Biomedical subjects

T Domon

Publications and source records attributed to T Domon.

At least 37 records · Page 2Linked to original sources

PubMed2000

Ultrastructural study of the root dentine surface resuming resorption on human deciduous teeth.

Resorption of deciduous teeth is not continuous, but alternates with periods of repair or rest. Dentine surfaces in periods of rest or repair resume resorption by odontoclasts during physiological root resorption of the deciduous teeth. However, no observations of such dentine surfaces have been shown. The characteristic feature of the dentine surfaces resuming resorption remains unknown. Tartrate-resistant acid phosphatase activity (TRAP) was detected on human deciduous teeth. The root resorbing surfaces on these teeth were photographed with a whole-mount light microscope, and the photographed areas were serially sectioned into 0.5 micron semithin sections. Preodontoclasts and odontoclasts were three-dimensionally reconstructed. On root resorbing surfaces, areas with small scattered TRAP-positive cells were observed among areas with many TRAP-positive resorbing odontoclasts and TRAP-negative areas. The sections showed that areas with small scattered TRAP-positive cells have features similar to those of TRAP-negative areas, but there were three kinds of characteristic TRAP-positive cells: preodontoclasts, odontoclasts forming small lacunae, and preodontoclasts, and odontoclasts with cytoplasmic processes extending to the dentine surface, which is covered with cells. These results suggest that the areas with small scattered TRAP-positive cells could be at the stage of resuming resorption, and show that the presence of preodontoclasts and odontoclasts with cytoplasmic processes extending to the covered dentine surface is a characteristic feature of the dentine surface at this stage.

Acid Phosphatase↗

PubMed2000

The structure of the cemento-dentinal junction in rat molars.

The cemento-dentinal junction was observed in the acellular and cellular cementum of rat molars by light and scanning electron microscopy. Scanning electron microscopy, combined with NaOH maceration, was used to observe the fibrous architecture directly in this region. Light microscopy revealed that the cemento-dentinal junction contains fewer collagen fibrils and more proteoglycans than the cementum and dentin. Scanning electron microscopy also showed that fibril intermingling is found only in some regions of the fibril-poor junction in macerated specimens. Prolonged maceration breaks down the cemento-dentinal junction in spite of the fibril intermingling. Only macerated specimens showed detachment here. It was established that NaOH maceration removes interfibrillar substances effectively, and does not damage the fibril structure or architecture. This suggests that the adhesion of proteoglycans is more important than fibril intermingling for preserving the cemento-dentinal attachment in the rat molar.

Animals↗

PubMed2000

The fibrillar structure of cementum and dentin at the cemento-dentinal junction in rat molars.

The cemento-dentinal junction was examined in demineralized rat molars with complete roots by scanning electron microscopy combined with NaOH maceration. It is established that the NaOH maceration removes interfibrillar substances and cells from connective tissues selectively without structural damage to collagen fibrils. The cementum was detached from the dentin by the maceration. The inner cementum surface facing the dentin and the outer dentin surface facing the cementum were observed. In acellular cementum, both the outer dentin surface and the inner cementum surface had a smooth appearance. There was little indication of fibrils intermingling between dentin and cementum. In contrast, both the inner cementum surface and outer dentin surface in cellular cementum had an uneven appearance due to the irregular arrangement of collagen fibrils. Point-like protrusions of fibril bundles were observed on both surfaces. Some (not all) of these point-like protrusions appeared to correspond to places of fibrillar intermingling between dentin and cementum.

Animals↗

PubMed2000

The fibrous structure of the cemento-dentinal junction in human molars shown by scanning electron microscopy combined with NaOH-maceration.

The cemento dentinal junction was studied in acellular and cellular cementum of human mandibular third molars by scanning electron microscopy combined with NaOH-maceration. Scanning electron microscopy with NaOH-maceration was applied to observe the fibrous structure in detail through long sections of the cemento-dentinal junction. In macerated specimens, the cemento dentinal junction was a fibril-poor groove. Some cemental fibrils or fibril bundles penetrated the groove and appeared to intermingle with dentinal fibrils. Prolonged maceration caused detachment of the cemento-dentinal junction irrespective of fibril intermingling allowing observation of the inner cementum surface facing the root dentin. Observations suggested that the fibril intermingling was point-like and present only in places at the cemento-dentinal junction. It was established that NaOH-maceration removes interfibrillar substances effectively in connective tissues and does no damage to the collagen fibril structure and architecture. This study showed the 3-dimensional fibrous structure of the cemento-dentinal junction in human mandibular third molars, and suggested that interfibrillar adhesive substances are more important than the fibril intermingling for the cemento-dentinal attachment.

Caustics↗

PubMed2000

The fibrillar structure of cement lines on resorbed root surfaces of human teeth.

The cement lines between reparative cementum and resorbed dentin or cementum in human teeth were observed by light microscopy and scanning electron microscopy combined with NaOH maceration. The NaOH maceration was used to remove interfibrillar substances and to observe the fibrillar architecture of the cement lines directly. Light microscopy showed that the cement lines were rich in proteoglycans with mucopolysaccharides, but deficient in collagen fibrils. The cement lines were artificially broken after treatment with hyaluronidase, which digests some of the mucopolysaccharides, but digests no collagen fibrils. Scanning electron microscopy showed that fibril intermingling occurred only in some places between reparative cementum and resorbed tissue. These findings suggested that the proteoglycans in cement lines mediate the attachment between new and old mineralized tissue.

Cytological Techniques↗

PubMed1999

Changing myoepithelial cell distribution during regeneration of rat parotid glands.

The distribution of the myoepithelial cells during regeneration of the rat parotid gland after atrophy induced by one week of parotid duct ligation was investigated by immunohistochemistry for actin and transmission electron microscopy (TEM). Immunohistochemically, residual ducts were surrounded by actin-positive cells when clips were removed from the duct. Three days later, most of the newly formed acini originating from the residual ducts were also embraced by actin-positive cells. After 10 days, actin-positivity tended to be seen as dots around acini that decreased in number day by day. On day 21 actin-positive cells mainly surrounded intercalated ducts with only a few positive reactions identified at the acinar periphery. Electron microscopically, residual ducts and newly formed acini were peripherally embraced by myoepithelial cells before day 5. After day 7, shift of myoepithelial cells from the periphery of acini to the duct-acinar junctional region was identified. Then few myoepithelial cells were identified at the periphery of acini. These observations indicate that myoepithelial cells migrate from the acinar periphery to the duct-acinar junctional region during rat parotid regeneration, and that such behaviour is closely related to that seen during rat parotid development.

Actins↗

PubMed1999

The structure and function of the cemento-dentinal junction in human teeth.

The structure and function of the cemento-dentinal junction were studied in human molars by light and electron microscopy. The cemento-dentinal junction was an approximately 1-3-micron-thick layer full of proteoglycans with mucopolysaccharides but containing fewer collagen fibrils than the root dentin and cementum. In places, cemental fibrils crossed the cemento-dentinal junction. These fibrils appeared to intermingle with dentinal fibrils. By enzymatic treatment of decalcified specimen with hyaluronidase and trypsin, the cemento-dentinal junction decreased or lost staining affinity to toluidine blue. Prolonged treatment caused the separation of cementum from the root dentin during routine histological processes. These data suggest that the adhesion of proteoglycans is more important than the intermingling of dentinal and cemental fibrils for the cemento-dentinal attachment.

Adolescent↗

PubMed1998

Increase in odontoclast nuclei number by cell fusion: a three-dimensional reconstruction of cell fusion of human odontoclasts.

Osteoclasts and odontoclasts are known to increase their nuclear number by fusion of mononuclear precursors. However, the pattern of fusion remains morphologically unclear. One lower right deciduous canine of an 8-year-old male was investigated. Tartrate-resistant acid phosphatase activity (TRAP) positive cells on the resorbing surface of the tooth were serially sectioned into 0.5 microm-thick semithin sections. The sections were photographed, and cells possessing a light microscopic brush border facing a resorptive lacuna were identified as odontoclasts. Fourteen odontoclasts appearing as a continuous figure of cellular membrane between cells on one section were three-dimensionally reconstructed using NIKON COSMOZONE 2SA. A criterion for fusion was established in this study, requiring that there must be two or more nucleated cells which contacted each other at one site only in the three-dimensional reconstruction. Among 14 reconstructed cells, 10 odontoclasts satisfied the criterion for fusion. The observations of the three-dimensional structures of these odontoclasts showed that mononuclear and multinucleated odontoclasts participated in fusion. Cell fusion occurred between resorbing odontoclasts and cells not forming lacunae, and between resorbing odontoclasts. A case of odontoclastic fusion among three cells was also observed. The results establish that fusion resulting in multinucleation occurred among various odontoclasts with different numbers of nuclei including mononuclear odontoclasts.

Cell Fusion↗

PubMed1998

The structure and function of periodontal ligament cells in acellular cementum in rat molars.

To elucidate the structure and function of periodontal ligament cells at the periodontal ligament-cementum interface in advanced acellular cementogenesis, the cervical regions of molars in rats aged 6 weeks were observed by light and electron microscopy. The light and transmission electron microscopy showed the periodontal ligament cells to be elongated between dense, well-developed principal fibers. The transmission and scanning electron microscopy showed that these cells extended wing-like projections from the lateral surface, forming cylindrical compartments surrounding the principal fibers. In addition, finger-like projections extended toward the cementum from the cementum-facing ends. The main results suggest the following: at the periodontal ligament-cementum interface, the periodontal ligament cells maintain the architecture of the principal fibers by means of extracellular compartments. The arrangement of finger-like projections results in the formation of acellular cementum containing only Sharpey's fibers as a fibrous component.

Animals↗

PubMed1998

The regulation of fiber arrangement in advanced cellular cementogenesis of human teeth.

This study observed cellular cementum in fully formed human premolars by light and electron microscopy to elucidate how cementoblasts regulate the fiber arrangement in cementum. Cementoblasts had wing-like processes encircling the principal fibers, where Sharpey's fibers were dense. On the cementum-facing side, wing-like processes were segmented into finger-like processes in parallel with the cementum surface. Observations suggested that with the segmentation intrinsic fibers appeared around principal fibers in close association with finger-like processes. Where Sharpey's fibers were few or absent, where intrinsic fibers were the main fibrous element of the cementum, cementoblasts had only few or no wing-like processes, but had finger-like processes not associated with the wing-like processes on the cementum-facing side. On the basis of the origin of the finger-like processes the main results suggest that there are two kinds of cementoblasts: one has finger-like processes associated with wing-like processes and secretes intrinsic fibers from the finger-like processes to incorporate the principal fibers for tooth support. The second type has finger-like processes not associated with wing-like processes, this type secretes intrinsic fibers from the finger-like processes to adjust the cementum thickness.

Adult↗

PubMed1997

Mononuclear odontoclast participation in tooth resorption: the distribution of nuclei in human odontoclasts.

Osteoclasts and odontoclasts have been considered multinucleated giant cells which resorb hard tissue by ruffled borders. Recently, the authors reported the presence of a mononuclear osteoclast and odontoclast with a ruffled border. However, the relative frequency of such cells and the distribution of the number of nuclei including mononuclear cells in them have not been elucidated. Six human deciduous teeth were used in this study. After fixation and decalcification, tartrate-resistant acid phosphatase (TRAP) activity was detected with the azo dye method, and then TRAP-positive cells were observed on resorbing areas of teeth by light microscopy. The cells for investigation were serially sectioned by semithin sections to observe the presence of resorptive lacuna and the number of nuclei. The TRAP activity was detected in both multinucleated and mononuclear odontoclasts from serial semithin sections, and 242 TRAP-positive cells which formed lacunae on dentin were investigated to determine the frequency distribution of the number of nuclei. The mean number of nuclei per cell was 5.3, and median was 4. Only 2.9% of odontoclasts were mononucleus and 93.8% had 10 or fewer nuclei. The majority of odontoclasts forming lacunae on the dentin were cells with 10 or fewer nuclei, and mononuclear odontoclasts participated in human deciduous tooth resorption together with multinucleated ones.

Acid Phosphatase↗

PubMed1997

Formation of an alternate lamellar pattern in the advanced cellular cementogenesis in human teeth.

The formation of an alternate lamellar pattern in the advanced stage of cellular cementogenesis in human molars was examined by light and electron microscopy. In longitudinal ultrathin sections, longitudinally oriented intrinsic fibril bundles appeared in close and parallel association with slender processes of cementoblasts on the cementum. Where transversely oriented intrinsic fibril bundles appeared, cementoblasts formed indentations to enclose the fibril bundles. Cytoplasmic fragments were also enclosed in the indentations. Scanning electron microscopy indicated that cementoblasts have developed two types of processes on their cementum-facing side - ridge- and finger-like. The cementoblasts formed groove-like compartments by ridge-like processes in cooperation with other cementoblasts. The compartments formed groups, and in each group the compartments were arranged in the same direction. The finger-like processes were arranged in parallel with the ridge-like processes in the compartments. These observations suggest that: (1) slender processes and cytoplasmic fragments are longitudinally and transversely cut finger-like processes, respectively; (2) the cellular indentations are transversely cut groove-like compartments; (3) the cementoblasts regulate the intrinsic fiber arrangement by the two types of processes; (4) the cementoblasts move the two types of processes synchronously and periodically to cause an alternate change in the intrinsic fiber arrangement. This dynamic sequence results in the alternate lamellar pattern of cellular cementum.

Collagen↗

PubMed1997

Regeneration of myoepithelial cells in rat submandibular glands after yttrium aluminium garnett laser irradiation.

The regeneration of myoepithelial cells in rat submandibular salivary gland after partial irradiation with yttrium aluminium garnett (YAG) laser was investigated. The irradiated glands were examined immunohistochemically for actin, histochemically for alkaline phosphatase (ALP), and by transmission electron microscopy (TEM). In control glands, myoepithelial cells were positive for actin and ALP. Electron microscopically, the positive reaction for actin was associated with the myofilaments of myoepithelial cells, and the plasma membrane of myoepithelial cells was positive for ALP. One day after YAG laser irradiation, the irradiated region was necrotic. By 5 days, duct-like structures and epithelial clusters were observed at the interface between the necrotic zone and the remaining undamaged glands; immature acini appeared after 7 days. No reaction in duct-like structures or epithelial clusters to actin or ALP was recognizable by 5 days. However, at 7 days, actin and ALP-positive spindle cells appeared at the periphery of the duct-like structures and immature acini. After 10 days, both actin-positive and ALP-positive cells increased in number. These observations indicate that during regeneration, actin-positive and ALP-positive cells regenerate myoepithelial cells, and it is suggested that this differentiation to myoepithelial cells is closely related to that of luminal to acinar cells. In addition, TEM observations indicate that regenerated myoepithelial cells originated from the basal cells of duct-like structures.

Actins↗

PubMed1996

Cellular cementogenesis in rat molars: the role of cementoblasts in the deposition of intrinsic matrix fibers of cementum proper.

The formation of intrinsic fibers was examined in the advanced stage of rat cellular cementogenesis by light and electron microscopy. Using scanning electron microscopy, cementoblasts showed wing-like processes, partly encircling principal fibers. At the cementum-facing side of the cells these processes showed segmentation into finger-like processes, arranged in parallel with the cementum surface. Transmission electron microscopy showed many cytoplasmic fragments around intrinsic fibers at the cementum surface. These fragments contained microtubules and collagenous secretory granules that were arranged in parallel with the cementum surface and the intrinsic fibers. The wing-like processes contained microtubules and secretory granules that were arranged perpendicularly to the cementum surface and in parallel with the principal fibers. These observations suggest that: (1) the cytoplasmic fragments are cross-sectioned finger-like processes; (2) cementoblasts secrete intrinsic fibers from the finger-like processes and additional principal fibers from the wing-like processes; (3) cementoblasts constantly shorten their wing-like processes by forming finger-like processes. This development starts at the side facing the cementum and proceeds towards the periodontal ligament. With the segmentation, the cementoblasts change the arrangement of secretory granules to secrete intrinsic fibers around preformed principal fibers.

Animals↗

PubMed1994

Electron microscopic and histochemical studies of the mononuclear odontoclast of the human.

BACKGROUND: Osteoclasts and odontoclasts are multinucleated giant cells which resorb hard tissue by the ruffled borders. Recently, the authors reported the presence of a mononuclear osteoclast with a ruffled border in vitro. However, its presence in vivo has not been shown. To demonstrate the presence of a mononuclear odontoclast in humans, the present study used human deciduous teeth. METHODS: After fixation and decalcification, tartrate-resistant acid phosphatase (TRACPase) activity was detected with the azo dye method, and then TRACPase-positive cells were observed on resorbing areas of teeth. TRACPase-positive cells could be distinguished from other cells by light microscopy, and the cells for investigation were serially sectioned by alternating semithin and ultrathin sections to observe their ultrastructure and three-dimensional organization. RESULTS: TRACPase activity was detected in both multinucleated odontoclasts and a mononuclear cell from serial sections. By electron microscopy, most of the multinucleated odontoclasts had ruffled borders and clear zones. A mononuclear TRACPase-positive cell with a ruffled border and clear zone was reconstructed three-dimensionally by NIKON COSMO-ZONE 2SA. The reconstruction showed that this cell had one irregularly shaped nucleus and a wide ring-shaped clear zone and a small ruffled border. Under the ruffled border, this cell formed a small lacuna on the dentin surface. The results suggested that this cell was a mononuclear odontoclast. CONCLUSIONS: The present study concludes that cells with ruffled borders and clear zones observed by transmission electron microscopy can be identified as odontoclasts or osteoclasts irrespective of the number of nuclei.

Acid Phosphatase↗

PubMed1994

Comparative study of the initial genesis of acellular and cellular cementum in rat molars.

The initial genesis of acellular and cellular cementum was examined in rat molars by light and electron microscopy. Before root dentinogenesis, flattened dental follicle cells formed compartments by regularly arranged cellular processes which demarcated collagen fibril bundles oriented in parallel with the root long axis in both of the two kinds of cementum. After this stage, compartments disappeared from the dental follicle cells, which became elongated and polarized, with the cytoplasmic side facing toward the root surface in the acellular cementogenesis. Fibril bundles, oriented in parallel with the root long axis, decreased in number, and principal fibers appeared. Some principal fibers were attached on the first acellular cementum. Observations suggested that the fibril bundles, which had been oriented in parallel with the root long axis, were reoriented to merge into the principal fibers. In cellular cementogenesis, the dental follicle cells continued to hold the fibril bundles in cellular compartments. The regular processes were transformed into randomly oriented, finger-like processes. At the same time, fibers, which may be secreted from the finger-like processes, appeared around the preformed fibril bundles oriented in parallel with the root long axis. The different cellular behavior may result in the different fiber arrangement of acellular and cellular cementum.

Age Factors↗

PubMed1991

Electron microscopic and histochemical studies of the mononuclear osteoclast of the mouse.

Osteoclasts collected from the long bones of mice were cultured on dentin slices. To identify osteoclasts, the tartrate-resistant acid phosphatase (TRACPase) activity of cultured cells was histochemically examined by the azo dye method. The TRACPase-positive cells could be distinguished from other cells by light microscopy. The cells were sectioned by alternating semithin and ultrathin sections to observe their ultrastructure and three-dimensional structure. TRACPase activity was detected both in multi-nucleated osteoclasts and in mononuclear cells. Most of the mononuclear TRACPase-positive cells had features similar to preosteoclasts. A mononuclear TRACPase-positive cell was a ruffled border and clear zone was reconstructed three-dimensionally by NIKON COSMOZONE 2SA. The reconstruction showed that this cell possessed a large clear zone and small ruffled border. Under the ruffled border, no lacuna was apparent; but there was disruption of the dentin surface. The results suggest that this cell was a mononuclear osteoclast and that it might have been in the process of making a new lacuna.

Acid Phosphatase↗

PubMed1991

The three-dimensional structure of the clear zone of a cultured osteoclast.

Osteoclasts collected from long bones of newborn mice were cultured on dentine slices. Then, osteoclasts were sectioned by alternating semithin and ultrathin sections, and the three-dimensional reconstruction was made by the serial semithin sections. By this method, the present study showed first the three-dimensional structure of an osteoclast, especially the clear zone. A reconstructed osteoclast with complicated contours shifted from the lacuna, and its clear zone was a ring-shaped structure. By TEM, a new small lacuna was formed under the ruffled border, and the clear zone could be further classified into three types. The present study suggested that the synthetic observations of both three-dimensional structure and ultrastructure by transmission electron microscopy were necessary to determine whether the osteoclast was resorbing or migrating. According to these observations, the reconstructed osteoclast seemed to be migrating.

Animals↗