Cell Structure and Function
Online ISSN : 1347-3700
Print ISSN : 0386-7196
ISSN-L : 0386-7196
Volume 17, Issue 4
Displaying 1-6 of 6 articles from this issue
  • Atsushi Ito, Kunio Shinohara
    1992 Volume 17 Issue 4 Pages 209-212
    Published: 1992
    Released on J-STAGE: March 27, 2006
    JOURNAL FREE ACCESS
    A simple model is presented for the estimation of image blurring in X-ray microscopy of biological specimens in a hydrated environment. The model is essentially based on thermal diffusion of an object to be imaged. The degree of image blurring by diffusion depends on the following situations of the object. The object is free from, is tightly fixed to, or is partially connected to the surrounding structures. The proper imaging time required to achieve a given resolution in X-ray microscopy of biological structures was estimated with the present method. The results suggest that imaging time shorter than 3 msec (free) to 1.4 sec (tightly fixed) is required for the observation of a cell (30μm in diameter) at the resolution of 100 nm. The model is also applicable to a fragmented object caused by imaging X-rays.
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  • Teruo Yamauchi, Masahito Higashiura, Tatsuo Yagura
    1992 Volume 17 Issue 4 Pages 213-222
    Published: 1992
    Released on J-STAGE: March 27, 2006
    JOURNAL FREE ACCESS
    Partially purified Golgi membranes of HeLa cells were used as antigen to produce a novel monoclonal antibody (mAb G3A5). The mAb G3A5 specifically labeled Golgi apparatus of human and monkey cultured cells as ascertained by indirect immunofluorescence but did not stain those of bovine or mouse cells. Treatment with nocodazole and brefeldin A (BFA) induced fragmentation and redistribution of the staining. Western immunoblot analysis showed that mAb G3A5 was directed against a single polypeptide with an apparent molecular mass of 138-kDa (p138 antigen). The p138 antigen is an integral membrane protein of the Golgi apparatus, as assessed by several assays: protease protection, salt wash and flotation in sucrose density gradient centrifugation. The p138 antigen was purified using immunoaffinity chromatography. The apparent molecular mass of the p138 antigen decreased by 2 to 4 kDa after treatment with the peptide: N-glycosidase F, while digestion with ENDO F or Neuraminidase did not have this effect. Thus, p138 antigen is a glycoprotein containing asparagine linked carbohydrates.
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  • Yosuke Tojyo, Akihiko Tanimura, Satoko Matsui, Yoshito Matsumoto
    1992 Volume 17 Issue 4 Pages 223-227
    Published: 1992
    Released on J-STAGE: March 27, 2006
    JOURNAL FREE ACCESS
    At concentrations >0.01 μM, thapsigargin (ThG) dose-dependently caused an increase in cytosolic free Ca2+ concentration ([Ca2+]i) in rat parotid acinar cells, as measured by the fluorescent Ca2+-indicator fura-2. In the absence of extracellular Ca2+, a transient increase in [Ca2+]i by ThG was observed, and subsequent addition of carbachol (CCh) did not produce a further [Ca2+]i response, suggesting that ThG released Ca2+ from the CCh-sensitive intracellular Ca2+ pool. Since ThG did not stimulate formation of inositol phosphates, the ThG-induced Ca2+ mobilization is independent of phosphoinositide breakdown. High concentrations (>0.1 μM) of ThG induced amylase release from rat parotide acini, but the effect was very poor as compared with that of CCh or the protein kinase C activator, PMA(phorbol 12-myristate 13-acetate). Combined addition of ThG and PMA modestly potentiated amylase release induced by PMA alone. These results support the view that amylase release by muscarinic stimulation is mediated mainly by activation of protein kinase C rather than a rise in [Ca2+]i although Ca2+ may modulate the secretory response.
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  • Kousaku Ohno, Eiji Nanba, Shigeki Miyawaki, Takeshi Sakiyama, Teruo Ki ...
    1992 Volume 17 Issue 4 Pages 229-236
    Published: 1992
    Released on J-STAGE: March 27, 2006
    JOURNAL FREE ACCESS
    Cell lines derived from the sphingomyelinosis (gene symbol, spm) mouse were established from homozygous (spm/spm) and heterozygous (spm/+) embryos according to a rigid 3T3 transfer schedule. The SPM-3T3 cells derived from a homozygousembryo showed extensive accumulation of intracellular cholesterol, attenuated esterification of exogenously added cholesterol and increased de novo cholesterol synthesis, when compared to SPMH-3T3cells derived from a heterozygous embryo. The phenotypic abnormalities were very similar to those observed in fibrobJasts from patients with Niemann-Pick disease type C (NP-C), in which a defect in the intracellular transport of unesterified cholesterol is suggested. The genetic defect in SPM-3T3 cells should be closely related to that in NP-C. The SPM-3T3cell line is useful for biochemical and genetic studies on the regulation of intracellular cholesterol metabolism.
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  • Jeman Kim, Toshiyuki Adachi, Etsuko Hirayama, Tadaaki Yabubayashi, Yos ...
    1992 Volume 17 Issue 4 Pages 237-247
    Published: 1992
    Released on J-STAGE: March 27, 2006
    JOURNAL FREE ACCESS
    Quail embryonic pectoral myoblasts fuse with each other at 35.5°C and 41°C to essentially equal extents. When the myoblasts were transformed with a temperature-sensitive mutant of Rous sarcoma virus (ts-RSV), their fusion and biochemical processes of differentiation became temperature-sensitive: their fusion occurred at 41°C, the non-permissive temperature, but not at 35.5°C, the permissive temperature, suggesting that the fusion was regulated by the viral transforming gene.
    Fusion of the transformed cells proceeded more rapidly and synchronously than that of the parent cells at 41°C, and was completely suppressed at the permissive temperature, unlike that of the parent cells. These transformed cells were used to examine the relationship between myogenic differentiation and the tyrosine kinase activity of the src gene product. In spite of the temperature sensitivity of transformation, results showed that expressions of the src gene at 35.5°C and 41°C were similar. However, the level of tyrosine-phosphorylated protein was decreased at 41°C. Moreover, myoblast fusion could occur at 35.5°C in the presence of herbimycin A, an inhibitor of the tyrosine kinase activity of the src gene product. These results indicate that the tyrosine kinase activity of the src gene product is closely associated with regulation of myogenic differentiation of the cells.
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  • Jeman Kim, Toshiyuki Adachi, Miyuki Saiuchi, Akiko Asada
    1992 Volume 17 Issue 4 Pages 249-255
    Published: 1992
    Released on J-STAGE: April 19, 2006
    JOURNAL FREE ACCESS
    The effects of calcium and temperature on fusion of quail embryonic myoblasts were examined using cells transformed with a temperature-sensitive mutant of Rous sarcoma virus (ts-RSV). The transformed quail myoblasts (QM-RSV)fused to form myotubes at 41°C, the non-permissive temperature, but not at 35.5°C, the permissive temperature. On incubation at 41°C, a period of more than 10 hr was needed for the myoblasts to become fusion-competent, but calcium was not needed for development of fusion-competence. Once the cells had become competent, fusion proceeded even at 35.5°C. These results suggest that the src gene product expressed at 35.5°C may control the fusion of cells in the competent stage by inactivating a components) that is associated with fusion-competence. However, fusion of even myoblasts in the competent stage was blocked in calcium-deficient medium, suggesting that calcium is essential for the fusion, probably at a step immediately before membrane union. Unlike fusion, other biochemical processes of differentiation proceeded even in calcium-deficient medium, indicating a distinction of fusion from these other processes during myoblast differentiation.
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