scholarly journals Effect of the venom of Glycera convoluta on the spontaneous quantal release of transmitter

Toxicon ◽  
1981 ◽  
Vol 19 (3) ◽  
pp. 437-438
Keyword(s):  
Quantal Release ◽  
Glycera Convoluta

scholarly journals Effect of the venom of Glycera convoluta on the spontaneous quantal release of transmitter.

1980 ◽  
Vol 85 (2) ◽  
pp. 446-458 ◽  
Author(s):  
R Manaranche ◽  
M Thieffry ◽  
M Israel
Keyword(s):  
Electrical Activity ◽  
Morphological Changes ◽  
Electric Organ ◽  
High Rate ◽  
Ultrastructural Changes ◽  
Quantal Release ◽  
Structural Modifications ◽  
Sustained Activity ◽  
Venom Glands ◽  
Glycera Convoluta

A neurotoxin able to increase the spontaneous release of transmitter was found in the venom glands of the polychaete annelid Glycera convoluta. We studied the effect of this venom on the frog cutaneous pectoris muscle, where its application produced a prolonged (20-h), high-frequency discharge of miniature potentials. After 5 h of action, the initial store was renewed several times but no detectable ultrastructural changes were observed. After 19 h of sustained activity, nerve terminals with their normal vesicular contents were infrequent; others were fragmented and contained swollen mitochondria, abnormal inclusions, and vesicles of various sizes. In the noncholinergic crayfish neuromuscular preparation, the venom triggered an important increase in spontaneous quantal release that subsided in 1 h. An activity higher than that in resting conditions then persisted for many hours. This high electrical activity was not accompanied by any detectable structural modifications after 3 h. In the torpedo electric organ preparation, the venom elicited a burst of activity that returned to control levels in 1 h. The release of ACh (evaluated by the efflux of radioactive acetate) paralleled the high electrical activity. No morphological changes or significant depletion of tissue stores were detected. The venom of Glycera convoluta appears to enhance considerably the release of transmitter without impairing its turnover. The venom effect is Ca++ dependent and reversible by washing, at least during the first hour of action. Because the high rate of transmitter release appears dissociated from the later-occurring structural modifications, it is possible that the venom mimics one component of the double mode of action proposed for black widow spider venom.

Novel congenital myasthenic syndromes associated with defects in quantal release

Neurology ◽  
2006 ◽  
Vol 66 (8) ◽  
pp. 1223-1229 ◽  
Author(s):  
M. Milone ◽  
T. Fukuda ◽  
X. M. Shen ◽  
A. Tsujino ◽  
J. Brengman ◽  
...  
Keyword(s):  
Quantal Release ◽  
Congenital Myasthenic Syndromes ◽  
Myasthenic Syndromes

scholarly journals Large-scale purification of presynaptic plasma membranes from Torpedo marmorata electric organ.

1985 ◽  
Vol 101 (5) ◽  
pp. 1757-1762 ◽  
Author(s):  
N Morel ◽  
J Marsal ◽  
R Manaranche ◽  
S Lazereg ◽  
J C Mazie ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Large Scale ◽  
Plasma Membranes ◽  
Electric Organ ◽  
Acetylcholinesterase Activity ◽  
Cholinergic Nerve Terminals ◽  
Membrane Bound ◽  
Torpedo Electric Organ ◽  
Presynaptic Plasma Membrane ◽  
Glycera Convoluta

The presynaptic plasma membrane (PSPM) of cholinergic nerve terminals was purified from Torpedo electric organ using a large-scale procedure. Up to 500 g of frozen electric organ were fractioned in a single run, leading to the isolation of greater than 100 mg of PSPM proteins. The purity of the fraction is similar to that of the synaptosomal plasma membrane obtained after subfractionation of Torpedo synaptosomes as judged by its membrane-bound acetylcholinesterase activity, the number of Glycera convoluta neurotoxin binding sites, and the binding of two monoclonal antibodies directed against PSPM. The specificity of these antibodies for the PSPM is demonstrated by immunofluorescence microscopy.

scholarly journals Timing of Quantal Release from the Retinal Bipolar Terminal Is Regulated by a Feedback Circuit

Neuron ◽  
2003 ◽  
Vol 38 (1) ◽  
pp. 89-101 ◽  
Author(s):  
Michael A Freed ◽  
Robert G Smith ◽  
Peter Sterling
Keyword(s):  
Feedback Circuit ◽  
Quantal Release

Development of neuromuscular synapses

1983 ◽  
Vol 63 (3) ◽  
pp. 915-1048 ◽  
Author(s):  
M. R. Bennett
Keyword(s):  
Motor Unit ◽  
Muscle Cells ◽  
Terminal Branch ◽  
Quantal Release ◽  
Synaptic Site ◽  
Neuromuscular Synapses ◽  
A Site ◽  
Threshold Amount ◽  
Neuron Soma ◽  
Secretory Capacity

Quantal secretion at nerve terminals in mature muscles depends on the number of terminal branches and the size of release sites (sect. VB4). The physical length of SBL determines the length of terminal branch that can be laid down in a reinnervation experiment (sect. IVA4). A limit is set on the total length of terminal branches formed by a motoneuron; this limit is determined by the amount of TF (sect. IVB) made available from the neuron soma to the peripheral branches of the neuron (sect. VC). As a result of this limit, not all SBL needs to be occupied at a site by terminal branches. The SBL eventually disappears if it is not occupied by terminal branches (sect. IVA2). If a muscle is relatively inactive, it synthesizes and releases at synaptic sites additional amounts of NGF, which stimulates the growth of additional terminal branches. These may secrete sufficient amounts of AF to induce the formation of new SRs with associated SBL. In these circumstances a new synaptic site is formed or an extension of an existing site is created. If the size of a motor unit is decreased, the enhanced release of TF at the remaining terminals ensures that each occupies all the SBL at the synaptic site. Furthermore the enhanced release of AF per terminal induces more SBL, allowing additional terminal branches on the muscle cells to be established. Neither of these changes occurs unless the threshold amount of NGF is available from the muscle to stabilize the terminals. If this condition is met, an increase in quantal release per terminal occurs after reducing the size of a motor unit (sect. VC). An increase in quantal release per terminal also occurs after inactivation of a muscle. Such inactivation leads to an enhanced release of NGF per synaptic site (sect. VA4). Extra terminals may then form if sufficient TF is available; these may innervate existing but empty synaptic sites. In rare circumstances the extra terminal may induce SBL and innervate these new sites if sufficient AF is available. In both cases the quantal release per terminal increases. During development the secretory capacity of the axon terminal depends on the muscle cells with which it synapses. This secretory capacity can be enhanced either by increasing the number of terminal branch pairs or by increasing the secretory capacity of individual release sites. If two terminals innervate a synaptic site, their individual secretory capacity is reduced--in these circumstances the terminal's secretory capacity depends on the amount of NGF available to the terminal; two terminals must share their NGF.

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