Location and ion-binding of membrane-associated valinomycin, a proton nuclear magnetic resonance study

Valinomycin, incorporated in small unilamellar vesicles of perdeuterated dimyristoylphosphatidylcholine, reveals several well-resolved 1H-NMR resonances. These resonances were used to examine the location, orientation and ion-binding of membrane-bound valinomycin. The order of affinity of membrane-bound valinomycin for cations is Rb+ greater than K+ greater than Cs+ greater than Ba2+, and binding is sensitive to surface change. The exchange between bound and free forms is fast on the NMR time scale. The intrinsic binding constants, extrapolated to zero anion concentration, are similar to those determined in aqueous solution. Rb+ and K+ show 1:1 binding to valinomycin, whereas the stoichiometry of Cs+ and Ba2+ is not certain. Paramagnetic chemical shift reagents and nitroxide spin label relaxation probes were used to study the location and orientation of valinomycin in the membrane. Despite relatively fast exchange of bound cations, the time average location of the cation-free form of valinomycin is deep within the bilayer under the conditions of these experiments. Upon complexation to K+, valinomycin moves closer to the interfacial region.

Cell membrane abnormality detected in erythrocytes from patients with multiple sclerosis by partition in two-polymer aqueous-phase systems

Erythrocytes from multiple sclerosis patients differ significantly (p less than 0.005) from those from controls with regard to hydrophobic affinity partition in two-polymer aqueous-phase systems containing dextran, poly(ethylene glycol) and poly (ethylene glycol)-fatty acid esters. The most likely source of the abnormality is the cell membrane.

Tensile strengths and hardness of tablets

The axial and radial tensile strengths were compared to the hardness of compressed tablets containing various concentrations of lubricants. Since radial tensile strength measurement considers the thickness of a tablet, and only tensile stress and axial tensile strength express the strength in the direction in which capping may occur, the tensile strengths characterize the strength of a tablet more completely than hardness.

Temperature dependence of dipalmitoyl phosphatidylcholine monolayer stability

Dipalmitoyl phosphatidylcholine is the principal component of lung surfactant, and knowledge of its behavior as a film spread at the air-water interface is essential for understanding how lung surfactant itself works. We therefore studied the collapse rates of very low surface tension air-water monolayers of dipalmitoyl, dimyristoyl, and palmitoyl-myristoyl phosphatidylcholines at different temperatures. In each case we found that the monolayers abruptly became unstable at temperature 3-4 degree C above their bulk lipid-water phase transition temperatures (Tc). This accords with a comparable increase in Tc occurring in bulk systems subjected to high pressure. These findings are also consistent with the behavior of isolated rat lungs, which have been found to require higher transmural pressures to maintain a given volume on deflation when kept at temperature above the Tc of dipalmitoyl phosphatidylcholine.

[Preparation of patients in diagnostic contrast radiography of the urinary and bile tracts and the large intestine]

A preparation schedule including, for clysterisation, a substance based on palmitate, stearate and oleate of sodium of vegetable origin has been experimented in 130 patients of both sexes (70 awaiting contrastography of the urinary and bile ways, and 60 double contrastography of the colon). Excellent results were obtained in urography and colangiocholecystography when the schedule was limited to just one clyster with double dose of Radioced carried out on the same morning as the investigation. For an examination like double contrast clyster, which is more demanding from the viewpoint of correct intestinal cleansing, the number of clysters has to be increased to four. Three, at appropriate intervals, are carried out on the day preceding examination, and the last no more than two hours prior to the clyster. In all four, a double dose of Radioced dissolved in warm water (two litres for each of the first three and a litre and a half for the fourth) is used. Still on double contrast clyster, the preparation schedule requires a three-day diet (the first two involving low-waste foods and the third a liquid diet only) plus 30 g of Epsom salts (and no less than a litre of water) the day before double contrastography.

Physicochemical properties of magnesium salicylate

Magnesium salicylate tetrahydrate is a nonhygroscopic, crystalline powder, whereas anhydrous magnesium salicylate is amorphous and very hygroscopic. Magnesium salicylate tetrahydrate tablets formulated with gelatin as a binder showed a dissolution half-life (t1/2) of 12 min, whereas a formulation using pregelatinized starch as a binder showed a t1/2 of 33 min. The optimum level of calcium stearate in the formulation was determined by the oscilloscope tracings of compressional and ejectional forces from an instrumented rotary tableting machine. Increasing the level of calcium stearate from 1 to 1.5 and 2% resulted in dissolution t1/2 values of 12, 18, and 21 min, respectively, and a higher incidence of softer tablets and capping.

A study of changes in surface area and molecular interactions in phospholipid vesicles by condensed phase radioluminescence

(1) The radioactive decay of tritium was used to excite 12-(9-anthroyloxy)-stearic acid. The resulting radioluminescence was observed by single-photon counting. A signal can only be observed if the emitting tritium is close enough to the absorbing fluorophore. This is accomplished by condensing the emitter and absorber into a lipid membrane. Therefore, we call the technique Condensed phase radioluminescence (CPR). (2) We present the theoretical background for the observed CPR signals. (3) We observed a large CPR signal when tritiated oleic acid was added to 12-(3-anthroyloxy)stearic acid micelles. (4) The phase transition of dimyristoyl phosphatidylcholine and dipalmitoyl phosphatidylcholine in unilamellar vesicles can be monitored with CPR, and the relative intensity change observed is directly related to the relative surface change at the centre of the bilayer. (5) Oleic acid and 12-(9-anthroyloxy)stearic acid exchange between dimyristoyl phosphatidylcholine and dipalmitoyl phosphatidylcholine vesicles. The labels show no real preference for the fluid phase of the dimyristoyl phosphatidylcholine vesicles. (6) CPR is a powerful method for studying distance and binding relationships in membranes.

Plasma and sputum erythromycin concentrations in chronic bronchitis

Plasma and sputum concentrations of erythromycin were measured in 10 patients with chronic bronchitis during an eight-day course of a new formulation of erythromycin stearate. The plasma erythromycin levels compared favourably with the minimal inhibitory concentrations for common respiratory pathogens and indicated adequate gastrointestinal absorption when the drug was taken immediately before food. Sputum erythromycin levels were variable and in some patients low or undetectable. Measurable sputum erythromycin levels were approximately 10% of plasma levels with no evidence of accumulation and were of similar order of magnitude to the minimal inhibitory concentrations for common respiratory pathogens except Haemophilus influenzae. There was no correlation between sputum and plasma erythromycin levels. There was a trend for higher erythromycin levels in sputum containing increasing amounts of pus and also when plasma levels increased.

Solid dispersion of morphine-tristearin with reduced presystemic inactivation in rats

Solid dispersions of morphine in tristearin, beta-sitosterol, and cholesterol were prepared by evaporation of their ethanol solutions. Weight ratios of morphine-lipid of 1:1, 1:3, and 1:4.5 were prepared. Dissolution studies of the solid dispersions and morphine were conducted in a simulated GI medium at 37 degrees. The release rates of morphine from the tristearin dispersions were the slowest. The 1:1 morphine-tristearin dispersion was administered orally to rats. Free and total morphine levels in rat urine were determined by spectrofluorometric and enzymatic immunoassay procedures, respectively. The morphine-tristearin dispersion yielded a higher percentage of free morphine after 24 and 48 hr as compared with morphine and its sulfate.

beta-Oxidation of the coenzyme A esters of elaidic, oleic, and stearic acids and their full-cycle intermediates by rat heart mitochondria

beta-Oxidation rates for the CoA esters of elaidic, oleic and stearic acids and their full-cycle beta-oxidation intermediates and for the carnitine esters of oleic and elaidic acids were compared over a wide range of substrate and albumin concentrations in rat heart mitochondria. The esters of elaidic acid were oxidized at about half the rate of the oleic acid esters, while stearoyl-CoA was oxidized equally as rapid as oleoyl-CoA. The full-cycle beta-oxidation intermediates of elaidoyl-CoA (trans-16 : 1 delta 7, -14 : 1 delta 5, and -12 : 1 delta 3) were found to be oxidized at rates nearly equal to those for the corresponding intermediates of oleoyl-CoA. Therefore, after the first cycle of beta-oxidation, oleoyl-CoA and elaidoyl-CoA are oxidized at nearly equal rates. The activity of fatty acyl-CoA dehydrogenase was higher with elaidoyl-CoA and its full-cycle intermediates as substrates than with the corresponding cisisomers. It was concluded that the slower oxidation rate of elaidic acid is not due to slower oxidation of any of its full-cycle beta-oxidation intermediates, nor to slower activity of fatty acyl-CoA dehydrogenase, nor to outer mitochondrial carnitine acyltransferase. Possible explanations to account for the slower oxidation rate of elaidic acid are discussed.

Electrical conductance of directly compressible materials under pressure

An electrometer that allowed direct recording of resistance changes during compression was used to measure the conductances of sodium chloride, potassium chloride, ammonium chloride, and sodium citrate. The effects of initial particle size, lubricant level, moisture content, and compaction pressure were determined. Direct compression tableting diluents also studied were dextrose, sucrose, lactose, microcrystalline cellulose, and dibasic calcium phosphate. Distinctive conductance patterns were observed and are rationalized in terms of previously proposed bondign machanisms.

Effect of microcrystalline cellulose on liquid penetration in and disintegration of directly compressed tablets

The penetration of isooctane and water into tablets of microcrystalline cellulose, dibasic calcium phosphate dihydrate, spray-crystallized maltose-dextrose, and blends of microcrystalline cellulose with one of the other excipients were studied. The isooctane penetrations occurred according to the Washburn equation and were not affected by the presence of 0.5 or 1.0% magnesium stearate. The inhibition of aqueous penetration into tablets resulting from hydrophobic magnesium stearate was less pronounced for vehicles like dibasic calcium phosphate, which exhibited extensive brittle fracture under compression. Microcrystalline cellulose tablets, both with and without magnesium stearate, exhibited extremely fast aqueous penetration even at low porosities, caused by breaking of the hydrogen bonds and subsequent widening of the pores. Ratios between water uptake and original pore volume up to 20 were obtained for microcrystalline cellulose tablets. This unique property was, however, suppressed by the presence of fast dissolving and highly soluble excipients like dextrose, resulting in an antagonistic disintegration behavior of tablets compressed at pressures over 10,000 N/cm2. Improved disintegration properties were obtained by blending microcrystalline cellulose with an insoluble vehicle such as dibasic calcium phosphate dihydrate.

Clinical and pharmacological evaluation of different preparations of oral erythromycin

The activity of erythromycin stearate in respiratory tract infections was evaluated. This study involved 269 out-patients. Of these, 76 satisfied the strict criteria for detailed bacteriological study with positive cultures of a known pathogen before treatment and bacteriological follow-up after treatment. The results of erythromycin stearate were good against the haemolytic streptococcal infections. The activity of this antibiotic was shown to be insufficient against Haemophilus influenzae. A second clinical trial with 20 patients with acute exacerbations of chronic bronchitis demonstrated quite good activity from erythromycin ethylsuccinate and no intolerance when administered in a dose of 1 g q.i.d. The administration of 1 g of the ethylsuccinate immediately after a meal gave a peak serum concentration after 60 min of 3.36 micrograms/ml. Blood levels on the fourth day of this treatment showed some accumulation, concentrations of greater than 4 micrograms/ml being found at 30, 60 and 90 min after the dose. With its good absorption, its lack of toxicity and its reputation for good diffusion into bronchial secretions, we consider that erythromycin ethylsuccinate should have a major place in the treatment of respiratory tract infections.

Studies on cephalopod rhodopsin. Fatty acid esters of sucrose as effective detergents

Squid rhodopsin was extracted with solutions of fatty acid esters of sucrose (monolaurate and monostearate) and purified by DEAE-cellulose and concanavalin A-Sepharose affinity chromatography. The purified rhodopsin (A280/A480 = 2.5) contained 2.3 mol of glucosamine and 1.2 mol of phospholipid per mol of rhodopsin. The photoproduct metarhodopsin was also stable in these detergent solutions as in digitonin solution. Concanavalin A had no affinity for retinochrome.

Multiple phase equilibria in binary mixtures of phospholipids

Approximate phse diagrams describing lateral phase separations are given for binary mixtures of dimyristoyl phosphatidylcholine with dipalmitoyl phosphatidylcholine, distearoyl phosphatidycholine, and dipalmitoyl phosphatidylethanolamine. These diagrams are based in part on freeze-fracture electron microscopic data. These phase diagrams represent an improvement over previous studies in that both solid phses (Pbeta' and Lbeta') of the phosphatidylcholines are included. Further consideration is given to the problem of binary mixtures in which there are two Pbeta' phases that do not form a continuous range of solid solutions.