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  • 1
    Electronic Resource
    Electronic Resource
    Formation of an alternate lamellar pattern in the advanced cellular cementogenesis in human teeth (1997)
    Springer
    Anatomy and embryology 196 (1997), S. 115-121 
    Details
    ISSN: 1432-0568
    Keywords: Key words Cellular cementum ; Intrinsic fiber ; Cementoblast ; Human tooth
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004290050084
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  • 2
    Electronic Resource
    Electronic Resource
    Some osteocytes released from their lacunae are embedded again in the bone and not engulfed by osteoclasts during bone remodeling (2000)
    Springer
    Anatomy and embryology 202 (2000), S. 119-128 
    Details
    ISSN: 1432-0568
    Keywords: Key words Serial sections ; Cutting cones ; Closing cones ; Bone cells ; Cement lines
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  It is generally accepted that osteocytes derive from osteoblasts that have secreted the bone around themselves. Osteocytes are cells embedded in the lacunae in the bone, and they are characteristically in contact with other cells by many slender cytoplasmic processes in canaliculi. During bone remodeling, many osteocytes in the bone are released from their lacunae by osteoclasts; however it remains unclear what happens to these released osteocytes. The cortical bone of the rat mandibular body was used in this study. Mandibles were fixed, decalcified, and then embedded in Epon 812. Specimens were sectioned in the frontal direction into serial 0.5 µm-thick semithin or 0.1 µm-thick ultrathin sections, and then examined by light or transmission electron microscopy. Cells that fitted in the osteocytic lacunae with canaliculi extending to the bone were identified as osteocytes in this study. Among many osteocytes released by osteoclasts in cutting cones, there were osteocytes half-released from their lacunae. These cells fitted in their lacunae with canaliculi extending to the bone and showed developed cell organelles in the cytoplasm. In closing cones, many osteocytes were situated in the bone away from cement lines; however, there were half-embedded osteocytes in the bone formed on cement lines. These cells fitted in their lacunae with canaliculi extending to the bone formed below cement lines and showed developed cell organelles in the cytoplasm. These results show that half-embedded osteocytes in closing cones derive from half-released osteocytes in cutting cones. Osteocytes encircled by osteo- clasts were sometimes observed on one section, but se-rial sections showed that these osteocytes fitted in their remaining lacunae in the bone on other sections. This shows that not all osteocytes released from their lacunae are engulfed by osteoclasts. Consequently, the present results suggests that some osteocytes released from their lacunae are embedded again in the bone and not engulfed by osteoclasts during bone remodeling.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004290000101
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  • 3
    Electronic Resource
    Electronic Resource
    Comparative study of the initial genesis of acellular and cellular cementum in rat molars (1994)
    Springer
    Anatomy and embryology 190 (1994), S. 521-527 
    Details
    ISSN: 1432-0568
    Keywords: Cellular cementum ; Acellular cementum ; Cementoblast ; Rat molar
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00190102
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  • 4
    Electronic Resource
    Electronic Resource
    Twisted plywood structure of an alternating lamellar pattern in cellular cementum of human teeth (2000)
    Springer
    Anatomy and embryology 202 (2000), S. 25-30 
    Details
    ISSN: 1432-0568
    Keywords: Keywords Cementoblasts ; Collagen fibrils ; Lamellar structure ; Maceration ; Scanning electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Human cellular cementum was examined by scanning electron microscopy to elucidate the manner of the alternate lamellar pattern forming the cellular cementum. Specimens were demineralized, trimmed with a freezing microtome, and treated by NaOH-maceration. This procedure was chosen to avoid artifacts in the fibril arrangement, and to study the fibrous architecture in detail. For comparison, non-demineralized, polished and HCl-etched specimens were also prepared. In the NaOH-macerated specimens, the lamellar pattern of the cellular cementum conformed to the twisted plywood principle of bone lamellation with a periodic rotation of matrix fibrils resulting in an alternating lamellar pattern. In contrast, matrix fibrils were irregularly arranged without indication of rotation of matrix fibrils in the polished and etched specimens. Our results suggest that polishing and etching procedures cause damage to fibrils and fibril arrangement.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00008241
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  • 5
    Electronic Resource
    Electronic Resource
    Cellular cementogenesis in rat molars: the role of cementoblasts in the deposition of intrinsic matrix fibers of cementum proper (1996)
    Springer
    Anatomy and embryology 193 (1996), S. 495-500 
    Details
    ISSN: 1432-0568
    Keywords: Cementoblast ; Extrinsic fiber ; Intrinsic fiber ; Periodontal ligament ; Rat molar
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00185880
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  • 6
    Electronic Resource
    Electronic Resource
    Histochemical, ultrastructural, and electron microprobe analytical studies on the localization of calcium in rat incisor ameloblasts at early stage amelogenesis (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    The @Anatomical Record 228 (1990), S. 123-131 
    Details
    ISSN: 0003-276X
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The enamel organs of rat incisors were separated from the enamel surface and processed for rapid freezing and freeze-substitution. A histochemical stain for calcium (GBHA) of thick Epon sections revealed intense calcium reactions in the secretory ameloblasts, exclusively in the tubulovesicular structures extending throughout their distal cytoplasm. Electron microscopy revealed a thin layer of amorphous material with clusters of electron-dense granules along the distal surface of secretory ameloblasts. In young secretory ameloblasts without typical Tomes' processes, a considerable number of mitochondria were located in the distal cytoplasm and contained numerous electron-dense granules. Similar dense granules as well as fine ribbon-like electron-dense figures, all containing significant amounts of calcium, were observed in some of the tubulovesicular structures at the distal end of these cells. A putative exocytotic figure of such dense granules was also observed. The electron-dense granules were rare in more differentiated ameloblasts with elongated Tomes' processes, which occasionally displayed ribbon-like figures in some of the tubulovesicular structures in the process region. No significant calcium peak was detected in the extracellular amorphous material, secretory granules, or along the lateral plasma membranes. These observations may imply high calcium concentrations in mitochondria and tubulovesicular structures in the distal cytoplasm of secretory ameloblasts relative to that of the cytosol and support the possible contribution of these organelles in secretory ameloblasts to cellular calcium regulation at least in the early stage of amelogenesis.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ar.1092280203
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  • 7
    Electronic Resource
    Electronic Resource
    Electron microscopic and histochemical studies of the mononuclear odontoclast of the human (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    The @Anatomical Record 240 (1994), S. 42-51 
    Details
    ISSN: 0003-276X
    Keywords: Osteoclast ; Ruffled border ; Mononuclear cell ; Multinucleation ; Electron microscopy ; Three-dimensional reconstruction ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: 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 declacification, 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 COSMOZONE 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. © 1994 Wiley-Liss, Inc.
    Additional Material: 24 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ar.1092400105
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  • 8
    Electronic Resource
    Electronic Resource
    Electron microscopic and histochemical studies of the mononuclear osteoclast of the mouse (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    American Journal of Anatomy 192 (1991), S. 35-44 
    Details
    ISSN: 0002-9106
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: 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 multinucleated 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.
    Additional Material: 21 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aja.1001920105
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