Sakae Nagasawa

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.

Study on the frictional properties between bracket and wire by sandblast processing

Abstract Purpose Various techniques are employed during orthodontic treatment involving anchorage units and multi-bracket apparatus. We investigated the efficacy of such techniques by examining the frictional force they created between the wire and bracket using a pulling test. Materials and methods In order to examine how the frictional force between the wire and bracket varied between operators and ligature types, 0.010 in. stainless steel orthodontic ligature wires (ligature wires) and orthodontic elastic modules (ligature modules) were used five times each by 11 orthodontists, and the resultant frictional force created between the wire and bracket was measured with a pulling test. To compare the effects of sandblast processing on the frictional force between the bracket and wire, each of the following four types of orthodontic wires was used five times: 0.016 in. round stainless steel wire, 0.016 in. round nickel titanium wire, 0.017 × 0.025 in. rectangular stainless steel wire, and 0.017 × 0.025 in. rectangular nickel titanium wire. Results The ligature modules exhibited significantly lower frictional force than the ligature wires. The frictional force in ligature modules also was more stable than in the ligature wire among the assessments of inter-operator and intra-operator. All of the wire types demonstrated significantly greater frictional force after being sandblasted. Conclusion These results indicate that the applying of wire with sandblast processing and ligature modules can reinforce the anchorage units used for tooth movement by increasing the stable frictional force between the bracket and wire.

Identification of cell cycle–arrested quiescent osteoclast precursors in vivo

1. 1. Mizoguchi, 2. et al. J. Cell Biol. 2009 doi:[10.1083/jcb.200806139][1] [1]: /lookup/doi/10.1083/jcb.200806139