The Experts below are selected from a list of 291 Experts worldwide ranked by ideXlab platform
Jan Holsheimer - One of the best experts on this subject based on the ideXlab platform.
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Three-dimensional topography of the motor Endplates of the rat gastrocnemius muscle.
Muscle & nerve, 2005Co-Authors: Dimiter Prodanov, Marie-anne Thil, Enrico Marani, Jean Delbeke, Jan HolsheimerAbstract:Spatial distribution of motor Endplates affects the shape of the electrical activity recorded from muscle. In order to provide information for realistic models of action potential propagation within muscles, we assembled three-dimensional maps of the motor Endplates of the rat medial gastrocnemius (MGM) and lateral gastrocnemius (MGL) muscles. The maps were assembled from histological cross sections stained for acetylcholinesterase activity. Within MGL, the motor Endplates formed three columns along its longitudinal axis. Within MGM, the motor Endplates were arranged in a leaf-like body that shifted obliquely from proximal to distal. As inferred from the proximo-distal distribution of the cross-sectional projection area, the majority of the motor Endplates were concentrated in the middle of MGL and in the distal third of MGM. Regions of maximal motor Endplate concentration are considered most suitable for injections of neuroactive substances, such as neuronal tracers. The assembled maps of the gastrocnemius muscles can be used as guides for such injections within the motor Endplate zones. Muscle Nerve, 2005
Richard R Ribchester - One of the best experts on this subject based on the ideXlab platform.
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co regulation of synaptic efficacy at stable polyneuronally innervated neuromuscular junctions in reinnervated rat muscle
The Journal of Physiology, 1999Co-Authors: Ellen M Costanzo, Jacqueline A Barry, Richard R RibchesterAbstract:Intracellular recordings and quantal analysis of synaptic transmission were made at neuromuscular junctions receiving stable convergent innervation in reinnervated rat lumbrical muscles, following recovery from chronic nerve conduction block. The polyneuronally innervated motor Endplates (π-junctions) were identified by vital staining of lateral plantar nerve (LPN) and sural nerve (SN) motor terminals, using the activity-dependent staining properties of the aminostyryl dyes RH414 and FM1-43, respectively. Endplate depolarisation and quantal content per unit area varied by more than a factor of ten (≈0.1-1.4 quanta μm−2) between fibres. However, the stable π-junctions produced nearly equivalent Endplate depolarisations and quantal content per unit area, suggesting that synaptic strengths were co-regulated at these motor Endplates. Quantal content per unit area was also independent of the size of individual synaptic inputs, or whether one, both or neither input was judged sufficient to produce suprathreshold or subthreshold Endplate depolarisations. Simultaneous excitation of convergent LPN and SN inputs from some π-junctions resulted in profound non-linear summation, and in some cases complete occlusion of the response of the smaller input. The amplitude of the smaller, test responses recovered with a time constant of 2.1 ± 0.5 ms (mean ±s.e.m.) on varying the interval between paired stimuli, of similar order to the time constant of repolarisation of the conditioning Endplate potential. The data show that it is not necessary for a motor nerve terminal to occupy most of an Endplate, or to produce a suprathreshold response in order to become stable. The occlusion of linear summation, similar to that described previously at polyneuronal junctions in neonates, suggests that convergent inputs comprising interdigitated synaptic boutons evoke self-contained synaptic responses at Endplates, and that these are non-co-operative with respect to overall Endplate depolarisation or safety margin for synaptic transmission. Activity exerts powerful, selective effects on the organisation, stability and strength of synaptic connections in all parts of the nervous system, including neuromuscular junctions (Lohof et al. 1996; Sanes & Lichtman, 1999). For example, neonatal rat muscle fibres are innervated at single motor Endplates by motor nerve terminals supplied by several motoneurones (polyneuronal innervation; π-junctions), and a similar pattern is re-established in adult muscle after nerve injury and regeneration (Brown et al. 1976; Betz et al. 1979; Ribchester, 1988). With time, synaptic boutons and axonal inputs are progressively eliminated, eventually leaving most Endplates innervated by only one motor axon (Gan & Lichtman, 1998). Progressive and disproportionate weakening of synaptic transmission, induced by differences in pre- and postsynaptic activity, has been presumed to underlie this competitive process (Ribchester & Taxt, 1983; Balice-Gordon & Lichtman, 1994; Coleman et al. 1997). However, activity may not be sufficient to induce elimination from all π-junctions. Previous studies of paralysed neonatal or reinnervated adult muscle suggest that significant polyneuronal innervation persists once activity resumes (Hoffman, 1953; Brown et al. 1982; Barry & Ribchester, 1995). The properties that allow convergent synapses of different size and efficacy to persist at a motor Endplate are unknown. Equally, it is unclear whether apparently stable, convergent synaptic inputs in reinnervated muscles may in fact be slowly undergoing heterosynaptic repression and progressive elimination, as in development. If small synaptic inputs to π-junctions in reinnervated adult muscles were actually undergoing elimination then they should be disproportionately weak: that is, transmitter release per unit area should be less than normal; or the synapses should show a reduced receptor density; or a combination of both (Balice-Gordon & Lichtman, 1994; Coleman et al. 1997). To test this prediction, we have used vital dyes and intracellular recording to correlate fractional Endplate occupancy with synaptic efficacy, measured in terms of overall depolarisation and transmitter release per unit area. We also studied the interactions between convergent inputs, by comparing the amplitudes of the Endplate potential responses evoked by separate and combined stimulation. Our findings indicate that converging inputs to reinnervated mammalian neuromuscular junctions are indeed stable; that these stable inputs have nearly equivalent synaptic strengths; that the strengths of converging inputs are regulated up or down together; that it is not necessary for small inputs to generate suprathreshold responses in muscle fibres in order to become stable; but that the synaptic responses derived from different inputs can be largely self-contained, and mutually occlusive. A preliminary account of these data was presented to The Physiological Society (Costanzo et al. 1999).
H. Zucker - One of the best experts on this subject based on the ideXlab platform.
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Persistence of nerve sprouting with features of synapse remodelling in soleus muscles of adult mice
Neuroscience, 2003Co-Authors: Anton Wernig, J.j. Carmody, A.p. Anzil, E. Hansert, M. Marciniak, H. ZuckerAbstract:Abstract An increase in the number of nerve branches of the unmyelinated axon terminals with increasing age was observed in normal adult mouse motor Endplates. In addition, ultrastructural investigation revealed signs of nerve retraction. A combined light and electron microscopic investigation was performed on zinc-iodine-osmium stained Endplates in soleus muscles. The number of branch points in a synapse, Endplate length and muscle fiber diameter were evaluated in “young adult” (3 months) and adult (6 and 11 months) mice. For all 3 parameters, 3-month-old animals had the lowest values. Eleven-month-old animals had more branch points and larger Endplate lengths than 6-month-old animals while there was no significant difference in fiber diameters. Branch point numbers and Endplate length were correlated in each muscle while fiber diameters did not correlate with any of the other parameters. The ultrastructure of 15 thin nerve branches—likely candidates for new branches—was investigated in serial sections and in 14 of them synaptic contacts were found. Near such contacts, empty gutters, possibly abandoned former synaptic sites, were present in several cases. It is concluded that there is continual nerve sprouting in synapses of adult mice and that sprouts form synaptic contacts. The possible signs of nerve retraction observed indicate that, as in the frog, synaptic contacts in mouse muscles undergo some continual remodelling.
I I Krivoi - One of the best experts on this subject based on the ideXlab platform.
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early Endplate remodeling and skeletal muscle signaling events following rat hindlimb suspension
Journal of Cellular Physiology, 2018Co-Authors: Alexander V Chibalin, Boubacar Benziane, Guzalija F Zakyrjanova, V V Kravtsova, I I KrivoiAbstract:Motor Endplates naturally undergo continual morphological changes that are altered in response to changes in neuromuscular activity. This study examines the consequences of acute (6-12 hr) disuse following hindlimb suspension on rat soleus muscle Endplate structural stability. We identify early changes in several key signaling events including markers of protein kinase activation, AMPK phosphorylation and autophagy markers which may play a role in Endplate remodeling. Acute disuse does not change Endplate fragmentation, however, it decreases both the individual fragments and the total Endplate area. This decrease was accompanied by an increase in the mean fluorescence intensity from the nicotinic acetylcholine receptors which compensate the Endplate area loss. Muscle disuse decreased phosphorylation of AMPK and its substrate ACC, and stimulated mTOR controlled protein synthesis pathway and stimulated autophagy. Our findings provide evidence that changes in Endplate stability are accompanied by reduced AMPK phosphorylation and an increase in autophagy markers, and these changes are evident within hours of onset of skeletal muscle disuse.
Dimiter Prodanov - One of the best experts on this subject based on the ideXlab platform.
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Three-dimensional topography of the motor Endplates of the rat gastrocnemius muscle.
Muscle & nerve, 2005Co-Authors: Dimiter Prodanov, Marie-anne Thil, Enrico Marani, Jean Delbeke, Jan HolsheimerAbstract:Spatial distribution of motor Endplates affects the shape of the electrical activity recorded from muscle. In order to provide information for realistic models of action potential propagation within muscles, we assembled three-dimensional maps of the motor Endplates of the rat medial gastrocnemius (MGM) and lateral gastrocnemius (MGL) muscles. The maps were assembled from histological cross sections stained for acetylcholinesterase activity. Within MGL, the motor Endplates formed three columns along its longitudinal axis. Within MGM, the motor Endplates were arranged in a leaf-like body that shifted obliquely from proximal to distal. As inferred from the proximo-distal distribution of the cross-sectional projection area, the majority of the motor Endplates were concentrated in the middle of MGL and in the distal third of MGM. Regions of maximal motor Endplate concentration are considered most suitable for injections of neuroactive substances, such as neuronal tracers. The assembled maps of the gastrocnemius muscles can be used as guides for such injections within the motor Endplate zones. Muscle Nerve, 2005