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PubMed1994

Deoxycytidine kinase is phosphorylated in vitro by protein kinase C alpha.

Deoxycytidine (dCyd) kinase was effectively phosphorylated by protein kinase C. The reaction was rapid, occurring at 4 degrees C as well as at 37 degrees C and approximately 0.7 mol of phosphate could be incorporated per mol of deoxycytidine kinase. Phosphoserine was the primary amino acid to be phosphorylated. Phosphorylation of deoxycytidine kinase resulted in a 100% increase in the Vmax using dCyd as a substrate (52.16 +/- 1.3 versus 104.47 +/- 11.4 nmol/min/mg protein), and an increase in the apparent Km (2.0 +/- 0.2 microM versus 6.9 +/- 1.2 microM). The inactive antimetabolite, ara-C, is activated within a cell by deoxycytidine kinase phosphorylation of the prodrug. Recent studies have shown that ara-C activates protein kinase C in vivo [1]. Furthermore, ara-C has been shown to be metabolized to ara-CDP-choline via reversal of the cholinephosphotransferase [2] producing diglyceride, a cellular activator of protein kinase C. Thus, in situ, deoxycytidine kinase may be phosphorylated by protein kinase C with the result that self-potentiation of ara-C toxicity may occur via increased activity of deoxycytidine kinase.

Cytarabine↗
PubMed1988

Characteristics of lactobacilli isolated from dry fermented sausages.

A study of the microflora of Spanish dry fermented sausages showed a similar pattern to that observed in other sausages during ripening. Lactic acid bacteria and organisms growing on Mannitol-salt-agar increased during the first five days, remaining at constant levels afterwards. From MRS agar, 368 strains were isolated and characterized. All Lactobacillus strains (343) could be separated into three groups according to their reactions in the API-50 L system. The biochemical characteristics of the Lactobacillus strains analyzed were those typical of isolates from sausages and other meat products. The extracellular and intracellular lipolytic activities of some strains of the three groups were also studied. It is concluded that lipolytic activity of lactobacilli is mainly directed against mono- and diglycerides and short-chain fatty acid triglycerides.

Animals↗
PubMed1983

Arachidonic acid uptake into and release from guinea-pig endometrium in vitro on days 7 and 15 of the oestrous cycle.

Endometrium from guinea-pigs on Days 7 and 15 of the oestrous cycle (days of low and high endometrial prostaglandin F2 alpha production, respectively) was maintained in tissue culture for periods up to 24 h (uptake experiments) or 48 h (release experiments). Tritiated arachidonic acid (3H-AA) was incorporated into endometrial phospholipids and neutral lipids in a time-dependent manner. After 24 h of culture, phosphatidylcholine (PC) and phosphatidylethanolamine (PE) were the major phospholipids, and triglyceride (TG) was the major neutral lipid which had incorporated 3H-AA. PC, PE and phosphatidylserine/phosphatidylinositol (PS/PI) incorporated significantly more 3H-AA on Day 15 than on Day 7. TG also incorporated more 3H-AA on Day 15 than on Day 7, but the increase was not statistically significant. Tritiated oleic acid (3H-OA) was incorporated into endometrial phospholipids and neutral lipids in a time-dependent manner. No increase in uptake of 3H-OA occurred on Day 15 compared to Day 7. There appears to be a specific stimulation of the mechanisms involved in the uptake of arachidonic acid into guinea-pig endometrium (particularly into the phospholipids) at the end of the oestrous cycle. There was little apparent release of 3H-AA from any endometrial lipid class, except diglyceride (DG) and monoglyceride (MG), on Day 7. In contrast, there was an apparent 50 to 80% decrease in the 3H-AA content of several endometrial lipid classes, particularly PC, PE and TG, on Day 15. Overall, the uptake and release studies suggest that PC, PE and possibly TG form the source of free arachidonic acid for PGF2 alpha synthesis by the guinea-pig endometrium.

Animals↗
PubMed1986

The effect of endogenous eicosapentaenoic acid on PMN leukotriene and PAF biosynthesis.

Caseinate elicited peritoneal PMNs were obtained from rats fed Menhaden fish oil or control rat chow. Total polyeneoic fatty acids were measured and compared with PAF and leukotriene biosynthesis after stimulation with the calcium ionophore A23187. PAF was measured by acetate incorporation and its molecular species were measured by GCNICIMS after conversion to the PFB-diglyceride. Eicosapentaenoic acid enrichment lowered the total amount of leukotriene B4 but increased the amount of LTB5 proportionally to the increase in the fatty acid. Although concentrations of 20:5 exceeded those of 20:4, PAF biosynthesis was not inhibited nor were the relative amounts of its molecular species dramatically altered.

Animals↗
PubMed1987

The effect of malathion and gamma-BHC on the lipid metabolism in relation to reproduction in the tropical teleost, Clarias batrachus.

In the present study, female Clarias batrachus were exposed to two sublethal concentrations of gamma-BHC (2 and 8 microg litre(-1)) and malathion (1 and 4 microl litre(-1)) for 4 weeks during different phases of their reproductive cycle. Impact of these pesticides on free fatty acids, monoglycerides, diglycerides, triglycerides, phospholipids, free and esterified cholesterol in the liver, plasma, ovary and muscle was assessed. During the pre-vitellogenic and regressed phases, they suppressed the levels of fatty acids and glycerides in the liver, but had no effect on their levels in the plasma, ovary and muscle. However, in the vitellogenic phase, fatty acids in the liver and plasma were increased, but were decreased in the ovary and muscle. Glycerides were also decreased in the studied tissues. In the post-vitellogenic phase, these pesticides increased the levels of fatty acids and glycerides in the liver and ovary, but decreased their levels in the plasma. Both pesticides decreased hepatic phospholipids in the pre-vitellogenic phase, while in the vitellogenic phase only gamma-BHC reduced its levels in the liver. These pesticides also restricted their mobilisation to the ovary. Cholesterol biosynthesis seemed unaffected, but the hydrolysis of esterified cholesterol to free cholesterol was adversely affected during the period of estrogen biosynthesis.

Journal Article↗
PubMed1981

The effects of space flight on some rat liver enzymes regulating carbohydrate and lipid metabolism.

We have examined, in the livers of rats carried aboard the Cosmos 936 biosatellite, the activities of about 30 enzymes concerned with carbohydrate and lipid metabolism. In addition to the enzyme studies, the levels of glycogen and of the individual fatty acids in hepatic lipids were determined. Livers from flight and ground control rats at recovery (R0) and 25 days after recovery (R25) were used for these analyses. For all parameters measured, the most meaningful comparisons are those made between flight stationary (FS) and flight centrifuged (FC) animals at RQ. When these two groups of flight rats were compared at R0, statistically significant decreases in the activity levels of glycogen phosphorylase, alpha-glycerol phosphate acyl transferase, diglyceride acyl transferase, aconitase and 6-phosphogluconate dehydrogenase and an increase in the palmitoyl CoA desaturase were noted in the weightless group (FS). The significance of these findings was strengthened by the fact that all enzyme activities showing alterations at R0 returned to normal 25 days postflight. When liver glycogen and total fatty acids of the two sets of flight animals were determined, significant differences that could be attributed to reduced gravity were observed. The weightless group (FS) at R0 contained, on the average, more than twice the amount of glycogen than did the centrifuged controls (FC) and a remarkable shift in the ratio of palmitate to palmitoleate was noted. These metabolic alterations, both in enzyme levels and in hepatic constituents, appear to be characteristic of the weightless condition. Our data seem to justify the conclusion that centrifugation during flight is equivalent to terrestrial gravity.

Animals↗
PubMed1981

Effect of butylated hydroxytoluene on the lipid composition of rat liver.

Hepatic lipids were studied in Sprague-Dawley male rats given butylated hydroxytoluene(BHT) at a level of 1.20% for 1 week. BHT significantly increased cholesteryl esters and phospholipids but decreased triglycerides, non-esterified fatty acids and diglycerides. BHT also increased phosphatidylethanolamine or decreased phosphatidylinositol and lysophosphatidylcholine. Fatty acid composition of each lipid class was also changed by BHT-feeding. The decrease in 16 : 1/16 : 0, 18 1/18 : 0 and 20 : 4/18 :2 ratios of total lipids, non-esterified fatty acids or phospholipids of BHT-given rats suggests that BHT decreases the activity of fatty acid desaturase in the liver.

Animals↗
PubMed1991

Characteristics of phosphoinositide-specific phospholipase C activity from mouse pancreatic islets.

In pancreatic islets the bulk of phosphoinositide-specific phospholipase C (PI-PLC) activity was cytosolic. The soluble enzyme was activated by submicromolar concentrations of Ca2+, independent of calmodulin. It was unaffected by glucose and a series of glycolytic intermediates, including glyceraldehyde 3-phosphate. These observations lend support to the hypothesis that glucose-stimulated inositol triphosphate production in islets may be secondary to and provoked by glucose-mediated Ca2+ influx. All four pyridine nucleotides stimulated PI-PLC. Phosphatidylinositol hydrolysis was also stimulated by dioleine and arachidonic acid, and by the polyamines, putrescine and spermine. Phosphatidylinositol hydrolysis was inhibited by chlorpromazine, tetracaine, ATP, 5'-AMP, inorganic pyrophosphate and by phosphatidylinositol 4,5-bisphosphate, phosphatidylcholine and phosphatidylserine--but not affected by phosphatidylethanolamine. The cyclic nucleotides, cAMP and cGMP had no effect on the enzyme, and GTP-gamma-S did not activate the enzyme event at very low Ca2+ concentrations. The diglyceride lipase inhibitor, RHC 80267, and the cyclooxygenase inhibitor, indomethacin, had no effect on PI-PLC activity.

Animals↗
PubMed1993

Differential involvement of phospholipase A2 in phorbol ester-induced luteinizing hormone and growth hormone release from rat anterior pituitary tissue.

The protein kinase C (PKC) activator, phorbol 12,13-dibutyrate (PDBu) induced the release of both luteinizing hormone (LH) and growth hormone (GH) from proestrous rat anterior pituitary pieces in vitro. Phorbol 12,13-dibutyrate-induced LH, but not GH release was readily inhibited by the phospholipase A2 (PLA2) inhibitors, quinacrine, aristolochic acid, ONO-RS-082 and chloracysine. Furthermore, PDBu induced release of [3H]arachidonic acid ([3H]AA) from pre-labelled anterior pituitary tissue that was prevented in the presence of quinacrine, aristolochic acid and ONO-RS-082 but not the diglyceride lipase inhibitor RHC 80267. The effect of PDBu was completely inhibited by staurosporine and the selective PKC inhibitor Ro 31-8220 but only partially by low concentrations of H7; consistent with the involvement of both H7-sensitive and H7-resistant forms of PKC in the activation of PLA2 by PDBu. The protein synthesis inhibitor cycloheximide inhibited the release of both [3H]AA and LH that had been induced by PDBu, whereas LH release induced by the PLA2 activator mellitin was cycloheximide-insensitive. These results suggest that PKC activators may induce LH but not GH release from anterior pituitary tissue by a mechanism involving activation of a PLA2, brought about by a process which is reliant on protein synthesis.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1983

Uncoupled release of protein and lipid in a protein-secreting bacterium, Bacillus brevis 47.

Bacillus brevis 47 was found to release approx. 10% of the total cellular lipids into the medium, and the protein secretion process in B. brevis 47 was studied to determine whether any relationship exists with lipid synthesis or alteration in the lipid composition. B. brevis 47 contained the usual phospholipids such as phosphatidylethanolamine, phosphatidylglycerol and cardiolipin as well as diglycerides as major neutral lipids. The extracellular lipid consisted of the same constituents as the cellular lipid but with a significantly altered composition. Divalent cations such as Ca2+, which specifically inhibit protein secretion, had no effect on the lipid release. A nonprotein-secreting mutant released lipid to the same extent as wild-type cells. Based on these results, we conclude that protein secretion occurs independently of lipid release.

Bacillus↗
PubMed1986

The role of oxygen deficiency and cytosolic reactions in cell growth.

It has been suggested that a decrease in the availability of oxygen to certain tissues may lead to increased metabolism of glucose through the hexose monophosphate shunt pathway and to increased synthesis of polyols, in particular myoinositol. It is further suggested that these "cytosolic reactions" result in stimulation of the phosphatidylinositol cycle by increasing substrate availability (i.e. phosphatidate, diglyceride and inositol). A relative decrease in local oxygen availability may therefore play a role in cell proliferation and differentiation and in the etiology of cancer, diabetic sequelae and obesity.

Citric Acid Cycle↗
PubMed1981

Effects of four bisphenolic antioxidants on lipid contents of rat liver.

Hepatic lipids were studied in Sprague-Dawley male rats given, 2,2'-methylenebis(4-ethyl-6-tert-butylphenol), 2,2'-methylenebis(4-methyl-6-tert-butylphenol), 4,4'-butylidenebis(3-methyl-6-tert-butylphenol) or 4,4'-methylenebis(2,6-di-tert-butylphenol) at a level of 1.135 mmol% for 1 week. 4,4'-Butylidenebis(3-methyl-6-tert-butylphenol) induced fatty liver and increased triglyceride, diglyceride and cholesteryl-ester concentrations, 7.1-, 5.8- and 6.1-fold, respectively. Plasma triglycerides, total cholesterol and non-esterified fatty acids were markedly decreased. It would appear that the fatty liver resulted mainly from defective fat excretion from the liver. The other bisphenols produced a little change in liver lipids.

Animals↗
PubMed1991

Application of liquid chromatography-thermospray mass spectrometry in the analysis of glycerophospholipid molecular species.

We report the application of high-performance liquid chromatographic (HPLC) separation with ultraviolet detection and direct, on-line, structural analyses by mass spectrometry of glycerobenzoate derivatives from complex mixtures of phospholipid molecular species. Individual phospholipids were resolved from total lipid extracts by thin-layer chromatography (TLC). Diradylglycerols were released from phospholipids by phospholipase-C treatment, converted to diradyl glycerobenzoates and subsequently separated by TLC into subclasses (alk-1-enylacyl, alkylacyl and diacyl types). The molecular species within each subclass were resolved by HPLC with an octadecyl reversed-phase column in acetonitrile-isopropanol (80:20, v/v). Individual peaks were quantitated at the picomole level by measuring absorbance at 230 nm. After post-column addition of methanol-0.2 M ammonium acetate (50:50, v/v), peaks were introduced through the thermospray interface into a VG Masslab 30-250 quadrupole mass spectrometer. Molecular species showed as base peaks the salt adducts of the molecular ion which permitted easy deduction of the overall fatty acyl composition. In addition, the diglyceride fragment of each species was found at [MH - 122]+ and two fragments formed by the loss of the fatty acyl groups (R) in the sn-1 or sn-2 position were found at [M - R1]+ and [M - R2]+, respectively. Since preferential release of either fatty acyl group was observed in positional isomers, the ratio of the intensity of these fragments gave information on the position of the fatty acyl groups in the individual HPLC peaks. We show that the use of on-line mass spectrometry, however, provides easy identification of all molecular species present in a complex phospholipid mixture, even when more than one molecular species is contained in an HPLC peak.

Chromatography, High Pressure Liquid↗
PubMed1992

Quantification of distinct molecular species of the 2-lyso metabolite of platelet-activating factor by gas chromatography-negative-ion chemical ionization mass spectrometry.

The biological activity of platelet-activating factor (PAF) is comprised by a few molecular species of phosphatidylcholine which contain a fatty alcohol connected by an ether linkage to the sn-1 position of the glycerol backbone and an acetate ester at the sn-2 position. The various molecular species of PAF differ in chain length and degree of unsaturation in the fatty alcohol residue side-chain. PAF is rapidly hydrolyzed to lyso-PAF by an acetylhydrolase enzyme which is quite active in a number of cells that synthesize PAF. We describe a method for quantitation of lyso-PAF which involves conversion to its propionate derivative in the presence of an internal standard (deuterium-labelled PAF), digestion to the diglyceride with Bacillus cereus phospholipase C, conversion to the pentafluorobenzoate derivative and capillary column gas chromatographic-negative-ion methane chemical ionization mass spectrometric analysis. Distinct molecular species of lyso-PAF can be individually quantitated at levels of 1 ng or less. These methods are applied to the demonstration of lyso-PAF accumulation in renal tissue from transplanted allografts undergoing acute rejection, in renal tissue from kidneys subjected to cold storage and autotransplantation, and in intestinal mucosa subjected to warm ischemia and reperfusion.

Animals↗
PubMed1992

Separation of acidic and neutral lipids by aminopropyl-bonded silica gel column chromatography.

The separation of acidic and neutral lipids by aminopropyl-bonded silica gel column chromatography is presented. Total lipid extracts from Escherichia coli and human spermatozoa were loaded onto pre-packed aminopropyl-bonded silica gel columns and the lipids separated into four fractions. Non-polar lipids including cholesterol esters, triglycerides, diglycerides, monoglycerides and cholesterol, were eluted with 4 ml of isopropanol-chloroform (1:2, v/v) (fraction 1); free fatty acids were eluted with 4 ml of 2% acetic acid in diethyl ether (fraction 2); neutral polar lipids, including phosphophatidylethanolamine, phosphatidylcholine, sphingomyelin and neutral glycolipids, were eluted with 4 ml of methanol (fraction 3); and, finally, polar acidic lipids, including phosphatidylglycerol, cardiolipin, phosphatidylinositol, phosphatidylserine, seminolipid lipid A and acidic glycosphingolipids, were eluted with 4 ml of chloroform-methanol-0.8 M sodium acetate (60:30:4.5, v/V/V) (fraction 4). The recoveries for the different lipids ranged between 89 and 98% and the intra-assay variation, expressed as the standard deviation, was less than 5%.

Chromatography, Liquid↗
PubMed1988

The effects of a choline deficiency on the lipid composition and ethanol tolerance of Drosophila melanogaster.

1. A reduction in the dietary concentration of choline, an essential nutrient for Drosophila melanogaster, from the optimal concentration of 80 micrograms/ml of defined medium to 8 micrograms/ml diminished the level of tissue phosphatidylcholine to less than one-third the normal level in third instar larvae without significantly altering the amount of phosphatidylethanolamine. 2. The rates of synthesis of phospholipids, triglycerides, diglycerides and monoglycerides were reduced by the choline-deficiency, and the chain length of fatty acids in lipids was shortened. 3. The activity of succinic dehydrogenase, a mitochondrial enzyme, was decreased by the deficiency, but the activities of fumarase, sn-glycerol-3-phosphate dehydrogenase, alcohol dehydrogenase, sn-glycerol-3-phosphate oxidase and fatty acid synthetase were unaffected. A choline-deficiency did not alter the ultrastructure of mitochondria of larval fat body cells. 4. Choline-deficient individuals were more susceptible to the toxic effects of ethanol during larval and pupal development, and less adept at utilizing ethanol as a substrate for adult tissue synthesis.

Animals↗
PubMed1989

Protein phosphorylation and the dependence on Ca2+ and GTP-gamma-S for exocytosis from permeabilised mast cells.

Exocytosis in permeabilised mast cells requires only that the concentrations of Ca2+ and GTP-gamma-S (the essential effectors) are elevated into the micromolar range of concentrations. These act through an unidentified Ca2(+)-binding protein and an uncharacterized G-protein (GE). There is no requirement for ATP in the final stages of the secretory pathway. However, mast cells permeabilised in the absence of ATP rapidly become refractory to stimulation due to a reduction in the affinity for the essential effectors. Here, we show that responsiveness may be restored by the addition of ATP. The characteristics of such ATP-dependent secretion have been examined. Preincubation (prior to permeabilization) of the cells with phorbol ester enhances affinity to Ca2+, and introduction of neomycin reduces Ca2+ affinity. AMG.C16, an ether-linked analogue of diglyceride, inhibits secretion in a manner which can be partially reversed by elevating the concentration of ATP. These observations indicate that while protein phosphorylation does not comprise a step in the triggering of exocytosis, a primed condition most likely involving a state of protein phosphorylation, and maintained by reactions catalysed by protein kinase C, is essential.

Adenosine Triphosphate↗
PubMed1990

Uptake, distribution and release of 3H-arachidonic acid from human endometrium.

The lysophosphatide acyltransferase blocking agent ethylmercurisalicylate (merthiolate) was used to investigate the uptake and release of arachidonic acid from explants of human endometrium in short term tissue culture. Tissue explants were (a) incubated with 3H-arachidonic acid for 1-24 h in the presence or absence of 0.5-50 microM merthiolate, and (b) prelabelled with 3H-arachidonic acid for 18 h followed by incubation with or without 50 microM merthiolate for 1-24 h. Neutral lipids, phospholipids and arachidonic acid were separated by thin layer chromatography and uptake and release of 3H-arachidonic acid expressed as % total uptake. The triglyceride pool was the main target for arachidonic acid uptake. Incorporation increased from 9.1% at 1 h to 56.6% at 24 h. Uptake into phospholipids increased from 8.1% at 1 h to 19.6% at 24 h with phosphatidylcholine accounting for 3.8% and 8.8% respectively. Incubation with 50 microM merthiolate rapidly reduced uptake into triglycerides (to 1.8% at 1 h and 0.9% at 24 h), whereas the effect on uptake into phospholipids (5.9% at 1 h, 3.4% at 24 h) was much less marked. There was a dose related inhibition of arachidonic acid incorporation into both triglycerides and phospholipids, but a lower dose of merthiolate (1 microM) was required to reduce uptake into triglycerides than into phospholipids (5 microM). Uptake into mono- and diglycerides was low and unaffected by merthiolate. Incubation of prelabelled tissue with 50 microM merthiolate resulted in a 20% increase in the release of arachidonic acid from triglycerides and a corresponding accumulation of labelled monoglyceride.(ABSTRACT TRUNCATED AT 250 WORDS)

Arachidonic Acid↗