0000000000040014
AUTHOR
Victor P. Whittaker
Isolation of Cholinergic Synaptic Vesicles from the Myenteric Plexus of Guinea-Pig Small Intestine
The acetylcholine-rich myenteric plexus-longitudinal muscle preparation of the guinea-pig small intestine has been subjected to subcellular fractionation using modifications of both classical methods and that originally devised for bulk isolation of cholinergic synaptic vesicles from the electromotor nerve terminals of Torpedo marmorata by means of density gradient centrifugation in a zonal rotor. The latter method gave a vesicle fraction with the highest acetylcholine content so far recorded for a mammalian particulate fraction, 30.9 +/- S.E.M. 1.8 (5) nmol of acetylcholine . mg of protein-1. Electron-microscopical examination showed that it consisted of a homogeneous preparation of vesicl…
Chapter 17: The cholinesterases: a discussion of some unanswered questions
Publisher Summary During the past three decades, a vast body of specificity and kinetic data relating to the cholinesterases has accumulated, which must now be explained by the extremely interesting new sequence and X-ray crystallographic results presented by MassouliC et al. As this chapter shows, the cholinesterases are remarkable among enzymes in having a broad specificity embracing both charged and uncharged substrates but with a clearly expressed preference, at any rate in the aliphatic series, for the acylcholine configuration: a classical example of the principle of complementariness between substrate and active site as the basis for enzyme action. It is well known that AChE exists i…
Vesicular Storage and Release of Cholinergic False Transmitters
Publisher Summary Several analogues of choline are known, which are taken up by cholinergic nerve terminals and released in the acetylated form on stimulation. Such compounds are thus precursors of cholinergic false transmitters. This chapter discusses two compounds, N-methyl-N-2-hydroxyethylpyrrolidiniu (mPCh) and homocholine (HCh), using guinea-pig cortex and the electric organ of Torpedo marmorata. In the experiments with cortex, the false transmitter precursors were injected into the tissue and released transmitters collected in Locke solution applied to the surface of the cortex in plastic sleeves. Free vesicles and those attached to external membranes were isolated from tissue subjace…
A novel cholinergic-specific antigen (Chol-2) in mammalian brain.
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…
A Trisialoganglioside Containing a Sialyl α2-6 N-Acetylgalactosamine Residue Is a Cholinergic-Specific Antigen, Chol-1α1
Cholinergic-specific antigens termed the Chol-1 family have been suggested to be of a ganglioside nature by Richardson et al. (J. Neurochem. 38, 1605-1614, 1982). Two molecular species of polysialogangliosides among bovine brain gangliosides were found to react with anti-Chol-1 alpha antiserum. One of them, Chol-1 alpha-a, was isolated and characterized as a trisialoganglioside containing the gangliotetraose backbone in which 1 mol of sialic acid was attached to each of the reducing end galactose, N-acetylgalactosamine and internal galactose residues, respectively. The chemical structure of Chol-1 alpha-a was determined for the first time, being as follows: IV3NeuAc III6NeuAc II3NeuAc-GgOse…
Vesamicol blocks the recovery, by recycling cholinergic electromotor synaptic vesicles, of the biophysical characteristics of the reserve population.
The effect of vesamicol on the ability of recycling cholinergic synaptic vesicles to recover, during a period of post-stimulation rest, the biophysical properties of the reserve pool was studied in prestimulated perfused blocks of the electric organ of the electric ray, Torpedo marmorata, a tissue rich in cholinergic synapses. The effect of the drug was analysed by high-resolution centrifugal density-gradient fractionation in a zonal rotor of the extracted vesicles. The two vesicle fractions were identified by their ATP and acetylcholine content and the recycled vesicles by their acquisition of [3H]acetylcholine derived from [3H]acetate in the perfusate. Vesamicol (10 microM) blocked the up…