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Articles by M Shimizu
Total Records ( 3 ) for M Shimizu
  S Adachi , M Shimizu , Y Shirakami , J Yamauchi , H Natsume , R Matsushima Nishiwaki , S To , I.B Weinstein , H Moriwaki and O. Kozawa

We previously reported that (–)-epigallocatechin gallate (EGCG) in green tea alters plasma membrane organization and causes internalization of epidermal growth factor receptor (EGFR), resulting in the suppression of colon cancer cell growth. In the present study, we investigated the detailed mechanism underlying EGCG-induced downregulation of EGFR in SW480 colon cancer cells. Prolonged exposure to EGCG caused EGFR degradation. However, EGCG required neither an ubiquitin ligase (c-Cbl) binding to EGFR nor a phosphorylation of EGFR at tyrosine residues, both of which are reportedly necessary for EGFR degradation induced by epidermal growth factor. In addition, EGCG induced phosphorylation of p38 mitogen-activated protein kinase (MAPK), a stress-inducible kinase believed to negatively regulate tumorigenesis, and the inhibition of p38 MAPK by SB203580, a specific p38 MAPK inhibitor, or the gene silencing using p38 MAPK-small interfering RNA (siRNA) suppressed the internalization and subsequent degradation of EGFR induced by EGCG. EGFR underwent a gel mobility shift upon treatment with EGCG and this was canceled by SB203580, indicating that EGCG causes EGFR phosphorylation via p38 MAPK. Moreover, EGCG caused phosphorylation of EGFR at Ser1046/1047, a site that is critical for its downregulation and this was also suppressed by SB203580 or siRNA of p38 MAPK. Taken together, our results strongly suggest that phosphorylation of EGFR at serine 1046/1047 via activation of p38 MAPK plays a pivotal role in EGCG-induced downregulation of EGFR in colon cancer cells.

  S. E Wojcik , S Rossi , M Shimizu , M. S Nicoloso , A Cimmino , H Alder , V Herlea , L. Z Rassenti , K. R Rai , T. J Kipps , M. J Keating , C. M Croce and G. A. Calin

Cancer is a genetic disease in which the interplay between alterations in protein-coding genes and non-coding RNAs (ncRNAs) plays a fundamental role. In recent years, the full coding component of the human genome was sequenced in various cancers, whereas such attempts related to ncRNAs are still fragmentary. We screened genomic DNAs for sequence variations in 148 microRNAs (miRNAs) and ultraconserved regions (UCRs) loci in patients with chronic lymphocytic leukemia (CLL) or colorectal cancer (CRC) by Sanger technique and further tried to elucidate the functional consequences of some of these variations. We found sequence variations in miRNAs in both sporadic and familial CLL cases, mutations of UCRs in CLLs and CRCs and, in certain instances, detected functional effects of these variations. Furthermore, by integrating our data with previously published data on miRNA sequence variations, we have created a catalog of DNA sequence variations in miRNAs/ultraconserved genes in human cancers. These findings argue that ncRNAs are targeted by both germ line and somatic mutations as well as by single-nucleotide polymorphisms with functional significance for human tumorigenesis. Sequence variations in ncRNA loci are frequent and some have functional and biological significance. Such information can be exploited to further investigate on a genome-wide scale the frequency of genetic variations in ncRNAs and their functional meaning, as well as for the development of new diagnostic and prognostic markers for leukemias and carcinomas.

  M Yamaguchi , S. K Biswas , Y Kuwabara , M Ohkusu , M Shimizu and K. Takeo

The spindle pole body (SPB) in the interphase cell of the pathogenic yeast Cryptococcus neoformans was studied in detail by freeze-substitution and serial ultrathin sectioning electron microscopy. The SPB was located on the outer nuclear envelope and appeared either dumbbell- or bar shaped. The dumbbell-shaped SPBs were 228–365 nm long with amorphous spheres on each end, each sphere being 78–157 nm in diameter. The bar-shaped SPBs were 103–260 nm long and 32–113 nm thick. They consisted of filamentous materials. The dumbbell-shaped SPBs were more frequent (61%) than the bar-shaped SPBs. The bar-shaped SPBs may be regarded as dumbbell-shaped SPBs whose spherical parts became sufficiently small. There seemed to be no relationship between the SPB shape and the cell cycle stage of G1–G2, since both types of SPB appeared not only in unbudded cells but also in budded cells and their appearance seems to be random. It is not clear at present whether morphological changes between dumbbell- and bar shapes have any physiological function. The SPB tended to be localized away from the nucleolus (141° ± 44°), but localized randomly to the bud (97° ± 50°). The present study highlights the necessity of observing a large number of micrographs in three dimensions to describe accurately the ultrastructure of the SPB in yeast.

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