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Biomedical subjects

M Shimono

Publications and source records attributed to M Shimono.

At least 19 recordsLinked to original sources
PubMed1994

Electrophysiologic effects of intravenous E-4031, a novel class III antiarrhythmic agent, in patients with supraventricular tachyarrhythmias.

The electrophysiologic effects of intravenous (i.v.) E-4031, a new class III antiarrhythmic drug, were evaluated in 15 patients with supraventricular tachyarrhythmias [11 men, 4 women; mean age 41 +/- 19 (SD) years]. Eleven patients had accessory atrioventricular (AV) pathways, and 4 patients with no accessory pathway had paroxysmal atrial fibrillation. Electrophysiologic studies were performed before and after E-4031 administration (loading infusion 9 micrograms/kg for 5 min + maintenance infusion 0.15 microgram/kg/min). QT and QTc intervals were significantly prolonged by E-4031 from 0.40 +/- 0.03 (mean +/- SD) to 0.46 +/- 0.03 s (p < 0.0001) and from 0.43 +/- 0.03 to 0.49 +/- 0.04 s (p < 0.0001), respectively. No effect was observed on RR interval, PR interval, QRS duration, or AH and HV intervals. The effective refractory periods (ERPs) of the right atrium and ventricle were significantly prolonged from 219 +/- 27 to 236 +/- 26 ms (p < 0.001) and from 230 +/- 12 to 249 +/- 11 ms (p < 0.001), respectively. The ERP of the AV node did not change significantly after E-4031 administration. In patients with ventricular preexcitation, E-4031 significantly prolonged the ERP of the antegrade accessory pathway conduction from 340 +/- 101 to 362 +/- 106 ms (p < 0.001), but not retrograde accessory pathway conduction. AV reentrant tachycardia was induced in 3 of 11 patients with an accessory pathway, and repetitive atrial firing was induced in 3 of 4 patients with paroxysmal atrial fibrillation. E-4031 could prevent repetitive atrial firing in only 1 patient and could not prevent induction of AV reentrant tachycardia.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Freeze-fracture studies of salivary glands.

Freeze-fracture electron microscopy was employed to study the general morphology, membrane fusion during exocytosis, intercellular junctions in adult and developing salivary glands, and morphological changes of intercellular junctions in secretory stimulation and neoplastic disorders. Intramembranous particles distributed on plasma membranes and organelle-membranes were determined on the basis of particle density per unit. Relationship between distribution and density of particles and functions of membranes and organelles was discussed. Fused membranes took the form of smooth areas of intramembranous particles free on the PF face in the submandibular acinar cells induced by isoproterenol stimulation. The sequence of membrane fusion during secretion was discussed from these freeze-fracture observations. Tight junctions which limited solute diffusion between adjacent cells formed continuous belts around the juxtaluminal region of plasma membrane. Their permeability function was regulated by the number and the geometrical pattern of the tight-junctional strands. The junction appeared late during gestational life, and its development and morphology correlated with the establishment of electrochemical tightness. Similarity in the location and morphology between developmental and neoplastic conditions might indicate reflect the function and degree of cytodifferentiation in salivary gland. Gap junctions were detected as clusters of particles, representing voltage-regulated intercellular channels connecting adjacent cells. The junctions were developmentally regulated, and their size and frequency correlated with the functional activity and with cytodifferentiation in neoplastic disorders. Desmosomes, which appeared as round or elongated clusters of particles, provided the mechanical stability necessary to maintain the organization of acini and ducts.

Animals↗
PubMed1992

Osteogenic activity of cells from dental pulp, periodontal ligament, bone marrow and muscle in vitro: an ultrastructural study and alkaline-phosphatase activity.

Dental pulp, periodontal ligament, bone marrow and muscle tissue from the same rat were cultured in vitro in order to investigate their osteogenic activity by transmission electron microscope. Immunohistochemical methods with various antibodies were utilized and alkaline-phosphatase (ALPase) activities of these cells were also measured biochemically. Dental pulp cells were stellate in shape, showed an intense ALPase reaction, and had lipid-like droplets. Periodontal ligament cells were composed of spindle fibroblasts and epithelial cells. The former revealed a positive reaction for ALPase and possessed microfilaments. Bone marrow cells were spindle shaped, resembling fibroblasts, but some of them were similar to osteoblasts. Muscle cells were long, slender in shape, and showed no positive reaction for ALPase. The cells from pulp tissue showed the highest activity of ALPase, followed by periodontal ligament and bone marrow; there was no activity in muscle tissue. All the cells except the epithelial-like cells of the periodontal ligament and muscle cells were positive in reaction with ALPase which is a marker for osteogenic cells, and vimentin which is a marker of fibroblastic characteristics. Osteogenic activity and cellular differentiation of these cells were discussed.

Alkaline Phosphatase↗
PubMed1992

Repair dentinogenesis following transplantation into normal and germ-free animals.

UNLABELLED: The purpose of this study was to investigate the dentinogenesis of dental pulp tissue following transplantation and during regeneration in normal and germ free animals, as well as in vitro experiments. EXPERIMENTS: (1) Partial and complete exposure of dental pulp in germ free rats by removing the enamel and dentin of molars. (2) The central portion of rat incisor which consisted of pulp and pulp chamber were autografted into various tissues. (3) Explants of rat pulp tissue were cultured on dentin matrix. (4) Resin bonding agent, 4-META/MMA-TBB-O (Superbond), was placed directly on surgically-exposed dental pulp. RESULTS: (1) Dentin bridge formation was recognized at 5 days after operation in germ free rat. (2) The cut surface of the transplant exhibited dentin bridge at 7 days after implantation, and the thickness of the newly formed dentin increased gradually thereafter up to 30 days. (3) Cultured pulp cells had high alkaline phosphatase activity and bone- or dentin-like hard tissue was synthesized on the dentin matrix in vitro. (4) Dentin bridge formation was evident on the surgically-exposed dental pulp even after application of Superbond. From these results, it is suggested that pulp tissue has a high activity of dentinogenesis both in vivo and in vitro and 3 days is enough for pulp cells to express the odontoblast phenotype when inflammatory factors are not present.

Animals↗
PubMed1991

Vacuoles and vesicles in the rat junctional epithelium: a study with serial ultrathin sections.

To investigate whether the electron-lucent structures resembling vesicles and vacuoles in the rat molar junctional epithelium (JE) are in fact intracellular or extracellular, a study using serial ultrathin sections was carried out. In one series of experiments, the animals were not treated before the tissues were conventionally fixed; in another, anesthetized animals were administered horseradish peroxidase 20 min before the tissues were fixed. A large number of electron-lucent structures resembling vesicles and vacuoles were detected in both the peripheral and central cytoplasm of the JE localized at enamel and connective tissue sites. These were 70 to 800 nm in diameter and had a lucency similar to that of the extracellular space in untreated specimens fixed with conventional fixative. Serial ultrathin sectioning revealed that the electron-lucent structures gradually became part of the extracellular space in the following sections. There were also found in the middle portion of the cytoplasm in specimens pretreated with horseradish peroxidase. Numerous vacuole-like structures containing peroxidase-positive materials were found to be contiguous with the extracellular space. A small number of vesicles, also containing peroxidase-positive materials, did not appear in the previous or following sections. These results indicate that almost all electron-lucent structures resembling vesicles and vacuoles in the JE are located at the end of a long infolding, and are still in contact with the extracellular space.

Animals↗
PubMed1991

An ultrastructural study of the pocket epithelium in rats.

The purpose of the present study was to elucidate the biological characteristics of pocket epithelium in experimental periodontitis. Elastic rubber was inserted between the first and second molars of the left maxilla in rats. The rubber was removed after one week, and the animals were sacrificed one week after the removal, i.e., two weeks after the insertion. Sections of the teeth and surrounding tissues were examined by electron microscopy. Periodontal pockets were evident between the tooth surface and epithelial cell layer in the coronal portion. A large number of bacteria surrounded by neutrophils were observed on the cementum surface in the pocket; however, no bacterial invasion could be seen in the epithelium. The epithelial cells were spilt in the central portion by invasion of neutrophils, so that one or two layers of surviving epithelial cells were present on the cementum surface. Numerous fenestrations of capillaries were found in the connective tissue immediately below the epithelium. These results suggest that the pocket epithelium is formed by an intercellular split of the epithelium, not between cementum surface and epithelium.

Animals↗
PubMed1991

Ameloblastoma and its relationship to ameloblastic fibroma: their histogenesis based on an unusual case and review of the literature.

The present paper describes the relationship between ameloblastoma and ameloblastic fibroma deduced from a case diagnosed as "ameloblastoma combined with ameloblastic fibroma" arising in the mandible of a 5-year-old boy. Histologically, the tumor consisted of ameloblastoma in the central area and ameloblastic fibroma in the peripheral area; it clinically fits the characteristics of ameloblastic fibroma based on predominant age, manner of growth, and encapsulation. We reviewed the literature and discussed the relationship between ameloblastoma a ameloblastic fibroma in terms of tumorigenesis. It is assumed that ameloblastic fibroma can also be transformed into ameloblastoma, if the succeeding hard tissues are not formed, and the collagenous connective tissue substituting for the stromal mesenchymal tissue is formed by the inductive effect of the epithelial strands or other unknown factors. Several possibilities relative to the pathogenesis of ameloblastoma have been proposed by oral pathologists; however, to our knowledge, "ameloblastic fibroma can be transformed into ameloblastoma" has not hitherto been reported. The case we experienced here may be thought as an intermediate tumor pattern between ameloblastic fibroma and ameloblastoma.

Ameloblastoma↗
PubMed1991

Multiple dens invaginatus and cranio-vertebral abnormality.

This paper reports a case of multiple dens invaginatus (DI) bilaterally involving the maxillary central incisors, mandibular canines, and first premolars. The patient was a 11-year-old boy with steeple-head and mild mental retardation. The maxillary central incisors showed disproportionately large crowns and short roots. A roentgenographic survey of the skeletal system showed a sutural hyperostosis of the skull at bregma and a hypoplastic cervical vertebra. The review of the literature yields 6 cases of multiple DI, including the present case; these can be classified into 2 types, cases of only DI and cases of DI with anomalies of skeletal and other systems. Morphological differences in the central incisors are found between these 2 types.

Abnormalities, Multiple↗
PubMed1990

Blood coagulation findings and the efficacy of factor XIII concentrate in premature infants with intracranial hemorrhages.

Coagulation findings were examined in 55 cases of neonatal intracranial hemorrhages (ICH). Marked decreases of the platelet count, fibrinogen, factor XIII (F XIII) activity, were observed in these cases. However, the relatively mild increases in the alpha 2-plasmin inhibitor activity, alpha 2-plasmin inhibitor.plasmin complex and fibrin/fibrinogen degradation products level were observed and only about one third of the cases showed abnormal values. In consideration of these coagulation findings, fifty-eight cases of premature infants were randomly divided into a treated group with a F XIII concentrate and a non-treated group. Thirty cases were administered within 6 hours after delivery to investigate the preventive effects against intraventricular hemorrhages (IVH). Compared in frequencies between both groups limited to the cases with a high risk of IVH, the frequency in the treated group was two out of 13 (15.4%), significantly low (p less than 0.05), while it was six out of eight cases (75.0%) in the non-treated group. From these results it was concluded that a F XIII concentrate is effective in the prophylaxis of IVH in premature infants.

Blood Coagulation Tests↗
PubMed1990

Immunohistochemical study of basal cell adenoma in the parotid gland.

Basal cell adenoma of the parotid gland was studied with immunohistochemical methods. We observed cells in the tumor with positive reaction to polyclonal keratin, prekeratin, monoclonal PKK-1, polyclonal S-100 protein, monoclonal S-100 protein (alpha), secretory component, actin and laminin. However, no cells which stained positively with monoclonal KL-1, amylase, carcinoembryonic antigen, or epithelial membrane antigen were recognized. From these immunohistochemical results and our ultrastructural observations reported previously, we conclude that the cells constituting the basal cell adenoma are ductal, myoepithelial, and squamous cells but not secretory ones. It is also suggested that the origins of basal cell ademona as well as those of pleomorphic and clear cell adenoma are undifferentiated cells of intercalated duct.

Adenoma↗
PubMed1990

Congenital fibrous epulis: an undescribed fibrous lesion studied immunohistochemically and ultrastructurally.

Histological, immunohistochemical, and ultrastructural studies were done on a case of congenital gingival tumor with previously undescribed histopathological findings. The present lesion clinically mimicked a congenital epulis (congenital gingival granular cell tumor); however, it histologically consisted of densely packed collagen fibers forming numerous, well demarcated bundles surrounded by flattened cells with long slender cytoplasmic precesses. Immunohistochemical and ultrastructural findings suggested that these flattened cells embracing collagen bundles were fibroblastic in nature. Intracytoplasmic lysozomal granules could not be found in any cells of the lesion. Fibrous lesions similar to the present case have not been documented previously in the literature.

Female↗
PubMed1990

Induction of cartilage and bone formation by cells from explants of various oral tissues in vitro.

Cells with both osteogenic and chondrogenic capabilities from various connective tissues, dental pulp, periodontal ligament, bone marrow, muscle and subcutaneous connective tissues of the rat were investigated by using either mineralized or demineralized bone and dentin matrix in vitro. After 28 days of the cell culture, explant cells were examined histologically. Bone and cartilage formations were assessed by counting their numbers in serial sections. Induction of cartilage was occurred only in muscle. New bone formation was occurred most frequently in dental pulp, followed in order by bone marrow and periodontal ligament. These results suggest that osteogenic cells, dental pulp, bone marrow stromal cells, and periodontal ligament can not response to inductive stimuli such as the bone morphogenetic protein, BMP.

Animals↗
PubMed1989

A cytochemical study of dense granules in the rat junctional epithelium.

To clarify the details of intracytoplasmic granules in the junctional epithelium (JE) of the rat gingiva, phosphotungstic acid (PTA) staining, acid phosphatase cytochemistry and zinc iodide-osmium (ZIO) staining were carried out. Condensing granules containing homogeneous electron-dense materials, measuring about 260 nm in diameter, have been observed at the peripheral cytoplasm of the JE. These granules reveal PTA-positive, ZIO-positive and acid phosphatase-positive staining. These results indicate that the granules contain glycoprotein, phospholipid, lipoprotein and lysosomal enzymes. From their composition and morphology, it is suggested that these granules in the JE may contribute secretory function and secrete glycoproteins or glycolipids. Although it is unclear whether the dense granules correspond to membrane-coating granules by our staining methods, it is surmised that, if the dense granules can engage in establishment of the barrier function, then this role is impeded by the large intercellular space in the JE.

Acid Phosphatase↗
PubMed1989

Ultrastructure of basal cell adenoma in the parotid gland.

Basal cell adenoma of the parotid gland was studied with electron microscopy. The cells constituting this tumor were divided into three types of epithelial cells; ductal, myoepithelial, and squamous cells. The ductal cells, which were polygonal and cuboidal in shape, formed a sometimes distinct lumen. Glycogen were recognized in the cytoplasm of these cells. The myoepithelial cells appeared as plasmacytoid cells which contained abundant microfilaments. The squamous cells were characterized by the presence of well-developed tonofilaments and desmosomes. However, no secretory cells could be found, although small, electron dense granules were detected in the cytoplasm of the ductal cells. The granules were unlike secretory granules in their size, number and location. In consideration of the presence of secretory and myoepithelial cells, we reviewed previously reported literature and discussed the identification of secretory granules. From our and other reported results, we tentatively concluded that the electron dense granules described as secretory granules are not intrinsic secretory granules. Further, we suggested that the cell types and the histogenesis of basal cell adenoma are analogous to those of both pleomorphic and clear cell adenomas.

Adenoma↗
PubMed1989

An experimental study of osteogenesis in explants of rat dental pulp, periodontal ligament, bone marrow and muscle cells in vitro.

Cells of dental pulp, periodontal ligament, bone marrow and muscle derived from the same rat were cultured in vitro. Outgrowth of cells from these four explants were examined using phase-contrast microscope, light microscope and scanning electron microscope. Furthermore, cell lengths were measured randomly from SEM photographs and growth curves were plotted by calculating cell numbers. These cells had different morphology in both shape and length. The bone marrow cells showed the most rapid proliferation rate followed by muscle, periodontal ligament and most slowly in dental pulp cells.

Animals↗
PubMed1989

Regeneration of periodontal tissues following experimentally induced periodontitis in rats: a comparison of sucrose-rich and conventional diets.

The purpose of the present study is to elucidate influences of diet on periodontal regeneration following experimental periodontitis in rats. S-D rats were divided into two groups, which were fed either a conventional diet (group A) or a sucrose-rich diet (group B). Experimental periodontitis was produced by placement of elastic bands between maxillary molar teeth. After one week, the elastic bands were removed and the animals were sacrified by perfusion fixation with formalin immediately, 1, 3, or 5 days, or 1, 2, 3, 4, 6, or 8 weeks after the removal. Sections of the teeth and surrounding tissue were examined by light microscopy. Three days after the removal, in both groups, granulation tissues with many inflammatory cells were covered by epithelial cells; the attachment site to the root surface was located more apically than the cemento-enamel junction. Distinct periodontal pockets were formed by five days after the removal in group A. In group B, the infiltrations of inflammatory cells were more prominent than in group A. Six weeks after the removal in both groups, an epithelium which resembled long junctional epithelium rather than pocket epithelium became thicker. Eight weeks after the removal, the findings were similar to those of six weeks in group A. However, a severe inflammatory cell concentration was found in group B. These results suggest that periodontal wound healing is markedly influenced by diet, and that this experimental system is useful for studying dynamic changes in both pocket and long junctional epithelia.

Animals↗
PubMed1989

[Statistical study of epulis, especially in general pathology].

This report contains a statistical study of 874 cases of epulis diagnosed by the Department of Pathology of Tokyo Dental College from 1966 to 1986. 1. Of the 874 cases, 344 were epulis fibrosa, 217 were epulis granulomatosa, 78 were epulis fibromatosa, 74 were epulis fibrosaosteoplastica, 51 were epulis hemangiomatosa, 43 were epulis fibrosa teleangiectaticum, 15 were epulis cementoplastica, 14 were epulis osteomatosa, 3 were congenital epulis, 2 were giant cell epulis, and 1 was epulis cementomatosa. 2. As has been reported in other literature, there is a marked tendency for this condition to occur in females (331 male cases and 539 female cases). 3. Our data indicate a higher occurrence rate in people in their fifties, although the occurrence rates were similar in people in their twenties and in people in their sixties. 4. The epulis was observed most frequently in the maxillary incisor region.

Adolescent↗