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At least 181 records · Page 10Linked to original sources
PubMed2003

Small-angle neutron scattering study of the lipid bilayer thickness in unilamellar dioleoylphosphatidylcholine vesicles prepared by the cholate dilution method: n-decane effect.

Previous X-ray diffraction studies on fully hydrated fluid lamellar egg phosphatidylcholine phases indicated a approximately 10 A increase of bilayer thickness in the presence of excess n-decane [Biochim. Biophys. Acta 597 (1980) 455], while the small-angle neutron scattering (SANS) on unilamellar extruded dioleoylphosphatidylcholine (DOPC) vesicles detected substantially smaller 2.4+/-1.3 A bilayer thickness increase at n-decane/DOPC molar ratio of 1.2 [Biophys. Chem. 88 (2000) 165]. The purpose of the present study is to investigate the n-decane effect on the bilayer thickness in unilamellar DOPC vesicles prepared by the sodium cholate (NaChol) dilution method. Mixed DOPC+NaChol micelles at DOPC and NaChol concentrations of 0.1 mol/l were prepared in 2H(2)O containing 0.135 mol/l NaCl. This micellar solution was diluted in 0.135 mol/l NaCl in 2H(2)O to reach the final DOPC and NaChol concentrations of 0.008 mol/l. Thirty microliters of n-decane solution in methanol was added to 1 ml of this dispersion. After methanol evaporation, SANS was conducted on the dispersions. From the Kratky-Porod plot ln[I(Q)Q(2)] vs. Q(2) of SANS intensity I(Q) in the range of scattering vector values Q corresponding to interval 0.001 A(-2)<or=Q(2)<or=0.006 A(-2), the bilayer radius of gyration R(g) and the bilayer thickness parameter d(g)=12(0.5)R(g) were obtained. The values of d(g) indicate that the bilayer thickness increases by 2.4+/-0.9 A up to n-decane/DOPC molar ratio of 1.6. This result confirms the previous SANS findings obtained with extruded vesicles.

Alkanes↗
PubMed2001

Separation and selectivity of benzophenones in micellar electrokinetic chromatography using sodium dodecyl sulfate micelles or sodium cholate modified mixed micelles.

The separation and selectivity of nine benzophenones in micellar electrokinetic chromatography (MEKC) using sodium dodecyl sulfate (SDS) micelles or sodium cholate (SC) modified mixed micelles were investigated in the pH range 6.5-8.0. The results indicate that the combined effects of buffer pH and SC concentration can greatly affect the separation and selectivity of benzophenones, particularly for benzophenones possessing a hydroxyl substituent at the 4-position of the aromatic ring with respect to the carbonyl moiety when using SDS-SC mixed micelles. Better separability can be obtained with SDS-SC mixed micelles than with SDS micelles. Complete separation of nine benzophenones in MEKC can be achieved with an appropriate choice of buffer pH and the concentration of SDS micelles or SC modified mixed micelles. The dependence of the migration order of those benzophenones based on their structures and solute-micelle interactions is discussed.

Benzophenones↗
PubMed2001

Discontinuous electrophoretic stacking system for cholate-based electrokinetic chromatographic separation of 8-hydroxy-2'-deoxyguanosine from unmodified deoxynucleosides.

The stacking and baseline-resolved separation of the oxidative damage marker, 8-hydroxy-2'-deoxyguanosine (8-OHdG), from unmodified deoxynucleosides in under 4 min is reported. Separations of 8-OHdG from 2'-deoxyadenosine, 2'-deoxycytosine, 2'-deoxyguanosine, and thymidine are accomplished using micellar electrokinetic capillary chromatography with sodium cholate. Importantly, the use of sulfate, intentionally added to the sample matrix, results in effective stacking of 8-OHdG and other analytes. This work extends electrokinetic stacking injection of neutral analytes to include deoxynucleosides. The procedure works well with either electrokinetic or hydrodynamic injection. The separation buffer and sample matrix composition were optimized to effect stacking conditions with an uncoated 50 microm fused-silica capillary. The lower limit of detection for the analytes is in the nanomolar range, and is more than an order of magnitude lower than without stacking. With 30 s (5.7 cm) electrokinetic injections, stacking and baseline separation of 8-hydroxy-2'-deoxyguanosine from the unmodified nucleosides is accomplished, even in the presence of a 400-fold excess of unmodified deoxynucleosides.

8-Hydroxy-2'-Deoxyguanosine↗
PubMed2003

Determination of hydroxyanthraquinoids in Rhubarb by cyclodextrin-modified micellar electrokinetic chromatography using a mixed micellar system of sodium dodecyl sulfate and sodium cholate.

A cyclodextrin-modified micellar electrokinetic chromatographic (CD-MEKC) method was established to determine five hydroxyanthraquinoids in Rhubarb. The five components were successfully separated by using the mixed micellar system consisting of 20 mmol/l sodium dodecyl sulfate (SDS) and 20 mmol/l sodium cholate (SC) with 10 mmol/l beta-cyclodextrin in phosphate buffer (pH 10.4). The separation was optimized by adjusting buffer pH, concentrations of beta-cyclodextrin and SC and applied voltage. The proposed method was validated and applied to the determination of two commercial Rhubarb samples. The results obtained were satisfactory.

Anthraquinones↗
PubMed1999

Separation of urea, uric acid, creatine, and creatinine by micellar electrokinetic capillary chromatography with sodium cholate.

The capillary electrophoretic separation of the four nonprotein nitrogenous compounds (NPNs; urea, uric acid, creatine, and creatinine) typically employed in clinical and medical settings for the monitoring of renal function is described. Successful resolution of these compounds is achieved with the use of a bile salt micelle system composed of sodium cholate at phosphate buffer pH 7.4. The elution patterns of four NPNs are obtained within 30 min with a voltage of 30 kV. The effect of varying the applied voltage, temperature, and the mole ratio of phosphate buffer with bile salt surfactant on the migration behavior is also examined.

Chromatography, Micellar Electrokinetic Capillary↗
PubMed2002

Physical properties of phosphatidylcholine vesicles containing small amount of sodium cholate and consideration on the initial stage of vesicle solubilization.

The effects of sub-solubilizing concentrations of sodium cholate (Na-chol) on several physicochemical properties of phosphatidylcholine (PC) small unilamellar vesicles (SUV) were considered in connection with the initial stage of membrane solubilization. ESR spectra of 12-doxylstearic acid (12-DS) in phosphatidylcholine from egg yolk (EPC) or dimyristoylphosphatidylcholine (DMPC) SUV at low concentrations (insufficient to destroy the vesicles) of Na-chol were composed of two (a strongly immobilized and an additional weakly immobilized) immiscible components. The origin of the additional bands was phase separation which occurred in the hydrophobic parts of PC SUV in the presence of Na-chol. Differential scanning calorimetry measurements demonstrated that the mixed DMPC/Na-chol SUV possessed two (a sharp low-temperature and a broad high-temperature) endothermic peaks, which is consistent with the coexistence of two immiscible phases in the vesicular membranes. zeta Potentials of the EPC/Na-chol SUV revealed that high anionic densities appeared on the surfaces of the SUV at a Na-chol concentration slightly below the upper boundary of the vesicle region. Thus, the initial stage of the solubilization of PC SUV by Na-chol was caused by the aggregation of hydrophobic parts of PC membranes, followed by the occurrence of high anionic densities on the surfaces of the vesicles. The fact that removal of Na-chol from PC/Na-chol mixed systems preferentially resulted in the formation of small vesicles might originate from these anionic charges.

Calorimetry, Differential Scanning↗
PubMed2005

Mild hepatic fibrosis in cholesterol and sodium cholate diet-fed rats.

To date, the majority of research on hypercholesterolemia has focused on the effects of a high cholesterol diet on atherosclerosis and coronary heart disease. The toxic effects of cholesterol on the liver and the relationship between the intake of a high cholesterol diet and hepatic fibrosis, however, have not been investigated clearly or histopathologically. Male Wistar rats were fed a diet supplemented with 1.0% cholesterol and 0.3% sodium cholate for 12 weeks. Rats were sacrificed and analyzed via blood biochemistry, traditional microscopy and immunohistochemistry. Following the feeding of this diet, the rates of aspartate aminotransferase, alanine aminotransferase, lactate dehydrogenase and total cholesterol in the rats were elevated consistently from week 3 and throughout the remainder of the experiment. From microscopic observation, hepatic necrosis, macrophage infiltration and steatosis increased markedly throughout the experiment. Hepatic fibrosis and myofibroblast proliferation were detected at weeks 9 and 12. Mast cell appearance was proportional to the degree of hepatic damage. These findings suggest that hepatic fibrosis is inducible by a high cholesterol diet and is likely the result of the interaction between several different cell types (i.e., macrophages, myofibroblasts, and mast cells) in an inflammatory milieu. Hypercholesterolemia should be considered as a risk factor for hepatic fibrosis as well as atherosclerosis and coronary artery disease.

Alanine Transaminase↗
PubMedDate not supplied

Influence of planarity and size on guest binding with sodium cholate aggregates.

Bile salt aggregates are supramolecular structures with two types of binding sites, called primary and secondary sites. The objective of this work was to explore how the nonplanarity and size of guests (biphenyl [BP], 1-1'-binaphthyl [BNP] and dibenz[b,f]oxepin [DBX]) affected their binding affinity and dynamics to sodium cholate (NaC) aggregates. Fluorescence and laser-flash photolysis experiments were performed to obtain information on the binding environment for the guests, the accessibility of quenchers to guests in the aggregate and the dissociation rate constants of the guests from the aggregates. All guests were bound to the more hydrophobic primary aggregate, showing that this site can accommodate nonplanar molecules. However, the structure of the guest affects the structure of the primary aggregates, leading to changes in the accessibility of anions to aggregate-bound guests and to changes for the guest dissociation rate constants from the aggregates.

Binding Sites↗
PubMed1996

Optimization of selectivity and resolution in micellar electrokinetic capillary chromatography with a mixed micellar system of sodium dodecyl sulfate and sodium cholate.

Selectivity and resolution were studied for the separation of seven corticosteroids by micellar electrokinetic capillary chromatography (MEKC) using a mixed micellar solution of sodium dodecyl sulfate (SDS) and sodium cholate (SC), buffered with 3-(N-morpholino)propanesulfonic acid (MOPS) or 3-[(1,1-dimethyl-2-hydroxyethyl)amino]-2-hydroxypropane sulfonic acid (AMPSO). The changes in selectivity were compared for the AMPSO-SDS-SC system by varying the pH and the concentrations of AMPSO, SDS and SC. The experimental design started with the central composite design and continued in a sequential manner. The optimum selectivity for the separation of the corticosteroids was calculated from the analyte migration times and the analyte velocities, by using empirical quadratic regression models. Satisfactory regression fits and coefficients of determination for prediction were obtained with cross-validated models. To optimize the resolution, the physical parameters of capillary length and analysis time were varied under the conditions optimal for the selectivity. In both the selectivity and the resolution, optimization the overall optimum was determined by using the desirability function technique. Analysis times were controlled by using 1,3-diaminopropane to influence the electroosmotic flow velocity (veo). The voltage was kept constant, which resulted in higher electric field strength in shorter capillaries. No changes in the selectivity were observed when 1,3-diaminopropane was used to control the electroosmotic flow velocity. Such an optimization technique, where the chemical and physical factors affecting the separation are treated independently, seemed to be effective for finding the best possible resolution for the corticosteroids.

Adrenal Cortex Hormones↗
PubMed1997

Determination of serum corticosteroids by mixed micellar electrokinetic capillary chromatography with sodium dodecyl sulfate and sodium cholate.

The application of mixed micellar electrokinetic capillary electrochromatography to the determination of the corticosteroid hormones cortisone, cortisol (hydrocortisone), and dexamethasone in serum samples is demonstrated. The serum samples were enzymatically hydrolyzed, precipitated, solid-phase extracted, and analyzed by capillary electrophoresis. A micellar system of sodium dodecyl sulfate and sodium cholate buffered with an organic compound provided the electrolyte solution. Spiked blank serum samples were used for the linearity testing and limits of detection and quantitation were measured. Patient samples were analyzed and the concentrations of cortisol and cortisone were measured. The method, which was fast and easy to perform, was confirmed to be useful for the determination of corticosteroids in serum.

Adrenal Cortex Hormones↗
PubMed1982

Chemical modification of membrane proteins by brominated taurodehydrocholate in isolated hepatocytes; relationship to the uptake of cholate and of phalloidin and to the sensitivity of hepatocytes to phalloidin.

In vitro treatment of isolated rat hepatocytes with brominated taurodehydrocholic acid (BTC) reduced their sensitivity against phalloidin and inhibited the uptake of phalloidin as well as of cholate in an irreversible and concentration dependent manner. BTC was taken up itself by liver cells; this process was inhibited by 4,4'-diisothiocyano 2,2'-stilbene disulfonate (DIDS). When hepatocytes were incubated with 35S-BTC their plasma membranes contained five labeled protein species with molecular weights of 67,000, 49,000, 38,000, 32,000 and 24,000 as shown by SDS-electrophoresis. No marked difference was observed when isolated plasma membranes from livers were directly treated with the affinity label. DIDS suppressed covalent binding of 35S-BTC to membrane components drastically. Incubation of phalloidin insensitive AS-30D ascites hepatoma cells with 35S-BTC did not result in a chemical modification of the above five proteins. This agrees with an earlier observation that hepatoma cells are unable to take up phalloidin and bile acids (Petzinger et al. 1979; Rufeger and Grundmann 1977; Kroker et al. 1978).

Affinity Labels↗
PubMed1980

Protective effect of anionic cholecystographic agents against phalloidin on isolated hepatocytes by competitive inhibition of the phallotoxin uptake. Comparison of the influence on the inward transport of 3H-demethylphalloin and of 14C-cholate.

Several anionic substances used for cholecystography inhibit the development of protrusions in isolated hepatocytes in response to phalloidin. Drugs from the iopodate family were equieffective with those of th iodipamide type. The above protective effect results from a competitive inhibition of the phallotoxin uptake as shown for iopodate. Cholecystographic agents similarly inhibit the inward transport of cholic acid in a competitive manner. The inhibition of the phallotoxin response is inversely correlated with the uptake of 3H-demethylphalloin (r = 0.94) and with the inward transport of cholate (r = 0.84) at various inhibiting concentrations of iopodate.

Alkaloids↗
PubMed1986

Preparation and characterization of unilamellar vesicles from cholate-phospholipid micelle treated with cholestyramine.

Cholestyramine, a well-known bile-salt sequestrant, can be used effectively to remove cholate or deoxycholate from a solution of phosphatidylcholine-bile salt mixed micelle. Upon removal of the bile salt, unilamellar phospholipid vesicles form essentially instantaneously. Cholestyramine resin could be pelleted and removed from the vesicle solution after a low speed centrifugation. Based on phosphate analyses, the recovery of vesicles was approximately 60% of the starting material. The average diameter of these vesicles, as estimated by gel exclusion chromatography on sephacryl S-1000 beads and by trapped volume measurement using [3H]sucrose, ranged between 85 to 121 nm. Phosphatidylethanolamine, cholesterol, or n-alkane such as tetradecane can be incorporated into the vesicles without any selective loss; however, selective loss was experienced when negatively charged phospholipid species such as phosphatidylglycerol or phosphatidylserine was included in vesicle formation.

Cholestyramine Resin↗
PubMed1992

The size dependence of cholate-dialyzed vesicles on phosphatidylcholine concentration.

The size dependence of vesicles prepared by dialysis of cholate from phosphatidylcholine (PC) dispersions has been investigated as a function of lipid concentration (at a constant applied lipid: detergent molar ratio of 0.7). Gel filtration of dialyzed samples produced a symmetrical profile shape, although quasielastic laser light scattering analysis of the fractions revealed an asymmetrical range of sizes about the peak for solutions containing elevated lipid concentrations. Vesicle diameters increased by approximately 20 nm for PC concentrations ranging from 10 to a maximum of 45 mg/ml. This was attributed to mixed micelle sizes being proportional to lipid concentration, since the diameters of vesicles produced from dialysis are determined by mixed micelle sizes. Before commencement of dialysis, mixed micelle sizes are proportional to lipid concentration and, although dialysis causes an increase in mixed micelle sizes, the phase ratios attained are larger for solutions containing elevated lipid concentrations.

Cholic Acid↗
PubMed1983

Pancreatic porcine phospholipase A2 catalyzed hydrolysis of phosphatidylcholine in lecithin-bile salt mixed micelles: kinetic studies in a lecithin-sodium cholate system.

Pancreatic porcine phospholipase A2 catalyzed hydrolysis of phosphatidylcholine in bile salt lecithin mixed micelles has been studied, utilizing a series of assay mixtures for which the micellar size, weight, and composition had been experimentally determined. Under these conditions the enzymatic hydrolysis is dependent on the phosphatidylcholine-to-sodium cholate molar ratio within the mixed micelle rather than the bulk concentration of the phospholipid in the mixture: at 5 mM phosphatidylcholine, variation of the NPC/NNaCh ratio from 0.2 to 2.0 increases the enzymatic activity from 82 to 933 mumol/min/mg protein. The initial rates are linear throughout the entire series of assay mixtures, the activity vs micellar concentration curves exhibit saturation behavior, and treatment of the data according to the "surface-as-cofactor" theory provides linear double-reciprocal plots which intersect in one point. The assay system should be applicable for detailed kinetic studies of lipolytic enzymes, including mammalian phospholipases which exhibit rather low activities toward lecithin-Triton X-100 mixed micelles. The system should also provide a convenient basis for mechanistic studies involving the use of inhibitory phospholipid substrate analogs.

Animals↗
PubMed1984

An X-ray diffraction and electron microscopy study of the extraction of erythrocyte membranes with the bile salt, cholate.

Studies by X-ray diffraction and electron microscopy of slowly frozen samples of control and cholate-extracted preparations of erythrocyte membranes have demonstrated changes in structural parameters which can readily be related to the extraction of cytoskeletal proteins. In the frozen state, these components appear to be condensed to about 10% of the total membrane thickness. The observations illustrate some of the advantages and limitations in the use of slowly frozen membrane preparations in studies of membrane structure.

Cell Fractionation↗
PubMed1983

Stimulation of hepatic phosphatidylcholine biosynthesis in rats fed a high cholesterol and cholate diet correlates with translocation of CTP: phosphocholine cytidylyltransferase from cytosol to microsomes.

A new model system for the study of phosphatidylcholine biosynthesis is presented. Young rats were fed a diet that contained 5% cholesterol and 2% cholate. After 6 days there was a 2-fold increase in the concentration of plasma phospholipid (243 mg/dl compared to 132 mg/dl for control animals) and a 3-fold increase in the concentration of plasma phosphatidylcholine. The rate of phosphatidylcholine biosynthesis was measured after injection of [Me-3H]choline into the portal veins. The incorporation of tritium into choline, phosphocholine and betaine by liver was similar for experimental and control animals, whereas there was a 3-fold increased incorporation into phosphatidylcholine of the cholesterol/cholate-fed rats. The activities of the enzymes of phosphatidylcholine biosynthesis in cytosol and microsomes were assayed. The only change detected was in the cytosolic and microsomal activities of CTP: phosphocholine cytidylyltransferase which were increased more than 2-fold in specific activity. When total cytidylyltransferase activity per liver was determined, a dramatic translocation of the enzyme to microsomes was observed. The control livers had 24% of the cytidylyltransferase activity associated with microsomes, whereas this value was 61% in the livers from cholesterol/cholate-fed rats. When the cytosolic cytidylyltransferase was assayed in the presence of phospholipid, the enzyme was stimulated several-fold and the difference in specific activity between control and cholesterol/cholate-fed rats was abolished. The increased activity in cytosol appears to be the result of a 2-fold increase in the amount of phospholipid in the cytosol from cholesterol/cholate-fed rats. The data strongly support the hypothesis that the special diet stimulates phosphatidylcholine biosynthesis by causing a translocation of the cytidylyltransferase from cytosol to microsomes where it is activated.

Animals↗
PubMed1988

Sodium cholate extraction of rat liver nuclear xenobiotic-metabolizing enzymes.

DNA is the purported target of several carcinogenic and mutagenic agents. Nuclear enzymes which could generate or detoxify reactive metabolites are of major concern. Several such enzymes have been identified within nuclei, but obtaining samples with enriched content or activity is difficult, time-consuming, and uses harsh isolation techniques. Extraction of rat liver nuclear suspensions with cholate-containing buffer results in solubilization of 25-30% of the protein. Linear extraction was obtained for total protein and cytochromes P-450 and b5, NADPH-cytochrome P-450 reductase, NADH-cytochrome b5 reductase, DT-diaphorase, and microsomal-like epoxide hydrolase with specific activities comparable to values reported for isolated nuclear membrane, while the yield was five to ten times greater. Detergent extracts of rat liver nuclei were employed to study the comparative response of microsomal and nuclear enzymes to chemical treatment. While the responses to acute inductive (phenobarbital and 3-methylcholanthrene) and toxic (carbon tetrachloride and dibromochloropropane) treatments were qualitatively similar, an initiation-promotion protocol (diethylnitrosamine with phenobarbital promotion) resulted in divergent responses between the enzymes in the two subcellular fractions. Detergent extracts of nuclei offer an efficient means of recovering xenobiotic-metabolizing enzymes from rat liver nuclei, and have been utilized to demonstrate a differential response of nuclear enzymes during preneoplastic development.

Animals↗