

Acrylic Resins↗
PubMed2001

Spontaneous onset of torsade de pointes in long-QT syndrome and the role of sympathovagal imbalance.

The net effects of sympathetic and vagal activity on the QT interval and the mode of spontaneous onset of torsade de pointes (TdP) are still unclear in long-QT syndrome. Two patients with long-QT syndrome had syncope while undergoing Holter ECG investigation. The spontaneous onset of TdP in these patients was analyzed with respect to the relation between the RR and QT intervals. Both patients were high-school students (16- and 17-year-old boys) who had been diagnosed as long-QT syndrome and followed up without medical treatment because they had had neither a history of syncope nor arrhythmia induction by treadmill exercise tests. The first episode of syncope in both patients occurred during ordinary daily life and was not related to exercise or psychological stress. The dynamic changes between the RR and QT intervals associated with the spontaneous onset of TdP were analyzed by Holter ECG. Both patients showed sinus tachycardia followed by abrupt sinus bradycardia immediately before the onset of TdP. The enhanced rate of the adaptive response of the QT interval that occurred during the deceleration of the heart rate preceded the onset of TdP. These observations suggest that the complex situation that follows sympathovagal imbalance may have an important role in the dynamic change in the QT interval and initiation of TdP in patients with long-QT syndrome.

Adolescent↗
PubMed2001

Characteristics of newly formed bone during guided bone regeneration: observations by immunohistochemistry and confocal laser scanning microscopy.

The purpose of this study was to investigate the characteristics of new bone formation during guided bone regeneration (GBR) using immunohistochemistry and confocal laser scanning microscopy. e-PTFE membranes were applied to defects created in the tibiae of rats, and some animals were sacrificed 6, 8, or 10 days later. Serial paraffin sections were cut, stained with H-E, and examined to analyze the ratio of new bone formation. Immunohistochemical staining with a monoclonal antibody specific for PCNA was used to evaluate the proliferating activity. In other experimental rats, calcein was injected at 6, 8, and 10 days after the surgery, and the animals were sacrificed 48 hr after injection. Their tibiae were removed, and Villanueva bone staining was performed before observation using confocal laser scanning microscopy to investigate the mineralization of new bones. The bone occupation ratio increased day by day, but the experimental groups had significantly higher ratios than control groups (without membrane) at each of the time periods. However, PCNA positive cells decreased over time in all groups, and there were no significant differences among the groups. Mineralization occurred more rapidly in the experimental groups than in the control groups. These results suggest that GBR accelerates the migration of osteogenic cells, the formation of new bone, and mineralization in the defect created by the e-PTFE membrane.

Animals↗
PubMed2001

A case of an ameloblastic fibro-odontoma arising from a calcifying odontogenic cyst.

This case report describes an ameloblastic fibro-odontoma arising from a calcifying odontogenic cyst (COC) in the mandible of a twenty-three-year old male. The patient was referred to the Department of Oral Surgery, Tokyo Dental College, on March 30th, 2000, complaining of a painful swelling, which had appeared three weeks earlier on his left mandibular molar region. In a pathological view, the lesion was a round cyst the size of a chicken-egg, dark red in color, and surrounded by a thick membrane. The cyst had an epithelium of varying thickness which included many ghost cells and an enamel-like structure on the inside, and a thick wall of connective tissue with an ameloblastic fibro-odontoma on the outside. Enamel organ-like epithelial islands were structured radially in the form of strands with immature dentin. Cytokeratin 19 was strongly immunoreactive in the epithelium of the lesion; osteopontin and osteocalcin reacted in the mesenchymal cells and weakly in the epithelial element of this tumor.

Adult↗
PubMed2000

Immunohistochemical study of dental pulp applied with 4-META/MMA-TBB adhesive resin after pulpotomy.

The purpose of this study was to investigate nerve regeneration and proliferative activity in amputated pulp tissue after the application of 4-META/MMA-TBB adhesive resin (4-META resin). Calcium hydroxide was used as a control material. At 3 days, fibroblast-like cells were positive for proliferating cell nuclear antigen (PCNA) in both 4-META resin- and calcium hydroxide-treated groups and were located mainly within 0.5 mm from the cut surface. Only a few fragmented neurofilament protein (NFP)-positive nerve fibers were observed in this area. At 7 and 14 days, the number of PCNA-positive cells had gradually decreased and regenerated NFP-positive nerve fibers were observed close to the cut surface of the pulp in both groups. At 21 days in the experimental group, several PCNA-positive cells were still found in the area 0.5 mm from the cut surface, and NFP-positive nerve fibers were detected about 0.15-;0.2 mm from the cut surface. In contrast, a dentin bridge was produced under the necrotic layer at 21 days in the control group. PCNA-positive cells were not found underneath the dentin bridge, but NFP-positive nerve fibers had regenerated close to it. These results suggest that although cell differentiation and nerve regeneration are delayed, wound healing occurred even after the application of 4-META resin to exposed pulp surface the same as calcium hydroxide application.

Animals↗
PubMed2000

Expression of connexin 32 and 43 in developing rat submandibular salivary glands.

The expression of the gap-junction proteins connexin 32 and 43 in the developing rat submandibular gland was determined using reverse transcription-polymerase chain reaction and immunohistochemistry. Sprague-Dawley rats from the 17th gestational day through to the 28th postnatal day were used. Connexin 43 gene expression was detected on the 17th gestational day. Connexin 32 gene expression was also detected on the 17th gestational day but less intensely. Immunolabelling for connexin 43 was also found in the developing submandibular gland from the 17th gestational day. Prenatally the most immunoreactive areas for connexin 43 were located in the periphery of terminal tubules, but some staining was discernible between the cells in terminal buds. In the postnatal period, reactive areas were located at both the periphery of acinus-like structures and around the intercalated duct. This is consistent with the known association of connexin 43 with myoepithelial cells. Connexin 32 immunostaining was first detected in the developing submandibular glands on the 18th day of prenatal development. Positive staining was present on the lateral side of the proacinar and mature acinar cells. The number of immunoreactive areas per cell increased during early development followed by a significant decrease perinatally. During postnatal development the density of areas again showed a pattern of increase. These results suggest that connexin 43 is associated with growth and differentiation in the pre- and perinatal periods and also with the contractile function of myoepithelial cells in the postnatal period of the developing submandibular gland. It is also implied that the number of connexin 32-positive areas may correspond to an increase or decrease in the number of proacinar and mature acinar cells.

Animals↗
PubMed2000

Connexins in salivary glands.

Connexins (Cxs) make up a family of gap junction structural proteins that form hexameric assemblies in the plasma membranes of adjacent cells that interact to form intercellular channels. It has been demonstrated that many kinds of CXs are differentially expressed in a variety of tissues; however, there have been only a few studies of CX expression in rat salivary glands. The co-localization of CX26 and 32 was examined in the parotid glands. Double immunofluorescence revealed that CX26 and 32 were present in the same gap junction. Double immuno-electron microscopy showed co-localization of both CX26 and 32 on the same gap junctional membranes between acinar cells. These results suggest that CX26 and 32 may participate in regulation of secretory function and permeability of acinar cells in the rat parotid glands.

Animals↗
PubMed2000

Tight junctions in the rat parotid gland.

The aim of this study was to elucidate the distribution and morphological changes of tight junctions during secretion in parotid gland acinar cells. Localization of tight junction-associated polypeptide ZO-1, and of tight junction transmembrane protein Occludin, was examined in rat parotid gland by immunofluorescence and immunogold labelling of ultrathin sections. Adult male Sprague-Dawley rats were intraperitoneally injected with IPR and, after 10 and 30 minutes, parotid glands were extirpated. In control specimens, positive immunoreaction for ZO-1 and Occludin was observed on the adluminal side between adjacent cells in the form of narrow elongated profiles corresponding to intercellular canaliculi. After IPR injection, canaliculi became dilated and fluorescence was no longer seen as a continuous line but appeared as an aggregation of separate bright particles. ZO-1 was more widely distributed and was recognized in other areas of the cytoplasm as well. Concurrently, omega-shaped concavities, marked by actin fluorescence, appeared along the intercellular canaliculi. We concluded that, during exocytosis, the selective permeability barrier to the paracellular pathway, based on tight junctions, becomes more leaky, owing to segregation of Occludin caused by intracellular ZO-1 distributional changes associated with actin filaments.

Animals↗
PubMed2000

Ultrastructural and immunoelectron microscopic studies of the peri-implant epithelium-implant (Ti-6Al-4V) interface of rat maxilla.

BACKGROUND: The role played by the internal basal lamina (IBL) and hemidesmosomes between an implant and the peri-implant epithelium (PIE) in the adherence of the epithelium to the implant is controversial. This study used rat maxilla implantation models to clarify the ultrastructure of the PIE-implant interface. METHODS: Ti-6Al-4V implants were inserted either immediately or 2 weeks after the extraction of the upper left first molar of 6- or 4-week-old rats, respectively. The junctional epithelium (JE) of the upper right molars in the same animals was used as a control. Four weeks after implantation, the animals were sacrificed to prepare specimens for light and immunoelectron microscopy. RESULTS: Under light microscopy, the PIE appeared to attach to the implant surface. Ultrastructurally, IBL, consisting of the lamina densa and lamina lucida, and hemidesmosomes were formed only in the lower region, and rarely in the middle region, of the PIE-implant interface. In control teeth, the IBL and hemidesmosomes formed throughout the dento-JE interface. Laminin-1 was found in the IBL and also in the vesicles and vacuoles of the PIE and JE cells. Statistical analysis showed that there was also a significant difference in the amount of IBL between the PIE-implant and dento-JE interfaces. CONCLUSIONS: PIE attached to the implant via hemidesmosomes and IBL in the lower region of the PIE-implant interface. Although PIE cells may secrete laminin-1, which contributes to epidermal cell adhesion, the PIE which attaches to implants only in the lower region of the interface is considered to be the poorly adhered epithelium.

Alloys↗
PubMed1999

Pattern of expression of beta-defensins in oral squamous cell carcinoma.

Human beta-defensin (hBD)-1 and hBD-2 are antimicrobial peptides that have been detected in certain types of epithelia, including the skin and oral epithelia. It has been suggested that bacterial infection is an important factor in the process of carcinogenesis. The expression of hBDs in oral squamous cell carcinoma (SCC) may be down-regulated. We studied the pattern of expression of hBD-1 and hBD-2 mRNA in oral (SCC) cell lines and in tumor samples obtained from four patients with oral SCC who underwent surgical resection, by reverse transcription-polymerase chain reaction (RT-PCR). Human gingival epithelial (HGE) cells were used as the control. The effect of various inflammatory cytokines on hBD-1 and hBD-2 expression in the HGE cells and SCC cell lines, was also studied. hBD-1 mRNA was detected in the Ca-9, SCC-9 and HSC-4 cell lines, but not in the SAS and KB cell lines. hBD-2 mRNA was detected in all five cell lines. All four tumor samples expressed both hBD-1 and hBD-2 mRNA, although the mRNA level of each protein varied. These results indicate that SCCs in which hBD expression is downregulated, may be susceptible to bacterial infection.

Aged↗
PubMed1999

Circadian variation of idiopathic ventricular tachycardia originating from right ventricular outflow tract.

We determined circadian variation of isolated ventricular premature complexes (VPCs), 2 to 4 consecutive VPCs, and ventricular tachycardia (5 consecutive VPCs) originating from the right ventricular outflow tract in patients without apparent structural heart diseases. There was apparent circadian variation with 2 prominent peaks for these ventricular arrhythmias, and blockade abolished ventricular tachycardia and attenuated the circadian variation of consecutive VPCs.

Adult↗
PubMed1999

Cell proliferation and death of Hertwig's epithelial root sheath in the rat.

Hertwig's epithelial root sheath (HERS) degenerates immediately after root dentin is formed. However, odontogenic tumors or cysts may originate from residual cells, although little is known about how HERS proliferates and disappears. This study investigated whether cell death is provoked in the tissues surrounding the root during eruption of the rat upper molar. We employed the TdT-mediated-dUTP nick end labeling (TUNEL) method and transmission electron microscopy (TEM) to observe the morphological features of cell death. We examined the activity of cell proliferation immunohistochemically using proliferative cell nuclear antigen (PCNA) and the continuity of HERS using polyclonal keratin antibody (PK). Cell death resembling apoptosis and apoptotic bodies phagocytosed by neighboring mesenchymal cells were detected in only a few cells by both TUNEL and TEM. We also found cells with electron-lucent cytoplasm which contained dilated or ruptured mitochondria and remarkably dilated rough endoplasmic reticulum (rER) which lay sparsely along the root. These cells seemed to be dead HERS cells based on their ultrastructural features, location, and stage. PCNA-positive cells were found in the apical end of the HERS cells, fibroblasts of the periodontal ligament, and odontoblasts. PK reacted with HERS; however, PK-positive cells partially disappeared after the 15th postnatal day when the root dentin had formed slightly. These results may indicate that HERS cells migrate into the periodontal ligament or die immediately after root dentin is formed and that various types of cell death such as apoptosis and cytoplasmic type occur in the tissues surrounding the root during tooth development.

Animals↗
PubMed1999

Clinical investigation of atypical adenomatous hyperplasia of the lung.

The clinicopathologic characteristics of atypical adenomatous hyperplasia (AAH) remain unclear. A total of 137 patients underwent resection for adenocarcinoma of the lung at our institution. Examination of resected lung tissue showed that in addition to adenocarcinoma AAH was present in 26 cases and was not present in 111 cases. All nonsmokers with AAH (n = 13) had earlier-stage disease (stage IA, IB, IIA, and IIB) and no history of respiratory disease. Among patients with stage IA disease, the relapse-free and overall survival curves for those with AAH (n = 14) tended to be better than for those without AAH (n = 40), but the difference was not statistically significant (P = 0.056 and 0.087, respectively). Concurrent presence of AAH may be a favorable prognostic indicator in patients with stage IA adenocarcinoma.

Adenocarcinoma↗
PubMed1999

Changes in autonomic nervous activity after catheter ablation of right ventricular outflow tract tachycardia.

Idiopathic right ventricular outflow tract (RVOT) tachycardia is prone to occur when sympathetic nervous activity increases. The effects of catheter ablation on the arrhythmia may be modified by changes in the sympathovagal balance induced by the ablation. In 8 patients with RVOT tachycardia, analyses of heart rate variability (HRV) were performed before, early (1-3 days, POST1) and late (7-14 days, POST2) after the ablation. From 24-h ambulatory Holter monitoring, RR intervals of a 2-h period during sleep (00.00-06.00 h) were analyzed. MSSD and pNN50 were increased along with a decrease in the frequency of ventricular arrhythmias at both POST1 and POST2 after successful ablation. In contrast, high frequency power (HF) was increased, and low frequency power (LF) and LF/HF were decreased only at POST2 in the 8 patients. In 4 patients in whom the initial ablation had been unsuccessful, the indices of HRV did not change significantly after the unsuccessful ablation, but after successful ablation they changed as in the other 4 patients. After successful catheter ablation of the RVOT tachycardia, sympathetic nervous activity was decreased and parasympathetic nervous activity was increased along with decrease in the frequency of ventricular arrhythmias. The presence of ventricular tachyarrhythmia could, therefore, elicit sympathetic predominance and consequently modify arrhythmogenesis.

Adult↗
PubMed1999

Influences of 4-meta/MMA-TBB adhesive resin on osteodentinogenesis of transplanted rabbit dental pulp in vivo: immunohistochemical and electronmicroscopic studies.

The purpose of this study was to investigate the influence of 4-META/MMA-TBB adhesive resin (4-META resin) on osteodentinogenesis of transplanted pulp in vivo. Dental pulp was obtained from the incisors of adult rabbits. 4-META resin was applied to the pulp tissue, and the pulp tissue with 4-META resin was autotransplanted beneath the renal capsule with the pulp side touching the kidney. Pulp tissue alone was also transplanted as a control. The animals were sacrificed at 3, 7, and 14 days after the experiment, and the specimens were examined morphologically. At 3 days, proliferation of mesenchymal cells was observed, and alkaline phosphatase activity (ALP) and osteocalcin were detected throughout the entire transplanted pulp area. In the experimental case, a thin, highly electron dense zone and a granular layer were observed. Under this layer, only a cell-membrane-like structure, a cell with an unclear nucleus, a nucleus alone, and an organelle-like structure could be seen. Furthermore, an exudative layer with many neutrophils was observed, and apoptotic-body-like structures were also found in some areas. On days 7 and 14 in the control group, osteoblast-like cells had proliferated, and osteodentin formation was initiated throughout the entire transplanted pulp area. In the experimental cases at 7 and 14 days, the entire transplanted area had become osteodentin except for a thin fibrous layer under the 4-META resin. These results suggested that the components of 4-META resin such as MMA and 4-MET (A), which guide the polymerization, might cause degeneration of, but not disturb, the wound healing of the pulp tissue.

Acrylic Resins↗
PubMed1999

Pleomorphic adenoma with nuclear palisading arrangement of modified myoepithelial cells: histopathologic and immunohistochemical study.

Pleomorphic adenomas with a nuclear palisading arrangement of spindle-shaped modified myoepithelial cells (MMCs), suggesting the appearance of palisading leiomyoma or Antoni's A type of neurilemmoma, are quite rare, and its cytologic nature has been poorly understood. This paper reports histologic and immunohistochemical findings of palisading MMCs in two cases of pleomorphic adenoma. Histologically, foci of spindle-shaped MMCs with nuclei in a palisading arrangement were scattered in the myxoid areas. Near the large foci of spindle-shaped MMCs with nuclear palisading arrangements, tiny foci of spindle-shaped MMCs forming nuclear palisading or rosette-like arrangements were seen. Such nuclear palisading arrangements of MMCs were suggestive of differentiation or transformation of MMCs into cells that were more smooth muscle in nature, supported by occasional existence of palisading leiomyoma in the myometrium and gastrointestinal tract. However, immunohistochemical findings of palisading MMCs in pleomorphic adenoma were similar to those of non-palisading MMCs, and showed no evidence of smooth muscle differentiation; neither palisading nor non-palisading MMCs in pleomorphic adenoma expressed desmin, muscle specific actin (HHF-35), alpha smooth muscle actin, or myoglobin. The biologic significance and formative mechanism of nuclear palisading arrangement of MMCs in pleomorphic adenoma could not be determined in the present study. However, if the MMCs with nuclear palisading arrangements in pleomorphic adenoma, presented here, are aspirated for cytologic diagnosis or are included in a small biopsy specimen, the correct diagnosis of pleomorphic adenoma may be confused by a suspicion of myogenic or neurogenic tumor.

Adenoma, Pleomorphic↗