Search PubMed⌕ Search

Biomedical subjects

M Tada

Publications and source records attributed to M Tada.

At least 37 records · Page 2Linked to original sources
PubMed2001

T-targets: clues to understanding the functions of T-box proteins.

Members of the T-box gene family have been identified in both vertebrates and invertebrates, where they play key roles in the regulation of embryonic development, and particularly in morphogenesis and the assignment of cell fate. T-box proteins act as transcription factors which regulate the expression of downstream effector genes. This review focuses on the identification of T-box target genes and the basis of T-box functional specificity.

Animals↗
PubMed2001

In vivo ESR study on hepatic reduction of a nitroxide radical after administration of glucose in rats.

The in vivo reducing ability of a nitroxide radical, 4-hydroxyl-2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPOL), in the liver of rats was estimated by using an electron spin resonance spectrometer equipped with a surface-coil-type resonator following administration of glucose. Both oral and intravenous administration of glucose significantly enhanced the reduction capacity. In vitro studies show that the reduction site of TEMPOL in the hepatic homogenate is located in the mitochondrial respiratory chain and microsomal electron transport system. These findings indicate that the enhancement of activity of these systems caused by the glucose administration prompts reduction of TEMPOL in the liver.

Animals↗
PubMed2001

Inactivate the remaining p53 allele or the alternate p73? Preferential selection of the Arg72 polymorphism in cancers with recessive p53 mutants but not transdominant mutants.

Several reports have noted epidemiological differences in the prevalence or prognostic significance of p53 mutants with arginine (R) or proline (P) at the codon 72 polymorphism (R72/P72) in certain cancer types, but the biological significance of these variants is unclear. The ability of p53 mutants to interact with and inactivate the p53 homolog p73 was recently reported to depend on the conformational state of the p53 protein and the residue at codon 72. Since the conformation of p53 mutants may influence their ability to transdominantly inhibit wild-type p53, we tested whether there was a correlation between the amino acid at codon 72 and the transdominance of p53 alleles found in tumors. The transdominance test was performed using a simple yeast transcription assay, and the amino acid at codon 72 was determined by sequencing. A total of 100 p53 mutants were tested. Compared with the germline frequency (R:P = 427:297), an extreme bias in favor of the R72 allele was observed with recessive mutants (R:P = 50:7, P < 0.0002), whereas no selection for the R72 allele was seen with transdominant mutants (R:P = 23:20). p53 and p73 are known to transactivate overlapping sets of target genes. We interpret the R72 bias with recessive mutants as evidence that decreased activation of p53 target genes provides a selective growth advantage to tumor cells during the stage of tumorigenesis in which a wild-type and mutant p53 allele coexist. We suggest that transdominant p53 mutants achieve this by inactivation of the remaining wild-type p53 allele, whereas recessive p53 mutants achieve it through inactivation of p73.

Alleles↗
PubMed2001

p73 is not mutated in meningiomas as determined with a functional yeast assay but p73 expression increases with tumor grade.

The p53 gene is normally wild type in meningiomas. Since all three members of the p53 gene family recognize the same DNA sequence, tumors containing wild type p53 could decrease transactivation of p53 target genes by mutating either p63 or p73. In meningiomas the most likely target is p73, because loss of heterozygosity of the chromosomal band containing p73 is the commonest genetic lesion in these tumors. To screen p73 for mutations we have developed a functional assay which tests the ability of p73 to activate transcription from a p53-responsive promoter in yeast. The assay correctly identified p73 mutants with mutations equivalent to hotspot mutations in p53, demonstrating that the assay can detect transcriptionally inactive p73. No mutations in p73 were identified in meningiomas. p73 RNA level was higher in more advanced tumors, but there was no correlation between the expression level of p73 and p21, a known p53 target gene. The yeast assay was also used to measure the intrinsic sensitivity of the p73 protein to mutagenesis. Like p53, p73 is exceptionally easy to inactivate as a transcription factor by point mutation. Taken together, these results indicate that p53 and p73 serve very different functions in tumors.

Aged↗
PubMed2001

In vitro and in vivo antibacterial activities of TAK-083, an agent for treatment of Helicobacter pylori infection.

The antibacterial activity of TAK-083 was tested against 54 clinical isolates of Helicobacter pylori and was compared with those of amoxicillin, clarithromycin, and metronidazole. The growth-inhibitory activity of TAK-083 was more potent than that of amoxicillin, clarithromycin, or metronidazole (the MICs at which 90% of the strains are inhibited were 0.031, 0.125, 64, and 8 microg/ml, respectively). The antibacterial activity of TAK-083 was highly selective against H. pylori; there was a >30-fold difference between the concentration of TAK-083 required to inhibit the growth of H. pylori and that required to inhibit the growth of common aerobic and anaerobic bacteria. Exposure of H. pylori strains to TAK-083 at the MIC or at a greater concentration resulted in an extensive loss of viability. When four H. pylori strains were successively subcultured in the medium containing subinhibitory concentrations of TAK-083, no significant change in the MICs of this compound was observed. TAK-083 strongly inhibited the formation of tryptophanyl-tRNA in H. pylori while exhibiting little effect on the same system in eukaryotes. TAK-083 was efficacious in the treatment of gastric infection caused by H. pylori in Mongolian gerbils. The results presented here indicate that TAK-083 is a promising candidate for the treatment of H. pylori infection.

Amoxicillin↗
PubMed2001

Toti-/pluripotential stem cells and epigenetic modifications.

The recent fascinating breakthrough in the area of stem cell research is the successful production of cloned animals via nuclear transplantation of somatic nucleus by intrinsic trans-acting factors of oocytes and trans-differentiation of somatic stem cells from adult organs induced by extrinsic growth factors. During the process of nuclear reprogramming, epigenetic modification of the somatic nuclei must be achieved to acquire toti-/pluripotential competence. However, the molecular mechanism involved is largely unknown. It has been shown that DNA methylation, histone acetylation and chromatin structure are involved in the establishment of epigenetic modification. Now it is evident that they function cooperatively to establish and maintain active or inactive chromatin state. Here we discuss the mechanisms of epigenetic modification potentially involved in the event of nuclear reprogramming.

Animals↗
PubMed2001

Isolation of plasma kallikrein by high efficiency affinity chromatography and its characterization.

We established a simple method for the purification of human plasma kallikrein (PK) by affinity chromatography and characterized it by analytical reverse phase-HPLC and Time of Flight Mass Spectroscopy (TOF-MS). The affinity resin (PKSI-Toyopearl) was synthesized using a selective synthetic inhibitor of plasma kallikrein (PKSI-527) as a ligand. The resin was found to have the highest efficiency in PK purification when the coupling ratio of PKSI-527 per resin was 9-14 micromol/g. PK was purified 466-fold with a yield of 83% from acetone-activated human plasma by affinity chromatography. The purity of PK thus obtained was confirmed by reverse phase-HPLC with a linear gradient of acetonitrile. The molecular weight of the purified PK was determined to be 86,151 by TOF-MS.

Chromatography, Affinity↗
PubMed2001

Structure-inhibitory activity relationship of plasmin and plasma kallikrein inhibitors.

Based on the structure of Tra-Tyr(O-Pic)-octylamide, a portion of the octylamine was replaced with moieties bearing hydrophobic, basic or acidic groups. Replacement of the C-terminal residue with a moiety bearing a hydrophobic group gave the proper affinity of the inhibitor to both plasmin (PL) and plasma kallikrein (PK). While addition of a basic residue did not improve the affinity of the inhibitor, a carboxylic acid attached to the phenyl ring increased the PK selectivity of the inhibitor.

Amines↗
PubMed2001

Accelerative effect of olive oil on liver glycogen synthesis in rats subjected to water-immersion restraint stress.

The effects of dietary oils on stress-induced changes in the liver glycogen metabolism of male Wistar rats at 6 weeks of age were investigated. The rats were subjected to repetitive water-immersion restraint and fed with a 20% saturated fatty acid mixture (PSC), olive oil (OLI), safflower oil (SAF), or linseed oil (LIS) diet. Stress loading decresed the body weight gain, although the food intake was hardly changed, and the weights of the liver and spleen generally declined regardless of the elapsed time after stress loading and the type of dietary oil. The adrenal weight was generally enhanced by stress in all deitary groups, and particularly tended to be greater in the OLI and PSC groups than in the other two. The plasma corticosterone concentration increased immediately after stressing (Stress-1), but approached the level of the rats with no stress (No stress) 2 h after releasing the stress load (Stress-2) in all groups. The enhancement of corticosterone level in the Stress-1 animals was large in the PSC and OLI groups, and the decline of this level in the Stress-2 animals was small in the OLI group when compared with the other groups. Although the concentrations of total cholesterol (T-CHOL) and triacylglycerol (TG) in the plasma were decreased by stress loading in all groups, these concentrations in the PSC and OLI groups were nearly always higher than in the other groups. The liver serine dehydratase (SDH) activity enhanced by stress was high in the OLI group and tended to be high in the PSC group when compared with the other groups. The contents of liver glycogen were reduced in the Stress-1 animals and extremely elevated in the Stress-2 animals of all groups, and particularly in the OLI group, the reduction in the Stress-1 animals was smaller and the enhancement in the Stress-2 animals was greater than in the other groups. These results suggest that feeding oleic acid to rats exposed to water-immersion restraint further accelerated liver glycogen synthesis through the rise in liver SDH activity due to increased corticosterone secretion when compared with the effect from linoleic and alpha-linolenic acids.

Animals↗
PubMed2001

ESR imaging on a solid-tumor-bearing mouse using spin-labeled dextran.

Imaging of a tumor with ESR was tried using two different types of spin probes, a low molecular weight spin probe, CPROXYL, and a polymer spin probe, TEMPO-DX. Spin probes were administered to a mouse bearing a solid tumor that was a transplanted Ehrlich's ascites carcinoma in the back, using two methods, conventional intraperitoneal injection and continuous intravenous injection with a micro-feeder. First, the accumulation of the probe was examined by X-band ESR. CPROXYL, which was administered to a mouse intraperitoneally, was exclusively retained in urine, showing that it was rapidly excreted into the bladder, while TEMPO-DX was absorbed from the peritoneal cavity with difficulty to the vessel. Using continuous intravenous injection, CPROXYL was also rapidly excreted, but it was confirmed that TEMPO-DX concentrated in tumor tissue because it has a long half-life in vivo. In addition, measurement of ESR imaging was done to measure the distribution of spin probes with continuous intravenous injection. The strongest spot of CPROXYL was observed on ESR images, showing the accumulation at the bladder, while the spot of TEMPO-DX was observed in the solid tumor of the back of the mouse. These results suggest that TEMPO-DX could stay much longer than a low molecular weight spin probe in vivo and concentrate at the tumor. TEMPO-DX may be useful for developing specific ESR imaging agents for tumor.

Animals↗
PubMed2001

Enhancement of endothelial nitric oxide production by chenodeoxycholic acids in patients with hepatobiliary diseases.

The purpose of this study was to clarify whether physiological concentrations of bile acids could affect endothelial nitric oxide production. We investigated the relationships between clinical concentrations of individual bile acids observed in patients with hepatobiliary diseases and endothelial nitric oxide production induced by each bile acid. Fifteen serum bile acids were measured using high-performance liquid chromatography combined with enzymatic fluorometry in 8 patients with liver cirrhosis, obstructive jaundice, and 8 healthy subjects. The effects of individual bile acids on nitric oxide production were examined in human umbilical endothelial cells by measuring the concentration of NO2- in the cultured medium. NO release in the blood was also determined by measuring the NO2-/NO3- concentration in these patients. In patients with hepatobiliary diseases, the plasma concentrations of chenodeoxycholic acid, ursodeoxycholic acid and cholic acid (free acid, taurine and glycine conjugates) were markedly elevated. Incubation of cells with chenodeoxycholic acid and deoxycholic acid (free acid, taurine and glycine conjugates) enhanced NO2- production in a concentration-dependent manner, while cholic acid (free and its conjugates) did not. The effects of individual bile acids on nitric oxide production were additive. Patients with liver cirrhosis and obstructive jaundice had higher plasma levels of NO2-/NO3- levels than the control subjects. These results suggest that increased plasma concentrations of chenodeoxycholic acid (free, taurine and glycine conjugates) in patients with hepatobiliary diseases may induce endothelial nitric oxide production. Thus, nitric oxide production induced by bile acids may be involved in the pathogenesis of circulatory abnormalities in patients with liver diseases.

Aged↗
PubMed2001

[Development of new hydrophilic catheter kit for self-catheterization: study in pediatric cases].

PURPOSE: To increase the management of self-catheterization in children of school age, a catheter kit consisting of hydrophilic catheter and a packet containing sterilized water was developed. We evaluated the lubricating characteristic and clinical efficacy of this new catheter kit. MATERIALS AND METHODS: The catheter kit used in the study was a pocket-size plastic container in which a polyurethane catheter coated with hydrophilic polymer and a packet containing sterilized water were packed in combination. The lubricating characteristic of catheter was assessed by the measurement of friction value. For clinical assessment, male children aged over 6 years old who were doing self-catheterization at 17 medical institutions nationwide were selected as the subjects. The 32 children who had given informed consent (mean age: 11.6 years old) were asked to use the catheter kit continuously for 1 week. The results were investigated by a questionnaire survey in which the assessment before and after the use was expressed in scores. At the same time, urinalysis and urine culture were examined. RESULTS: The friction value of hydrophilic catheter was equivalent to or less than that observed by applying a lubricant to the conventional catheter. The comparison of conventional catheter with the kit indicated significantly higher scores (assessment in 5 grades expressed in scores) for the portability and operability of the kit. Though there was no significant difference in the ease of insertion between the two catheters, there were several comments that the kit got stuck in the urethra when it was withdrawn. The global assessment gave a significantly higher score to the kit and 30 (94%) of the 32 children wanted to use the kit continuously. No increase in hematuria which caused a clinical problem or no new apparent urinary tract infection occurred after the use of the kit. CONCLUSIONS: Compared with the conventional catheter, the hydrophilic catheter kit highly satisfied a large number of children at the time of self-catheterization. Depending on the condition of children, the kit is considered useful for continued self-catheterization for a long term.

Child↗
PubMed2001

Frequent deletions and mutations of the beta-catenin gene are associated with overexpression of cyclin D1 and fibronectin and poorly differentiated histology in childhood hepatoblastoma.

Hepatoblastoma (HBL) is the most common malignant liver tumor in young children. Recent reports have shown that the beta-catenin gene was frequently mutated or deleted in HBLS: To elucidate the role of beta-catenin abnormalities in HBLs, we searched for mutations of beta-catenin and APC as well as expression of the target genes, cyclin D1, c-myc, and fibronectin, in 68 primary HBLS: The mutation analysis revealed that 44 (65%) tumors carried missense mutations or deletions of beta-catenin, all of which were somatic and targeted to the exon 3 encoding the amino acid residues involved in its degradation. However, no loss of function mutation of the APC gene was detected by the yeast functional assay. Of interest, beta-catenin mutation was significantly correlated with overexpression of the target genes, cyclin D1 and fibronectin, but not with that of c-myc in HBLs as measured by quantitative real-time reverse transcription-PCR. The immunohistochemical studies in 15 HBLs demonstrated that the nuclear/cytoplasmic accumulation of beta-catenin was positive in 13 tumors, 9 of which had the deletion or mutation of the gene. The significant correlation between the beta-catenin gene abnormality and the positive staining of cyclin D1 was also confirmed. Furthermore, the nuclear accumulation of beta-catenin was strongly associated with the poorly differentiated tumor cell components as well as with the positive staining of cyclin D1 within the tumor. Thus, our present results suggested that the gain of function mutation of beta-catenin played a crucial role in the malignant progression of HBL in vivo.

Adenomatous Polyposis Coli Protein↗
PubMed2000

Virulence factors of Helicobacter pylori responsible for gastric diseases in Mongolian gerbil.

Helicobacter pylori infection induces various gastroduodenal diseases. We examined the role of two genes, vacA and cagE, in the gastric pathogenesis induced by H. pylori using a long-term (62 wk) animal model. Reportedly, both genes are associated with the virulence of H. pylori: vacA encodes vacuolating cytotoxin, and cagE, with other genes in the cag pathogenicity islands, encodes a type IV secretion system. Mongolian gerbils were challenged in this study by a wild-type TN2 strain and its isogenic mutants of cagE or vacA. The wild-type and vacA mutants induced severe gastritis, whereas cagE mutants induced far milder changes. Gastric ulcer was induced at the highest rate (22/23) by the wild-type TN2, followed by the vacA mutant (19/28). No ulcer was found in the gerbils infected with the cagE mutant (0/27) or in controls (0/27). Intestinal metaplasia was also found in the gerbils infected with the wild-type (14/23) or vacA mutant (15/28). Gastric cancer developed in one gerbil with wild-type infection and in one with vacA mutant infection. In conclusion, the knocking out of the cagE gene deprived wild-type H. pylori of the pathogenicity for gastritis and gastric ulcer, suggesting that the secretion system encoded by cag pathogenicity island genes plays an essential role.

Adenocarcinoma↗
PubMed2000

c-Src regulates the interaction between connexin-43 and ZO-1 in cardiac myocytes.

Connexin-43 is known to interact directly with ZO-1 in cardiac myocytes, but little is known about the role of ZO-1 in connexin-43 function. In cardiac myocytes, constitutively active c-Src inhibited endogenous interaction between connexin-43 and ZO-1 by binding to connexin-43. In HEK293 cells, by contrast, a connexin-43 mutant lacking the Src phosphorylation site (Tyr265) interacted with ZO-1 despite cotransfection of a constitutively active c-Src. Moreover, in vitro binding assays using recombinant proteins synthesized from regions of connexin-43 and ZO-1 showed that the tyrosine-phosphorylated C terminus of connexin-43 interacts with the c-Src SH2 domain in parallel with the loss of its interaction with ZO-1. Cell surface biotinylation revealed that, by phosphorylating Tyr265, constitutively active c-Src reduces total and cell surface connexin-43 down to the levels seen in cells expressing a mutant connexin-43 lacking the ZO-1 binding domain. Finally, electrophysiological analysis showed that both the tyrosine phosphorylation site and the ZO-1-binding domain of connexin-43 were involved in the regulation of gap junctional function. We therefore conclude that c-Src regulates the interaction between connexin-43 and ZO-1 through tyrosine phosphorylation and through the binding of its SH2 domain to connexin-43.

Cell Line↗
PubMed2000

Development of plasmin and plasma kallikrein selective inhibitors and their effect on M1 (melanoma) and HT29 cell lines.

trans-4-Aminomethylcyclohexanecarbonyl-Tyr(O-Pic)-octylamide (YO-2) inhibited plasmin (PL) selectively, while trans-4-aminomethylcyclohexanecarbonyl-Phe-4-carboxymethylanili de (YO-1) inhibited plasma kallikrein (PK). YO-2 induced apoptosis of M1 (melanoma) cell line and HT29 colon carcinoma cells during 24 h through activation of caspase-3, while YO-1 did not affect either cell line even during 48 h.

Antineoplastic Agents↗
PubMed2000

Detection of PTEN nonsense mutation and psiPTEN expression in central nervous system high-grade astrocytic tumors by a yeast-based stop codon assay.

We have developed a new yeast-based assay for the detection of PTEN nonsense mutation, and applied it to a total of 42 astrocytic tumors. The assay utilizes homologous recombination of PCR-amplified PTEN cDNA samples to a yeast vector which expresses an in-frame PTEN::ADE2 chimera protein. An allele of nonsense mutation in the sample PTEN mRNA gives a truncated chimera protein in a yeast cell, resulting in the formation of a red colony. The assay and subsequent sequence analysis demonstrated nonsense mutations as red colonies of more than 10% in one of 10 anaplastic astrocytomas and six of 18 glioblastomas, but none in six pilocytic astrocytomas or in eight astrocytomas. Sequence analysis of white colonies showed one missense mutation in a glioblastoma. Interestingly, four of seven nonsense mutations were frame-shifts due to exon skipping. In addition, pink colonies were found in one of six pilocytic astrocytomas, three of eight astrocytomas, two of 10 anaplastic astrocytomas, and 10 of 18 glioblastomas. Sequence analysis of the pink colonies revealed a sequence similar to those reported as psiPTEN/PTH2. By testing mRNA and genomic DNA, it was found to be a processed pseudogene which was transcribed. The psiPTEN expression was complementary to PTEN mutation, for 14 of 18 glioblastomas showed either PTEN mutation or psiPTEN expression and only one case showed both PTEN mutation and psiPTEN expression (P<0.046), suggesting a pathological role of psiPTEN expression as an alternative to PTEN mutation in glioblastomas.

Astrocytoma↗