Search results for "Cholin"
showing 10 items of 1261 documents
A Study of Lipid-Lipid and Lipid-Polypeptide Interactions by High Performance Liquid Chromatography
1984
Abstract Ternary systems containing phosphatidylcholine-cholesterol, phosphatidylcholine-gramicidin A or cholesterol-gramicidin A in tetrahydrofuran have been examined by high performance liquid chromatography. Preferential solvation of cholesterol and especially gramicidin A by phosphatidylcholine is observed. These results are interpreted in terms of hydrophobic interactions between membrane components.
Screening of acetylcholinesterase inhibitors by CE after enzymatic reaction at capillary inlet.
2009
In this study the development of a procedure based on capillary electrophoresis after enzymatic reaction at capillary inlet methodology for the screening and in vitro evaluation of the biological activity of acetylcholinesterase (AChE) inhibitors is presented. The progress of the enzymatic reaction of the hydrolysis of acetylthiocholine at pH 8 in the presence of AChE and the inhibitor studied is determined by measuring at 230 nm the peak area of the reaction product thiocholine (TCh). In the method employed the capillary was first filled with 30 mM borate-phosphate buffer (pH 8.0) and subsequently, plugs of: (i) water, (ii) AChE solution, (iii) substrate solution with or without inhibitor,…
FT-IR investigation of the urea state in lecithin and sodium bis(2-ethylhexyl)phosphate reversed micelles
2003
Abstract FT-IR spectra of urea/lecithin/CCl4 and urea/sodium bis(2-ethylhexyl) phosphate (NaDEHP)/CCl4 systems as a function of the urea-to-surfactant molar ratio (Rurea) at a fixed surfactant concentration (0.1 mol kg−1) have been recorded at 25 °C. Analysis of the absorption spectra leads the to hypothesis that urea is confined within the hydrophilic micellar core of lecithin and NaDEHP reversed micelles. The encapsulation of urea involves some changes of the urea NH stretching band with respect to that of the pure solid urea, attributable to confinement effects. The stretching modes of the surfactant head group are affected by the presence of urea, indicating specific urea-surfactant hea…
Atropine-resistant effects of the muscarinic agonists McN-A-343 and AHR 602 on cardiac performance and the release of noradrenaline from sympathetic …
1974
Abstract 1 The effects of 4-(m-chlorophenylcarbamoyloxy)-2-butynyltrimethylammonium chloride (McN-A-343) and N-benzyl-3-pyrrolidyl acetate methobromide (AHR 602) on cardiac performance and noradrenaline release from terminal sympathetic fibres were measured in isolated perfused hearts of rabbits. 2 In the presence of sufficient atropine to block muscarinic receptors, high concentrations of McN-A-343 and AHR 602 caused no cardiac stimulation and there was no increase in the resting output of noradrenaline into the perfusates. 3 McN-A-343 and AHR 602 increased both the mechanical responses and the transmitter overflow evoked by electrical stimulation of the sympathetic nerves (SNS) but inhibi…
Effects of the Phosphodiesterase Inhibitor Enoximone on the Autonomic Innervation of the Isolated Heart
1989
Enoximone is a selective inhibitor of a low Km, cyclic AMP-specific type of phosphodiesterase (PDE III). In guinea pig and chicken atria, enoximone (0.1-100 mumol/L) caused a weak increase in the force of contraction. The heart rate was slightly enhanced or was unchanged (chicken). Enoximone (30 mumol/L) also failed to shift the concentration-response curves for the positive inotropic and chronotropic effects of norepinephrine in guinea pig atria. Under almost the same conditions, enoximone and the nonselective PDE inhibitor 3-isobutyl-1-methylxanthine (IBMX) markedly potentiated the forskolin-induced mobilization of choline from phospholipids. The concentrations of IBMX (100 mumol/L) and o…
Ouabain enhances release of acetylcholine in the heart evoked by unilateral vagal stimulation.
1986
The aim of the study was to elucidate peripheral effects of ouabain on the parasympathetic innervation of the heart, effects that could contribute to the experimentally and clinically well established “vagal effect of cardiac glycosides”. The experiments were carried out with ouabain concentrations of 3×10−7 and 10−6 mol/l, which were considered “therapeutic”, as they increased force of contraction and did not elicit arrhythmias in incubated chicken atria. In atrial preparations of chickens and guinea-pigs the negative chronotropic and inotropic effects of acetylcholine (ACh) were not altered by 3×10−7 mol/l ouabain. Resting efflux of ACh from perfused chicken hearts was increased by ouabai…
Structural characterisation of the natural membrane-bound state of melittin: a fluorescence study of a dansylated analogue
1997
Abstract The binding of a dansylated analogue of melittin (DNC–melittin) to natural membranes is described. The cytolytic peptide from honey bee venom melittin was enzymatically labelled in its glutamine-25 with the fluorescent probe monodansylcadaverine using guinea pig liver transglutaminase. The labelled peptide was characterised functionally in cytolytic assays, and spectroscopically by circular dichroism and fluorescence. The behaviour of DNC–melittin was, in all respects, indistinguishable from that of the naturally occurring peptide. We used resonance energy transfer to measure the state of aggregation of melittin on the membrane plane in synthetic and natural lipid bilayers. When bo…
HPLC study on the ‘history’ dependence of gramicidin A conformation in phospholipid model membranes
1989
AbstractA novel HPLC methodology for the study of gramicidin A reconstituted in model membranes has been tested in comparison with circular dichroism data. It is shown that this chromatographic technique not only corroborates most of the recent spectroscopic results but allows one to explain them in terms of mass fractions of different actual conformational species of GA in the phospholipid assemblies. In particular, the dependence of the inserted peptide configuration on the organic solvent and other parameters involved in the ‘history’ of the sample preparation and handling has been analyzed by HPLC in two phospholipid model systems: small unilamellar vesicles and micelles. Moreover, a sl…
Environment- and sequence-dependent modulation of the double-stranded to single-stranded conformational transition of gramicidin A in membranes.
1998
The role of the membrane lipid composition and the individual Trp residues in the conformational rearrangement of gramicidin A along the folding pathway to its channel conformation has been examined in phospholipid bilayers by means of previously described size-exclusion high-performance liquid chromatography HPLC-based strategy (Bano et al. (1991) Biochemistry 30, 886). It has been demonstrated that the chemical composition of the membrane influences the transition rate of the peptide rearrangement from double-stranded dimers to beta-helical monomers. The chemical modification of Trp residues, or its substitution by the more hydrophobic residues phenylalanine or naphthylalanine, stabilized…
Cellular Mechanisms of Subplate-Driven and Cholinergic Input-Dependent Network Activity in the Neonatal Rat Somatosensory Cortex
2008
Early coordinated network activity promotes the development of cortical structures. Although these early activity patterns have been recently characterized with respect to their developmental, spatial and dynamic properties, the cellular mechanisms by which specific neuronal populations trigger coordinated activity in the neonatal cerebral cortex are still poorly understood. Here we characterize the cellular and molecular processes leading to generation of network activity during early postnatal development. We show that the somatosensory cortex of newborn rats expresses cholinergic-driven calcium transients which are synchronized within the deeply located subplate. Correspondingly, endogen…