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At least 685 records · Page 38Linked to original sources
PubMed1987

Influence of saturated and unsaturated fats on platelet fatty acids in cholesterol-fed rabbits.

Feeding natural fats varying in contents of palmitate (16:0), stearate (18:0), oleate (18:1), and linoleate (18:2) to rabbits resulted in modulation of platelet phospholipid fatty acyl composition. Rabbits were fed high fat semipurified diets containing 2% corn oil (CO) + 18% CO, cocoa butter (CB) or milkfat (M) for periods of up to 300 d. Platelet phospholipid linoleate contents corresponded to diet levels with 18:2 highest in CO-fed rabbits and following the sequence CO greater than CB greater than M. Stearate was highest in CB-fed rabbits, corresponding to high 18:0 levels in CB, but palmitate levels were not affected by diet. Both CB and M-fed rabbits were higher than CO-fed rabbits in oleate. Though CO is highest in 18:2, the accepted 20:4 precursor, arachidonate was highest in M-fed rabbits. Adding cholesterol (0.2%) to the diets did not affect platelet phospholipid fatty acyl composition except to elevate 20:4 in M-fed rabbits. CO-fed rabbits showed uniquely high levels of tetracosadienoate (24:2). Fatty acyl composition data were essentially constant between 200 and 300 d on diet. Phospholipid fatty acyl unsaturation was apparently homeostatically controlled as mole percent unsaturate to saturate ratios were independent of diet. The observed homeostasis resulted in minimal diet influences on platelet membrane fluidity and ADP or collagen stimulated platelet aggregation. Platelet fluidity, determined by fluorescence polarization, was a function of oleate and linoleate contents of the cells. Cholesterol feeding generally lowered platelet fluidity and altered the dependence of fluidity on fatty acyl composition.

Animals↗
PubMed1992

Metabolic effects of dietary stearic acid in mice: changes in the fatty acid composition of triglycerides and phospholipids in various tissues.

The fatty acid patterns of triglycerides and phospholipids extracted from adipose tissue, liver, heart, kidney, spleen, and lung of 3 groups of C57BL/6 mice were determined after feeding diets rich in palmitic acid (16:0) (high palmitic: 16:0 = 45.1% of total fatty acids), stearic acid (18:0) (high stearic: 18:0 = 42.9% of total fatty acids) and oleic acid (18:1) (high oleic: 18:1 = 79.7% of total fatty acids) for 9 months. Triglyceride content of adipose, liver, heart, kidney, lung and spleen tissues was significantly enriched in palmitic acid in mice fed the high palmitic diet (range among all tissues: 19.9% +/- 0.2% to 29.0% +/- 1.9% of total fatty acids) and in oleic acid in mice fed the high oleic diet (range 56.0% +/- 1.9% to 71.6% +/- 1.2%). The stearic acid content of organ triglycerides in mice fed the high stearic diet ranged from 3.7% +/- 0.3% to 10.8% +/- 1.2%; however, the content of oleic acid on this diet (range: 57.0% +/- 1.8% to 71.4% +/- 1.7%) was similar to the one observed in mice fed the high oleic diet. In all organs, phospholipids had a significantly higher percentage of stearic acid (range: 23.5% +/- 0.9% to 51.5% +/- 6.6%) than triglycerides, regardless of diet. To evaluate the production of oleate from stearate and palmitate, 2 groups of mice were fed the high palmitic and the high stearic diets for 1 week and then injected intravenously with [1-14C]palmitate and [1-14C]stearate and the amount of labelled oleate in liver triglycerides was measured.(ABSTRACT TRUNCATED AT 250 WORDS)

Adipose Tissue↗
PubMed1993

In vitro hepatic thyroid hormone deiodination in iron-deficient rats: effect of dietary fat.

The effects of different dietary fats on thyroid indices were studied in weanling iron-deficient rats. Rats were fed one of five different diets (safflower oil with a casein protein source, safflower oil with defatted beef as the protein source, prime rib, beef tallow with casein and stearate with casein). Both dietary fat and iron status (adequate, CN; deficient, ID; or iron-deficient replete, ID-replete) had significant effects on body weight and hemoglobin concentrations. The tallow-fed animals weighed the least relative to animals fed the other fats; ID rats were smaller than CN rats. The tallow- and stearate-fed animals had the highest hemoglobin concentrations. Type of dietary fat affected plasma thyroxine (T4), but not plasma triiodothyronine (T3) or rate of deiodination of reverse T3 (rT3). Iron deficiency decreased plasma concentrations of T3 and T4 and increased in vitro hepatic rT3 deiodination, suggesting that the ID animals tend to metabolize thyroid hormones via deactivating pathways. The alterations in thyroid hormone metabolism associated with iron deficiency are reversible with iron repletion.

Animals↗
PubMed1987

Infectious flare-ups and serious sequelae following endodontic treatment: a prospective randomized trial on efficacy of antibiotic prophylaxis in cases of asymptomatic pulpal-periapical lesions.

Without peritreatment antibiotics, infectious flare-ups (about 15% incidence) and serious sequelae follow endodontic treatment of asymptomatic teeth with necrotic pulps and associated periapical lesions. Antibiotics administered after endodontic treatment (4-day regimen) reduce the flare-up incidence to about 2%, but hypersensitivity responses, sensitization, resistant microbes, and drug-taking compliance are potential problems. To ascertain whether a specific prophylactic antibiotic (high-dose, 1-day regimen) would preferentially maintain this low flare-up incidence while overcoming antibiotic-related problems, 315 patients with quiescent pulpal necrosis and an associated periapical lesion were randomly given either penicillin V or erythromycin (base or stearate). Evaluations of flare-up after endodontic treatment were done at 1 day, 1 week, and 2 months. A 2.2% flare-up incidence was found, with no statistically significant differences for penicillin (0.0%), base (2.9%), and stearate (3.8%). No hypersensitivity responses occurred. Gastrointestinal side effects were found primarily with the erythromycins (12.4%). A comparative analysis of the data from our first study (no peritreatment antibiotics) and the pooled data from our last two investigations (including the current trial) showed that peritreatment antibiotic coverage significantly reduced flare-ups and serious sequelae after endodontic treatment (p less than 0.001).

Adolescent↗
PubMed1990

A comparison of erythromycin and cefadroxil in the prevention of flare-ups from asymptomatic teeth with pulpal necrosis and associated periapical pathosis.

In a previous study by our group with patients having asymptomatic teeth with pulpal necrosis and an associated periapical radiolucent lesion (PN/PL), it was shown that prophylactic administration of penicillin V or erythromycin (high-dose, 1-day regimen) resulted in a low incidence of flare-up (mean = 2.2%) and a low incidence of swelling and pain not associated with flare-up. No hypersensitivity responses occurred, and gastrointestinal side effects were found primarily with the erythromycins. To ascertain whether a single-dose administration of a long-acting 1-gm tablet of the cephalosporin antibiotic cefadroxil would result in a similar outcome, the present study was undertaken with 200 patients having quiescent PN/PL. The patients were randomly given either cefadroxil or erythromycin (base or stearate). Evaluations of flare-up were done 1 day, 1 week, and 2 months after endodontic treatment. A 2.0% flare-up incidence was found, with no statistically significant differences for cefadroxil (1.0%), stearate (2.0%), or base (4.0%). No hypersensitivity responses occurred. Gastrointestinal side effects were found primarily with the erythromycins (19.0%). The results showed that a 1-gm, single-dose regimen of cefadroxil was as effective as erythromycin and penicillin in preventing flare-ups and serious sequelae. A comparative analysis of the data from our first study (no peritreatment antibiotics) and the pooled data from our last three investigations (including the current trial) showed that peritreatment antibiotic coverage significantly reduced flare-ups and serious sequelae after endodontic treatment of asymptomatic PN/PL (p less than 0.001).

Acute Disease↗
PubMed1990

Characterization of spin-labelled fatty acids and hematoporphyrin binding sites interactions in serum albumin.

Electron paramagnetic resonance (EPR) was used to investigate the spin-labelled fatty acid (SLFA) binding equilibrium to human (HSA) and bovine (BSA) serum albumin. The number of 5-doxyl stearate (5-DS) and 16-doxyl stearate (16-DS) binding sites on HSA and BSA were found to be equal, while the association constants, KA values (especially those of the primary binding site) were different. The applied EPR spectra analysis permitting a quantitative distinguishing between slow macromolecular rotation (pi c) and fast anisotropic motion (steric restriction, S) of bound SLFA, allowed SLFA oxazolidinyl ring mobility to be estimated. The 5-DS nitroxide radical is completely immobilized within the HSA protein matrix (S approximately 1.0, pi c approximately 56 +/- 1 ns). The 5-DS when bound to BSA exhibited the presence of more extensive fluctuations (lower S and pi c values) and its immersion depth with respect to BSA surface was calculated to be 4 +/- 2 A. The 16-DS oxazolidinyl radical bound to HSA was found to undergo moderated fluctuations (both S and pi c are smaller with respect to 5-DS) and it is buried deeper within the protein core (rimm = 10 +/- 2 A with respect to BSA surface). The tetrapyrrole ligands hematoporphyrin (Hp) and hematoporphyrin derivative (HpD) were found to induce well detectable changes in the SLFA binding patterns to serum albumin. The action mode was determined to be different for 16-DS (primary) and 5-DS (secondary) serum albumin binding sites: (i) 5-DS is extruded from several binding sites accompanied by an increase in KA in the remaining ones; (ii) simultaneous binding of 16-DS and Hp consists of cooperative and non-cooperative phases (both the number of the independent sites and the parameter of cooperativity, alpha, being dependent on Hp/HSA ratio); (iii) in principal the mobilities of 5-DS and 16-DS bound to HSA are changed, depending on the porphyrin/HSA ratio; and (iv) the effective immersion depth of the paramagnetic centres with respect to the protein surface is increased when Hp is present as a second ligand (rimm = 7 +/- 2 and 16 +/- 2 A for 5-DS and 16-DS, respectively).

Binding Sites↗
PubMed1994

Effect of sucrose monostearate, an emulsifier, on polyamine metabolism and phosphatidylinositol turnover in Ehrlich ascites tumor cells.

Sucrose esters of fatty acids have antitumor activity. We studied the effect of sucrose monostearate (SS), an emulsifier, on polyamine metabolism and phosphatidylinositol turnover in Ehrlich ascites tumor cells. The activity of ornithine decarboxylase (ODC) was increased in the cells by changing the medium. This increase in the activity was inhibited by adding sucrose stearate, but not sucrose or stearate to the medium. The activity of spermidine/spermine N1-acetyltransferase (SAT), a rate-limiting enzyme of polyamine biodegradation, was enhanced with the addition of SS in a time- and dose-dependent manner. The elevation of SAT activity was completely prevented when cycloheximide was added to the culture simultaneously. In in vitro studies, SS at various concentrations up to 1 mM hardly affected the activities of ODC or SAT. The incorporation of [3H]inositol into both fractions of inositolphospholipid and inositol phosphates was inhibited by SS. These results suggest that the perturbation of polyamine metabolism and phosphatidylinositol turnover is involved in the mechanism of antitumor activity of SS in Ehrlich ascites tumor cells.

Acetyltransferases↗
PubMed1993

Intravascular metabolism of different fatty acids during lipid infusion in man.

The differential intravascular metabolism of individual fatty acids contained in triacylglycerol-rich particles was studied by infusing 6 normal subjects for 5h with a conventional soy-based emulsion and an experimental olive oil-based emulsion. Both emulsions contained similar amounts of palmitate (11%) and stearate (3-4%) but the former was quite rich in linoleate (54%) and alpha-linolenate (7%), while the latter was rich in oleate (69%). During hydrolysis of circulating triacylglycerols by endothelial lipases, the associated rise of non-esterified fatty acids (FFA) in plasma represents the balance between fatty acid release and tissue uptake. Plasma levels of triacylglycerols and FFA increased about 3 fold and total body fat oxidation was raised to similar values with both emulsions. Fatty acid pattern quickly changed in plasma triacylglycerols to resemble the composition of emulsion particles, with an exception for palmitate which increased markedly more, suggesting a high level of hepatic re-esterification and re-appearance in nascent very low density lipoprotein triglycerides (VLDL-TG) secreted into the circulation. In plasma FFA, stearate and palmitate increased more and alpha-linolenate much less than expected from their content in the emulsion, indicating probably low tissue uptake for the former ones but avid removal for the latter.

Journal Article↗
PubMed1985

Covalent adduct formation and chloroform production after free radical attack on fatty acids by carbon tetrachloride reactive intermediates.

The interactions of fatty acids and the trichloromethyl free radical generated anaerobically by the benzoyl peroxide model system were studied. Chloroform was produced due to the interaction of the trichloromethyl free radical with the unsaturated fatty acid ester methyl oleate, indicating the hydrogen in chloroform may result from abstraction from fatty acids. In addition, chloroform was detected in incubations containing the saturated fatty acid ester methyl stearate, indicating hydrogen abstraction is not limited to allylic hydrogens. Mass spectral analysis identified one adduct resulting from additional reactions to methyl oleate, and an adduct resulting initially from hydrogen abstraction on methyl stearate. These findings describe previously unreported reactions of the trichloromethyl free radical with saturated fatty acid, and inhibition of chloroform production by 3 free radical inhibitors.

Benzoyl Peroxide↗
PubMed1982

Comparative studies on the kinetic parameters and product analyses of chicken and rat liver and yeast fatty acid synthetase.

1. Comparative kinetics and product analyses of chicken and rat liver and yeast fatty acid synthetase. 2. Vmax's for the three enzymes studied decrease with increasing primer chain-length, while Km's (except for yeast) increases. 3. Palmitate is the main product (approximately 90%) of the rat synthetase whereas palmitate (60%) and stearate (40%) are the products of chicken and yeast enzymes. Increasing the primary chain length does not alter palmitate synthesis by rat and chicken enzymes but increases stearate synthesis by the yeast synthetase. 4. The three synthetases could not synthesize fatty acids in the absence of primer acetyl-CoA suggesting that malonyl-CoA decarboxylase is not a component.

Animals↗
PubMed1996

Selective spectrophotometric method for the determination of erythromycin and its esters in pharmaceutical formulations using gentiana violet.

A simple and selective method for the determination of erythromycin and its stearate and succinate esters in their pure forms and in pharmaceutical formulations is described. The procedure is based on the formation of a blue-coloured (lambda max = 633 nm) complex with gentiana violet in alkaline medium. Different variables affecting the colour development were studied and optimized. The method was used to determine 2.5-25 micrograms ml-1 of erythromycin in the final measured solution. The simplicity of the method permits rapid analysis and it is thus suitable for routine control. The method is highly specific for the determination of stearate and succinate esters in pharmaceutical formulations. The reliability of the method was established by parallel determinations against the official British Pharmacopoeial method.

Anti-Bacterial Agents↗
PubMed1994

Reduction of lipid-soluble nitroxides in CHO cells and macrophage tumor cells.

There is a need to understand the metabolism of nitroxides because of their usefulness in measurements in living cells of complex phenomena, such as biophysical properties, redox metabolism, and the concentration of oxygen at specific sites. As part of a systematic study of the metabolism of nitroxides in cells, the authors studied Chinese hamster ovary (CHO) cells and mouse macrophage tumor (M5076) cells, using a set of lipophilic nitroxides based on 5 doxyl stearate: the free acid, the methyl ester of the acid, and a phosphatidylcholine with two doxyl stearates esterified to the glycerol. The rates of metabolism of these nitroxides under anoxia differed significantly as a function of both the type of cell and the type of nitroxide. The rates of reduction of the three lipophilic nitroxides depended on their localization. The rates of reduction were first order for all three lipophilic nitroxides, and the only products detected were the respective hydroxylamines. Effects of freeze-thawing and incubation temperature differed in the two cell lines. The authors conclude that the metabolism of nitroxides in different cell lines can be quite different. This may be especially important in understanding studies using nitroxides in living cells, functional organs, and in vivo.

Animals↗
PubMed2006

Highly efficient protein separations in capillary electrophoresis using a supported bilayer/diblock copolymer coating.

A surfactant/polymer wall coating consisting of the doubly chained cationic surfactant dimethyldioctadecylammonium bromide (DODAB) and polyoxyethylene (POE) 40 stearate is investigated. The coating is formed by simply rinsing a capillary with a solution containing DODAB and POE 40 stearate. The resultant coating is semi-permanent--demonstrating stable electroosmotic flow (EOF) even after a 60 min high pressure rinse with buffer. The EOF (-0.45+/-(0.23) x 10(-4) cm(2) V(-1) s(-1) at pH 7.4) is suppressed by more than a factor of ten compared to that observed for DODAB alone. Model protein mixtures were separated over a pH range of 3-10 with efficiencies of up to greater than 1 million plates/m for the basic proteins cytochrome c, lysozyme, ribonuclease A and alpha-lactalbumin, and the acidic proteins insulin chain A, trypsin inhibitor, and alpha-chymotrypsinogen A. Migration time reproducibility was 0.5-4.0% from run to run and 0.6-4.3% from day to day. Protein recoveries with this coating ranged from 84% to 97%.

Electrophoresis, Capillary↗
PubMed2005

Compaction mechanism and tablet strength of unlubricated and lubricated (silicified) microcrystalline cellulose.

This paper describes the differences in compaction properties between microcrystalline cellulose (MCC) and microcrystalline cellulose co-processed with colloidal silicon dioxide (SMCC). The different compaction parameters are not only compared for the pure materials, but also for the lubricated powders with magnesium stearate. Neither magnesium stearate, nor colloidal silicon dioxide, facilitates extensively the densification of (silicified) microcrystalline cellulose during compaction. The difference in tablet relaxation of MCC and SMCC indicates a small negative effect of colloidal silicon dioxide on the interparticle bonding strength of unlubricated MCC. However, for lubricated MCC a larger increase in tablet relaxation at a high compression speed was found than for lubricated SMCC tablets. Accordingly, the decrease in tablet strength was larger for the MCC tablets than for the SMCC tablets when lubrication was applied. The examination of the tablet strengths of tablets compressed from physical mixtures of MCC with increasing concentrations of colloidal silicon dioxide proved the slightly negative influence of silicon dioxide on the tablet strength of unlubricated MCC tablets and the positive effect of colloidal silicon dioxide addition on the tensile strength of lubricated MCC tablets. Co-processing of MCC with colloidal silicon dioxide showed no extra contribution on the tablet strength of lubricated tablets above the physical mixtures. The interactions between the different materials were further supported by the interaction parameters based on partial solubility parameters.

Cellulose↗
PubMed2004

Search for technological reasons to develop a capsule or a tablet formulation with respect to wettability and dissolution.

Proquazone, a poorly wettable compound, was used as a model drug in the search for reasons to develop a capsule or tablet formulation. The capsules were filled with proquazone as active ingredient, with lactose monohydrate (200 mesh) as filler and with magnesium stearate as lubricant. The tablet was made out of a granulate as internal phase which consisted of proquazone as active ingredient, lactose as filler, corn starch as disintegrant and PVP as a binding agent. The external phase consisted of magnesium stearate and corn starch. The concentration of proquazone in the capsule and in the tablet formulation was varied. The capsule formulations showed a significantly slower dissolution of the drug substance than the tablet formulations especially for a high-drug load. Independently of the drug load, only the tablet formulation showed a high-dissolution rate. Thus, concerning drug load, only the tablet formulations showed to be robust. It became clear that proquazone needs to be formulated as a granulate or a tablet to achieve a fast dissolution rate. Thus, a poorly wettable drug, especially when it is found in high concentrations, can have direct impact on the decision to develop a tablet or a capsule formulation.

Capsules↗
PubMed2006

Measurement of the surface energy of lubricated pharmaceutical powders by inverse gas chromatography.

The objective of the study was to determine whether lubrication of pharmaceutical powders with magnesium stearate (MgSt) results in a change in the surface energy of the powder, and to assess whether surface energy changes, if any, are correlated to lubricant concentration and blend time. The surface energies of microcrystalline cellulose (MCC), lactose, and blends of each material with MgSt, prepared at a range of concentrations and blending times were measured using inverse gas chromatography. The physical distribution of MgSt in the blend was mapped by energy dispersive spectrometry. Overall, there was a reduction in the dispersive surface energy of MCC-MgSt blends with increase in MgSt concentration, that was attributed to increasing coverage of the high-energy sites on microcrystalline cellulose by magnesium stearate. MgSt concentration had a larger effect on dispersive energy than the blending time of the powder with lubricant. X-ray maps of blend samples indicated a heterogeneous distribution of the lubricant in the blend and on the excipient particles. Measurement of the specific component of surface energy indicated that MgSt interacts with excipient powders through non-specific forces rather than acid-base interactions. No distinction among lactose-MgSt blends could be made on the basis of dispersive energy because of similar surface energies of the native materials.

Cellulose↗
PubMed2006

Surface analysis of powder binary mixtures with ATR FTIR spectroscopy.

Attenuated Total Reflectance Fourier Transform Infra Red spectroscopy (ATR FTIR) has been used for surface analysis of powder mixtures. The appearance of one component on the surface of the mixture in greater amounts than that expected from the mass or volume ratio was quantified. Coloured mixtures containing methyl orange were analysed. They contained proportions of components from 0% to 100% in steps of 10%. Mixtures of non-sieved powders of methyl orange and Povidone were dark red when containing only 20% of methyl orange, indicating that particles of methyl orange were present on the surface of the mixture in higher amounts than expected from the mass ratios. Mixtures of methyl orange and Mg stearate, on the other hand, were a light colour, showing the presence of more Mg stearate on the surface than expected. Visual observations correlated with semiquantitative surface concentration determination by ATR FTIR spectroscopy using specific peaks of each component. Quantitative determination of components on the surface of the mixture, using the Beer Lambert law, was possible when characteristic peaks for the first component did not overlap with those of the other component. A non-linear correlation between peak height and concentration of a component in a mixture was explained by distribution of the particle size of components. With a small component, the larger number of particles in the same volume allowed them to surround the larger particles of the second component. These conclusions were confirmed by preparing mixtures with non-coloured components (Povidone-Eudragit, NaCl-Povidone, NaCl-Eudragit. Results again correlated with the ATR FTIR spectroscopy measurements. It was additionally shown that a small proportion of finer particles can drastically influence the surface of powder mixtures, due to their large contribution to the specific surface area. ATR FTIR is thus demonstrated to be a useful method for studying surfaces of powder mixtures also in terms of process analytical technology (PAT).

Azo Compounds↗
PubMed2005

Design and characterization of a new drug nanocarrier made from solid-liquid lipid mixtures.

The classical lipid nanoparticles that have been proposed for drug delivery are composed of solid lipids. Due to their composition, these nanoparticles have a limited drug loading and controlled release capacity. The present work was aimed at modifying the inner structure of nanoparticles made of tripalmitin, lecithin, and poly(ethylene glycol) (PEG)-stearate with the incorporation of a liquid lipid (Miglyol 812 oil). The composition and structural organization of the components of the resulting nanoparticles were characterized by (1)H NMR spectroscopy. Any possible changes in the crystalline domains of individual components when in the form of the nanoparticles were investigated by differential scanning calorimetry (DSC) and X-ray diffraction spectroscopy. The results of the NMR analysis indicated a significant incorporation of the oil to the solid nanoparticle matrix. Furthermore, the relaxation time constants as well as the peak width of the (1)H NMR spectrum of the nanoparticles suggest the presence of the oil in the form of phase-separated liquid nanoreservoirs within the nanoparticles. This conclusion was supported by the observation of restricted diffusion dynamics for the oil molecules. Interestingly, the incorporation of the oil did not interfere with the crystallization of the solid lipids (tripalmitin and PEG-stearate). In conclusion, a new nanostructure consisting of solid lipids and oily nanodomains was developed. This structural modification of the solid lipid nanoparticles may have an effect on their encapsulation capacity and controlled release properties.

Calorimetry, Differential Scanning↗