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T Domon

Publications and source records attributed to T Domon.

43 records · Page 3Linked to original sources
PubMed1990

Histochemical, ultrastructural, and electron microprobe analytical studies on the localization of calcium in rat incisor ameloblasts at early stage amelogenesis.

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.

Ameloblasts↗
PubMed1990

[Ultrastructural study of osteoclasts: reference to the three-dimensional structure of cultured osteoclasts].

The present study aims to understand the three-dimensional structure of the osteoclast during locomotion. The osteoclasts were gained from the bone marrow cells of new born ddY mouse. These osteoclasts were seeded onto dentine slices and then cultured for 48 hrs. The cells were examined using transmission electron microscopy. The osteoclast seen in this study had an irregular outline and had shifted from previously formed lacunae. This cellular extension was seemed to be lamellipodia. According to these results, the osteoclasts seen in present study were determined to have been during locomotion. The ruffled border of the osteoclast was composed of both finger-like processes and plate-like ones. The plate-like processes were observed in the almost newly formed lacuna. The complicated interwoven membranous gatherings were observed at two extensive areas of the cell body situated in the previously formed lacuna. It is postulated that these structures are related to the incoming and outgoing of the cell membranes of the ruffled border in accordance with cell locomotion.

Animals↗
PubMed1990

Time-related changes in the distribution of 45Ca in the developing enamel of rat incisors as revealed by radioautography.

The distribution and movement of calcium through the enamel organ and into the forming enamel was examined by means of quantitative 45Ca radioautography in rat incisors. Dislocation of radiocalcium in the specimen was minimized during histologic and radioautographic processing by using rapid freeze/freeze-substitution and dry emulsion coating methods. At 30 sec. after the 45Ca injection, distinct peaks of radioactivity occurred in the connective tissue immediately adjacent to the enamel organ and the infranuclear compartment of secretory ameloblasts. An intense labeling also occurred in the superficial layers of the forming enamel extending 15 microns below the surface. The grain density in the distal cytoplasm of secretory ameloblasts increased at later time periods, whereas all other regions of the enamel organ showed a considerable decrease in radioactivity. The radioactivity in the infranuclear compartment of ameloblasts with numerous mitochondria remained relatively high at 2 min. but was abolished by 10 min. after the injection. The grain density in the enamel matrix became much stronger but the labeled regions only extended to 20, 30, and 40 microns below the surface at 2, 10, and 60 min. after the injection, respectively. The application of wet emulsion over similarly prepared sections caused a severe dislocation of radiocalcium in the specimens. These data confirmed the rapid penetration of systemically administered radiocalcium into the surface layers of forming enamel and its slow diffusion to the deeper layers. The time-related changes in relative grain densities at various regions of the ameloblasts support the coexistence of a relatively slow transcellular pathway for calcium through the secretory ameloblast layer.

Ameloblasts↗
PubMed1989

A three-dimensional reconstruction of the ruffled border of osteoclasts.

Osteoclasts of rat parietal bones were cultured and observed under the transmission electron microscope. The processes forming the ruffled border were studied three-dimensionally by a reconstruction method. After the observation of one plane (A-plane), serial ultrathin sections were made at right angles to the A-plane (B-plane). The processes of the ruffled border in the B-plane were reconstructed, based on the A-plane features, with Nikon Cosmozone 2S. The three-dimensional structure of the ruffled border of the osteoclasts was composed of two kinds of processes: one finger-like and the other plate-like. Both finger-like and plate-like processes branched from the stem processes projecting directly from the cell body. The long plate-like processes branched into secondary plates, extending perpendicularly to the bone surface.

Animals↗
PubMed1989

Studies of the clear zone of osteoclasts: immunohistological aspects of its form and distribution.

Bone marrow cells isolated from long bones of a ddY mouse were cultured on sperm whale dentin and examined by light, scanning and transmission electron microscopy. The osteoclasts in vitro showed essentially the same ultrastructures as in vivo. The distribution of actin in the osteoclasts was examined by an indirect immunofluorescent antibody method, which revealed a wide ring-shaped area under the fluorescence microscope. Transmission electron microscopy showed that the ring-shaped area corresponded to the clear zone. The clear zone and resorption lacunae were examined by a double illuminating method to determine the relationship between the clear zone and the lacunae, which could be divided into three types. The distribution and function of the clear zone are discussed.

Actins↗
PubMed1986

Electron microscope study of osteoclasts with special reference to the three-dimensional structure of the ruffled border.

Osteoclasts of rat mandibulars were observed under the transmission electron microscope with the aim of understanding the three-dimensional structure of the ruffled border. After observation, the same block was remounted to obtain sections of the same osteoclasts at right angles to the first sectioning plane. The structure of the ruffled border of osteoclasts was observed in the two perpendicular directions. The ruffled border of osteoclasts was found to consist of two areas: one being composed of finger-like processes and the other, of plate-like processes. The distribution of the two areas of processes in the ruffled border did not show any apparent regularity. Not all processes continued to the cell body; some processes (stem processes) did while others were interwoven branches of the stem processes. The finger-like processes were long and rod-shaped and a few of them branched directly from the stem processes. The plate-like processes were long and belt-like and showed complicated branching from the stem processes; some of these were possibly the long belt-like processes that were complicatedly folded up to make many secondary plates; they are arranged parallel to each other in a given area. The relationship between the structure and function of the ruffled border is discussed.

Animals↗