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Biomedical subjects

B Lundberg

Publications and source records attributed to B Lundberg.

At least 73 records · Page 4Linked to original sources
PubMed1979

Effect of substrate properties on the activity of lysosomal cholesteryl ester hydrolase.

The effects of the substrate properties on the catalytic activity of lysosomal cholesteryl ester hydrolase from rat liver have been examined with three standard substrate types: vesicle, micelle and emulsion. The pH optimum of the enzyme coincided to 4.5--5.0 with the substrate types employed. The apparent Km values were 15.3, 14.3 and 7.3 microM for vesicle, micelle and emulsion substrates, respectively. In the systems used in this study reaction products, cholesterol and oleic acid, and the nonionic surfactant Tween 80 and Triton X-100 Had an inhibitory effect. The emulsifier phosphatidylcholine and the charged phospholipid phosphatidic acid stimulated the activity. The mixed micelle of sodium taurocholate and phosphatidylcholine was the most potent substrate vehicle. With dipalmitoyl phosphatidylcholine vesicles the enzyme showed maximal activity at the gel-liquid-crystalline transition temperature of the phospholipid. The possible physiological significance of the lysosomal cholesteryl ester hydrolase is discussed with special reference to the form of the substrate.

Animals↗
PubMed1979

Simultaneous solubilization of steroid hormones II: androgens and estrogens.

The simultaneous solubilization of some androgens and estrogens in aqueous polysorbate 40, tetradecyltrimethylammonium bromide, and sodium lauryl sulfate was studied. The solubilizations of estradiol and testosterone were independent of each other in all three association colloids. However, if the estrogen component was ethinyl estradiol, the solubilization was dependent on the addition order. The estrogen precipitates more readily than testosterone in polysorbate 40 and tetradecyltrimethylammonium bromide, but the opposite is true in sodium lauryl sulfate. The simultaneous solubilizations of methyltestosterone or ethisterone with the estrogens tested were different from those of testosterone. The solubilization behavior of the steroids is discussed, starting with the pseudophase model and different solubilization loci. Results indicated that the free energy change of micellar binding, delta Gb, decreases with increased steroid polarity. The simultaneous solubilization cannot be predicted by delta Gb but may be explained by differences in the solubilization mechanism.

Androgens↗
PubMed1978

Simultaneous solubilization of steroid hormones I: estrogens and C21 steroids.

The simultaneous solubilization of some estrogens and C21 steroids in aqueous polysorbate 40, tetradecyltrimethylammonium bromide, and sodium lauryl sulfate was studied. The less soluble estrogen estradiol was solubilized independently of the C21 steroids. The micellar solubilities of ethinyl estradiol and both corticosterone and hydrocortisone were independnet of the presence of each other while the solubility of 11alpha-hydroxyprogesterone was enhanced by ethinyl estradiol. The solubilizations of ethinyl estradiol and the two C21 steroids, progesterone and 21-hydroxyprogesterone, were dependent on each other so that a varying amount of the steroid solubilized first was precipitated by an excess of the second steroid. If saturated solutions of the two steroids were mixed, no precipitation occurred. A possible mechanism for the simultaneous solubilization of steroids and its relation to structure are discussed.

Chemistry, Pharmaceutical↗
PubMed1978

The hydration of phospholipids and phospholipid-cholesterol complexes.

The hydration characteristics of phosphatidylcholines and the effect of cholesterol on these were studied with differential thermal analysis and water vapour adsorption experiments. Also the water adsorption of egg phosphatidylethanolamine and the effect of cholesterol on this was studied and compared with corresponding qualities of phosphatidylcholine. The differential thermal analysis study showed that the monohydrates of egg, dipalmitoyl, and dioleoyl phosphatidylcholine tightly bind approximately 9 molecules of water per phosphatidylcholine molecule. Cholesterol is proved to somewhat increase the water binding of the phospholipids. Cholesterol is also shown to decrease the heat change of the chain melting transition of dioleoyl phosphatidylcholine, but not to abolish it completely. The water adsorption experiments indicate that the hydration of phosphatidylcholines takes place in two steps; a strong initial water binding and a second phase of weak binding. The adsorption isotherm of egg phosphatidylethanolamine is strikingly different from that of egg phosphatidylcholine. Cholesterol is shown, also by this method, to increase the hydration of phospholipids especially that of dipalmitoylphosphatidylcholine. The results in this study are in good agreement with those presented by many other authors. Starting with the accumulated information of the hydration characteristics of phosphatidylcholines the organization of the bound water around the polar group is discussed and the most probable model is evaluated.

Adsorption↗
PubMed1977

Properties of mixed vesicles of lecithin: cholesterol up to a 1:2 molar ratio.

The cholesterol solubilizing capacity of lecithin vesicles was studied and some physicochemical properties of the resulting mixed vesicles were investigated. The maximum association of ultrasonicated cholesterol and lecithin was found to be a cholesterol/lecithin molar ratio of 2:1, with a limiting concentration of colloidal lipid of approximately 34 mg/ml. The 2:1 dispersions were found to be rather stable with no change in cholesterol/lecithin ratios for long periods. The mixed 2:1 cholesterol/lecithin vesicles were separated by Sepharose 4 B chromatography to obtain homogeneous preparations. The homogeneity was further tested by analytical ultracentrifugation and electron microscopy. Light-scattering measurements showed an increase in particle weight with increasing cholesterol proportion. 1H-and 13C-NMR studies demonstrated an additional broadening, especially of chain resonances, when going from a cholesterol/lecithin molar ratio of 1:1 to 2:1.

Cholesterol↗
PubMed1976

Thermal properties of systems containing cholesteryl esters and triglycerides.

Binary and ternary systems of the three cholesteryl esters, linoleate, oleate, and stearate and the two triglycerides, triolein and tristearin were studied in order to determine the phase transitions and the conditions for the cholesteric and smectic mesophases. Phase transitions were determined using differential thermal analysis, melting point determination, and polarizing microscopy. Of the cholesterol esters the linoleate-oleate system showed complete miscibility in both the liquid and solid phases. The linoleate-stearate and oleate-stearate systems are of the eutectic type with limited solid solubility. The mesophases are monotropic as to the crystalline state and exist over the entire composition interval in all cholesteryl ester systems studied.

Chemical Phenomena↗