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N Ueta

Publications and source records attributed to N Ueta.

At least 37 records · Page 2Linked to original sources
PubMed1990

Phosphatidylcholine metabolism for energy production in sea urchin spermatozoa.

Sea urchin spermatozoa use endogenous phosphatidylcholine (PC) to produce energy for swimming. The catabolism of PC was studied in Hemicentrotus pulcherrimus spermatozoa. Following incubation in sea water, the content of PC decreased and that of choline increased gradually, whereas phosphocholine maintained a constant level. Measurement of the radioactivity in metabolites converted from 1-palmitoyl-2-[1-14C]linoleoyl-PC, [choline-methyl-14C]dipalmitoyl-PC and 1-[1-14C]palmitoyl-lysophosphatidylcholine (LysoPC) showed that the major degradative pathway is PC----LysoPC----glycerophosphocholine----choline. 1-Palmitoyl-2-[1-14C]linoleoyl-PC and [1-14C]oleic acid were oxidized to 14CO2 in a cell-free system of spermatozoa. Sea urchin spermatozoa thus appear to quite likely obtain energy through the oxidation of fatty acid(s) from PC.

Animals↗
PubMed1990

The influence of an egg-associated peptide on energy metabolism in sea-urchin spermatozoa: the peptide stimulates preferential hydrolysis of phosphatidylcholine and oxidation of fatty acid.

A study was made of the effects of a sperm-activating peptide (SAP-I: Gly-Phe-Asp-Leu-Asn-Gly-Gly-Gly-Val-Gly) on energy metabolism in spermatozoa of the sea urchin, Hemicentrotus pulcherrimus. The swimming activity and respiratory rate in slightly acidic seawater (pH 6.6) have been shown to be somewhat less than in normal seawater (pH 8.2). Little change occurred in sperm lipid levels during incubation in seawater at pH 6.6. The addition of SAP-I to seawater at pH 6.6 enhanced the consumption of endogenous phosphatidylcholine (PC), with no change in the levels of other lipids. SAP-I also caused increase in 14CO2 production from exogenous [1-14C]oleic acid following incubation of spermatozoa at pH 6.6. However, the stimulated levels of PC consumption and fatty acid oxidation with SAP-I at pH 6.6 did not exceed those at pH 8.2. At pH 8.2, SAP-I had no effect on PC metabolism. Activities of phospholipase A2 and fatty acid oxidation were markedly influenced by pH and increased at pH exceeding 7. SAP-I is thus concluded to stimulate sea-urchin sperm energy metabolism which depends on the oxidation of endogenous PC. It follows from these results that PC metabolism is activated following increase in the intracellular pH of spermatozoa.

Amino Acid Sequence↗
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↗
PubMed1990

Changes in cerebral free fatty acids and triacylglycerols in focal cerebral ischemia.

1. Focal cerebral ischemia was induced in anesthetized rats by occluding the stem of the proximal middle cerebral artery. 2. The levels of free fatty acids, such as stearic and arachidonic acids, in the ischemic cerebral cortex increased progressively until 60 min after occlusion, but thereafter they decreased rapidly. 3. In contrast to the time-dependent changes in free fatty acids, the levels of triacylglycerol (TAG) in the ischemic cerebral cortex continued to increase for 120 min after occlusion. Increases in TAG-palmitate, -stearate and -arachidonate accounted for the increase in the triacylglycerol level. 4. The pattern of the lipid changes in focal cerebral ischemia differs from those reported in bilateral diffuse cerebral ischemia induced by arterial occlusion or in decapitation ischemia.

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↗
PubMed1989

Mediation of cyclic adenosine 3',5'-monophosphate in 1-methyladenine production by starfish ovarian follicle cells.

Resumption of meiosis in starfish oocytes is induced by 1-methyladenine (1-MeAde) produced by ovarian follicle cells under the influence of a gonad-stimulating substance (GSS). It has also been reported that concanavalin A (Con A) and two serine proteolytic enzymes (trypsin and Pronase) can stimulate 1-MeAde production. This study was undertaken to determine if 1-MeAde production induced by these compounds is mediated through elevation of cAMP in starfish (Asterina pectinifera) follicle cells. GSS at a concentration of 0.1 mg/ml significantly stimulated 1-MeAde accumulation in extracellular medium after 1-2 hr of follicle cell incubations. GSS also caused a four- to fivefold increase in intracellular levels of cAMP. The continuous presence of GSS was required for the maintenance of elevated levels of cAMP and 1-MeAde. Basal levels of intracellular cGMP were only about 20% of those of cAMP and were not influenced by treatment with GSS. At 1 mM, 3-isobutyl-1-methylxanthine (IBMX), a potent phosphodiesterase inhibitor, stimulated both 1-MeAde and cAMP production in a concentration-dependent manner. Con A and two serine proteases also raised both cAMP and 1-MeAde production. Con A-induced (1.0 mg/ml) increases in cAMP and 1-MeAde were greater than the response to GSS (0.1 mg/ml) and were completely suppressed by treatment with alpha-methyl-D-mannoside (10 mM), a competitive inhibitor of Con A. These results strongly suggest that cAMP is a second messenger in the production of 1-MeAde by starfish ovarian follicle cells.

Adenine↗
PubMed1989

Fatty chain composition of phospholipids in sea urchin spermatozoa.

1. An analysis was made of lipids extracted from the spermatozoa of the sea urchins, Hemicentrotus pulcherrimus and Anthocidaris crassispina. 2. Nearly all the lipids from both species consisted of phospholipids (about 80%) and cholesterol (about 14%). Triglyceride and cholesterol ester were present in trace amounts. 3. The fatty acid composition of each phospholipid was determined by gas-liquid chromatography. In both species, the fatty acid consisting of phosphatidylethanolamine was of the unsaturated type for the most part, while cardiolipin was comprised to a considerable degree of saturated fatty acids. In phosphatidylcholine and phosphatidylserine from H. pulcherrimus sperm, unsaturated fatty acid content was somewhat higher than that in phospholipids from A. crassispina sperm.

Animals↗
PubMed1989

Accumulation of ceramide in ischemic human brain of an acute case of cerebral occlusion.

An increase of ceramide, which is the major component of sphingolipids, was found in the ischemic human brain of an acute case of internal carotid artery occlusion. Amide-linked fatty acids in the ceramide isolated from the ischemic human brain were mostly non-hydroxy fatty acids, such as stearic acid (66.9%) and palmitic acid (20.2%). Other long-chain fatty acids, C24:0 and C21:1, were rare components in the ceramide. The ceramide contained C-20 sphingosine, and the ratio of C-20 to C-18 was 0.13. These findings indicate that an ischemic insult accelerates the degradation of gangliosides and causes an accumulation of ceramide in the ischemic human brain.

Aged↗
PubMed1988

Energy metabolism of sea urchin spermatozoa, with phosphatidylcholine as the preferred substrate.

Phosphatidylcholine content in the spermatozoa of the sea urchin, Hemicentrotus pulcherrimus, decreased rapidly during incubation with sea water. Sea urchin sperm contained approx. 85% phospholipid in total lipid. Phosphatidylcholine (PC) was the principal lipid. Other phospholipids, however, remained at constant levels during incubation. Although the free fatty acid content gradually increased following dilution of dry sperm in sea water, the amounts of triacylglycerol and cholesterol ester were extremely low. Analysis by gas-liquid chromatography indicated most of fatty acid moieties in PC to be polyenoic. PC composed in part of unsaturated fatty acids was consumed to a greater extent during incubation than that consisting of saturated fatty acids. Furthermore, 1-palmitoyl-2-[1-14C]linoleoylphosphatidylcholine was transformed to 14C-labelled free fatty acid in a subcellular system. Thus, possibly, phospholipase A2 is present in sea urchin sperm. Also, [1-14C]oleic acid was immediately oxidized to 14CO2 by sperm. It is thus concluded that sea urchin sperm use phosphatidylcholine as a substrate for energy metabolism.

Animals↗
PubMed1988

Morphometrical and biochemical analysis on autofluorescent granules in various tissues and cells of the rats under several nutritional conditions.

The effects of age and nutritional conditions on accumulation of autofluorescent granules in various organs and tissues of male Sprague-Dawley rats were compared morphometrically. The relative intensity of the specific fluorescence of these autofluorescent granules was similar in all tissues and cells examined. In almost all cases, there were more autofluorescent granules in the 12-month experiment than in the 4-month one. Multiple necrotic foci of myofibrils with an accumulation of autofluorescent granules were seen in striated muscles in the rats on vitamin E-deficient diets for 12 months. In splenocytes, renal proximal convoluted tubules and hepatic cells, autofluorescent granules quantitatively increased significantly with an increase of the corn oil contents in the diets. The increase was rather marked in the splenocytes and renal epithelia of vitamin E-deficient rats. In the Purkinje cells and bronchial epithelial cells, no significant differences were noted according to the difference in the vitamin E and corn oil contents in diets. The accumulation of autofluorescent granules was not merely considered to be an age-related change, but to be influenced by a relationship to the cell metabolism and functional activity in various organs.

Animals↗
PubMed1988

Comparison of fluorescence characteristics of products of peroxidation of membrane phospholipids with those of products derived from reaction of malonaldehyde with glycine as a model of lipofuscin fluorescent substances.

The fluorescence characteristics of product (I), formed during the lipid peroxidation of rat liver phosphatidylcholine liposomes containing glycine, and fluorescent product (II), derived from the reaction of malonaldehyde with glycine, were examined to elucidate the mechanism of fluorescent chromophore formation. Fluorescent product (I) had a fluorescence emission maximum at 430 nm when excited at 360 nm; its fluorescence intensity decreases in alkaline medium, but is restored by readjustment of pH to neutrality. In contrast, fluorescent product (II) exhibited an emission maximum at 458 nm, and the fluorescence was quenched at acidic pH. The fluorescent substances formed during the lipid peroxidation of hemoglobin-free human erythrocyte ghost membranes had similar fluorescence characteristics to product (I). Gel filtration experiments showed that molecular size of fluorescent product (I) was larger than that of fluorescent product (II). The thiobarbituric acid-reactive substances released from peroxidizing liposomal phospholipids had a larger molecular size than malonaldehyde, and produced little or no fluorescence with glycine. It is concluded that the precursor of the fluorescent product formed during the lipid peroxidation of membrane phospholipids differs from malonaldehyde. The mechanism of the formation of blue emitting fluorescent material, believed to be a component of lipofuscin, seems to involve peroxidized phospholipids of the membrane.

Animals↗
PubMed1987

Regulatory functions of cyclic adenosine 3',5'-monophosphate in 1-methyladenine production by starfish follicle cells.

The biosynthesis of 1-methyladenine (1-MeAde) in follicle cells of the starfish, Asterina pectinifera, occurred in response to a gonad-stimulating substance (GSS). Simultaneously with 1-MeAde production, the intracellular cAMP level immediately increased following the administration of GSS. This level in follicle cells markedly depended on GSS concentration. Although 1-MeAde production was also induced by 1-methyladenosine, it caused no increase in cAMP content. It thus appears that the effect of GSS on starfish follicle cells results in the receptor-mediated formation of cAMP.

Adenine↗
PubMed1987

Maturation dependence of the turnover of phosphatidylinositides in rabbit red blood cells.

"Pulse-chase" experiments with erythrocytes and reticulocytes prelabelled with 32P-Pi revealed a high turnover of the monoester phosphate groups of PIP2 in reticulocytes, which declines strongly during maturation [Maretzki et al., Biomed. Biochim. Acta 45, 1227-1236 (1986)]. The 3H-inositol uptake exhibits a strong maturational loss. A carrier-mediated uptake of inositol in reticulocytes is suggested. In reticulocytes PI, PIP and PIP2 incorporated 3H-inositol in the relative distribution of 86; 5 and 9%, respectively, but only PI to a minor extent in erythrocytes. A small release of 3H-labelled inositol phosphates was found in reticulocytes, which was not stimulated by extracellular calcium during incubation. Determination of the 32P/3H-ratio in double-labelled phosphatidylinositides in reticulocytes demonstrated a very slow turnover of the diester phosphate bonds compared with that of the inositol phosphate ester groups.

Animals↗
PubMed1984

Formation of age pigment-like fluorescent substances during peroxidation of lipids in model membranes.

The formation of age pigment-like fluorescent substances during the lipid peroxidation of model membranes has been studied. Ferrous ion and ascorbate-induced lipid peroxidation of liposomal membranes containing phosphatidylethanolamine led to the formation of fluorescent substances which have characteristics similar to those of compounds derived from the reaction of phosphatidylethanolamine with purified fatty acid hydroperoxides. The fluorescent substances were accumulated in liposomal membranes, whereas thiobarbituric acid-reactive substances formed during lipid preoxidation were immediately released from the liposomal membranes. The thiobarbituric acid-reactive substances free from the membranes were not reactive with amino compounds such as phosphatidylethanolamine in liposomes or glycine in aqueous phase. It was suggested that the products reacting with amino compounds are short-lived, and may be rapidly inactivated after released into aqueous phase. The formation of fluorescent products was inefficient when phosphatidylethanolamine incorporated into the liposomes insensitive to lipid preoxidation was incubated with ferrous ion and ascorbate in the presence of liposomes sensitive to the peroxidation. The results suggest that some products generated from peroxidation-sensitive lipids react with the amino group of phosphatidylethanolamine molecules which are located on the same membranes, forming fluorescent substances. The presence of phosphatidylethanolamine in the membrane suppressed the formation of thiobarbituric acid-reactive substances, suggesting that phosphatidylethanolamine may react with radicals formed and terminate the propagation.

Aging↗
PubMed1983

Brain free fatty acids, edema, and mortality in gerbils subjected to transient, bilateral ischemia, and effect of barbiturate anesthesia.

Brain free fatty acids (FFAs) and brain water content were measured in gerbils subjected to transient, bilateral cerebral ischemia under brief halothane anesthesia (nontreated group) and pentobarbital anesthesia (treated group). Mortality in the two groups was also evaluated. In nontreated animals, both saturated and mono- and polyunsaturated FFAs increased approximately 12-fold in total at the end of a 30-min period of ischemia; during recirculation, the level of free arachidonic acid dropped rapidly, while other FFAs gradually decreased to their preischemic levels in 90 min. In treated animals, the levels of total FFAs were lower than the nontreated group during ischemia, but higher at 90 min of reflow, and the decrease in the rate of free arachidonic acid was slower in the early period of reflow. Water content increased progressively during ischemia and recirculation with no extravasation of serum protein, but the values were consistently lower in the treated group. None of the nontreated animals survived for 2 weeks; in contrast, survival was 37.5% in the treated group. It is suggested that barbiturate protection from transient cerebral ischemia may be mediated by the attenuation of both membrane phospholipid hydrolysis during ischemia and postischemic peroxidation of accumulated free arachidonic acid.

Anesthesia, General↗
PubMed1980

Isolation and analysis of age-related fluorescent substances in rat testes.

Fluorescent substances were extracted from rat testicular tissue with 2,2-dimethoxypropane (DMP) and analyzed by 2-dimensional thin layer chromatography (TLC). One substance that accumulated with increasing age of the animals was isolated and analyzed quantitatively by spectrophotofluorometry using quinine sulfate as a standard. This substance, which was designed as an age-related fluorescent substance (ARFS), exhibited an excitation maximum at 355 nm and an emission maximum at 490 nm. Its fluorescence was quenched by metal chelators and at alkaline pH, indicating it contained a conjugated Schiff base structure. Quantitative analysis of this substance in the testes of rats 1, 2, 11 and 20 months of age showed that it increased linearly with age. The relation of this substance to aging also was indicated by its detection in animals of different ages fed diets of both low and high unsaturation.

Aging↗
PubMed1980

Effect of transient ischemia on free fatty acids and phospholipids in the gerbil brain. Lipid peroxidation as a possible cause of postischemic injury.

The effect of transient bilateral carotid occulsion on levels of free fatty acids, phospholipids, and lipid peroxides in the brain was studied in gerbils. During occulsion, both saturated and polyunsaturated free fatty acids increased strikingly to approximately 11-fold in total by 30 minutes. During recirculation, however, a selectively rapid decrement occurred in arachidonic acid, while saturated fatty acids gradually decreased to their basal levels in 180 minutes. The peroxide level, estimated by a thiobarbituric acid test, did not change during occlusion, but was elevated on reperfusion. Phosphatidylethanolamine content decreased throughout the periods examined. These results do not support a hypothesis that lipid peroxidation is initated during ischemia by the lack of oxygen at the terminus of the mitochondrial respiratory chain. Instead, it is suggested that severe cerebral ischemia disintegrates membrane phospholipids, probably through activation of hydrolytic enzymes, and that overt peroxidative processes take place during reflow by means of restoration of oxygen supply. The peroxidative reactions may indeed, cause additional damage during the postischemic phase.

Animals↗