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Biomedical subjects

J Chapron

Publications and source records attributed to J Chapron.

6 recordsLinked to original sources
PubMed1991

The effect of tetanus toxin on in vitro synaptogenesis.

Cultures of spinal cord neurons and cocultures of rat embryo neurons and muscle cells have been studied in the presence of tetanus toxin (TT) at a concentration of 40 micrograms/ml of medium. TT strongly stimulated neurite outgrowth, notably branching from the cell bodies. In addition it induced a marked, overall increase in acetylcholine receptor (AChR), but inhibited focalisation of AChR and acetylcholinesterase (AChE) at the synaptic sites. TT seems to act on neurite emergence, on the neuronal factor(s) controlling AChE and AChR concentrations, and on the factor(s) modulating degradation and/or synthesis of AChR.

Acetylcholinesterase↗
PubMed1991

Fura-2 imaging of spontaneous and electrically induced oscillations of intracellular free Ca2+ in rat myotubes.

Rat myotubes have a resting [Ca2+]i of about 82 nM. Myotubes 3-5 days old (quiescent myotubes) display electrically induced and spontaneous transients in the intracellular concentration of free Ca2+ ions ([Ca2+]i) uncoupled to any detectable contraction. By contrast, 1- to 2-day-old myotubes are insensitive to electrical stimuli and, after 6 days in culture, stimulated myotubes always show [Ca2+]i transients and twitch contractions. The spatial distribution of [Ca2+]i variations in quiescent myotubes is heterogeneous, local increases in [Ca2+]i being mainly observed near the periphery of the cell. The small effect of different external Ca2+ concentrations and of Cd2+ on the amplitude of the [Ca2+]i oscillation indicates that the main source of Ca2+ may be the sarcoplasmic reticulum. This conclusion is supported by the close similarity between electrically induced and caffeine-induced [Ca2+]i maps. These findings suggest that, at an early stage of myotube ontogenesis, a part of the excitation/contraction coupling, as membrane ionic channels, voltage sensors and Ca2+ release and reuptake mechanisms, is functional but, apparently, still uncoupled to the contractile machinery.

Animals↗
PubMed1989

In vitro synaptic maturation.

Cocultures of spinal cord neurons and muscle cells taken from rat embryos were used for in vitro reproduction of embryonic synapses. This system did not display the synaptic maturation characteristics of postnatal development: decreased multiple innervation and the presence of a developed subneural apparatus. Studies on cultures consisting of 3 cell types (muscle cells, nerve cells, Schwann cells), or on co-cultures (muscle cells, nerve cells), in the presence or absence of a monoclonal antibody directed against an antigen from Schwann cells, have shown that Schwann cells participate in synaptic maturation and in the elimination of superfluous synapses. The synapses were visualised for optical microscopy by co-localisation of acetylcholinesterase (AChE) spots and acetylcholine receptor (AChR) clusters.

Animals↗
PubMed1988

Does the Schwann cell synthesize a molecule concentrated at the neuromuscular synapse?

The monoclonal antibody 6.17 binds to a molecule concentrated at the neuromuscular synapse. We tested it in various experimental conditions and all along the normal muscle development. It seems that the 6.17 corresponding antigen, suspected of Schwann cell origin, would be later localised in the synaptic space, but not in the basal lamina. Thus, the Schwann cell might participate to the synthesis of some synaptic molecules.

Animals↗