University of Groningen
Muscular reinnervation and differentiation after peripheral nerve transection
IJkema-Paasen, Josina
IMPORTANT NOTE: You are advised to consult the publisher's version (publisher's PDF) if you wish to
cite from it. Please check the document version below.
Document Version
Publisher's PDF, also known as Version of record
Publication date:
2005
Link to publication in University of Groningen/UMCG research database
Citation for published version (APA):
IJkema-Paasen, J. (2005). Muscular reinnervation and differentiation after peripheral nerve transection s.n.
Copyright
Other than for strictly personal use, it is not permitted to download or to forward/distribute the text or part of it without the consent of the
author(s) and/or copyright holder(s), unless the work is under an open content license (like Creative Commons).
Take-down policy
If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately
and investigate your claim.
Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons the
number of authors shown on this cover page is limited to 10 maximum.
Download date: 18-06-2017
9
GENERAL DISCUSSION
Chapter 9
115
The clinical problem
Peripheral nerve injury is a frequently occurring complication of trauma due
to traffic accidents, sports accidents or otherwise. The extremities are often
affected and if such injury comprises a disruption of the nerve including the
surrounding myelin sheath, surgical intervention is needed. Despite advanced
surgical techniques and the application of autologous nerve grafts or artificial nerve
guides, functional outcome generally is poor31;34-36;39;40. Research is needed, into
optimalization of surgical techniques and protocols, into the processes involved
in the reinnervation, into new nerve guides which allow long range outgrowth of
nerve fibres and into the reactions of the tissues denervated by the transection.
Results hopefully may enhance clinical prospects and help to design improved
therapeutical strategies. A field of research that has been relatively neglected
sofar is the effects of a nerve transection and a temporary denervation on muscle
morphology and the innervation of muscles. This field is the topic of my thesis.
The experimental animal, the peripheral nerve
It was decided to study the effects of a transection of the sciatic nerve in adult
rats (in the first part) as well as in young rats (in the second part). The sciatic
nerve innervates a variety of muscles, among which, the gastrocnemius, tibialis
anterior and soleus muscles, as well as skin areas in the foot region. The tibialis
anterior muscle is a hindlimb flexor and the gastrocnemius and soleus muscles
are hindlimb extensors and this indicates that the branches of the sciatic nerve
innervate antagonist muscles. From an experimental point of view, this enables to
study the effects of a transection in muscles with different properties, and this also
allows to study behavioral consequences of a transection and reinnervation, by
observing walking performance, and neurophysiological consequences by recording
EMG patterns. The sciatic nerve in rats, basically is similar in its properties and
morphology to peripheral nerves of a mixed character in the human, and, besides,
this nerve is easily accessible for surgery, for the implantation of nerve grafts or
nerve guides and for histological inspection after experimentation.
In our experiments, we transected and repaired the sciatic nerve on one side
(in general the left side) and we concentrated on the effects on muscle morphology
of the soleus (SOL), the lateral gastrocnemius (LGC) and the tibial (TA) muscles.
Chapter 9
Observations and countings at the side of the lesion were compared to those at the
contralateral side. We also studied whether parameters of this “control” side had
changed in comparison to those in normal rats. The research questions comprise
the effects of a transection on the muscles, on the innervation of the muscles,
and in the second part we concentrate upon the question whether a sciatic nerve
116
transection at young age has less deleterious effects on muscle morphology, on
behavior and other functional aspects than at adult age.
Changes in muscles after a transection at adult age
In the first part of my thesis, we studied the effects of the unilateral removal
of a section of 12 mm from the sciatic nerve, and the implantation of this section
in a reversed orientation. This lesion was made proximal to the bifurcation of
the nerve into its two main branches, the common peroneal nerve and the tibial
nerve.
Muscles after denervation, gradually diminish in size and the numbers
of muscle fibers decrease over a period of weeks, a phenomenon known as
denervation atrophy. This atrophy affects the red (type I) and white (type II)
fibers equally49. In our experiments we observed in the SOL, the TA and the
LGC muscles a decrease in cross sectional areas by about 30% after 7 weeks
(chapter 2) and similar results were obtained in other research23;49;51. The atrophy
of the muscle fibers appeared to be reversible during a long period of time33 and
the same has also been demonstrated in human patients26. Reinnervation in our
research started before 7 weeks after the transection (see, below) and after 21
weeks the cross sectional areas in the TA and LGC had regained the values as
observed at the control side, and this held as well for the numbers of muscle fibers
(chapter 2). The SOL muscle, however, remained smaller and also the numbers of
muscle fibers were decreased in comparison with the control side.
The most important changes we observed after a transection were shifts in
the proportions and the regional distributions of the type I and type II muscle
fibers in the muscles of the rats’ hindlimb. Normally, the TA contains 2 – 3% of
type I muscle fibres, the LGC between 10 and 20%, but the SOL has 80 - 85%
of type I muscle fibers. After reinnervation we observed an initial increase in the
percentages of type I muscle fibers in the TA and LGC until 15 weeks, but at 21
weeks after the transection these percentages had returned to values approaching
normal ranges. In the SOL, on the other hand, the type II muscle fibers steadily
increased during this period and at 21 weeks we observed that 80% of the fibers,
phenotypically, were of type II. As far as we know, this is the first time that the
trends in these three muscles collectively have been described. These changes
imply that the nerve transection leads to a more or less common fibre type
distribution in all the muscles affected.
In an earlier experiment, we recorded EMG patterns in the LGC and the TA
muscles during walking in rats after a sciatic nerve transection18. The results showed
Chapter 9
a marked coactivation of these antagonists and these were interpreted such that
after transection, the outgrowing axons aselectively and randomly reinnervate the
muscles. This conclusion was supported by experiments in which we retrogradely
traced the motoneurones connected to these muscles. Many motoneurones
appeared to be far outside the normal territories of the respective motoneuronal
to an at-random reinnervation.
117
pools18. Results by Bodine Fowler et al.8 are in line with our interpretation pointing
On the basis of these findings, we hypothesized that the trends towards a
common fibre type compositions in the reinnervated muscles is the consequence
of the at-random reinnervation of the muscles. Crucial to this hypothesis obviously
is, that muscle fibres in adult rats adjust to the properties of the newly innervating
motoneurones. The classical experiment on cross-innervation in kittens and
adult cats by Buller et al. indeed points to a decisive role of motoneurones in
the adjustments in muscle fibers10 (for extensive discussions see, chapter 2, and
also chapter 8). Cross uniting the axons originally innervating the “slow” SOL
muscle to the “fast” flexor digitorum longus muscle changed this muscle into a
slow muscle and vice versa (see also,27;53;57). Changes in the properties of the
muscle fibers, possibly are not only induced by alternative activation patterns of
the newly innervating motoneurones but also by neurotrophins. Neurotrophins,
released from the nerve ending might gain access to the muscle fiber through
endocytosis or by binding to receptors on the muscle fiber membrane where
they influence a second messenger system. This second messenger system in
turn, controls the expression of muscle protein-genes which may lead e.g. to an
increase of myosin heavy chain molecules. Recent research has pointed to NT3 as
a possible candidate48.
Although the fiber type compositions in the LGC and TA after a long
recovery are more or less within the normal ranges, an abnormality remains that
histochemically identical fibers are grouped together in these muscles (chapter 2).
This fiber type-grouping indicates previous denervation of the muscle13;24. Rafuse
and Gordon explained this clumping of muscle fibers by distal sprouting of motor
axons after entering into the muscle, leading to larger groups of muscle fibers
with identical histochemical properties41.
Denervation and reinnervation of the motor endplate
Recordings of action potentials over the muscle membrane showed that
after a sciatic nerve transection in the rat all electrical activity wanes within 2436 hours38. Soon thereafter, the neuromuscular junctions start to degenerate,
the complete disruption of the endplate taking only between 3 and 5 hours37.
The specialization in the basal membrane of the muscle fibre, the so-called sole
plate of the motor endplate in contrast, remains intact for several weeks or even
Chapter 9
months, as investigations e.g., in the frog have demonstrated42;60.
In our research on the fate of the motor endplate after denervation, and in
which we prevented the axons to grow out, all nerve fibers within the muscle
had disappeared by two weeks after transection (chapter 3). At that time, the
motor endplates had changed in their morphology, they had decreased in size,
118
were shrunken and sometimes they showed clear signs of degeneration and
fragmentation. However, only by 7 weeks all motor endplates had disappeared.
These findings illustrate that the motor endplates are much longer resistant to a
denervation than the terminal segments of the motoneuronal axon (chapter 3).
In case of reinnervation, it is generally taken that the former soleplate of
the motor endplate is the spot where reinnervating axons contact the muscle
fiber4;9;28;44. At 7 weeks, we already observed reinnervated motor endplates in all
three muscles and strikingly around 20% of the muscle fibers in the TA and the
LGC and 40% in the SOL were innervated by more than one axon, a polyneural
innervation. Probably, the terminal Schwann cells around the last axonal segment,
upon denervation upregulate the genes for GAP-43 production43;62, and they then
produce long, axon-like extensions to neighboring endplates. These outgrowths
seem to stimulate the new axonal sprouts to contact several endplates47. The
percentages of polyneurally innervated endplates had decreased to around 10%
in all muscle fibers at 21 weeks after the nerve transection. This decrease in
polyneural innervation might theoretically influence the fiber type distributions of
the reinnervated muscles. We indeed observed some changes between 7 and 21
weeks, suggesting that both processes might be related. (chapter 3).
Long term effects on fiber type distributions and innervation
After 7, via 15 and until 21 weeks after the nerve transection we observed
ongoing changes in fibre type distributions and innervation patterns and the
question obviously is, whether further changes occur after longer survival periods
(chapter 4). As the most prominent changes had occurred in the SOL muscle we
concentrated on that muscle. Even one year after transection, the muscle still
was smaller than the homologous muscle at the control side and the affected
muscle still contained preponderantly type II muscle fibers. The percentage of the
polyneurally innervated motor endplates had increased from a value of 10% at 21
weeks after the transection, to 20% at one year, and in parallel to that we counted
in these rats (which were close to two years old), 10% polyneurally innervated
motor endplates in the muscle at the control side. Possibly these increases at both
sides are phenomena related to a similar aging process.
The effects of the nerve transection at adult age summarized
After transection of the sciatic nerve and repair, the axons of the proximal
stump are able to sprout and grow back to the target areas via the distal stump
Chapter 9
of the nerve. The axons, however, are unable to relocate their former muscles and
reinnervation of the muscles is a random process. As a consequence of this random
reinnervation the affected muscles acquire a common fiber type distribution. This
random reinnervation obviously has dramatic consequences for the activation of
the muscles by segmental ciruits and suprasegmental brain areas. The results of
the research referred to above, in combination with results of functional effects
in fibre type distributions probably is an important factor in the impaired functions
119
after a transection indicate that the altered properties of the muscles by the shifts
of the affected extremity.
Nerve lesions at young age
Several reports indicate that extensive plexus lesions, sometimes occurring
during the birth of particularly, heavy babies, or after a breech delivery, or, nerve
transections in young children have a better outcome when compared to similar
lesions in adults3;15;20;21;30;52;55. Others, however, have questions this notion5;6.
Undoubtedly, sensory deficits recover more readily2 but prospects after lesions of
motor nerves particularly in cases of a total rupture are considered to be generally
poor. An important factor in functional recovery undoubtedly is an increased
compensational capacity of brain areas29. It seems, also in central compensational
processes, that sensory recovery due to central re-modeling seems to be much
better than motor recovery2.
Evidence from animal experiments is only scanty. It might be hypothesized
that nerve transections at young ages have less severe consequences as tropic
factors being effective during initial outgrowth (for review see17) might still be
present. On the other hand, the CNS including the spinal cord during development
is more vulnerable to peripheral injury because of an increased dependency upon
signals from the periphery1.
We choose to study the effects of a sciatic nerve transection in young rats.
Rats are born at an early stage of brain development. Romijn et al.45, on the basis
of parameters of brain development considered a rat of about 13 days after birth
to be at the same stage as human babies at term birth, and although Clancy et
al.11 thought this point should be set earlier in time, both studies indicate that a
rat in its postnatal period is similar, as far as the development of neuromuscular
development is concerned to a human before birth. Obviously, the rats’ birth at
an early stage of neural development has important experimental advantages, as
interference with early developmental stages can be performed postnatally.
A peripheral nerve transection at neonatal age in rats leads to the
upregulation of genes associated with cell death56 resulting in the death of
almost all motoneurones19;25;46;59. This is in contrast to such lesions at adult age
when almost all motoneurones survive transection8;50. We systematically studied
motoneuronal death after peripheral nerve transections and observed that such
Chapter 9
lesions at the 10th day leaves between 50 and 60% of the motoneurones alive,
and that age was chosen as the age for sectioning the sciatic nerve (chapter
5). At earlier ages less motoneurones survive, and strangely also transections
at the 15th day lead to increased cell death-counts. We hypothesized that this
increase after the 10th day in motoneurones innervating the SOL muscle is due
120
to impressive reorganizations taking place both in the muscle (a transfer from a
muscle with mainly type II into a muscle with mainly type I muscle fibres), in the
innervation (a regression of polyneural innervation) as well as in the innervating
motoneurones (a reorganization in the dendrites). This points to the important
rule that development does not proceed in a linear fashion61.
Sciatic nerve transection at the 10th postnatal day, consequences for
function
Walking patterns were severely impaired, from two–three weeks after
the transection until one year and we suppose that the deterioration of motor
performance started to deteriorate from the point at which the muscles became
reinnervated (chapter 6). EMG recordings of the gastrocnemius (GC) and the TA
muscles at the side of the transection at P10 we observed a coactivation of the TA
and GC muscle both during the stance and the swing phase. This and the badly
phased activation of the muscles in relation to the stance and the swing phase
indicated an at random reinnervation of these muscles. Retrogradely labeling the
muscles by injections into the newly reinnervated muscles demonstrated that the
motoneurones often were located outside the former domain of the pools of these
muscles (chapter 7). These results supported the hypothesis of an at-random
reinnervation after the sciatic nerve transection at P10.
Fibre type composition of the soleus muscle after early transection
The SOL muscle still is developing in many respects after the 10th postnatal
day. At the age of about one year after the transection, the muscle appeared to
contain mainly type II fibres. The fiber type composition, and also other aspects
of its morphology (the decreased size of the muscle, the occurrence of groups
with type I fibers) are very similar to that what we described in this muscle
after a transection of the sciatic nerve at adult age. Obviously, the mechanisms
and processes involved in directing the outgrowing axons towards their muscles
(effective during initial development) are not effective anymore after the 10th
postnatal day. It is interesting to note that such tropic mechanisms still are active
within muscles. Wang investigated the “regionalization” of type I muscle fibers in
the gastrocnemius muscle after sectioning the nerve close to its entry into this
muscle. In some rats the proximal end of the nerve was reconnected to the distal
part, but in others the nerve was connected at a more medial localization on
the muscle. These results demonstrated that the regionalization was maintained
Chapter 9
after recovery, indicating that the ingrowing fibres within the muscle are able to
relocate their predilectional region58.
Summary of the findings after a transection at the 10th day
Sciatic nerve lesion at the 10th postnatal day in rats resulted in an at-random
reinnervation of the muscles, severely impaired motor performance and as far as
results are very similar to those which we obtained after a sciatic nerve transection
121
the SOL muscle is concerned in a strongly abnormal fibre type distribution. These
in adult rats. They indicate that at the 10th postnatal day in the rat the processes
of pathfinding and routing are not effective anymore and that compensational
processes are not sufficient to alleviate functional impairments due to aberrant
neuromuscular connections.
Possible directions for future research
The major finding in my thesis is that after a transection of a peripheral nerve
containing axons to antagonist muscles, these are randomly reinnervated. This
occurs both after transections at adult age but also at young stages of development.
This mismatch leads to altered fiber type compositions and severely impaired
functions.
Functional recovery, after a disruption of peripheral nerves is dependent upon
two important factors (apart, obviously, from the cell bodies of the severed axons
vigorously supporting regrowth). These are, that the denervated tissue remains
receptive for the reinnervating axons, and secondly, that the axons are accurately
guided towards their former target area. In case of regrowth and reinnervation in
a reasonable period of time muscles and skin areas remain receptive. The second
factor provides the greater problems.
It is well known that the degenerating distal nerve stump after a transection
attracts the regrowing axons and it is generally agreed that the Schwann cells are
the most important source of these factors (such as NCAM, N-cadherin12;32 as well
as NGF, IGF and BDNF7;16;54). Successful regrowth towards the target generally
occurs if the basal lamina and the collagenous sheath around the nerve fibers
still is intact. In such cases, the axons grow along a well defined path and tropic
factors to direct the fibers are not implied. However, when the endoneurium is
disrupted, which is the case in transactions, then, the axons generally fail to
relocate their target. The identity is not known of factors that specifically might
direct the axons towards their own muscle or fiber group within a muscle. During
early development, probably an intricate interplay between on the one hand, the
timing of cell proliferation, neurite outgrowth and maturational stage of the target
cells, and on the other hand, tropic and trophic factors on the cell membrane
are decisive for optimal connectivity. It is know for a considerable time22, that
in embryonic development of the extremities, a simple topographical relation
Chapter 9
exists between the location of the motoneurones in the dorsolateral part of the
ventral horn, the outgrowth of their axons towards the mesenchymal cells in the
dorsal plate in the limb bud, the cells from which later, the flexor muscle develop.
Similarly, and somewhat earlier, the axons from the motoneurones in the more
ventral part of the ventral horn grow in the ventral ramus of the ventral root
122
towards the mesenchymal cells in the ventral plate, which later develop in the
extensor muscles14;22. Identifying the factors which are specific in the guiding
of this outgrowth (which might be effective next to factors such as timing of
outgrowth, and mechanical factors) might provide opportunities to adequately
sort outgrowing axons after the transection of a peripheral nerve with axons to
extensor and flexor muscles. Most probably, in-vitro experiments are needed to
identify and isolate these factors, and subsequently these might be tested in invivo preparations.
Chapter 9
123
REFERENCES
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
Chapter 9
18.
19.
20.
21.
124
22.
23.
Alvares D, Fitzgerald M. Building blocks of pain: the regulation of key molecules in
spinal sensory neurones during development and following peripheral axotomy. Pain
1999; Suppl 6: S71-S85.
Anand P, Birch R. Restoration of sensory function and lack of long-term chronic pain
syndromes after brachial plexus injury in human neonates. Brain 2002; 125: 113122.
Barrios C, de Pablos J. Surgical management of nerve injuries of the upper extremity
in children: a 15-year survey. J Pediatr Orthop 1991; 11: 641-645.
Bennett MR, McLachlan EM, Taylor RS. The formation of synapses in reinnervated
mammalian striated muscle. J Physiol 1973; 233: 481-500.
Birch R. Obstetric brachial plexus palsy. J Hand Surg [Br ] 2002; 27: 3-8.
Birch R, Raji AR. Repair of median and ulnar nerves. Primary suture is best. J Bone
Joint Surg Br 1991; 73: 154-157.
Bjerre B, Bjorklund A, Edwards DC. Axonal regeneration of peripheral adrenergic
neurons; effects of antiserum to NGF in mouse. Cell Tissue Res 1974; 148: 441-476.
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 1978; 278: 325-348.
Buller AJ, Eccles JC, Eccles RM. Interactions between motoneurones and muscles in
respect of the characteristic speeds of their responses. J Physiol 1960; 150: 417439.
Clancy B, Darlington RB, Finlay BL. Translating developmental time across mammalian
species. Neuroscience 2001; 105: 7-17.
Daniloff JK, Levi G, Grumet M, Rieger F, Edelman GM. Altered expression of neuronal
cell adhesion molecules induced by nerve injury and repair. J Cell Biol 1986; 103: 929945.
Dubowitz V, Brooke MH. Muscle biopsy: a modern approach. In: Walton JN, ed. Major
problems in neurology. London, Philadelphia, Toronto: W.B. Sauders Company Ltd.;
1973. Vol. 2, pp 12-101.
Francis-West PH, Antoni L, Anakwe K. Regulation of myogenic differentiation in the
developing limb bud. J Anat 2003; 202: 69-81.
Frykman GK. Peripheral nerve injuries in children. Orthop Clin North Am 1976; 7: 701716.
Glaze KA, Turner JE. Regenerative repair in the severed optic nerve of the newt
(Triturus viridescens): effect of nerve growth factor antiserum. Exp Neurol 1978; 58:
500-510.
Goodman CS, Tessier-Lavigne M. Molecular mechanisms of axon guidance and target
recognition. In: Cowan WM, Jessell TM, Zipursky SL, eds. Molecular and cellular
approaches to neural development. NY, Oxford: Oxford University Press; 1997. pp
108-178.
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.
Greensmith L, Vrbova G. Motoneurone survival: a functional approach. Trends Neurosci
1996; 19: 450-455.
Hoeksma AF, ter Steeg AM, Nelissen RG, van Ouwerkerk WJ, Lankhorst GJ, de Jong BA.
Neurological recovery in obstetric brachial plexus injuries: an historical cohort study.
Dev Med Child Neurol 2004; 46: 76-83.
Hudson DA, Bolitho DG, Hodgetts K. Primary epineural repair of the median nerve in
children. J Hand Surg [Br ] 1997; 22: 54-56.
Jacobson M. Developmental Neurobiology. NY, London: Plenum Press; 1971. 776 pp
p.
Jaweed MM, Herbison GJ, Ditunno JF. Denervation and reinnervation of fast and slow
Chapter 9
125
muscles. A histochemical study in rats. J Histochem Cytochem 1975; 23: 808-827.
24. Karpati G, Engel WK. “Type grouping” in skeletal muscles after experimental
reinnervation. Neurology 1968; 18: 447-455.
25. Kashihara Y, Kuno M, Miyata Y. Cell death of axotomized motoneurones in neonatal rats,
and its prevention by peripheral reinnervation. J Physiol 1987; 386: 135-148.
26. Kern H, Boncompagni S, Rossini K, Mayr W, Fano G, Zanin ME, Podhorska-Okolow
M, Protasi F, Carraro U. Long-term denervation in humans causes degeneration of
both contractile and excitation-contraction coupling apparatus, which is reversible by
functional electrical stimulation (FES): a role for myofiber regeneration? J Neuropathol
Exp Neurol 2004; 63: 919-931.
27. Kugelberg E, Edstrom L, Abbruzzese M. Mapping of motor units in experimentally
reinnervated rat muscle. J Neurol Neurosurg Psychiatry 1970; 33: 319-329.
28. Lüllmann-Rauch R. The regeneration of neuromuscular junctions during spontaneous
re-innervation of the rat diaphragm. Z Zellforsch Mikrosk Anat 1971; 121: 593-603.
29. Lundborg G. Nerve injury and repair-a challenge to the plastic brain. J Peripher Nerv
Syst 2003; 8: 209-226.
30. Lundborg G, Rosen B. Sensory relearning after nerve repair. Lancet 2001; 358: 809810.
31. Mackinnon SE, Dellon AL. Surgery of the peripheral nerve. Thieme, New York; 1988.
32. Martini R, Schachner M. Immunoelectron microscopic localization of neural cell adhesion
molecules (L1, N-CAM, and myelin-associated glycoprotein) in regenerating adult
mouse sciatic nerve. J Cell Biol 1988; 106: 1735-1746.
33. McComas AJ. Recovery of muslcle innervation. In: McComas AJ, ed. Skeletal muscle
form and function. Leeds: Human Kinetics; 1996. pp 259-272.
34. Meek MF, Den Dunnen WFA, Schakenraad JM, Robinson PH. Long-term evaluation of
functional nerve recovery after reconstruction with a thin walled biodegradable poly (DLlatide-ε-caprolactone) nerve guide, using walking tract analysis and electrostimulation
tests. Microsurgery 1999; 19: 247-253.
35. 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.
36. Meek MF, van der Werff JFA, Klok F, Robinson PH, Nicolai J-P, Gramsbergen A. Functional
nerve recovery after bridging a 15 mm rat sciatic nerve gap with a biodegradable nerve
guide. Scand J Plast Surgery 2003; 37: 258-265.
37. Miledi R, Slater CR. Electrophysiology and electron-microscopy of rat neuromuscular
junctions after nerve degeneration. Proc R Soc Lond B Biol Sci 1968; 169: 289-306.
38. Miledi R, Slater CR. On the degeneration of rat neuromuscular junctions after nerve
section. J Physiol 1970; 207: 507-528.
39. Politis MJ. Specificity in mammalian peripheral nerve regeneration at the level of the
nerve trunk. Brain Res 1985; 328: 271-276.
40. Pollock M, Harris AJ. Accuracy in peripheral nerve regeneration. Trends Neurosci 1981;
4: 18-20.
41. 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.
42. Reist NE, Magill C, McMahan UJ. Agrin-like molecules at synaptic sites in normal,
denervated, and damaged skeletal muscles. J Cell Biol 1987; 105: 2457-2469.
43. Reynolds ML, Woolf CJ. Terminal Schwann cells elaborate extensive processes following
denervation of the motor endplate. J Neurocytol 1992; 21: 50-66.
44. Rich M, Lichtman JW. Motor nerve terminal loss from degenerating muscle fibers.
Neuron 1989; 3: 677-688.
45. Romijn HJ, Hofman MA, Gramsbergen A. At what age is the developing cerebral cortex
of the rat comparable to that of the full-term newborn human baby? Early Hum Dev
1991; 26: 61-67.
46. Schmalbruch H. Motoneuron death after sciatic nerve section in newborn rats. J Comp
Neurol 1984; 224: 252-258.
126
Chapter 9
47. Son YJ, Thompson WJ. Schwann cell processes guide regeneration of peripheral axons.
Neuron 1995; 14: 125-132.
48. Sterne GD, Coulton GR, Brown RA, Green CJ, Terenghi G. Neurotrophin-3-enhanced
nerve regeneration selectivity improves recovery of muscle fibres expressing myosin
heavy chains 2b. J Cell Biol 1997; 139: 709-715.
49. Stonnington HH, Engel AG. Normal and denervated muscle. A morphometric study of
fine structure. Neurol 1973; 23: 714-724.
50. Streppel M, Angelov DN, Guntinas-Lichius O, Hilgers RD, Rosenblatt JD, Stennert E,
Neiss WF. Slow axonal regrowth but extreme hyperinnervation of target muscle after
suture of the facial nerve in aged rats. Neurobiol Aging 1998; 19: 83-88.
51. Sunderland S, Ray LJ. Denervation changes in mammalian striated muscle. J Neurol ,
Neurosurg and Psych 1950; 13: 159-177.
52. Tajima T, Imai H. Results of median nerve repair in children. Microsurgery 1989; 10:
145-146.
53. Tötösy de Zepetnek JE, Zung HV, Eredebil S, Gordon T. Motor-unit categorization based
on contractile and histochemical properties: a glycogen depletion analysis of normal
and reinnervated rat tibialis anterior muscle. J Neurophysiol 1992; 67: 1404-1415.
54. Turner JE, Glaze KA. Regenerative repair in the severed optic nerve of the newt (Triturus
viridescens): effect of nerve growth factor. Exp Neurol 1977; 57: 687-697.
55. van Ouwerkerk WJR, van der Sluijs JA, Nollet F, Barkhof F, Slooff ACJ. Management of
obstetric brachial plexus lesions: state of the art and future developments. Childs Nerv
Syst 2000; 16: 638-644.
56. Vanderluit JL, McPhail LT, Fernandes KJ, McBride CB, Huguenot C, Roy S, Robertson
GS, Nicholson DW, Tetzlaff W. Caspase-3 is activated following axotomy of neonatal
facial motoneurons and caspase-3 gene deletion delays axotomy-induced cell death in
rodents. Eur J Neurosci 2000; 12: 3469-3480.
57. Vrbova G, Gordon T, Jones R. Nerve-Muscle interaction. London: Chapman & Hall;
1995.
58. Wang, L. C. Regional organization of fibre types in normal and reinnervated hindlimb
muscles. Thesis, University of Groningen 2001; 97-112.
59. Watanabe O, Mackinnon SE, Tarasidis G, Hunter DA, Ball DJ. Long-term observations
of the effect of peripheral nerve injury in neonatal and young rats. Plast Reconstr Surg
1998; 102: 2072-2081.
60. Werle MJ, Sojka AM. Anti-agrin staining is absent at abandoned synaptic sites of frog
neuromuscular junctions. J Neurobiol 1996; 30: 293-302.
61. Westerga, J. Locomotion in the rat. Electrophysiological and neuroanatomical correlates
of normal and perturbed development. Thesis, University of Groningen 1993.
62. Woolf CJ, Reynolds ML, Chong MS, Emson P, Irwin N, Benowitz LI. Denervation of the
motor endplate results in the rapid expression by terminal Schwann cells of the growthassociated protein GAP-43. J Neurosci 1992; 12: 3999-4010.