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  • 1
    Electronic Resource
    Electronic Resource
    Increased Ca-uptake of presynaptic terminals during long-term potentiation in hippocampal slices (1986)
    Springer
    Experimental brain research 62 (1986), S. 663-668 
    Details
    ISSN: 1432-1106
    Keywords: CA1 ; Hippocampus ; Long-term potentiation ; Ca-uptake ; Subcellular fractionation ; Presynaptic terminals
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary A combined electrophysiological and neurochemical study was performed on the CA1 area of hippocampal slices in an attempt to identify changes in presynaptic nerve terminal function in long-term potentiation (LTP). After controlled induction of LTP in CA1, the activated region was subjected to subcellular fractionation followed by 45Ca2+ uptake determinations. Synaptosomes prepared from slices in which LTP has been induced showed a faster risetime and a higher level of saturation for K+-induced Ca-uptake than those derived from unstimulated and stimulated control slices. These findings point to a participation of presynaptic terminals in long-term potentiation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00236048
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  • 2
    Electronic Resource
    Electronic Resource
    4-Ammopyridine-induced ultrastructural alterations of pinched-off nerve terminals from rat cerebral cortex (1984)
    Springer
    Experimental brain research 54 (1984), S. 385-389 
    Details
    ISSN: 1432-1106
    Keywords: Synaptosome ; 4-Aminopyridine ; Ultrastructure ; Exocytosis ; Recycling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Pinched-off nerve terminals (synaptosomes) from rat cerebral cortex were depolarized with 60 mM KCl and treated with 20 mM 4-aminopyridine in order to evaluate ultrastructural alterations. The empty presynaptic terminals were counted and their number was given as a percentage of the normal terminals. The proportion of empty terminals increased from 10.47±1.56% to 32.45±1.88% (P 〈 0.001) following treatment with 20 mM 4-aminopyridine. This effect of 4-aminopyridine depended on the presence of Ca++ in the incubation medium. The results are discussed in terms of facilitation by 4-aminopyridine of exocytotic transmitter release. We think that the increase of the empty synaptosomes was due to the exhaustion or inhibition of the synaptic vesicle recycling mechanism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00236242
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  • 3
    Electronic Resource
    Electronic Resource
    Presence of Vasoactive Intestinal Polypeptide-Like Immunoreactivity in the Cholinergic Electromotor System of Torpedo marmorata (1986)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 47 (1986), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Vasoactive intestinal polypeptide (VIP)-like immunoreactivity was detected in the cholinergic electromotor system of Torpedo marmorata using a combination of immunohistochemical assays, radioimmunoassay, and HPLC. The immunohistochemical assays revealed that the distribution of VIP-like immunoreactivity in the electric lobes, electromotor nerves, and electric organ is comparable to that of the stable cholinergic synaptic vesicle marker vesicle-specific proteoglycan. Ligation of the electromotor nerves caused a marked accumulation of VIP-like immunoreactivity in the lobes (180%) and the proximal portions of the electromotor nerves (130%) and a decrease in the electric organ (-50%), when measured by radioimmunoassay using synthetic VIP (porcine sequence) as the standard. VIP-like immunoreactivity in extracts of electric lobes electromotor nerves, and electric organ was eluted from a semipreparative reverse-phase HPLC column as a single peak with a retention time similar to that of porcine VIP. Rechromatography at higher resolution on an analytical column indicated diversity between the molecular forms of VIP-like immunoreactivity extracted from electric lobe and electric organ, suggesting the possibility of posttranslational processing.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1986.tb04521.x
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  • 4
    Electronic Resource
    Electronic Resource
    Characterization, by Size, Density, Osmotic Fragility, and Immunoaffinity, of Acetylcholine- and Vasoactive Intestinal Polypeptide-Containing Storage Particles from Myenteric Neurones of the Guinea-Pig (1989)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 52 (1989), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: When cytoplasmic extracts of guinea-pig myenteric neurones are submitted to centrifugal density gradient fractionation in a zonal rotor acetylcholine is bimodally distributed in the gradient, in a peak (I) rich in synaptic vesicles of the classic type and in a denser peak (II/VI) rich in densecored vesicles and vasoactive intestinal polypeptide (VIP). The putative stable synaptic vesicle markers synaptophysin (p38), vesicular proteoglycan, and Mg2+-activated ATPase were also bimodally distributed, with a peak coincident with peak I and another, broader peak embracing peak II/VI, and neighbouring peaks of other neuropeptides resolved from peak II/VI by the density gradient separation procedure used. To establish whether the stable markers, acetylcholine and VIP in peak II/VI were present in one particle or several, attempts were made to separate them by particle-exclusion chromatography and differential osmotic fragility. These were unsuccessful, leading us to conclude that the storage particles in peak II/VI contain both neurotransmitters and all three putative stable synaptic vesicle markers. It is suggested that such particles are the counterparts, in cholinergic neurones of the myenteric plexus, of the dense-cored, enkephalin- and noradrenaline-containing vesicles of certain adrenergic neurones and, like the latter, may exist in a precursor–product relationship with the classic synaptic vesicles containing the small-molecular-mass transmitters and found in the same nerve terminals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1989.tb09196.x
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  • 5
    Electronic Resource
    Electronic Resource
    Proteolytic Inactivation of Substance P and Neurokinin A in the Longitudinal Muscle Layer of Guinea Pig Small Intestine (1986)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 47 (1986), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Membrane vesicles, showing a 21 ± 2-fold enrichment in the activity of 5′-nucleotidase and a 11 ± 4-fold enrichment in the activity of angiotensin-converting enzyme relative to homogenate, were prepared from the myenteric plexus-containing longitudinal muscle layer of guinea pig ileum. Incubation of the vesicles with substance P and neurokinin A led to degradation of the peptides, and metabolites were isolated by reverse-phase HPLC and identified by amino acid composition. Cleavages of substance P between Glu6-Phe7, Phe7-Phe8, and Gly9-Leu10 and of neurokinin A between Gly8-Leu9 were observed and could be inhibited in a dose-dependent manner by phosphoramidon, an inhibitor of neutral endopeptidase 24.11. Formation of these metabolites was not completely inhibited by this agent, indicating that a phosphoramidon-insensitive form of endopeptidase 24.11 was present in the gut. Substance P was resistant to degradation by aminopeptidases, but neurokinin A was a substrate for bestatin-sensitive aminopeptidase(s), so that the neurokinin A (3–10) fragment represented the predominant metabolite in the chromatograms. The rate of formation of all the metabolites was not inhibited by ena-lapril and not enhanced by an increased Cl− concentration, indicating that angiotensin-converting enzyme was unimportant in the degradation process. Degradation of neurokinin A by the vesicles (Km 30 μM; Vmax 7.2 ±0.8 nmol min−1 mg of protein−1) was more rapid than degradation of substance P (Km 25 μM; Vmax 4.4 ± 0.4 nmol min−1 mg of protein−1).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1986.tb00690.x
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  • 6
    Electronic Resource
    Electronic Resource
    Conversion of Neuropeptide K to Neurokinin A and Vesicular Colocalization of Neurokinin A and Substance P in Neurons of the Guinea Pig Small Intestine (1987)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 48 (1987), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: The highest concentration of neurokinin A-like immunoreactivity and substance P-like immunoreactivity in the guinea pig small intestine was associated with the myenteric plexus-containing longitudinal muscle layer. Chromatographic analysis of extracts of this tissue demonstrated the presence of neurokinin A and neuropeptide K but the probable absence of neurokinin B. A fraction of synaptic vesicles of density 1.133 ± 0.003 g/ml was prepared from the myenteric plexus-containing tissue by density gradient centrifugation in a zonal rotor and was enriched 29 ± 12-fold in the concentration of neurokinin A-like immunoreactivity and 43 ± 13-fold in the concentration of substance P-like immunoreactivity. This fraction was separated from the fraction of vasoactive intestinal peptide-containing vesicles (density, 1.154 ± 0.009 g/ml). Chromatographic analysis of lysates of the vesicles indicated the presence of neurokinin A but not neuropeptide K. It is postulated that β-pre-protachykinin is processed to substance P, neurokinin A, and neuropeptide K in the cell bodies of myenteric plexus neurons but that conversion of neuropeptide K to neurokinin A takes place during packaging into storage vesicles for axonal transport. The data are consistent with the proposal that neurokinin A and substance P are stored in the same synaptic vesicle, but the possibility of cosedimentation of different vesicles of very similar density cannot be excluded.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1987.tb13138.x
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  • 7
    Electronic Resource
    Electronic Resource
    A Kinetic Study of Stimulus-Induced Vesicle Recycling in Electromotor Nerve Terminals Using Labile and Stable Vesicle Markers (1986)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 47 (1986), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract The kinetics of recovery, by recycling electromotor synaptic vesicles, of the biophysical parameters of the reserve population has been studied in perfused blocks of electric organ of Torpedo marmorata prestimulated in vivo, followed by density gradient separation of the extracted vesicles in a zonal rotor using labile (acetylcholine and ATP) and stable (proteoglycan) vesicle markers. Stimulation in vivo at 0.15 Hz for 3.3 h depleted tissue acetylcholine much less than stimulation at 1 Hz for 1 h but nevertheless generated a much larger pool of recycled vesicles that recovered more slowly. At the lower rate of stimulation, recovery of the biophysical characteristics of the reserve population by the recycled vesicles, identified by their content of newly synthesized transmitter, was essentially complete by 8 h. The stable proteoglycan marker was immunochemically assayed and was bimodally distributed in the vesicle-containing portion of the density gradient even in experiments with unstimulated or recovered tissue. The second peak corresponded with that of newly synthesized transmitter and was thus identified as containing the recycled vesicles. Its normalized acetylcholine/proteoglycan ratio was lower than that of the first peak, which is consistent with earlier findings that recycled vesicles, before recovery, are only partially loaded with transmitter. However, as expected, the proportion of total vesicular proteoglycan and acetylcholine associated with the recycled vesicle fraction was very much lower in preparations derived from unstimulated or recovered tissue than in those from recently stimulated tissue.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1986.tb00798.x
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  • 8
    Electronic Resource
    Electronic Resource
    Effects of a 4-Aminopyridine in Calcium Movements and Changes of Membrane Potential in Pinched-Off Nerve Terminals from Rat Cerebral Cortex (1983)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 41 (1983), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: A study was conducted on the influence of 4-aminopyridine (4-AP) on the radiocalcium uptake and membrane potential of rat cortical synaptosomes previously depolarized by biochemical procedures. The initial calcium entry into isolated nerve terminals was substantally enhanced in the presence of 10-−4M 4-AP in potassium-rich media (60 mM). The fast initial phase of potassium-stimulated calcium entry involves different kinetic characteristics in the presence and the absence of 4-AP. In the presence of 4-AP, the fast component of calcium entry reached a peak during the first 15 s immediately following depolarization. The potassium-stimulated synaptosomal calcium influx at 15 s was 3.5 ± 0.17 times higher in the presence of 4-AP (10-−4M) and 2.6 ± 0.11 times higher in the absence of 4-AP as compared with the respective unstimulated uptake values. In the absence of 4-AP, however, the calcium entry did not show a peak until 45 s after depolarization. The total amount of calcium accumulated in the synaptosome treated and untreated by 4-AP is equal at the end of this initial uptake period. The effect of 4-AP on membrane potential during depolarization of synaptosomes evoked by potassium-rich medium was also determined by means of a potential sensitive fluorescent dye. It was found that 4-AP had no effect on the final level of membrane potential, induced by high [K+]o; however, the kinetics showed significant differences. The initial phase of synaptosomal membrane depolarization was slower in the presence of 4-AP: τ-4-AP: 42 ± 4.0 s, τ-control: 18 ± 2.5 s. The initial calcium entry into the nerve terminals was increased during the 4-AP treatment in potassium-rich media—as resulted from our calcium uptake studies—and thus, during this higher calcium influx, the degree of membrane depolarization was decreased. This faster initial calcium influx constitutes a feasible explanation for the unique effect of 4-AP termed “chemical potentiation” on transmitter release at chemical synapses.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1983.tb04803.x
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  • 9
    Electronic Resource
    Electronic Resource
    Potential autocrine and autoregulatory action of VIP in human neuroblastoma cells
    Amsterdam : Elsevier
    Regulatory Peptides 26 (1989), S. 171 
    Details
    ISSN: 0167-0115
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Medicine
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0167-0115(89)90065-7
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  • 10
    Electronic Resource
    Electronic Resource
    Comparative biochemical and biophysical studies on rat brain synaptosomes
    Amsterdam : Elsevier
    FEBS Letters 137 (1982), S. 67-70 
    Details
    ISSN: 0014-5793
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0014-5793(82)80316-5
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