Proceedings of the Japan Academy, Series B
Online ISSN : 1349-2896
Print ISSN : 0386-2208
ISSN-L : 0386-2208
Volume 77 , Issue 9
Showing 1-4 articles out of 4 articles from the selected issue
  • Hiroko NAGAHARA, Kazuhito OZAWA
    2001 Volume 77 Issue 9 Pages 167-171
    Published: 2001
    Released: October 17, 2006
    JOURNALS FREE ACCESS
    The Hf-W chromometer that was developed recently is a very powerful tool because of high time resolution due to short half life and significant partitioning of Hf into the mantle and W into the core. We have developed a mass conservation equation, which includes three important parameters, mass accretion rate, metal separation rate, and redox reaction rate, and searched for the conditions to satisfy the Hf/W and W isotopic compositions of the present Earth's mantle. Although previous work has suggested slow accretion (accretion time >50Myr), it could be shorter by an order of magnitude if the metal separation time or redox reaction rate is longer than -100Myr. The slow metal separation rate with rapid accretion is, however, inconsistent with constraints from thermal evolution and fluid dynamics, and slow redox reaction of oxidized materials is the plausible mechanism.
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  • Yuka NAKAJIMA, Kazuyuki MIKAMI, Mihoko TAKAHASHI
    2001 Volume 77 Issue 9 Pages 172-177
    Published: 2001
    Released: October 17, 2006
    JOURNALS FREE ACCESS
    Fertilization process of Paramecium caudatum includes a reciprocal exchange of migratory pronuclei across a temporary junction between conjugating cells. To know the role of microtubules on the behavior of pronuclei during conjugation in P. caudatum, the localization of microtubules was investigated by indirect immunofluorescence with a monoclonal anti-α-tubulin antibody. The immunofluorescence showed that the migratory pronucleus was surrounded by the cytoplasmic microtubules. The migratory pronucleus seems to be pushed to the cell junction by the cytoplasmic microtubules. Then the migratory pronucleus extended into the partner cell. An electron-microscopic observation showed that the cytoplasmic microtubules were assembled at the back of the migratory pronucleus, and the intranuclear microtubules of the pronucleus were aligned along the direction of the extension at the exact moment when the migratory pronucleus was crossing the cell junction. The transfer of migratory pronucleus was inhibited by injection of the monoclonal anti-α-tubulin antibody. These evidences suggest that both the cytoplasmic and the intranuclear microtubules are necessary for the dynamic behavior of gametic pronucleus across the cell junction of conjugating pair. We also suggest that microtubules are involved in the pronuclear migration after entering the partner cell.
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  • Poh-Sing NG, Hui LI, Kazuko MATSUMOTO, Sunao YAMAZAKI, Toshihiro KOGUR ...
    2001 Volume 77 Issue 9 Pages 178-183
    Published: 2001
    Released: October 17, 2006
    JOURNALS FREE ACCESS
    Sea mammals are known to contain high concentrations of mercury and selenium especially in the liver with no apparent symptoms of poisoning. We examined the chemical form of mercury and selenium in the liver of striped dolphin, Stenella coeruleoalba. Neither mercury nor selenium could be extracted with acetone, 80% ethanol or 0.2M ammonium acetate. The residue after extraction was digested most effectively with alkaline protease, resulting in solubilization of almost all the material (99% by weight) but still leaving a small amount of insoluble material (1%), which contained 80% of mercury and 66% of selenium of the original amount. This insoluble material was subjected to transmission electron microscopic analysis, X-ray microanalysis, X-ray diffraction analysis and elemental analysis, which revealed that the material contained spherical crystals of Hg(S0.34, Se0.66) with 5-10nm in diameter as a major component. These crystals may be the final detoxification product of mercury.
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  • Kotaro KOYAMA, Masahiko WATANABE, Toshitami KOMATSU, Takashi SUGIMURA, ...
    2001 Volume 77 Issue 9 Pages 184-186
    Published: 2001
    Released: October 17, 2006
    JOURNALS FREE ACCESS
    Cytotoxic activity of aqueous extracts from adult moth abdomens of 12 species belonging to the subfamily Arctiinae was tested in vitro using human gastric carcinoma TMK-1 cells. The strong cytotoxic activity, down to a dilution of 1/105, was found in females of all of 12 species of moths. However, samples of the males of the same species were without cytotoxicity. Females of three species, not of this subfamily, and those of 9 species, belonging to other family than Arctiinae, did not show any cytotoxicity. The strong cytotoxic activity in female abdomens of Hyphantria cunea was located in the ovaries. The active principle in the extract sample from H. cunea was inactivated by heat, acid or alkaline treatment and digested by proteases, indicating probably protein in its nature. Thus, cytotoxic factors in moths of the subfamily Arctiinae were likely to be derived from their ovaries.
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