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Volume 26 (2001)
- Issue 6 Pages 525-
- Issue 5 Pages 253-
- Issue 4 Pages 189-
- Issue 3 Pages 117-
- Issue 2 Pages 61-
- Issue 1 Pages 1-
Volume 26, Issue 4
Displaying 1-7 of 7 articles from this issue
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REVIEW
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Lisheng Zhuo, Koji KimataArticle type: scientific monograph
Subject area: Cell Structure and Function
2001 Volume 26 Issue 4 Pages 189-196
Published: 2001
Released on J-STAGE: November 09, 2001
JOURNAL FREE ACCESSCumulus oophorus, an investing structure unique to oocytes of higher mammals, is induced to synthesize an extensive extracellular matrix by ovulatory stimulus, leading to the characteristic preovulatory expansion of the cumulus-oocyte complex. The extracellular matrix consists of cumulus cell-secreted hyaluronan, proteoglycans and proteins, as well as extrafollicularly originated SHAPs (serum-derived hyaluronan-associated proteins) that are bound covalently to hyaluronan. The secretion and assembly of matrix molecules by cumulus cells are temporally regulated by factors derived from both mural granulosa cells and oocyte, which synchronize the deposition of the cumulus oophorus matrix with other intrafollicular ovulatory events. The cumulus oophorus matrix is essential for ovulation and subsequent fertilization. Recently, taking advantage of animal models with defined genetic modifications, it has become possible to investigate in vivo the structure of the cumulus oophorus matrix, the regulatory mechanism for matrix deposition and its biological functions. This review focuses on the recent findings on the construction of the cumulus oophorus matrix and the regulation.View full abstractDownload PDF (1314K)
REGULAR ARTICLES
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Kazuhiro Tetsuka, Ken-ichi Hosoya, Sumio Ohtsuki, Hitomi Takanaga, Nob ...Article type: scientific monograph
Subject area: Cell Structure and Function
2001 Volume 26 Issue 4 Pages 197-203
Published: 2001
Released on J-STAGE: November 09, 2001
JOURNAL FREE ACCESSTo characterize acidic amino acid transport in type 2 astrocytes, we established conditionally immortalized rat astrocyte cell lines (TR-AST) from newly developed transgenic rats harboring temperature-sensitive SV40 large T-antigen gene. TR-AST exhibited positive immunostaining for anti-GFAP antibody and A2B5 antibody, characteristics associated with type 2 astrocytes, and expressed glutamine synthetase. Acidic amino acid transporters, GLT-1 and system xC-, which consists of xCT and 4F2hc, were expressed in all TR-ASTs by RT-PCR. On the other hand, GLAST expression was found in TR-AST3 and 5. The characteristics of [3H]L-glutamic acid (L-Glu) uptake by TR-AST5 include an Na+-dependent and Na+-independent manner, concentration-dependence, and inhibition by L-aspartic acid (L-Asp) and D-aspartic acid (D-Asp). The corresponding Michaelis-Menten constants for the Na+-dependent and Na+-independent process were 36.3 μM and 155 μM, respectively. [3H]L-Asp and [3H]D-Asp uptake by TR-AST5 had an Na+-dependent and Na+-independent manner. This study demonstrated that GLT-1, system xC-, and GLAST were expressed in TR-AST, which has the characteristics of type 2 astrocytes and is able to transport acidic amino acids.View full abstractDownload PDF (214K) -
Atsuyuki Okuda, Masumi Ohtsu, Genki KimuraArticle type: scientific monograph
Subject area: Cell Structure and Function
2001 Volume 26 Issue 4 Pages 205-214
Published: 2001
Released on J-STAGE: November 09, 2001
JOURNAL FREE ACCESSA temperature-sensitive cell-cycle mutant of the 3Y1 rat fibroblast cell line, 3Y1tsD123 has in the D123 gene coding region a point mutation which causes instability of the D123 protein. Temperature-sensitive G1 arrest of the mutant is caused by increased degradation of the D123 protein at restrictive temperature. In this study we found that the selective proteasome inhibitors lactacystin and MG132 inhibited degradation of the mutated D123 protein in cell lines overexpressing the mutated D123 protein, followed by accumulation of a modified form (increased molecular weight other than by ubiquitination) of the D123 protein. Although a temperature-resistant revertant of the mutant had no further mutation in the D123 gene coding region, the modification of the mutated D123 protein was inhibited and the mutated D123 protein was rendered stable. The modification was also inhibited in the hybrid cell lines between the revertant and the cell line overexpressing the mutated D123 protein. These facts imply that the mutated D123 protein receives unidentified modification before degradation in the proteasome, and that the revertant expresses a gene inhibiting this modification.View full abstractDownload PDF (1816K) -
Ryoji Ishida, Rika Takashima, Takako Koujin, Masao Shibata, Naohito No ...Article type: scientific monograph
Subject area: Cell Structure and Function
2001 Volume 26 Issue 4 Pages 215-226
Published: 2001
Released on J-STAGE: November 09, 2001
JOURNAL FREE ACCESSIt is known that topoisomerase IIα is phosphorylated by several kinases. To elucidate the role of phosphorylation of topoisomerase IIα in the cell cycle, we have examined the cell cycle behavior of phosphorylated topoisomerase IIα in HeLa cells using antibodies against several phospho-oligopeptides of this enzyme. Here we demonstrate that serine1212 in topoisomerase IIα is phosphorylated only in the mitotic phase. Using an antibody against an oligopeptide containing phosphoserine-1212 in topoisomerase IIα (PS1212), subcellular localization of topoisomerase IIα phosphorylated at serine1212 was examined by indirect immunofluorescence staining, and compared with that of overall topoisomerase IIα. Serine1212-phosphorylated topoisomerase IIα was localized specifically on mitotic chromosomes, but not on interphase chromosomes; this result contrasts with overall topoisomerase IIα which was observed on chomosomes in both interphase and mitosis. Serine1212-phosphorylated topoisomerase IIα first appeared on chromosome arms in prophase, became concentrated on the centromeres in metaphase, and disappeared in early telophase. In addition, ICRF-193, a catalytic inhibitor of topoisomerase II, prevented accumulation of serine1212-phosphorylated topoisomerase IIα at the centromeres. These results indicate that serine1212 of topoisomerase IIα is phosphorylated specifically during mitosis, and suggest that the serine1212-phosphorylated topoisomerase IIα acts on resolving topological constraint progressively from the chromosome arm to the centromere during metaphase chromosome condensation.View full abstractDownload PDF (1459K) -
Kousuke Iba, Hideki Chiba, Toshihiko Yamashita, Seiichi Ishii, Norimas ...Article type: scientific monograph
Subject area: Cell Structure and Function
2001 Volume 26 Issue 4 Pages 227-233
Published: 2001
Released on J-STAGE: November 09, 2001
JOURNAL FREE ACCESSWe have recently reported that retinoic acid inhibits dexamethasone-induced alkaline phosphatase activity and mineralization in human osteoblastic cell line SV-HFO. In this study, we show that this inhibitory effect on alkaline phosphatase activity depends on the stage of cell differentiation; however, expression of tetranectin, which is a recently reported bone matrix protein, was completely inhibited by treatment with retinoic acid, irrespective of the stage of cell differentiation. Similarly, mineral deposit formation in SV-HFO cells was phase-independently inhibited by retinoic acid. To our knowledge, this is the first report that retinoic acid downregulates the tetranectin expression in human osteoblastic cells independent of the stage of cell differentiation, and is correlated with inhibition of mineralization.View full abstractDownload PDF (630K) -
Kingo Suzuki, Hidenobu Kato, Yasuyuki Sakuma, Hideo NamikiArticle type: scientific monograph
Subject area: Cell Structure and Function
2001 Volume 26 Issue 4 Pages 235-241
Published: 2001
Released on J-STAGE: November 09, 2001
JOURNAL FREE ACCESSIt was recently reported that intravenous administration of phorbol 12-myristate 13-acetate (PMA) showed a therapeutic effect in myelocytic leukemia patients. However, we previously observed that, in serum-free conditions, polymorphonuclear leucocytes (PMNs) were killed rapidly by exposure to PMA, suggesting the possibility of serious side effects. In this study, we found that PMA-induced necrosis of PMNs was prevented by serum, suggesting the existence of a "necrosis-suppressing factor". Next we tried to identify the serum factor. The hemopexins we purified were found to suppress necrosis of PMNs in a dose-dependent fashion. Hemopexins alone could not suppress necrosis, however, as it required the coexistence of another macromolecule such as albumin. Albumin promoted the suppressive activity of hemopexins in a dose-dependent fashion. These results strongly suggest that serum hemopexins may rescue mature PMNs from necrosis in the PMA-administered leukemia patient as previously reported, resulting in avoidance of serious side effects.View full abstractDownload PDF (203K) -
Muhammad Mujahid Khan, Masatoshi KomiyamaArticle type: scientific monograph
Subject area: Cell Structure and Function
2001 Volume 26 Issue 4 Pages 243-251
Published: 2001
Released on J-STAGE: November 09, 2001
JOURNAL FREE ACCESSIt has been known that isoforms of myosin essential light chain (LC) exhibit the isoform-specific sorting within cardiac myocytes and fibroblasts. In order to analyze which domain of LC is responsible for the sorting, various chimeric cDNA constructs between human nonmuscle isoform (LC3nm) and chicken fast skeletal muscle isoform (LC3f) were generated and expressed in cultured chicken cardiac myocytes. If chimeras contained LC3f sequence at the place that was restricted by BssHII and PstI, they were preferentially sorted to sarcomeres and precisely localized at A-bands, and their incorporation levels into the A-bands were identical with that of the wild type LC3f. However, other chimeras were distributed throughout the cytoplasm like the wild type LC3nm. Comparison of amino acid sequences revealed that 12 amino acids are different between chicken LC3f and human LC3nm in the BssHII-PstI fragment, and these amino acids are located within the second EF-hand of LC. These results indicated that the second EF-hand is responsible for the isoform-specific sorting of LC. Although the second EF-hand is not included in the key contacts with myosin heavy chain, it is supposed that this domain is important for the relative disposition of neighboring domains. Thus, the 12 amino acids in the second EF-hand might play a key role for modulation of overall configuration of LC, thereby influencing the precise association of the key contacts.View full abstractDownload PDF (1940K)
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