The ultrastructure of the transparent layer of carious dentin was investigated in relation to hardness. This layer was the deeper part of the intermediately-softened inner carious dentin. Intratubular deposition of fine crystals was initially observed at the uppermost layer of normal dentin, increased in the subtransparent layer, and gradually shifted to deposition of rhomboid-shaped crystals in the transparent layer. Crystals were not seen in the tubules in the overlying discolored layer. Softening, due to demineralization of the intertubular and peritubular dentin, started at the bottom of the subtransparent layer and increased in the outward direction.

We investigated the immunohistochemical localisation of types II and X collagen as well as the cytochemical localisation of alkaline phosphatase in the developing condylar cartilage of the fetal mouse mandible on d 14-16 of pregnancy. On d 14 of pregnancy, although no immunostaining for types II and X collagen was observed, alkaline phosphatase activity was detected in all cells in the anlage of the future condylar process. On d 15 of pregnancy, immunostaining for both collagen types was simultaneously detected in the primarily formed condylar cartilage. Alkaline phosphatase activity was also detected in chondrocytes at this stage. By d 16 of pregnancy, the hypertrophic cell zone rapidly increased in size. These findings strongly support a periosteal origin for the condylar cartilage of the fetal mouse mandible, and show that progenitor cells for condylar cartilage rapidly or directly differentiate into hypertrophic chondrocytes.

BACKGROUND AND PURPOSE:Although the prognostic value of perfusion MR imaging in various gliomas has been investigated, that in high-grade astrocytomas alone has not been fully evaluated. The purpose of this study was to evaluate retrospectively whether the tumor maximum relative cerebral blood volume (rCBV) on pretreatment perfusion MR imaging is of prognostic value in patients with high-grade astrocytoma.

Mandibular condylar cartilage is the principal secondary cartilage, differing from primary cartilage in its rapid differentiation from progenitor cells (preosteoblasts/skeletoblasts) to hypertrophic chondrocytes. The expression of three transcription factors related to bone and cartilage formation, namely Runx2, Osterix and Sox9, was investigated at the onset of mouse mandibular condylar cartilage formation by in situ hybridization. Messenger RNAs for these three molecules were expressed in the condylar anlage, consisting of preosteoblasts/skeletoblasts, at embryonic day (E)14. Hypertrophic chondrocytes appeared at E15 as soon as cartilage tissue appeared. Runx2 mRNA was expressed in the embryonic zone at the posterior position of the newly formed cartilage, in the bone collar and in the newly formed cartilage, but expression intensity in the newly formed cartilage was slightly weaker.Osterix mRNA was also expressed in the embryonic zone and in the bone collar, but was at markedly lower levels in the newly formed cartilage. Sox9 mRNA was continuously expressed from the embryonic zone to the newly formed cartilage. At this stage, Sox5 mRNA was expressed only in the newly formed cartilage. These results suggest that reduced expression of Osterix in combination with Sox9-Sox5 expression is important for the onset of condylar (secondary) cartilage formation.

We investigated the expression pattern of versican, aggrecan, link protein and hyaluronan in the developing limb bud cartilage of the fetal mouse using in situ hybridization and/or immunohistochemistry. Versican mRNA and immunostaining were detected in the mesenchymal cell condensation of the future digital bone at E13. Versican mRNA expression rapidly disappeared from the tibial cartilage, as cartilage formation progressed during E13-15, but the immunostaining was gradually replaced by aggrecan immunostaining from the diaphysis. Immunostaining for both molecules thus had a 'nega-posi' pattern and consequently versican immunostaining was still detected at the epiphyseal end at E15. This result indicated that versican functions as a temporary framework in newly formed cartilage matrix. An aggrecan-positive region within the cartilage invariably had intense hyaluronan staining, whereas a versican-positive region also had affinity for hyaluronan within the cartilage, but not in the mesenchymal cell condensation. Therefore, the presence of versican aggregates was not confirmed in the developing limb bud cartilage. Furthermore, although link protein was more closely related with aggrecan than versican during limb bud cartilage formation, there was a discrepancy between the expression of aggrecan and link protein in tibial cartilage at E15. In particular, only a link protein-positive region was present in the marginal area of the metaphysis and the epiphysis at this stage. This finding may indicate a novel role for link protein.