Rat Peroneal Nerve Research Articles

Artificial Nerve Graft Using Collagen as an Extracellular Matrix for Nerve Repair Compared with Sutured Autograft in a Rat Model

A study was conducted to compare the regeneration of rat peroneal nerves across 0.5-cm gaps repaired with artificial nerve grafts versus sutured autografts. The artificial nerve graft model is composed of a synthetic biodegradable passive conduit made of polyglycolic acid filled with a collagen extracellular matrix (predominantly Type I collagen, derived from calf skin, and with the telopeptide ends left intact). Axonal regeneration was studied in 22 long-term animals (11 or 12 months). The nerves were studied by qualitative and quantitative histological and electrophysiological methods, and by functional analysis in 9 of the animals. The axonal regeneration of the artificial nerve graft is equal to sutured autografts as measured by axonal counts, and by physiological and functional methods, although the sutured autografts demonstrated statistically superior axonal diameters.

Acute stages of batrachotoxin-induced neuropathy: a morphologic study of a sodium-channel toxin

The acute effects of batrachotoxin, a steroidal neurotoxin which opens the membrane sodium channel, were observed morphologically at various time points up to 3 h after injection into rat peroneal nerve. Three changes were found. First, there was massive swelling of the axon at the node of Ranvier accompanied by retraction of paranodal myelin. Second, a similar swelling of unmyelinated axons was seen. Third, extracellular fluid accumulated along the internode in the adaxonal space, the intraperiod line of myelin and, rarely, the external mesaxon, with concomitant shrinkage of the axon. The first two changes might be explained on the basis of massive shift of sodium through the batrachotoxin-modified sodium channel into the axon and subsequent osmotic shift of fluid. The reason for the third change is not clear but probably also has a ionic basis.

Potassium ion channel blockade restores conduction in heat-injured nerve and spinal nerve roots

Compound action potentials were recorded in vitro from rat peroneal and sural nerves and from dorsal and ventral roots of the cauda equina before and after radiofrequency heating of 5-mm-length segments of these nerves to 41 to 45°C. The heating was continued for intervals sufficient to reduce response amplitude by 50%. Inflection velocity, potential duration at 1 2 peak height, and the proportion of conducting Aα fibers were also measured. The topical application of 4-aminopyridine (4-AP) and tetraethylammonium chloride (TEA) to the previously heated segments immediately following the radiofrequency injury completely or near-completely restored amplitude height to the preheat value in all experiments. Aα sensory fibers were the most susceptible to the conduction block. Conduction in these fibers was also the most readily restored by the application of 4-AP or TEA. The effects of TEA, but not of 4-AP, could be reversed by saline or buffer washing. Topical application of verapamil and of magnesium or calcium ions had no discernible effect on heated nerves. We suggest that the mechanism of heat-induced conduction block may be similar to that from early demyelination or stretch injury. Further, motor and sensory Aα fibers differ both in their vulnerability to heat and in their subsequent response to the application of potassium channel blockers.

Microwave irradiation of peripheral nerve following injury: A structural analysis of degeneration and regeneration

Studies of the enhancement effect of pulsed energy irradiation on nerve regeneration following injury have produced variable results. The effect of microwave treatment on the rat peroneal nerve after transection and anastomosis was analyzed by light and electron microscopy. The hindquarters were irradiated 1 h/day during the first 10 days postoperative (dpo). The nerves were fixed in situ and prepared for microscopic analysis. At 10 dpo the distal segment of the degenerating nerve had several enlarged myelin sheath profiles devoid of axoplasm. The swelling was not significantly altered by microwave treatment, but the number and density of the empty myelin sheath profiles were three to four times greater in the treatment group. At 49 dpo the regenerating nerve segment had a 43% decrease in the nerve fiber diameter compared with a normal mean of 7 μm. The number and density of remyelinated fibers showed a 50% increase in both treatment and control groups. Histologic evidence indicated no permanent enhancement on nerve regeneration by microwave treatment, even though the treatment may have delayed Wallerian degeneration.

Axonal caliber and neurofilaments are proportionately decreased in galactose neuropathy.

Feeding galactose to rats induces nerve conduction abnormalities, increased levels of nerve galactitol, endoneurial edema, elevated pressure and hypoxia of endoneurial fluid, and pathological abnormalities of nerve fibers. To investigate the cellular mechanisms of the fiber lesions and their possible relationship to alterations in the nerve microenvironment, rat peroneal nerves were morphometrically evaluated eight months after the commencement of galactose feeding. Whereas the density of neurofilaments (NF/micron2) in the transverse axonal area of myelinated fibers was not significantly different between the nerves of galactose-fed and control rats, axonal areas and the number of NF/axon, when related to myelin spiral length, were significantly less in nerves of galactose-fed rats. Myelin alterations, characteristic of axonal atrophy, were also significantly increased. The present data provide evidence of a proportionate decrease in axonal caliber and the number of NF/axon in myelinated fibers in experimental galactose neuropathy, suggesting that galactose induces fibers in experimental galactose neuropathy, suggesting that galactose induces either decreased NF synthesis, assembly or transport. The possible role of microenvironmental alterations, including endoneurial hypoxia and hyperosmolarity, in the production of this axonal atrophy is discussed.

Effects of high-peak pulsed electromagnetic field on the degeneration and regeneration of the common peroneal nerve in rats

Apart from preliminary notices of present work, previous reports of experimental and clinical trials of the effects of a high-peak pulsed electromagnetic field (PEMF) on degeneration and regeneration of peripheral nerves lacked statistical analysis. Therefore, we designed experiments with standardised operative, histological, cytological and morphometric techniques to assess the effect of PEMF on lesions of the common peroneal nerves in paired male rats matched for age, environmental conditions and level and type of lesion. One of two types of lesion was induced in the left common peroneal nerve: in 12 pairs of rats the nerve was crushed just above the knee and in the remaining 12 pairs the nerve was cut and immediately sutured at the same level. The right common peroneal nerve of each rat served as a control. Animals received 15 minutes of PEMF produced by a Diapulse machine or sham treatment daily for periods ranging from three and a half days to eight weeks after injury. Healthy nerves were unaffected, but after damage there were statistically significant differences between PEMF treated and sham treated rats. PEMF accelerated the recovery of injured limbs and the degeneration, regeneration and maturation of myelinated axons; epineural, perineural and intraneural fibrosis was reduced; and the luminal cross-sectional area of intraneural vessels increased after both types of lesion. Findings are discussed and the need for clinical trials is stressed.

Biochemistry of rat single muscle fibres in newly assembled motor units following nerve crush.

A partial crush was applied surgically to the common peroneal nerves of rats, producing motor deficits lasting 4 weeks; the tibialis anterior muscles supplied by the crushed nerves were removed 5 weeks after recovery along with the contralateral control muscles. Myosin ATPase staining following pre-incubation at pH 4.5 was used to determine fibre types and to demonstrate areas of fibre-type grouping in the reinnervated areas of the muscles. Enzyme activities of lactate dehydrogenase (LDH), adenylokinase (AK) and malate dehydrogenase (MDH) were measured using micro-analytical techniques on the individual fibres within the histochemically identical groups and on fibres of the same types selected from areas of the test muscle or the contralateral control which appeared normal. The results show that the degree of enzymatic variation among single fibres reinnervated by a common axon is very small when compared to the general fibre population and, moreover, to fibres of the same histochemical type. Enzyme variability within the newly formed motor units was only slightly greater than the variability reported for normal motor units (Nemeth, Pette & Vrbová, 1981). The results indicate that skeletal muscle fibres originally having great differences in levels of enzyme activity, as demonstrated in the general fibre population, acquire considerable enzymatic similarity following reinnervation by a common motor neurone.

Consequences of axonal transport blockade by batrachotoxin on mammalian neuromuscular junction. III. An ultrastructural study

Ultrastructural alterations were analyzed following a single subperineural injection of batrachotoxin (BTX) into the rat peroneal nerve 10–12 mm proximal to its entrance into the extensor digitorum longus (EDL) muscle. At the injection site, most axons underwent reversible changes. Internodal segments of myelin degenerated and were phagocytized without apparent damage to the axon cylinders. Newly forming myelin sheaths were observed by 10 days after injection. Similarly, motor endplates were reversibly altered. By 18 h following injection, most nerve terminals were withdrawn from the postsynaptic elements but reinnervated original endplate regions between 7 and 10 days after injection. These observations explain earlier findings in which muscle membrane potential decreased immediately and spontaneous miniature endplate potentials (MEPPs) and evoked transmitter release were absent from 18 h to 7 days following injection. We suggest that these reversible changes were the result of an insufficient supply of neuronal materials due to BTX-induced blockade of fast axonal transport. Normal physiological function and morphology were restored after fast axonal transport recovered and sufficient quantities of appropriate materials necessary for the maintenance of the nerve terminals and muscle membrane potential were again transported distally from the nerve cell body.

Effects of high-peak pulsed electromagnetic field on the degeneration and regeneration of the common peroneal nerve in rats.

Apart from preliminary notices of present work, previous reports of experimental and clinical trials of the effects of a high-peak pulsed electromagnetic field (PEMF) on degeneration and regeneration of peripheral nerves lacked statistical analysis. Therefore, we designed experiments with standardised operative, histological, cytological and morphometric techniques to assess the effect of PEMF on lesions of the common peroneal nerves in paired male rats matched for age, environmental conditions and level and type of lesion. One of two types of lesion was induced in the left common peroneal nerve: in 12 pairs of rats the nerve was crushed just above the knee and in the remaining 12 pairs the nerve was cut and immediately sutured at the same level. The right common peroneal nerve of each rat served as a control. Animals received 15 minutes of PEMF produced by a Diapulse machine or sham treatment daily for periods ranging from three and a half days to eight weeks after injury. Healthy nerves were unaffected, but after damage there were statistically significant differences between PEMF treated and sham treated rats. PEMF accelerated the recovery of injured limbs and the degeneration, regeneration and maturation of myelinated axons; epineural, perineural and intraneural fibrosis was reduced; and the luminal cross-sectional area of intraneural vessels increased after both types of lesion. Findings are discussed and the need for clinical trials is stressed.

Studies on the control of myelinogenesis. 3. Signalling of oligodendrocyte myelination by regenerating peripheral axons

Continuing from earlier work which demonstrated the peripheral axonal regulation of Schwann cell myelination, this study has investigated the possibility that a peripheral axon can stimulate oligodendrocyte myelination. To test this hypothesis, regenerating PNS axons were allowed to interact with uncommitted oligodendrocytes by transecting a rat peroneal nerve and inserting a segment of the autologous optic nerve between the cut ends. Grafts were maintained for 4–28 weeks and then examined by light and electron microscopy. A few regenerating peripheral myelinated nerve fibers penetrated the optic nerve graft. Some axons penetrated the outer margin of the graft, were myelinated by Schwann cells, and surrounded by astrocyte processes bordered by basal lamina. More centrally in the optic nerve graft, regenerating peripheral axons displayed myelin of CNS type. The outer myelin lamella abutted directly on the plasmalemma surface of surrounding astrocytic processes and was expanded focally to form a glial tongue. These observations demonstrate the experimental induction of central myelination by regenerating peripheral axons and suggest the existence of a common neuronal mechanism to stimulate myelin formation by both the Schwann cell and the oligodendrocyte.

Regeneration of the node of Ranvier: a light and electron microscope study.

Regeneration of the node of Ranvier was investigated in the rat peroneal nerve 10-60 days after nerve crush, by light and electron microscopy. At 10 and 20 days after crush nodes of Ranvier were clearly identifiable by electron microscopy but had a relatively simple structure. At 40 days after crush however nodes were highly differentiated showing specialised features such as paranodal bulbs, nodal constriction of the axon, paranodal Schwann cell mitochondria, nodal Schwann cell microvilli, and nodal gap substance. By light microscopy some nodes were identifiable as early as 20 days after crush. At both 30 and 60 days after crush regenerated internodes were uniformly short (means of 275 micronm and 339 micronm respectively).

COPPER BINDING AT PNS NODES OF RANVIER DURING DEMYELINATION AND REMYELINATION IN THE PERINEURIAL WINDOW

Nodes of Ranvier of peripheral nerves are associated with mucopolysaccharide which is capable of binding a wide variety of cations. The present study has determined the changes in the binding properties of the node of Ranvier during demyelination and remyelination in the perineurial window. The location of copper ion binding, visualized as a dense copper ferrocyanide precipitate, was studied in teased fibres from 60 rat peroneal nerves with single perineurial windows and from 8 normal nerves. In normal nerves, precipitate was present over the nodal axon and at the borders of the paranodal axon. Before demyelination, severely beaded fibres sited within the perineurial window displayed a reduction or a loss of nodal precipitate. During the period of myelin phagocytosis and demyelination, precipitate was absent throughout the denuded axon but present at adjacent, uninvolved nodes. At the commencement of remyelination, precipitate appeared at the newlycreated nodal and paranodal regions and at interfaces between preserved and remyelinating internodes. The density increased with myelin thickening. These findings indicate: (1) severely beaded regions lose their normal binding property before undergoing demyelination, (2) demyelinated regions do not bind copper ions, (3) remyelinating fibres bind copper ions at newly‐created nodes and (4) Schwann cells are responsible for the production of nodal mucopolysaccharides.

Crush injury to peripheral nerve. An electron microscope study employing horseradish peroxidase.

Electron microscope observations were made of rat peroneal nerve after crushing using intravenously injected horseradish peroxidase (HRP) as a tracer protein to indicate changes in vascular permeability. At 1/2 h and 2 d after the crush there was gross leakage of HRP from damaged capillaries at the site of injury but none from vessels above or below this. Ultrastructurally vessels at the site of crush showed broken and separated endothelial cells. Proximally and distally there was little abnormal in the vessel walls; vesicles containing HRP were absent and tight-junctions between cells remained intact. Twenty-one days after the crush, leakage of HRP was found both at the site of crush and along the distal segment. The only change in vessel walls was an obvious increase in vesicles filled with HRP. Tracer was also found both in perivascular locations and throughout the endoneurial space.

Studies to improve fixation of human nerves: Part 3. Effect of osmolality of glutaraldehyde solutions on relationship of axonal area to number of myelin lamellae

When rat peroneal nerves were fixed under 5 different fixation schedules with various osmolalities (310, 410 and 900 milliosmoles), the frequency of abnormality of mitochondria in the axoplasm was lowest in myelinated fibers fixed with 6% glutaraldehyde in 0.1 M cacodylate buffer (900 milliosmoles). The relationship of axonal area to number of myelin lamellae was significantly different between high-osmolality fixation and low-osmolality fixation. Assuming that the number of myelin lamellae remains the same with fixation, there was a significant shrinkage in the axonal area of fibers with high-osmolality fixation. The amount of shrinkage was less in larger fibers than in smaller fibers fixed at high osmolality.

Studies to improve fixation of human nerves. IV. Effect of time elapsed between death and glutaraldehyde fixation on density of microtubules and neurofilaments.

Glutaraldehyde fixation of rat peroneal nerves after the animal was killed (simulated autopsy) was associated with a statistically significant decrease of density (number per unit area) of microtubules (MT) in comparison with controls (simulated biopsy). The density of MT decreased progressively with prolongation of time elapsed prior to glutaraldehyde fixation (1, 6, and 12 hours). Such a time effect was not demonstrated for density of neurofilaments.

Studies to improve fixation of human nerves: Part 1. Effect of duration of glutaraldehyde fixation on peripheral nerve morphometry

No change in the transverse fascicular area of rat peroneal nerve occurred when the duration of fixation in 2% glutaraldehyde was increased from 1 to 12 hr. Shrinkage in endoneurial area was inferred from the development of clefts. The number of myelin lamellae remained constant when the nerve was fixed in glutaraldehyde for 1 or for 12 hr. Unequivocal shrinkage of axis cylinders occurred with prolongation of glutaraldehyde fixation beyond 1 hr. In nerves fixed for 12 hr, this shrinkage was approximately 20%, compared to the area at 1 hr.

The Effect of Unilateral Section of the Peroneal Nerve of the Albino Rat on the Number of Myelinated Fibers in the Intact Nerve of the Opposite Side

The Effect of Unilateral Section of the Peroneal Nerve of the Albino Rat on the Number of Myelinated Fibers in the Intact Nerve of the Opposite Side