scholarly journals Localization of acetylcholine receptors by means of horseradish peroxidase-alpha-bungarotoxin during formation and development of the neuromuscular junction in the chick embryo

1979 ◽  
Vol 82 (1) ◽  
pp. 195-211 ◽  
Author(s):  
M. Jacob
Keyword(s):  
Chick Embryo ◽  
Horseradish Peroxidase ◽  
Neuromuscular Junction ◽  
Acetylcholine Receptors ◽  
Alpha Bungarotoxin

scholarly journals In vivo recovery of muscle contraction after alpha-bungarotoxin binding.

1975 ◽  
Vol 66 (1) ◽  
pp. 209-213 ◽  
Author(s):  
H C Fertuck ◽  
W Woodward ◽  
M M Salpeter
Keyword(s):  
Fine Structure ◽  
Neuromuscular Junction ◽  
Muscle Contraction ◽  
Acetylcholine Receptors ◽  
Actinomycin D ◽  
Recovery Period ◽  
Em Autoradiography ◽  
Alpha Bungarotoxin ◽  
In Vivo Recovery

Acetylcholine receptors were inactivated in vivo at the mouse neuromuscular junction using alpha-bungarotoxin (alpha-BTX). It was found that neurally produced muscle contraction recovered within 4-8 days (halftime similar to 3 days). Actinomycin D interfered with this recovery, but did not affect normal nerve-stimulated muscle contraction. If the response was initially eliminated by [125-I]alpha-BTX and the end plates examined by EM autoradiography, no evidence of mass internalization of bound radioactivity during recovery was seen. The fine structure of the end plates and muscle was unaltered during the post-alpha-BTX recovery period.

scholarly journals Alpha-bungarotoxin-horseradish peroxidase conjugate: preparation, properties and utilization for the histochemical detection of acetylcholine receptors.

1979 ◽  
Vol 27 (4) ◽  
pp. 846-851 ◽  
Author(s):  
Z Vogel ◽  
M Towbin ◽  
M P Daniels
Keyword(s):  
Horseradish Peroxidase ◽  
Acetylcholine Receptors ◽  
Light And Electron Microscopy ◽  
Gel Filtration ◽  
Histochemical Staining ◽  
Ion Exchange Chromatography ◽  
Exchange Chromatography ◽  
Nicotinic Acetylcholine ◽  
Alpha Bungarotoxin ◽  
Peroxidase Conjugate

A method is presented for the efficient conjugation of horseradish peroxidase to alpha-bungarotoxin. The 1:1 molar conjugate obtained is purified to completion by gel filtration on Sephadex G-100, followed by ion exchange chromatography on CM-Sephadex. The conjugate retains half of the activity of unmodified horseradish peroxidase and binds effectively to the nicotinic acetylcholine receptor of muscle. The conjugate is proven to be useful reagent for the histochemical staining of the receptor on muscle fibers for light and electron microscopy.

scholarly journals Metabolic stabilization of acetylcholine receptors in vertebrate neuromuscular junction by muscle activity.

1990 ◽  
Vol 111 (2) ◽  
pp. 655-661 ◽  
Author(s):  
S Rotzler ◽  
H R Brenner
Keyword(s):  
Skeletal Muscle ◽  
Neuromuscular Junction ◽  
Muscle Activity ◽  
Acetylcholine Receptors ◽  
Muscle Stimulation ◽  
Cluster Growth ◽  
Rat Skeletal Muscle ◽  
Achr Cluster ◽  
End Plate ◽  
Alpha Bungarotoxin

The effects of muscle activity on the growth of synaptic acetylcholine receptor (AChR) accumulations and on the metabolic AChR stability were investigated in rat skeletal muscle. Ectopic end plates induced surgically in adult soleus muscle were denervated early during development when junctional AChR number and stability were still low and, subsequently, muscles were either left inactive or they were kept active by chronic exogenous stimulation. AChR numbers per ectopic AChR cluster and AChR stabilities were estimated from the radioactivity and its decay with time, respectively, of end plate sites whose AChRs had been labeled with 125I-alpha-bungarotoxin (alpha-butx). The results show that the metabolic stability of the AChRs in ectopic clusters is reversibly increased by muscle activity even when innervation is eliminated very early in development. 1 d of stimulation is sufficient to stabilize the AChRs in ectopic AChR clusters. Muscle stimulation also produced an increase in the number of AChRs at early denervated end plates. Activity-induced cluster growth occurs mainly by an increase in area rather than in AChR density, and for at least 10 d after denervation is comparable to that in normally developing ectopic end plates. The possible involvement of AChR stabilization in end plate growth is discussed.

scholarly journals Degradation rates of acetylcholine receptors can be modified in the postjunctional plasma membrane of the vertebrate neuromuscular junction.

1986 ◽  
Vol 103 (4) ◽  
pp. 1399-1403 ◽  
Author(s):  
M M Salpeter ◽  
D L Cooper ◽  
T Levitt-Gilmour
Keyword(s):  
Neuromuscular Junction ◽  
Acetylcholine Receptors ◽  
Degradation Rate ◽  
Postsynaptic Membrane ◽  
Nerve Crush ◽  
Adult Mice ◽  
Vertebrate Muscle ◽  
Degradation Rates ◽  
Alpha Bungarotoxin ◽  
Two Populations

Denervation of vertebrate muscle causes an acceleration of acetylcholine receptor turnover at the neuromuscular junction. This acceleration reflects the composite behavior of two populations of receptors: "original receptors" present at the junction at the time of denervation, and "new receptors" inserted into the denervated junction to replace the original receptors as they are degraded (Levitt, T. A., and M. M. Salpeter, 1981, Nature (Lond.), 291:239-241). The present study examined the degradation rate of original receptors to determine whether reinnervation could reverse the effect of denervation. Sternomastoid muscles in adult mice were denervated by either cutting or crushing the nerve, and the nerves either allowed to regenerate or ligated to prevent regeneration. The original receptors were labeled with 125I-alpha-bungarotoxin at the time of denervation, and their degradation rate followed by gamma counting. We found that when the nerve was not allowed to regenerate, the degradation decreased from a t1/2 of approximately 8-10 d to one of approximately 3 d (as reported earlier for denervated original receptors) and remained at that half-life throughout the experiment (approximately 36 d). If the axons were allowed to regenerate (which occurred asynchronously between day 14 and day 30 after nerve cut and between day 7 and 13 after nerve crush), the accelerated degradation rate of the original receptors reverted to a t1/2 of approximately 8 d. Our data lead us to conclude that the effect of denervation on the degradation rate of original receptors can be reversed by reinnervating. The nerve can thus slow the degradation rate of receptors previously inserted into the postsynaptic membrane.

scholarly journals Acetylcholine receptors in regenerating muscle accumulate at original synaptic sites in the absence of the nerve.

1979 ◽  
Vol 82 (2) ◽  
pp. 412-425 ◽  
Author(s):  
S J Burden ◽  
P B Sargent ◽  
U J McMahan
Keyword(s):  
Skeletal Muscle ◽  
Horseradish Peroxidase ◽  
Basal Lamina ◽  
Acetylcholine Receptors ◽  
Structural Organization ◽  
Neuromuscular Junctions ◽  
Muscle Fibers ◽  
Nerve Terminals ◽  
Alpha Bungarotoxin

We examined the role of nerve terminals in organizing acetylcholine receptors on regenerating skeletal-muscle fibers. When muscle fibers are damaged, they degenerate and are phagocytized, but their basal lamina sheaths survive. New myofibers form within the original basal lamina sheaths, and they become innervated precisely at the original synaptic sites on the sheaths. After denervating and damaging muscle, we allowed myofibers to regenerate but deliberately prevented reinnervation. The distribution of acetylcholine receptors on regenerating myofibers was determined by histological methods, using [125I] alpha-bungarotoxin or horseradish peroxidase-alpha-bungarotoxin; original synaptic sites on the basal lamina sheaths were marked by cholinesterase stain. By one month after damage to the muscle, the new myofibers have accumulations of acetylcholine receptors that are selectively localized to the original synaptic sites. The density of the receptors at these sites is the same as at normal neuromuscular junctions. Folds in the myofiber surface resembling junctional folds at normal neuromuscular junctions also occur at original synaptic sites in the absence of nerve terminals. Our results demonstrate that the biochemical and structural organization of the subsynaptic membrane in regenerating muscle is directed by structures that remain at synaptic sites after removal of the nerve.

scholarly journals Acetylcholine receptor aggregation parallels the deposition of a basal lamina proteoglycan during development of the neuromuscular junction.

1984 ◽  
Vol 99 (5) ◽  
pp. 1769-1784 ◽  
Author(s):  
M J Anderson ◽  
F G Klier ◽  
K E Tanguay
Keyword(s):  
Neuromuscular Junction ◽  
Basal Lamina ◽  
Acetylcholine Receptors ◽  
Time Course ◽  
Synapse Formation ◽  
Muscle Cells ◽  
Postsynaptic Membrane ◽  
Receptor Aggregation ◽  
Nerve Muscle ◽  
Alpha Bungarotoxin

To determine the time course of synaptic differentiation, we made successive observations on identified, nerve-contacted muscle cells developing in culture. The cultures had either been stained with fluorescent alpha-bungarotoxin, or were maintained in the presence of a fluorescent monoclonal antibody. These probes are directed at acetylcholine receptors (AChR) and a basal lamina proteoglycan, substances that show nearly congruent surface organizations at the adult neuromuscular junction. In other experiments individual muscle cells developing in culture were selected at different stages of AChR accumulation and examined in the electron microscope after serial sectioning along the entire path of nerve-muscle contact. The results indicate that the nerve-induced formation of AChR aggregates and adjacent plaques of proteoglycan is closely coupled throughout early stages of synapse formation. Developing junctional accumulations of AChR and proteoglycan appeared and grew progressively, throughout a perineural zone that extended along the muscle surface for several micrometers on either side of the nerve process. Unlike junctional AChR accumulations, which disappeared within a day of denervation, both junctional and extrajunctional proteoglycan deposits were stable in size and morphology. Junctional proteoglycan deposits appeared to correspond to discrete ultrastructural plaques of basal lamina, which were initially separated by broad expanses of lamina-free muscle surface. The extent of this basal lamina, and a corresponding thickening of the postsynaptic membrane, also increased during the accumulation of AChR and proteoglycan along the path of nerve contact. Presynaptic differentiation of synaptic vesicle clusters became detectable at the developing neuromuscular junction only after the formation of postsynaptic plaques containing both AChR and proteoglycan. It is concluded that motor nerves induce a gradual formation and growth of AChR aggregates and stable basal lamina proteoglycan deposits on the muscle surface during development of the neuromuscular junction.

MYASTHENIA GRAVIS: A SERUM FACTOR BLOCKING ACETYLCHOLINE RECEPTORS OF THE HUMAN NEUROMUSCULAR JUNCTION

The Lancet ◽  
1975 ◽  
Vol 305 (7907) ◽  
pp. 607-609 ◽  
Author(s):  
AdamN Bender ◽  
W King Engel ◽  
StevenP Ringel ◽  
MathewP Daniels ◽  
Zvi Vogel
Keyword(s):  
Neuromuscular Junction ◽  
Myasthenia Gravis ◽  
Acetylcholine Receptors ◽  
Serum Factor

scholarly journals Processing of ARIA and release from isolated nerve terminals

1999 ◽  
Vol 354 (1381) ◽  
pp. 411-416 ◽  
Author(s):  
Bomie Han ◽  
Gerald D. Fischbach
Keyword(s):  
Neuromuscular Junction ◽  
Action Potential ◽  
Acetylcholine Receptors ◽  
Molecular Layer ◽  
Postsynaptic Membrane ◽  
High Density ◽  
Small Contribution ◽  
Presynaptic Nerve Terminal ◽  
Voltage Gated

The neuromuscular junction is a specialized synapse in that every action potential in the presynaptic nerve terminal results in an action potential in the postsynaptic membrane, unlike most interneuronal synapses where a single presynaptic input makes only a small contribution to the population postsynaptic response. The postsynaptic membrane at the neuromuscular junction contains a high density of neurotransmitter (acetylcholine) receptors and a high density of voltage–gated Na + channels. Thus, the large acetylcholine activated current occurs at the same site where the threshold for action potential generation is low. Acetylcholine receptor inducing activity (ARIA), a 42 kD protein, that stimulates synthesis of acetylcholine receptors and voltage–gated Na + channels in cultured myotubes, probably plays the same roles at developing and mature motor endplates in vivo . ARIA is synthesized as part of a larger, transmembrane, precursor protein called proARIA. Delivery of ARIA from motor neuron cell bodies in the spinal cord to the target endplates involves several steps, including proteolytic cleavage of proARIA. ARIA is also expressed in the central nervous system and it is abundant in the molecular layer of the cerebellum. In this paper we describe our first experiments on the processing and release of ARIA from subcellular fractions containing synaptosomes from the chick cerebellum as a model system.

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