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PubMed1977

Specific interaction of concanavalin A with glycolipid monolayers.

The effect of 131I-labelled concanavalin A on the surface pressure and surface radioactivity of monolayers formed from phospholipids and from natural and synthetic glycolipids has been studied. The lectin binds to and penetrates dipalmitoyl phosphatidylcholine monolayers at a surface pressure of 15 dynes/cm and this interaction is inhibited by the presence of alpha-methyl mannose in the subphase. At surface pressures of 25 dynes/cm or higher, concanavalin A will interact with monoglucosyl diglyceride or diglucosyl diglyceride from Acholeplasma laidlawii and with synthetic glycolipids containing 2 or 3 alpha 1 leads to 4-linked D-glucose residues in the headgroup, but not with phosphatidylcholine, phosphatidylethanolamine, phosphatidylglycerol, or with the ganglioside II3NeuAc-GgOse4-Cer. The binding to the glycolipid sugar group and penetration of the hydrocarbon region seem to occur simultaneously, as the time courses for the development of surface pressure and surface radioactivity coincide.

Cell Membrane↗
PubMed1978

Biochemical aspects of the visual process. XXXVII. Evidence for lateral aggregation of rhodopsin molecules in phospholipase C-treated bovine photoreceptor membranes.

Photoreceptor membranes derived from isolated bovine rod outer segments, are subjected to treatment with phospholipase C (Bacillus cereus). This results in varying degrees of hydrolysis of the membrane phospholipids into diglycerides and water soluble phosphate esters without loss of rhodopsin. Electron microscopic observations of thin sections and freeze-fractured preparations indicate extrusion of diglycerides from the membranes and their coalescence to lipid droplets, beginning at 20% hydrolysis of phospholipids. After 90% hydrolysis of phospholipids membranous structures are still present. The rhodopsin is located in these structures, presumably in the form of two-dimensional lateral aggregates. This explains the cross-fracturing of the membranous structures, regularly observed upon freeze-fracturing of the phospholipase-treated photoreceptor membranes.

Animals↗
PubMed1992

A novel fluorescent fatty acid, 5-methyl-BDY-3-dodecanoic acid, is a potential probe in lipid transport studies by incorporating selectively to lipid classes of BHK cells.

The 5-methyl-BDY-3-dodecanoic acid (B12FA) labelling of BHK cell lipids was analyzed by thin layer and reverse phase column chromatography. Incorporation to phospholipids was selective: over 90% of B12FA label was enriched in phosphatidylcholine. The major molecular species of PC was that containing palmitate as the unlabelled fatty acid. Small amounts of label was also found in other phosphoglycerides, but not in sphingomyelin. Triglycerides and diglycerides constituted the main B12FA-labelled neutral lipid classes; however, no label was found in cholesterol esters. B12FA was degraded to shorter homologues, which had significantly slower lipid incorporation rates. B12FA-labelled cells displayed in a microscope initially green reticular type fluorescence, but later red spherical structures, representing neutral lipid droplets, could also be seen. It is concluded that B12FA does not incorporate indiscriminately to all lipid classes of BHK cells, but is enriched to PC, diglycerides and triglycerides, which could be utilized in studies on lipid transport as well as metabolism.

Animals↗
PubMed1994

Effects of bryostatin 1 and other pharmacological activators of protein kinase C on 1-[beta-D-arabinofuranosyl]cytosine-induced apoptosis in HL-60 human promyelocytic leukemia cells.

We have demonstrated previously that bryostatin 1, a macrocylic lactone with putative protein kinase C (PKC)-activating properties, synergistically augments the antileukemic actions of the deoxycytidine analog 1-[beta-D-arabinofuranosyl]cytosine (ara-C) in HL-60 human promyelocytic leukemia cells (Grant et al., Biochem Pharmacol 42: 853-867, 1991), and that this effect appears to be related to sensitization to ara-C-induced apoptosis (Grant et al., Cancer Res 52: 6270-6278, 1992). In the present studies, we have assessed the extent of this damage by quantitative spectrofluorophotometry of small molecular weight, double-stranded DNA fragments in order to provide: (a) a more complete characterization of the interaction between ara-C and bryostatin 1, and (b) a direct comparison of the relative effects of bryostatin 1 treatment with other pharmacological manipulations known to modulate protein kinase C activity. Exposure of cells to ara-C (10(-9) to 10(-4) M; 1-24 hr) induced time- and concentration-related increases in the extent of DNA fragmentation. Treatment with bryostatin 1 (10(-11) to 10(-7) M; 1-24 hr) alone failed to induce DNA damage, but promoted substantial time- and concentration-related increases in the extent of fragmentation induced by a subsequent 6-hr exposure to ara-C. Maximal potentiation of fragmentation (e.g. 2- to 3-fold greater than that obtained with ara-C alone) was observed following a 24-hr pretreatment with 10(-8) M or 10(-7) M bryostatin 1, and correlated closely with enhanced inhibition of HL-60 cell clonogenicity. The stage-1 tumor-promoter phorbol dibutyrate potentiated the effects of ara-C in a biphasic manner, maximally augmenting the response at 2.5 x 10(-8) M, but exerting no effect at 10(-7) M, whereas the stage-2 tumor-promoter mezerein failed to augment ara-C-related DNA fragmentation at low concentrations, and antagonized ara-C action at high concentrations. In contrast, ara-C-related DNA fragmentation was attenuated or abolished either by continual preexposure to synthetic diglyceride or by pretreatment with exogenous phospholipase C at all concentrations tested. Increased DNA fragmentation was not specifically related to recruitment of cells into S-phase or enhancement of ara-C-related cellular differentiation. Finally, concentrations of bryostatin 1 that maximally potentiated ara-C-related DNA fragmentation were associated with virtually complete down-regulation of total cellular PKC activity, whereas diglyceride and phospholipase C, which suppressed the response to ara-C, moderately increased total PKC activity.(ABSTRACT TRUNCATED AT 400 WORDS)

Antineoplastic Agents↗
PubMed1989

In vitro studies of the inhibition of protein kinase C from rat brain by di-(2-ethylhexyl)phthalate.

The environmental contaminant di(2-ethylhexyl)phthalate (DEHP) has been shown to inhibit the phosphorylation of histone by purified protein kinase C (PK-C) from rat brain in a concentration-dependent manner. The inhibition does not involve making the substrate unavailable, although DEHP does bind to some extent to histone. DEHP displaces phorbol dibutyrate from PK-C, indicating that DEHP binds to the regulatory domain of the enzyme. Since DEHP does not affect the PK-C dependent phosphorylation of protamine, DEHP probably does not bind at the catalytic site. DEHP non-competitively blocked activation of PK-C by either phosphatidyl serine or calcium ion. Inhibition of histone phosphorylation by DEHP was enhanced if diglyceride was present, and the enhancement was stereoselective for the isomeric form of the diglyceride. The mechanism of the inhibition is thought to involve interference with the interaction between calcium ion and the regulatory domain of PK-C, and would have significance only for those PK-C substrates that require calcium activation of the enzyme. Thus the presence of DEHP in the high nanomolar concentration range alters the effective substrate specificity of PK-C.

Animals↗
PubMed1978

Lipids of the Streptomycettes. Structural investigation and biological interrelation a review.

During a systematic investigation of lipids of Streptomycetes a series of compounds of biochemical and microbiological interest have been isolated and characterized. These include several menaquinones, glycosyl diglycerides (glucuronosyl and isoladobinosym diglycerides), two ornithino lipids and a diol phospholipid. Some of these lipids were not known previously as constituents of streptomycete cells although they have been encountered elsewhere; others have proved to be novel lipids. The results of structural studies of these lipids are reviewed and some of their possible biological functions are discussed.

Actinomyces↗
PubMed1991

A continuous fluorometric assay for phospholipase C from Clostridium perfringens.

A fluorescent assay for Clostridium perfringens phospholipase C is described using 1-palmitoyl-2-[6(pyren-1-yl)hexanoyl]-sn-glycero-3- phospho-N-(trinitrophenyl)aminoethanol (PPHTE) as the substrate. This method is based on the decrease of the quenching of pyrene monomer fluorescence when phospholipase C hydrolyzes PPHTE into pyrenediglyceride and phospho(trinitrophenyl)-aminoethanol. The hydrolysis of egg lecithin/PPHTE (25:1 molar ratio) substrate by C. perfringens phospholipase C was linear with time for at least 2 min. Optimal conditions for the hydrolysis by phospholipase C were 50 mM Tris-HCl pH 7.0-30 mM CaCl2/63 microM egg lecithin and 2.5 microM PPHTE. The Km and Vmax values for the hydrolysis of egg lecithin/PPHTE vesicles were 28 microM and 280 pmol min-1, respectively. The detection limit of the assay was 40 microU of C. perfringens phospholipase C. When diglyceride was included into egg lecithin/PPHTE vesicles up to 30 mol% the reaction velocity increased 13-fold. Higher molar proportions of diglyceride were inhibitory. When the hydrolysis of mixtures of different naturally occurring phospholipids and PPHTE was studied egg lecithin was found to be the best substrate. When dipalmitoylphospholipids with different polar head groups were used the reaction velocity decreased in the order egg lecithin greater than or equal to dipalmitoylphosphatidylserine greater than dipalmitoylphosphatidic acid greater than dipalmitoylphosphatidylcholine greater than dipalmitoylphosphatidylglycerol.

Calcium Chloride↗
PubMed1983

HPLC analysis of neutral glycolipids: an aid in the diagnosis of lysosomal storage disease.

Concentrations of GL-la (glucocerebroside) (8.36 nmol/ml), GL-2a (lactosylceramide) (4.03 nmol/ml), GL-3a (globotriosylceramide) (2.25 nmol/ml) and GL-4a (globotetraosylceramide) (2.87 nmol/ml) have been determined in normal plasma and compared to concentrations in the plasma from patients with Gaucher, Krabbe, Fabry, Sandhoff and Tay-Sachs diseases as well as with hypercholesterolemia. HPLC analysis of perbenzoylated glycolipid derivatives (isolated and purified by modification of an existing procedure) was performed on samples equivalent to 50 to 100 microliter of plasma. The sensitivity could be readily increased ten-fold. We have employed a novel internal standard-monogalactosyl diglyceride, a plant glycolipid, commercially available in pure form. Analysis was performed on a 5 micron ultrasphere silica column, using a gradient of isopropanol in hexane rather than the more usual dioxane in hexane. Our gradient exhibited an essentially flat baseline precluding the necessity of a reference cell. Recoveries of glycolipids added to plasma (95%), experimental yields (60%) and standard curves are presented and discussed. A method is also presented for the separation of GL-la and monogalactosyl diglyceride derivatives for rapid (8 minute) isocratic analysis of multiple samples from Gaucher patients. The benefits of such a simple, reproducible HPLC technique are discussed.

Chromatography, High Pressure Liquid↗
PubMed1986

Stimulation of parathyroid hormone secretion by phorbol esters is associated with a decrease of cytosolic calcium.

Unlike in other endocrine systems calcium inhibits parathyroid hormone (PTH) secretion and this inhibition is paralleled by a rise of cytosolic calcium concentration ([Ca]i). Because of evidence that diglyceride levels and protein kinase C activity are also decreased by high extracellular calcium we have investigated the effects of 12-O-tetradecanoylphorbol-13-acetate (TPA), an activator of protein kinase C, on [Ca]i and PTH secretion using dispersed bovine parathyroid cells. At 1.5 mM medium calcium TPA enhanced PTH secretion and caused reduction of [Ca]i from 639 +/- 36 nM (SE) to 335 +/- 21 nM (P less than 0.001); at 0.5 mM calcium TPA was ineffective. Moreover, TPA suppressed the rise of [Ca]i evoked by high extracellular calcium. Thus TPA presumably stimulates PTH secretion via activation of protein kinase C, and the lowering of [Ca]i may TPA presumably stimulates PTH secretion via activation of protein kinase C, and the lowering of [Ca]i may be a secondary event related to diglyceride availability.

Animals↗
PubMed1981

Membrane-active agents. Effect of various anesthetics and chlorpromazine on arterial lipid metabolism.

The local anesthetic lidocaine was studied for its effects on lipid metabolism in aortas from normal rats, rabbits, and cholesterol-fed (atherosclerotic) rabbits in vitro. Incubation of aortas in the presence of 3--5 mM lidocaine resulted in a statistically significant reduction in the incorporation of [14C]oleate into cholesteryl esters and phosphatidylcholine. Additionally, significant increases in [14C]oleate incorporation into the diglyceride fraction of atheromatous rabbit aortas was observed with a trend to greater incorporation into the diglyceride fraction of normal rat and rabbit arteries as well. The most significant overall effect of lidocaine was its inhibition (50--90%) of the arterial sterol esterification. Assays of acylCoA : cholesterol acyltransferase (ACAT, EC 2.3.1.26) in isolated arterial microsomes revealed that, in addition to local anesthetics (e.g., lidocaine), other membrane-active agents such as chlorpromazine and methoxyflurane inhibit ACAT; this suggests ACAT may be regulated by alterations in the biophysical properties of its membrane milieu.

Acetyl-CoA C-Acyltransferase↗
PubMed1992

Isolation of experimental anti-AIDS glycerophospholipids by micro-preparative reversed-phase high-performance liquid chromatography.

The experimental anti-AIDS glycerophosphatidic acid: nucleoside (sn-1/sn-2 diacylglycerol:dideoxynucleotide) drugs 3'-azido-3'-deoxythymidine monophosphate diglyceride (AZT-MP-DG) and 2',3'-dideoxycytidine monophosphate diglyceride (ddC-MP-DG) were isolated and purified by reversed-phase high-performance liquid chromatography (HPLC). The chromatographic separation was based on the glycerophospholipid moiety of the drugs and detection of the nucleoside component. The separations were optimized on method development columns packed with the stationary phase to be used in the micro-preparative column and monitored by a UV detector. Fractions were collected and analyzed for purity by analytical-scale HPLC and by thin-layer chromatography (TLC). The purity of the recovered drugs based on UV and light-scattering detection and on TLC was greater than 99%. The purified compounds were isolated for studies on structure confirmation, physical, biophysical and formulation properties and anti-HIV efficacy in culture.

Acquired Immunodeficiency Syndrome↗
PubMed1983

The role of the phosphatidate-inositide cycle in the action of steroidogenic agents.

Most steroidogenic agents have been found to provoke rapid changes in the metabolism of phospholipids in the phosphatidate-inositide cycle. These changes include: (a) de novo synthesis of phosphatidic acid and its derivatives, phosphatidylglycerol, mono- and polyphosphoinositides and diglyceride; and (b) phosphatidylinositol hydrolysis and consequent generation of diglyceride and phosphatidic acid. The de novo phosphatidate synthesis effect occurs in the action of all tested steroidogenic agents (ACTH, LH, angiotensin, K+, serotonin) and may be induced by either of the "second messengers", cAMP and Ca2+. The phosphatidylinositol hydrolysis effect(s) occurs only in the action of steroidogenic agents that operate via Ca2+ (angiotensin and K+) and may be important in Ca2+ mobilization. The de novo phospholipid effect correlates well with changes in steroidogenesis and, like the latter, requires Ca2+ and protein synthesis; from these and other results, it seems likely that this phospholipid effect plays an important role in the stimulation of steroidogenesis.

Adrenal Glands↗
PubMed1978

Arachidonic acid distribution in lipids of mammary glands and DMBA-induced tumors of rats.

In the phospholipid fractions, arachidonic acid represented a several fold higher percentage of fatty acids from DMBA-induced tumors and in mammary glands from midpregnant rats when compared to mammary glands from virgin rats. Arachidonic acid was not present in measurable quantities in the neutral lipid fractions of mammary glands from virgin rats. The arachidonic acid in the neutral lipid fraction of mammary glands from midpregnant rats was only detectable in the triglyceride-sterol ester fraction, but in that fraction less than 1% of the fatty acids were arachidonic acid. In the neutral lipids of the DMBA-induced tumors, it was of particular interest that a high proportion (19%) of the fatty acids in the diglyceride fraction consisted of arachidonic acid; no arachidonic acid was detected in the diglycerides of the normal tissues.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1981

Schistosoma mansoni: modulation of schistosomular lipid composition by serum.

Human serum and foetal calf serum have been compared in terms of their ability to modify the biochemical and immunological properties of the schistosomular surface. Artificially transformed schistosomula were incubated in the presence of serum for 24 h and then radioiodinated using the chloramine T method. With this method only lipids are labelled. Foetal calf serum produces a net loss of lipids from the schistosomula, particularly of mono- and diglycerides. Human serum however, promotes not only a loss of mono- and diglycerides, but also a substantial uptake of cholesterol and triglycerides. Schistosomula recovered from the lungs of mice could also be labelled and contained besides triglycerides, an increased amount of cholesterol esters. The modulation of surface lipids in worms cultured with human serum correlates with the observation that such schistosomula develop significantly greater protection against eosinophil-mediated cytotoxicity in vitro than do individuals incubated with foetal calf serum. On the other hand, schistosomula cultured in the presence of either human serum or foetal calf serum develop the same degree of protection against complement-dependent lethal antibody; this result indicates that resistance against complement-mediated damage may be independent of the uptake of cholesterol and/or triglycerides, and might involve only limited alterations in the surface configuration of the schistosomulum.

Animals↗
PubMed1993

Carcinogenicity study of the emulsifier TOSOM and the release agent TOS in Wistar rats.

Groups of 60 Wistar rats of each sex were fed diets containing 3, 6 or 12% of the margarine emulsifier TOSOM (thermally oxidized soybean oil interacted with mono- and diglycerides of fatty acids) for 2.5 yr. In addition, three groups of 60 rats of each sex were fed two products of the release agent TOS (thermally oxidized soybean oil) in dietary levels of 1.2% TOS(G) (TOS from Grindsted Product A/S, Denmark) and 0.3 and 1.2% TOS(N) (TOS from Nexus Aps, Denmark), respectively for 2.5 yr. 120 rats of each sex fed a diet containing mono- and diglycerides served as controls. The diets given to all groups were isocaloric. Clinical appearance, food consumption, body weight and weight gain, survival, haematology, and clinical chemistry parameters were examined. Gross and histopathological examinations, including neoplastic and non-neoplastic lesions, were performed on all groups. Time to occurrence of tumours was recorded. No substance-related effect, including carcinogenicity, was found.

Animals↗
PubMed1995

Analysis of dipalmitoyl phosphatidylcholine in amniotic fluid by enzymatic hydrolysis and high-performance thin-layer chromatography reflectance spectrodensitometry.

A novel test for the determination of dipalmitoyl phosphatidylcholine (DPPC) in amniotic fluid (AF) as free dipalmitoylglycerol (DPG), is described. Aliquots of amniotic fluid were hydrolyzed with Bacilus cereus phospholipase C, and the resulting diglycerides analyzed by AgNO3-modified high-performance thin-layer chromatography (HPTLC)-reflectance spectrodensitometry. This HPTLC system provided resolution of DPG and palmitoylpalmitoleoylglycerol (POG) from other 1,2-diglycerides and cholesterol. The turn-around analysis time for triplicate aliquots of amniotic fluid was 40 min. Recoveries ranged between 90 and 98%. In summary, this method provides a quantitative, specific, highly reproducible, and fast turn-around means of analysis of DPPC in amniotic fluid.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1989

Effect of bovine growth hormone on incorporation of [14C]acetate into lipids by co-cultures of bovine mammary, liver, and adipose tissue explants.

Incorporation of [14C]acetate into lipids was measured in 24 hr co-cultures of mammary, liver and adipose tissue from Holstein cows at 53, 210 and 318 d of lactation in the presence or absence of bovine growth hormone. Little (less than 1%) of the labeled lipids appeared in the media relative to that incorporated into the tissue. In mammary tissue, incorporation of [14C]acetate was highest into triglycerides (16,298 cpm/mg mammary tissue), followed by phospholipids (1,887 cpm), free fatty acids (1,252 cpm), diglycerides (708 cpm), free cholesterol (360 cpm) and monoglycerides (93 cpm). Bovine growth hormone did not increase incorporation of [14C]acetate when mammary or adipose tissue were incubated separately. However, in the presence of liver and adipose tissue, bovine growth hormone significantly increased the incorporation of [14C]acetate into triglycerides, diglycerides, free fatty acids and free cholesterol by mammary tissue. These results suggest that bovine growth hormone acts on mammary tissue indirectly through liver and adipose tissue to increase lipid synthesis. This mechanism may play a role in the action of bovine growth hormone in vivo to increase milk and milk fat production.

Acetates↗
PubMed1986

Arachidonic acid releasing systems in pig aorta endothelial cells.

Endothelial cells synthesize prostacyclin both from platelet-derived endoperoxides and from the arachidonic acid released from its intracellular stores. The mechanisms controlling this release does not appear to be mediated through phospholipid methylation but by means of phosphoinositide hydrolysis. As yet two possible mechanisms have so far been proposed to regulate arachidonic acid release in a number of cellular systems: phospholipase C-controlled phospholipase A2 activity or phospholipase C-diglyceride lipase system. The results presented here show that using phospholipases inhibitors is not a reliable strategy to study arachidonic acid release in cultures of endothelial cells. Our data also strongly suggest that the release of prostacyclin may be accounted in these cells for by a phospholipase C-diglyceride lipase system.

Animals↗