Histopathologic features of the vagus nerve after electrical stimulation in swine

This paper describes the histological features of the vagus nerve after its stimulation with an electrostimulation system that is being developed for morbid obesity treatment. An electrostimulation system was implanted laparoscopically around the ventral vagal trunk of five Large White female pigs (49.63+/-1.94 kg.). Vagal nerve stimulation was performed by continuous constant voltage current pulses. Thoracic samples of both ventral and dorsal vagal trunks were obtained thoracoscopically one month after implantation. Animals were sacrificed one month after thoracoscopic vaguectomy. Tissue samples were then harvested from the vagal nerve at the implantation site, 1cm cranial to it, thoracic portion of ventral and dorsal vagal trunks, sub-diaphragmatic dorsal vagal trunk, left and right vagus nerves. Specimens were analysed with light microscope. The severity of the lesions was graded from 0 to 4 (0: no lesion, 1: mild, 2: moderate, 3: severe and 4: extremely severe), taking into account fibrosis, vascularization, necrosis, fiber degeneration and inflammation. Electrode implantation resulted in thickened epineurium and endoneural connective tissue. The greatest lesion score was evidenced at the leads implantation site in the ventral vagal trunk, followed by, in order of decreasing lesion severity, left vagus nerve, thoracic portion of ventral vagal trunk, subdiaphragmatic dorsal vagal trunk, thoracic portion of dorsal vagal trunk and right vagus nerve. The stimulation device used in this study caused connective tissue growth, greatest in the samples located closer to the implantation site. However, there was no sign of altered vascularization in any studied specimen.     

Electrical stimulation in multiple sclerosis. Comparison of transcutaneous electrical stimulation and epidural spinal cord stimulation

Forty-nine multiple sclerosis patients with bladder symptoms and/or walking disability were subjected to a therapeutic trial with electrical spinal cord stimulation and transcutaneous electrical stimulation, a second aim being to compare these two treatments. A clear subjective improvement in bladder symptoms was achieved in the majority of the cases, and this was substantiated by objective parameters. In a proportion of cases a more moderate improvement seems to have been achieved in a variety of symptoms. Transcutaneous electrical stimulation seems to be a useful selection procedure for later electrical spinal cord stimulation.     

Advances in functional electrical stimulation (FES)

This review discusses the advancements that are needed to enhance the effects of electrical stimulation for restoring or assisting movement in humans with an injury/disease of the central nervous system. A complex model of the effects of electrical stimulation of peripheral systems is presented. The model indicates that both the motor and sensory systems are activated by electrical stimulation. We propose that a hierarchical hybrid controller may be suitable for functional electrical stimulation (FES) because this type of controller acts as a structural mimetic of its biological counterpart. Specific attention is given to the neural systems at the periphery with respect to the required electrodes and stimulators. Furthermore, we note that FES with surface electrodes is preferred for the therapy, although there is a definite advantage associated with implantable technology for life-long use. The last section of the review discusses the potential need to combine FES and robotic systems to provide assistance in some cases.     

Chronic electrical stimulation of nongrafted and grafted skeletal muscles in rats

Our purpose was to determine the effects of chronic electrical stimulation on the structure and function of neve-intact grafts in rats. Fourteen days after grafting, extensor digitorum longus (EDL) grafts (n = 6) and nongrafted EDL muscles (n = 4) were stimulated 8 h/day at 10 Hz for 26 days. Measurements were made subsequently of cytochrome c concentration, capillary density, contraction and relaxation times, developed tension, and the resistance to fatigue. Compared with contralateral nonstimulated grafts, chronically stimulated grafts demonstrated a 65% greater cytochrome c concentration, 45% greater number of capillaries per millimeter squared, 30% greater resistance to fatigue, 35% longer contraction time, 30% longer relaxation time, and 30% lower maximum tetanic tension. The differences that resulted from the stimulation of nongrafted EDL muscles were significant but of less magnitude. Chronic stimulation of 8 h/day provided a mixed stimulus for adaptation that enhanced the metabolic and endurance characteristics of fibers in muscles and grafts, but decreased the total fiber cross-sectional area and development of force.     

Cross-education after one session of unilateral surface electrical stimulation of the rectus femoris

Thirty-six adult men were randomly assigned to a remote stimulation group (RS; n = 18) or control group (CTL; n = 18). The RS group unilaterally performed a 10-minute surface electrical stimulation program (frequency 100 Hz, impulse 300 micros, 10 seconds on/10 seconds off) on the rectus femoris of the non-dominant leg. The subjects of the CTL group relaxed for 10 minutes without performing any training. Immediately before and after the surface electrical stimulation program, the isometric strength and the electromyographic (EMG) and mechanomyographic (MMG) response of the dominant leg was measured for all subjects. The dominant leg of the RS group showed a significant increase in the isometric force (5.11%; P < 0.001) and EMG activity of the agonist muscle (4.67%; P < 0.05), whereas a decrease in EMG activity of the antagonist muscles was observed (-10.27%; P < 0.05). The MMG activity did not show any alteration. No significant changes were observed for the CTL group. These results indicate that one unilateral surface electrical stimulation session on the rectus femoris improves the efficiency of the inactive leg. At a practical level, the results open a new way to rehabilitate muscle-skeletal injuries, especially weak members that cannot do any physical work. In this case, the muscle strength (and physical efficiency) can be improved by passive electrostimulation training on the healthy member.     

Ultrastructural features of megasporogenesis inTorreya nucifera (Taxaceae)

In megasporogenesis ofTorreya nucifera (Taxaceae) more than one product of meiosis can start to germinate, a process previously observed inTaxus. Ultrastructural analysis ofT. nucifera revealed that this behaviour is cytologically determined by the presence of a transfer cell type wall-membrane apparatus and by the presence of uncommonly complex plasmalemmasomes in the megasporocyte. These features may determine a uniform supply of nutrients to the entire megasporocyte cytoplasm, so that after meiosis the germination potential is not restricted to the chalazal megaspore. Even if more than one product of meiosis can originate the female gametophyte in bothTaxus andTorreya, this process involves different ultrastructural aspects in the two species. In conclusion, the extension of the germination potential is a common characteristic to both species but it is most probably the result of some evolutionary convergence.     

Qualitative features of erythropoiesis in rabbits following multiple antigenic stimulation

Experiments were conducted on rabbits; a study was made of the influence of multiple antigen stimulation on the indices of erythropoiesis. Isotonic physiological saline was administered daily in control rabbits. The erythroid bone marrow series responded in the same direction both to the antigen and to the non-antigen stimulation. There was noted an increase of the percentage content of macrocytes, coinciding in time with reticulocytosis in the immunized animals at the second stage (the 50th day). Normalization of the character of the erythrocyte distribution occurred in the control group at this period. In case of empolyment of the antigen stimulation, the second stage can be regarded as the compensatory-regenerative response to the damaging action of the antigen.     

Recruitment,force and fatigue characteristics of quadriceps muscles of paraplegics isometrically activated by surface functional electrical stimulation

This study deals with the recruitment characteristics of unfatigued electrically stimulated quadriceps muscles of paraplegic subjects and with the time-dependent force output of these muscles under sustained stimulation conditions. Both these aspects of the performance of paralysed stimulated muscles were studied under isometric conditions and at different muscle lengths. The forces in the knee joint resulting from stimulation of the quadriceps were also calculated. Recruitment force curves due to a ramp-like stimulation function indicated a strong dependence on muscle length and demonstrated a sigmoid-shaped curve with three distinct regions: negligible force up to threshold stimulation intensity; rapid force increase; and levelling-off of the curve after which the force remains constant even though intensity is further increased. When normalized to the maximal force, recruitment was found to be independent of muscle length, generating a typical recruitment curve for every patient, under isometric stimulation. The peak forces were obtained at the same flexion angles previously published for normal subjects, but with much lower values. Muscle fatigue in tetanic isometric conditions, defined as the decrease in force due to sustained stimulation with fixed parameters, was found to be length dependent and to have a double exponential decay. The first is the acute force loss and is the more significant for functional purposes; the second is the more moderate and asymptotic region, in which partial force receovery in the form of bursts is observed.     

Septal nuclei in the mechanisms of lateral hypothalamic self stimulation in rabbits

Unilateral lesions of medial septal nucleus and lateral septal nuclei (dorsalis, intermedius, ventralis) decreased ipsilateral hypothalamic self-stimulation; the lesions of n. dorsalis, n. medialis and lateral septal nuclei (intermedius and ventralis) has the opposite effect on contralateral self-stimulation. The inhibition of ipsilateral self-stimulation was neither total nor permanent; 25-32% decrease in stimulation rate was seen, but behaviour returned to near-normal levels over a period of few days. In contrast, the augmentation of contralateral self-stimulation showed no significant change over the same period; in this case the 35-40% shift in stimulation rate was immediate and permanent. Bilateral lesions of septal nuclei had no effect if the initial level of self-stimulation rate was high and significantly increased self-stimulation.     

Atherosclerosis in rabbits induced by prolonged electrical stimulation of the hypothalamus]

The influence of prolonged electrical stimulation of rabbit hypothalamus on blood lipids and the development of atherosclerosis were studied. The negative emotional state observed during the electrical stimulation was accompanied by blood hyperlipemia and atherosclerosis development in 1/3 noncastrated and 2/3 castrated animals.