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Biomedical subjects

K Waku

Publications and source records attributed to K Waku.

At least 109 records · Page 6Linked to original sources
PubMed1985

CoA-independent transfer of arachidonic acid from 1,2-diacyl-sn-glycero-3-phosphocholine to 1-O-alkyl-sn-glycero-3-phosphocholine (lyso platelet-activating factor) by macrophage microsomes.

Macrophage microsomes catalyzed the transfer of arachidonic acid (20:4) from 1,2-diacyl-glycerophosphocholine (GPC) to 1-alkyl-GPC (lyso platelet-activating factor). This enzyme reaction did not require the presence of cofactors such as Co A. Free arachidonic acid or linoleic acid-labeled phospholipids failed to act as the acyl donor. These results suggest that the reaction is a CoA-independent direct transfer of arachidonic acid. This arachidonoyl transacylation system may play a very important role in the metabolism of lyso platelet-activating factor and also in the elimination or release of arachidonic acid from diacyl-GPC.

Adenosine Triphosphate↗
PubMed1985

The molecular species composition of diacyl-, alkylacyl- and alkenylacylglycerophospholipids in rabbit alveolar macrophages. High amounts of 1-O-hexadecyl-2-arachidonyl molecular species in alkylacylglycerophosphocholine.

The relative composition of molecular species of diacyl-, alkylacyl- and alkenylacylglycerophospholipids in rabbit alveolar macrophages was determined with reverse-phase high-performance liquid chromatography (HPLC). Diacylglycerophosphocholine (GPC) (22.3% of the total glycerophospholipids), alkylacylGPC (11.3%) and alkenylacylglycerophosphoethanolamine (GPE) (15.8%) were the predominant glycerophospholipids in rabbit alveolar macrophages. DiacylGPE (6.9%), diacylGPI (5.5%) and diacylGPS (3.6%) also occurred. 1,2-Diradyl-3-acetylglycerol derived from glycerophospholipids were each resolved into 19 separate peaks with reverse-phase HPLC. By gas-liquid chromatographic quantitation of each peak, 19-29 different molecular species were identified. DiacylGPC, GPE and GPS were mainly composed of saturate, monoene and diene species, such as the 16:0-16:0, 16:0-18:1, 18:0-18:1, and 18:0-18:2 species. The predominant molecular species composing diacylGPI was the 18:0-20:4 species, which represented 40% of this glycerophospholipid. Distinct differences were found in the distributions of arachidonyl molecular species between diacyl- and ether-containing GPC and GPE. Although diacylGPC and GPE included a small amount of arachidonyl molecular species, the 16:0-20:4 species was by far the most prevalent one which composed alkylacylGPC (39% of the total) and alkenylacylGPE (49% of the total). The 16:0-20:4 species of alkylacylGPC and alkenylacylGPE together comprised 60% of the total arachidonyl molecular species of glycerophospholipids. The high amounts of the 16:0-20:4 species in alkylacylGPC may serve as a good source of both the potent platelet-activating factor and the products of arachidonic cascade in the stimulated alveolar macrophages.

Animals↗
PubMed1985

Determination of the amounts of free arachidonic acid in resident and activated rabbit alveolar macrophages by fluorometric high performance liquid chromatography.

An improved method of high performance liquid chromatography (HPLC) has been developed for the separation and quantitation of low levels of free fatty acids as they occur in mammalian tissues. The fatty acid analysis is based on the esterification of the carboxylic group with 9-anthryldiazomethane (ADAM). HPLC separation and fluorescence measurement of fatty acid ADAM esters allow the determination of pmole amounts of fatty acids. The amounts of free fatty acids of resident and activated alveolar macrophages were determined by the fluorometric HPLC method. There were approximately 2 micrograms/10(6) cells of free fatty acids. In resident macrophages, free 20:4 was a minor component (0.8% of total free fatty acids), while significant amounts of 20:4 were found in the total glycerophospholipids, representing 16.6% of the total fatty acids. A marked increase in amounts of 20:4 (8 times) occurred in activated macrophages stimulated for 1 hr with opsonized zymosan. Small but significant increases (1.5 times) also occurred in other fatty acids. These results show that the release reaction of fatty acids was not selective for 20:4 in alveolar macrophages after the challenge with opsonized zymosan.

Animals↗
PubMed1984

Enhanced turnover of arachidonic acid-containing species of phosphatidylinositol and phosphatidic acid of concanavalin A-stimulated lymphocytes.

The incorporation of [32P]orthophosphate into phosphatidylinositol (PI) of pig lymphocytes was markedly increased by stimulation with concanavalin A. The labeling of PI with [3H]glycerol was also enhanced significantly, indicating that both de novo synthesis and recircular system (PI response) of PI were accelerated. This rapid labeling of PI might be related to the rapid breakdown of phosphatidylinositol 4,5-bisphosphate which was observed in various stimulated tissues. Concanavalin A also accelerated the labeling of phosphatidic acid with 32P and [3H]glycerol. To determine the dependence of this phenomenon on the fatty acid composition of both phospholipids, we separated PI and phosphatidic acid into individual molecular species. The predominant molecular species in PI was tetraene (81.6%) and those in phosphatidic acid were monoene (53.0%), diene (15.8%) and tetraene (19.2%), respectively. Interestingly, the incorporation of 32P into arachidonic acid-containing species (tetraene) was most rapidly elevated. On the other hand, the increment of 32P into saturated + monoene, diene and triene was relatively smaller and resembled that of [3H]glycerol. Similarly, the incorporation of 32P into tetraene of phosphatidic acid was preferentially accelerated. This is the first report concerning the metabolism of molecular species of phosphatidic acid in stimulated cells. These results indicate that the PI recirculating system is virtually dependent on tetraenoic species and that the participation of other molecular species is small. The increased de novo synthesis mainly depends upon molecular species other than tetraene. Arachidonic acid-containing species which turn over rapidly via the PI cycle may have an important role in the mitogenic triggering.

Animals↗
PubMed1984

The effect of plasma on platelet function in hypercholesterolemic rabbits and the changes in fatty acid composition of the plasma.

Rabbits were fed with 1% cholesterol-containing standard diet for 1 to 3 months. The arachidonic acid (AA)-induced aggregation of the platelet-rich plasma (PRP) of the control rabbits was accelerated by substitution of hypercholesterolemic plasma. The incorporation of 14C-AA into thromboxane B2 in platelets was increased approximately 1.6 times with PRP and 1.2 times with the washed platelet suspension (WPS) in hypercholesterolemic rabbits as compared with those of the control. Analysis of the fatty acid compositions of phospholipids and total lipids of hypercholesterolemic rabbits revealed an increase in AA of platelets and plasma, and a decrease in docosahexaenoic acid (DHA) in plasma. The AA/DHA ratio of plasma increased dependently on the period of feeding with the high cholesterol diet, and the increase in the ratio was parallel with the acceleration of platelet aggregation by AA in PRP.

Animals↗
PubMed1984

Selective incorporation of docosahexaenoic acid in rat brain.

The incorporation of [14C]docosahexaenoic acid (22:6) into various lipid classes was compared with that of [3H]arachidonic acid (20:4) in developing rat brains in order to characterize the retention of 22:6. The percentage distribution of 20:4 in neutral glycerides was similar to the mass distribution and, of the phospholipids, 20:4 was incorporated into choline glycerophospholipids and inositol glycerophospholipids in relatively higher amounts. The incorporation of labeled 22:6 differed from that of 20:4, as it was incorporated into ethanolamine glycerophospholipids and triacylglycerols in greater amounts in comparison with its mass distribution. Further division of ethanolamine glycerophospholipids into diacyl, alkylacyl and alkenylacyl types revealed that the high incorporation of radioactive 22:6 in ethanolamine glycerophospholipids was predominantly due to its rapid incorporation into diacyl and alkylacyl compounds. The distributions of both radioactively labeled 20:4 and 22:6 among the three types of ethanolamine glycerophospholipids were compared with those of radioactively labeled glycerol. The value of [3H]20:4/[3H]glycerol was much higher in alkenylacyl-GPE than in alkylacyl-GPE, and this indicates that 20:4 is incorporated into alkenylacyl-GPE by a deacylation-reacylation mechanism. In addition, [14C]22:6 was incorporated into ether-linked ethanolamine phospholipids in a similar manner to 20:4. This observation suggests that 22:6 may be incorporated into alkenylacyl-GPE by the same rearranging system, while another possibility is that preferential synthesis of hexaene species may occur in the desaturation of alkylacyl-GPE.

Animals↗
PubMed1984

Mobilization of arachidonic acid between diacyl and ether phospholipids in rabbit alveolar macrophages.

The metabolism of 20:4 (arachidonic acid) in alkenylacyl, alkylacyl and diacyl lipid classes in choline glycerophospholipids (CGP) and ethanolamine glycerophospholipids (EGP) in rabbit alveolar macrophages was examined. [3H]20:4 was very rapidly incorporated into diacyl glycerophosphocholine (GPC). After the removal of free 20:4, the radioactivity was gradually lost from diacyl GPC. Concomitantly, the radioactivities in alkylacyl GPC and alkenylacyl glycerophosphoethanolamine (GPE) were increased, indicating that 20:4 was mobilized from diacyl GPC to alkylacyl GPC and alkenylacyl GPE. The mobilization was considered to be a 20:4-specific event. The gradual accumulation of 20:4 in ether phospholipids leads to a high abundance of 20:4 in these lipids. These results suggest metabolic relationships between 20:4 and ether phospholipids, including platelet-activating factor (PAF).

Animals↗
PubMed1984

Turnover rates of the molecular species of ethanolamine plasmalogen of rat brain.

1,2-Diradyl-3-acetylglycerols prepared from 1-O-alk-1'-enyl-2-acylglycero-3-phosphoethanolamine (alkenylacyl-GPE, ethanolamine plasmalogen) and 1-alkyl-2-acylglycero-3-phosphoethanolamine (alkylacyl-GPE) of rat brain at 18 days of age were subfractionated into six species by AgNO3-impregnated TLC. The percent compositions of substractions were compared with that of 1,2-diacylglycero-3-phosphoethanolamine (diacyl-GPE). The incorporation rate of [1-3H]glycerol into each molecular species was also estimated to examine the turnover rate and selective synthesis of molecular species of ethanolamine phosphoglycerides (EPG). Among the molecular species of EPG, a major proportion contained polyunsaturated fatty chains, and the sum of tetraene-, pentaene-, and hexaene-containing species was greater than 65% in common with three classes of EPG. It was possible to calculate the turnover time, synthesis rate, and synthesis rate constant of ethanolamine plasmalogen in myelinating rat brain by the equation of Zilversmit et al. since the time-dependent change of specific activity and the distribution of molecular species indicated that each molecular species of alkenylacyl-GPE is synthesized from the corresponding species of alkylacyl-GPE. The observed turnover time of ethanolamine plasmalogen was about 5 h. The observed turnover times of the various molecular species were of the order: tetraene greater than or equal to hexaene greater than pentaene greater than or equal to monoene greater than or equal to diene. The synthesis rate constants of each molecular species, in the formation of alkenylacyl-GPE from alkylacyl-GPE, were of the order: hexaene greater than tetraene greater than pentaene greater than diene greater than or equal to monoene.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

The chemical form of cadmium in subcellular fractions following cadmium exposure.

Wistar rats were given drinking water containing 250 ppm Cd for 12 months. After excision of the kidney and liver, the organs were subfractionated into nuclear, mitochondrial, microsomal and cytosol fractions, and the chemical forms of Cd in the subcellular fractions were examined. Although approximately 90% of the total Cd was present in the cytosol, in the form of metallothionein, 3-5% was also present in the mitochondrial fraction and 5-7% in the microsomal fraction from both organs. By Sephadex G-75 gel filtration, after solubilizing the particulate fractions with sodium deoxycholate, approximately 89% of Cd in the microsomal fraction and 94% in the mitochondrial fraction eluted with the same retention time as that of metallothionein in both liver and kidney, while the remainder was found in a high molecular weight protein fraction. The Cd that eluted with the high molecular protein fraction may be involved in dysfunction in subcellular organelles. For estimating the toxicity of Cd associated with the high molecular weight fraction, rat liver microsomes and CdCl2 were mixed with 1% of sodium deoxycholate and the protein-Cd complex produced was isolated by eluting with Sephadex G-75. This complex had a strong toxicity toward the alcohol dehydrogenase activity (SH-enzyme), and the Ki values of the Cd-protein complexes decreased with increased amount of Cd bound to the microsomal protein fraction. The above results suggest that loosely bound Cd increased in the case of higher Cd/protein and plays a toxic role in the living cells.

Alcohol Oxidoreductases↗
PubMed1983

Occurrence of alkyl ether phospholipids in rabbit platelets: compositions and fatty chain profiles.

Rabbit platelets contained significant amounts of alkylacyl compounds (10.4%) in choline phosphoglycerides (CPG) and alkenylacyl compounds (46.3%) in ethanolamine phosphoglycerides (EPG). The fatty chain profiles of alkylacyl and diacyl CPG, and alkenylacyl and diacyl EPG were considerably different from each other. Alkylacyl CPG contained higher amounts of 16:0 (35.0%) and 20:4 (20.9%) than diacyl compounds (4.5% and 12.6%, respectively). On the other hand, alkenylacyl EPG included a large amount of 20:4 (58.2%) in comparison with diacyl analogues (28.8%).

Animals↗
PubMed1982

Distinctive selectivity for docosatetraenoic acid incorporation by Ehrlich ascites tumor cells.

Three polyunsaturated fatty acids were incorporated into the lipids of Ehrlich ascites cells to examine the selectivity of the synthetic enzymes for chain length and the number of double bonds. Arachidonic acid (20:4n-6) and timnodonic acid (20:5n-6) showed approximately similar patterns of incorporation into neutral acylglycerols, choline glycerophospholipids and ethanolamine glycerophospholipids. Further division of the lipids into diacyl and alkylacyl categories established that 20:4n-6 was incorporated at relatively lower amounts in the triacylglycerols and in the alkylacyl and alkenylacyl forms of the glycerophospholipids. The pattern of incorporation of radioactive 20:5n-3 into the phospholipids was similar to that for 20:4n-6, but there was no evidence for a selectively restrained incorporation into the triacylglycerols. The 22-carbon acid (22:4n-6) differed greatly from its shorter homolog (20:4n-6) in being incorporated in much greater amounts into triacylglycerols than into phospholipids. It did not appear to be present at an appreciably higher relative amount in either the alkyl diacylglycerols or in the ether-containing choline glycerophospholipids. Nevertheless, it occurred with exceptionally high specific activities in the alkylacyl and alkenylacyl forms of ethanolamine glycerophospholipids in a manner that suggests marked discrimination by the cytidine-mediated ethanolamine phosphotransferase. This distinctive selectivity provides evidence for special role for a 22-carbon acid in lipid metabolism.

Animals↗
PubMed1982

Ether phospholipids in guinea pig polymorphonuclear leukocytes and macrophages. Occurrence of high levels of 1-O-alkyl-2-acyl-sn-glycero-3-phosphocholine.

Significant proportions of the choline phosphoglycerides (CPG) were found to contain alkyl either-type moieties (e.g., 1-O-alkyl-2-acyl-glycero-3-phosphocholine) in both guinea pig peritoneal exudate polymorphonuclear leukocytes (16.4%) and macrophages (13.5%). High proportions of the ethanolamine phosphoglycerides (EPG) contained alkenyl either moieties in both cells (37.2 and 41.2%), while the proportions of the CPG containing alkenyl moieties and of the EPG containing alkyl moieties were shown to be small. The either phospholipid composition as well as the fatty chain profiles of these two types of cells had relatively similar patterns. However, the fatty chains at the 1- and 2-positions for alkenyl either, alkyl ether and diacyl phosphoglycerides showed considerable differences. The amount of 16:0 at the 1-position was higher in alkyl compounds than that in diacyl compounds of the CPG. This was also the case in either-containing and diacyl EPG. The most predominant fatty acids at the 2-position was 18:2, in each lipid class, except for the alkenyl CPG. The amounts of 20:4 and other polyunsaturated fatty acids were low in every lipid class, though ether compounds contained higher amounts of 20:4 than diacyl compounds, particularly for EPG.

Animals↗
PubMed1982

Changes in the composition of fatty chains of diacyl, alkylacyl and alkenylacyl ethanolamine and choline phosphoglycerides during the development of chick heart ventricular cells. High accumulation of 22-carbon fatty acid in ether phospholipids.

The phospholipids of embryonic chick ventricular cells were analysed at various developmental stages with respect to the composition of alkylacyl, alkenylacyl and diacyl ethanolamine and choline phosphoglycerides and for the fatty chain composition of these lipid classes. The percentage of alkylacyl and alkenylacyl choline phosphoglycerides increased in the course of the development. The fatty chain composition of ether-linked phosphoglycerides was significantly different from that of the diacyl compound. In general, both ether choline and ethanolamine phosphoglycerides consisted of a significantly higher percentage of 22-carbon fatty chains, such as 22:4, 22:5 and 22:6, compared to that of the diacyl compounds, throughout the earlier stage of development. During development, there was a dramatic increase of 20:4 and a decrease of 22:6, mainly in total ethanolamine phosphoglycerides but also in choline phosphoglycerides. A particularly significant decrease of 22:6 was found with diacyl ethanolamine phosphoglycerides. When 14C-labeled 22:4 and 3H-labeled 20:4 were incorporated into the ethanolamine and choline phosphoglycerides of ventricles in vitro, it was observed that 22:4 was mainly associated with ether phospholipids, especially the ethanolamine alkyl ether phospholipids, suggesting that there is a high selectivity of 22-carbon fatty acid to ether phospholipids during the synthesis of these compounds.

Aging↗
PubMed1982

The turnover of molecular species of phosphatidylinositol in Ehrlich ascites tumor cells.

It has been shown previously the 32Pi is incorporated into phosphatidylinositol 30 times faster than into the other phospholipids classes in Ehrlich ascites tumor cells, whereas [1-14C] glycerol is incorporated at almost the same rate (Waku, K., Nakazawa, Y. and MOri, W. (1976) J. Biochem. 79, 407-411). It was therefore suggested that there is a recirculating system (phosphatidylinositol leads to diacylglycerol leads to phosphatidic acid leads to CDP diacylglycerol leads to phosphatidylinositol) of phosphatidylinositol in Ehrlich ascites tumor cells. In this work, 32Pi or [1-3H] glycerol was injected into the peritoneal cavity of mice bearing Ehrlich ascites tumor cells from which the lipids were extracted after selected periods. Phosphatidylinositol was prepared and fractionated in the form of dimethylphosphatidic acid into six molecular species by AgNO3-impregnated TLC. The specific radioactivities of the fractionated species were determined. 32Pi was incorporated into diene molecular species and [1-3H] glycerol into monoene species with a higher rate than the other species and both precursors were incorporated into tetraene species rather slowly. 32P/3H values appeared to be at almost the same for each molecular species, although monoene species showed slightly lower values. These results suggest that there could be a recirculating of the phosphorylinositol moiety in each of the molecular species of phosphatidylinositol.

Animals↗
PubMed1981

The chemical form of cadmium in microsomal and mitochondrial fractions from rat liver and kidney after long term administration of cadmium chloride.

Wistar rats were given drinking water containing 250 ppm cadmium (Cd) for 12 months. After excising the kidney and liver, the organs were subfractionated into nuclear, mitochondrial, microsomal and cytosol fractions, and the chemical forms of Cd in the subcellular fractions were examined. Although approx. 90% of the total Cd was present in the cytosol, in the form of metallothionein, 3-5% was also present in the mitochondrial fraction and 5-7% in the microsomal fraction from both organs. Each membrane fraction was washed 3 times and there was no contamination of metallothionein from the cytosol according to Cd/protein ratios. By Sephadex G-75 gel filtration, after solubilizing the particulate fractions with sodium deoxycholate, approx. 89% of Cd in the microsomal fraction and 94% in the mitochondrial fraction eluted with the same retention time as that of metallothionein in both liver and kidney, while the remainder was found in a high molecular weight protein fraction. The Cd eluted with the high molecular protein fraction might be involved in dysfunctions in subcellular organelles.

Animals↗