• The korean journal of orthodontics
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• v.26 no.3
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• pp.291-299
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• 1996

Orthodontic force is a mechanical stress controlling both of tooth movement and skeletal growth. The mechanical stress stimulate bone cells that may exert some influence on bone remodeling. The purpose of this study was to evaluate the difference in cellular activity depending on mechanical stresses such as compressive and tensile force by determining the alkaline phosphatase(ALP) activity. A clonal osteogenic cell line MC3T3-E1 was seeded into a 24-well plate($2{\times}10^4/well$). At the confluent phase, a continuous compressive hydrostatic pressure($25g/cm^2$, $300g/cm^2$) and continuous tensile hydrostatic pressure($-25g/cm^2$, $-300g/cm^2$) were applied for 4, 6, 10, 14, 18, 20 days respectively by a diaphgragm pump. At the end of the stimulation period, cell layers were prepared for ALP activity assay. The ALP activity of the compressive group increased more than that of the tensile group at same force magnitude, whereas the cells responded to a similar pattern regardless of the type of mechanical stress The ALP activity of the compressive and tensile group turned into the level of the control group as the length of time increased. These results indicated that a mechanical stress may be more effective on cellular activity during active cellular proliferation and differentiation periods. The time to achieve maximum ALP activity was delayed as the mechanical stress increased in both the compressive and the tensile group. Accordingly, the magnitude of the stress rather than the type of mechanical stress may have more influence on cellular activity.

• Korean Journal of Medicinal Crop Science
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• v.1 no.2
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• pp.137-157
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• 1993

This study was carried out to investigate the optimal condition for multiple propagation through leaf tissue culture and to apply anther culture techniques to Pulsatilla koreana Nakai breeding. Leaf and anther of Pulsatilla koreana Nakai were cultured on MS, MT, LS and $B_5$ media supplemented with several growth regulators and nitrogen sources under various conditions. For callus induction and differentiation from the Pulsatilla koreana leaf segments were more effective in the combination of zeatin and auxin than auxin alone. The color of the callus was green when treated with IBA alone. Shoot differentiation was more effective when treated with zeatin than auxin alone, especially the best hormoal combination for shoot differentiation was zeatin 1.0mg/l +NAA 0.1mg/l, while 2,4-D inhibited shoot differentiation. The appeared rate of S pollen was 35% in vivo, while that of S pollen by low temperature$(4^{\circ}C)$ pretreatment for 4 days was increased by 53% and the optimum culture time for callus induction from anther was uni-nucleate stage. $B_5$ basal medium supplemented with NAA 0.5mg/l and zeatin 1 mg/l was the most effective on callus formation and the best results of plant regeneration were obtained from combination of NAA 0.5mg/l and zeatin 0.5mg/l in anther culture. $NH_{4}NO_3$ as more effectives as the nitrogen source than $KNO_3$ and the combination with zeatin 2.0mg /L was the best effective. The best combination for plant regeneration in callus induced from anther was $NH_{4}NO_3$ 1650mg/l + $KNO_3$ 3800mg/l + zeatin 2.0mg/l. Ploidy level of anther-derived plants appeared 28% haploid, 47% diploid and the others were triploid, tetraploid and mixploid. In compare with E.S.T, M.D.H and P.X banding patterns were distinguished among callus, haploid and diploid plants in electrophoresis.