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PubMed1985

Intramembrane fluidity increases when the cyclohexyl ring of retinal binds to rod outer-segment membranes.

The spin-label 5-4',4'-dimethyloxazolidinyl-N-oxy stearate (5-doxyl-stearate) exists in a viscous environment when it is incorporated into bleached rod outer segment membranes (ROSM). Addition of the cyclohexyl ring moiety of retinal to ROSM produced a large increase in intramembrane fluidity. A decrease in both the order parameter S (from 0.5 to 0.14) and the rotational correlation time (from 4.0 to 2.0 nsec) gives an estimate of the magnitude of change. Other ring analogs produced similar fluidity changes. The extent of their action depended on their structural similarity to the cyclohexyl of retinal. The pH range in which the cyclohexyl ring produced the increase in ROSM fluidity was 6.8-9.5.

Animals↗
PubMed1979

[Biochemistry of the developmental cycle of Triatoma infestans (Vinchuca). 2. Biosynthesis of fatty acids].

The biosynthesis of fatty acids in Triatoma infestans was studied in all the nymph stages and adult insects by feeding experiments with 1-14C acetate. In other experiments labeled acetate, 1-14C palmitate or 1-14C stearate were injected in the abdomen. In another group of experiments the abdominal non intestinal tissue of adult insects was homogenized and the supernatants of 10 000 X g and 105 000 X g were incubated with 1-14C acetyl-CoA. The incorporation of the labeling in the fatty acids was studiel by gas liquid radiochromatography. It was proved that the supernatant of 105 000 X g possessed a fatty acid synthetase able to synthesize de novo the saturated fatty acids of 10 to 18 carbons with a maximal yield in the myristic and palmitic acids. The fatty acid synthetase was active from Nymph L stage. The supernatant of 10 000 X g was able to synthesize fatty acids tentatively identified as eicosenoic and eicosadienoic acids. The T. infestans has also an enzyme that elongated palmitate to stearate. In the fraction precipitable between 10 000 X g and 105 000 X g was apparently present a desaturating enzyme that converts saturated to monoethylenic acids. The enzyme was apparently only active from Nymph II stage.

Acetates↗
PubMed1967

Studies in the biosynthesis of hepatic and biliary lecithins.

Male rats with biliary cannulae were injected with linoleate-1-(14)C, stearate-1-(14)C, palmitate-9-10-(3)H, phosphate-(32)P, l-methionine-methyl-(14)C, and choline-methyl-(3)H in various combinations and the incorporation of these isotopes into the phospholipids of liver, bile, and plasma was determined for 1-4 hr. The results summarized below favor the view (a) that exchange of saturated fatty acids plays a role in the formation of lecithins; (b) that the unsaturated fatty acids do not undergo significant exchange and determine the pathway of biosynthesis of lecithins; and (c) that there is either more than one pool of CDP-choline in liver or a pathway of biosynthesis of lecithin from choline not involving CDP-choline as an intermediate. Linoleoyl lecithin of liver attained higher specific activity with respect to phosphate-(32)P and choline-methyl-(3)H than did arachidonoyl lecithin. Lecithin in bile attained higher specific activities with respect to phosphate-(32)P, choline-methyl-(3)H, and linoleate-1-(14)C than the corresponding hepatic lecithins. Stearate-1-(14)C and palmitate-9-10-(3)H attained highest specific activities in the hepatic lecithin fraction rich in arachidonic acid. The specific activity of hepatic phosphatidyl ethanolamine was lower with respect to saturated fatty acids, but much higher with respect to (32)P than any lecithin. The ratio of specific activity of (3)H in methyl groups from choline to (14)C in methyl groups from methionine in hepatic sphingomyelin was lower than in hepatic linoleoyl lecithin.

Animals↗
PubMed1982

Effect of lead on physical state of erythrocytes and model membranes.

Lead has an high affinity for erythrocyte and influences the membrane bound enzymes activities but its interactions with biological membranes is still unclear. We have investigated the effect of lead as free ion on physical state of erythrocytes and liposomes by Electron Spin Resonance (ESR) using two spin labels 5-doxyl-stearate (5-NS) and 16-doxyl-stearate (16-NS) and by DPH (1,6-diphenyl-1,3,5-hexatriene) fluorescence polarization analysis. Lead induces decrease of fluidity in natural membrane which is more evident in membrane hydrophobic core; the effect is not correlated with lead concentration. Lead ion interacts with negative charged liposomes inducing an increase of their microviscosity.

Cardiolipins↗
PubMed1984

A study of the activity of soft soaps prepared from a homologous series of saturated fatty acids against cells of Escherichia coli NCTC 9001.

Soaps were prepared by direct neutralization of a homologous series of fatty acids with potassium hydroxide, the acids used being lauric, myristic palmitic and stearic acids. The antibacterial activity of these soaps were studied using Escherichia coli as the test organism. From the various phenomena examined it can be concluded that all the soaps used had a measure of antibacterial activity, the order of this activity being myristate, laurate, palmitate, and stearate. The antibacterial activity of both the palmitate and the stearate can only be described as marginal.

Acriflavine↗
PubMed1984

[The ratio of free and fixed interlamellar water as quality criteria for O/W creams].

O/W creams with crystalline gel structures are supposed to be four phase systems. Their dominant structural elements are the hydrophilic and lipophilic gel phases. The hydrophilic gel phases have - depending on the hydrophilic character of their polar groups - a very strong swelling capacity. Further, a dynamic equilibrium is maintained between the water interlamellarly inserted into the hydrophilic gel phase and the bulk water phase. The latter is mainly fixed mechanically by the hydrophilic gel phase. The lipophilic gel phases, however, which immobilize the dispersed phase, have no or only an extremely weak swelling capacity. By means of thermogravimetry (TG) a quantitative differentiation between water interlamellarly fixed in the hydrophilic gel phase and bulk water is possible. Using dynamic TG, the curves of water release and the results obtained are discussed. In the water-containing hydrophilic ointment DAB 8 and in the non-ionic hydrophilic ointment DAC the fractions of interlamellarly fixed water are substantially higher than those of the bulk water. In the investigated stearate creams, however, the fraction of the bulk water is much higher than the fraction of interlamellarly fixed water. Consequently the water release from these stearate creams is higher than that of the other O/W creams mentioned above. It is concluded that the ratio of interlamellarly fixed water and bulk water is an important criterion for the properties of such O/W creams and that TG can be suitably applied not only as in process control during product manufacturing but also as a useful tool in the development of O/W creams with a controlled water release.

Chemical Phenomena↗
PubMed1983

Metabolism of C14 mevalonate by adult and fetal arteries.

The metabolism of mevalonate by the arterial wall was evaluated in fetal and adult maternal arteries of the New Zealand white rabbit. Freshly minced tissue from umbilical arteries, fetal aortas and adult maternal aortas was incubated in oxygenated Krebs Henseleit bicarbonate buffer at 37 degrees C in the presence of 5-14C-mevalonate or 5-14C-3-hydroxy-3-methylglutaryl-Coenzyme A (HMG CoA). After incubation, the arterial tissue lipids were extracted and total cholesterol and free fatty acids were purified by thin layer chromatography and assayed for 14C by liquid scintillation spectrometry and analyzed chemically. The conversion of labeled HMG CoA or mevalonate to cholesterol in fetal aorta was 15 fold greater than in maternal aorta and 5-10 fold greater than in fetal umbilical artery. In addition some 14C from HMG CoA became incorporated into palmitate, stearate and oleate while 14C from mevalonate appeared in palmitate and stearate in trace amounts. Similarly, conversion of label from both precursors to 14CO2 was greatest in fetal aorta followed by umbilical artery and maternal aorta of the term pregnant rabbit. Of particular interest was the observation of enhanced (3.5 fold) conversion of label from mevalonate to 14CO2 by maternal aortas at mid-gestation compared to aortas of late-term gestation. These results are consistent with the explanation that while mevalonate clearly serves as a precursor for cholesterol synthesis in arterial tissue, a finite degree of exclusion from the main stream sterol pathway also occurs. This "shunt" pathway may involve oxidation directly to CO2 or indirectly by way of fatty acids. The level of activity through this exclusion pathway in arterial tissue appears to be under physiologic control during pregnancy since a 3.5 fold increase in conversion to 14CO2 occurred in aortas obtained in midgestation compared to those obtained at term gestation.

Acyl Coenzyme A↗
PubMed1983

Formation of methylamines from ingested choline and lecithin.

Humans ingest substantial amounts of choline and lecithin as part of common foods. Physicians have recently begun administering large doses of these compounds to individuals with neurological diseases. A significant fraction of ingested choline is destroyed by enzymes within gut bacteria, forming trimethylamine (TMA), dimethylamine (DMA) and monomethylamine (MMA). Some of these methylamines are eventually excreted into the urine, presumably after being absorbed and carried to the kidneys via the bloodstream. The methylamines formed after choline is eaten could be substrates for the formation of nitrosamines, which have marked carcinogenic activity. Twenty-seven millimoles of choline chloride, choline stearate or lecithin were administered to healthy human subjects. It was found that these treatments markedly increased the urinary excretion of TMA, DMA and MMA, with choline chloride having the greatest effect. Rats were treated with 2 mmol/kg b.wt. of choline chloride or lecithin, and it was found that these treatments significantly increased urinary TMA excretion and did not alter DMA or MMA excretion. Our choline chloride preparation contained no MMA, DMA or TMA; however, it was found that our choline stearate and all the commercially available lecithins tested were contaminated with methylamines. Prior removal of methylamines from our lecithin preparation minimized the effect of oral administration of this compound on methylamine excretion in urine of rats and humans.

Administration, Oral↗
PubMed1982

In vivo acylation of rat brain myelin proteolipid protein.

Examination of brain myelin proteins by sodium dodecyl sulfate-gel electrophoresis followed by fluorography clearly showed that both proteolipid protein (PLP) and DM-20 were acylated 24 h after the intracerebral injection of 30-day-old rats with [3H]palmitic acid. The radioactivity associated with PLP remained after purification, re-electrophoresis, and fluorography. Most of the radioactivity associated with PLP was removed when the gels were treated with hydroxylamine and then fluorographed, indicating that fatty acids were bound to PLP by ester linkage. Cleavage of purified PLP with methanolic sodium hydroxide readily released almost all protein-bound radioactivity. Thin layer chromatography of this material on both silver nitrate and reverse-phase plates provided evidence that most of the radioactivity co-migrated with methyl palmitate (77%) and methyl stearate (19%); however, some radioactivity was associated with methyl oleate (4%). Gas-liquid chromatography of the fatty acids associated with PLP distinctly revealed the presence of methyl palmitate and a detectable peak of methyl stearate.

Acylation↗
PubMed1981

Influence of dietary fatty acids on the incidence of mammary tumors in the C3H mouse.

Statistical techniques have been used to establish the extent to which the incidence of spontaneous mammary tumors in C3H mice could be associated with the levels of individual fatty acids in their diets. Eleven different fats and oils and nine mixtures of these fats and oils were selected so that the levels of the nine major fatty acids varied over a reasonable range and were not highly correlated with one another. Tumor incidence was observed in mice raised on diets containing 10% of these different fats. Multiple regressions have been calculated, expressing tumor incidence or time to tumor as a function of the levels of nine fatty acids, four saturated and five unsaturated, of the dietary lipids. Increased tumor incidence and decreased time to tumor were observed when increasing levels of linoleate (18:2) replaced the eight other fatty acids in the diet while the other polyunsaturated fatty acid, linolenate (18: 3), had little effect on tumor incidence. Four saturated fatty acids, laureate (12:0), myristate (14:0), palmitate (16:0), and stearate (18:0), were studied, with only the latter showing a significant effect. Increasing levels of stearate were associated with decreased tumor incidence and increased time to tumor. There was also a suggestion that erucic acid (22:1) reduced tumor incidence, but oleic acid (19:1) produced no significant effect.

Adenocarcinoma↗
PubMed1981

The adjuvant activity of fatty acid esters. The role of acyl chain length and degree of saturation.

Water-in-oil emulsions of metabolizable fatty acid esters, with the non-toxic surfactant Pluronic L122 as emulsifying agent, potentiated the humoral response to bovine serum albumin and staphylococcal toxoid in the mouse. Adjuvant activity was increased by changing the chemical nature of the esters as follows: (i) using a series of ethyl esters, adjuvant activity appeared when the acyl chain length of the fatty acid component was 16 or greater; (ii) isobutyl and isopropyl esters of palmitic acid (C16:0) were superior to ethyl; (iii) the ethyl esters of oleic (C18:1) and linoleic (C18:2) acids were better than stearic (C18:0). Since emulsions prepared with longer chain saturated esters are very viscous or solid at room temperature, and unsaturated esters are chemically reactive, emulsions were prepared with differing proportions of ethyl caprate (C10:0) and butyl stearate. At a ratio of 9:1 the emulsions possessed the low viscosity of ethyl caprate, but gained the adjuvant activity of butyl stearate. 125I-labelled BSA was retained in the footpad to a significantly greater extent than with a caprate emulsion, but reasons are given for believing that slow release of antigen is not the only mechanism of adjuvant activity. The ester emulsions caused more acute but less chronic local inflammation (footpad swelling) than Freund's incomplete adjuvant.

Adjuvants, Immunologic↗
PubMed1980

Identification of fatty acid esters of pregnenolone and allopregnanolone from bovine corpora lutea.

The lipoidal derivatives of steroids present in bovine corpora lutea have been identified and quantified. Nonpolar steroid derivatives were extracted from the tissue with a mixture of chloroform and methanol. The extract was subjected to column and high performance liquid chromatography in order to remove phospholipids, cholesterol, triglycerides, cholesteryl esters, and unesterified steroids. A portion of the purified nonpolar material was subjected to methanolysis. By gas-liquid chromatographic analysis, the products were shown to consist of the steroids 3 beta-hydroxy-5 alpha-pregnan-20-one (80%) and pregnenolone (20%), and the methyl esters of palmitic (34%), stearic (27%), oleic (22%), linoleic (7%), arachidonic (7%), palmitoleic (3%), and eicosatrienoic (1%) acids. Mass spectrometric analysis of the intact lipoidal derivatives and of their methoximes confirmed the presence of seven esters of allopregnanolone and pregnenolone: allopregnanolone palmitate, pregnenolone palmitate, allopregnanolone stearate, allopregnanolone oleate, allopregnanolone linoleate, allopregnanolone eicosatrienoate, and pregnenolone arachidonate. The mass spectral data suggested that four other esters were also present: pregnenolone stearate, pregnenolone oleate, pregnenolone linoleate, and allopregnanolone arachidonate.

Animals↗
PubMed1980

Lipid dynamics and lipid-protein interactions in rat hepatocyte plasma membranes.

Rat hepatocyte plasma membranes were isolated and examined by differential scanning calorimetry and by steady state fluorescence polarization of 1,6-diphenyl-1,3,5-hexatriene, 12-anthroyl stearate, and 2-anthroyl stearate. Calorimetry of the intact membranes revealed a reversible lipid thermotropic transition with lower and upper critical temperatures of 18 degrees and 31 degrees C, respectively. The transition was also observed in lipid extracts of the membrane, both dried and rehydrated. The transition enthalpies estimated for intact membranes, dried membrane lipids, and rehydrated lipids, respectively, were approximately 0.3, 1.2 to 1.4, and 0.5 to 0.7 cal/g of lipid. The transition observed in the native membranes is broad and of low enthalpy, owing in part to the relatively high cholesterol content and to protein-lipid interactions. Fluorescence polarization studies detect the lower critical temperature of the transition in the membranes and in sonicated dispersions of the membrane lipid. Arrhenius studies of membrane 5'-nucleotidase and alkaline phosphatase give two-slope plots with breakpoints, respectively, of approximately 17 degrees and 26 degrees C. These break points and others reported for a number of hepatocyte membrane protein activities cluster uniformly at either the lower or the upper critical temperature of the lipid transition observed by differential scanning calorimetry.

Animals↗
PubMed1981

The fatty acid composition of phosphatidylinositol from thrombin-stimulated human platelets.

The level of phosphatidylinositol (PI) in human platelets falls abruptly when they are stimulated with thrombin and then returns to baseline within 15 min. PI is enriched in arachidonate and our recently proposed pathway for arachidonate release (Bell, R. L., Kennerly, D. A., Stanford, N., and Majerus, P. W. (1979) Proc. Natl. Acad. Sci. U. S. A. 76, 3238-3241) provides a link between the unique fatty acid composition of PI and the increased turnover of PI seen in many secretory tissues when they are stimulated. We measured the fatty acid composition of PI at time points following stimulation with thrombin as a means of defining the route of PI resynthesis which occurs, and the mechanism for the arachidonate enrichment. In resting platelets, the fatty acid content (per cent of total fatty acid contributed by each) of PI is: palmitate, 5.1; stearate, 39.9; oleate, 8.6; linoleate, 5.6; and arachidonate, 40.8. At 30 s after thrombin treatment, when the mass of PI has fallen from 18.7 +/- 2.3 to 12.5 +/- 2.4 nmol/10(9) platelets, there are no significant changes in per cent fatty acid composition. However, at 8 min, when PI has returned to 16.8 +/- 2.9 nmol/10(9), the per cent fatty acid composition is: palmitate, 7.8 (p > 0.05); stearate, 34.0 (p < 0.005); oleate, 10.7 (p < 0.05); linoleate, 16.1 (p < 0.001); and arachidonate, 31.3 (p < 0.05). The altered fatty acid composition excludes the "Pi cycle" as the mechanism for resynthesis as it would result in an unchanged pattern. The evidence suggests that PI is synthesized without a specific fatty acid composition, and then undergoes a deacylation-reacylation cycle to result in the unique 1-stearyl-2-arachidonyl pattern.

Blood Platelets↗
PubMed1994

Possible compensation of structural and viscotropic properties in hepatic microsomes and erythrocyte membranes of rats with essential fatty acid deficiency.

The effect of essential fatty acid deficiency on the structural and dynamic properties of the lipid matrix of rat liver microsomes and erythrocyte membranes was studied. The rate and range of the rotational mobility of 1,6-diphenyl-1,3,5-hexatriene and 2-, 7-, and 12-(9-anthroyloxy)stearate probes in the native membranes and in lipid vesicles prepared with the total lipid extracts of these membranes were evaluated by using differential polarized phase fluorometry. For the anthroyloxystearate probes, two modes of rotation (in and out of the plane of the aromatic anthracene ring) were partially resolved by measuring at different excitation wavelengths. The fat-free diet produces important changes in the fatty acid composition of the different glycerophospholipid classes without affecting the total double-bond number, the relative contents of cholesterol, phospholipid, and protein, and the glycerophospholipid class distribution. The principal changes, more pronounced in liver microsomes than in erythrocytes, are: an increase in nonessential monoene and triene (18:1n-9 and 20:3n-9) and a decrease in essential diene (18:2n-6) and tetraene (20:4n-6). These changes modify the double-bond distribution as a function of the distance from the interphase toward the bilayer interior, with a significant deficit (15% in erythrocytes and 30% in liver microsomes) in the double-bond density in the intermediate region of the membrane leaflet, corresponding to the carbon number 11-12 of an extended saturated acyl chain, and where the 12-anthroyloxystearate probe is located. In spite of the changes in fatty acid composition and double-bond distribution, with the only exception of a slight increase (about 15%) in the "out of the plane" rotation rate of the 7-(9-anthroyloxy)stearate probe in the erythrocyte lipid vesicles, no other significant change is observed. Thus, the changes in fatty acid composition would take place in such a way that at least the average structural and viscotropic properties of the lipid phase of the membrane, sensed by these probes, would be almost exactly compensated.

Animals↗
PubMed1993

Trypanosome metabolism of myristate, the fatty acid required for the variant surface glycoprotein membrane anchor.

The trypanosome variant surface glycoprotein (VSG) is anchored to the outer leaflet of the parasite plasma membrane by a glycosyl phosphatidylinositol (GPI). The VSG anchor is unique among GPIs in containing exclusively dimyristoylglycerol as its lipid moiety. Myristate is incorporated into the anchor precursor by sequential deacylation and specific reacylation with myristate. Although myristate is required for the VSG anchor, trypanosomes cannot synthesize this fatty acid and must import their entire supply from the host bloodstream, where it exists in low abundance. Chemical analysis of these parasites reveals that most of their myristate is in VSG protein, with no major lipid storage form. Unexpectedly, when these cells are radiolabeled with [3H]myristate in culture, most of the label is incorporated into phospholipids, with little into VSG. This apparent contradiction is explained by the fact that trypanosomes in culture medium elongate much of the [3H]myristate into palmitate and stearate, probably because the medium (with only 5% serum) contains limiting amounts of these fatty acids. In contrast, trypanosomes radiolabeled in whole blood (with higher concentrations of palmitate and stearate) do not modify most of the [3H]myristate, and instead utilize the major portion of it for GPI synthesis. Our studies suggest that bloodstream trypanosomes have evolved highly efficient means of directing myristate into the GPI biosynthetic pathway.

Acetates↗
PubMed1998

Substantial carbon recycling from linoleate into products of de novo lipogenesis occurs in rat liver even under conditions of extreme dietary linoleate deficiency.

A significant portion of the beta-oxidized carbon skeleton of some polyunsaturated fatty acids can be recycled into de novo lipogenesis, i.e., cholesterol, saturates and monounsaturates. The recycling of carbon from linoleate was quantified in liver lipids of severely linoleate-deficient rats to determine whether it is more likely to be a function of redundancy or could be obligatory. After 13 wk on a control (2 energy % linoleate) or severely linoleate-deficient (<0. 05 energy % linoleate) diet, 7 muCi [1-14C]linoleate was given by gavage and the rats were killed 48 h later. A second linoleate-deficient group received an oral bolus of 256 mg linoleate as a supplement with the radiotracer. In comparison to the controls, 14C recovery in liver total lipids of the linoleate deficient group was increased about 5-fold with increased dpm/g in linoleate (13.7-fold higher), arachidonate (2.7-fold higher) and products of de novo lipogenesis (3.5-fold higher). In livers of control rats, 14C distribution was: 41% arachidonate, 29% linoleate, 22% sterols, 3% oleate, 3% palmitate, and 2% stearate. In livers of linoleate-deficient rats, 14C distribution was: 63% linoleate, 19% arachidonate, 11% sterols, 4% oleate, 3% palmitate, and <1% stearate. Thus, in controls, equivalent amounts of 14C were in products of de novo lipogenesis as in linoleate (29-30%), and in livers of linoleate-deficient rats, a similar proportion of 14C was in products of de novo lipogenesis as was converted to arachidonate (18-19%). We conclude that carbon recycling into de novo lipogenesis accounts for a significant, obligatory component of linoleate metabolism even during extreme linoleate deficiency.

Animals↗
PubMed1998

The use of some hydrophobic substances in tablet technology.

The objective of this work is to continue in a study of utilization of synthetic triacylglycerides of higher aliphatic acids as additives improving the flow properties of granulates and reducing die friction in the tabletting press. These effects are not supposed to interfere with the drug liberation velocity. We have evaluated the effects of the synthetic triacylglycerides in theophylline containing model tablets using magnesium stearate as the reference standard. Magnesium stearate is the lubricant of choice in the production, found in up to 80% of all industrially produced tablets.

Calorimetry, Differential Scanning↗