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Biomedical subjects

R Maeba

Publications and source records attributed to R Maeba.

8 recordsLinked to original sources
PubMed2004

A novel antioxidant action of ethanolamine plasmalogens in lowering the oxidizability of membranes.

We have demonstrated a novel antioxidant action of ethanolamine plasmalogens both in protecting cholesterol from oxidation by free radicals and in lowering the oxidizability of membranes, along with the action of scavenging radicals, by the oxygen-uptake method using large unilamellar vesicles and the water-soluble azo-radical initiator, AAPH [2,2'-azobis-(2-amidino-propane) dihydrochloride].

Antioxidants↗
PubMed1995

Oxidized low-density lipoprotein induces the production of superoxide by neutrophils.

Exposure of guinea pig peritoneal neutrophils to ox-LDL led to the production of superoxide, which was measured by the formation of superoxide-dependent chemiluminescence. The cells exposed to unoxidized LDL, e.g. native LDL, acetyl-LDL, and self-aggregates of LDL showed no production of superoxide. The superoxide production was correlated with the levels of oxidative modification of LDL and reached a maximum between 10 and 30 min during incubation, but preincubating the cells with cytochalasin B decreased the superoxide production. These findings indicate that neutrophils rapidly take up ox-LDL by phagocytosis and generate superoxide which may cause superoxide-mediated lipid peroxidation in vivo.

Animals↗
PubMed1995

Lipid peroxidation and ceroid accumulation in macrophages cultured with oxidized low density lipoprotein.

When mouse peritoneal macrophages were cultured with oxidized human low density lipoprotein (ox-LDL), storage of ceroid-like pigments was observed within the cells by light and fluorescent microscopy, and fluorescence spectrophotometry. The fluorescent products exhibit the characteristics of Schiff base structures, having a fluorescence maximum of 430 nm and an excitation maximum of 355 nm, which has been generally accepted with fluorescent lipid peroxidation products. Similar fluorescent products were isolated from the atherosclerotic lesions of the aged human artery. Ox-LDL was also intraperitoneally injected into guinea pigs to study an early stage of ceroid accumulation in macrophages. An early event in guinea pigs was the appearance of neutrophils. The findings from the model systems suggest that the ox-LDL in the artery wall is probable chemotactic for neutrophils as well as monocytes. We propose the hypothesis that the production of superoxide by neutrophils causes further lipid peroxidation of native LDL and then produces large amounts of oxidatively modified LDL which is the souse of ceroid pigment accumulated within the foam cells in human atherosclerotic lesions.

Aged↗
PubMed1994

Conformational changes in oxidized LDL recognized by mouse peritoneal macrophages.

Mouse peritoneal macrophages have been considered to recognize and take up oxidized LDL by a scavenger receptor. However, it is still unknown what conformational changes in oxidized LDL contribute to recognition by the macrophage scavenger receptor. In the present study, it was shown that the amount of oxidized LDL taken up by macrophages correlated well with the fluorescence intensity formed in oxidized LDL. The autofluorescent products generated in oxidized LDL were characterized by Ex:365 nm Em:430 nm, and the intensity of the fluorescence was reduced at base pH, and restored by adjusting the pH to neutral. The characteristics of the fluorescent products indicate that a Schiff base structure was formed in oxidized LDL. Oxidized LDLs were fractionated into native size and aggregated large particles with HPLC by monitoring fluorescence. It was demonstrated that macrophages ingest selectively or preferentially aggregated oxidized LDL, but not native size oxidized LDL. The incorporation of aggregated oxidized LDL was remarkably suppressed by heparin and cytochalasin B. These results suggest that mouse peritoneal macrophages recognize the conformational changes in oxidized LDL related to the formation of a Schiff base structure with increasing autofluorescence, and ingest selectively aggregated large particles in oxidized LDL in a phagocytic process.

Animals↗
PubMed1991

Purine and pyrimidine compounds in murine peritoneal macrophages cultured in vitro.

Extracts of murine peritoneal macrophages were analysed by ion-pair reversed-phase high-performance liquid chromatography during incubation at 37 degrees C in vitro. Four-step gradient elution was applied to an ODS column (250 x 4.6 mm I.D.) at a flow-rate of 1.3 ml/min, allowing the separation of hypoxanthine, inosine, guanosine, adenosine, IMP, CDP, AMP, GDP, UDP, ADP, CTP, GTP, UTP and ATP within 50 min. Samples of 0.4 . 10(6)-0.5 . 10(6) cells were washed twice with RPMI 1640 medium and extracted with perchloric acid. Nucleotide concentrations of murine peritoneal macrophages did not change during incubation for 4 days in vitro.

Animals↗
PubMed1990

Accumulation of ceroid-like pigments in macrophages cultured with phosphatidylcholine liposomes in vitro.

When mouse peritoneal macrophages as well as P388D1 cells, an established macrophage-like cell line, were cultured with liposomes composed of rat liver phosphatidylcholine and phosphatidylserine, storage of fluorescent products, ceroid-like pigments, within those cells was observed with light and fluorescence microscopy, and fluorescence spectrophotometry. The amounts of thiobarbituric acid-reactive substances and fluorescent products in macrophages were increased gradually to reach a maximal level to between 6 and 8 days of culture. The involvement of peroxidation of liposomal lipids in the formation of the pigments was further suggested by the 6 days that incorporation of alpha-tocopherol into liposomes decreased the storage of the pigments. No appreciable formation of the pigments was observed in macrophages cultured with liposomes containing dipalmitoylphosphatidylcholine instead of rat liver phosphatidylcholine. The fluorescent products formed in cultured cells were found in lipid-soluble and -insoluble fractions. Lipid-insoluble fluorescent products had an excitation maximum at 360 nm and a fluorescence maximum at 430 nm in SDS-aqueous solution (pH 7.4) and the intensity of the fluorescence was quenched at base pH, but it was not changed in acidic media. These findings indicate that the macrophages can store Schiff base fluorescent substances formed by the reaction between peroxidation products of exogenous lipids and amino compounds in the cells, under some pathological conditions.

Animals↗
PubMed1989

Lipid peroxidation and storage of fluorescent products by macrophages in vitro as a model of ceroid-like pigment formation.

Storage of fluorescent products, ceroid-like pigments was observed in P388D1 cells, an established macrophage-like cell line, when the cells were cultured in the presence of rat liver phosphatidylcholine liposomes containing polyunsaturated fatty acids. Some fluorescent products accumulated in the cells were extractable in organic solvents, ethanol/ether (3:1, v/v), while others were insoluble in organic solvents, but soluble in detergent. The fluorescent products dissolved in organic solvents or in detergent had a fluorescence maximum at 430 nm when excited at 360 nm. The formation of the ceroid-like pigments was inhibited, at least in part, by antioxidants, such as alpha-tocopherol and butylated hydroxytoluene (BHT). The fluorescence intensity of the pigments was quenched in alkaline media and restored by adjustment of pH to neutrality. These findings indicate that liposome uptake by macrophages causes the formation of ceroid-like pigments, and that the fluorescent chromophores of the pigments are Schiff base structures derived from the reaction of lipid peroxides from the exogenous phospholipids and subcellular amino compounds.

Animals↗