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Biomedical subjects

H Miyoshi

Publications and source records attributed to H Miyoshi.

At least 145 records · Page 8Linked to original sources
PubMed1997

Glucocorticoids induce apoptosis in acute myeloid leukemia cell lines with A t(8;21) chromosome translocation.

The t(8;21) chromosome translocation frequently occurs in the AML, acute myeloid leukemia, M2 sub-type. This translocation juxtaposes the AML1 gene on chromosome 21 with the MTG8(ETO) gene on chromosome 8, resulting in the expression of the AML1-MTG8(ETO) fusion transcript. The fusion product is thought to play a critical role in the abnormal proliferation and differentiation of myeloid leukemia cells. We investigated the effects of various differentiation inducers of myeloid leukemia cells on the growth and differentiation of Kasumi-1 and SKNO-1 cells, AML cell lines with t(8;21). These cells resisted differentiation into mature granulocytes and macrophages in response to various inducers of myelomonocytic differentiation, such as dimethyl sulfoxide, retinoic acid, butyrate, 12-O-tetradecanoylphorbol-13-acetate (TPA) and 1alpha,25-dihydroxyvitamin D3. On the other hand, dexamethasone can induce apoptosis in these cells at low concentrations, whereas other myelomonocytic leukemia cell lines tested were resistant to glucocorticoid-induced apoptosis. The levels of glucocorticoid receptor gene expression were high in Kasumi-1 and SKNO-1 cells. Expression of the AML1-MTG8(ETO), bcl-2, and c-myc genes was unchanged following exposure to dexamethasone. Glucocorticoids might induce the apoptosis of some types of AML cells, just like that of some lymphoid leukemia cells.

Acute Disease↗
PubMed1997

Packed-bed type reactor to attain high density culture of hepatocytes for use as a bioartificial liver.

In an attempt to develop a bioartificial liver using cultured hepatocytes, we investigated the short-term and long-term viability and metabolic functions of hepatocytes cultured in a new type of packed-bed type reactor using reticulated polyvinyl formal (PVF) resin as a supporting material. Perfusion culture experiments using this reactor, as well as monolayer cultures using conventional collagen-coated Petri dishes as control experiments, were performed. It was found that the highest density of immobilized hepatocytes attained with PVF resin was on the order of 10(7) cells/cm3 PVF and that hepatocytes cultured in this type of module for up to a week showed a sufficient level of liver-specific metabolic functions, such as ammonium metabolism, urea-N synthesis, and albumin secretion, to be comparable to those in the monolayer culture. It is concluded that the packed-bed reactor system utilizing PVF resin is a promising means to develop a bioartificial organ using hepatocytes.

Alanine Transaminase↗
PubMed1997

Differences in brain metabolites between patients with autism and mental retardation as detected by in vivo localized proton magnetic resonance spectroscopy.

We performed volume-selective proton magnetic resonance spectroscopy (1H-MRS) of the brain with a 1.5 T magnet in 28 patients with autism, and compared the results with those from 28 age-matched patients with unclassified mental retardation and 25 age-matched healthy children. Peaks for N-acetylaspartate, choline and creatine, but not lactate, were observed in each group on 1H-MRS. The N-acetylaspartate/choline ratio was lower in patients with mental retardation than in patients with autism and controls (P = .05, respectively). However, there were no differences in the N-acetylaspartate/ choline ratios between patients with autism and controls, and the N-acetylaspartate/creatine and choline/creatine ratios did not differ among the three groups. These results suggest that N-acetylaspartate is decreased in patients with mental retardation and that a disorder or dysfunction of neurons in the brain exists. There also appear to be differences in the brain lesions or dysfunctions found in patients with autism and mental retardation.

Aspartic Acid↗
PubMed1997

Specific interaction of cytokinins and their analogs with rotenone-sensitive internal NADH dehydrogenase in potato tuber mitochondria.

Effects of cytokinins were studied on rotenone-sensitive NADH dehydrogenase in mitochondria from fresh potato tubers (Solanum tuberosum), in consideration of the operation of external and rotenone-insensitive internal NADH dehydrogenases that has not been fully accounted for in previous studies. In submitochondrial particles (smp), zeatin was only weakly active, and zeatin riboside (ZR) was inactive. Inhibition rates at 400 microns of isopentenyladenine (iP) and isopentenyladenosine (iPA) were 45% and 30%, respectively, and that of BA (BA) was 64%. In intact mitochondria, the inhibition by iP and BA significantly increased, I50 being 50 and 250 microM, respectively, but that by zeatin and iPA decreased. A structure-activity study showed that hydrophobic and steric factors are important for the activity. Cytokinins inhibited the electron flow via natural quinone more strongly than that via synthetic quinone. These results suggest that among the cytokinins the species that can regulate the electron transport is iP rather than its riboside or zeatin.

Adenine↗
PubMed1997

AML1a but not AML1b inhibits erythroid differentiation induced by sodium butyrate and enhances the megakaryocytic differentiation of K562 leukemia cells.

AML1 may play a role in growth and differentiation of cells along erythroid and/or megakaryocytic lineages, because a significant level of the AML1 gene is expressed in these cells. We overexpressed AML1a (without the transcription-activating domain) and AML1b (with the domain) proteins in K562 leukemia cells, which can be induced to differentiate into hemoglobin-producing cells and megakaryocytes. The AML1a-transfected K562 cells had a reduced capacity to differentiate in the presence of sodium n-butyrate but not in the presence of other inducers, such as hemin, 1-beta-D-arabinofuranosylcytosine, and herbimycin A. The AML1 antisense oligodeoxynucleotide but not the sense oligomer recovered its differentiation-inducing capacity in the presence of butyrate. On the other hand, AML1b conferred a similar differentiation-inducing capacity upon K562 cells transfected with vector alone. AML1a expression was associated with enhanced sensitivity to megakaryocytic differentiation induced by phorbol ester. These results provide evidence that AML1 proteins play a role in erythroid and megakaryocytic differentiation.

Antigens, CD↗
PubMed1997

[The studies of extracorporeal shock wave lithotripsy (ESWL) for pancreatic ductal stones].

30 patients with main pancreatic duct stones were treated by ESWL. In 18 of 22 patients who had not previously undergone endoscopic pancreatic sphincterotomy (EPST) or endoscopic sphincterotomy (EST), the stone fragments disappeared after ESWL. The fragments were removed endoscopically in the remaining 4 cases. Complete clearance was achieved in 8 cases with endoscopically unextractable stones by ESWL. After the ESWL procedure, absolute relief from pain was reported by in 19 of 22 patients with abdominal complaints. Serum amylase levels decreased significantly, and dilatation of the main pancreatic duct (MPD) was reduced. In the medium-term follow-up period, pancreatic exocrine function and endocrine function had a possibility to be preserved. One case of pancreatic cancer and one case of an intraductal papillary tumor of the pancreas were found, indicating that careful observation is necessary even after complete removal of pancreatic stones. In cases of Santorini duct dominant, multiple stones, or stricture of the MPD, ESWL should be combined with EPST and endoscopic stenting for preventing recurrence of acute pancreatitis and pancreatic stones. In conclusion, ESWL is the first choice of treatment for pancreatolithiasis and useful procedure and the limited complications.

Adult↗
PubMed1997

[Transverse relaxation time of metabolites by proton MRS: one of the parameters concerned with quantification].

We examined the transverse relaxation time of metabolites observed by proton MRS at 6 different points of TE(18, 30, 60, 90, 135, and 270ms). The double exponential curve was better fitted to the 6 points than the single exponential curve for calculating the T2 values of the three major metabolites. We considered that these metabolites would have a long T2 component and short T2 component, and the correct T2 value is difficult to obtain under the limitations of measurement time available in clinical applications.

Adult↗
PubMed1997

[Accuracy and clinical utility of quantitative proton magnetic resonance spectroscopy (MRS) on phantom and chronic cerebral ischemia].

We quantified the concentration of metabolites observed by proton MRS using the tissue water signal as an internal standard. A phantom containing known concentrations of NAA (10 mM) and Cr (5 mM) was used for the study of methodological accuracy. Clinical utility was evaluated by the measurement of patients with severe stenosis or obstruction of the unilateral internal carotid artery. The concentration of tissue water was compensated using a proton-density weighted image measured with a water bag attached to the head. The calculated concentrations of NAA and Cr in the phantom were 9.2 mM (SD: 1.2) and 5.6 mM (SD: 0.7), respectively. On the ischemic side of the brain, the concentrations of NAA and Cr were lower than on the opposite side, but the concentration of choline (Cho) was almost the same on the two sides. The NAA/Cr ratio showed no statistically significant differences between the two sides, because the concentration of Cr was shown to be decreased in the ischemic area. We consider that quantitative evaluation of proton MRS might reveal changes in single metabolites clearly, thereby facilitating understanding of the results of proton MRS.

Aspartic Acid↗
PubMed1997

Laparoscopic adrenalectomy in asymptomatic pheochromocytoma.

A patient with asymptomatic pheochromocytoma associated with catecholamine hypersecretion but no hypertension was treated by right laparoscopic adrenalectomy. The 63-year-old male patient was referred to us for treatment of an incidentaloma. The diameter of the adrenal tumor was 50 mm, and the peripheral blood nonrepinephrine level was 1.12 ng/ml (normal level, 0.4 ng/ml). Blood pressure was normal. A flexible electron laparoscope was used for open laparoscopy, and four trocars were inserted. The retroperitoneum was incised to the right of the inferior vena cava, and the tumor was excised. During the operation, blood pressure rose transiently, and a blocker and nitroglycerin were administered. The tumor bled extremely easily. The duration of surgery was 3 hours and 20 minutes, and blood loss was 210 ml. The excised tumor was 55 mm in diameter. The patients's postoperative course was uneventful. If the size of asymptomatic pheochromocytoma is not large, and blood pressure and cardiac function are stable, laparoscopic adrenalectomy is indicated for this type of tumor as long as it is performed by experienced surgeons.

Adrenal Gland Neoplasms↗
PubMed1997

Effect of K+ channel openers on K+ channel in cultured human dermal papilla cells.

Minoxidil sulfate and pinacidil, well-known activators of the ATP-sensitive K+ (KATP) channel, induce hair growth in clinical studies. The opening of K+ channels is thought to be an important mechanism in the regulation of hair follicles. In the present study, we used the patch clamp technique to characterize the K+ channels and tested the effect of K+ channel openers on K+ channels in cultured human dermal papilla cells. In dermal papilla cells, the Ca(2+)-activated K+ (KCa) channel with large conductance (179.3 +/- 13.1 pS in symmetrical 150 mM K+ solutions, n = 9) was dominant and we could not observe KATP channels in cell-attached and inside-out patches. In addition, minoxidil and pinacidil failed to activate KATP or KCa channels. In inside-out membrane patches, the channel was blocked by 10 mM tetraethylammonium ion, 2 mM 4-aminopyridine to the cytosolic face of the membrane or by lowering Ca2+ using 10 mM EGTA, but not by glibenclamide. In the cell-attached patch configurations, extracellular application of 1 mM sodium nitroprusside, a nitrovasodilator, activated the KCa channel. Methylene blue (2 mM) inhibited channel activation by sodium nitroprusside. Extracellular application of 20 mM dibutyryl cGMP activated the KCa channel, suggesting that channel activation is mediated by cGMP. Nitrovasodilators, which have no effect on hair growth, now appear to activate KCa channels in dermal papilla cells. These results suggest that increased K+ permeability itself in dermal papilla cells may not be sufficient for promotion of hair growth.

Cells, Cultured↗
PubMed1997

Expression of Xenopus laevis translation initiation factor 4E (eIF-4E) by baculovirus-insect cell system.

A gene encoding Xenopus laevis eIF-4E was cloned into a transfer vector, and its gene expression was attempted in cells of E. coli, yeast and insect. Effective expression of the active eIF-4E was achieved in the soluble fraction of the insect cell Sf9, which was infected with the recombinant baculovirus. Overexpression of the eIF-4E protein caused remarkable change in the shape of the cells.

Animals↗
PubMed1996

Probing substrate binding site of the Escherichia coli quinol oxidases using synthetic ubiquinol analogues.

Substrate binding sites of the Escherichia coli bo- and bd-type quinol oxidases were probed with systematically synthesized ubiquinol analogues. The apparent Km values of ubiquinol-2 derivatives to the bo-type enzyme were much lower than that of the corresponding 6-n-decyl derivatives. The isoprenoid structure is less hydrophobic than the saturated n-alkyl group with the same carbon number; therefore, the native isoprenoid side chain appears to play a specific role in quinol binding besides simply increasing hydrophobicity of the molecule. The Vmax values of 2-methoxy-3-ethoxy analogues were greater than that of 2-ethoxy-3-methoxy analogues irrespective of the side chain structure. This result indicates not only that a methoxy group in the 2-position is recognized more strictly than the 3-position by the binding site but also that the side chain structure does not affect binding of the quinol ring moiety. Systematic analysis of the electron-donating activities of the analogues with different substituents in the 5-position revealed that the 5-methyl group is important for the activity. In the parallel studies with the bd-type enzyme, we obtained similar observations except that almost all quinol analogues, but not ubiquinol-1, elicited a remarkable substrate inhibition at higher concentrations. These results indicate that the two structurally unrelated terminal oxidases share common structural properties for the quinol-oxidation site.

Electrons↗
PubMed1996

Structural factors of rotenone required for inhibition of various NADH-ubiquinone oxidoreductases.

We performed a structure-activity study of a series of synthetic rotenone analogues to elucidate the structural factors of rotenone required for inhibition and to probe the structural properties of the rotenone binding site of various NADH-ubiquinone oxidoreductases (NDH), including both proton-pumping (NDH-1) and non-proton-pumping (NDH-2) enzymes, from bovine heart mitochondria, potato tuber (Solanum tuberosum L.) mitochondria and Escherichia coli (GR 19N) plasma membranes. Using a benzyloxy group as a substitute for the E-ring moiety of natural rotenone, systematically selected structural modifications of the A-ring became feasible. The inhibitory potency of bovine NDH markedly varied depending upon structural modifications of the A-ring. The native chemical structure (2,3-dimethoxy substitution) appeared to be the most favorable for the activity. The spatial location of the hydrogen-bond acceptable methoxy oxygens may be important for tight fitting into the binding site. However, replacing one of the two methoxy groups by an ethoxy group almost completely retained the activity, indicating that the binding environment of the A-ring moiety is spacious enough to accommodate a substituent larger than the methoxy group. The manner of action of the derivative lacking the 12-C = O group in the C-ring differed from that of natural rotenone, indicating that this functional group is important for supporting the inhibitory action of natural rotenone itself. Regarding potato tube and E. coli NDH-1, the sensitivity of the two enzymes to the inhibition by rotenone analogues was much lower than that of the bovine enzyme. The 2,3-dimethoxy substitution was the most favorable for the activity with potato NDH-1, whereas this substitution pattern was not necessarily the best with E. coli NDH-1. A rule governing inhibitory potency depending upon structural modifications was ambiguous for the two enzymes because of a small variation in the inhibitory potencies. These findings indicated that the local binding environment of the A-ring moiety of rotenone in bovine NDH is specific and differs considerably from that in potato and E. coli NDH-1.

Animals↗
PubMed1996

Inhibitor probes of the quinone binding sites of mammalian complex II and Escherichia coli fumarate reductase.

The structural and catalytic properties of beef heart succinate dehydrogenase (succinate-ubiquinone oxidoreductase, complex II) and Escherichia coli fumarate reductase are remarkably similar. One exception is that whereas electron exchange between the mammalian enzyme and its quinone pool is inhibited by thenoyltrifluoroacetone and carboxanilides, the enzyme from E. coli is not sensitive to these inhibitors. The lack of good inhibitors has seriously hampered the elucidation of the mechanism of quinone oxidation/reduction in the E. coli enzyme. We have previously reported (Tan, A. K., Ramsay, R. R., Singer, T. P., and Miyoshi, H. (1993) J. Biol. Chem. 268, 19328-19333) that 2-alkyl-4,6-dinitrophenols inhibit mammalian complexes I, II, and III, but with different potencies and kinetic characteristics. Based on these studies we have selected a series of 2-alkyl-4,6-dinitrophenols which proved to be very effective noncompetitive inhibitors of mammalian complex II, particularly when acting in the direction of quinone reduction, the physiological event. These compounds turned out to be even more potent inhibitors of E. coli fumarate reductase, particularly when acting in the direction of quinol oxidation, again, the physiological event. Kinetic analysis revealed that with both enzymes 2 inhibitor binding sites seem to be involved in the oxidation of succinate by quinone, but one seems to be functioning when fumarate is reduced by external quinol. Since the E. coli enzyme can be modified by site-directed mutagenesis, these studies were extended to four mutants of fumarate reductase, impaired by single amino acid substitutions at either of the putative quinone binding sites (QA or QB) of the enzyme. The results were analyzed in terms of the model of these dual sites of quinone binding in fumarate reductase, as well as the nature of the substituent in the 2-position of the dinitrophenol inhibitors.

Animals↗
PubMed1996

Estrogen inhibits endothelin-1 production and c-fos gene expression in rat aorta.

In order to clarify the mechanism underlying the preventive effect of estrogen on atherogenesis, we investigated the role of estrogen in the regulation of endothelin-1 (ET-1) production and c-fos mRNA expression, which may contribute to atherogenesis. Plasma ET-1 concentration in ovariectomized rats (OVX) was twice as high as that in sham-operated female rats (Sham). Estradiol replacement in OVX rats (OVX + E) decreased plasma ET-1 to the level in Sham (Sham, 0.68 +/- 0.14; OVX, 1.32 +/- 0.14; OVX + E, 0.85 +/- 0.12 pg/ml). Metabolic clearance rate of ET-1 was similar in these three groups of rats, suggesting that the difference in plasma ET-1 was due to production rather than degradation. Measurement of immunoreactive ET-1 in tissue extract and immunohistochemical examination showed that expression of ET-1 in the aortic smooth muscle cells of OVX was increased. The expression of c-fos mRNA in the aorta was also increased in OVX compared with Sham and OVX + E. Intravenous infusion of ET-1 to Sham induced c-fos expression in the aorta, suggesting the contribution of ET-1 to c-fos expression. Tissue culture study revealed that DNA synthesis was increased in the aorta and femoral artery of OVX. These results suggest that inhibition of ET-1 and c-fos expression is involved in the anti-atherogenic action of estrogen.

Animals↗