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At least 19 recordsLinked to original sources
PubMed1979

Stimulation of Ca2+-dependent neurotransmitter release and presynaptic nerve terminal protein phosphorylation by calmodulin and a calmodulin-like protein isolated from synaptic vesicles.

Synaptic vesicles have a Ca(2+)-dependent protein kinase system that may play a role in mediating Ca(2+)-stimulated neurotransmitter release and vesicle function. Calcium's ability to initiate norepinephrine release and protein phosphorylation in synaptic vesicle preparations was shown to be stimulated by the presence of an endogenous heat-stable vesicle protein fraction. The heat stability and characteristics of this endogenous vesicle fraction were similar to those of calmodulin (Ca(2+)-dependent regular protein) isolated from rat and bovine brain. Calmodulin, like endogenous heat-stable vesicle factor, restored calcium's ability to stimulate vesicle neurotransmitter release and protein kinase activity. Calmodulin-like vesicle protein and purified calmodulin were also equally effective in stimulating cyclic nucleotide-dependent phosphodiesterase, further indicating that these two proteins are functionally equivalent. Depolarization-dependent Ca(2+) uptake in intact synaptosomes simultaneously stimulated release of neurotransmitter and phosphorylation of particular synaptic vesicle proteins that were shown in the isolated vesicle preparation to be dependent on Ca(2+) and calmodulin. The results suggest that calcium's effects on neurotransmitter release and presynaptic nerve terminal protein phosphorylation may be mediated by endogenous calmodulin-like proteins.

Animals↗
PubMed1978

[Separation of enriched synaptosomes, synaptic vesicles and synaptic plasma membranes].

A rapid and simple method is described for separation of intact synaptosomes, synaptic plasma membranes and vesicles. Two synaptosome fractions were obtained by modified differential centrifugation. The rate zonal zentrifugation in a linear sucrose gradient (very low density) is suitable to obtain fractions highly enriched in synaptic plasma membranes and vesicles. Examination of the prepared fractions was done by enzyme marker activities and electron microscopy

Adenosine Triphosphatases↗
PubMed1979

Studies on synaptic vesicles in mammalian brain characterization of highly purified synaptic vesicles from bovine cerebral cortex.

Synaptic vesicles have been isolated from bovine cerebral cortex by sequential differential and density gradient centrifugations followed by chromatography on a Sepharose 6B column. We have studied the morphology, enzymatic markers, neurotransmitter and ATP contents and protein composition of the vesicles. The specific contents of acetylcholine, gamma-aminobutyric acid, aspartate, glutamate and catecholamines were 4--8-fold higher in the vesicle fraction compared to the crude synaptosomal pellet. Electron micrographs of the vesicle preparation showed enrichment of vesicular material with an average diameter of 50 nm. The purity of the preparation was assessed by the very low activities of enzymatic markers of cellular membranes and cytosol components. Some Ca--Mg-activated ATPase activity was detected in the vesicle preparations, but its content relative to the neurotransmitters fell on chromatography, suggesting that this activity may be partially contributed by non-synaptic vesicle components, such as small microsomes. The isolated synaptic vesicles were solubilized with 1% sodium dodecyl sulfate and subjected to polyacrylamide gel electrophoresis. The major Coomassie blue stained bands observed with apparent molecular weights of 160,000 and 55,000 were enriched in parallel to the increase in purity of the preparation.

Acetylcholinesterase↗
PubMed1979

Topological organization of proteins in an intracellular secretory organelle: the synaptic vesicle.

Intact synaptic vesicles prepared from the electric organ of the marine elasmobranch Narcine brasiliensis have eight major polypeptides demonstrable on sodium dodecyl sulfate gels. Six of these copurify with the synaptic vesicles during isolation of vesicles by chromatography on CPG-3000 and, by this criterion, are specific to vesicles. The other two are either shared by many membrane or are contaminants. One of these proteins comigrates with actin. Three different approaches were used to determine which proteins were exposed on the external, cytoplasmic surface of the vesicle and which were internal. The first was susceptibility to the proteases trypsin, Streptomyces griseus protease, and Pronase; the second was labeling by the membrane-impermeable reagent diazotized [125I]iodosulfanilic acid; and the third was iodination catalyzed by lactoperoxidase. In general, the three approaches give the same result: six of the eight proteins are on the external, cytoplasmic surface and two are accessible only after the vesicles are lysed by freezing and thawing or by detergents. Five of the vesicle-specific proteins are external and one is internal. The actin-like protein is internal. Proteins involved in the interaction of vesicles with the presynaptic membrane during exocytosis might be expected to be vesicle specific and external.

Acetylcholine↗
PubMed1979

Substance P: characteristics of binding to synaptic vesicles of rat brain.

1. The binding of substance P (SP) to synaptic vesicles from rat brain was studied by use of the 125I-Tyr8-analogue of SP. 2. The pH dependence of the binding of both peptides to the lipid extractable fraction of synaptic vesicles was shown to be comparable. 3. The binding of 125I-Tyr8-SP shows a rate constant of association (k1 = 6.6 x 10(6) M-1 S-1), a rate constant of dissociation (k-1 = 6.4 x 10(-4) S-1) and gives a KD of 1 x 10(-10) M. Kd derived from equilibrium studies was 3.2 x 10(-10) M. 4. The binding of 125I-Tyr8-SP to lipids of synaptic vesicles was shown to be reversible, saturable and highly specific. 5. The kinetic data suggest one population of binding sites with a maximal number of 0.8 pmol per mg protein of the synaptic vesicle preparation. 6. Unlabeled SP and the (2--11)-, (3--11)- and (4--11)-analogues of SP inhibit the binding of 125I-Tyr8-SP in a decreasing order in a competitive way when added in excess. Tyr8-SP and eledoisin did not interfere with the binding of 125I-Tyr8-SP whereas uperolein and neurotensin caused a partial inhibition. Physalaemin and D-Ala2-D-Met5-enkephalin enhance the binding of 125I-Tyr8-SP in a cooperative way.

Animals↗
PubMed1976

The preparation and characterization of synaptic vesicles of high purity.

Very pure preparations of synaptic vesicles have been obtained from guinea pig cerebral cortex and from the electromotor synapses of Torpedo marmorata by density gradient centrifugation in a zonal rotor followed by chromatography on columns of glass beads of controlled pore size. Markers for soluble cytoplasm (lactate dehydrogenase), plasma and endoplasmic membranes membranes (Na-K-ATPase; acetylcholinesterase, NADPH-cytochrome c reductase], mitochondrial membranes [cytochrome oxidase] and lysosomes [acid phosphatase] were used to assess contamination and were undetectable. The only enzymes detected in the highly purified preparations from guinea pig cerebral cortex were Mg- and Ca-activated ATPases, but their content relative to acetylcholine fell on chromatography suggesting that they may be constituents of non-cholinergic vesicles. Lipids analyses of the highly purified vesicles confirmed earlier results and showed that glycolipids and lysolecithin are present in negligible amounts; this suggests that lysolecithin is not required for exocytosis of synaptic vesicles. A discussion of the probable limiting concentration of acetycholine in cerebral cortical vesicles derived solely from cholinergic terminals suggests that from 13 to 56% of the vesicles isolated are cholinergic, depending on the assumptions made.

Acetylcholine↗
PubMed1977

Synaptic vesicle fraction devoid of adenosine triphosphatase activity from bovine caudatolenticular nuclei and thalamus.

1. As a part of studies on the mechanism by which catecholamines are released from the nerve terminals, the synaptic vesicle fraction was isolated from bovine caudatolenticular nuclei and thalamus by differential centrifugation essentially according to the method of Kadota and Kadota (17). 2. Further centrifugation on a sucrose density gradient of the synaptic vesicle fraction by the method of Whittaker et al. (1) yielded white materials on the upper portion of 0.4 M sucrose, which consisted of vesicles averaging 600-800 A in diameter, and did not show Mg2+-dependent ATpase activity. On the other hand, the denser materials centering on 0.6 M sucrose, consisting of a mixture of microsomes and synaptic vesicles of 400-500 A diameter, showed an ATpase activity activated by either Mg2+ or Ca2+ but not inhibited by ouabain. 3. The white materials on 0.4 M sucrose were almost free of mitochondria, but they contained a large amount of non-heme iron, as reported elsewhere (2). Furthermore, the protein components analyzed on SDS-polyacrylamide gels were similar to those already reported for purified synaptic vesicles (3). 4. Based on these results, the white materials were assumed to be synaptic vesicles devoid of Mg2+-dependent ATPase activity.

Adenosine Triphosphatases↗
PubMed1978

Electrogenic behavior of synaptic vesicles from Torpedo californica.

Electrical potential changes in pure synaptic vesicles from Torpedo californica were monitored with the fluorescent dye 3,3'-dipropylthiadicarbocyanine iodide. Vesicles resuspended in variable external sodium ion in the presence of gramicidin established sodium ion membrane diffusion potentials. Vesicles resuspended in choline or acetylcholine chloride became hyperpolarized upon addition of gramicidin. Hyperpolarization was subsequently partially reversed spontaneously by choline or acetylcholine influx, which was confirmed by gel filtration, to yield a new, less negative, stable membrane potential. Thus, acetylcholine and choline are taken up electrogenically by synaptic vesicles.

Acetylcholine↗
PubMed1975

The involvement of lysophosphoglycerides in neurotransmitter release; the composition and turnover of phospholipids of synaptic vesicles of guinea-pig cerebral cortex and Torpedo electric organ and the effect of stimulation.

(1) Crude synaptosomal fractions (P2) derived from guinea-pig cerebral cortex were incubated in the presence of 50 mM KCl in a Krebs-glucose medium. Torpedo marmorata electric organs were stimulated electrically in vivo at 5 pulses/sec for 30 min by electrodes placed on the electric lobe. Synaptic vesicles were isolated from each source and the phospholipid compositions analysed and compared with vesicles from unstimulated controls. (2) Lysophosphatidylcholine was the only lysophosphoglyceride demonstrable in the synaptic vesicles from either source and its low levels did not increase as a result of chemical or electircal stimulation. In each case there was a close similarity of the phospholipid distributions in the vesicles taken from control and stimulated samples. (3) Control experiments indicated extensive decreases in the acetylcholine content of the vesicles from the stimulated electric organ and smaller decreases in the acetylcholine content of the synaptic vesicles from stimulated crude synaptosomal fractions. These fractions were found to respire linearly in the presence of 10 mM glucose and the vesicle fractions were shown to have low levels of contaiminating membranes as judged by marker enzyme analyses. (4) Crude synaptosomal fractions from guinea-pig cerebral cortex were incubated in a Krebs-glucose medium with labelled fatty acids and [3H]glucose in the presence or absence of 50 mM KCl. Subsynaptosomal fractionation was carried out and specific radioactivities of phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine and phosphatidylinositol were determined in fractions D (synaptic vesicles), E (microsomes) and H (disrupted synaptosomes). The release of neurotransmitter did not significantly enhance the labelling of phospholipids in any of the fractions studied as compared with phospholipids from unstimulated fractions. This was found after two incubation times and using [14C]oleate, [14C]arachidonate, [3H]palmitate and [3H]glucose.

Acetylcholine↗
PubMed1976

A critical evaluation of the relationship between the presynaptic network, synaptic vesicles and dense projections in central synapses.

Synapses of the oculomotor nucleus of Echidna have been examined ultrastructurally with the aim of integrating data obtained from osmicated and nonosmicated PTA stained material. Particular emphasis has been laid on the relationship between the synaptic vesicles of the osmicated material and the presynaptic network and vesicular grid of the PTA material. This relationship has been explored qualitatively by examining osmicated material of varying qualities of fixation. Such material contains dense projections in addition to synaptic vesicles, and various vesicular network appearances. A variety of measurement techniques have shown that the PTA network is characterised by reticular strands, spaces, and regular hexagonal units smaller than vesicles, these observations prompting the formulation of a "vesicle-network coincidence" model of the presynaptic terminal. This model has been tested by tracing the profiles of vesicles within the PTA network and comparing their size and shape frequency distributions with those of osmicated synaptic vesicles. The distributions have been found to be essentially similar, suggesting that vesicles can be located within the network, and that the hexagonal network units are formed only in the presence of an underlying vesicular matrix. Additionally, the following points have emerged: 1) the dense projections in the two types of material appear to be quivalent; 2) a loose correlation exists between dense projections and vesicles in osmicated terminals, increase in the area of the dense projections being associated with a decrease in the area of the vesicles; 3) network and dense projection units are similar. In view of the similarity between network and dense projection units, the demonstrated vesicular basis of the network raises the question of whether dense projections are entirely independent structures, or whether they depend in part for their existence on the nearby presence of synaptic vesicles.

Animals↗
PubMed1976

Interrelationships between Golgi, GERL and synaptic vesicles in the nerve cells of insect and gastropod ganglia.

In addition to demonstrating synaptic vesicles, staining with the zinc-iodide-osmium tetroxide (ZIO) method reveals the presence of positively reacting GERL membranes in association with the Golgi complex and lysosomes in the nerve cell bodies within ganglia from the locust Schistocerca gregaria and the gastropod molluscs, Limnaea stagnalis and Helix aspersa. A positive response to ZIO occurs in certain Golgi vesicles and saccules, in GERL (Golgi-endoplasmic-reticulum-lysosomes), in multivesicular bodies as well as residual bodies and in small vesicles and cisternae of axonal smooth endoplasmic reticllum (ER). The interrelationships between these organelles are considered in view of the similarity of the ZIO localization to phosphatase-rich sites in the neuronal perikarya and with respect to the possibility that components of the synaptic vesicles are formed in the Golgi region of the cell and migrate via the axonal smooth ER to the synaptic regions.

Animals↗
PubMed1975

[Effect of carbidine on the content and storage of adrenergic neurotransmitter in the synaptic vesicles].

The influence of carbidine, an original psychotropic drug, on the adrenergic neurotransmitter content and storage in the sympathetic nerves was studied with the use of cytochemical electron microscopy. The influence of carbidine on the uptake of the exogenous noradrenaline (NA) in the synaptic vesicles was also studied. Carbidine was found to be capable to decreasing the NA storage in the synaptic vesicles and failed to block the accumulation of the exogenous NA in the synaptic vesicles.

Amines↗
PubMed1976

Characterization of ATPases of plain synaptic vesicle and coated vesicle fractions isolated from rat brains.

The plain synaptic vesicle and the ocated vesicle fractions were isolated from rat brains, and the ATPase [EC 3.6.1.3] activities were characterized in terms of ionic effects, drug effects, and protein components. Coated vesicle fraction contained three times as much actomysin-like proteins as plain vesicle fraction, although both fractions had an identical ratio of actin-like protein to myosin-like protein. The ATPases of these two fractions were activated by both Mg2+ and Ca2+, and, in the presence of either of the cations, were inhibited by KCl. Reserpine activated plain vesicle ATPase only in the presence of Cl-. Colchicine and vinblastine inhibited coated vesicle ATPase only. The results are consistent with the view that actomyosin-like proteins are involved in the synaptic retrieval process.

Actins↗
PubMed1979

5'-triphosphate recycles independently of acetylcholine in cholinergic synaptic vesicles.

The effect of hemicholinium-3 (HC-3) on vesicular contents in acetylcholine (ACh) and 5-triphosphate (ATP) and the vesicular incorporation of 14C-label derived from [14C]choline ,nd 3H-label derived from [3H]adenosine was investigated after low frequency stimulation (with a subsequent rest period) of the Torpedo electric organ. HC-3 (100 microM) caused an increased depletion of vesicular ACh and blocked the incorporation of 14C-label whereas contents in vesicular ATP and 3H-incorporation were identical with and without HC-3. HC-3 also blocked the recovery of electrical response of the tissue after stimulation but did not cause a change in vesicle numbers. The result suggest that synaptic vesicles continue to recycle ATP in the absence of recycling of ACh and that vesicular uptake and storage of the two components are not coupled to each other.

Acetylcholine↗
PubMed1979

ZIO staining in synaptic vesicles of the rat pineal nerves after inhibition of serotonin and noradrenaline synthesizing enzymes.

Two compartments have been defined in monoaminergic synaptic vesicles: the core or central compartment, storage site for monoamines, and the matrix or outer compartment, of unknown function. The outer compartment reacts with the mixture of zinc iodide-osmium tetroxide (ZIO). This reaction is temperature and time dependent and may be abolished by -SH reagents. The effect of drugs inhibiting the synthesis of serotonin and noradrenaline (stored in the core) on the ZIO reaction in the matrix was studied in synaptic vesicles of rat pineal nerves. The inhibitors of monoamine synthesis abolish or decrease the ZIO reaction directly or in combination with the administration of tyramine. This effect is temperature dependent suggesting that the drugs act on different components of the matrix that react with ZIO at different temperatures. A comparison of the present results with those obtained with -SH reagents seems to indicate that the drugs assayed act, at least in part, by changing the accessibility of -SH groups in vesicle proteins. (An abstract of this paper was presented at the 7th International Congress of Pharmacology, Paris, 1978.)

Animals↗
PubMedDate not supplied

[Neuromediator content in the synaptic vesicles of rat adrenergic nerves in some pharmacological actions].

Cytochemical electron microscopy was employed to study the content of neurotransmitters in the synaptic vesicles of adrenergic nerve fibers of Vas deferens of the rat following depletion of the meadiator's reserves by tyramine and subsequent accumulation of exogenous norepinephrine. Subject to investigation was also the effect of antidepressants (phthoracizine and imipramine) on the accumulation of exogenous norepinephrine in the synaptic vesicles. Phthoracizine and imipramine (1 and 10 gamma/ml) are shown to block the acculation of norepinephrine in the vesicles, when the mediator is introduced in a concentration of 0,5 gamma/ml, and not to impede this process, if the mediator's concentration is increased to 30 gamma/ml.

Animals↗