Biomedical subjects

N F Zilber-Gachelin

Publications and source records attributed to N F Zilber-Gachelin.

12 recordsLinked to original sources

PubMed1981

Patterns of motor innervation in the pectoral muscle of adult Xenopus laevis: evidence for possible synaptic remodelling.

1. An anatomical and electrophysiological study was performed on the pectoral muscle of Xenopus laevis. 2. Silver-impregnated preparations revealed immature endings, collateral and terminal sprouting and signs of synaptic regression. 3. Twenty percent of the fibres received a dual innervation from two different nerves. The synapses of 25% of these fibres are formed in close vicinity. 4. Some of the singly innervated and most of the dually innervated end-plates generated only subthreshold electrical activity. Synaptic efficacy in dually innervated muscle fibres with closely spaced or distant endings was, on the average, one third and two thirds, respectively, of that obtained in singly innervated fibres. 5. Fibres with subthreshold electrical activity displayed normal ACh sensitivity. 6. The existence of non-transmitting synapses, of dually innervated end-plate sites and of morphological signs of the sprouting of new endings and the degeneration of old ones suggests that synaptic remodelling may occur in normal adult muscles.

Acetylcholine↗

PubMed1981

Interaction between motor axons from two different nerves reinnervating the pectoral muscle of Xenopus laevis.

1. An electrophysiological and morphological study of sprouting and regeneration of motor nerves has been performed in the dually innervated pectoral muscle of Xenopus laevis. 2. Section of one of the nerves induced axon sprouting in the intact nerve. Synapse formation by the sprouting axons was slow since the intact nerve took more than 3 months to increase its field of innervation by 70%. The rate of axon regeneration was faster than that of axon sprouting since the cut nerve reinnervated its former territory in less than 1 month. 3. At early stages of synapse formation the sprouted or regenerated endings were poorly branched but any terminal branches were, as a rule, longer than normal. Signs of degeneration and replacement of endings have been observed. 4. Low levels of transmitter release persisted for several months in newly formed endings. This depression was more pronounced at the endings formed outside the normal field of innervation of the nerve. 5. Poly-innervated muscle fibres have been observed during reinnervation by regenerated or sprouted axons. Their number decreases gradually in the months that follow the beginning of reinnervation. Synaptic efficacy was lower at poly than at mono-innervated muscle fibres. At doubly innervated spots and at separated spots on the same fibre average end-plate potential (e.p.p.) amplitude was 1/3 and 2/3 respectively of that recorded at singly innervated fibres. 6. Electrophysiological and morphological data have been compared at individual doubly innervated end-plate sites. End-plate potential amplitude was positively correlated with the degree of ending development. 7. Sprouted endings remain functional after periods of reinnervation of 30 months, although signs of regression have been observed. These are probably mediated by spontaneous degeneration of the terminals and replacement by endings from the regenerating nerve.

Animals↗

PubMed1976

Further investigations on the effect of denervation and pH on the conductance change at the neuromuscular junction of the frog.

Currents induced by acetylcholine application at the voltage-calmped frog end-plate, were measured over a large range of membrane potentials. Due to a non-linearity of the current-voltage curve, the directly-measured reversal potential may be quite different from the value classically determined by extrapolation (linear regression) of the measurements made at potentials below spike threshold. Denervation and changes of external pH were found to alter the shape of the current-voltage relation, but not the directly-measured reversal potential. These effects are tentatively explained on the basis of changes in the ratio: time-to-peak for [ACh] reaching the receptors/mean life-time of the open synaptic channels. Possible changes in cooperativity are also considered.

Acetylcholine↗

PubMed1974