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PubMed2004

Phase behaviour and morphology of binary mixtures of DPPC with stearonitrile, stearic acid, and octadecanol at the air-water interface.

The behaviour of dipalmitoylphosphatidylcholine (DPPC), mixed with stearonitrile (SN), was investigated at the air-water interface by surface pressure-area (pi-A) measurements and by direct visualisation of monolayers by Brewster angle microscopy (BAM). The pi-A-X diagram of system DPPC/SN was compared with the corresponding diagrams of systems DPPC/stearic acid (SA) and DPPC/octadecanol (OD) at 20 degrees C. Monolayers of the three systems reach the closest packing of alkyl chains in the 0.4-0.6 range of XDPPC. Thermodynamic analysis indicates miscibility in the three binary systems with negative deviations from the ideal behaviour. Morphological features of system DPPC/SN change significantly with XDPPC and temperature in the range 10-30 degrees C. At 10 and 20 degrees C mixed monolayers form condensed states from low pi all over the composition range. At 30 degrees C, the liquid-expanded (LE)--liquid-condensed (LC) phase transition occurs at increasing pi with XDPPC. The shape and size of condensed domains change with XDPPC and pi. Contrarily to the behaviour of pure components, mixed monolayers of DPPC/SN exhibit orientational order in the 0.2-0.6 mol fraction range of DPPC. BAM observation confirmed the partial miscibility indicated by GE data in a limited range of compositions at 30 degrees C.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed2004

Design of vesicles of 1,2-di-O-acyl-3-O-(beta-D-sulfoquinovosyl)-glyceride bearing two stearic acids (beta-SQDG-C18), a novel immunosuppressive drug.

The immunosuppressive effects of synthetic sulfo-glycolipids in the class of sulfoquinovosyl-diacylglycerols (SQDG), including stereoisomers, were interesting in development of a promising clinical drug. Especially, 1,2-di-O-stearoyl-3-O-(6-deoxy-6-sulfo-beta-D-glucopyranosyl)-sn-glycerol (beta-SQDG-C18) was thought to be a valuable candidate because of the preliminary observations of its high inhibitory activities in spite of low toxicities. The problem of using this material is to find an applicable way avoiding its low solubility in water. The vesicle formation of beta-SQDG-C18 is advantageous to i.v. administration in its chemico-structural character. With preparation in water, beta-SQDG-C18 was hard to form vesicles, because its hydrophilicity was strong. We examined the suitable parameter of the vesicle forming condition. It was possible to take a balance between the hydrophilicity and the hydrophobicity of the beta-SQDG-C18 molecule to be optimized to form vesicles in 150 mM PBS. In addition, we demonstrated the strong immunosuppressive activity of beta-SQDG-C18 vesicles. This is the first report of the preparation method of beta-SQDG-C18 vesicles, which should facilitate in vitro and in vivo application.

Drug Stability↗
PubMed1993

Destruction of stearic acid nitroxyl radicals mediated by photoexcited merocyanine 540 in liposomal and micellar systems.

Fatty acid spin labels have been included into liposomes and micelles, in order to study the photochemical behavior of merocyanine 540 toward nitroxyl radicals situated at various depths in the bilayer or the surfactant layer. Visible illumination of the dye, either free in ethanol or bound to liposomes or micelles, leads to the reduction of the electron spin resonance signal of the label. The efficiency of the interaction between merocyanine 540 and spin labels depends on the depth at which the nitroxyl moiety is localized in the micelle or vesicle. Fluorescence measurements indicate that the first excited singlet state of merocyanine 540 is not directly implicated in the reaction mechanism. Flash photolysis experiments conducted in aqueous solutions of hexadecyltrimethylammonium bromide micelles show that the presence of nitroxyl radical decreases the rate constant of triplet decay in a concentration-dependent fashion. The corresponding quenching rate constant (kq) is determined for the different spin labels. The kq values and the reduction rates of ESR signal show the same dependence on the localization of the nitroxyl moiety in the micelles.

Cetrimonium↗
PubMed1994

Binding of (+)- and (-)-isomers and racemate of etomoxir to human serum albumin and effect of stearic acid and stanozolol.

Binding of (+)- and (-)-isomers and the racemate of sodium 2[6-(4-chlorophenoxy)-hexyl]-oxiran-2-carboxylate dihydrat (etomoxir) to the human serum albumin (HSA) was studied by the gel filtration method. The experimental results are presented graphically using the method of Scatchard. Measurements revealed the following data on the binding: (a) for either of the isomers there are two independent and nonequivalent classes of binding sites on the HSA molecule; (b) the binding constants calculated for both isomers were of the same order of magnitude (K1/n approximately 20 x 10(5) L.mol-1 for the concentration range 3.48-4.0 x 10(-5) mol.L-1, and K2/n approximately 2 x 10(5) L.mol-1 for the concentration range 4.28-10 x 10(-5) mol.L-1, for the high and low affinity binding sites, respectively); (c) statistically significant difference (p < or = 0.05) between the low affinity binding constant estimated for the (+)-isomer K2 = 1.9 +/- 0.1 x 10(5) L.mol-1) compared with the constants evaluated for the (-)-isomer and racemic etomoxir (2.6 +/- 0.1 and 2.9 +/- 0.2 x 10(5) L.mol-1, respectively); and (d) both isomers are bound into a high extent to the HSA molecule (i.e., at a ligand concentration of 3.48 x 10(-5) mol.L-1, the percent of binding was approximately 95% for the compound tested. When plotting the percent binding (% Cb) against the total concentration (Ctot), a statistically significant difference (p < or = 0.05) was obtained between the slope of the straight line for the (+)-isomer and those for other two compounds.(ABSTRACT TRUNCATED AT 250 WORDS)

Binding, Competitive↗
PubMed1984

Modulation of rabbit neutrophil aggregation and degranulation by free fatty acids.

We have examined the effects of free fatty acids on the unstimulated and N-formyl-methionyl-leucyl-phenylalanine (f-Met-Leu-Phe) stimulated rabbit neutrophil aggregation and degranulation. As previously reported, arachidonic acid was found to induce by itself an aggregatory response, and in the presence of cytochalasin B, a degranulation response from the neutrophils. The aggregatory property, but not the secretory activity of arachidonic acid, was shared by oleic acid, linoleic acid, linolenic acid, linoelaidic acid, and lauric acid but not by elaidic acid, caproic acid, stearic acid, and arachidic acid. In addition, several free fatty acids (oleic acid, linoleic acid, linolenic acid, arachidonic acid, and linoelaidic acid) were found to inhibit the aggregatory and secretory responses of the neutrophils to the addition of f-Met-Leu-Phe. Caproic acid and lauric acid were found to stimulate to a small extent the aggregatory response of the neutrophils to f-Met-Leu-Phe and to leave unaffected their secretory response. Elaidic acid, stearic acid, and arachidic acid, on the other hand, left both stimulated responses unaffected. These results demonstrate that at least two neutrophil functions can be modulated (both positively and negatively) by free fatty acids.

Animals↗
PubMed2003

Inhibition by arachidonic acid and other fatty acids of dopamine uptake at the human dopamine transporter.

It is known that arachidonic acid, in addition to promoting release of dopamine, can inhibit its transport. The present study provides preliminary information on structure-activity relationships for uptake inhibition by rotating disk voltammetry in human embryonic kidney-293 cells expressing the human dopamine transporter. Except for anandamide, all other fatty acids studied at a pretreatment concentration of 80 microM caused significant reductions in Vmax but not Km. Increasing saturation of the hydrocarbon tails (partial saturation: oleic acid, linoleic acid; full saturation: arachidic acid, stearic acid, stearic acid ethyl ester) removed inhibitory activity incrementally, suggesting a role for cis-unsaturation (folding/bending of hydrocarbon tails). The relative lack of effect of 5,8,11,14-eicosatetraynoic acid also supports the idea that less linear structures are less inhibitory on dopamine uptake. Esterification of the free carboxylic group (arachidonic acid ethyl ester) prevented most of the inhibitory activity, arguing against mere membrane lipid disruption. Finally, the endogenous cannabinoid anandamide greatly reduced uptake Vmax accompanied by a small decrease in Km, a potentially important effect on dopaminergic neurotransmission.

Arachidonic Acid↗
PubMed2004

Differential regulation by fatty acids of protein histidine phosphorylation in rat pancreatic islets.

Long-chain fatty acids (e.g. arachidonic acid) have been implicated in physiological control of insulin secretion. We previously reported histidine phosphorylation of at least two islet proteins (e.g., NDP kinase and the beta subunit of trimeric G-proteins), and suggested that such a signalling step may have regulatory roles in beta cell signal transduction, specifically at the level of G-protein activation. Since our earlier findings also indicated potential regulation by long-chain fatty acids of islet G-proteins, we undertook the current study to verify putative regulation, by fatty acids, of protein histidine phosphorylation of NDP kinase and Gbeta subunit in normal rat islets. The phosphoenzyme formation of NDP kinase was stimulated by various fatty acids in the following rank order: linoleic acid > arachidonic acid > oleic acid > palmitic acid = stearic acid = control. Furthermore, the catalytic activity of NDP kinase was stimulated by these fatty acids in the rank order of: oleic acid > arachidonic acid > linoleic acid > palmitic acid = stearic acid = control. Arachidonic acid methyl ester, an inactive analog of arachidonic acid, did not significantly affect either the phosphoenzyme formation or the catalytic activity of NDP kinase. Interestingly, arachidonic acid exerted dual effects on the histidine phosphorylation of beta subunit; it significantly stimulated the phosphorylation at 33 microM beyond which it was inhibitory. Together, these findings identify additional loci (e.g., NDP kinase and Gbeta subunit) at which unsaturated, but not saturated, fatty acids could exert their intracellular effects leading to exocytotic secretion of insulin.

Animals↗
PubMed2006

Fatty acids, inhibitors for the DNA binding of c-Myc/Max dimer, suppress proliferation and induce apoptosis of differentiated HL-60 human leukemia cell.

c-Myc is instrumental in the progression of Burkitt's lymphoma including HL-60 human leukemia cells. We tested fatty acids for their inhibitory effect on the DNA binding of c-Myc/Max dimeric proteins of human origin, prepared as recombinant proteins encompassing DNA binding (basic) and dimerization (HLHZip) domain, and found that those suppress proliferation and induce apoptosis of DMSO-differentiated HL-60 cells. The analyzed IC50 values of myristic acid, stearic acid, gamma-linolenic acid, linoleic acid, linolenic acid and arachidonic acid by EMSA were 97(+/-3), 2.2(+/-1.2), 55(+/-5), 32(+/-2), 62(+/-12), 22(+/-2)microM for DNA binding of recombinant c-Myc/Max, respectively. According to the results shown by XTT assay, their influence on proliferation was quite different from the rank order of IC50. Whereas the degree of influence of the unsaturated fatty acids on the proliferation of DMSO-differentiated HL-60 cells was similar, the influence of saturated fatty acids, stearic acid in particular, was very weak at same concentrations. In addition, we confirmed that these fatty acids have no influence on the expression of c-Myc in DMSO-differentiated HL-60 cells. Our experiments demonstrated that the inhibitors for the DNA binding of c-Myc/Max contribute to the downregulation of Myc-dependent proliferation and to the inducement of apoptosis, and serve as an exploration of potent new inhibitors.

Apoptosis↗
PubMed1975

Dietary effects of the esters of butyric, caproic, caprylic, capric, lauric, myristic, palmitic, and stearic acids on food intake, weight gain, plasma glucose, and tissue lipid in the male white rat.

Eight saturated fatty acid esters were fed to male white rats for 30 days in a 1/81 fractional factorial experiment in which diets contained 12-38% of their total energy as lipid. Marked increases in food intake, feed efficiency, and weight gain were achieved when lipid provided 36% of diet energy, and when that lipid was more than half caproate, caprate, myristate, and/or stearate. Caproate was the only saturated fatty acid to increase plasma glucose levels. The feeding of stearate or caprylate decreased plasma and liver cholesterol. Caprate increased liver fat. The short-chain fatty acids (butyrate to myristate) increased the concentration of fat in the carcass.

Animal Nutritional Physiological Phenomena↗
PubMed1994

A Mutant of Arabidopsis with Increased Levels of Stearic Acid.

A mutation at the fab2 locus of Arabidopsis caused increased levels of stearate in leaves. The increase in leaf stearate in fab2 varied developmentally, and the largest increase occurred in young leaves, where stearate accounted for almost 20% of total leaf fatty acids. The fatty acid composition of leaf lipids isolated from the fab2 mutant showed increased stearate in all the major glycerolipids of both the chloroplast and extrachloroplast membranes. Although the stearate content was increased, the fab2 mutant still contained abundant amounts of 18:1, 18:2, and 18:3 fatty acids. These results are consistent with the expectations for a mutation partially affecting the action of the stromal stearoyl-acyl carrier protein desaturase. Positional analysis indicated that the extra 18:0 is excluded with high specificity from the sn-2 position of both chloroplast and extrachloroplast glycerolipids. Although stearate content was increased in all the major leaf membrane lipids, the amount of increase varied considerably among the different lipids, from a high of 25% of fatty acids in phosphatidylcholine to a low of 2.9% of fatty acids in monogalactosyldiacylglycerol.

Journal Article↗
PubMed1989

The effect of phospholipase A2 and cyclooxygenase inhibition on free fatty acids in the brain.

The levels of NEFA (oleic acid, palmitic acid, stearic acid, arachidonic acid) were studied in the brain cortex, hypothalamus and the brain stem of rat brain. Inhibition of phospholipase A2 by Delagil (Mepacrinium dichloratum CsL 3) decreased statistically significantly the values of arachidonic aci (-5.5%) in the brain cortex and the values of stearic acid (-11.2%) in the hypothalamua. The cyclooxygenase inhibition by aspirin led to a significant increase of palmitic acid (+12.7%), oleic acid (+18.7%) and arachidonic acid (+14.3%) in the hypothalamus. Total NEFA increased by 11.2%. A significant increase of palmitic acid (+26.9%), arachidonic acid (+33.9%) and of total NEFA (+22.9%) was evidenced in the brain stem. Delagil administered in combination with acetylsalicylic acid suppressed the NEFA increase observed after the application of acetylsalicylic acid alone. A statistically significant decrease was found in stearic acid (-12.6%) in the hypothalamus and in all studied NEFA in the brain stem (palmitic acid, -14.2% stearic acid -11.7%, oleic acid -3.8%, arachidonic acid -16.6% and total NEFA -11.8%).

Animals↗
PubMed2001

Rhamnolipid production by Pseudomonas aeruginosa under denitrification: effects of limiting nutrients and carbon substrates.

Being biosurfactants, rhamnolipids create severe foaming when produced in aerobic Pseudomonas aeruginosa fermentation. The necessary reduction of aeration causes oxygen limitation and restricts cell and product concentrations. In this study, we evaluate the new strategy of rhamnolipid production under denitrification conditions. Because hydrocarbons used in earlier aerobic fermentations were not metabolizable in the absence of oxygen, other potential C substrates were examined, including palmitic acid, stearic acid, oleic acid, linoleic acid, glycerol, vegetable oil, and glucose. All were found able to support cell growth under anaerobic denitrification. The growth on the two solid substrates (palmitic acid and stearic acid) was slower but could be enhanced substantially by initial addition of rhamnolipids (0.06 g/L). The effects of different limiting nutrients (N, P, S, Mg, Ca, and Fe) were also investigated. The commonly used N limitation could not be adopted in the denitrifying fermentation because the nitrate added for anaerobic respiration would also be assimilated for growth. P limitation was most effective, giving four- to fivefold higher specific productivity than the conventional N limitation. S limitation was comparable to N limitation; Mg limitation was much poorer. Ca and Fe were ineffective in limiting cell growth. The new strategy was further evaluated in a P-limited fermentation with palmitic acid as the substrate. The fermentation was first carried out under denitrification and later switched to aerobic condition. The specific productivity under denitrification was found to be about one-third that of the aerobic condition. The denitrification process was, however, free of foaming or respiratory limitation. Much higher cell concentrations may be employed to attain higher volumetric productivity and product concentrations, for more economical product recovery and/or purification.

Aerobiosis↗
PubMed1987

Chemical identification of lipid components in the membranous form of rat liver alkaline phosphatase.

Membranous and soluble forms of rat liver alkaline phosphatase were selectively prepared by extracting microsomes with n-butanol at pH 8.5 and 5.5, respectively, and purified in homogeneous forms by the method previously established (Miki et al. (1986) Eur. J. Biochem. 160, 41-48). When subjected to polyacrylamide gel electrophoresis, the two forms migrated to the same position in the presence of sodium dodecyl sulfate, while the membranous form remained at the top of gels in the absence of the detergent. Treatment of the membranous form with phosphatidylinositol-specific phospholipase C resulted in its conversion to a soluble form with the same electrophoretic mobility even in the absence of the detergent as that of the soluble form extracted at pH 5.5. Automated Edman degradation analysis showed that the two forms have the same N-terminal amino acid sequence up to the 30th residue determined. Chemical analyses of hydrolysates of the two forms by gas-liquid chromatography demonstrated that the membranous form contains palmitic acid, stearic acid, and inositol, while the soluble form contains inositol but is devoid of the fatty acids. Taken together, these results suggest that rat liver alkaline phosphatase is covalently attached to phosphatidylinositol acylated with palmitic acid and stearic acid, which functions as the membrane-anchoring domain of the enzyme molecule.

Alkaline Phosphatase↗
PubMed2004

Selectivity and stability of organic films at the air-aqueous interface.

It has recently been determined that organic compounds represent a significant percentage of the composition of certain atmospheric aerosols. Amphiphilic organics, such as fatty acids and alcohols, partition to the interface of aqueous aerosols. In this way, the air-aqueous interface of an aerosol has the ability to act as both a concentrator and a selector of organic surfactants. Isotherms of nonanoic acid, stearic acid, 1-octadecanol, and a binary of mixture of nonanoic and stearic acids were used to infer the packing ability and molecular orientation of the surfactants at the interface. The selectivity of the air-aqueous interface was studied by monitoring the composition of binary organic films as a function of film exposure time. The films were formed, aged, and collected with the use of a Langmuir trough. The composition of the aged film was determined via GC-MS. Surfactants with differing carbon number and chemical functionalities were studied. These included stearic acid, lauric acid, 1-octadecanol, and octadecane. The stability and packing ability of stearic and lauric acid films were examined as a function of subphase pH. The relevance of these findings as they relate to the composition and structure of organic aerosols as well as recent surface-sensitive aerosol field measurements is discussed.

Journal Article↗
PubMedDate not supplied

Characterisation of castor oil by on-line and off-line non-aqueous reverse-phase high-performance liquid chromatography-mass spectrometry (APCI and UV/MALDI).

A non-aqueous reverse-phase HPLC method, based on two columns in series, has been used to separate the major triacylglycerols (TAGs) from commercial castor oil and to perform either on-line negative ion atmospheric pressure chemical ionisation (APCI), or off-line positive ion matrix-assisted laser desorption ionisation (MALDI)/MS. The resulting Mass Spectra showed chloride-attached TAG molecules [M + CI]- in the case of negative-ion APCI, and sodium-attached TAG molecules [M + Na]+ in the case of positive-ion MALDI. For MALDI time-of-flight (TOF)/MS, a liquid binary matrix system consisting of sodium ferrocyanide and glycerol was applied, resulting in excellent TAG sensitivity, which was necessary for the determination of trace amounts of TAGs in castor oil. Both techniques allowed unambiguous molecular mass determination of the intact TAG molecules with no thermal degradation. Furthermore, seamless post source decay (PSD) fragment ion analysis by means of a curved field reflector TOF mass spectrometer allowed the determination of the fatty acid composition of each individual TAG. Castor oil contained eight different TAGs which were successfully determined by both APCI and MALDI techniques. In each TAG, at least two units of 12-hydroxy-9-octadecenoic acid (ricinoleic acid) were present. The following fatty acids were determined by seamless PSD fragment ion analysis and APCI/MALDI molecular mass determination as TAG substructures: ricinoleic acid, palmitic acid, stearic acid, oleic acid, linoleic acid, linolenic acid, dihydroxy stearic acid and eicosenoic acid. Triricinolein was the dominating TAG.

Castor Oil↗
PubMed1990

Dietary influences on serum lipids and lipoproteins.

Substantial data are available to indicate that the diet influences serum levels of cholesterol and lipoproteins. These data are derived from studies in laboratory animals, from epidemiologic studies, and from human investigations. Most research has focused on effects of diet on serum total cholesterol concentrations. In recent years, however, attention has shifted to individual lipoproteins, i.e., low density lipoproteins (LDL), high density lipoproteins (HDL), and very low density lipoproteins (VLDL). Three nutritional factors have been identified that raise serum LDL levels; these are saturated fatty acids, cholesterol itself, and excess caloric intake leading to obesity. The major cholesterol-raising saturated fatty acid in the diet is palmitic acid. Several nutrients can be substituted for saturated fatty acids to produce a reduction in LDL-cholesterol levels. These are polyunsaturated fatty acids, monounsaturated fatty acids, carbohydrates, and even one saturated fatty acid, stearic acid. The latter appears to be converted rapidly into a monounsaturated fatty acid in the body. Any of these nutrients can be used for replacement of cholesterol-raising saturated fatty acids in the diet. However, their relative effects on other metabolic processes remain to be determined fully. At present it appears that carbohydrates and monounsaturated fatty acids represent the preferred replacements for saturated fatty acids, although modest increases in polyunsaturated fatty acids and stearic acid, at the expense of cholesterol-raising saturates, probably are safe and may provide for greater variety in the diet.

Animals↗