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Biomedical subjects

M Miyahara

Publications and source records attributed to M Miyahara.

At least 145 records · Page 8Linked to original sources
PubMed1988

Charge-dependent regulation of NADPH oxidase activities in intact and subcellular systems of polymorphonuclear leukocytes.

It has been reported that respiratory bursts with N-formylmethionylleucylphenylalanine, A23187, phorbol ester and fatty acids are switched off and on by modulating the net charges of plasma membranes in guinea-pig neutrophils (Miyahara, M. et al. (1987), Biochim. Biophys. Acta, 929, 253-262). In the present study, this was further extended in cells treated with protein kinase C inhibitors which completely suppressed the phorbol ester-dependent respiratory burst. This suggested that the initiation of the respiratory burst, which is generally accepted as linked to protein kinase C activation, might also be implicated in the net charge changes of plasma membranes. The above results were also supported by data obtained with a cell-free system reconstituted with plasma membranes and cytosolic fractions from unstimulated neutrophils, guanosine 5'-[gamma-thio]triphosphate and NADPH. Arachidonate stimulated NADPH oxidase activity accompanied by a marked phosphorylation of membrane proteins. The phosphorylation was sensitive to H-7, but it did not appear to be essential for the respiratory burst, because the oxidase activation was insensitive to H-7. Pretreating the plasma membranes with positively charged cetylamine inhibited the oxidase activation by arachidonate. These results suggest that a charge-dependent process, which does not use protein kinase C, may play an important role in the reaction leading to NADPH oxidase activation, and this may be related to the interaction of plasma membranes with the cytosolic activation factor.

Animals↗
PubMed1988

Purification and characterization of a lipocortin-like 33 kDa protein from guinea pig neutrophils.

A lipocortin-like, phospholipase A2 inhibitory 33 kDa protein was purified from guinea pig neutrophils. From amino acid composition and sequence data, this protein was found to have a high degree of homology to human lipocortin I. This protein inhibited porcine pancreatic phospholipase A2 activity in the presence of [3H]oleic acid-labeled Escherichia coli membranes as substrate. Maximal inhibition amounted to 65% whereas 50% inhibition occurred at 83.5 nM. This protein showed F-actin-binding ability in a Ca2+-dependent manner.

Actins↗
PubMed1988

Giant hepatic angiomyolipoma simulating focal nodular hyperplasia.

A case of hepatic angiomyolipoma occurring in a 41-year-old woman, the eighteenth case in literature, is reported herein. The radiographic imagings of the tumor simulated those of focal nodular hyperplasia; namely, the tumor was hyperechoic on ultrasound, hypodense on computed tomography, hypervascular on angiography, and exhibited an uptake of technetium (Tc)-99m phytate. The diagnosis was established after successful removal of the huge tumor from the right hepatic lobe. Histologically, the tumor was angiomyolipoma which was made up of three components, blood vessels, smooth muscle and fatty tissue. Furthermore, extramedullary hematopoiesis, which is usually seen in this tumor was confirmed. The differentiation of hepatic angiomyolipoma from FNH is also discussed.

Adult↗
PubMed1988

Widespread occurrence of the restriction endonuclease YenI, an isoschizomer of PstI, in Yersinia enterocolitica serotype O8.

The cold-active restriction endonuclease YenI, an isoschizomer of PstI, was found in 12 of 14 Yersinia enterocolitica serotype O8 strains of different origins, but not in other serotypes of Y. enterocolitica, Yersinia pseudotuberculosis, or Yersinia pestis. In spite of the limited number of strains tested, the result suggests that the detection of YenI endonuclease or the gene might result in more rapid determination of the prominently pathogenic serotype of Y. enterocolitica.

Animals↗
PubMed1988

Lipocortin-like 33 kDa protein of guinea pig neutrophil. Its distribution and stimulation-dependent translocation detected by monoclonal anti-33 kDa protein antibody.

33 kDa protein of neutrophil is a lipocortin-like protein, as proposed from its biochemical properties, amino acid composition, and the homology of its amino acid sequence to human lipocortin I. The localization and translocation of 33 kDa protein (p33) in blood cells of guinea pig were studied by immunoblotting (Western blotting) and immunocytochemical fluorescence methods using polyclonal and monoclonal mouse anti-p33 antibodies. The protein was determined to be present only in the cytoplasm of neutrophils, but not in cells such as the monocyte, lymphocyte, platelet, and other bone marrow cells. The translocation of the protein from cytoplasm to cell membrane was coupled with the increase in intracellular calcium ion and in superoxide generation induced by a chemotactic factor. These findings suggest that p33 may have an important role not only in the regulatory mechanism of phospholipase A2 (PLA2) activity but also in other transmembrane signaling.

Animals↗
PubMed1987

Charge-dependent regulation of NADPH oxidase activity in guinea-pig polymorphonuclear leukocytes.

The mechanism of respiratory burst was studied by modulating membrane surfaces with lipophilic ions in guinea-pig polymorphonuclear leukocytes and their subcellular membranes. Positively charged alkylamines in concentration ranges of 0.5 to 15 microM (ED50 values) inhibited the O2- generation with phorbol 12-myristate 13-acetate, N-formylmethionylleucylphenylalanine, A23187, myristate and arachidonate in intact cells, and the inhibition was relieved by negatively charged agents. A similar molecular size of alkylalcohols had no effects. A similar charge-dependent O2- generation was also observed with fatty acids in subcellular membrane fractions prepared from unstimulated control cells, and this was insensitive to H-7 and W-7. These results suggest that triggering of NADPH oxidase activation involves a reaction(s) that is regulated by membrane charges.

Amines↗
PubMed1987

Neutrophil specific 33 kDa protein: its Ca2+- and phospholipid-dependent intracellular translocation.

A 33 kDa protein from neutrophils has been shown to associate reversibly with phosphatidylserine containing liposomes in a Ca2+-dependent manner. The protein was purified from guinea pig neutrophils. Immunoblotting and cytochemical studies with polyclonal and monoclonal antibodies to the protein revealed that the protein is commonly distributed in neutrophil cytoplasm of different animal species. The protein was translocated to the plasma membrane by treatment with stimuli. Thus the 33 kDa protein is neutrophil specific and may be involved in transmembrane signaling.

Animals↗
PubMed1986

Calcium-dependent association of 33 kDa protein in polymorphonuclear leukocytes with phospholipid liposomes containing phosphatidylserine or cardiolipin.

The effects of lipids and Ca2+ on the association of cytoplasmic proteins of polymorphonuclear leukocytes (PMN) with dipalmitoylphosphatidylcholine liposomes containing phosphatidylserine (PS) or cardiolipin (CL) were examined. In the presence of Ca2+, a cytoplasmic protein (33 kDa) of PMN was found to be a major component that bound to these liposome membranes. The maximum association with the liposomes was obtained at the molecular concentration of 25% CL and 50% PS; the required concentrations of Ca2+ were in the nanomolar and micromolar ranges for CL and PS, respectively. The liposome-associated 33 kDa protein was released from liposomes by an addition of EGTA. These results suggest that the 33 kDa protein reversibly associates to the cytoplasmic surface of PMN plasma membranes where PS localizes depending on a small change in intracellular concentration of free Ca2+.

Animals↗
PubMed1986

Metabolic response of polymorphonuclear leukocyte to arachidonic and linoleic acids.

Various stimuli act on polymorphonuclear leukocytes (PMN), activating membrane-bound phospholipase A2 and C, and diglyceride lipase and then liberating unsaturated fatty acids (USFAs). These liberated USFAs are immediately metabolized through various metabolic pathways such as cyclooxygenase, lipoxygenase, phosphatidylinositol metabolism etc. It is possible that the metabolic intermediates of these pathways reveal various physiological actions. This work was undertaken to clarify whether stimuli on PMN depend on these USFAs themselves or on their oxidation products. The following results were obtained: 1. USFAs such as arachidonate and linoleate stimulate PMN, accelerating superoxide (O2) generation, depolarization of membrane potential and increase in [Ca2+]i. 2. Oxidation products of USFAs have no stimulative effect on PMN. The decrease in the stimulative effect of these USFAs following their oxidation is proportional to the quantitative decrease in non-oxidized linoleate. 3. USFAs accelerate membrane permeability of Ca2+, and their oxidation products enhance non-specific membrane permeability in proportion to the formation of monohydroxy compound. These results suggest that stimulative effects of USFAs on PMN do not depend on their oxidation products but on unoxidized fatty acids. Furthermore, among the oxidation products of the USFAs, monohydroxy compound acts as a strong perturber of membrane and accelerates membrane permeability.

Arachidonic Acid↗
PubMed1985

Strand specific transcription of satellite DNA I in rat ascites hepatoma cells.

Rat satellite DNA I was highly expressed in a rat ascites hepatoma cell line, AH60C. The transcripts were found predominantly in the non-polyadenylated fraction of the nuclear RNA. RNA dot blot assay using strand specific probes revealed a strand-selective transcription of the sequence. The structures of cDNA clones isolated on the basis of their cross-hybridization to satellite DNA I were mainly composed of a tandemly repeated array of this sequence.

Animals↗
PubMed1985

Radiation-induced damage to mitochondrial D-beta-hydroxybutyrate dehydrogenase and lipid peroxidation.

Radiation-induced damage to the reconstituted system of membrane-bound enzyme, D-beta-hydroxybutyrate dehydrogenase obtained from rat liver mitochondria, was investigated in relation to the lipid peroxidation of membranes. The activity of D-beta-hydroxybutyrate dehydrogenase in fresh mitochondria was very low in general and was not affected by irradiation because of little incorporation of substrates into mitochondria. However, the enzyme activity in one-day-aged mitochondria or submitochondrial particles was five times higher than that of fresh mitochondria and decreased with increasing radiation dose accompanying the increase in peroxidation of membrane lipids. The activity of D-beta-hydroxybutyrate dehydrogenase in the reconstituted system of the purified enzyme with irradiated liver microsomes or irradiated liposomes was decreased considerably in comparison with either unirradiated control or irradiated enzyme. Therefore, the radiation-induced decrease in the enzyme activity was thought to be caused mainly by peroxidation of membrane lipids and not to be due to direct damage by radiation to the enzyme molecule itself. Irradiation of microsomes, a component of the reconstituted system, caused decreases in phosphatidylcholine and phosphatidylethanolamine content and an increase in lysophosphatidylcholine content. In addition, arachidonic acid contents in phosphatidylcholine, phosphatidylinositol and phosphatidylethanolamine were also markedly decreased with increasing radiation dose. These results are discussed in terms of a mechanism involving radiation-induced damage to membrane function and structures.

3-Hydroxybutyric Acid↗
PubMed1985

Ca2+ translocation across liposomal membranes enhanced by unsaturated long-chain fatty acids.

The putative ionophoretic action of phosphatidic acid or arachidonic acid metabolites for Ca2+ has offered an attractive explanation for stimulation-coupled mobilization of cytoplasmic Ca2+. We have examined the effects of Ca2+ ionophore and long-chain unsaturated fatty acids on the translocation of Ca2+ across the liposomal membrane by using Quin II-entrapped liposomes, a sensitive assay system for ionophoresis of Ca2+. A23187 increased Quin II fluorescence intensity corresponding to the translocation of Ca2+ into liposomes. Similar translocation was observed with unsaturated long-chain fatty acids but not with saturated fatty acids. Thus, when phospholipases of cell membrane are activated by certain stimuli, unsaturated long-chain fatty acids are liberated and might mediate the mobilization of cytoplasmic Ca2+.

Arachidonic Acids↗
PubMed1985

Continuous fluorometric assay of Ca2+ transport by liposomes with Quin 2 entrapped: effect of phospholipase A2 and unsaturated long-chain fatty acids.

The amount of free calcium in the cytoplasm is important in stimulation coupled with a number of cellular functions. The putative ionophoretic action of membrane lipid metabolites on Ca2+ offers convenient explanation of the stimulation-coupled mobilization of cytoplasmic Ca2+. To analyze the ionophoretic action of the lipid metabolites, we devised a sensitive method to study Ca2+ transport that uses liposome-entrapped Quin 2. A calcium ionophore, A23187, increased the fluorescence intensity of the Ca2+-Quin 2 complex as a function of Ca2+ transport into liposomes. A similar Ca2+ flux into the liposomes was induced by phospholipase A2 (PLA2) and by various long-chain fatty acids in liposomes that consist of phospholipids containing unsaturated fatty acids. The potencies of the fatty acids for Ca2+ transport is inversely correlated with their melting points. The oxidized products of the unsaturated fatty acids increased the Ca2+ and nonspecific permeability of the biological membranes. These results suggest that stimulation-coupled PLA2 activation might mediates the mobilization of cytoplasmic Ca2+.

Aminoquinolines↗