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Biomedical subjects

Y Mizukami

Publications and source records attributed to Y Mizukami.

At least 19 recordsLinked to original sources
PubMed2007

Gemcitabine chemoresistance and molecular markers associated with gemcitabine transport and metabolism in human pancreatic cancer cells.

To identify predictive molecular markers for gemcitabine resistance, we investigated changes in the expression of four genes associated with gemcitabine transport and metabolism during the development of acquired gemcitabine resistance of pancreatic cancer cell lines. The expression levels of human equilibrative nucleoside transporter-1 (hENT1), deoxycytidine kinase (dCK), RRM1, and RRM2 mRNA were analysed by real-time light cycler-PCR in various subclones during the development of acquired resistance to gemcitabine. Real-time light cycler-PCR demonstrated that the expression levels of either RRM1 or RRM2 progressively increased during the development of gemcitabine resistance. Expression of dCK was slightly increased in cells resistant to lower concentrations of gemcitabine, but was decreased below the undetectable level in higher concentration-resistant subclones. Expression of hENT1 was increased in the development of gemcitabine resistance. As acquired resistance to gemcitabine seems to correlate with the balance of these four factors, we calculated the ratio of hENT1 x dCK/RRM1 x RRM2 gene expression in gemcitabine-resistant subclones. The ratio of gene expression decreased progressively with development of acquired resistance in gemcitabine-resistant subclones. Furthermore, the expression ratio significantly correlated with gemcitabine sensitivity in eight pancreatic cancer cell lines, whereas no single gene expression level correlated with the sensitivity. These results suggest that the sensitivity of pancreatic cancer cells to gemcitabine is determined by the ratio of four factors involved in gemcitabine transport and metabolism. The ratio of the four gene expression levels correlates with acquired gemcitabine-resistance in pancreatic cancer cells, and may be useful as a predictive marker for the efficacy of gemcitabine therapy in pancreatic cancer patients.

Antimetabolites, Antineoplastic↗
PubMed2004

[Familial spontaneous pneumothorax].

A case of familial spontaneous pneumothorax was reported. A 52-year-old man was referred to our hospital complaining of exertional dyspnea. He had experienced right spontaneous pneumothorax and cured with tube drainage last year. Five of his 7 brothers and his son too had had spontaneous pneumothorax. Chest X-ray film and computed tomography (CT) scan on admission showed giant bulla of the left lung with compression of normal lungs. Pulmonary function studies revealed obstructive pulmonary disease and mild hypoxemia. Partial resection of the lung with open thoracotomy surgery was performed. Air leaks sealed in 14 days and the patient discharged the hospital with inadequate expansion of the left lung. Three years later the patient experienced right hemicolectomy for colon cancer and died for recurrence 7 years later with adequate expansion of the left lung.

Humans↗
PubMed2003

Detection of Japanese yam mosaic virus by RT-LAMP.

Arapid and simple procedure is described to detect the genomic RNA molecule of Japanese yam mosaic potyvirus (JYMV). This method, named RT-LAMP, allows direct detection of RNA from infected plants without careful RNA extraction, rapid thermal cycling and gel electrophoresis. RT-LAMP was successfully applied to leaves, propagules and roots of Japanese yam infected with JYMV. One of the characteristics of the RT-LAMP method is its ability to synthesize an extremely large amount of DNA. Accordingly, a large amount of by-product, pyrophospate ion, is produced yielding a white precipitate of magnesium pyrophosphate in the reaction mixture. The presence or absence of this white precipitate allows easy detection of the amplification of JYMV genomic RNA without gel electrophoresis.

Base Sequence↗
PubMed2001

Requirement of c-jun N-terminal kinase for apoptotic cell death induced by farnesyltransferase inhibitor, farnesylamine, in human pancreatic cancer cells.

Farnesyltransferase inhibitors (FTIs) represent a novel class of anticancer drugs and are now in clinical trial. We have previously shown that farnesylamine, synthetic isoprenoid-linked with "amine" which acts as a potent FTI, induces apoptosis in human pancreatic cancer cells through the ras signaling cascade. Since the effect of FTI is usually "cytostatic" rather than "cytotoxic", we speculated another apoptotic machinery of farnesylamine in addition to the effect of FTI. Farnesylamine induced sustained activation of c-jun N-terminal kinase (JNK), which was not caused by other FTI, FTI-277. Blockage of JNK activity by dominant-negative mutant abrogated the DNA laddering and significantly reduced "cytotoxic" effect of farnesylamine. Strikingly similar effect on JNK activation and apoptosis was induced by structurally related long-chain fatty amine (LFA), oleylamine, but not by farnesol, an isoprenoid analogue of farnesylamine without "amine." Taken together, apoptosis induction through JNK activation by farnesylamine based on the LFA structure rather than an effect of FTI.

Alkyl and Aryl Transferases↗
PubMed2001

Dietary iron reduces the anti-convulsion activity of phenytoin in electroconvulsion via inhibition of brain penetration.

We determined the anti-convulsion activity of phenytoin (PHT) using the maximum electron shock method in mice fed diets containing various concentrations of iron for 18 weeks. Dietary iron reduces the anti-convulsion activity of PHT in a dose-dependent manner (0-6100 ppm). High concentrations of PHT are detected in the plasma of mice fed a high iron diet compared with those fed normal and low iron diets, in contrast to the pharmacological effect. However, the concentration of PHT in the brains of mice fed high amounts of dietary iron decreased significantly 3 h after treatment with PHT, consistent with the anti-convulsion effect of PHT. The relationship between brain and plasma-unbound concentrations of PHT indicates that the penetration of PHT into brain is significantly inhibited by dietary iron.

Animals↗
PubMed2001

Clonality and field cancerization in intraductal papillary-mucinous tumors of the pancreas.

BACKGROUND: Multiple lesions of intraductal papillary-mucinous tumor of the pancreas (IPMT) in the same pancreas often are encountered. To elucidate field (multicentric) cancerization and clonality of IPMT, clonal analyses of IPMT and its precursor lesion of ductal hyperplasia were performed. K-ras codon 12 mutations and X-chromosome inactivation of human androgen receptor gene (HUMARA) were investigated. METHODS: Paraffin embedded tissue samples from the pancreata of 37 patients who underwent resection for IPMTs were microdissected manually or by laser capture microdissection. Multiple samples from each surgical specimen were microdissected representing each IPMT and discrete ductal hyperplasias. DNA was extracted, and K-ras codon 12 mutations were examined by two-step polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). The mutations were analyzed by direct DNA sequence. The HUMARA locus was digested with or without HpaII and HhaI prior to amplification. The HUMARA assay was conducted by fluorescence-labeled PCR-RFLP and was analyzed with specialized software. RESULTS: All 37 pancreata had at least two lesions of ductal hyperplasia, and 23 of 37 pancreata (62%) had K-ras codon 12 mutations in these precursor lesions. Of 23 pancreata with mutated K-ras hyperplasia, 15 (65%) had multiple, distinct mutations in different lesions of hyperplasia in the same pancreas, suggesting a field defect. Thirty-two of 37 IPMTs (86%) had K-ras codon 12 mutations. Among these, 16 IPMTs (50%) had multiple, distinct mutations at K-ras codon 12. The HUMARA assay showed that 12 of 15 IPMTs were informative, and 9 were considered polyclonal and/or oligoclonal origin in origin. With the combined results of multiple K-ras mutation detection and the HUMARA assay, 12 of 15 IPMTs from female patients (80%) were considered polyclonal and/or oligoclonal in origin. CONCLUSIONS: The current results suggest that multiple, distinct K-ras mutations of different ductal hyperplasias in a given pancreas are due to a field (multicentric) cancerization effect in IPMTs. Thus, most of IPMTs are polyclonal and/or oligoclonal in origin, i.e., IPMTs may originate from multiple (molecularly distinct) precursor lesions.

Adenocarcinoma, Mucinous↗
PubMed2001

Phosphorylation of proteins and apoptosis induced by c-Jun N-terminal kinase1 activation in rat cardiomyocytes by H(2)O(2) stimulation.

Cytokines and various cellular stresses are known to activate c-Jun N-terminal kinase-1 (JNK1), which is involved in physiological function. Here, we investigate the activation of JNK1 by oxidative stress in H9c2 cells derived from rat cardiomyocytes. H(2)O(2) (100 microM) significantly induces the tyrosine phosphorylation of JNK1 with a peak 25 min after the stimulation. The amount of JNK1 protein remains almost constant during stimulation. Immunocytochemical observation shows that JNK1 staining in the nucleus is enhanced after H(2)O(2) stimulation. To clarify the physiological role of JNK1 activation under these conditions, we transfected antisense JNK1 DNA into H9c2 cells. The antisense DNA (2 microM) inhibits JNK1 expression by 80% as compared with expression in the presence of the sense DNA, and significantly blocks H(2)O(2)-induced cell death. Consistent with the decrease in cell number, we detected condensation of the nuclei, a hallmark of apoptosis, 3 h after H(2)O(2) stimulation in the presence of the sense DNA for JNK1. The antisense DNA of JNK1 inhibits the condensation of nuclei by H(2)O(2). Under these conditions, the H(2)O(2)-induced phosphorylation of proteins with molecular masses of 55, 72, and 78 kDa is blocked by treatment with the antisense DNA for JNK1 as compared with the sense DNA for JNK1. These findings suggest that JNK1 induces apoptotic cell death in response to H(2)O(2), and that the cell death may be involved in the phosphorylations of 55, 72, and 78 kDa proteins induced by JNK1 activation.

Animals↗
PubMed2001

Phosphoinositide 3-kinase accelerates necrotic cell death during hypoxia.

Using H9c2 cells derived from rat cardiomyocytes, we investigated the mechanism of cell death during hypoxia in the presence of serum and glucose. Hypoxic cell death is by necrosis and is accompanied by metabolic acidosis. Moreover, hypoxic cell death is inhibited by Hepes buffer as well as by 2-deoxyglucose, an inhibitor of glycolysis, indicating that metabolic acidosis should play an essential role in hypoxic injury. The involvement of phosphoinositide 3-kinase (PI 3-kinase), which is known to activate glucose metabolism, was examined using its inhibitor, LY290042, or adenovirus-mediated gene transfer. Hypoxic cell death was inhibited by LY294002 in a dose-dependent manner. Overexpression of dominant negative PI 3-kinase was found to reduce cell death, whereas wild-type PI 3-kinase enhanced it. Dominant negative PI 3-kinase also reduced glucose consumption and acidosis, but this was stimulated by wild-type PI 3-kinase. The data indicate that PI 3-kinase stimulates cell death by enhancing metabolic acidosis. LY294002 significantly reduced glucose uptake, showing that PI 3-kinase regulates glycolysis at the step of glucose transport. These findings indicate the pivotal role of glucose metabolism in hypoxic cell death, and reveal a novel death-promoting effect of PI 3-kinase during hypoxia, despite this enzyme being considered to be a survival-promoting factor.

Acidosis↗
PubMed2001

Orphan G protein-coupled receptor, GPR41, induces apoptosis via a p53/Bax pathway during ischemic hypoxia and reoxygenation.

Orphan receptors that couple to G protein without known ligands are considered to relate directly to drug discovery. Here, we examine the expression of various orphan receptors in H9c2 cells during ischemic hypoxia and reoxygenation. Among orphan receptors examined, the level of G protein-coupled receptor 41 (GPR41) mRNA increases significantly, with a peak at 2 h after reoxygenation, and recovers to the control level by 3 h after reoxygenation. The level of glyceraldehyde-3-phosphate dehydrogenase mRNA used as an internal control remains almost constant. The levels of c-fos and c-jun mRNA increase significantly with ischemic hypoxia and reoxygenation. The transfection of GPR41 into H9c2 cells results in a significant decrease in cell number, with DNA fragmentation observed by in vitro and in situ assay. The amount of p53 protein increases significantly in the nuclei of cells expressing GPR41, accompanying an increase in the transcriptional activity of p53. Consistent with the activation of p53, the level of bax mRNA is significantly increased, which leads to an increase in Bax protein. Furthermore, the expression of a deletion mutant of a GPR41, which lacks the G protein binding site and shows an attenuation of intracellular phosphorylation signals to H9c2 cells, inhibits cell death and the increase in p53 protein within 24 h after reoxygenation. These observations demonstrate that GPR41 is a novel receptor that activates p53 leading to apoptosis during reoxygenation after ischemic hypoxia in H9c2 cells. We have designated GPR41 as the hypoxia-induced apoptosis receptor, HIA-R.

Animals↗
PubMed2001

Molecular cloning of rat transmembrane domain protein of 40 kDa regulated in adipocytes and its expression in H9c2 cells exposed to ischemic hypoxia and reoxygenation.

We clone a 1230 bp complementary DNA encoding rat transmembrane domain protein of 40 kDa regulated in adipocytes (TPRA40), an orphan receptor, by reverse transcription-polymerase chain reaction using H9c2 cells derived from embryonic rat heart. The deduced amino acid sequence of rat TPRA40 consists of 369 amino acids and has a longer carboxyl terminus than that of the mouse protein. The level of TPRA40 mRNA decreases significantly throughout ischemic hypoxia and reoxygenation.

Adipocytes↗
PubMed2001

Eicosapentaenoic acid (EPA) induces Ca(2+)-independent activation and translocation of endothelial nitric oxide synthase and endothelium-dependent vasorelaxation.

Eicosapentaenoic acid (EPA), but not its metabolites (docosapentaenoic acid and docosahexaenoic acid), stimulated nitric oxide (NO) production in endothelial cells in situ and induced endothelium-dependent relaxation of bovine coronary arteries precontracted with U46619. EPA induced a greater production of NO, but a much smaller and more transient elevation of intracellular Ca(2+) concentration ([Ca(2+)]i), than did a Ca(2+) ionophore (ionomycin). EPA stimulated NO production even in endothelial cells in situ loaded with a cytosolic Ca(2+) chelator 1,2-bis-o-aminophenoxythamine-N',N',N'-tetraacetic acid, which abolished the [Ca(2+)]i elevations induced by ATP and EPA. The EPA-induced vasorelaxation was inhibited by N(omega)-nitro-L-arginine methyl ester. Immunostaining analysis of endothelial NO synthase (eNOS) and caveolin-1 in cultured endothelial cells revealed eNOS to be colocalized with caveolin in the cell membrane at a resting state, while EPA stimulated the translocation of eNOS to the cytosol and its dissociation from caveolin, to an extent comparable to that of the eNOS translocation induced by a [Ca(2+)]i-elevating agonist (10 microM bradykinin). Thus, EPA induces Ca(2+)-independent activation and translocation of eNOS and endothelium-dependent vasorelaxation.

Animals↗
PubMed2001

Clinical approach to renal study incidental to 99mTc-MDP bone scintigraphy.

In order to investigate the feasibility of the assessment of renal function with 99mTc-MDP, we compared renographical images, renogram patterns and the glomerular filtration rate (GFR) obtained by means of a modified Gates' method and 200 MBq of 99mTc-MDP with those obtained by means of 99mTc-DTPA. Because 19 of 20 patients had malignant tumors in the genitourinary tract, there was no difference between the two tracers in identifying a parenchymal defect corresponding to renal cancer. Of eight patients with hydronephrosis, four had a defect or decreased uptake with a dilated pelvis, whereas the other four had marked radioisotope retention in the renal pelvis or the whole kidney on serial images. There was also no difference between the two tracers in identifying hydronephrosis. Of 38 paired renograms 35 showed the same renogram patterns with both tracers. Of three patients with different renogram patterns, two had hydronephrosis. In 20 patients including three patients with bone metastasis, total GFR and split GFR obtained with both tracers correlated with a correlation coefficient of r = 0.920 (p < 0.001) and r = 0.944 (p < 0.001), respectively. Excluding bone metastasis from the analysis, a linear-regression analysis showed excellent agreement between the two measurements with a correlation coefficient of r = 0.960 (p < 0.001) and r = 0.963 (p < 0.001), respectively. The linear regression equations were Y = 1.009X - 0.111 and Y = 1.034X - 0.714, respectively. In conclusion, 99mTc-MDP can be used as a supplement to evaluate renal function incidental to the survey of bone metastases in patients with malignant tumor.

Aged↗
PubMed2001

A matter of size: developmental control of organ size in plants.

The intrinsic size of plant organs is determined by developmental signals, yet the molecular and genetic mechanisms that control organ size are largely unknown. Ongoing functional analysis of Arabidopsis genes is defining important regulators involved in these mechanisms. Key features of this control are the coordinated activation of growth and cell division by growth regulators and the maintenance of meristematic competence by the ANT gene, which acts as an organ-size checkpoint. Alterations of genome size by polyploidization and endoreduplication can reset this checkpoint by ploidy-dependent, epigenetically regulated differential gene expression. In addition, the regulation of polarized growth and phytohormone signaling also affect final organ size. These findings reveal unique aspects of plant organ-size control that are distinct from animal organ-size control.

Arabidopsis↗
PubMed2001

Apoptosis of rat gastric mucosa and of primary cultures of gastric epithelial cells by indomethacin: role of inducible nitric oxide synthase and interleukin-8.

In order to gain insights into indomethacin-induced gastric injury, rats were fed with indomethacin (20 mg/kg), or alternatively, the primary cultures of rat gastric epithelial cells were cultured with different doses of indomethacin (1-1000 microM). Light microscopy, electron microscopy, fluorescence microscopy, TdT-mediated dUTP-biotin nick end labelling staining, ssDNA staining and DNA fragmentation assay were employed to evaluate the levels of gastric injury and apoptosis. Cells expressing inducible nitric oxide synthase (iNOS) and interleukin (IL)-8 were localized at the rat gastric mucosa by immunohistochemistry. Administration of indomethacin to rats caused apoptosis and injury of the gastric mucosal epithelial cells. Indomethacin also induced apoptosis of primary cultures of gastric epithelial cells in a dose-dependent manner. Cells expressing iNOS and IL-8 were detected at and around the sites of gastric injury in the indomethacin-fed rats, but not in the control rats. The induction of apoptosis by indomethacin in the primary cultures of gastric epithelial cells suggests that the direct apoptotic capacity of indomethacin. iNOS and IL-8 may be involved in this process.

Animals↗
PubMed2001

Non-invasive approach for diagnosing atrophic gastritis using the 13C-bicarbonate breath test.

The experiments presented here were done to evaluate whether the levels of CO2 in respiratory air during the 13C-bicarbonate breath test (13C-BBT) may be used as a marker of non-invasive diagnosis of the levels of atrophic gastritis. Twenty-eight patients with chronic gastritis and five healthy volunteers were enrolled in the study. Moreover, experimental gastritis was induced in rats by N-methy-N-nitro-N-nitrosoguanidine. In human, the levels of atrophic gastritis were evaluated from the vascular pattern of the gastric fornix. Total delta 13CO2 calculated from the 13C-BBT and the mucosal thickness ratio (MTR) were measured in rats with experimental gastritis. The levels of 13CO2 were significantly higher from patients with a vascular pattern at the fornix than in those without a vascular pattern (p<0.01). There was a good correlation between MTR and the levels of 13CO2, in rats with experimental gastritis (p<0.01). These findings indicate that the levels of 13CO2 during 13C-BBT reflect the levels of atrophic gastritis and show its clinical significance for non-invasive evaluation of atrophic gastritis. This has important clinical implications in selecting Helicobacter pylori-positive cases for therapy and follow-up.

Age Factors↗
PubMed2001

Pelvic arteriovenous malformation with iliac vein thrombosis. A case report.

BACKGROUND: Congenital arteriovenous malformations (AVMs) of the pelvis are relatively rare and are difficult to treat because of diffuse extension and the number of feeding vessels. METHODS: We describe a patient with a pelvic AVM with shunts who also developed iliac vein thrombosis. The AVM was diagnosed during evaluation of what had initially appeared to be a venous stasis ulcer. RESULTS: The ulcer was successfully treated by Palma s procedure, partial resection of the feeding vessels, and transcatheter arterial embolization. CONCLUSIONS: Coexistence of a pelvic AVM with an iliac vein thrombosis has not previously been reported.

Aged↗