Functional Reinnervation of the Distal Hindlimb Muscles in Rats after Compression of the Sciatic Nerve

Chronic experiments (12 weeks long) were carried out on two groups of pubertate-age Wistar rats. The sciatic nerve in one hindlimb was compressed, and complex analysis of the dynamics of functional reinnervation of the distal hindlimb muscles was performed. We used videorecording of images of the feet in the course of locomotion for estimation of the level of functional reinnervation of the toe extensors (the technique was modified in our laboratory) and a tensometric technique (measuring of the contraction force of the toe flexors and ankle extensors in the course of realization of the burrowing instinct by the animals). In the first group of animals (n = 21), we studied the dynamics of recovery of the force developed by the toe flexors and ankle extensors and of the functional sciatic index after sciatic nerve traumatization with no additional pharmacological influences. In the second group (n = 29), the same indices were analyzed, but after single injections of gamma-hydroxybutyrate (GHB) into animals before compression of the sciatic nerve and within early and late (3–4 and 14 weeks, respectively) terms after such intervention. Within the first week after compression, the smallest loss of activity was observed in the toe flexors, as compared with that in the toe and ankle extensors. Significant functional reinnervation of the ankle and toe extensors (to 52 and 87%, respectively) was observed on the 3rd to 7th weeks after the nerve injury. Functional reinnervation of the toe flexors was characterized by a relatively greater initial force of concentrations and more rapid recovery than those of the ankle and toe extensors. Practically complete recovery of the functions of the toe flexors was observed on the 10th week, while that of the ankle extensors was found on the 12th week. To make clearer possible reasons for differences between the processes of recovery of functions of the flexor and extensor muscles, we analyzed the effects of GHB on the contractile activity of these muscle groups within different time intervals after traumatization. In the second animal group, injection of GHB before operation resulted in drops of the muscle contraction force. After injury of the right sciatic nerve and injection of GHB on the 3rd posttraumatic week, recovery of the contraction force of all the examined muscles on the side of operation was more considerable. The functional loss of the muscle force in the left (intact) hindlimb in this case was 10 and 7% for the ankle extensors and toe flexors, respectively. Single injections of GHB within a late posttraumatic period resulted in a relative decrease in the contraction force of both flexors and extensors, and the functional loss was the greatest (35%) in the toe flexors.     

Effect of electromagnetic radiation of millimeter range on restoration of motor activity after impairment of the sciatic nerve in the rat

The effect of low-intensity (10–12 mW/cm²) amplitude-modulated electromagnetic radiation (EMR) with a wavelength of 8.1 mm on restoration of motor activity of hindlimb after the sciatic nerve had been crushed was studied in rats (only the injured area was radiated). The recovery was found to be significantly accelerated by EMR: after a seven-week-long treatment by EMR, the mean amplitude of the extensor force developed by the hindlimb of the EMR-treated animals reached 62.3% of its initial value (recorded before the nerve had been crushed), while in the control group of animals it was equal to near 40%.Neirofiziologiya/Neurophysiology, Vol. 28, No. 1, pp. 3–6, January–February, 1996.     

Microvascular architecture of the pampiniform plexus-testicular artery system in the rat: a scanning electron microscope study of corrosion casts

Because the architectural and biochemical properties of skeletal muscle dictate its force, velocity, and displacement properties, the major extensors (triceps brachii) and flexors (biceps brachii, brachialis, and brachioradialis) of the elbow in a primate (cynomolgus, monkey) were studied. Functional cross-sectional areas (CSA) were calculated from muscle mass, mean fiber length (normalized to a 2.20 microns sarcomere length), and angle of fiber pinnation measurements from each muscle. Fiber-type distributions were determined and used as a gross index of the biochemical capacities of the muscle. The extensor group had a shorter mean fiber length (31 vs. 47 mm), a larger CSA (13 vs. 8 cm2), and a higher overall percentage of slow-twitch fibers (47 vs. 26%). Consequently, the elbow extensors had a relatively greater potential for force production and force maintenance than the flexors. In contrast, the flexors were designed to optimize their length-velocity potentials; i.e., they had relatively long fibers and a higher fast-twitch fiber composition than the extensors. These morphologic differences between antagonistic muscle groups should be considered when evaluating the motor control mechanisms regulating reciprocal movements about the elbow.     

A rat model of progressive isometric strength training

This study presents an isometric model of strength resistance training in rats. Seven rats were trained for five weeks with increasing load, once a day for six days per week while seven rats served as control group. Mechanical strength of the hindlimb muscle group was measured on anaesthetised rats with a force transducer linked to the Achilles tendon after electrical stimulation of the sciatic nerve. Training resulted in a 74 +/- 2% strength gain in experimental (E) vs control (C) rats and in a reduction of fatigability with no change in gastrocnemius, soleus and extensor digitorum longus weights. The fibres composition of the gastrocnemius showed a 50% increase of IIA fibres and a 17% fall of IIB fibres. Consequently, this new model of isometric training is suitable for physiological studies.     

Accelerated contractile function and improved fatigue resistance of calf muscles in newborn piglets with IUGR

Asymmetrical intrauterine growth restriction is denoted by disproportional reduction of muscle mass compared with body weight reduction. However, effects on contractile function or tissue development of skeletal muscles were not studied until now. Therefore, isometric force output of serial-stimulated hindlimb plantar flexors was measured in thiopental-anesthetized normal weight (NW) and intrauterine growth-restricted (IUGR) 1-day-old piglets under conditions of normal, reduced (aortic cross clamping), and reestablished (clamp release) blood supply (measured by colored microspheres technique). Furthermore, muscle fiber type distribution was determined after histochemical staining, specific muscle force of the plantar flexors [quotient from absolute force divided by muscle mass (N/g)] was calculated, and glycogen content and morphometric data of the investigated muscles were estimated. Regional blood flow of hindlimb muscles was similar in NW (6 +/- 2 ml. min(-1). 100 g(-1)) and IUGR piglets (8 +/- 1 ml. min(-1). 100 g(-1)). Isometric muscle contractions induced a marked increase in regional blood flow of 4.1-fold in NW and 5-fold in stimulated hindlimb muscles of IUGR piglets (baseline blood flow). Specific force of NW piglet muscles (5.2 +/- 0.2 N/g) was significantly lower than IUGR piglet muscles (6.1 +/- 0.6 N/g; P < 0.05). Isometric muscle contractions (NW: 32.7 +/- 4.7 N; IUGR: 21.7 +/- 4.0 N) resulted in a higher rate of force decrease in the calf muscles of NW animals compared with IUGR piglets (8 +/- 2 vs. 3 +/- 1%; P < 0. 01). Functional restoration of contractile performance after hindlimb recirculation was nearly complete in IUGR piglets (98 +/- 1%), whereas in NW piglets a deficit of 9 +/- 3% was found (P < 0. 01). Muscle fiber type estimation revealed an increased proportion of type I fibers in flexor digitalis superficialis and gastrocnemius medialis in IUGR piglets (P < 0.05). These data clearly indicate that contractile function is accelerated in newborn IUGR piglets.     

The effect of six weeks endurance training on dynamic muscular control of the knee following fatiguing exercise

The aim of the study was to examine whether six weeks of endurance training minimizes the effects of fatigue on postural control during dynamic postural perturbations. Eighteen healthy volunteers were assigned to either a 6-week progressive endurance training program on a cycle ergometer or a control group. At week 0 and 7, dynamic exercise was performed on an ergometer until exhaustion and immediately after, the anterior–posterior centre of pressure (COP) sway was analyzed during full body perturbations. Maximal voluntary contractions (MVC) of the knee flexors and extensors, muscle fiber conduction velocity (MFCV) of the vastus lateralis and medialis during sustained isometric knee extension contractions, and power output were measured. Following the training protocol, maximum knee extensor and flexor force and power output increased significantly for the training group with no changes observed for the control group. Moreover, the reduction of MFCV due to fatigue changed for the training group only (from 8.6% to 3.4%). At baseline, the fatiguing exercise induced an increase in the centre of pressure sway during the perturbations in both groups (>10%). The fatiguing protocol also impaired postural control in the control group when measured at week 7. However, for the training group, sway was not altered after the fatiguing exercise when assessed at week 7. In summary, six weeks of endurance training delayed the onset of muscle fatigue and improved the ability to control balance in response to postural perturbations in the presence of muscle fatigue. Results implicate that endurance training should be included in any injury prevention program.     

Lentiviral-mediated transfer of CDNF promotes nerve regeneration and functional recovery after sciatic nerve injury in adult rats

Peripheral nerve injury is often followed by incomplete and unsatisfactory functional recovery and may be associated with sensory and motor impairment of the affected limb. Therefore, a novel method is needed to improve the speed of recovery and the final functional outcome after peripheral nerve injuries. This report investigates the effect of lentiviral-mediated transfer of conserved dopamine neurotrophic factor (CDNF) on regeneration of the rat peripheral nerve in a transection model in vivo. We observed notable overexpression of CDNF protein in the distal sciatic nerve after recombinant CDNF lentiviral vector application. We evaluated sciatic nerve regeneration after surgery using light and electron microscopy and the functional recovery using the sciatic functional index and target muscle weight. HE staining revealed better ordered structured in the CDNF-treated group at 8 weeks post-surgery. Quantitative analysis of immunohistochemistry of NF200 and S-100 in the CDNF group revealed significant improvement of axonal and Schwann cell regeneration compared with the control groups at 4 weeks and 8 weeks after injury. The thickness of the myelination around the axons in the CDNF group was significantly higher than in the control groups at 8 weeks post-surgery. The CDNF group displayed higher muscle weights and significantly increased sciatic nerve index values. Our findings suggest that CDNF gene therapy could provide durable and stable CDNF protein concentration and has the potential to enhance peripheral nerve regeneration, morphological and functional recovery following nerve injury, which suggests a promising strategy for peripheral nerve repair.     

The expression patterns of β1,4 galactosyltransferase I and V mRNAs, and Galβ1-4GlcNAc group in rat gastrocnemius muscles post sciatic nerve injury

Glycosylation is one of the most important post-translational modifications. It is clear that the single step of β1,4-galactosylation is performed by a family of β1,4-galactosyltransferases (β1,4-GalTs), and that each member of this family may play a distinct role in different tissues and cells. β1,4-GalT I and V are involved in the biosynthesis of N-linked oligosaccharides and play roles in sciatic nerve regeneration after sciatic nerve injury. In the present study, the expression of β1,4-galactosyltransferase (β1,4-GalT) I, V mRNAs and Galβ1-4GlcNAc group were examined in rat gastrocnemius muscles after sciatic nerve crush and transection. Real time PCR revealed that β1,4-GalT I and V mRNAs expressed at a high level in normal gastrocnemius muscles and decreased gradually from 6 h, reached the lowest level at 2 weeks, then restored gradually to relatively normal level at 4 weeks after sciatic nerve crush. In contrast, in sciatic nerve transection model, β1,4-GalT I and V mRNAs decreased gradually from 6 h, and remained on a low level at 4 weeks in gastrocnemius muscles after sciatic nerve transection. In situ hybridization indicated that β1,4-GalT I and V mRNAs localized in numerous myocytes and muscle satellite cells under normal conditions and at 4 weeks after sciatic nerve crush, and in a few muscle satellite cells at 4 weeks after sciatic nerve transection. Furthermore, lectin blotting showed that the expression level of the Galβ1–4GlcNAc group decreased from 6 h, reached the lowest level at 2 weeks, and restored to relatively normal level at 4 weeks after sciatic nerve crush. RCA-I lectin histochemistry demonstrated that Galβ1–4GlcNAc group localized in numerous membranes of myocytes and muscle satellite cells in normal and at 4 weeks after sciatic nerve crush, and in a few muscle satellite cells at 2 and 4 weeks after sciatic nerve transection. These results indicated that the expressions of β1,4-GalT I, V mRNAs and Galβ1–4GlcNAc group were involved in the process of denervation and reinnervation, which suggests that β1,4-GalT I, V mRNAs and Galβ1-4GlcNAc group may play an important role in the muscle regeneration.     

Effects of fatigue duration and muscle type on voluntary and evoked contractile properties

Behm, D. G., and D. M. M. St-Pierre. Effects of fatigueduration and muscle type on voluntary and evoked contractile properties. J. Appl. Physiol. 82(5):1654-1661, 1997.The effects of fatigue duration and muscle typeon voluntary and evoked contractile properties were investigated withan isometric, intermittent, submaximal fatigue protocol. Four groupsperformed contractions of the plantar flexors and quadriceps at variousintensities to produce long (LDF; 19 min 30 s)- and short-durationfatigue (SDF; 4 min 17 s). The LDF group had a significantly greaterdecrease in muscle activation than did the SDF group (12 vs. 5.8%)during recovery, although there was no difference in the impairment of maximum voluntary contraction force beyond 30 s of recovery. The significant decrease in the compound muscle action potential of the LDFgroup (M-wave amplitude; 14.7%) contrasted with the M-wave potentiation of the SDF group (15.7%), suggesting changes in membrane excitation may affect LDF. The quadriceps group performing contractions at 50% MVC experienced a smaller decrease in agonist electromyograph activity than did other groups, indicating both muscle and fatigue duration specificity. Impairments in excitation-contraction coupling were indicated by changes in quadriceps peak twitch and time to peaktwitch while decreases in PF M-wave amplitudes suggested a disruptionof membrane potentials. Results suggest that fatigue mechanisms may beduration (activation, half relaxation time) or muscle specific(electromyograph, twitch torque) or a combination of both (M wave, timeto peak twitch torque).

     

Effects of Acrylamide on the Nervous Tissue Antioxidant System and Sciatic Nerve Electrophysiology in the Rat

To investigate the time-dependent effects of acrylamide (ACR) on the antioxidative status in rat nerve tissues, adult male Wistar rats were given ACR (40 mg/kg, i.p., 3 times/week) for 2, 4, 6 and 10 weeks, respectively. The time-dependent changes of the lipid peroxidation (malondialdehyde, MDA) and antioxidative status (glutathione, GSH; glutathione peroxidase, GSH-Px; glutathione reductase, GR; superoxide dismutase, SOD and anti-reactive oxygen species, anti-ROS) in nerve tissues were investigated. The electrophysiology indices (nerve conduction velocity, NCV; compound action potential duration, CAPD; compound action potential amplitude, CAPA; compound action potential latency, CAPL) in the sciatic nerve were determined using BL-420E Biologic Function Determining System. The results showed that MDA levels increased significantly (P < 0.05) in nerve tissues, while GSH levels markedly decreased (P < 0.05) in a time-dependent manner. SOD activity (in the spinal cord and sciatic nerve) and GR activity (in the sciatic nerve) increased significantly after 4 weeks ACR treatment (P < 0.01), but then decreased (P < 0.05). The anti-ROS activity in the sciatic nerve was markedly decreased at the end of week 6 and 10 (P < 0.01). The above indices changed most in the sciatic nerve. The levels of GSH, MDA and anti-ROS in rat sciatic nerve were in high correlation (P < 0.05, |r| > 0.80) with the electrophysiology indices according to the exposure time. Thus, ACR-induced neurotoxicity may be associated with the enhancement of lipid peroxidation and reduction of the antioxidative capacity. Depletion of neural GSH level might be one of the primary events in ACR-induced neuropathy. Ying-Jian Zhu and Tao Zeng––These authors contributed equally to this work.     

Local muscle blood flow and sustained contractions of human arm and back muscles.

The endurance during sustained contraction of elbow, flexors, elbow extensors, and back extensors was tested in 3 human subjects. The force level used was varied between ca. 15 and ca. 75% of maximal isometric strength (IS). The clearance of 133Xe from contracting muscles was registered during and after the endurance test. In this way it was possible to determine whether muscle blood flow (MBF) was increased or had stopped during the contraction. Experiments with artificial ischaemia of the upper arm together with MBF measurements showed that MBF was of no importance for continuing sustained contractions above a certain force level, which was 50,25, and 40% of IS for elbow flexors, elbow extensors and back extensors, respectively. However, the level, where longer lasting ( greater than 15 min) sustained contraction is possible is directly related to MBF. These levels were 22, 15, and 20% IS for elbow flexors, elbow extensors, and back extensors, respectively.     

Effect of weight bearing on recovery from nerve injury in skeletal muscle.

We examined the effect of weight bearing (WB) on muscle recovery after nerve injury. Rats were housed in individual cages for 2 wk under WB or hindlimb suspension (HS) after being subjected to sciatic nerve compression for 1 wk. Sham operated on rats served as controls (sham group). We used 31P- and 19F-nuclear magnetic resonance spectroscopy combined with histochemical, physiological, and biochemical techniques to assess the outcome in the three groups. Creatine kinase-BB (CK-BB) mRNA levels expression, CK activity, and type I fiber density in the WB group were elevated compared with those in the HS group. In addition, sciatic functional index, tetanic tension, energy state, and local circulation dynamics of the WB group were greater than those of the HS group. These results suggested that WB plays an important role in muscle regeneration, inhibits the reduction of CK activity, and facilitates the activation of neural recovery, energy state, and local circulation dynamics.     

Power output and work in different muscle groups during ergometer cycling

The aim of this study was to calculate the magnitude of the instantaneous muscular power output at the hip, knee and ankle joints during ergometer cycling. Six healthy subjects pedalled a weight-braked bicycle ergometer at 120 watts (W) and 60 revolutions per minute (rpm). The subjects were filmed with a cine camera, and pedal reaction forces were recorded from a force transducer mounted in the pedal. The muscular work at the hip, knee and ankle joint was calculated using a model based upon dynamic mechanics described elsewhere. The mean peak concentric power output was, for the hip extensors, 74.4 W, hip flexors, 18.0 W, knee extensors, 110.1 W, knee flexors, 30.0 W and ankle plantar flexors, 59.4 W. At the ankle joint, energy absorption through eccentric plantar flexor action was observed, with a mean peak power of 11.4 W and negative work of 3.4 J for each limb and complete pedal revolution. The energy production relationships between the different major muscle groups were computed and the contributions to the total positive work were: hip extensors, 27%; hip flexors, 4%; knee extensors, 39%; knee flexors, 10%; and ankle plantar flexors 20%.     

Distribution of muscle fibers in skeletal muscles of the cheetah (Acinonyx jubatus)

We examine the muscle fiber population of skeletal muscles from whole body in the cheetah (Acinonyx jubatus). In the present experiments, we showed the characteristics of fiber composition in the cheetah by comparative studies among the cheetah, domestic cat, and the beagle dog. Fiber population was determined on muscle fibers stained with monoclonal antibody to each myosin heavy chain isoform. Histochemical analysis demonstrated that many muscles in the cheetah and domestic cat had a low percentage of Type I fibers and a high percentage of Type IIx fibers, while those in the beagle dog showed a high percentage of Type IIa. The hindlimb muscles in the cheetah had a higher percentage of Type II (Type IIa + IIx) fiber than the forelimb muscles. This fact suggests that the propulsive role of the hindlimb is greater than the forelimb in the cheetah. The longissimus in the cheetah had a high percentage of Type IIx fibers over a wide range from the thoracic to lumbar parts, while the population of muscle fibers in this muscle was different depending on the parts in the domestic cat and beagle dog. This indicates that the cheetah can produce a strong and quick extension of the spinal column and increase its stiffness during locomotion. Furthermore, we found the notable difference of muscle fiber type population between flexors and extensors of digits in the cheetah. The present experiments show the characteristics of muscle fibers in the cheetah, corresponded to its ability to perform high-speed running.     

Isometric force development of some muscle groups in athletes

In a large sample of both male and female athletes, subdivided by age and sex, a development curve of isometric muscule force (F) was analyzed for hand flexors, upper-body flexors and extensors, and knee extensors (PDS). A sample of 1,857 male and 1,009 female athletes, aged 8-30 years, subdivided by their age and sex, was used to measure the mean values of isometric muscle force of certain muscle groups by way of 5 topologically defined tests. Based on the results, isometric muscle force (F) development curves are shown and analyzed for the right-hand and left-hand (PLS) flexors, upper-body flexors (PTR), upper-body extensors (OTR), and knee extensors (ONO). The application of certain statistical programs gave rise to equations of the relationship between isometric force and age. The maximum mean value of PLS was chosen as the reference value or "the gold standard," with which PTR, OTR, and ONO were subsequently compared. The relationships were 1:1:1:2.8:5.9 (for male athletes), and 1:1:1.3:3.2:5.2 (for female athletes). The newly derived relationship was recognized as "the canon." The results may have practical application in athletes' fitness and conditioning. Every topologically defined muscle force has its own patterns and rules that should be closely followed in the training process, because any generalization may lead to false conclusions.     

The role of hind limb flexor muscles during swimming in the toad, Bufo marinus

Most work examining muscle function during anuran locomotion has focused largely on the roles of major hind limb extensors during jumping and swimming. Nevertheless, the recovery phase of anuran locomotion likely plays a critical role in locomotor performance, especially in the aquatic environment, where flexing limbs can increase drag on the swimming animal. In this study, I use kinematic and electromyographic analyses to explore the roles of four anatomical flexor muscles in the hind limb of Bufo marinus during swimming: m. iliacus externus, a hip flexor; mm. iliofibularis and semitendinosus, knee flexors; and m. tibialis anticus longus, an ankle flexor. Two general questions are addressed: (1) What role, if any, do these flexors play during limb extension? and (2) How do limb flexors control limb flexion? Musculus iliacus externus exhibits a large burst of EMG activity early in limb extension and shows low levels of activity during recovery. Both m. iliofibularis and m. semitendinosus are biphasically active, with relatively short but intense bursts during limb extension followed by longer and typically weaker secondary bursts during recovery. Musculus tibialis anticus longus becomes active mid way through recovery and remains active through the start of extension in the next stroke. In conclusion, flexors at all three joints exhibit some activity during limb extension, indicating that they play a role in mediating limb movements during propulsion. Further, recovery is controlled by a complex pattern of flexor activation timing, but muscle intensities are generally lower, suggesting relatively low force requirements during this phase of swimming.     

Non-thermal plasma application enhances the recovery of transected sciatic nerves in rats

This experimental research aimed to investigate the effects of non-thermal plasma on nerve regeneration after transected nerve damage using the sciatic nerve in Wistar albino (A) rats. The experiments were performed on 27 Wistar A rats. The rats underwent surgery for right sciatic nerve exposure and were divided into three groups (each group, n = 9) according to sciatic nerve transected injury (SNTI) and non-thermal plasma application: a non-nerve damage (non-ND) group, a only nerve damage without non-thermal plasma application (ND) group, and a nerve damage with non-thermal plasma application (ND + NTP) group. Subsequent to SNTI and immediate suture, non-thermal plasma was administered three times per week for eight weeks. Evaluation for functional recovery was performed using the static sciatic index measured over the full treatment period of eight weeks. The sciatic nerve specimens were obtained after euthanasia and third day from the last non-thermal plasma application. The sciatic nerve tissues were subjected to histological analysis. Behavior analysis presented that the ND + NTP group showed improved static sciatic index compared with the nerve damage group. Histopathological findings demonstrated that the ND + NTP group had more dense Schwann cells and well-established continuity of nerve fibers, greater than the nerve damage group. Immunohistochemistry showed that the ND + NTP group had increased levels of markers for microtubule-associated protein 2 (MAP2), tau, S100 calcium-binding protein B, and neurofilament-200 and regulated the overexpression of CD68 and MAP2. These results indicated that non-thermal plasma enhanced the motor function and restored the neuronal structure by accelerating myelination and axonal regeneration. Additionally, non-thermal plasma was confirmed to have a positive effect on the recovery of SNTI in rats.     

A novel basic fibroblast growth factor delivery system fabricated with heparin-incorporated fibrin–fibronectin matrices for repairing rat sciatic nerve disruptions

Autologous nerve grafts are widely used in bridging critical gaps of peripheral nerves, but they remain associated with high morbidity of the donor site and lack of full recovery. As an alternative, we have focused on chitosan nerve conduits filled with a heparin-incorporated fibrin–fibronectin matrix serving as delivery systems for basic fibroblast growth factor (bFGF). The artificial nerve conduits were used for repairing sciatic nerve defects of 10 mm in adult rats. Three months post-operation, the conduction velocity recovery index (CVRI) and the muscle restoration rate (MRR) in animals of the experimental group were 32 ± 4.1 and 77.4 ± 7.9%, respectively, which were significantly higher than those of the PBS control group (17.8 ± 1.9 and 66.7 ± 6.5%), and similar to those of the autograft group (38.4 ± 3.9 and 81.3 ± 7.8%). These results were also consistent with the densities of regenerated axons in the three groups, which were demonstrated by histomorphological analysis.     

Improving Nerve Regeneration of Acellular Nerve Allografts Seeded with SCs Bridging the Sciatic Nerve Defects of Rat

The objective of the paper is to evaluate the effect of acellular nerve allografts (ANA) seeded with Schwann cells to promote nerve regeneration after bridging the sciatic nerve defects of rats and to discuss its acting mechanisms. Schwann cells were isolated from neonatal Wistar rats. In vitro Schwann cells were microinjected into acellular nerve allografts and co-cultured. Twenty-four Wistar rats weighing 180–220 g were randomly divided into three groups with eight rats in each group: ANA seeded with Schwann cells (ANA + SCs), ANA group and autografts group. All the grafts were, respectively, served for bridging a 10-mm long surgically created sciatic nerve gap. Examinations of regeneration nerve were performed after 12 weeks by transmission electron microscope (TEM), scanning electron microscope (SEM), and electrophysiological methods, and then analyzed statistically. The results obtained indicated that in vitro Schwann cells displayed the feature of bipolar morphology with oval nuclei. Compared with ANA group, the conduction velocity of ANA + SCs group and autograft group was faster after 12 weeks, latent period was shorter, and wave amplitude was higher (P < 0.05). The difference between ANA + SCs group and autograft group is not significant (P > 0.05). Regeneration nerve myelinated fiber number, myelin sheath thickness, and myelinated fibers/total nerves (%) in both ANA + SCs group and autograft group are higher than that in ANA group; the difference is significant (P < 0.05). The difference between the former two is not significant (P > 0.05). In conclusion, ANA seeded with SCs could improve nerve regeneration and functional recovery after bridging the sciatic nerve gap of rats, which offers a novel approach for the repair peripheral nerve defect.     

Nerve stimulation with a multi-contact cuff electrode: validation of model predictions

The recruitment characteristics of muscle selective nerve stimulation by a multi-contact nerve cuff electrode, as predicted by computer modeling, have been investigated in acute experiments on rabbits. A nerve cuff containing five or six dot electrodes was placed around the sciatic nerve in five rabbits. M-waves were recorded with wire electrodes from the lateral gastrocnemius, soleus, tibialis anterior, and extensor digitorum longus muscles. The muscle recruitment performances of three contact configurations (monopole, transverse bipole, transverse tripole) were compared. The selectivity was quantified by the recruitment of two muscles (one extensor and one flexor) in response to a particular stimulus. The results showed that only in a few cases, transverse bi- and tripolar stimulation provided a better selectivity than monopolar stimulation. Neither of the two extensors, nor of the two flexors could be stimulated separately. In accordance with the results of the modeling studies, bi- and tripolar stimulation required higher stimulus currents than monopolar stimulation, whereas maximum recruitment and slopes of recruitment curves were lower. The rabbit sciatic nerve appears to be a less suitable preparation for reproducible selectivity experiments, due to the variability in the number and size of the fascicles and their position in this nerve.