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Tadashi Kondo

Publications and source records attributed to Tadashi Kondo.

25 records · Page 2Linked to original sources
PubMed2003

Suppression of intestinal polyposis in Mdr1-deficient ApcMin/+ mice.

Aberrant transactivation of a certain set of target genes by the beta-catenin and T-cell factor/lymphoid enhancer factor complex has been considered crucial for the initiation of intestinal tumorigenesis. The human multidrug resistance (MDR)1 (ABCB1) gene contains multiple beta-catenin-T-cell factor4-binding elements in its promoter and is one of the immediate targets of the complex. In the current study, we have further substantiated the biological involvement of MDR1 in intestinal tumorigenesis based on the following evidence: (a) aberrant induction of the Mdr1a (Abcb1a) gene product, P-glycoprotein, associated with nuclear accumulation of the beta-catenin protein, was observed even in nascent microscopic adenomas of Min mice; (b) Mdr1-deficient Min (Apc(Min/+)Mdr1a/b(-/-)) mice developed significantly fewer intestinal polyps than did Apc(Min/+)Mdr1a/b(+/+) mice; and (c) Inhibitors of P-glycoprotein, verapamil, and cyclosporin A had a suppressive effect on the in vitro polypoid growth of IEC6 expressing stabilized (DeltaN89) beta-catenin protein. Inhibitors of P-glycoprotein may be included in a novel class of chemopreventive agents against colorectal carcinogenesis.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed2003

Application of sensitive fluorescent dyes in linkage of laser microdissection and two-dimensional gel electrophoresis as a cancer proteomic study tool.

The combination of laser microdissection and two-dimensional gel electrophoresis (2-D PAGE) has been developed to perform proteomic analysis on specific populations of cells in cancer tissues. However, as conventional low sensitivity silver staining was used for spot detection, the microdissection required to obtain an adequate amount of protein for 2-D PAGE is laborious and only a restricted number of protein spots could be visualized. As a consequence, this technology was impractical for direct clinical applications and had a limited impact on cancer studies. To solve these problems, we developed an application in which fluorescent dyes label the proteins extracted from microdissected tissues prior to 2-D PAGE separation. In this application, a small amount of protein, less than 6.6 microg, was enough to generate a 2-D profile with approximately 1500 protein spots. This technique was applied to compare the proteome of normal intestinal epithelium with that of adenoma in Min mice. Thirty-seven protein spots reproducibly showed significant differences in intensities. Mass spectrometric analysis and Western blotting identified eight of them, including prohibitin, 14-3-3zeta, tropomyosin 3 and Hsp84. These results indicate that fluorescence labeling of proteins from microdissected tissues prior to 2-D PAGE is a powerful cancer proteomic study tool.

Adenoma↗
PubMed2003

Reduction of hepatic ischemia/reperfusion-induced injury by a specific ROCK/Rho kinase inhibitor Y-27632.

BACKGROUND: The low-molecular-weight GTPase Rho is known to act as a molecular switch by activating several downstream effectors, one of which is Rho-associated coiled-coil forming protein kinase (ROCK). ROCK/Rho kinase mediates cytoskeleton-dependent cell functions, such as actomyosin-based smooth muscle contraction and integrin-mediated cell adhesion. A specific inhibitor of ROCK/Rho kinase, Y-27632, was recently developed. The present study examined whether Y-27632 could provide a beneficial effect on hepatic ischemia/reperfusion (I/R)-induced injury through the attenuation of microcirculatory disturbance. MATERIALS AND METHODS: In male Sprague-Dawley rats, normothermic partial ischemia was induced by clamping the hepatic pedicle to the left and median lobes for 90 min, followed by 2 h of reperfusion. In the treatment group, Y-27632 was intravenously administered prior to ischemic insult. Hepatic microcirculation was investigated by using intravital fluorescence microscopy. Liver enzyme release and histological changes of the liver tissue were also evaluated. RESULTS: Y-27632 significantly improved sinusoidal perfusion and reduced the number of leukocytes sticking in hepatic sinusoids and adhering in postsinusoidal venules. The postischemic narrowing of both sinusoids and postsinusoidal venules was also markedly suppressed. Consequently, liver enzyme release was reduced and postischemic histological damage was suppressed. CONCLUSIONS: A specific ROCK/Rho kinase inhibitor, Y-27632, was useful to alleviate hepatic I/R-induced injury through ameliorating postischemic microcirculation. The administration of Y-27632 may be a novel strategy for conquering hepatic I/R-induced injury.

Amides↗
PubMed2002

Activation of caspase-3 and cleavage of Rb are associated with p16-mediated apoptosis in human non-small cell lung cancer cells.

The p16 tumor suppressor gene is frequently inactivated in human cancer tissues and cell lines. We previously reported that wild-type p16 expression from an adenovirus vector (Adv/p16) induced p53-dependent apoptotic cell death in non-small cell lung cancer (NSCLC) cell lines. Here we show the potential mechanism of apoptosis induced by Adv/p16 infection. Infection of human NSCLC cell line A549, which carries the wild-type p53 gene, with Adv/p16 resulted in activation of caspase-3, accompanied by the cleavage of its substrate poly (ADP-ribose) polymerase (PARP), on day 3 of infection. The retinoblastoma (Rb) cell cycle regulator protein was also cleaved after activation of caspase-3; when the levels of Rb significantly diminished, apoptosis began. When A549 cells were pretreated with the caspase-inhibitory peptide N-acetyl-asp-Glu-Val-Asp-CHO (aldehyde) (Ac-DEVD-CHO), Adv/p16-mediated apoptosis and Rb cleavage were greatly inhibited. Furthermore, MDM2, a negative regulator of p53 expression was upregulated 3 days after Adv/p16 infection, and MDM2 was subsequently cleaved by caspase-3; MDM2 cleavage was inhibited by Ac-DEVD-CHO treatment. These data implied that cleavage of Rb, in addition to activation of caspase-3, represented a mechanism by which Adv/p16 induced apoptotic cell death in human NSCLC cells. Our results support the clinical relevance of Adv/p16 as a treatment for p16-null human NSCLC that express wild-type p53.

Adenoviridae↗
PubMed2002

Infrequent occurrence of age-dependent changes in CpG island methylation as detected by restriction landmark genome scanning.

Hypermethylation of CpG islands, resulting in the inactivation of tumor suppressor genes, is an early event in the development of some malignancies. Recent studies suggest that this abnormal methylation may be a function of aging. The number of CpG islands that methylate with age is unknown. We used restriction landmark genome scanning (RLGS) to approximate the extent to which CpG islands change methylation status during aging. Comparison of more than 2000 loci in T lymphocytes isolated from newborn, middle age, and elderly people revealed that 29 loci ( approximately 1%) changed methylation status during aging, with 23 increasing methylation, and six decreasing. The same subset also changed methylation status with age in the esophagus, lung, and pancreas, but in variable directions. Virtual genome scanning identified one of these loci as a member of the forkhead family, recently implicated in aging, and another as an EST fragment. The methylation status of both correlated with level of expression. Confirming studies in multiple tissues from normal and DNMT1(+/-) mice demonstrated only one age dependent change in the methylation of more than 2000 loci, occurring in liver and kidney. These results indicate that the methylation status of the majority of CpG islands in both mice and humans is tightly controlled during aging, and that changes are infrequent and in humans confined to a specific subset of genes.

Adult↗
PubMedDate not supplied

Metastable garnet in oceanic crust at the top of the lower mantle.

As oceanic tectonic plates descend into the Earth's lower mantle, garnet (in the basaltic crust) and silicate spinel (in the underlying peridotite layer) each decompose to form silicate perovskite-the 'post-garnet' and 'post-spinel' transformations, respectively. Recent phase equilibrium studies have shown that the post-garnet transformation occurs in the shallow lower mantle in a cold slab, rather than at approximately 800 km depth as earlier studies indicated, with the implication that the subducted basaltic crust is unlikely to become buoyant enough to delaminate as it enters the lower mantle. But here we report results of a kinetic study of the post-garnet transformation, obtained from in situ X-ray observations using sintered diamond anvils, which show that the kinetics of the post-garnet transformation are significantly slower than for the post-spinel transformation. Although metastable spinel quickly breaks down at a temperature of 1,000 K, we estimate that metastable garnet should survive of the order of 10 Myr even at 1,600 K. Accordingly, the expectation of where the subducted oceanic crust would be buoyant spans a much wider depth range at the top of the lower mantle, when transformation kinetics are taken into account.

Journal Article↗