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M F Meek

Publications and source records attributed to M F Meek.

At least 37 records · Page 2Linked to original sources
PubMed2001

Functional assessment of peripheral nerve recovery in the rat: gait kinematics.

Computerized rat gait analysis has become an invaluable technique of functional evaluation for some peripheral nerve investigators, comparing the normal and the pathological kinematic data. Appropriate selection of the methods to evaluate the functional outcome should be sensitive enough to moderate changes. By combining kinematic data and traditional methods in regeneration studies, it is possible to achieve better documentation of functional changes with the passage of time. A review of the three commonly kinematic parameters used in nerve regeneration studies, such as the calculation of sciatic function index, stance factor, and ankle angle, will provide the reader with detailed information about this accurate and consistent means of evaluating peripheral nerve function after nerve injury and repair. This study aims to review the different methods and potentialities of the rat gait kinematics as a noninvasive evaluation during regeneration, allowing for measurement of the rate of functional recovery in experimental studies.

Animals↗
PubMed2001

Biodegradable p(DLLA-epsilon-CL) nerve guides versus autologous nerve grafts: electromyographic and video analysis.

The aim of this study was to evaluate the functional effects of bridging a gap in the sciatic nerve of the rat with either a biodegradable copolymer of DL-lactide and epsilon-caprolactone [p(DLLA-epsilon-CL)] nerve guide or an autologous nerve graft. Electromyograms (EMGs) of the gastrocnemius (GC) and tibialis anterior (TA) muscles were recorded 3.5 and 5 months after bridging the nerve gaps. Furthermore, the rats' gait was recorded on video and the quality of the gait was analyzed. EMG patterns of the contralateral nonoperated side were essentially normal. The EMG patterns on the operated side were irregular in all animals, but the quality of gait was better in the nerve guide group. We conclude that the surgical technique (nerve guide or nerve graft) does not influence the occurrence of abnormal EMG patterns, but gait improves to a greater extent when the nerve gap is bridged by a nerve guide.

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PubMed2001

Sensory nerve function and auto-mutilation after reconstruction of various gap lengths with nerve guides and autologous nerve grafts.

The aim of this study was to evaluate sensory nerve recovery and auto-mutilation after reconstruction of various lengths of nerve gaps in the sciatic nerve of the rat, using different techniques. Group 4, in which the longest nerve gap (15 mm) was reconstructed with a thin-walled p(DL-lactide-gamma-caprolactone) nerve guide filled with modified denatured muscle tissue, showed the best results in the electro-stimulation tests and signs of severe auto-mutilation were not observed. Even in the control group, in which a 10 mm nerve gap was left open, in two of the five rats improvement of the sensory nerve function was observed, which was caused by re-innervation of the sciatic nerve and not by expansion of the neighboring saphenous nerve. It is hypothesized that a better quality of nerve reconstruction/guidance channel/support results in faster regeneration and hence re-innervation, thereby, preventing auto-mutilation. A thin red glabrous skin, anhydrosis (dryness of the skin), short nails and edema were interpreted as signs of autonomic dysfunction.

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PubMed2001

Electronmicroscopical evaluation of short-term nerve regeneration through a thin-walled biodegradable poly(DLLA-epsilon-CL) nerve guide filled with modified denatured muscle tissue.

The aim of this study was to evaluate short-term peripheral nerve regeneration across a 15-mm gap in the sciatic nerve of the rat, using a thin-walled biodegradable poly(DL-lactide-epsilon-caprolactone) nerve guide filled with modified denatured muscle tissue (MDMT). The evaluation was performed using transmission electron microscopy and morphometric analysis. Evaluation times ranged from 3 to 12 weeks after reconstruction. Already, 3 weeks after reconstruction, myelinated nerve fibers could be observed in the distal nerve stump. Twelve weeks after reconstruction, the number of (non)myelinated nerve fibers had significantly increased in the distal nerve stump. From this study, we can conclude that a thin-walled biodegradable poly(DL-lactide-epsilon-caprolactone) nerve guides filled with MDMT can be successfully applied in the reconstruction of severed nerves in the rat model. Furthermore, we showed fast nerve regeneration across the 15-mm nerve gap and found that the use of MDMT functioned as a mechanical support preventing a collapse of this thin-walled nerve guide.

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PubMed2001

Muscle differentiation after sciatic nerve transection and reinnervation in adult rats.

Reinnervation after peripheral nerve transections generally leads to poor functional recovery. In order to study whether changes in muscles might be a contributing factor in this phenomenon we studied muscle morphology and fibre type distributions after sciatic nerve transection in the rat hind limb. Proximally, before the bifurcation in the tibial and common peroneal nerve, a 12 mm segment of the sciatic nerve was resected, reversed and re-implanted as an autologous nerve graft. After survival periods of 7, 15 and 21 weeks the lateral gastrocnemius, tibialis anterior and soleus muscles were dissected, stained with mATP-ase, and fibre type distributions were studied. In addition, numbers of muscle fibres were counted, and cross sectional areas were calculated. After 7 weeks, cross sectional areas were decreased in all muscles. In the gastrocnemius and tibialis anterior muscles the fibre number remained unaltered but the hypotrophy had been reversed at later ages. The number of muscle fibres in the soleus muscle remained decreased over the entire period of observation. The percentages of type II fibres in the gastrocnemius and tibialis anterior muscles were decreased at 7 and 15 weeks but these again approached normal values at 21 weeks. The type I fibres, however, remained arranged in groups. In the soleus muscle a large increase in the percentage of type II muscle fibres was observed and this remained until 21 weeks. We conclude that a non-selective reinnervation and later readjustments by regression of polyneural innervation may in part explain the changes in distributions of various fibre types.

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PubMed2001

Sciatic nerve transection in adult and young rats: abnormal EMG patterns during locomotion.

Transections of peripheral nerves usually lead to serious handicaps. In order to enhance insights into the poor functional recovery, we studied the effects of a unilateral sciatic nerve lesion in adult and young rats. Electromyographic (EMG) patterns of the tibialis anterior (a hindlimb flexor) and the gastrocnemius muscle (a hindlimb extensor) during walking were recorded after transecting the sciatic nerve at adult age and at the 10th postnatal day. After recovery periods lasting up to 21 weeks, EMG patterns in the hindleg muscles during locomotion were highly abnormal, irrespective of the age at lesioning. Electromyographic bursts were markedly irregular and, generally, coactivation of these antagonists was observed during walking. Other evidence has shown that after peripheral nerve transection, nerves randomly reinnervate their target muscles and we conclude that the patterns of muscle activity may be associated with the properties of foreign, as well as genuine, motor nerves. Behaviourally, walking patterns after a transection at adult age are markedly abnormal but, after transection at the 10th day, locomotion is much less disturbed. The finding of a discrepancy between a near normal walking pattern in rats operated on at a young age and severely disturbed EMG activity may be due to subtle readjustments in the force recruitment in the respective muscles, despite a random reinnervation by the sciatic nerve branches. These compensatory readjustments are particularly prominent after transection at an early age.

Age Factors↗
PubMed2001

Transection of the sciatic nerve and reinnervation in adult rats: muscle and endplate morphology.

The functional recovery after peripheral nerve lesions is generally poor. We studied whether changes in muscles after reinnervation might explain such disappointing results. The functional recovery after peripheral nerve lesions is generally poor. Changes in muscle morphology and neuromuscular innervation might partly explain this lack of compensation. In order to test this hypothesis, we studied muscular differentiation in the soleus, gastrocnemius and tibialis anterior muscles at 7, 15 and 21 weeks after a sciatic nerve lesion in adult rats. In the gastrocnemius and tibialis muscles the percentages of type II muscles fibres were decreased at 7 and 15 weeks but at 21 weeks they again approached normal values. The soleus muscle, however, was permanently decreased in size and this muscle, in contrast to the normal soleus muscle, contained mainly type II fibres. The morphology of the endplates showed distinct stages of degeneration and reinnervation. Two weeks after denervation, in rats in which reinnervation was prevented, all 3 muscles contained considerable numbers of morphologically abnormal endplates and, after 7 weeks, no endplates were detected. During reinnervation, endplates showing signs of acetylcholinesterase activity were observed in all 3 muscles from 7 weeks. At later ages a shift towards morphologically normal endplates occurred, but complete recovery was not observed. Endplates in all 3 muscles were polyneurally innervated at 7 weeks. Although these percentages decreased over age, polyneural innervation was still present at 21 weeks. We conclude that the changes in the distribution of fibre types, abnormal endplate morphology and polyneural innervation may in part explain the poor functional recovery after peripheral nerve lesions.

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PubMed2001

La maladie de Grisel: spontaneous atlantoaxial subluxation.

OBJECTIVE: "La maladie de Grisel" (Grisel's syndrome) is a spontaneously occurring atlantoaxial subluxation with torticollis. We present a case of atlantoaxial subluxation occurring in a 20-year period of pharyngoplasty surgery. The occurrence of a "spontaneous" atlantoaxial subluxation after oral cavity or pharynx operations is rare. Because some neck pain and stiffness are commonly seen after these kinds of operations, we would like to draw attention to this unusual complication. Symptoms associated with a torticollis after an operation in the oral cavity or pharynx requires additional investigation to exclude this rare complication. A review of the available literature concerning etiology and treatment of la maladie de Grisel is presented.

Atlanto-Axial Joint↗
PubMed2000

In vivo and in vitro degradation of poly[(50)/(50) ((85)/(15)(L)/(D))LA/epsilon-CL], and the implications for the use in nerve reconstruction.

Nerve guides can be used for the reconstruction of peripheral nerve defects. After serving their function, nerve guides should degrade. p[(50)/(50) ((85)/(15)(L)/(D))LA/epsilon-CL] degrades completely within 1 year without the formation of a slow degrading crystalline fraction. Although the tensile strength (TS) of a p[(50)/(50) ((85)/(15)(L)/(D))LA/epsilon-CL] nerve guide is negligible after 2 months, nerve regeneration across a 1-cm gap in the sciatic nerve of the rat is faster and qualitatively better than after reconstruction using autologous nerve grafts. During degradation p[(50)/(50) ((85)/(15)(L)/(D))LA/epsilon-CL] swells, especially during the first 3 months. This can have a negative influence on the regenerating nerve. p[(50)/(50) ((85)/(15)(L)/(D))LA/epsilon-CL] nerve guides could only be used in the clinical situation in case of short nerve gaps (several mm) in small nerves (for instance digital nerves). Refinements will be needed to successfully reconstruct longer nerve gaps (several cm).

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PubMed2000

Methods to evaluate functional nerve recovery in adult rats: walking track analysis, video analysis and the withdrawal reflex.

The aim of this study was to compare different methods for the evaluation of functional nerve recovery. Three groups of adult male Wistar rats were studied. In group A, a 12-mm gap between nerve ends was bridged by an autologous nerve graft; in rats of group B we performed a crush lesion of the sciatic nerve and group C consisted of non-operated control rats. The withdrawal reflex, elicited by an electric stimulus, was used to evaluate the recovery of sensory nerve function. To investigate motor nerve recovery we analyzed the walking pattern. Three different methods were used to obtain data for footprint analysis: photographic paper with thickened film developer on the paws, normal white paper with finger paint, and video recordings. The footprints were used to calculate the sciatic function index (SFI). From the video recordings, we also analyzed stepcycles. The withdrawal reflex is a convenient and reproducible test for the evaluation of global sensory nerve recovery. Recording walking movements on video and the analysis of footplacing is a perfect although time-consuming method for the evaluation of functional aspects of motor nerve recovery.

Animals↗
PubMed2000

Sciatic nerve transection in the adult rat: abnormal EMG patterns during locomotion by aberrant innervation of hindleg muscles.

The effects of lesions in the sciatic nerve were studied in adult rats. In the left hindleg, a segment 12 mm long was resected from the proximal part of the nerve, before the bifurcation into the peroneal and tibial nerves. This segment in a reversed orientation was used as a nerve graft. EMG patterns in the tibialis anterior and the gastrocnemius muscles at both sides were recorded during locomotion in six rats after recovery periods varying from 15 to 21 weeks. The specificity of axonal outgrowth was studied in nine rats by retrogradely labeling the motoneurons with unconjugated Cholera Toxin subunit B (CTB) after injections into the gastrocnemius, the soleus, and the tibialis anterior muscles at both sides. EMG patterns at the operated side were irregular and we often observed coactivation of the gastrocnemius and tibialis anterior muscle. Moreover, burst activity was badly adjusted to the phases of the stepcycle. Retrogradely labeling indicated that the pools of motoneurons innervating the respective muscles at the left side had increased in volume. Neuronal diameters were slightly decreased but a considerable decrease was observed in dendritic branching and dendrite bundles in the pools of the SOL and in the GC were absent. No consistent trends in neuronal numbers at the affected side in comparison to the right side were detected. We conclude that axons, sprouting from the proximal stump of the sciatic nerve, innervate the muscles aselectively and that the motoneurons of origin maintain their original activation pattern.

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