Nobutake Kanematsu

BONE FORMATION UNDER THE INFLUENCE OF BONE MORPHOGENETIC PROTEIN/SELF -SETTING APATITE CEMENT COMPOSITE AS A DELIVERY SYSTEM

Self-setting apatite cement (apatite cement) with a phase of hydroxyapatite (HAP) was employed as a delivery system for bone morphogenetic protein (BMP). A composite of BMP and apatite cement (BMP/HAP composite) was implanted both in thigh muscle and surgically created defect of a critical size of 5 mm, which is a size that does not heal spontaneously in the femur of mice, to evaluate its osteogenetic potential as an augmentation and reconstructive material for clinical usage. The histological and immunohistochemical assessment of proteoglycans reiterated osteogenesis in the muscle tissue. On day 14 postimplantation of BMP/HAP composite, chondroid tissue was formed in the muscle, and HAP particles were seen in newly formed chondroid tissue. On the 21st day, endo-chondral ossification had occurred, however, small HAP particles remained in the newly formed bone, i.e., HAP particles and newly formed osseous tissues coexisted in a central area. BMP/HAP composite was incorporated by newly formed osseous tissue in the experimented animals. HAP particle found in BMP/HAP composite implanted into the bone defect was resorbed and replaced by osseous tissue. The apatite cement was proved to have advantages for its shaping as well as collapsing properties, and thus, apatite cement containing BMP is suggested as a favorable augmentation material in clinical usage for delivery system of BMP.

Dentinogenic ghost cell tumor: histologic aspects, immunohistochemistry, lectin binding profiles, and biophysical studies.

Dentinogenic ghost cell tumor accompanied with calcifying odontogenic cyst (COC) was described in terms of its clinical, histological, immunohistochemical, lectin binding and biophysical properties. The case was a 38-year-old Japanese female, in whom the tumor had arisen in the right mandibular premolar and molar region. Material obtained by partial mandibulectomy was used. Decalcified paraffin sections were used to detect keratins, involucrin, and lectin binding; and non-decalcified thin sections were used for biophysical analysis. The lesion comprising dentinogenic ghost cell tumor and COC contained odontogenic epithelium with ghost cells, eosinophilic amorphous materials and osteodentin. Some of the eosinophilic material had undergone transformation into osteodentin. Keratins in odontogenic epithelia showed positive PKK1 staining in peripheral tumor cells, and stainings with KL1 and involucrin were positive in centrally located cells. Lectin binding in the amorphous materials was comparatively strong for PNA, and SBA, moderate for WGA, RCA-1, and UEA-1, and slight for DBA and ConA. Lectin binding affinities were higher in the amorphous materials than in the osteodentin. Elemental analysis with an electron probe X-ray microanalysis of the amorphous materials and osteodentin showed a pattern similar to that found in the normal dentin. The biologic properties of the eosinophilic amorphous materials suggested the material to be poorly calcified osteodentin, which gradually transformed into the well-calcified type.

Temperature-dependent changes in phospholipid and fatty acid composition and membrane lipid fluidity of Yersinia enterocolitica

Temperature‐dependent compositional changes of phospholipids and their fatty acids were analysed in Yersinia enterocolitica grown at 5°, 25° and 37°C. The relative amounts of the four phospholipids, phosphatidylethanolamine (75–78%), phosphatidylglycerol (10–11%), cardiolipin (<7%) and lysophosphatidylethanolamine (<5%), were essentially the same at all growth temperatures. The degree of fatty acid unsaturation of the four phospholipids increased with decrease in growth temperature, mainly due to an increase of C16:1 and C18:1 and a corresponding decrease of C16;0, C18:0 and cyclo C17:0. An electron spin resonance spectroscopic study of the membrane lipids showed that membrane lipid fluidity was enhanced by decreasing the growth temperatures. The changes in fatty acid composition of phospholipids in response to varied temperatures were consistent with the temperature‐dependent changes in the membrane lipid fluidity of Y. enterocolitica, and were similar to those reported for other bacteria.

Bone tissue engineering using porous carbonate apatite and bone marrow cells.

Porous blocks of carbonate apatite (CA) were prepared by holding together CA particles ranging in size from 300 to 500 &mgr;m through sintering at 750°C for 2 hours. Bone marrow cells taken from Fischer rats were seeded onto and inside the CA blocks and cultured for 14 days to allow stem cells to proliferate to osteoblasts capable of inducing bone formation. Hybrids made of CA blocks and cultured bone marrow cells were then implanted into the back of syngeneic rats. Microfocus x-ray computed tomographic images of tissues containing CA blocks before decalcification suggested that new bone was formed in this extraosseous site 4 and 8 weeks after implantation. These data indicate that the hybrid made of CA and bone marrow cells is capable of inducing heterotopic bone formation in vivo.

Bone scintigraphy in solitary (Simple) bone cyst of jaw

Six cases of solitary (simple) bone cyst with typical clinical, radiographical, and histological findings were examined by bone scintigraphy. Bone scintigraphy using99mTc-HMDP was performed prior to operation. No uptake of99mTc-HMDP in these solitary bone cysts was demonstrated. On the other hand, 2 cases of florid osseous dysplasia (Melrose et al. 1976) associated with bone cavities resembling solitary bone cyst showed remarkable uptake of99mTc-HMDP.Six cases of solitary (simple) bone cyst with typical clinical, radiographical, and histological findings were examined by bone scintigraphy. Bone scintigraphy using99mTc-HMDP was performed prior to operation. No uptake of99mTc-HMDP in these solitary bone cysts was demonstrated.On the other hand, 2 cases of florid osseous dysplasia (Melrose et al. 1976) associated with bone cavities resembling solitary bone cyst showed remarkable uptake of99mTc-HMDP.

Sucrose concentratidns in the growth medium influence the membrane lipids of Streptococcus mutans

Streptococcus mutans was cultivated in media containing sucrose (10–40%, w/v) and the sucrose induced changes in chemical and physical properties of its membrane lipids were investigated. The degree of unsaturation in the fatty acids of both total lipid and glycolipid fractions decreased when the sucrose concentration was increased. An electron spin resonance spectroscopic study revealed the reduction of membrane lipid fluidity by adding sucrose to the growth medium. Liposomes prepared from membrane lipids of bacteria grown with sucrose showed less osmotic volume changes than those of bacteria grown without sucrose. These results suggest that modification of membrane lipid composition, fluidity and osmosis‐resistance have an important role in the ability of Streptococcus mutans to grow in sucrose at high concentrations.