Conformational analysis of 6-cis- and 6-trans-leukotriene B4-calcium complexes.

We present a computational description of the conformation of a pair of two isomeric molecules (6-cis-and 6-trans-leukotriene B4) forming a complex with one calcium ion. Our theoretical prediction of the membrane-water interface conformation and of the bulk lipid phase conformation of the two different isomeric complexes are in excellent agreement with experimental data on the leukotriene-mediated calcium ionophoresis in liposomes. The two isomers lead to vastly different conformations in the presence of Ca2+, and the most probable conformation of the permeant species shows a globular conformation able to cross a lipid membrane

The effect of Ca

31P NMR spectra of phosphatidylcholine-cardiolipin mixed liposomes were obtained as a function of Ca++ and Zn++ concentration for different temperatures. The ions induce non lamellar phases in this model membrane and it was observed that Zn++ is a better promotor of isotropic and hexagonal H11 phases than Ca++. The NMR observations can be correlated to the fusogenic power of these ions

Nutrient-induced changes in the pH of pancreatic islet cells.

Fluorescein rapidly accumulates in rat pancreatic islets exposed to fluorescein diacetate. The influence of environmental agents upon cellular pH was examined in fluorescein-labelled islets by recording their fluorescence intensity at 520 nm after excitation at 490 and 435 nm, respectively. Glucose caused a rapid, sustained and dose-related increase in cellular pH. Another nutrient secretagogue, 2-ketoisocaproic acid, also increased cellular pH. The stimulation of islet cells by non-nutrient secretagogues, e.g. by glibenclamide or in response to an increase in extracellular K+ concentration, decreased cellular pH, indicating that the nutrient-induced increase in cellular pH is not merely a consequence of stimulated Ca2+ inflow and/or insulin release. In either the presence of amiloride or absence of bicarbonate, glucose decreased cellular pH. These results strongly suggest that the acidification of islet cells which can be expected from the increased metabolism of glucose in glucose-stimulated islets is normally masked and overcome by stimulation of such processes as Na+/H+ and HCO3-/Cl- exchange.In VitroJournal ArticleResearch Support, Non-U.S. Gov'tinfo:eu-repo/semantics/publishe

Effects of cations, ionophores and hypoglycemic sulfonylureas on the fluorescence of fluorescein-labelled pancreatic islets.

The stimulation of Ca2+ inflow into pancreatic islet cells resulting from either an increase in extracellular K+ (from 5 to 37 mM) or Ca2+ (from 1 to 20 mM) concentration or the administration of tolbutamide, glibenclamide and the ionophores A23187 or X537A resulted in an apparent fall of cellular pH as judged from the fluorescence of islets prelabelled with fluorescein diacetate. In all cases, the decrease in pH was abolished when the experiments were repeated in the absence of extracellular Ca2+. These results suggest that the cytosolic concentration of Ca2+ may affect the pH of islet cells, possibly by displacing H+ from intracellular binding sites.Journal ArticleResearch Support, Non-U.S. Gov'tinfo:eu-repo/semantics/publishe

The Effect of Ca++ and Zn++ Ions On the Polymorphism and the Fusion of Model Membranes

P-31 NMR spectra of phosphatidylcholine-cardiolipin mixed liposomes were obtained as a function of Ca++ and Zn++ concentration for different temperatures. The ions induce non lamellar phases in this model membrane and it was observed that Zn++ is a better promotor of isotropic and hexagonal H(II) phases than Ca++. The NMR observations can be correlated to the fusogenic power of these ions

Tablet comprising cetirizine and pseudoephedrine

The present invention concerns a tablet comprising two distinct segments. More particularly the invention relates to combinations of two pharmaceutical substances and methods of treatment of allergic disorders.info:eu-repo/semantics/publishe

Piracetam-induced changes to membrane physical properties. A combined approach by 31P nuclear magnetic resonance and conformational analysis.

Piracetam, Nootropil (2-oxo-1-pyrrolidine acetamide), is a drug promoting erythrocyte deformability. To establish the mode of action of this compound, we have investigated its influence on the organization of model phospholipid membranes. 31P NMR data show that the drug induces a structural modification in liposomes made of phosphatidylcholine and phosphatidylethanolamine. Our conformational analysis results have allowed the interpretation of the effect of piracetam on these model membranes: the specific interaction between the drug molecules and the phosphate headgroups induces a new organization of the lipids favouring formation of mobile drug-phospholipid complexes that exhibit an isotropic-type signal in the 31P NMR spectra.Journal ArticleResearch Support, Non-U.S. Gov'tinfo:eu-repo/semantics/publishe

Glucose-induced membrane fluidification in endocrine pancreatic cells

SCOPUS: ar.jinfo:eu-repo/semantics/publishe