ABSTRACT
A silver stain was used to investigate the regeneration of nerve terminals in mouse diaphragm, superior gluteus and tensor fasciae latae (TFL) muscles following nerve crush injury at different ages (9-530 days). The development of myelinated terminal branches and the development and elimination of terminal sprouts were little affected by age or muscle type following reinnervation. However, multiple axonal innervation developed on up to 50% of the gluteus and TFL muscle fibres, and this was subsequently eliminated only in the youngest animals.
Subject(s)
Aging , Muscles/innervation , Nerve Regeneration , Neuromuscular Junction/physiology , Synapses/physiology , Animals , Animals, Newborn/physiology , Axons/physiology , Mice , Nerve Fibers/physiology , Nerve Fibers, Myelinated/physiology , Neuromuscular Junction/classificationABSTRACT
The mechanism underlying rhythmical aggregate activity of a population of neural or neuromuscular elements is examined in this report. By making use of the spectral properties of stochastic processes (Papoulis, 1965), it is shown that such population rhythms are the inevitable effect of the rhythmical activities of the individual elements, irrespective of the phase relations of the latter. This result applies to both "discrete" signals, such as spike trains, and "continuous" ones, such as membrane potential fluctuations. It has implications regarding the generation of common physiological rhythms and the preservation of rhythms when converging activity of one of the above two types is transformed into activity of the other type.
Subject(s)
Electroencephalography , Neuromuscular Junction/physiology , Neurons/physiology , Action Potentials , Alpha Rhythm , Animals , Models, Neurological , Neuromuscular Junction/classification , Neurons/classification , Stochastic Processes , Synapses/classification , Synapses/physiologyABSTRACT
Motor units of the cat peroneus tertius muscle were systematically analyzed using the criteria established by Burke et al. (1973). On the basis of their speed of contraction and resistance to fatigue, 121 (97%) of 125 motor units examined in ten adult cats could be classified as belonging to one of four types: fast-fatigable (FF), fast-resistant (FR), fast-intermediate (FI), and slow-resistant (S). Peroneus tertius was found to contain 30% FF motor units, 9% FI units, 39% FR units, and 22% S units. Contraction times of fast motor units (FF, FR, and FI) ranged from 15 to 27 ms and those of S units from 26 to 42 ms. The mean tetanic tensions were 37 g for FF units, 29 g for FI units, 7.5 g for FR units, and 1.1 g for S units. Fast motor units displayed considerable post-tetanic potentiation of twitch tension. Under similar conditions of stimulation, FF units appeared able to potentiate more and faster than FR units.
Subject(s)
Hindlimb/innervation , Muscle Contraction , Muscles/innervation , Neuromuscular Junction/physiology , Animals , Axons/physiology , Electric Stimulation , Evoked Potentials , Humans , Motor Neurons/physiology , Neural Conduction , Neuromuscular Junction/classification , Spinal Nerve Roots/physiologyABSTRACT
The results of this study and its precedents suggest that the tetrapartite classification scheme might have universal applicability to at least the muscle units of cat hindlimb muscles and perhaps any mammalian muscle in which fiber typing reveals the presence of FG, FI, FOG, and type SO fibers. A possible exception to this generalization involves a small (n = 18) but thoroughly examined sample of muscle units from the first deep lumbrical muscle of the cat's foot, which led Kernell et al. (30) to conclude that the FF, FR, and S classification scheme was not directly applicable to that muscle. However, histochemical fiber typing is not yet available for that muscle. Furthermore, more extensive sampling, use of a different stimulation regime in the fatigue test, and a more detailed analysis of the sag property might well reveal that the tetrapartite classification scheme is indeed appropriate for units of cat foot muscles.
