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Bone-resorbing activities of 24-epi-1α-hydroxyvitamin D2 and 24-epi-1α,25-dihydroxyvitamin D2 (1995)

Yokoyama, K. ; Miyahara, T. ; Matsumoto, M. ; [et al.]

Springer

Calcified tissue international 56 (1995), S. 49-53

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ISSN: 1432-0827

Keywords: Bone resorption ; Osteoclast formation ; Resorption lacunae ; 24-epi-1α-hydroxyvitamin D2 ; 24-epi-1α,25-dihydroxyvitamin D2

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Medicine , Physics

Notes: Abstract Bone-resorbing activities of 24-epi-1α-hydroxyvitamin D2 [24-epi-1α(OH)D2], 24-epi-1α,25-dihydroxyvitamin D2 [24-epi-1,25(OH)2D2], and 1α,24S,25-trihydroxyvitamin D2 [1,24S,25(OH)3D2], which might be a metabolite of 24-epi-1,25(OH)2D2, were investigated. In an in vitro bone resorption test, the activity of 24-epi-1α(OH)D2 was similar to that of 1α-hydroxyvitamin D3 [1α(OH)D3] at 10-9 M-10-6 M. The activity of 24-epi-1,25(OH)2D2 was weaker than that of 1α,25-dihydroxyvitamin D3 [1,25(OH)2D3] at 10-11 M-10-8 M. On the other hand, the activity of 1,24S,25(OH)3D2 was similar to that of 24-epi-1,25(OH)2D2 at 10-11 M-10-9 M. In the formation assay of osteoclast-like cells, the activity of 24-epi-1α(OH)D2 was weaker than that of 1α(OH)D3 at 10-7 M. The activity of 24-epi-1,25(OH)2D2 was almost similar to that of 1,25(OH)2D3 at 10-11 M-10-7 M. The activity of 1,24S,25(OH)3D2 was significantly weaker than that of 24-epi-1,25(OH)2D2 at 10-11 M-10-9 M. In the two experiments, the potencies of 24-epi-1,25(OH)2D2 were about 100 times higher than those of 24-epi-1α(OH)D2. In an in vivo/in vitro bone resorption test, the activity of 24-epi-1α(OH)D2 was almost similar to those of 1α(OH)D3 and 1,25(OH)2D3 and higher than those of 24-epi-1,25(OH)2D2 and 1,24S,25(OH)3D2. 24-epi-1α-(OH)D2 and 1α(OH)D3 were longer lasting than 24-epi-1,25(OH)2D2 and 1,25(OH)2D3 in this experiment. These results suggested that 24-epi-1α(OH)D2 as well as 1α(OH)D3 was converted into dihydroxy form in vivo.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00298744

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Study of the pseudo-steady-state kinetics of CO2 hydrate formation and stability (1994)

Lund, P. C. ; Shindo, Y. ; Fujioka, Y. ; [et al.]

New York, NY : Wiley-Blackwell

International Journal of Chemical Kinetics 26 (1994), S. 289-297

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ISSN: 0538-8066

Keywords: Chemistry ; Physical Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: This article describes a dynamic model for formation and stability of CO2-hydrate on the interface of liquid CO2(LCO2) and ocean water at large depths. Experimental results indicate that a thin film of hydrate naturally forms on the interfaces between LCO2 and water, and inhibits diffusion between the two phases. Experiments further shows that the flux of CO2 through the hydrate film is dependent of the CO2-concentration in the ambient sea water. The model proposed here explains these phenomena by introducing four major mechanisms; diffusion of water to the LCO2-phase, formation of hydrate in the LCO2-hydrate interface, decay of hydrate in the water-hydrate interface, and diffusion of CO2 through the water phase. The model explains the CO2 flux not by diffusion through the hydrate film, but suggest a mechanism of continuous hydrate formation and decay. The overall effect is a “moving,” pseudo-steady-state hydrate film due to transport of CO2 through the film. The film velocity is dependent of liquid-liquid diffusivity parameters and reaction constant, and lacking experimental values of these parameters, an order-of-magnitude analysis is done by fitting the model to experimentally obtained data for the overall film velocity. The motivation for this work is to elucidate options for CO2 depositions in deep oceans, of which liquid CO2 sequestration is believed to be one of the most feasible. Spreading of CO2 from a liquid CO2-lake and associated lowering of pH in the ecosystem surrounding the lake is of large concern. The work presented here concludes that diffusion of CO2 in the ocean is largely reduced by the hydrate film and suggests that hydrate formation may alleviate some of the environmental concerns regarding deep ocean sequestration of liquid CO2. © 1994 John Wiley & Sons, Inc.

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