Cell Structure and Function
Online ISSN : 1347-3700
Print ISSN : 0386-7196
ISSN-L : 0386-7196
Volume 22, Issue 3
Displaying 1-9 of 9 articles from this issue
  • Hiroyoshi Takano, Tsuneyoshi Kuroiwa, Shigeyuki Kawano
    1997 Volume 22 Issue 3 Pages 299-308
    Published: 1997
    Released on J-STAGE: March 27, 2006
    JOURNAL FREE ACCESS
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  • Mitsuo Shimizu, Kazunobu Minakuchi, Satomi Kaji, Junichi Koga
    1997 Volume 22 Issue 3 Pages 309-315
    Published: 1997
    Released on J-STAGE: March 27, 2006
    JOURNAL FREE ACCESS
    It is well known that cellular interactions, such as cell adhesion, migration, invasion, between cells and the extracellular matrix are mediated by the integrin family of cell surface receptors. Chondrocytes are surrounded by an abundant extracellular matrix, but there is less information on the cellular receptors which interact with this matrix. In our studies, flbronectin, type I collagen, and type II collagen promoted haptotactic and chemotactic migration of Chondrocytes, as determined using a modified Boy den chamber system. Treatment of Chondrocytes with tyrosine kinase inhibitor, herbimycin or genistein, resulted in a dose dependent inhibition of migration toward these matrix proteins, whereas adhesion of Chondrocytes was not influenced. This indicated the existence of functional relationships between protein tyrosine phosphorylation and chondrocyte migration following the adhesion of Chondrocytes to matrix proteins. Further study showed that the peptide GRGDSP inhibited chondrocyte migration to fibronectin but not to collagens. On the other hand, Chondrocytes migrated toward the tetra-RGD containing peptide, but not the peptide GRGDSP, in a dose dependent fashion. These observations suggest that cross-linking or clustering of integrins is essential to induce transmembrane signaling related to tyrosine phosphorylation for chondrocyte migration toward fibronectin.
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  • Edesio J.T. Melo, Wanderley de Souza
    1997 Volume 22 Issue 3 Pages 317-323
    Published: 1997
    Released on J-STAGE: April 19, 2006
    JOURNAL FREE ACCESS
    Tachyzoites of Toxoplasma gondii multiplies within the parasitophorous vacuole (PV) of the host cell. Simultaneously with parasite division growth of the vacuole takes place. Using immunofluorescence microscopy and antibodies recognizing calreticulin, a nonmuscle functional analogue of calsequestrin, and a 76 kDa glycoprotein localized in the endoplasmic reticulum (ER), we showed the incorporation of ER elements of the host cell into parasitophorous vacuole containing-T. gondii. In addition enzyme cytochemistry showed that glucose-6-phosphatase, an enzyme marker of ER, is also localized within the PV. These observations suggest that growth of T. gondii - containing PV is at least in part due to incorporation of elements of the host cell ER into the vacuole.
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  • Harumi Hoshino, Atsushi Tamaki, Tatsuo Yagura
    1997 Volume 22 Issue 3 Pages 325-334
    Published: 1997
    Released on J-STAGE: March 27, 2006
    JOURNAL FREE ACCESS
    By means of a monoclonal antibody (mAbG3A5) against Golgi membrane glycoprotein, we have visualized the relative position of cytoplasmic polymerized microtubule bundles to Golgi stack cisternae in taxol treated HeLa cells, and found extensive fragmentation of the Golgi stack cisternae brought about by microtubule bundles. Within a 1 h period of taxol treatment, polymerization of cytoplasmic microtubules increased rapidly to form microtubule bundles, while the Golgi complex dispersed slightly along with the polymerized microtubule bundles. After 2 to 3 h taxol treatment the dispersal of the Golgi complex from the microtubule-organizing center (MTOC) to cytoplasmic periphery rapidly progressed in the direction which the microtubules ran. At early dispersal, the microtubule bundles were oriented apart from the stretched end of the Golgi stack cisternae and exhibited little direct contact with the Golgi stack cisternae membrane. The Golgi stack cisternae then began to wind around the microtubule bundles, followed by the beginning of fragmentation of the Golgi stack cisternae. At this step, some of the microtubules seemed to attach to a part of the Golgi stack cisternae. After prolonged exposure of cells to taxol (25 h) the microtubule bundles were highly developed throughout the cells and most of the Golgi fragments were trapped at their termini. In these cells, extensive fragmentation of Golgi stack cisternae occurred, resulting in small Golgi vesicles bound to the microtubule bundle.
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  • Hiroyuki Aizawa, Masazumi Sameshima, Ichiro Yahara
    1997 Volume 22 Issue 3 Pages 335-345
    Published: 1997
    Released on J-STAGE: March 27, 2006
    JOURNAL FREE ACCESS
    We transformed Dictyostelium discoideum cells by a vector for expression of a chimerical fusion protein consisting of Aequorea Victoria green fluorescent protein (GFP) and D. discoideum actin at its aminoand carboxy-terminal, respectively. The amount of expressed GFP-actin was about 3% of total actin molecules in the transformed cells. The expression of GFP-actin in D. discoideum completely inhibited cytokinesis in suspension culture. The expression decreased the rate of random cell locomotion to about a half of that of control cells. The expression also caused the cells to round up. These phenotypic observations suggested that GFP-actin acts as a dominant negative form of actin in the cells. The rounding up by expression of GFP-actin was suppressed by genetical elimination of myosin II heavy chain. This result suggested that myosin II is necessary for the rounding up of GFP-actin expressing cells. GFP-actin constructed cortical actin filament architectures together with intrinsic actin in the cells. Purified GFP-actin polymerized and de-polymerized repetitively according to the solution conditions in vitro. The critical concentration of GFP-actin for polymerization is the same as that of actin. The GFP-actin filaments was able to bind to coverglass surfaces coated with myosin head fragments. However, the GFP-actin filaments did not slide at all on the coverglass by addition of ATP. This indicates that the GFP-actin filaments form rigor complex with myosin II in vitro even in the presence of ATP. The formation of rigor complex may cause the cells to round up.
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  • Takashi Kojima, Chihiro Mochizuki, Toshihiro Mitaka, Yohichi Mochizuki
    1997 Volume 22 Issue 3 Pages 347-356
    Published: 1997
    Released on J-STAGE: March 27, 2006
    JOURNAL FREE ACCESS
    Melatonin has antiproliferative and antioxidant effects on cells in vivo and in vitro. Gap junctions mediate the communication between adjacent cells and are closely related to cellular growth and oxidative stress. We previously reported that 2% dimethylsulfoxide (DMSO) which has antiproliferative and antioxidative effects on hepatocytes, induces connexin 32 (Cx32) gap junction protein in primary cultures of adult rat hepatocytes. In the present study, we have examined the effects of melatonin on proliferation, oxidant stress and Cx32 gap junction protein expression in the cultured rat hepatocytes as compared to 2% DMSO treatment. 10-2 M melatonin significantly inhibited the proliferation and the oxidative stress of the cells, and markedly induced Cx32 gap junction protein expression and gap junctional intercellular communication (GJIC). These effects of 10-2 M melatonin treatment were not due to cytotoxicity to the cultured rat hepatocytes and they were as strong as those of 2% DMSO treatment. These results suggested that melatonin might be a useful substance to maintain the functions of the hepatocytes in vitro by modulating the levels of proliferation, oxidative stress and gap junction expression.
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  • Atsuko Iguchi, Ryuhei Okuyama, Masahito Koguma, Masuo Obinata, Nobuaki ...
    1997 Volume 22 Issue 3 Pages 357-364
    Published: 1997
    Released on J-STAGE: March 27, 2006
    JOURNAL FREE ACCESS
    Bone marrow is a major granulopoietic organ whose hematopoietic microenvironment is comprised of stromal cells. In the present work, we examined the regulation of in vitro granulopoiesis with an established line of bone marrow stromal cells. In coculture of the progenitor cells on the particular stromal cell lines from bone marrow, large granulocyte (G) colonies consisting of over 200 cells were formed without G-CSF for 5 days. Stromal cells supported development of Gr-1 (granulocyte specific surface marker)-negative progenitors into Gr-1 and myeloperoxidase positive granulocytes. Seventy percent of the large G-colonies were formed on the stromal layers even in the presence of anti-G-CSF antibody, which indicates the G-CSF independent pathway of granulopoiesis. Inhibition of the large G-colony formation by the addition of anti-adhesion molecules, such as very late activation antigen-4 (VLA-4) and CD31 (PECAM-1), suggested the role of cell-to-cell adhesion in stroma-supported granulopoiesis.
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  • Kwang Ho Cheong, Sang Dai Park, Jeman Kim, Seung Hwan Hong
    1997 Volume 22 Issue 3 Pages 365-377
    Published: 1997
    Released on J-STAGE: March 27, 2006
    JOURNAL FREE ACCESS
    We used a morphological approach to determine the topogenic role of the signal peptide in mediating the ER translocation of yeast prepro-α-factor. In prepro-α-factor-somatostatin hybrids, changes in the N-terminal amino acid sequence from wild-type NH2-Met-Arg-Phe (MRF) to NH2-Met-Phe-Lys (MFK) caused a subtle difference in protein trafficking in yeast cells (12). Immunofluorescence microscopy on semithin cryosections and immunoelectron microscopy on ultrathin sections showed that the transposition of the charged amino acid at N-terminus caused the precursors to be associated with either nucleus or mitochondria. This suggests that the secretory proteins are mistargeted to the irrelevant organelles as the result of inefficient ER translocation. Structural aspects of nuclear or mitochondrial targeting proteins and common principles in membrane translocation systems account for the mistargeting of overexpressed mutant hybrid precursors that are not rapidly translocated into the ER. Based on our immunocytochemical study on individual cells, we propose here that the positively charged N-terminal domain of signal peptide is important not merely in the efficiency of ER translocation, but also in appropriate targeting of peptide hormone precursors in yeast cells where post-translational ER translocation is known to occur frequently.
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  • Wei Zhang, Godfried M. Roomans
    1997 Volume 22 Issue 3 Pages 379-385
    Published: 1997
    Released on J-STAGE: March 27, 2006
    JOURNAL FREE ACCESS
    Changes in elemental content in response to muscarinic drugs in HT29 cells were investigated by X-ray microanalysis. Acetylcholine (ACh) and carbachol (Cch), both agonists binding to muscarinic receptors, induced a decrease of the intracellular Cl and K content. This agrees with the notion that these agonists induce electrolyte and water secretion. Atropine, a non-selective antagonist of muscarinic receptors, inhibited the decrease in K and Cl caused by ACh and Cch, and instead caused an increase of the Cl and K concentrations. A similar inhibition was found in the case of the selective muscarinic 3 receptor antagonist P-F-HHSiD. In contrast, the selective muscarinic 2 receptor antagonist AF-DX 116 did not inhibit Cch-activated secretion of K and Cl. A slight inhibition of ACh induced ion secretion was seen, but this inhibition was weak compared to that caused by P-F-HHSiD. Treatment with U-73122, an inhibitor of phospholipase C, blocked ACh or Cch induced ion secretion. These results suggest that ACh and Cch stimulated secretion of Cl and K is mediated by muscarinic 3 receptors via the inositol-1, 4, 5-trisphosphate (IP3) dependent pathway.
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