Cell Structure and Function
Online ISSN : 1347-3700
Print ISSN : 0386-7196
ISSN-L : 0386-7196
Volume 18, Issue 6
Displaying 1-10 of 10 articles from this issue
  • Takako Kato, Osamu Kagami, Toshiki Yagi, Ritsu Kamiya
    1993 Volume 18 Issue 6 Pages 371-377
    Published: 1993
    Released on J-STAGE: March 27, 2006
    JOURNAL FREE ACCESS
    Two novel Chlamydomonas mutants, ida5 and ida6, that lack subsets of inner-arm dynein have been isolated and mapped to discrete loci on the right arm of linkage group XIV. Of the seven different innerarm dynein subspecies (a, b, c, d, e, /and g) identified by ion-exchange chromatography, ida5 lacks a, c, d and
    e, while ida6 lacks e alone; these are the only mutants that have been shown to lack subspecies e. Both strains can swim, albeit more slowly than the wild type. Hence, subspecies e must contribute to flagellar movement although it is unnecessary for the generation of undulating movement.
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  • Shigehiko Yumura
    1993 Volume 18 Issue 6 Pages 379-388
    Published: 1993
    Released on J-STAGE: March 27, 2006
    JOURNAL FREE ACCESS
    The distribution of actin and myosin II was studied by immunofluorescence microscopy in Dictyostelium discoideum cells that had been stimulated with a chemoattractant, cAMP. The amounts of actin but not of myosin II increased in the cortical region of cells after 5-10 seconds of stimulation by cAMP at 21°C (the first peak). After a transient decrease in the amount of actin in the cortical region, the amounts of both actin and myosin II increased in the cortical region after 25-35 seconds of stimulation (the second peak). The amounts of myosin II decreased in the cortical region thereafter but actin became localized in the pseudopods. The stimulated cells extended many short projections that contained actin at the time of the first peak and the cell bodies contracted at the time of the second peak. Foci in the cortical actin network decreased in number at 20-30 sec and recovered thereafter. A quantitative examination using a fluorocytometer revealed that the amounts of actin filaments in the cells increased at both peaks. The calcium ionophore A23187 and Ca2+ ion induced the reorganization of actin and myosin II to a certain extent. Furthermore, Ca2+ ions inhibited the return of myosin II to the endoplasm in CAMP-stimulated cells after preincubation with A23187. Thus, Ca2+ ions may play a dual role, being involved in the regulation of both the initiation and the termination of the reorganization of cytoskeletons. The cAMP-stimulated responses of cytoskeletons were not inhibited by EGTA, La3+ ions, or ruthenium red but were inhibited by preincubation with BAPTA-AM. These observations suggest that increase of Ca2+ ions from intracellular stores may play a crucial role in the response of cytoskeletons.
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  • Aiko Sakai-Wada, Shimako Yagi
    1993 Volume 18 Issue 6 Pages 389-397
    Published: 1993
    Released on J-STAGE: March 27, 2006
    JOURNAL FREE ACCESS
    The distribution of Ca2+ in dividing cells of the maize root tip was examined by potassium pyroantimonate precipitation and EGTA treatment methods. Ca2+ was found in most of the cell organelles, such as the matrix of the mitochondria, the thylakoid membrane of the proplastid and the Golgi vesicles, and on the plasma membrane. Ca2+ was also distributed throughout the cytoplasmic ground matrix and attractoplasm, inside the vacuoles, in the granular zone of the nucleolus in the interphasic nucleus and in the regenerated nucleolus in the telophasic nucleus. The amounts of Ca2+ distributed in the cytoplasmic ground matrix, the vacuole and the nucleolus varied during nuclear division. From the results of the present experiment, the following considerations on the role of Ca2+ and the regulation site of Ca2+ in dividing plant cells were drawn: 1) Ca2+ may play a role in the construction of the granular form of the ribosome. 2) Ca2+ may be an essential ion in the regeneration of nucleolus. 3) Vacuoles may act as the regulatory site of the Ca2+ concentration in the cytoplasm and attractoplasm in plant cells. Spindle microtubules and phragmo-microtubules are probably surrounded by other ions, such as Mg2+.
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  • Dorly de Freitas Buchi, Wanderley de Souza
    1993 Volume 18 Issue 6 Pages 399-407
    Published: 1993
    Released on J-STAGE: March 27, 2006
    JOURNAL FREE ACCESS
    Mouse peritoneal resident macrophages efficiently ingest IgG-coated erythrocytes through a phagocytic process mediated by Fc-receptors. During this process surface components of the macrophages, which can be labeled by cationized ferritin and gold-labeled lectins are not interiorized together with the IgGcoated erythrocytes. However, they are internalized through endocytic vesicles and concentrated into vacuoles which are part of the endosomal-lysosomal system. Later on some of these components either are recycled back to the cell surface or are released, due to a process of lysosome-phagosome fusion, into the erythrocyte-containing phagosomes.
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  • Masaharu Mori, Junjirou Tsuchiyama, Shigeru Okada
    1993 Volume 18 Issue 6 Pages 409-417
    Published: 1993
    Released on J-STAGE: March 27, 2006
    JOURNAL FREE ACCESS
    The proliferation of megakaryocytes, their migration, and their platelet release processes were observed in long-term bone marrow culture in collagen gel. Megakaryocytes proliferated for more than 6 months, not only with myeloid cells but also with sinusoid-like capillaries. The megakaryocyte count decreased at 2 weeks of culture, increased to more than 400 at 6 weeks, and then decreased to about 100. Megakaryocyte colonies appeared after 2 weeks of culture; the number increased to more than 10 at 4 weeks of culture, and was maintained at that level.
    Morphologically, most fully mature megakaryocytes extended several long antennae-like processes, with periodic constrictions, demarcation membranes (DM), and platelet fields. Pro-platelets were released from these processes primarily by a "pinching off" mechanism, but some megakaryocytes released pro-platelets by the dissociation of DM, without extending long processes. Mature megakaryocytes migrated like ameba in collagen gel, and a few migrated to the abluminal side of the capillary or into the capillary; in both cases releasing pro-platelets into the capillary lumina. These observations were very similar to those noted in vivo.
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  • Hideki Chiba, Norimasa Sawada, Masahito Oyamada, Takashi Kojima, Shint ...
    1993 Volume 18 Issue 6 Pages 419-426
    Published: 1993
    Released on J-STAGE: March 27, 2006
    JOURNAL FREE ACCESS
    We examined i) the kinds of connexins, component proteins of gap junctions, that are expressed in osteoblasts and ii) the relationship between the expression of gap junctions and osteoblastic phenotype during cell proliferation and after the treatment with 1α, 25-dihydroxyvitamin D3. Human osteoblastic cells with (SV-HFO) or without (HFO) transformation by simian virus 40 and mouse osteoblast-like cells (MC3T3-E1) expressed connexin 43 (Cx43), but not Cx26 or Cx32, as revealed by Northern blot analysis and immunocytochemistry. The expression of Cx43 was significantly higher in SV-HFO cells in the confluent phase than in the proliferative phase. Similarly, the expression of alkaline phosphatase (ALP) and osteocalcin in SV-HFO cells in the confluent phase were higher than those in the proliferative phase. On the other hand, treatment of lα, 25-dihydroxyvitamin D3 did not change the expression of Cx43 in SV-HFO cells, but significantly induced the expression of ALP and osteocalcin. These results showed that the expression of gap junction protein in osteoblastic cells was coupled with cell differentiation in association with the expression of osteoblastic phenotype, but that the connexin expression is regulated in a way different from that of ALP and osteocalcin.
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  • Katsuji Miyauchi, Akitsugu Yamamoto, Ryuichi Masaki, Yukio Fujiki, Yut ...
    1993 Volume 18 Issue 6 Pages 427-436
    Published: 1993
    Released on J-STAGE: March 27, 2006
    JOURNAL FREE ACCESS
    We investigated the subcellular distribution of microsomal aldehyde dehydrogenase (msALDH) in rat liver and revealed by the immunoblotting method that msALDH or a cross-reacting 54-kDa protein(s) exists in the outer mitochondrial membranes and peroxisomes. Anti-msALDH antibody markedly inhibited the decanal aldehyde dehydrogenase activity of the outer mitochondrial membranes as well as that of the microsomes. Immunogold electron microscopic observations showed that gold particles are localized over the ER, outer mitochondrial membranes and peroxisomal membranes. These results suggest that msALDH or its crossreacting related protein is distributed not only in the ER membranes but also in the mitochondrial outer membranes and peroxisomal membranes.
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  • Tohru Marunouchi, Hiromi Hosoya
    1993 Volume 18 Issue 6 Pages 437-447
    Published: 1993
    Released on J-STAGE: March 27, 2006
    JOURNAL FREE ACCESS
    The transcription of hsc70, a cognate member of the hsp70 gene family, is suppressed in the terminally differentiated human histiocytic lymphoma cell line, U937, and appears to be regulated in the absence of heat shock. We have examined the 5' upstream regulatory region of 450 bp which contains a putative regulatory sequence of 18 bp in addition to known cis-elements such as HSEs, CCAAT boxes, Sp1 binding sites and AP2 binding sites. The 18 bp cis-element formed larger complexes with nuclear localized transfactors when extracts were prepared from differentiated rather than from proliferating cells.
    These larger complexes were also detected in nuclear extracts of serum-deprived cells, suggesting that such complexes may be related to the suppression of hsc70 gene transcription in Go arrested cells.
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  • Kohzaburo Fujikawa-Yamamoto, Kouhei Teraoka, Shizuo Odashima
    1993 Volume 18 Issue 6 Pages 449-455
    Published: 1993
    Released on J-STAGE: March 27, 2006
    JOURNAL FREE ACCESS
    The cellular responses of the V79 cell cycle to K-252a, a protein kinase inhibitor, were examined by flow cytometry (FCM) and by time-lapse videomicrography. At a concentration of 0.5 μM of K-252a for 72 h, V79 cells became hyperploid, having above 32c DNA content. The cycle times in the hyperploidizing process were 11.2 (4c-8c), 16.3 (8c-16c) and 19.3 (16c-32c) hours, values which were less than twice that of the control (10.5 h). After the washout of K-252a, the DNA content was widely distributed in the V79 cell population and hyperploid V79 cells reduced DNA content through a variety of cell division modes. These cellular responses to hyperploidization of V79 cells by K-252a were in reasonable agreement with those by demecolcine.
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  • Kazuyoshi Nakanishi, Hwang Yong-Il, Haruko Ishiwatari, Yasunari Takami ...
    1993 Volume 18 Issue 6 Pages 457-465
    Published: 1993
    Released on J-STAGE: March 27, 2006
    JOURNAL FREE ACCESS
    A rat embryo fibroblast (REF) cDNA expression library was transfected into 3Y1 cells transformed by human papillomavirus type 18 E6 and E7 genes and 10 flat revertants were isolated. These revertants expressed the same levels of E6 and E7 mRNA as the parent cells, but had greatly reduced ability to form colonies in soft agar. Suppression of transformation was dominant in cell hybrids generated by fusing each revertant with the parental transformed cells. Furthermore, loss of transfected cDNA was observed in re-transformed cell hybrids derived from one flat revertant. Over expression of the CDNA suppresses the colony-forming efficiency of the cells transformed by E6 and E7 genes.
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