<ORIGINAL ARTICLE>Tartrate-resistant acid phosphatase activity induced by pre-incubation with tartrate in mouse embryonic mandibles

The present study used mouse embryonic mandibles to examine the characteristics of tartrate in tartrate-resistant acid phosphatase (TR-ACPase) histochemistry. Short-term incubation (30 min) in substrate-containing reaction medium showed intense and specific activity of TR-ACPase only in a small number of mononuclear cells, presumably pre-osteoclasts, present around a population of differentiating osteoblasts. Pre-incubation with tartrate and subsequent incubation of reaction medium resulted in slightly increased intensity in the preosteoclasts and also weak enzyme activity in other cells such as oral and dental epithelia, osteoblasts, and chondrocytes of Meckel\u27s cartilage. Pre-incubation with tartrate and subsequent incubation with reaction medium may result in overestimation of the histochemical products. Therefore short-term incubation is important to estimate the enzyme activity exactly in TR-ACPase histochemistry. especially in osteoblasts

<ORIGINAL>Appearance and distribution of osteoclast precursors and the morphological change during mouse mandibular osteogenesis

The appearance and distribution of osteoclast precursors and the morphological change of the precursors were examined during mouse mandibular osteogenesis, using enzyme histochemistry of tartrate-resistant acid phosphatase (TRAPase). Osteogenic tissue was not observed in the prospective region of the mandibles at embryonic day 12 (E12), but TRAPase-positive cells often existed in the region. Immature osteoblasts were seen as a population in E13 mandibles, and a thin layer of bone matrix had been formed at the central part of the osteogenic region in E14 mandibles. A number of TRAPase-positive osteoclast precursors were tandemly localized along the region. At these stages, the TRAPase-positive cells were oval and round in the vicinity of blood vessels, but at an earlier stage of the osteogenesis, the positive cells extended long processes towards the interspace between the osteoblasts. The present results demonstrated the morphology characteristic of the TRAPase-positive osteoclast precursors during osteoclast differentiation, suggesting the possibility that there is a cell-cell interaction between the osteoclast precursors and the osteoblasts in vivo

Susceptibility of tenascin to degradation by matrix metalloproteinases and serine proteinases

AbstractThe degradation of tenascin purified from human melanoma cells was examined by treatment with matrix metalloproteinases (MMPs) and serine proteinases. Among eight different types of proteinases examined, MMP-1, -3, and -7, cathepsin G and leukocyte elastase could digest tenascin, but MMP-2, MMP-9 and thrombin did not. This suggests that tenascin may be readily catabolized by extracellular matrix-degrading proteinases found in the pathophysiological conditions

<ORIGINAL ARTICLE>Localization of anti-monocyte/macrophage antibody-positive cells in periodontal tissue of rat maxillary molars after orthodontic tooth movement

To examine the localization of monoclonal anti-monocyte/macrophage (ED1) and macrophage (ED2) antibody-positive cells in periodontium, rat maxillary molar teeth were moved by insertion of band materials. The orthodontic tooth movement was elicited for 5 days, and paraffin-embedded maxillary teeth were stained by fluorescent immunocytochemistry and observed using a confocal laser scanning microscope. The localization of ED1-positive mononuclear cells in the experimental teeth was little different from that in the controls. While ED2-positive mononuclear cells were located throughout the periodontium on the distalside of controls, the number of positive cells decreased on the pressure side of the treated teeth. The present study suggested that most of the immunoreactive mononuclear cells on the distal side of controls are macrophages, while the positive cells on the pressure side of the experimental teeth are osteoclast precursors and a small number of macrophages

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Two radiopaque lines demonstrated in the mandibular molar regions have customarily been termed to be "external oblique line" and "internal oblique line". But, even in the textbooks for dental radiology, some defferences are seen in the explanation of them. Therefore, the textbooks for oral anatomy, dental radiology, complete prodentics and dental anesthesia in which the terms "external oblique line" and "internal oblique line" were reviewed. The results show that the "external oblique line" and "internal oblique line" are homonymic words derived by the difference of the purpose to use. If one uses such names properly in education, students must learn the different meanings doubly or threefold, and it might obstruct the commonness between these subjects

Dentinogenesis in the incisor teeth of adult rats after persisting daily overdosage of 1α-hydroxyvitamin D3,with special reference to osteodentin formation

雄ラット20匹を4群に分け,1群は対照群とし,実験群に0.1, 0.5, 2.5 μg/kgの1 α-OH-D3を30日間連続経口投与した.上顎切歯を材料とし,ビタミンD3の象牙質形成に及ぼす影響,特にOsteodentin形成を光顕と電顕で観察した.1)ビタミンD3低投与群では変化はみず,高投与群で著明な形態的変化を認めた.2)象牙質と象牙芽細胞の配列の乱れは最初に基底側1/3にみ,切端に向い周期的に生じる.3)象牙質と象牙芽細胞の配列が乱れる部位では,象牙前質が消失し,退行性の象牙芽細胞が多数出現し一部は不規則な象牙質中に埋入される.4)象牙芽細胞の配列が乱れる部位では象牙芽細胞直下の歯髄側に前象牙質様の構造物が出現し,これはコラーゲン基質から成る.5)上記の前象牙質様構造物に接する象牙芽細胞の近位端には象牙芽細胞の突起が出現し,基質小胞様の構造物が出現する.以上はビタミンD3の過剰投与により,周期的に象牙芽細胞に退行性変化が生じ象牙芽細胞は自ら分泌した基質中に埋入しOsteodentinを形成する可能性を示唆した雄ラット20匹を4群に分け,1群は対照群とし,実験群に0.1, 0.5, 2.5 μg/kgの1 α-OH-D3を30日間連続経口投与した.上顎切歯を材料とし,ビタミンD3の象牙質形成に及ぼす影響,特にOsteodentin形成を光顕と電顕で観察した.1)ビタミンD3低投与群では変化はみず,高投与群で著明な形態的変化を認めた.2)象牙質と象牙芽細胞の配列の乱れは最初に基底側1/3にみ,切端に向い周期的に生じる.3)象牙質と象牙芽細胞の配列が乱れる部位では,象牙前質が消失し,退行性の象牙芽細胞が多数出現し一部は不規則な象牙質中に埋入される.4)象牙芽細胞の配列が乱れる部位では象牙芽細胞直下の歯髄側に前象牙質様の構造物が出現し,これはコラーゲン基質から成る.5)上記の前象牙質様構造物に接する象牙芽細胞の近位端には象牙芽細胞の突起が出現し,基質小胞様の構造物が出現する.以上はビタミンD3の過剰投与により,周期的に象牙芽細胞に退行性変化が生じ象牙芽細胞は自ら分泌した基質中に埋入しOsteodentinを形成する可能性を示唆し

Matrix Mineralization as a Trigger for Osteocyte Maturation

The morphology of the osteocyte changes during the cell's lifetime. Shortly after becoming buried in the matrix, an osteocyte is plump with a rich rough endoplasmic reticulum and a well-developed Golgi complex. This “immature” osteocyte reduces its number of organelles to become a “mature” osteocyte when it comes to reside deeper in the bone matrix. We hypothesized that mineralization of the surrounding matrix is the trigger for osteocyte maturation. To verify this, we prevented mineralization of newly formed matrix by administration of 1-hydroxyethylidene-1,1-bisphosphonate (HEBP) and then examined the morphological changes in the osteocytes in rats. In the HEBP group, matrix mineralization was disturbed, but matrix formation was not affected. The osteocytes found in the unmineralized matrix were immature. Mature osteocytes were seen in the corresponding mineralized matrix in the control group. The immature osteocytes in the unmineralized matrix failed to show immunoreactivity with anti-sclerostin antibody, whereas mature osteocytes in the mineralized matrix showed immunoreactivity in both control and HEBP groups. These findings suggest that mineralization of the matrix surrounding the osteocyte is the trigger for cytodifferentiation from a plump immature form to a mature osteocyte. The osteocyte appears to start secreting sclerostin only after it matures in the mineralized bone matrix. (J Histochem Cytochem 56:561–567, 2008