University of Groningen
Muscular reinnervation and differentiation after peripheral nerve transection
IJkema-Paasen, Josina
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3
REINNERVATION OF MUSCLES
AFTER TRANSECTION OF THE
SCIATIC NERVE IN ADULT RATS
Chapter 3
33
ABSTRACT
Functional recovery after transection of the sciatic nerve
in adult rats is poor, probably because of abnormalities
in reinnervation. Denervation and reinnervation patterns
were studied morphologically in the lateral gastrocnemius
(LGC), tibialis anterior (TA), and soleus (SOL) muscles
for 21 weeks after nerve transection (motor endplates by
acetylcholinesterase staining; nerves by silver impregnation). Motor endplates in the TA showed improving morphology with age, and, at 21 weeks, three-quarters of
these were normal. Poorest recovery was observed in the
SOL, as, at 21 weeks, only one-third of the motor endplates had a normal morphology. Polyneuronal innervation initially was more pronounced in the SOL, but, at 21
weeks, 10% of the motor endplates in all three muscles
were still polyneuronally innervated. Our results indicate
important differences in the reinnervation of these three
hindleg muscles, and, even at 5 months, abnormalities
were still present. These factors may in part explain the
abnormal locomotion in rats as well as the limited recovery of function observed clinically in humans after nerve
34
Chapter 3
transection.
INTRODUCTION
Functional recovery after transection of a peripheral nerve, e.g., due to
trauma, generally is poor, despite meticulous reconstructive microsurgery or the
use of modern artificial nerve guides
18;26;27
. Our previous results on sciatic nerve
transection in adult rats, with repair using an autologous nerve graft, are in accord
with this11;20. Recordings of footprints and calculations of the sciatic function index
(SFI) only showed minimal recovery over time. Similar results were obtained by
Chen et al.9. Other groups, however, have observe some improvement in these
indices after 13 weeks13 or 26 weeks33 respectively, and our own recent research
revealed slight recovery in qualitative aspects of gait (as regularity of the stepcycle, fluency of walking) with time21.
After transection of a peripheral nerve, the distal section of the motor nerve
degenerates within hours22, synapses degrade,19;32 and the properties of muscle
change15. After a delay of 24-36 h, however, the axons start to sprout from the
proximal stump23. The Schwann cells ensheathing the nerve play a role in guiding the sensory and motor axons to their targets ( skin areas and muscle tissue,
respectively)5;6. However, the outgrowing motor axons are unable to identify their
own muscles and randomly reinnervate muscles that were denervated by the
transection. The muscles thus become reinnervated in part by “foreign” and in
part by their original axons4;12 and this leads to abnormal activation patterns of
the muscles, such as cocontractions of flexors and extensors during locomotion
(for full discussion see Gramsbergen et al.,12).
Earlier results on cross-innervation experiments in adult cats by Buller et al.7
indicated that the properties of muscle fibers adjust to those of the motoneurons.
With this in mind, we recently studied the effects of proximal transection of the
sciatic nerve on fiber type distributions in two hindlimb extensors, the lateral gastrocnemius muscle (LGC), mainly containing type II muscle fibers, and the soleus
muscle (SOL) which contains more than 80% type I muscle fibers. We also studied
a hindlimb flexor, the tibialis anterior muscle (TA), which is constituted mainly by
type II muscle fibers15. Seven weeks after the transection, we detected similar
proportions of type I and type II fibers in all three muscles. When considering an
at-random innervation of the three muscles7 after the sciatic nerve transection,
Chapter 3
this finding is in agreement with the results obtained by Buller et al.7. However,
after longer postoperative intervals, the fiber type distributions in the LGC and TA
tended to approach normal values, but the SOL had reversed to a muscle with
mainly type II muscle fibers15. An explanation of these puzzling results is lacking.
As abnormalities in reinnervation might explain these striking results, we decided
to study the time course of the neuromuscular reinnervation in the LGC, TA, and
SOL muscles from 2 to 21 weeks after transection.
35
MATERIAL AND METHODS
A total of 11 male Wistar rats (200 g) was used for this study. Rats in one
group (N=6), were premedicated with atropine (0.25 mg/kg body weight) and
anesthetized with 1% halothane (Fluothane) and O2/N2O. The left sciatic nerve
was exposed by splitting the gluteal muscle. A 12-mm segment was resected
proximal to the bifurcation. This segment was reversed and used as an autologous
nerve graft. Reversing the nerve segment avoids sprouting of branches from the
nerve graft15. The proximal and distal coaptation sites were sutured epineurally
with 10-0 nylon and the wound was closed. After survival periods of 7, 15, or
21 weeks, material was collected from two rats each. The animals were deeply
anaesthetized with ether and the LGC, TA, and SOL muscles were dissected. In
order to study the effects of denervation alone on motor endplates, in a second
group of rats (N=3), we transected the sciatic nerve and ligated the proximal
stump of the nerve to prevent reinnervation of muscles in the lower leg. After 2,
4, and 7 weeks, the muscles at the operated side were removed and the rats were
sacrificed.
In previous studies, we demonstrated that adaptational changes occur in
movements and electromyographic patterns of the unoperated leg,12 and this
might be reflected in changes in the muscles of this leg. Therefore, we chose to
collect material from two control rats at an age similar to that of the rats we studied at 21 weeks after the initial operation.
The muscles were stretched mildly and frozen in isopentane, cooled by liquid
nitrogen, and kept at –80° C. Longitudinal cryostat sections (40µm) were cut on
a cryostat and air-dried at room temperature. For histological processing, we followed the procedure described by Beermann and Cassens1. Tissue was fixated in
30% formalin and incubated in acetyl-thiocholine-iodide solution, in order to stain
acetylcholinesterase (AChE) in the motor endplate. Nerve terminals were stained
by impregnating them in a 10% AgNO3 solution. This procedure resulted in nerve
fibers staining black, motor endplates staining brown, and muscle fibers staining
yellow.
The motor endplates were studied at high magnification (100x) and their
morphology was categorized. Shortly after transection, normal motor endplates
Chapter 3
can still be observed but, at later stages, we observed motor endplates consisting
of interconnected but shrunken AChE-positive structures or, in other cases, showing clear signs of degeneration and fragmentation. During regeneration, as well,
three mutually exclusive stages could be distinguished, i.e. motor endplates consisting of fragments of AChE positivity, motor endplates with interconnected AChE
structures having a granular appearance, and fully regenerated, normal motor
36
endplates. This categorization is derived from descriptions by Csillik and Sávay10,
as well as from our own studies14. Quantitative data on the frequency of each of
these motor endplate categories were collected. Sections with the motor endplate
regions were selected and the locations of the endplates marked on a map at low
magnification (76x, Nikon microscope with drawing device). Motor endplates in
representative regions were drawn at high magnification (2,100x) and allotted to
one of the above categories.
In addition, we studied trends in the numbers of nerve endings on motor
endplates. When considering these data, it should be kept in mind that only axons
in the plane of section can be considered, and these data therefore underestimate
the actual number of endings per motor endplate3;29. We also studied trends in the
sizes of motor endplates. As the motor endplates follow the cylindrical surface of
the muscle fibers, it is not possible to reliably measure their width and, therefore,
we restricted ourselves to measuring the length of the motor endplates.
Data on the frequencies of motor endplate morphology were subjected to statistical testing (Chi-square; significance level 5%). Trends in dimensions of motor
endplates were tested applying Welch’s approximate t-test, with a significance
level of 5%.
RESULTS
The motor endplates of the LGC, TA and SOL muscles in control rats were
arranged in a narrow plane, located in the mid-belly region of the muscle. In the
vicinity of the motor endplates, we generally observed nerve branches consisting of several axons ensheated by myelin. The motor endplates had an elliptical
shape, and the large, darkly stained AChE-positive blots were located mainly in
their periphery (Fig. 1A). Several of these blots were interconnected, thus forming a complex structure. In the TA and LGC, all motor endplates had this normal
morphology. In the SOL, however, we detected, in 7% of the motor endplates,
AChE-positive blots with a granular appearance, similar to motor endplates at
advanged stages of reinnervation.
Measurements of the motor endplates indicated that their average lengths
in the three muscles varied between about 35 and 40 µm, but the variations in
length were large indeed. We could not detect significant differences between the
sizes of motor endplates in the three muscles.
Chapter 3
Degradation of Motor Endplates. In the animal examined 2 weeks after sciatic
nerve transection, and in which reinnervation was prevented, we could not detect
any surviving nerve fibers in any of the muscles. However, we did observe bands
of mesenchymal cells near the groups of motor endplates, which may have been
the remains of the degenerated nerve branches. The morphology of the motor
endplates had clearly changed by this age. We observed motor endplates, which
37
were clearly decreased in size. The AChE blots were smaller and instead of having
Figure 1. Morphology and innervation patterns of motor endplates. Photographs were
taken on different levels in the 40µm slides, and reconstructions were made. Bar = 10
µm;
(A) Normal motor endplates; the darkly stained and interconnected AChE-positive spots are
located mainly at the periphery. (B) The intensely staining AChE-positive spots are lying
separately, with a fragmented appearance. (C) AChE-positive spots are interconnected but
have a granular appearance. (D) Polyneurally innervated motor endplate; arrows point at
nerve endings.
a smooth surface, they often were shrunken but were still interconnected. We
also observed another category of motor endplates in which the blots were clearly
further diminished in size and with the blots disconnected, signs of a further stage
of degeneration and fragmentation.
In the LGC, the majority of the motor endplates (62%) were shrunken, others
were fragmented, and only 5% had a normal appearance. In the TA, 24% of the
Chapter 3
motor endplates showed normal features, but the majority were fragmented. In
the SOL, we noticed that half of the motor endplates were still normal, whereas
the rest were either of the shrunken or fragmented type (Table 1). After 4 weeks,
we observed a few fragmented motor endplates but only in the TA, and at 7
weeks, motor endplates were not observed in any of the muscles.
The lengths of the motor endplates in the SOL and the LGC had diminished
38
significantly (P<0.05) after 2 weeks, but those in the TA remained within the
normal range until 4 weeks after the transection.
Table 1. Morphological characteristics of motor endplates, 2 weeks after denervation (without reinnervation) in the soleus muscle, lateral gastrocnemius muscle, and the tibialis anterior muscle.
Morphological
characteristics
Normal
Degenerating
and shrunken
Degenerating
and fragmented
Soleus
(%)
Lateral
gastrocnemius
(%)
Tibialis
anterior
(%)
46.0
32.0
5.4
62.1
24.0
24.0
24.0
32.5
52.0
Motor Endplates during Reinnervation. During reinnervation, initially small
and isolated grains of AChE-positive blots could be observed. At this stage, several
axons penetrated the motor endplate areas. The axons were near to normal, albeit
relatively thin. The AChE-positive blots were small and not interconnected. After
survival periods of 15 weeks or longer, the AChE blots in the motor endplates had
increased in size but their contours had an irregular and granular appearance. The
blots were interconnected and localized at the outer rim of the motor endplates.
At 7 weeks, we detected reinnervated motor endplates in all three muscles,
with the exception of one animal in which we could not detect any sign of reinnervation in the SOL muscle. The motor endplates, which were reinnervated at
this age, often had a fragmented appearance (Fig. 1B), whereas others were
in a more advanced stage of reconstruction and showed a granular appearance
(Fig. 1C ); we even observed motor endplates that had all the characteristics of
normal motor endplates (Fig. 1A). After 15 weeks of recovery, an increase in the
percentages of normal motor endplates was observed, and this percentage had
further increased at 21 weeks, but, even then, we still detected motor endplates
showing signs of reconstruction.
Quantification of the different stages of recovery indicated that in the TA,
7 weeks after transection, the percentages of the motor endplates with a fragmented appearance varied considerably. A granular aspect was observed in about
a third of the cases and, on the average, only a quarter of the motor endplates had
attained a normal morphology (Table 2). At 15 weeks, the percentages of normal
motor endplates had increased slightly (but not significantly) but, at 21 weeks, a
Chapter 3
large increase in the percentages of normal motor endplates was observed (the
differences between 15 and 21 weeks were significant; P < 0.05).
In the LGC at 7 weeks, the percentages of motor endplates in their initial
stage of reinnervation were still low. Between 7 and 15 weeks after the transection, an increase in the number of normal motor endplates was observed and, at
21 weeks, 48% – 58% of the motor endplates were normal. These values differed
39
significantly from the values in the TA at 21 weeks (P < 0.05).
Table 2. Morphological characteristics of motor endplates 7,15 and 21 weeks after transection and reinnervation of the sciatic nerve in the soleus muscle, the lateral gastrocnemius
muscle, and the tibialis anterior muscle.
Weeks after
transection
7
Morphological
characteristics
of endplates
Fragmented
Granular
Normal
Fragmented
Granular
Normal
Fragmented
Granular
Normal
15
21
Soleus
(%)
7.4
50
42.6
9.1
63.6
27.3
7.7
92.3
0
30
50
20
20.7
44.8
34.5
Lateral
gastrocnemius
(%)
26.7
33.3
40.0
30.8
34.6
34.6
29.0
22.6
48.4
22.2
50.0
27.8
2.0
17.3
80.8
5.6
36.1
58.3
Tibialis
anterior
(%)
79.0
21.0
0
55.5
25.0
19.4
0
34.1
65.9
7.1
40.5
52.4
1.4
39.4
59.1
2.5
7.5
90.9
Each value indicates values of a single muscle
In the SOL muscle, reinnervation at 7 weeks had hardly begun. In one rat,
no motor endplates could be observed at all and, in the other, only a few endplates were detected, which were predominantly (92%) of the granular type. At
15 weeks, the numbers of motor endplates of either type had increased considerably. Half of the motor endplates had a granular appearance and roughly one third
had attained normal characteristics. At 21 weeks, the percentages of the different
categories were similar to those at 15 weeks. Values at 15 and 21 weeks differed
significantly from those at 7 weeks (P < 0.05).
Comparing the three muscles at 21 weeks indicated that the highest proportions of normal motor endplates were found in the TA; the LGC took an intermediate position and, in the SOL, still only about one third of the motor endplates had
reached normal morphology.
Polyneural Innervation. In all reinnervated muscles, we invariably detected a
certain percentage of the motor endplates, innervated by more than one but no
more than two axons (Fig. 1D). Polyneuronal innervation was never observed in
control rats.
Quantitation of the data on polyneuronal innervation indicated that in both the
LGC and TA muscles around 15 – 20% of the motor endplates after 7 weeks were
Chapter 3
polyneuronally innervated (Table 3). At 15 weeks, this percentage had decreased
in both muscles. At 21 weeks, a further slight decrease in the percentage of
polyneuronal innervation was observed (Table 3). In the SOL muscle at 7 weeks,
we detected only a few motor endplates and 40% of these were innervated by
two axons. This percentage decreased in this muscle to 16%-32% at 15 weeks
and further to an average of 14% at 21 weeks. The decreases in each of the
40
muscles were statistically significant (P < 0.05), but the differences between the
three muscles at 21 weeks were not significant. Polyneuronal innervation was not
Table 3. Percentages of mono- and polyneuronally innervated motor endplates after different recovery periods in the soleus muscle, lateral gastrocnemius muscle, and tibialis anterior
muscle.
Soleus
Lateral
gastrocnemius
Tibialis
anterior
Weeks after Mononeural Polyneuronal Mononeural Polyneuronal Mononeural Polyneuronal
transection innervation innervation innervation innervation innervation innervation
(%)
(%)
(%)
(%)
(%)
(%)
7
15
21
60
84.6
68.2
72.2
100
40
15.4
31.8
27.8
0
70
90.9
88.2
89.7
94.1
86.4
30
9.1
11.8
10.3
5.9
13.6
84.6
84.2
83.3
92.2
87.5
95.8
15.4
15.8
16.7
8.0
12.5
4.2
restricted to motor endplates of the fragmented or granular type, and we regularly
observed even normal motor endplates that were polyneuronally innervated.
The dimensions of the motor endplates in the reinnervated muscles after 7
weeks all had decreased in comparison with control values (Table 4). In the SOL
and in the TA at 21 weeks, values had returned to normal values, but, in the LGC,
the dimensions remained somewhat smaller at all postoperative ages and these
differences were significant (P < 0.05).
Table 4. Lengths of the motor endplates in control muscles and after sciatic nerve transection, after different recovery periods.
Muscle
Control (µm)
7 weeks (µm)
15 weeks (µm)
21 weeks (µm)
Soleus
Lateral
gastrocnemius
Tibialis anterior
38.08 ± 14.17
17.43 ± 7.73
30.86 ± 11.19
38.54 ± 15.65
40.01 ± 11.59
34.91 ± 10.95
32.84 ± 9.58
32.59 ± 9.56
23.55 ± 6.7
36.04 ± 13.08
26.28 ± 8.38
36.91 ± 10.53
DISCUSSION
In the present investigation, we found that 2 weeks after sciatic nerve transection, most of the motor endplates in the LGC and TA had degraded. By 7 weeks,
several normal motor endplates were again present, and, at 21 weeks, most of
Chapter 3
the motor endplates were morphologically normal in these muscles. In the SOL,
however, even at 21 weeks, less than half of the motor endplates had a normal
morphology. These differences in the time scale of motor endplate maturation
are puzzling. The distance from the transection site to the SOL muscle is longer
than that to the TA or LGC, but it seems unlikely that this difference, amounting to a few millimeters at the most, could account for such a substantial delay
in motor endplate maturation. Recently, we studied the consequences of sciatic
41
nerve transection on the morphology of these three muscles and found that the
SOL changes from a muscle with over 80% of type I muscle fibers into one with
mainly type II muscle fibers15. The conversion of the SOL within 1 month from a
slow into a predominantly fast muscle might be related to the delayed maturation
of motor endplates.
An intriguing question is the fate of the motor endplates after denervation and
also whether their locations are the likely sites for reinnervation. Indications from
previous research indicate that the outgrowing axons indeed impinge upon the
former motor endplate locations2;4;17;30 and, in the present investigation, we only
observed endplates developing in the region where they normally are located.
The categories of motor endplates we defined, in order to identify stages of
degradation, are based upon the descriptions by Sávay and Csillik32 who studied
the consequences of denervating the gastrocnemius muscle. During reinnervation, similar categories were observed10 and these are similar to the stages we
distinguished during the development of motor endplates14. Four days after birth,
AChE-positive spots, distributed over the entire motor endplate, occur in the psoas
muscle of rats, and this stage closely resembles the stage when fragmented motor
endplates occur during reinnervation. With increasing age, these spots increase
in size, become connected and, from the 18th postnatal day, are located at the
periphery of the motor endplate. Because of this order in early development, we
hypothesize that motor endplates with isolated and fragmented AChE blots occur
in the initial stage of recovery, and motor endplates with a granular appearance
occur at an intermediate stage.
Muscle fibers in adult mammals normally are mononeuronally innervated8;29.
At older ages, and particularly in rats from 25 months onwards, the occurrence
of polyneuronally innervated muscle fibers increases31. In the muscles of control
rats aged about 1 year, only mononeuronally innervated motor endplates can be
observed, and this is in line with data in the literature16. In our operated rats,
however, polyneuronal innervation invariably occurred in all three muscles and
at all recovery periods. Seven weeks after the nerve lesion, about 20% (LGC and
TA) to 40% (SOL) of the motor endplates were polyneuronally innervated, and
these figures decreased to around 10% in all three muscles at 21 weeks. Similar
results were obtained by Pécot-Dechavasinne and Mira25 and Ribchester29 in the
gastrocnemius muscle after localized freezing of the sciatic nerve. Östberg et al.24
Chapter 3
demonstrated in cross-innervation experiments that over-innervation of a fast
muscle leads to a significant portion of the motor endplates becoming polyneuronally innervated. When, however, they connected the same two nerves to the
SOL muscle, they virtually found no polyneuronally innervated motor endplates.
In our study at 21 weeks after reinnervation, 10% of the motor endplates in all
three muscles were still polyneuronally innervated, perhaps as a consequence
42
of at-random reinnervation12, rather than over-innervation. Rich and Lichtman30
demonstrated that, during regeneration, axons from adjacent territories sprout
and share motor endplates with other axon terminals. Previously, we showed
that in the LGC and TA after a sciatic nerve transection, type I muscle fibers are
grouped together instead of being dispersed in a checkerboard-like pattern as is
found in normal muscles. Rafuse and Gordon28 suggested that fiber type grouping is explained by distally sprouting axons that induce groups of adjacent muscle
fibers with similar properties. The decrease in size of these so-called fiber type
groups15 parallels the decrease in polyneuronal innervation, and this suggests that
both processes are related.
Measurements of the motor endplates indicate that their lengths in the SOL
were significantly smaller at 7 weeks, but normal values were found at 21weeks.
At this time, two thirds of the motor endplates in the SOL were still morphologically abnormal.
This indicates that the stage of maturation of the motor endplate is not related to
the motor endplate size.
Results from the present study indicate that, at 21 weeks after sciatic nerve
transection, 10% of the motor endplates are still polyneuronally innervated and
that considerable percentages of the motor endplates have immature characteristics. These factors, together with data on at-random reinnervation of the
muscles12 and results on changes in the fiber type distribution15 may explain, to a
large extent, the abnormal locomotion in rats as well as limited recovery of function in clinical studies18;27.
We thank H.L. Bartels for assistance in performing the nerve transection and S.
Nekeman for technical assistance.
Chapter 3
43
REFERENCES
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
Chapter 3
20.
21.
44
22.
23.
Beermann DH, Cassens RG. A combined silver and acetylcholinesterase method for
staining intramuscular innervation. Stain Technol 1976; 51: 173-177.
Bennett MR, McLachlan EM, Taylor RS. The formation of synapses in reinnervated mammalian striated muscle. J Physiol (Lond) 1973; 233: 481-500.
Bodine-Fowler SC, Meyer RS, Moskovitz A, Abrams R, Botte MJ. Inaccurate projection
of rat soleus motoneurons: a comparison of nerve repair techniques. Muscle & Nerve
1997; 20: 29-37.
Brown MC, Ironton R. Sprouting and regression of neuromuscular synapses in partially
denervated mammalian muscles. J Physiol (Lond) 1978; 278: 325-348.
Brushart TME. Preferential reinnervation of motor nerves by regenerating motor axons.
J Neurosci 1988; 8: 1026-1031.
Brushart TME, Gerber J, Kessens P, Chen Y-G, Royall RM. Contributions of pathway and
neuron to preferential motor reinnervation. J Neurosci 1998; 18: 8674-8681.
Buller AJ, Eccles JC, Eccles RM. Interactions between motoneurones and muscles in
respect of the characteristic speeds of their responses. J Physiol (Lond) 1960; 150:
417-439.
Burke RE. Motor units: anatomy, physiology and functional organization. In:Handbook
of Physiology, section I,. Bethesda, MD American Physiological Soc: 1981. 345-439.
Chen LE, Seaber AV, Urbaniak JR, Murrell GAC. Denatured muscle as a nerve conduit: a
functional, morphologic and electrophysiologic evaluation. J Reconstr Microsurg 1994;
10: 137-144.
Csillik B, Sávay G. Die Regeneration der subneuronalen Apparate der motorischen Endplatten. Acta Neuroveg 1958; 19: 41-52.
Dijkstra JR, Meek MF, Robinson PH, Gramsbergen A. Methods to evaluate functional
nerve recovery in adult rats: walking track analysis, video analysis and the withdrawal
reflex. J Neurosci Methods 2000; 96: 89-96.
Gramsbergen A, IJkema-Paassen J, Meek MF. Sciatic nerve transection in the adult rat:
abnormal EMG patterns during locomotion by aberrant innervation of hindleg muscles.
Exp Neurol 2000; 161: 183-193.
Hall GD, van Way CW. A comparison of nerve grafting and tissue expansion techniques
in the rat. Microsurgery 1994; 15: 439-442.
IJkema-Paassen J, Gramsbergen A. Polyneural innervation in the psoas muscle of the
developing rat. Muscle Nerve 1998; 21: 1058-1063.
IJkema-Paassen J, Meek MF, Gramsbergen A. Muscle differentiation after sciatic nerve
transection and reinnervation in adult rats. Ann Anat 2001; 183: 369-377.
Jansen JKS, Fladby T. The perinatal reorganization of the innervation of skeletal muscle
in mammals. Progress Neurobiol 1990; 34: 39-90.
Lüllmann-Rauch R. The regeneration of neuromuscular junctions during spontaneous
reinnervation of the rat diaphragm. Z Zellforsch 1971; 121: 593-603.
Mackinnon SE, Dellon AL. Surgery of the peripheral nerve. New York, Thieme; 1988;
638.
Matsuda Y, Oki S, Kitaoka K, Nagano Y, Nojima M, Desaki J. Scanning electron microscopic study of denervated and reinnervated neuromuscular junction. Muscle Nerve
1988; 11: 1266-1271.
Meek MF, Dijkstra JR, Den Dunnen WFA, IJkema-Paassen J, Schakenraad JM, Gramsbergen A, Robinson PH. Functional assessment of sciatic nerve reconstruction: biodegradable poly (DLLA-ε-CL) nerve guides versus autologous nerve grafts. Microsurgery
1999; 19: 381-388.
Meek MF, Van Der Werff JFA, Nicolai J-PA, Gramsbergen A. Biodegradable p(DLLA-ε-CL)
nerve guides vs. autologous nerve grafts: EMG and video analysis. Muscle Nerve 2001;
24: 753-759.
Miledi R, Slater CR. Electrophysiology and electron-microscopy of rat neuromuscular
junctions after nerve degeneration. Proc R Soc Lond (Biol) 1968; 169: 289-306.
Miledi R, Slater CR. On the degeneration of rat neuromuscular junctions after nerve
section. J Physiol (Lond) 1970; 207: 507-528.
24. Östberg AJC, Vrbova G, O’Brien RAD. Reinnervation of fast and slow mammalian muscles by a superfluous number of motor axons. Neuroscience 1986; 18: 205-213.
25. Pécot-Dechavassine M, Mira J-C. Electrophysiological evaluation of the effects of naftidrofuryl on skeletal muscle reinnervation in the rat. Microsurg 1994; 15: 116-122.
26. Politis MJ. Specificity in mammalian peripheral nerve regeneration at the level of the
nerve trunk. Brain Res 1985; 328: 271-276.
27. Pollock M, Harris AJ. Accuracy in peripheral nerve regeneration. Trends Neurosci 1981;
4: 18-20.
28. Rafuse VF, Gordon T. Self-reinnervated cat medial gastrocnemius muscles. II. Analysis
of the mechanisms and significance of fiber type grouping in reinnervated muscles. J
Neurophysiol 1996; 75: 282-297.
29. Ribchester RR. Development and plasticity of neuromuscular innervation. In: Kalverboer AF, Gramsbergen A, eds. Handbook of brain and behaviour in human development. Dordrecht, The Netherlands: Kluwer; 2001. p 261-342.
30. Rich M, Lichtman JW. Motor nerve terminal loss from degenerating muscle fibers.
Neuron 1989; 3: 677-688.
31. Rosenheimer JL, Smith DO. Differential changes in the end-plate architecture of functionally diverse muscles during aging. J Neurophysiol 1985; 53: 1567-1581.
32. Sávay G, Csillik B. The effect of denervation of the cholinesterase activity of motor
endplates. Acta Morph Acad Sci Hung 1956; 6: 261-342.
33. Shen N, Zhu J. Application of sciatic function index in nerve functional assessment.
Microsurgery 1995; 16: 552-555.
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