Search results for "Cholin"

Noncompetitive agonism at nicotinic acetylcholine receptors; functional significance for CNS signal transduction.

1995

The alkaloids (-)physostigmine (Phy), galanthamine (Gal) and codeine (Cod), and several derivatives and homologous compounds, can act as noncompetitive agonists (NCA) of nicotinic acetylcholine receptors (nAChR) from Torpedo electrocytes, frog and mammalian muscle cells, clonal rat pheochromocytoma cells, cultured hippocampal neurons and several ectopic expression systems, by interacting with a binding site on the alpha-subunits of these nAChRs that is insensitive to the natural transmitter, acetylcholine (ACh), and ACh-competitive agonists and antagonists. Several endogenous ligands, including opioid-type compounds, can also act via this site, albeit at higher concentrations than is typica…

A novel cholinergic-specific antigen (Chol-2) in mammalian brain.

1993

Three new antisera have been raised in sheep against cholinergic electromotor presynaptic plasma membranes prepared from the electric organs of the electric ray, Torpedo marmorata. They all recognized one or more cholinergic-specific antigens in the mammalian nervous system by the following criteria: they sensitized the cholinergic subpopulation of rat-brain synaptosomes--and only this subpopulation--to lysis by the complement system and, in an immunocytochemical study, selectively stained choline acetyltransferase-positive cholinergic neurons in the rat spinal cord. However, two of the three antisera failed to recognize Chol-1 alpha and -beta, two closely related minor gangliosides already…

Nicotinic receptor function in the mammalian central nervous system.

1995

The diversity of neuronal nicotinic receptors (nAChRs) in addition to their possible involvement in such pathological conditions as Alzheimer's disease have directed our research towards the characterization of these receptors in various mammalian brain areas. Our studies have relied on electrophysiological, biochemical, and immunofluorescent techniques applied to cultured and acutely dissociated hippocampal neurons, and have been aimed at identifying the various subtypes of nAChRs expressed in the mammalian central nervous system (CNS), at defining the mechanisms by which CNS nAChR activity is modulated, and at determining the ion permeability of CNS nAChR channels. Our findings can be sum…

Oligomerization of Vibrio cholerae cytolysin yields a pentameric pore and has a dual specificity for cholesterol and sphingolipids in the target memb…

1999

Vibrio cholerae cytolysin permeabilizes animal cell membranes. Upon binding to the target lipid bilayer, the protein assembles into homo-oligomeric pores of an as yet unknown stoichiometry. Pore formation has been observed with model liposomes consisting of phosphatidylcholine and cholesterol, but the latter were much less susceptible to the cytolysin than were erythrocytes or intestinal epithelial cells. We here show that liposome permeabilization is strongly promoted if cholesterol is combined with sphingolipids, whereby the most pronounced effects are observed with monohexosylceramides and free ceramide. These two lipid species are prevalent in mammalian intestinal brush border membranes…

Chapter 27: Peptidergic and cholinergic receptors on cultured astrocytes of different regions of the rat CNS

1992

Publisher Summary This chapter discusses whether astrocytes possess peptidergic and cholinergic receptors. There is strong evidence that in addition to neurons, astrocytes also express receptors for neurotransmitters and neuromodulators. The investigations were carried out in explant cultures of the spinal cord, brain-stem, cerebellum, and neocortex of fetal and newborn rats. By the means of autoradiography, it was demonstrated that astrocytes possess binding sites for the vasoactive peptides 3 H-Ang II, 125 I- VIP, 125 I-ET-l, ET-3, and 125 I-AVP. These findings are consistent with electrophysiological studies demonstrating that Ang II, ET, and AVP cause a depolarization of the glial membr…

Role of hydrophobic forces in bilayer adhesion and fusion.

1992

With the aim of gaining more insight into the forces and molecular mechanisms associated with bilayer adhesion and fusion, the surface forces apparatus (SFA) was used for measuring the forces and deformations of interacting supported lipid bilayers. Concerning adhesion, we find that the adhesion between two bilayers can be progressively increased by up to two orders of magnitude if they are stressed to expose more hydrophobic groups. Concerning fusion, we find that the most important force leading to direct fusion is the hydrophobic attraction acting between the (exposed) hydrophobic interiors of bilayers; however, the occurrence of fusion is not simply related to the strength of the attrac…

Mixed monolayers of natural and polymeric phospholipids: structural characterization by physical and enzymatic methods

1990

This study has focused on physical characterization and enzymatic hydrolysis of mixed monolayers of a natural phospholipid substrate and a polymerizable phospholipid analogue. Such a mixed system presents the possibility to stabilize model biomembranes, vary the molecular environment within the layer through polymerization and simultaneously examine these influences on monolayer structure. Phospholipase A2 was used here as a sensitive probe of the molecular environment within these mixed, polymerizable monolayers to complement information obtained from isotherm and isobar data. The results clearly show a strong influence of molecular environment on phospholipase A2 activity, even if differe…

Penetration enhancer containing vesicles as carriers for dermal delivery of tretinoin.

2011

The ability of a recently developed novel class of liposomes to promote dermal delivery of tretinoin (TRA) was evaluated. New penetration enhancer-containing vesicles (PEVs) were prepared adding to conventional phosphatidylcholine vesicles (control liposomes) different hydrophilic penetration enhancers: Oramix® NS10 (OrNS10), Labrasol® (Lab), Transcutol® P (Trc), and propylene glycol (PG). Vesicles were characterized by morphology, size distribution, zeta potential, incorporation efficiency, stability, rheological behaviour, and deformability. Small, negatively charged, non-deformable, multilamellar vesicles were obtained. Rheological studies showed that PEVs had fluidity higher than conven…

Cholinergic-Adrenergic Interactions at the Presynaptic Level as Studied in the Heart

1982

Role of calcium in the adhesion and fusion of bilayers.

1993

The interaction forces and fusion mechanisms of mixed zwitterionic-anionic phospholipid bilayers were measured with the surface forces apparatus. The bilayers were 3:1 mixtures of either dimyristoylphosphatidylcholine and dimyristoylphosphatidylglycerol (DMPC/DMPG) or dilauroylphosphatidylcholine and dilauroylphosphatidylglycerol (DLPC/DLPG), and experiments were carried out in NaCl solutions with and without CaCl2. In NaCl solutions, the forces between either mixed bilayer system were consistent with the DLVO (Derjaguin-Landau-Verwey-Overbeek) theory of repulsive electrostatic and attractive van der Waals forces, and fusion did not occur. At high pH (> 6) and in high (20 mM) NaCl concentra…