Hiroshi Yagasaki

Effect of hydroxyapatite content on physical properties and connective tissue reactions to a chitosan-hydroxyapatite composite membrane.

The present study investigated the effect on certain physical properties of adding various amounts of hydroxyapatite (HAP) to chitosan sol. Also investigated were connective tissue reactions to a composite membrane that is being developed for possible use in guided tissue regeneration and for the limitation of HA particle migration at sites of implantation. The physical properties evaluated were shrinkage, tensile strength, hardness, calcium ion release, and morphology. Assessment of physical properties indicated that a ratio of HA to chitosan sol of 4/11 by weight is optimal in the preparation of the composite membrane. Subperiosteal implantation of the membranes over rat calvaria revealed that the membranes were well tolerated, with fibrous encapsulation and occasional areas of osteogenesis. Increasing the hydroxyapatite content seems to enhance membrane degradation.

Histopathological and immunohistochemical studies of membranes of deacetylated chitin derivatives implanted over rat calvaria

Membranes made of 65, 70, 80, 94, and 100% deacetylated chitin (chitosan) were implanted subperiosteally over the calvaria of 100 rats. Reactions were studied at 1, 2, 4, and 8 weeks after implantation. Membranes prepared with 65, 70, and 80% deacetylated chitin initially elicited marked inflammatory reactions that subsided in time with granulation tissue formation and osteogenesis. Osteocalcin-positive cells were detected immunohistochemically in the granulation tissue. On the other hand, membranes made of 94% deacetylated chitin and chitosan showed mild inflammation and minimal osteogenesis. The results indicate that membranes made of 65, 70, and 80% deacetylated chitin enhance osteogenesis at the site of their implantation. However, the initially severe inflammatory reaction associated with these materials needs to be controlled before the materials would be suitable for clinical application.

In vitro properties of a chitosan-bonded bone-filling paste : Studies on solubility of calcium phosphate compounds

The present study investigated properties of various mixtures of organic acids (malic and malonic) and calcium phosphate compounds (beta-tricalcium phosphate, ashed bovine bone, and synthetic hydroxyapatite) with the objective of determining the optimum combination of organic acid and calcium phosphate compound for components of a chitosan-bonded bone-filling paste. beta-tricalcium phosphate was decomposed by malic acid and malonic acid, but these two acids did not decompose synthetic hydroxyapatite and ashed bovine bone. Assessment of ion release from a set paste containing either synthetic hydroxyapatite or ashed bovine bone indicated that only calcium ions were appreciably released after storing and stirring the set paste in physiologic saline for 7 days.

Dolomite supplementation improves bone metabolism through modulation of calcium-regulating hormone secretion in ovariectomized rats

Dolomite, a mineral composed of calcium magnesium carbonate (CaMg (CO3)2), is used as a food supplement that supplies calcium and magnesium. However, the effect of magnesium supplementation on bone metabolism in patients with osteoporosis is a matter of controversy. We examined the effects of daily supplementation with dolomite on calcium metabolism in ovariectomized (OVX) rats. Dolomite was administered daily to OVX rats for 9 weeks. The same amount of magnesium chloride as that supplied by the dolomite was given to OVX rats as a positive control. Histological examination revealed that ovariectomy decreased trabecular bone and increased adipose tissues in the femoral metaphysis. Dolomite or magnesium supplementation failed to improve these bone histological features. Calcium content in the femora was decreased in OVX rats. Neither calcium nor magnesium content in the femora in OVX rats was significantly increased by dolomite or magnesium administration. Urinary deoxypyridinoline excretion was significantly increased in OVX rats, and was not affected by the magnesium supplementation. Serum concentrations of magnesium were increased, and those of calcium were decreased, in OVX rats supplemented with dolomite or magnesium. However, there was a tendency toward decreased parathyroid hormone secretion and increased calcitonin secretion in OVX rats supplemented with dolomite or magnesium. Serum 1,25-dihydroxyvitamin D3 and osteocalcin levels were significantly increased in the supplemented OVX rats. These results suggest that increased magnesium intake improves calcium metabolism in favor of increasing bone formation, through the modulation of calcium-regulating hormone secretion.

Experimental Development of a Chitosan-Bonded β-Tricalcium Phosphate Bone Filling Paste

Bone filling substances are needed to meet several requirements including nontoxicity, setting time, changes in pH values, and amount of dissolved elements as well as mechanical properties. In this study, the bone-generating composites were prepared by employing the in vivo absorbable beta-tricalcium phosphate as a parent matrix kneaded with CaO, MgO, and ZnO as bone mineral additives with different compositions. The setting time, pH values, compressive strength were investigated as a function of the amount of these bone mineral additives. It was found that the setting time was shortened by increasing CaO, MgO, and ZnO contents. Increasing ZnO contents resulted in the pH value lower, while the pH values increased by increasing CaO and MgO contents. Increasing ZnO contents caused the compressive strength stronger, on the other hand, the compressive strength was weakened by increasing MgO contents. Furthermore, calcium appears to be selectively released from the hardened composite sample.

Distribution and origin of VIP‐, SP‐, and phospholipase Cβ2‐ immunoreactive nerves in the tongue of the bullfrog, Rana catesbeiana

Previous studies have found a few intralingual ganglionic cells that were immunoreactive to vasoactive intestinal polypeptide (VIP) in the frog. A recent study reported a large number of such cells, and the possibility of the release of substance P (SP) from these. The aim of the present study was to investigate the distribution, origin, and colocalization of VIP‐ and SP‐ immunoreactive nerves in the tongue of the bullfrog, R. catesbeiana. In addition, the study also examined the colocalization of SP and phospholipase Cβ2 (PLCβ2) in the tongue and jugular ganglion. VIP immunoreactivity was seen in unipolar cells that were sparse in nerve bundles in the submucosal and muscle layers. The density of VIP‐immunoreactive cells was approximately 4.8 cells/mm3. Their fibers terminated in the vicinity of the epithelial basal layer of the fungiform papillae. SP immunoreactivity was not seen in the VIP‐immunoreactive cells, but was observed in pseudounipolar cells in the jugular ganglion. The SP fibers terminated close to the free surface, showing spindle‐ and button‐like profiles. Transection of glossopharyngeal nerve resulted in the persistence of VIP‐immunoreactive cells and the disappearance of SP‐immunoreactive fibers in the tongue. SP immunoreactivity was co‐expressed with PLCβ2 in both the tongue and jugular ganglia. No PLCβ2 immunoreactivity was seen in cells comprising the epithelial taste disk. These findings indicate that the origin of VIP nerve fibers are unipolar cells in the tongue, and SP and PLCβ2 fibers originate from pseudounipolar cells that may be able to release SP primarily in the jugular ganglion. Anat Rec, 299:929–942, 2016.