The success of axon regeneration after nerve injury should be judged by the extent to which the target organs regain their function. Recovery of muscle contraction involves axon regeneration, ...reestablishment of nerve-muscle connections, recovery of transmission, and muscle force. All these processes were investigated under the same experimental conditions and correlated in order to better understand their time-course and interdependence. The sciatic nerve of a rat was crushed in the thigh. The ingrowth of regenerating motor axons into the soleus (SOL) and extensor digitorum longus (EDL) muscles was monitored by measuring the activity of choline acetyltransferase (ChAT), a marker enzyme for cholinergic nerve terminals, in the muscles. The electron microscopic cytochemistry of acetylcholine esterase (AChE) was used to estimate the reestablishment of neuromuscular junctions in these two muscles. The recovery of muscle contraction was followed by measuring the force of isometric contraction in the triceps surae muscle in vivo. The pattern of ChAT recovery during reinnervation was similar in the EDL and SOL. The statistically significant increase of ChAT activity in these muscles, 14 d after the nerve crush, signified the entry of regenerating axons into the calf muscles. Electron microscopic cytochemistry revealed the first small nerve endings in contact with the denervated end plates 12 d after denervation. Subsequently, the number of reinnervated motor end plates and the surface area of the neuromusclar junctions steadily increased. The recovery of muscle force started between d 14 and 21 after the nerve crush. Thirty-five days after denervation, the difference between the muscle force of the reinnervated muscle and the control became statistically insignificant. Morphological normalization of the motor end plates was practically complete 33 d after denervation, concomitant with the normalization of the muscle force. At that time, however, ChAT activity in both muscles was still clearly subnormal (33.5% in EDL and 45% of the control in SOL) and therefore does not reflect the true extent of muscle force recovery. Yet, it seems that in spite of this, the regenerated nerve terminals contained sufficient amounts of acetylcholine (ACh) to trigger normal muscle contractions.
An analytic method for stabilization of the unstable orbits of a complex system is applied to the problem of ferroresonance in power systems. The method is based on the feedback control theory ...proposed by Pyragas (1992). Simulation results are presented illustrating transitions from unstable, chaotic, to stable, periodic, orbits. The stability was evaluated using the largest Lyapunov exponent. In this way, an efficient approach to the damping and control of the ferroresonant chaotic oscillations, which can arise in high-voltage terminal equipment, is presented.
A prototype of a diagnostic system for quality end-tests of vacuum cleaner motors is presented. The core of the system are four modules for features extraction based on vibration analysis, sound ...analysis, analysis of commutation and check of parity relations respectively. The symptoms resulting there from are processed by a reasoning module relying on the Transferable Belief Model (TBM). The result of such a comprehensive diagnostic procedure is detection of faulty motors and localisation of tentative fault origins along with accompanying belief measures. Attributes of the system performance and an excerpt from results obtained in an experimental study over a series of motors are provided.
The paper presents reconstruction of cardiovascular dynamics based on analysis of signals measured from various functions of the cardiovascular system on different sites of the human body. All ...signals comprise the same characteristic peaks in their frequency spectra. The time variations of these peaks are illustrated using wavelet transform. To further reveal the dynamic properties of the cardiovascular system the signals are analysed in the phase space by calculating the correlation integral and Lyapunov exponents. The correlation integrals of measured signals differ from those of their surrogates, and the Lyapunov exponents appear in pairs. The obtained results suggest the complex and deterministic nature of the system that governs cardiovascular dynamics. A model of coupled oscillators is proposed to describe the dynamics of the cardiovascular system.
The use of a functional neuromuscular stimulation (FNS) device can have therapeutic effects that persist when the device is not in use. Clinicians have reported changes in both voluntary and ...electrically assisted neuromuscular function and improvements in the condition of soft tissue. Motor recovery has been observed in people with incomplete spinal cord injury, stroke, or traumatic brain injury after the use of motor prostheses. Improvement in voluntary dorsiflexion and overall gait pattern has been reported both in the short term (several hours) and permanently. Electrical stimulation of skin over flexor muscles in the upper limb produced substantial reductions for up to 1 h in the severity of spasticity in brain-injured subjects, as measured by the change in torque generation during ramp-and-hold muscle stretch. There was typically an aggravation of the severity of spasticity when surface stimulation reached intensities sufficient to also excite muscle. Animals were trained to alter the size of the H-reflex to obtain a reward. The plasticity that underlies this operantly conditioned H-reflex change includes changes in the spinal cord itself. Comparable changes appear to occur with acquisition of certain motor skills. Current studies are exploring such changes in humans and animals with spinal cord injuries with the goal of using conditioning methods to assess function after injury and to promote and guide recovery of function. A better understanding of the mechanisms of neural plasticity, achieved through human and animal studies, may help one to design and implement FNS systems that have the potential to produce beneficial changes in the subject's central nervous systems.
In spite of the extensive clinical work reported in the area of electrical wound healing, electrical stimulation to augment chronic wound repair is still far from being widely accepted in clinical ...practice. Problems in designing clinical studies (size of the sample observed, control group, ethics of the procedure), evaluating treatment efficacy, rationales for use of the treatment, and unknown underlying mechanisms contribute to the aforementioned fact. In the present study, the authors evaluated low frequency electrical current for its beneficial effects in pressure ulcer management. Seventy-three spinal cord injured patients with 109 pressure ulcers participated in the study. Patients were randomly assigned to a control group receiving conventional treatment of their ulcers, or to a stimulation group, in which the ulcers were additionally treated with low frequency pulsed current. A comparison of the two groups showed significantly higher average healing rate for the stimulated group. Patients from the control group had the opportunity of crossing over to the stimulation group after the required control period of four weeks. This group (the crossover group) was analyzed separately. In all but one ulcer out of 20, an improvement in the healing process was observed after electrical stimulation was initiated.< >
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