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Biomedical subjects

Takahiro Sakai

Publications and source records attributed to Takahiro Sakai.

15 recordsLinked to original sources
PubMed2006

The evaluation of problem-based learning (PBL) for three years.

PBL was evaluated in the course of nursing education for three years as problem solution, self-learning, integrated learning, and communication skills. The students who entered this school in 2000-2002 were examined. The students themselves evaluated each session and tutor, with the same evaluation format. In the three groups, the grand mean of the self-evaluation in each school year was elevated year-to-year (p < .001), while that of evaluated elements significantly increased (p < .001). Self-evaluation of communication skills became the highest. The usefulness of PBL is supported by using the evaluation scale the appropriate problems, and tutoring capabilities.

Education, Nursing↗
PubMed2005

Preparation and characterization of unique inorganic-organic hybrid mesoporous materials incorporating arenetricarbonyl complexes [-C6H4M(CO)3-] (M = Cr, Mo).

Unique inorganic-organic hybrid mesoporous materials incorporating arenetricarbonyl complexes [-C6H4M(CO)3-] (M = Cr, Mo) within their mesoporous frameworks have been successfully prepared by a simple CVD treatment of the phenylene-bridged organosilica mesoporous materials with metal hexacarbonyls [M(CO)6] (M = Cr, Mo). FT-IR and UV-vis investigations revealed that the arenetricarbonyl complexes exist stably even at temperatures above 473 K under vacuum.

Journal Article↗
PubMed2005

Origins of mouse inbred strains deduced from whole-genome scanning by polymorphic microsatellite loci.

Microsatellite loci are uniformly distributed at approximately 100-kbp intervals on all chromosomes except the chromosome Y, and genetic information about more than 9000 loci and high-throughput polymorphism analysis are now available. Taking advantage of these properties, we carried out whole-genome scanning using eight common inbred strains (CIS) of laboratory mice, including A/J, C57BL/6J, CBA/J, DBA/2J, SM/J, SWR/J, NC/Nga, and 129/SvJ, and eight wild-derived inbred strains (WIS), BGL2/Ms, CAST/Ei, JF1/Ms, MSM/Ms, NJL/Ms, PGN2/Ms, SK/CamEi, and SWN/Ms. We selected and located 1226 informative loci at 1.2-cM average intervals on all of the chromosomes of the 16 strains and compared the polymorphisms of the eight CIS with those from the eight WIS as subspecies representatives. More than 50% of the loci can be identified as WIS (therefore, subspecies-specific) alleles in the CIS genomes. We also discovered that the CIS chromosomes form a mosaic structure with an average ratio of domesticus to non-domesticus alleles of 3:1. Furthermore, the domesticus alleles were present much more frequently on the CIS chromosome X than on their autosomes, suggesting that successive backcrossing of non-domesticus stocks to domesticus stocks had been undergone at the beginning of CIS history.

Animals↗
PubMed2004

Identification of a protanomalous chimpanzee by molecular genetic and electroretinogram analyses.

We determined the structures of long (L)-wavelength-sensitive and middle (M)-wavelength-sensitive opsin gene array of 58 male chimpanzees and we investigated relative sensitivity to red and green lights by electroretinogram flicker photometry. One subject had protanomalous color vision, while others had normal color vision. Unlike in humans, a polymorphic difference in the copy number of the genes and a polymorphic base substitution at amino acid position 180 were not frequently observed in chimpanzees.

Animals↗
PubMed2004

Transforming growth factor-beta 1-induced apoptosis is blocked by beta 1-integrin-mediated mitogen-activated protein kinase activation in human hepatoma cells.

Growth factors and extracellular matrices cooperatively regulate cellular behavior. However, the interactions between transforming growth factor-beta 1 (TGF-beta 1) and integrins in hepatic cells are not fully understood. We investigated the effects of beta 1-integrin on TGF-beta 1-regulated growth of hepatoma cells. Human hepatoma cell lines HepG2, Huh7, and Hep3B were stably transfected with beta 1-integrin, and the parental, and mock- and beta 1-integrin-transfected hepatoma cells were treated with TGF-beta 1. Modulation of apoptosis and pathways involved in the process were investigated. TGF-beta 1 suppressed the growth of hepatoma cells, and apoptosis was observed in Hep3B and Huh7. Hepatoma cells transfected with beta 1-integrin were protected from TGF-beta 1-induced apoptosis. Mitogen-activated protein (MAP) kinase inhibitors, PD98059, SB203580, and SP600125, abolished this protective effect of beta 1-integrin, but herbimycin A and wortmannin were ineffective. Hepatoma cells overexpressing beta 1-integrin showed increased activities of MAP kinases, and TGF-beta 1 induced sustained activation of MAP kinases in these cells, but only transient activation in mock-transfected cells. These data suggest that MAP kinases activated by beta 1-integrin provide a strong anti-apoptotic signal during TGF-beta 1-induced apoptosis in human hepatoma cells. Therefore beta 1-integrin-mediated signals may contribute to the development and progression of hepatocellular carcinoma.

Apoptosis↗
PubMed2004

Update of mouse microsatellite database of Japan (MMDBJ).

We updated a database of microsatellite marker polymorphisms found in inbred strains of the mouse, most of which were derived from the wild stocks of four Mus musculus subspecies, M. m. domesticus, M. m. musculus, M. m.castaneus and M. m. molossinus. The major aim of constructing this database was to establish the genetic status of these inbred strains as resources for linkage analysis and positional cloning. The inbred strains incorporated in our database are A/J, C57BL/6J, CBA/J, DBA/2J, SM/J, SWR/J, 129Sv/J, MSM/Ms, JF1/Ms, CAST/Ei, NC/Nga, BLG2/Ms, NJL/Ms, PGN2/Ms, SK/CamEi and SWN/Ms, which have not or have only been poorly incorporated in the Whitehead Institute/MIT (WI/MIT) microsatellite database. The number of polymorphic microsatellite loci incorporated in our database is over 1,000 in all strains, and the URL site for our database is located at http:// www.shigen.nig.ac.jp /mouse/mmdbj/mouse.html.

Animals↗
PubMed2003

Induction of multiple matrix metalloproteinase genes in human hepatocellular carcinoma by hepatocyte growth factor via a transcription factor Ets-1.

Matrix metalloproteinases (MMPs) have been implicated in progression of hepatocellular carcinoma (HCC), as have hepatocyte growth factor (HGF) and its c-Met receptor. We investigated regulation of MMP gene expression by HGF in human HCC. Expression of mRNAs encoding MMPs, HGF and c-Met receptor was examined by quantitative reverse transcription-polymerase chain reaction (RT-PCR) in human HCC and in five human HCC cell lines. HCC cells were treated with HGF, and mRNA expression for MMPs and Ets-1 which activates transcription of MMPs was investigated. Ets binding activity was determined by gel mobility shift assay. MMP promoter activities were evaluated by reporter gene assay. Effects of Ets-1 antisense oligonucleotides were also examined. At the mRNA level, MMP-1, -3, -7 as well as c-Met were overexpressed in HCC compared with corresponding nonneoplastic liver tissues, although MMP-2, -9 or HGF were not. HGF dose-dependently induced Ets-1 together with an increased Ets binding activity, followed by transcription of MMP-1, -3, and -7. HGF increased MMP promoter activity, as did cotransfection with Ets-1. Ets-1 antisense oligonucleotide transfection down-regulated the MMP expression, and abolished induction by HGF. In conclusion, certain MMPs and c-Met, overexpressed in HCC cells, are induced by HGF via Ets-1. This pathway may contribute to tumor progression.

Journal Article↗
PubMed2003

Mechanism of beta 1-integrin-mediated hepatoma cell growth involves p27 and S-phase kinase-associated protein 2.

Although cooperative interactions between growth factors and integrins, cell surface receptors for extracellular matrices (ECM), have been reported, little is known about the interaction between hepatocyte growth factor (HGF) and integrin in hepatoma cells. We investigated the effects and mechanisms of integrin on the proliferation of hepatoma cells regulated by HGF. Human HepG2 hepatoma cells stably transfected with beta 1-integrin were treated with HGF and compared with parental and mock-transfected control cells. Cell proliferation and expression of cyclin-dependent kinase (Cdk) inhibitors and S-phase kinase-associated protein 2 (Skp2), were investigated. HGF dose-dependently suppressed the proliferation of parental and mock-transfected HepG2 cells. However, cells overexpressing beta 1-integrin exhibited increased proliferation in response to HGF. Although HGF increased p27 and decreased Skp2 expression in the parental and mock-transfected cells, the p27 and Skp2 levels in cells overexpressing beta 1-integrin were not altered by HGF. Interestingly, HepG2 cells overexpressing beta 1-integrin showed increased Skp2 expression. Furthermore, HGF did not reduce the proliferation of HepG2 cells transfected with antisense p27 or sense Skp2. Thus, HGF suppresses HepG2 cell proliferation by directly increasing p27 expression and indirectly decreasing Skp2 expression, and beta 1-integrin modulates the responsiveness of hepatoma cells to HGF via a p27-dependent manner by increasing Skp2. In conclusion, these results strongly suggest that integrin-mediated signals from the ECM can modulate growth factor-mediated signals in hepatoma cells, and may contribute to the growth of hepatocellular carcinomas.

Carcinoma, Hepatocellular↗
PubMed2003

Molecular phylogeny of Japanese Rhinolophidae based on variations in the complete sequence of the mitochondrial cytochrome b gene.

Microchiroptera have diversified into many species whose size and the shapes of the complicated ear and nose have been adapted to their echolocation abilities. Their speciation processes, and intra- and interspecies relationships are still under discussion. Here we report on the geographical variation of Japanese Rhinolophus ferrumequinum and R. cornutus using the complete sequence of the mitochondrial cytochrome b gene to clarify the phylogenetic positions of the 2 species as well as that of Rhinolophidae within the Microchiroptera. We have found that sequence divergence values within each of the 2 species are unexpectedly low (0.07%-0.94%). We have also found that there is no local specificity of their mtCytb alleles. On the other hand, the divergence values for Japanese Microchiroptera (12.7%-16.6%) are much higher than those for other mammalian genera. Similarly, the values among five genera of Vespertilionidae were 20.5%-27.3%. Phylogenetic analysis shows that the 2 species of family Rhinolophidae in the suborder Microchiroptera belong to the Megachiroptera cluster in the constructed maximum parsimony tree. These results suggest that the speciation of Rhinolophidae involved its divergence as an independent lineage from other Microchiroptera, and other microbats might be paraphyletic. In addition, the tree also shows that the order Chiroptera is monophylitic, and the closest group to Chiroptera is the ungulates.

Alleles↗
PubMed2002

Beta 1-integrin protects hepatoma cells from chemotherapy induced apoptosis via a mitogen-activated protein kinase dependent pathway.

BACKGROUND: beta 1-integrin modulates cellular phenotype by mediating signals from the extracellular matrix (ECM). Although overexpression of integrin molecules in hepatocellular carcinoma (HCC) has been reported, the role of overexpressed beta 1-integrin in the disease process of HCC is not fully understood. The authors investigated the effects of beta 1-integrin on apoptosis in hepatoma cells. METHODS: Human hepatoma cell lines HepG2, Huh7, and HLE were stably transfected with full-length beta 1-integrin. Cells underwent apoptosis induced by chemotherapeutic reagents, including cis-platinum (II)-diammine dichloride, etoposide, and docetaxel. Cell survival and intracellular signaling pathways dependent on beta 1-integrin-mediated apoptosis effects were analyzed by treating cells with PD98059 (ERK inhibitor), SB203580 (p38MAP kinase inhibitor), wortmannin (phosphatidyl inositol-3-kinase inhibitor), and herbimycin A (tyrosine kinase inhibitor). RESULTS: All three hepatoma cell lines overexpressing beta 1-integrin were protected from apoptosis induced by chemotherapeutic reagents, whereas parental or mock transfected cells were not. Treatment with PD98059 or SB203580 abolished the protective effect on apoptosis in cells overexpressing beta 1-integrin. Neither herbimycin nor wortmannin blocked the protective effects of beta 1-integrin overexpression. CONCLUSIONS: These data suggest that overexpression of beta 1-integrin confers resistance to apoptosis in hepatoma cells via a MAP kinase dependent pathway. beta1-integrin mediated signaling from the ECM in HCC cells may contribute to chemotherapy resistance.

Antineoplastic Agents↗
PubMed2002

Hepatocyte growth factor induces collagenase (matrix metalloproteinase-1) via the transcription factor Ets-1 in human hepatic stellate cell line.

BACKGROUND/AIMS: Although hepatocyte growth factor recently has been shown to decrease hepatic fibrosis in animal models, the molecular mechanisms of this effects remain to be elucidated. We investigated regulation of collagenase expression by hepatocyte growth factor in hepatic stellate cells. METHODS: A human hepatic stellate cell line, LI90, was treated with hepatocyte growth factor. Expression of collagenase, 72 kDa gelatinase, procollagen alpha 1(I), tissue inhibitor of matrix metalloproteinase-1, transforming growth factor-beta 1, or Ets-1, and carboxyterminal telopeptide of type I collagen was examined. Ets-1 binding activity was determined by gel mobility shift assay, collagenase promoter activity was evaluated by reporter gene assay. LI90 cells were also transfected with Ets-1 antisense oligonucleotides with or without hepatocyte growth factor. RESULTS: Hepatocyte growth factor increased expression of collagenase mRNA and protein, and an increase in Ets-1 mRNA preceded the increase in collagenase mRNA. Collagenase activity and protein, and a degradation product of type I collagen were increased in the medium. Nuclear extracts from treated LI90 cells also showed increased Ets-1 binding activity. Hepatocyte growth factor and cotransfection of Ets-1 enhanced promoter activity of collagenase gene. Furthermore, treatment of LI90 cells with Ets-1 antisense oligonucleotides downregulated basal and hepatocyte growth factor-induced Ets-1 and collagenase mRNA expression. CONCLUSIONS: Collectively, the results suggest that hepatocyte growth factor increases collagenase expression in hepatic stellate cells via the Ets-1 transcription factor-dependent manner.

Cell Line↗
PubMed2002

A case of primary leiomyoma of the liver in a patient without evidence of immunosuppression.

A 31-year-old Japanese male was admitted to our hospital for investigation of an asymptomatic nodular lesion of the liver detected by abdominal ultrasonography (US) during a routine medical examination. Computed tomography (CT) revealed a single, hypovascular mass 35 mm in diameter, within the left lobe of the liver. The tumor demonstrated hypointensity on T1-weighted, and hyperintensity on T2-weighted magnetic resonance (MR) imaging. Hematological and biochemical investigations were normal. There were no abnormalities of the gastrointestinal or urinary tracts. A left lateral segmentectomy of the liver was performed. Pathological examination of the nodule revealed a primary leiomyoma of the liver, with positive immunohistochemical staining for vimentin and desmin antigens. Primary leiomyoma of the liver is rare, with the majority of cases associated with immunodeficiency disorders. This patient had no evidence of any underlying disease. Primary leiomyoma of the liver should be considered when a nodular lesion is found in a patient without evidence of viral hepatitis.

Journal Article↗