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Volume 80, Issue 1
Displaying 1-4 of 4 articles from this issue
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Review
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Hiroo KAGAMI, Yoshinobu KAWANO, Toshiyuki IKAWA, Naoko NISHI, Tsuyoshi ...2004 Volume 80 Issue 1 Pages 1-9
Published: 2004
Released on J-STAGE: June 30, 2004
JOURNAL FREE ACCESSThe Nd-isotopic data on sedimentary and metamorphic rocks of SW Japan Arc allow their discrimination into five different depleted mantle (TDM) model age clusters, 2.6-2.45 Ga, 2.3-2.05 Ga, 1.9-1.55 Ga, 1.45-1.25 Ga, 1.2-0.85 Ga. The 2.6-2.45 Ga and 1.9-1.55 Ga model ages are also coincident with U-Pb inherited zircon ages of the above two epochs as well as the major magmatic activity in the Sino-Korean Craton (SKC). The 2.3-2.05 Ga model ages can be considered as the initial formation ages for the precursors of sedimentary rocks. The Nd-isotopic data suggest that the Hida Belt was most likely formed as a part of the SKC. The mantle underlying the Ryoke Belt had continental lithospheric signature during Triassic-Jurassic period. The 1.9-1.55 Ga model ages, especially 1.8 Ga~, can be associated with the formation of this belt. The source material for the sedimentary rocks occurring in the accretionary terrane of northeastern areas in the SW Japan Arc was probably in and around the SKC of the Ryoke Belt itself. The sedimentary rocks occurring in southwestern areas of the Arc were mainly composed of materials derived from a relatively younger source (1.45-0.85 Ga).
(Communicated by Syun-iti AKIMOTO, M.J.A., Jan. 13, 2004)
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Original Papers
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Record of Late Permian double mass extinction eventYukio ISOZAKI, Jianxin YAO, Tetsuo MATSUDA, Harutaka SAKAI, Zhansheng ...2004 Volume 80 Issue 1 Pages 10-16
Published: 2004
Released on J-STAGE: June 30, 2004
JOURNAL FREE ACCESSPrecise stratigraphic analysis of Middle-Upper Permian and Lower Triassic sequence at Chaotian in northern Sichuan, China, identified two remarkable mass extinction horizons, one at the Middle-Upper Permian (Guadalupian-Lopingian; G-L) boundary and the other at the Upper Permian-Lower Triassic (P-T) boundary. Across each of the boundaries, biodiversity declined sharply in fusulinid, rugose coral, brachiopod, ammonite, conodont, and radiolaria. Both boundaries are characterized by two biohorizons, i.e., one marked by major extinction of pre-existing fauna and the other by the first appearance of younger fauna. It is noteworthy that a peculiar rhyo-dacitic tuff bed occurs at each of the extinction horizons. Thus the Late Permian biosphere was strongly affected twice by highly explosive, severe volcanism. Regional correlation of the G-L and P-T boundary tuff beds throughout South China, and partly to Japan, positively suggests a cause-effect link between large-scale explosive volcanism and mass extinction.
(Communicated by Tatsuro MATSUMOTO, M.J.A., Jan. 13, 2004)
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Satoshi OHTA, Nobuyuki HAGA2004 Volume 80 Issue 1 Pages 17-21
Published: 2004
Released on J-STAGE: June 30, 2004
JOURNAL FREE ACCESSNon-deteriorative cellular functions were examined in Paramecium and found in the cell lines undergoing proliferative senescence. Changes in two kinds of cellular functions, the ability to regenerate cilia and the locomotive function of cilia, were compared between young and old cells. The ability to regenerate cilia after artificial deciliation decreased in old Paramecium cells, but the ability of cilia to swim both forward and backward was stable with age. Our results suggest that morphogenesis of cilia is a deteriorative character, but the locomotive function of cilia is not associated with proliferative senescence.
(Communicated by Koichi HIWATASHI, M.J.A., Jan. 13, 2004)
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2. Crystal formation by a full length FFRP, pot0434017 (FL11)Sanae A. ISHIJIMA, Lester CLOWNEY, Hideaki KOIKE, Masashi SUZUKI2004 Volume 80 Issue 1 Pages 22-27
Published: 2004
Released on J-STAGE: June 30, 2004
JOURNAL FREE ACCESSIn the crystal the archaeal feast/famine regulatory protein pot0434017 (FL11) forms helical cylinders, each extending along the c axis and densely packed with a hexagonal symmetry in the a/b plane. By applying cryo-electron microscopy to protein solutions yielding crystals, with selectively focussing zero-loss electrons accelerated at 200 KV, two types of regular objects were observed, hexagonal (i.e. projections of crystals to their a/b planes) or rectangular (i.e. projections onto planes perpendicular to a/b). The two types of images are different in the ranges of sizes, suggesting that the crystallization might initiate by forming a hexagonal sheet on the a/b plane, subsequently extending along the c axis. Some other images obtained were intermediate between regular and amorphous, suggesting that some crystals were growing inside amorphous precipitates by rearranging the protein molecules, and that some larger crystals were growing by absorbing smaller amorphous precipitates. Tubes running parallel to each other were also observed in pieces of thin films. These tubes have hollows in their centers, and their lateral arrangement with a periodicity of ~150 Å and the presence of a helical component ~50 Å suggest that they are projections of the helical cylinders, forming mono-layers on the a/c or b/c planes.
(Communicated by Masanori OTSUKA, M.J.A., Dec. 13, 2004)
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