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Biomedical subjects

K Imai

Publications and source records attributed to K Imai.

At least 289 records · Page 16Linked to original sources
PubMed2000

[A case with juvenile rheumatoid arthritis who developed cerebral vasculitis and venovascular hypertension].

On November, 1997, a 15-year-old boy visited our hospital because of headache, fever and arthralgia. He was treated with 5 mg/day of prednisolone thereafter. On October 21, 1998, he was admitted because of remittent fever and multiple arthralgia and diagnosis of juvenile rheumatoid arthritis (JRA) was made. He was also found to have hypertension of 210/110 mmHg, and soon developed ptosis of the eye, facial paresis and perceptive deafness of the right side. Cerebrospinal fluid showed protein of 98 mg/dl and mildly elevated IgG, IgA and IgM levels with normal cell count. Brain MRI examination revealed multiple cerebral lesions in the frontal, parietal and cerebellar areas on the right, whose cause was thought to be vasculitis. Renal angiography demonstrated a right renal artery stenosis, compatible with renovascular hypertension. He was treated with 60 mg of prednisolone per day, which brought about a satisfactory improvement of the above rheumatic and neurologic signs. On November 17, 1998, he received a follow-up study of MRI, which failed to show any cerebral lesions, supporting the effectiveness of prednisolone. An angiotensin converting enzyme inhibitor successfully normalized hypertension and renin activity in serum, although renal blood flow did not increase.

Adolescent↗
PubMed1999

Characterization of the human and mouse ETV1/ER81 transcription factor genes: role of the two alternatively spliced isoforms in the human.

The Ets transcription factors of the PEA3 group--E1AF/PEA3, ETV1/ER81 and ERM--are almost identical in the ETS DNA-binding and the transcriptional acidic domains. To accelerate our understanding of the molecular basis of putative diseases linked to ETV1 such as Ewing's sarcoma we characterized the human ETV1 and the mouse ER81 genes. We showed that these genes are both encoded by 13 exons in more than 90 kbp genomic DNA, and that the classical acceptor and donor splicing sites are present in each junction except for the 5' donor site of intron 9 where GT is replaced by TT. The genomic organization of the ETS and acidic domains in the human ETV1 and mouse ER81 (localized to chromosome 12) genes is similar to that observed in human ERM and human E1AF/PEA3 genes. Moreover, as in human ERM and human E1AF/PEA3 genes, a first untranslated exon is upstream from the first methionine, and the mouse ER81 gene transcription is regulated by a 1.8 kbp of genomic DNA upstream from this exon. In human, the alternative splicing of the ETV1 gene leads to the presence (ETV1 alpha) or the absence (ETV1 beta) of exon 5 encoding the C-terminal part of the transcriptional acidic domain, but without affecting the alpha helix previously described as crucial for transactivation. We demonstrated here that the truncated isoform (human ETV1 beta) and the full-length isoform (human ETV1 alpha) bind similarly specific DNA Ets binding sites. Moreover, they both activate transcription similarly through the PKA-transduction pathway, so suggesting that this alternative splicing is not crucial for the function of this protein as a transcription factor. The comparison of human ETV1 alpha and human ETV1 beta expression in the same tissues, such as the adrenal gland or the bladder, showed no clear-cut differences. Altogether, these data open a new avenue of investigation leading to a better understanding of the functional role of this transcription factor.

Amino Acid Sequence↗
PubMed1999

Aberrant methylation in gastric cancer associated with the CpG island methylator phenotype.

Aberrant methylation of 5' CpG islands is thought to play an important role in the inactivation of tumor suppressor genes in cancer. In colorectal cancer, a group of tumors is characterized by a hypermethylator phenotype termed CpG island methylator phenotype (CIMP), which includes methylation of such genes as p16 and hMLH1. To study whether CIMP is present in gastric cancer, the methylation status of five newly cloned CpG islands was examined in 56 gastric cancers using bisulfite-PCR. Simultaneous methylation of three loci or more was observed in 23 (41%) of 56 cancers, which suggests that these tumors have the hypermethylator phenotype CIMP. There was a significant concordance between CIMP and the methylation of known genes including p16, and hMLH1; methylation of p16 was detected in 16 (70%) of 23 CIMP+ tumors, 1 (8%) of 12 CIMP intermediate tumors, and 1 (5%) of 21 CIMP- tumors (P<0.0001). Methylation of the hMLH1 gene was detected in three of five tumors that showed microsatellite instability, and all three of the cases were CIMP+. The CIMP phenotype is an early event in gastric cancer, being present in the normal tissue adjacent to cancer in 5 of 56 cases. These results suggest that CIMP may be one of the major pathways that contribute to tumorigenesis in gastric cancers.

Adaptor Proteins, Signal Transducing↗
PubMed1999

Distinct methylation pattern and microsatellite instability in sporadic gastric cancer.

Aberrant 5' CpG island methylation is an alternative mechanism of gene inactivation during the development of cancer as demonstrated for several tumor-suppressor genes. Also, marked relationship of microsatellite instability (MSI) and DNA methylation has been reported in sporadic colorectal cancer, which is a result of epigenetic inactivation of hMLH1 in association of promoter hypermethylation. In the present study, we investigated the 5' CpG island hypermethylation of hMLH1, E-cadherin and p16 in 61 primary gastric cancers (GCs) by using combined bisulfite restriction analysis (COBRA) and methylation-specific PCR (MSP), and their MSI status. Of 61 GCs investigated, 5 (8.1%) tumors presented hMLH1 methylation, 16 (26.2%) and 25 (40.9%) showed E-cadherin and p16 methylation respectively, and 8 (13.1%) presented high-frequency MSI (MSI-H). Of the 8 MSI-H patients, 5 presented hMLH1 methylation, whereas no low-frequency MSI (MSI-L) and microsatellite stable (MSS) cases exhibited hMLH1 methylation (5/8 vs. 0/43, p < 0.00001). Furthermore, these patients also presented E-cadherin and p16 hypermethylation. Our data showed a significant correlation between hMLH1 methylation and MSI in GC, and suggested that a common mechanism of aberrant de novo methylation can be postulated in these cancers.

Adaptor Proteins, Signal Transducing↗
PubMed1999

Determination of cDNA, gene structure and chromosomal localization of the novel human 17beta-hydroxysteroid dehydrogenase type 7(1).

We have identified human 17beta-hydroxysteroid dehydrogenase type 7 (17beta-HSD 7). The novel human cDNA encodes a 37 kDa protein that shows 78 and 74% amino acid identity with rat and mouse 17beta-HSD 7, respectively. These enzymes are responsible for estradiol production in the corpus luteum during pregnancy, but are also present in placenta and several steroid target tissues (breast, testis and prostate) as revealed by RT-PCR. The human 17beta-HSD 7 gene (HSD17B7) consists of nine exons and eight introns, spanning 21. 8 kb and maps to chromosome 10p11.2 close to susceptibility loci for tumor progression, obesity and diabetes. The HSD17B7 promoter (1.2 kb) reveals binding sites for brain-specific and lymphoid transcription factors corresponding to additional expression domains in hematopoietic tissues and the developing brain as identified by in silico Northern blot.

17-Hydroxysteroid Dehydrogenases↗
PubMed1999

Protein kinase Calpha promotes apoptotic cell death in gastric cancer cells depending upon loss of anchorage.

Disruption of interactions between epithelial cells and extracellular matrix proteins leads to apoptosis of the cells, a phenomenon termed anoikis. Anoikis seems to play important roles in control of cellular positioning and inhibition of inappropriate cell growth. Here we found that a protein kinase C (PKC) activator phorbol ester 12-O-tetradecanoyl phorbol-13-acetate (TPA) promoted cell death in human gastric cancer cell lines MKN45 and MKN74 only when they lost anchorage. Loss of anchorage slightly increased enzymatic activity of PKCalpha, and an addition of TPA promoted cell death with further increase of PKCalpha activity, but not PKCbeta in MKN45 cells, implicating an involvement of PKCalpha in anoikis. Furthermore, vaccinia virus-mediated overexpression of PKCalpha strongly increased CPP32 activity in the detached MKN45 and MKN74 cells, and augmented anoikis, however it had little effect on viability and CPP32 activity in the attached cells. Taken together, PKCalpha promotes apoptotic cell death in gastric cancer cells depending upon loss of anchorage, thereby may be a modulator of anoikis.

Adenocarcinoma↗
PubMed1999

Wiskott-Aldrich syndrome protein induces actin clustering without direct binding to Cdc42.

WASP (Wiskott-Aldrich syndrome protein) was identified as the gene product whose mutation causes the human hereditary disease Wiskott-Aldrich syndrome. WASP contains many functional domains and has been shown to induce the formation of clusters of actin filaments in a manner dependent on Cdc42. However, there has been no report investigating what domain(s) is(are) important for the function. Here we present for the first time the results of detailed analyses on the domain-function relationship of WASP. First, the C-terminal verprolin-cofilin-acidic domain was shown to be essential for the regulation of actin cytoskeleton. In addition, we found that the clustering of WASP itself is distinct from actin clustering. The partial protein containing the region from the N-terminal pleckstrin homology domain to the basic residue-rich region also clustered especially around the nucleus as wild type WASP without inducing actin clustering. Finally, we obtained the quite unexpected result that a WASP mutant deficient in binding to Cdc42 still induced actin cluster formation, indicating that direct interaction between Cdc42 and WASP is not required for the regulation of actin cytoskeleton. This result may explain why no Wiskott-Aldrich syndrome patients have been identified with a missense mutation in the Cdc42-binding site.

Actin Depolymerizing Factors↗
PubMed1999

Increase in hepatic content of oleic acid induced by dehydroepiandrosterone in the rat.

The effects of dehydroepiandrosterone (DHEA) on the acyl composition of lipids in rat liver were studied. The content of oleic acid (18:1) in hepatic lipids was increased markedly by feeding rats a diet containing 0.5% (w/w) DHEA for 14 days. Treatment of rats with DHEA caused an increase in the activity of the terminal desaturase of the stearoyl-CoA desaturation system, without changing either the activity of NADH-cytochrome b5 reductase or the microsomal content of cytochrome b5. Among the changes observed in hepatic lipids, the increase in 18:1 content in phosphatidylcholine (PtdCho) was the most prominent; an approximately 2.5-fold increase in the proportion of 18:1 was induced at position 2, but not at position 1, by DHEA. This selective elevation of 18:1 at position 2 of PtdCho seems to be produced by the concerted actions of the induced 1-acylglycerophosphocholine (1-acyl-GPC) acyltransferase and the induced stearoyl-CoA desaturase. The content of 18:1 in serum lipids was unchanged by DHEA treatment, suggesting that secretion of lipids containing 18:1 into the circulation was not affected by DHEA. These results suggest that the elevation of hepatic content of 18:1 caused by DHEA treatment is mainly due to the induction of stearoyl-CoA desaturase.

Animals↗
PubMed1999

Overexpression of cyclooxygenase-2 protein is less frequent in gastric cancers with microsatellite instability.

Overexpression of cyclooxygenase-2 (COX-2) has been reported in gastric cancers. However, the relationship between expression of COX-2 and clinico-pathological or genotypic features has not been elucidated. To address the issue, expression of COX-2 protein was analyzed in 100 gastric cancers as well as 7 gastric cancer cell lines by using immunoblot analysis. Overexpression of COX-2 in cancer tissues compared with matched non-cancerous tissues was found in 70% of cases and was significantly associated with lymphatic involvement, lymph node metastasis and advanced tumor stage. Interestingly, overexpression of COX-2 was less frequent in gastric cancers with microsatellite instability (MSI) than in those without MSI (8/20 vs. 62/80, p < 0.01). Expression of COX-2 protein was detected in some gastric cancer cell lines without MSI at various levels, but not in those with MSI. Our results suggest that overexpression of COX-2 may play an important role in tumor progression of gastric cancer and also support the notion that gastric cancers with and without MSI represent distinctive pathways of carcinogenesis. We also observed a reduction of MSI phenotype after aspirin or sulindac treatment in a hMLH1-defective gastric cancer cell line SNU-1, which lacks COX-2 expression. Int. J. Cancer (Pred. Oncol.) 84:400-403, 1999.

Adaptor Proteins, Signal Transducing↗
PubMed1999

D-aspartate localization in the rat pituitary gland and retina.

Rat pituitary gland and retina were probed with anti-D-aspartate (D-Asp) antibody previously prepared in this laboratory [Lee et al., Biochem. Biophys. Res. Commun., 231 (1997) 505-508]. D-Asp immunoreactivity (IR) was observed only in the posterior lobe of the pituitary gland of 3-day-old rats, whereas the anterior and posterior lobes were also positive in 3-week and 6-week-old rats, respectively. In the anterior lobe, intense IR was scattered throughout the lobe and the D-Asp-positive cells appeared to be prolactin-containing cells or some other very closely related type of cell. In the retina, D-Asp IR was observed only in the ganglion cell and nerve fiber region of 3-day-old rats. In contrast, during the transient increase in D-Asp levels in 7-day-old rats, D-Asp IR was additionally evident in regions where differentiating bipolar cells had begun to make contact with other types of cells. The functional relevance of D-Asp localization in these tissues is discussed.

Animals↗
PubMed1999

TGF-beta inhibits lipopolysaccharide-stimulated activity of c-Jun N-terminal kinase in mouse macrophages.

Transforming growth factor-beta (TGF-beta) is a potent anti-inflammatory cytokine. Although this cytokine inhibits lipopolysaccharide (LPS)-mediated septic shock, the molecular mechanism of TGF-beta is not well known. Since recent studies showed that c-Jun N-terminal kinase (JNK), one of the mitogen-activated protein kinases, plays an important role in LPS signalling, we focused here on the inhibitory action of TGF-beta1 on LPS-stimulated JNK activity in mouse macrophages. TGF-beta1 inhibited LPS-stimulation of phosphorylated JNK1 and JNK2 and consequently of JNK activity in the cells. This JNK activity resulted in a decreased level of phosphorylated c-Jun protein. Using Western blotting, we also observed TGF-beta1 inhibition of newly synthesized c-Jun protein in LPS-stimulated cells. These results demonstrate that TGF-beta1 inhibits LPS-stimulated JNK activity in mouse macrophages. Also, our present study suggests a possible inhibitory mechanism of TGF-beta in signalling of LPS-induced inflammatory responses.

Animals↗
PubMed1999

Direct suppression of TCR-mediated activation of extracellular signal-regulated kinase by leukocyte protein tyrosine phosphatase, a tyrosine-specific phosphatase.

Leukocyte protein tyrosine phosphatase (LC-PTP)/hemopoietic PTP is a human cytoplasmic PTP that is predominantly expressed in the hemopoietic cells. Recently, it was reported that hemopoietic PTP inhibited TCR-mediated signal transduction. However, the precise mechanism of the inhibition was not identified. Here we report that extracellular signal-regulated kinase (ERK) is the direct target of LC-PTP. LC-PTP dephosphorylated ERK2 in vitro. Expression of wild-type LC-PTP in 293T cells suppressed the phosphorylation of ERK2 by a mutant MEK1, which was constitutively active regardless of upstream activation signals. No suppression of the phosphorylation was observed by LC-PTPCS, a catalytically inactive mutant. In Jurkat cells, LC-PTP suppressed the ERK and p38 mitogen-activated protein kinase cascades. LC-PTP and LC-PTPCS made complexes with ERK1, ERK2, and p38alpha, but not with the gain-of-function sevenmaker ERK2 mutant (D321N). A small deletion (aa 1-46) in the N-terminal portion of LC-PTP or Arg to Ala substitutions at aa 41 and 42 resulted in the loss of ERK binding activity. These LC-PTP mutants revealed little inhibition of the ERK cascade activated by TCR cross-linking. On the other hand, the wild-type LC-PTP did not suppress the phosphorylation of sevenmaker ERK2 mutant. Thus, the complex formation of LC-PTP with ERK is the essential mechanism for the suppression. Taken collectively, these results indicate that LC-PTP suppresses mitogen-activated protein kinase directly in vivo.

Calcium-Calmodulin-Dependent Protein Kinases↗
PubMed1999

Green tea and cancer chemoprevention.

Worldwide interest in green tea as a cancer preventive agent for humans has increased, because it is non-toxic and it is effective in a wide range of organs. (-)-Epigallocatechin gallate (EGCG) is the main constituent of green tea; the others are (-)-epicatechin gallate, (-)-epigallocatechin and (-)-epicatechin (EC). This paper reports the results of our latest pharmacological and biochemical studies with 3H-EGCG, along with studies on human subjects. The study on bioavailability of 3H-EGCG in mice revealed the wide distribution of radioactivity in multiple organs. Specifically, radioactivity was found in all reported target organs of EGCG and green tea extract (digestive tract, liver, lung, pancreas, mammary gland and skin) as well as other organs (brain, kidney, uterus and ovary or testes) in mice. Recently, we demonstrated that EC enhanced incorporation of 3H-EGCG into human lung cancer cell line PC-9 cells. EC along with another cancer preventive agent sulindac also synergistically enhanced apoptosis in PC-9 cells induced by EGCG. Moreover, a case-control study on breast cancer patients revealed that high daily consumption of green tea was associated with a lower recurrence rate among Stages I and II patients. All the results suggest that consumption of green tea is a practical and effective cancer preventive both before cancer onset and after cancer treatment.

3T3 Cells↗
PubMed1999

Association of matrilysin expression with recurrence and poor prognosis in human esophageal squamous cell carcinoma.

Matrix metalloproteinase-7 (matrilysin) has been implicated in tumor invasion and metastasis as well as tumor initiation and growth. In this study, we analyzed an association between immunohistochemically detected matrilysin expression at the invasive front in esophageal squamous cell carcinomas and clinicopathological characteristics and determined whether matrilysin predicts recurrence and/or survival Matrilysin expression at the invasive front was detected in 49% of 100 carcinoma tissues and was associated with the depth of invasion (P < 0.0001), advanced tumor stage (P = 0.0159), recurrences (P = 0.0002), and recurrences within the first postoperative year (P = 0.002). Patients with matrilysin-positive carcinoma had a significantly shorter disease-free and overall survival time than did those with a matrilysin-negative one (P < 0.0001). Matrilysin remained a significant predictive value for disease-free and overall survival in multivariate analysis, including conventional clinicopathological factors (P = 0.0007 and 0.0004, respectively). Our results suggest that matrilysin may play a key role in the progression of esophageal carcinoma and that its detection may be useful for the prediction of recurrence and poor prognosis and, possibly, for selecting patients for anti-matrix metalloproteinase therapy.

Carcinoma, Squamous Cell↗
PubMed1999

Stimulation of steroidogenic acute regulatory protein (StAR) gene expression by D-aspartate in rat Leydig cells.

D-aspartate and human chorionic gonadotropin act synergistically to increase testosterone production in purified rat Leydig cells, and D-aspartate stimulates testosterone synthesis even in the absence of human chorionic gonadotropin stimulation. In addition, D-aspartate enhances steady-state cellular mRNA and protein levels of steroidogenic acute regulatory protein, which is a key regulatory factor in gonadal and adrenal steroidogenesis. D-aspartate therefore appears to increase testosterone production in rat Leydig cells by stimulating steroidogenic acute regulatory protein gene expression. To our knowledge, this is the first report demonstrating a direct effect of D-aspartate on gene expression in mammalian cells.

Animals↗