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At least 145 records · Page 8Linked to original sources
PubMed1988

Human tissue factor contains thioester-linked palmitate and stearate on the cytoplasmic half-cystine.

The state of the five half-cystine residues in human tissue factor (TF) has been characterized. The results indicate that the four half-cystines in the extracellular domain of TF form two disulfide bonds and the half-cystine in the cytoplasmic region is acylated by palmitic acid and stearic acid. The extracellular disulfide cross-links, Cys49-Cys57 and Cys186-Cys209, were deduced from the analysis of tryptic peptides. Acylation of the cytoplasmic half-cystine was demonstrated by purifying and characterizing fibroblast TF from cells labeled with [3H]palmitic acid. Radiolabeled fibroblast TF was observed by autoradiography following sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The tritiated material covalently bound to the protein was identified as [3H]palmitate and [3H]stearate by reverse-phase high-pressure liquid chromatography. Deacylation of TF with hydroxylamine resulted in the spontaneous generation of disulfide-linked TF dimers. This result suggests that the disulfide-linked TF dimer, a minor component of most TF preparations, and the recently described heterodimeric form of TF are artifacts produced by deacylation of Cys245 and subsequent interchain disulfide bond formation.

Autoradiography↗
PubMed2006

Solution structures of spinach acyl carrier protein with decanoate and stearate.

Acyl carrier protein (ACP) is a cofactor in a variety of biosynthetic pathways, including fatty acid metabolism. Thus, it is of interest to determine structures of physiologically relevant ACP-fatty acid complexes. We report here the NMR solution structures of spinach ACP with decanoate (10:0-ACP) and stearate (18:0-ACP) attached to the 4'-phosphopantetheine prosthetic group. The protein in the fatty acid complexes adopts a single conformer, unlike apo- and holo-ACP, which interconvert in solution between two major conformers. The protein component of both 10:0- and 18:0-ACP adopts the four-helix bundle topology characteristic of ACP, and a fatty acid binding cavity was identified in both structures. Portions of the protein close in space to the fatty acid and the 4'-phosphopantetheine were identified using filtered/edited NOESY experiments. A docking protocol was used to generate protein structures containing bound fatty acid for 10:0- and 18:0-ACP. In both cases, the predominant structure contained fatty acid bound down the center of the helical bundle, in agreement with the location of the fatty acid binding pockets. These structures demonstrate the conformational flexibility of spinach ACP and suggest how the protein changes to accommodate its myriad binding partners.

Acyl Carrier Protein↗
PubMed1990

A pharmacokinetic and MRI study of unilamellar gadolinium-, manganese-, and iron-DTPA-stearate liposomes as organ-specific contrast agents.

Small unilamellar liposomes that contain the lipophilic chelate DTPA-stearate (DTPASA) were used as carriers for the paramagnetic metal ions gadolinium, manganese, and iron. The iron liposomes were unstable in vitro and thus not studied further. The natural targeting properties of these liposomes to the reticuloendothelial system was used in rats and dogs for the imaging of liver and spleen. In vitro incubations with human plasma, followed by high-pressure liquid chromatography (HPLC) separation of the Gd-DTPASA and Mn-DTPASA liposomes showed that after an incubation period of 24 hours, only 4% of the gadolinium was bound to the plasma proteins, whereas, with the Mn-DTPASA liposomes, a transfer of 40% manganese was seen. These results indicate that the Mn-DTPASA complex is not stable. On T1-weighted images, both liposome preparations gave a strong signal enhancement of the organs of the mononuclear phagocyte system (MPS). Gadolinium liposomes accumulated in the liver of rats at a peak concentration 4 hours after application and at a higher concentration compared with the manganese liposomes. Gd-DTPASA liposomes had an elimination half-time from the liver of 61 hours. Manganese liposomes produced stronger contrast at lower concentrations and had faster elimination kinetics from the liver, with a major elimination half-time of 10 hours. Both chelate complexes were eliminated predominantly by the hepatobiliary route. Thus, liposomal Gd-DTPASA appears to be a stable, efficient, and specific magnetic resonance imaging (MRI) contrast agent for the upper abdomen.

Animals↗
PubMed1979

Effects of spin-labeled stearates on duck erythrocyte adenylate cyclase.

The effects of various spin-labeled stearates on duck erythrocyte adenylate cyclase were investigated. Only 2-(3-carboxypropyl)-4,4-dimethyl-2-tridecyl-3-oxazolidinyloxyl caused an increase in adenylate cyclase activity. It increased the basal rate by about 50%, and the activities stimulated by isoproterenol and isoproterenol plus guanosine 5'-[beta,gamma-imido]triphosphate by 35%. Upon analysis of the width parameter delta1 in the electron spin resonance spectra for both the basal enzyme activity and the stimulation obtained with effectors such as guanosine 5'-[beta,gamma-imido]triphosphate, isoproterenol, isoproterenol plus guanosine 5'-[beta,gamma-imido]triphosphate and NaF, a correlation of the changes of modification in adenylate cyclase activities was found. These findings suggest that the molecular environment of the enzyme has been modified.

Adenylyl Cyclases↗
PubMed1989

Serum albumin binding of palmitate and stearate. Multiple binding theory for insoluble ligands.

In usual studies of ligand binding to a carrier, free and bound ligand concentrations are measured in equilibrium mixtures with varying carrier and ligand concentrations. The observed data are then analyzed by a binding equation such as Scatchard's or the general binding equation. With palmitic, stearic and oleic acids as ligands we found that the aqueous solubility is too low to allow this procedure. We have consequently transformed the general binding equation so that it does not contain parameters related to aqueous solutions of the ligand. While the classical binding equations describe affinities of transfer of a ligand from an aqueous solution to the carrier, the new equation is valid for transfer of a ligand from one bound state to another, i.e. for relative binding description. The relative binding constants, L1, L2, L3 ... Li, in the new equation thus define the transfer affinity for the ligand from a 1:1 complex with a standard carrier to an i:1 complex of the ligand with the carrier investigated. Binding of palmitate and stearate to human serum albumin was studied by determination of dialytic exchange rates between identical fatty acid/albumin solutions. The results were analyzed by the new equation without reference to ligands in aqueous solution.

Chlorides↗
PubMed1975

Comparison of erythromycin ethyl succinate, stearate and estolate treatments of group A streptococcal infections of the upper respiratory tract.

The microbiologic and clinical responses of acute Group A beta-hemolytic streptococcal infections of the upper respiratory tract to oral treatment with erythromycin ethyl succinate, stearate, and estolate were studied in 303 patients. Streptococcal M and T typing was done on all positive cultures. The overall cure rate was 95.4 per cent, with no statistically significant differences in clearing organisms from the pharynx. Of the 285 cured patients who completed the prescribed follow-up period, 11 had recurrences between the 12th and 31st day after initiation of therapy, and five developed new infections. No cases of rheumatic fever or glomerulonephritis were encountered during a follow-up study. Eight gastrointestinal reactions and one transient rash occurred. Results with these forms of erythromycin compare favorably with published results for similar infections treated with oral penicillins.

Administration, Oral↗
PubMed1975

Erythromycin stearate in acute maxillary sinusitis.

76 patients with acute maxillary sinusitis were treated with oral erythromycin stearate (500 mg twice or 3 times a day for 10 days). The mean concentration of erythromycin in the sinus secretion after 3-5 days' treatment was 0.6 mug/ml with the lower dosage and 1.3 mug/ml with the higher. The concentration of erythromycin in the sinus secretion was, on the average, 10-20 times higher than the minimum inhibitory concentration (MIC) for group A streptococci and pneumococci, and reached MIC values for 15-30% of 100 examined strains of Haemophilus influenzae. 81% of the patients given the smaller and 94% of those given the larger dose improved or recovered. Radiological improvement was demonstrated in both groups. The infections with H. influenzae tended to respond somewhat less to the treatment than those with pneumococci. Comparisons of the roentgen findings and the findings at aspiration showed good agreement. An extra projection taken with the patient recumbent and the affected side downwards gave no information above that obtained from the routine projections. The large dose caused side effects more often (in 17/41 patients) than the smaller one (4/35 patients). In 10 patients treatment was discontinued because of side effects; 8 of them had received the larger dose.

Acute Disease↗
PubMed1992

[The cytotoxic action of metal stearates and its correlation with the toxicity for animals].

Toxic effects of lead, cadmium, barium, silver, zinc and calcium stearates on the Rh-type cells culture have been revealed. The expressiveness of the cytotoxic action correlated with the toxicity degree for laboratory animals. The strongest (r = 0,98; p less than 0,01) was the correlation between cytotoxicity parameter (the minimal cytoclastic concentration) and the inhalation toxicity parameter in animals (lim(ac)). The results permitted deriving formulae for predicting some toxicity parameters (intraperitoneal LD50, lim(ac)), hygienic regulations (MAC), and showed that the prediction based on cytotoxicity data is more reliable, than that based on toxicometric parameters in short-term experiments used for such purpose.

Air Pollutants, Occupational↗
PubMed1992

Metabolism of intravenously administered 7 alpha-hydroxycholesterol-3 beta-stearate in the hamster.

In order to investigate the metabolic fate of serum esterified 7 alpha-hydroxycholesterol, [4-14C]7 alpha-hydroxycholesterol-3 beta-stearate was synthesized from labeled cholesterol and administered to bile fistula hamsters intravenously. Bile samples were collected at every 20 min for 7 h. Radioactivity was detected in bile 40 min after the beginning of the infusion of the labeled compound and 56.5 +/- 5.7% (48.7-66.0%) of the administered radioactivity was recovered in bile during 7 h. The liver contained appreciable radioactivity (19.5 +/- 7.6% of the administered dose) at the time of sacrifice. Only a trace amount of radioactivity was detected in urine and blood. Cumulative recovery of the radioactivity was 76.3 +/- 8.6% (63.3-90.4%). Major radioactive metabolites in the bile samples were identified to be taurine- and glycine-conjugated cholic acid and chenodeoxycholic acid by radioactive thin-layer chromatographic analysis of the bile samples before and after enzymatic hydrolysis and 3 alpha-hydroxysteroid dehydrogenase treatment. The conversion was nearly complete and we could not detect neutral metabolites, such as the mother compound, free 7 alpha-hydroxycholesterol and bile alcohols, as well as glucuronidated or sulfated bile acids. It is concluded that serum esterified 7 alpha-hydroxycholesterol could be effectively taken up by the liver, hydrolyzed by cholesterol esterase and metabolized via the normal biosynthetic pathway to taurine- or glycine-conjugated primary bile acids to be excreted into bile.

Animals↗
PubMed1997

Mixtures of Ascorbyl-stearate and Vitamin D3: A Monolayer Study at the Gas/Water Interface

Vitamin C and vitamin D3 perform different and important activities in living systems. Vitamin D3 forms stable monomolecular films at the gas/water interface and, at higher concentrations, produces large aggregates in water solutions. Because of their amphiphilic structure, vitamin C alkyl esters form monolayers, micelles, vesicles, or microemulsions in water, depending on composition, concentration, solvent, and temperature. In this work the monolayer of 6-O-ascorbyl-stearate and vitamin D3 was studied to investigate the behavior of the two compounds and their mixtures at the gas/water interface at different temperatures, at different pH, and in the presence of Ca2+ in the subphase. The results show that stable Langmuir films are formed in all molar ratios, with repulsive interactions between the two components, and that the presence of calcium ions modifies the properties of the monolayer.

Journal Article↗
PubMed2000

Preparation and Characterization of Stearate-Capped Titanium Dioxide Nanoparticles.

The preparation of titanium dioxide nanoparticles capped with stearate by sol-gel methods is presented in this paper. The nanoparticles are characterized by Fourier transform infrared spectroscopy and by X-ray photoelectron spectroscopy. Existence of the organic layer can be confirmed by the results of characterizations, which also indicate that the inorganic nuclei and organic surface layer are linked with chemical bonds. The nanoparticles are poorly crystallized based on the X-ray diffraction pattern. The mechanism of formation of the organo-capped nanoparticles is proposed to be competitive reactions between water and stearic acid, which is similar to a polymerization and inhibition processes. A structural model for organo-capped nanoparticles is also proposed. Copyright 2000 Academic Press.

Journal Article↗
PubMed1979

Single-dose fasting bioequivalence assessment of erythromycin stearate tablets in man.

The bioequivalence of film-coated erythromycin stearate tablets produced by five different manufacturers was evaluated in a balanced incomplete block design involving the five formulations given to 30 fasted subjects over a 3-week study period. Serum levels of erythromycin activity were determined microbiologically. Statistical analysis of variance was performed on the observed bioavailability parameters: maximum serum concentration (Cmax), time to maximum serum concentration (Tmax), and area under the serum concentration-time curve (AUC). There was no statistical difference between formulations for the Tmax parameter. Formulation differences were found, however, based on the analysis of variance of the Cmax and AUC parameters. Two products, although not significantly different from one another, showed significantly greater Cmax and AUC values than the other three products.

Adult↗
PubMed1989

Characterizing stearate probes in vitro for the electrochemical detection of dopamine and serotonin.

This paper describes an electrochemical method for the detection of dopamine and serotonin in vitro. Dopamine and serotonin can be distinguished from each other without interference from metabolites. 3-4-dihydroxyphenylacetic acid and 5-hydroxyindoleacetic acid. The method also provides selective differentiation of dopamine and serotonin in the presence of other possible interfering chemicals, ascorbic acid and uric acid. Specific details for voltammetric technology, electrode fabrication, electrode conditioning, paste synthesis and experimental protocol are presented. The method uses semidifferential treatment of voltammetric data in conjunction with a graphite stearate indicator electrode. The methodology is relevant to the interpretation of electrochemical signals for dopamine and serotonin in vivo in neuroanatomical substrates, richly innervated by dopaminergic and serotonergic neuronal circuitry.

Dopamine↗
PubMed1985

Measurement of the lateral diffusion coefficients of ubiquinones in lipid vesicles by fluorescence quenching of 12-(9-anthroyl)stearate.

The lateral diffusion coefficients of some ubiquinone homologues have been measured in phospholipid vesicles exploiting the fluorescence quenching of the probe 12-(9-anthroyl)stearate by the quinones. Diffusion coefficients higher than 10(-6) cm2 X s-1 have been found at 25 degrees C, compatible with the localization of the ubiquinones in the low-viscosity midplane region of the bilayer.

Diffusion↗
PubMed1991

Penetration of erythromycin into periapical lesions after repeated doses of erythromycin acistrate and erythromycin stearate: a pilot study.

In 26 patients who had undergone apicectomy and extirpation of granulomas (n = 9) or radicular cysts (n = 17), concentrations of erythromycin, 2'-acetyl erythromycin, and their anhydro forms were determined with a novel chemical method in plasma and periapical lesions after at least 2 days of treatment with erythromycin acistrate (EA) (400 mg three times daily, n = 11) or erythromycin stearate (ES) (500 mg three times daily, n = 15). Oral surgery was performed 2 1/2 to 3 hours after the last dose. Blood samples were collected at the time of operation, and immediately before antibiotic treatment, and 1, 2, and 6 hours after treatment. At all time points EA produced at least twice the total antibiotic (2'-acetyl erythromycin plus erythromycin) concentrations in plasma as ES. Erythromycin levels in plasma were at least as high after EA treatment as after ES. In periapical lesions erythromycin concentration after EA was three times higher (1.34 +/- 0.28 micrograms/gm) than after ES treatment (0.40 +/- 0.17 micrograms/gm). Although the total drug concentration in periapical lesions was about the same after EA (2.64 micrograms/ml) and ES (3.41 micrograms/ml), most of the drug recovered after ES was antimicrobially inactive anhydroerythromycin (3.01 micrograms/gm). The concentration of anhydroerythromycin in plasma was approximately the same as that of erythromycin after ES throughout the dose interval. After EA treatment both plasma and the periapical lesion samples contained hardly detectable amounts of anhydroerythromycin. Hence EA has a good bioavailability essential for treatment and prophylaxis of bacterial infections in dentistry.

Adult↗
PubMed1990

Chlordecone impairs Na(+)-stimulated L-[3H]glutamate transport and mobility of 16-doxyl stearate in rat liver plasma membrane vesicles.

Chlordecone (CD) treatment of rat liver plasma membranes (LPM) provided in vitro evidence for mechanisms of in vivo liver dysfunction caused by CD. LPM preparations enriched 14- to 19-fold in the bile canalicular markers gamma-glutamyl transpeptidase, alkaline phosphatase, and leucine aminopeptidase were isolated from male Sprague-Dawley rats. CD inhibited the bile canalicular-specific active transport of Na(+)-stimulated L-[3H]glutamate in LPM vesicles. CD (0.08 and 0.5 mumol/mg protein) reduced both the initial velocity and the maximum level of Na(+)-stimulated L-[3H]glutamate uptake without significantly reducing Na(+)-independent uptake. In vitro treatment of LPM with CD (0.2-1.0 mumols/mg protein) also reduced the mobility of a 16-doxyl stearate spin label probe in a concentration-dependent manner. No change in mobility was apparent at CD concentrations below 0.2 mumol/mg protein. These results demonstrated that CD impaired a bile canalicular-specific transport system and induced liver plasma membrane perturbation. Na(+)-stimulated L-[3H]glutamate uptake was more sensitive to CD than was detectable immobilization of the spin label probe.

Animals↗
PubMed1987

The effect of polyoxyethylene stearate (POES) on the growth of mycobacteria in radiometric 7H12 Middlebrook TB medium.

Polyoxyethylene stearate (POES) is a non-ionic emulsifying agent. Such agents have been shown to enhance the growth of mycobacteria in vitro. POES (POE(JL)S) has been recommended as an additive to the radiolabelled 7H12 Middlebrook TB media and as such has been shown to enhance growth of mycobacteria in the radiometric BACTEC rapid culture system. We examined the growth enhancing effect of six previously untested POE's (POE(8)S to POE(100)S) whose spreading properties (Hydrophilic-Lipophilic Balances-HLB's) were known. The aim of this study was to determine which POES has the greatest ability to enhance the growth of different mycobacterial species and how the HLB of each POES related to its effect on the growth of each species. We found that POE(50)S produced the greatest enhancement in growth and reduction in the time taken to detect growth for M. tuberculosis and POE(30)S and POE(JL)S for species of mycobacteria other than M. tuberculosis (MOTT). Comparing the effects of POES's to their HLB's (in BACTEC 7H12 media) we suggest four factors which may affect the growth enhancing ability of each POES: 1 its dispersal effect on the bacteria (acting as an emulsifier); 2 it's solubilizer effect on the bacterial cell; 3 the effect the POES on the dispersal of the radiolabelled fatty acid used as a substrate in the media to produce radiolabelled CO2; 4 mycobacteria may metabolise POES.

Culture Media↗