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PubMed2000

Bioartificial nerve graft for bridging extended nerve defects in rat sciatic nerve based on resorbable guiding filaments.

A long defect (15 mm) in rat sciatic nerve was repaired with a bioartificial nerve graft composed of a silicone tube and seven synthetic filaments of five types (polyamide, catgut, polydioxanone, and two types of polyglactin, normal and quickly-absorbed) inserted longitudinally into the tube. In all cases in which filaments were used a regenerating bridge was obtained in the tube after three months in contrast to empty silicone tubes, in which no structure was observed. There was a 6%-46% recovery of isometric muscle contractility of the anterior tibial and gastrocnemius muscles with positive pinch reflex test in most cases. Myelinated axons were seen in the regenerating tissue between the filaments but not directly in contact with them, and there were varying numbers of macrophages close to the filaments. Silicone tubes with filaments, regardless of type of filament, induced nerve tissue to regenerate and resulted in functional recovery through a 15 mm nerve gap not achieved with empty tubes. Nerve promoting factors may be applied to the filaments and the model is a valuable tool for further development of artificial nerve grafts.

Animals↗
PubMed1983

Stimulation by ACTH4-10 of nerve fiber regeneration following sciatic nerve crush.

The number of newly formed myelinated nerve fibers was counted in the sciatic and tibial nerves in the rat following sciatic nerve crush. Beginning at days 8 and 14 in the sciatic and tibial nerve, respectively, the number of new myelinated fibers increased steadily and eventually exceeded the original number by 40 and 30%, respectively. This overshoot in nerve fibers was accompanied by the presence of clusters of fibers. Both the overshoot and the clusters disappeared at later stages and returned gradually to normal values within 3 months. Chronic administration of ACTH4-10 to the animals resulted in higher numbers of new myelinated nerve fibers throughout the process of regeneration. This stimulation was most pronounced (a three-fold increase) during the initial stages of regeneration. A higher number of myelinated nerve fibers was also observed in ACTH-treated rats 60 and 96 days after sciatic nerve crush. No changes in diameter of the fibers could be observed. The results are discussed in terms of a stimulation of the number of outgrowing nerve fibers caused by the peptide treatment.

Adrenocorticotropic Hormone↗
PubMed1994

Neonatal sciatic nerve section results in a rearrangement of the central terminals of saphenous and axotomized sciatic nerve afferents in the dorsal horn of the spinal cord of the adult rat.

Previous studies have shown that following neonatal peripheral nerve injury, adjacent intact myelinated and unmyelinated primary afferents sprout into the central denervated terminal area. The present study investigates this in more detail and goes further, to study the fate of the central terminals of the surviving axotomized primary afferent neurons. Bulk labelling of the sciatic and saphenous nerves with horseradish peroxidase conjugated to choleragenoid (B-HRP), to label the A fibres, or wheatgerm agglutinin (WGA-HRP), to label C fibres were employed to investigate the central consequences of sciatic nerve section and ligation on the day of birth, in adult rats. Bulk labelling of the axotomized sciatic or intact saphenous nerve with either tracer and comparison with contralateral controls revealed alterations to the terminal field. The intact saphenous nerve terminal field expanded caudally from mid L4 to the L4-L5 boundary when labelled with WGA-HRP and to the sacral cord when labelled with B-HRP. Labelling the axotomized sciatic nerve with either tracer revealed little change in the overall somatotopic organization of central terminals, although labelling was less intense compared to control nerves and more variable with WGA-HRP. Invasion of the substantia gelatinosa (SG) by axotomized A fibres was observed in segments L3-5, into the area occupied by axotomized C fibres. This area was also invaded by intact saphenous A fibres in the L4-5 segments. These results demonstrate that following neonatal nerve section: (i) axotomized primary afferents are able to retain a 'normal' somatotopic map in the rostrocaudal plane; (ii) both A and C fibres from adjacent intact nerves sprout into the denervated territory, but A fibres sprout further caudally; (iii) axotomized A fibres and invading intact A fibres both sprout dorsally into denervated SG. As a result, there is considerable overlap between nerve territories in denervated spinal cord, suggesting that competition for laminar termination sites exists between A and C fibres and also between axotomized and intact primary afferents.

Animals↗
PubMed1991

Changes in nerve fiber numbers distal to a nerve repair in the rat sciatic nerve model.

Changes in nerve fiber numbers distal to a nerve repair in the sciatic nerve of 48 rats were evaluated over a 1- to 24-month period. The results of the morphometric evaluation in the sciatic nerve distal to the nerve repair demonstrated an increase in nerve fiber counts as early as 1 month following the nerve repair. The number of nerve fibers in the distal nerve was greatest at 3 months and did not return to normal levels until 24 months. The results of this study will influence the timing of experimental studies in which nerve fiber counts are critical for evaluation, and provides a better understanding of the clinical events occurring following nerve repair.

Animals↗
PubMed1996

Presynaptic deficit of sympathetic nerves: a cause for disturbed sciatic nerve blood flow responsiveness in diabetic rats.

Reduced nerve blood flow is thought to play an important role in the pathogenesis of diabetic neuropathy. This disturbance in nerve blood flow might be the consequence of either microangiopathy or an impaired autonomic innervation of the vasa nervorum. In order to differentiate between a vascular or an adrenergic-autonomic defect as the underlying cause of the disturbed nerve blood flow, we investigated the effects of the adrenocorticotropic hormone [ACTH]-(4-9) analogue Org 2766 on sciatic nerve blood flow under basal and adrenergic-stimulated conditions. Org 2766 has neuroprotective effects without cardiovascular effects. Treatment with Org 2766 was started 6 weeks after the induction of experimental diabetes mellitus. At week 12 the sciatic nerve blood flow, measured by laser-Doppler flowmetry, was reduced to 60% of the non-diabetic level; blood pressure was unchanged in diabetic rats compared to non-diabetic rats. Basal haemodynamic values were not affected by Org 2766 treatment. Vasa nervorum adrenergic responsiveness to tyramine (presynaptic) and phenylephrine (postsynaptic) was investigated. Diabetic rats showed adrenergic hyporesponsiveness. Treatment with Org 2766 restored the reduced presynaptic response to tyramine without affecting the reduced postsynaptic response to phenylephrine. It is concluded that a presynaptic-sympathetic deficit of nervi vasorum causes a disturbed flow responsiveness in diabetic rat sciatic nerve and that adrenergic autonomic disturbances in the vasa nervorum have only a small role in the reduced basal nerve blood flow of diabetic rats.

Adrenocorticotropic Hormone↗
PubMed1990

Effects of dibutyryl cyclic adenosine monophosphate, ACTH(4-10) and gangliosides on nerve fiber regeneration after rat sciatic nerve tubulization.

Tubulization of sectioned rat sciatic nerves was used to evaluate the effect of dibutyryl cyclic adenosine monophosphate (db-cAMP), a fragment of the adrenocorticotrophic hormone (ACTH(4-10] and gangliosides on the regrowth of injured nerve processes. Four weeks post-operative, the number of myelinated fibers was counted at different levels of the lesioned sciatic nerves and the endoneurium surface of the bridging structure in the tube was measured. Animals treated with gangliosides and db-AMPc showed statistically significant differences compared to vehicle treated rats. The gangliosides have shown a beneficial effect but db-cAMP diminished the number of myelinated fibers. In this case, an implication of Schwann cell mitosis and migration is discussed. In spite of better results obtained in ACTH(4-10)-treated animals compared to controls, the differences did not attain a statistically significant level. These experiments confirm the beneficial effect of gangliosides on peripheral nerve regeneration and reveal a negative effect of db-cAMP in the regeneration chamber model.

Adrenocorticotropic Hormone↗
PubMed1997

The action of local anesthetics on myelin structure and nerve conduction in toad sciatic nerve.

X-ray scattering and electrophysiological experiments were performed on toad sciatic nerves in the presence of local anesthetics. In vitro experiments were performed on dissected nerves superfused with Ringer's solutions containing procaine, lidocaine, tetracaine, or dibucaine. In vivo experiments were performed on nerves dissected from animals anesthesized by targeted injections of tetracaine-containing solutions. In all cases the anesthetics were found to have the same effects on the x-ray scattering spectra: the intensity ratio of the even-order to the odd-order reflections increases and the lattice parameter increases. These changes are reversible upon removal of the anesthetic. The magnitude of the structural changes varies with the duration of the superfusion and with the nature and concentration of the anesthetic molecule. A striking quantitative correlation was observed between the structural effects and the potency of the anesthetic. Electron density profiles, which hardly showed any structural alteration of the unit membrane, clearly indicated that the anesthetics have the effect of moving the pairs of membranes apart by increasing the thickness of the cytoplasmic space. Electrophysiological measurements performed on the very samples used in the x-ray scattering experiments showed that the amplitude of the compound action potential is affected earlier than the structure of myelin (as revealed by the x-ray scattering experiments), whereas conduction velocity closely follows the structural alterations.

Action Potentials↗
PubMed1984

Magnesium enhances local anesthetic nerve block of frog sciatic nerve.

The present study was designed to examine the effects of increased magnesium concentration on the nerve block produced by lidocaine, benzocaine, and QX 572 (a quaternary derivative of lidocaine). Desheathed whole sciatic nerves from northern Rana pipiens frogs were placed in a sucrose gap chamber and stimulated at various frequencies at supramaximal intensity for the activation of the compound action potential. After control studies, the nerve was bathed by a calcium-free frog Ringer's solution containing magnesium concentrations of 3.0, 10.0, or 20.0 mM with or without 0.5 mM lidocaine, 0.5 mM benzocaine, or 0.75 mM QX 572. Compound action potentials were measured, and nonfrequency and frequency dependent blocks were compared in each solution. Increased magnesium ion concentration, in the absence of local anesthetics, enhanced the nonfrequency dependent block but did not change the frequency dependent block. All three local anesthetics enhanced both types of block. Increased magnesium concentrations enhanced only the nonfrequency dependent benzocaine block. In contrast, increased magnesium enhanced both types of block produced by QX 572 and lidocaine. These results suggest a potentially important interaction between high magnesium concentrations and local anesthetic nerve blocks.

Action Potentials↗
PubMed1989

Expression of growth-associated protein B-50 (GAP43) in dorsal root ganglia and sciatic nerve during regenerative sprouting.

Recently it has been shown that B-50 is identical to the neuron-specific, growth-associated protein GAP43. The present study reports on the fate of B-50/GAP43 mRNA and B-50/GAP43 protein, determined by radioimmunoassay, in a rat model of peripheral nerve regeneration (sciatic nerve crush) over a period of 37 and 312 d, respectively. Moreover, the effects of repeated subcutaneous injection of the neurotrophic peptide Org.2766 (an ACTH4-9 analog) and of a conditioning lesion on B-50/GAP43 protein levels in the regenerating nerve and dorsal root ganglia (DRG) were investigated. Both treatments enhanced the functional recovery as evidenced by a foot-flick withdrawal test. Immunocytochemical analysis using antineurofilament antibodies revealed a peptide-induced increase in the number of outgrowing sprouts in the sciatic nerve. Both the peptide and the conditioning lesion amplified the crush lesion-induced increase in B-50 protein content in the nerve as determined by radioimmunoassay. B-50 protein levels seem to correlate proportionally with the number of sprouts. In the DRG of the crushed sciatic nerve, the time course of B-50 expression was studied. B-50 mRNA was quantified from Northern blots. A linear increase up to 10 times the basal level of B-50 mRNA was observed 2 d postsurgery, followed by a gradual decline to normal levels at day 37. The first significant rise in B-50 mRNA level became apparent between 8 and 16 hr after placement of the crush lesion. The first significant rise in B-50 protein level occurred 40 hr after the crush lesion, reaching a plateau of 3 times the basal level between day 6 and 20. B-50 protein levels in DRG cell bodies remained elevated up to 60 d after crush, a period much longer than that observed for B-50 mRNA. Thus, during a later phase of peripheral axonal regeneration, the presence of B-50 appears to be prolonged, probably by an increase in half-life and not so much by enhanced transcription. Treatment with Org.2766 did not affect the B-50/GAP43 levels in DRG cell bodies during the first 6 d following crush. Conditioning lesion resulted in a DRG B-50/GAP43 protein amount at the same level as in rats 14 d after the test lesion. B-50/GAP43 levels in DRG are probably influenced by the rapid axonal transport of the protein, as has been reported by others.

Adrenocorticotropic Hormone↗
PubMed1994

Bipartite piriformis muscle: an unusual cause of sciatic nerve entrapment.

The sciatic nerve usually emerges below the piriformis muscle; however, variations of the relationship between the sciatic nerve and piriformis muscle are occasionally encountered. In a 28-year-old woman with sciatica, entrapment of the sciatic nerve by a bipartite piriformis muscle was found. She was treated by dissection of the lower head of the piriformis muscle and restitution of the normal anatomical relationship between the nerve and piriformis muscle. Sciatica resolved postoperatively.

Adult↗
PubMed2001

Sciatica due to malignant nerve sheath tumour of sciatic nerve in the thigh.

Malignant peripheral nerve sheath tumour (MPNST) is a rare malignant neoplasm arising from the supportive non-neural component of the peripheral nerves. An unusual case of pain and weakness of the foot and calf muscles due to a giant MPNST of the sciatic nerve in the posterior compartment of the thigh is presented. The patient was already investigated as a case of sciatica due to a lumbar disc disease with a negative magnetic resonance imaging and then unsuccessfully operated elsewhere twice, with a misdiagnosis of tarsal tunnel syndrome. Neurosurgical referral prompted a diagnostic magnetic resonance study of the thigh, revealing the lesion, which was completely excised microsurgically with total relief in the pain and partial improvement in the weakness and sensations in the sole of the foot.

Adult↗
PubMed1989

Tellurium-induced neuropathy: metabolic alterations associated with demyelination and remyelination in rat sciatic nerve.

Rats fed a diet containing 1.25% elemental tellurium initiated on postnatal day 20 undergo a transient neuropathy characterized by synchronous demyelination of peripheral nerves. In sciatic nerve, the extent of demyelination was maximal after 5 days of tellurium exposure; there was a loss of 25% of the myelin, as assayed by concentration of myelin-specific P0 protein. Tellurium-induced alterations in the metabolic capacity of Schwann cells were examined by measuring the synthesis of myelin lipids in vitro in isolated sciatic nerve segments. Exposure to tellurium resulted in an early marked decrease of approximately 50% in overall incorporation of [14C]acetate into lipids, with a preferential depression in synthesis of cerebrosides, cholesterol, and ethanolamine plasmalogens (components enriched in myelin). Most dramatically, within 1 day of initiation of tellurium exposure, there was a profound increase in [14C]acetate-derived radioactivity in squalene; 23% of incorporated label was in this intermediate of cholesterol biosynthesis, compared to less than 0.5% in controls. In association with the remyelinating phase seen after 5 days of tellurium exposure, synthesis of myelin components gradually returned to normal levels. After 30 days, metabolic and morphologic alterations were no longer apparent. We suggest that the sequence of metabolic events in sciatic nerve following tellurium treatment initially involves inhibition of the conversion of squalene to 2,3-epoxysqualene, and that this block in the cholesterol biosynthesis pathway results, either directly or indirectly, in the inhibition of the synthesis of myelin components and breakdown of myelin.

Acetates↗
PubMed1991

Transfer of 45Ca and 36Cl at the blood-nerve barrier of the sciatic nerve in rats fed low or high calcium diets.

Unidirectional fluxes of 45Ca, 36Cl, and of [3H]mannitol from blood into the sciatic nerve and cerebral cortex were determined from 5- and 15-min uptakes of these tracers after an intravenous (i.v.) bolus injection in awake rats. Rats were fed diets for 8 wk, that had either a low (0.01% wt/wt), normal (0.67%), or high (3%) Ca content. Plasma [Ca] was 32% less and 11% more in rats fed low (LOCA) and high Ca diets (HICA), respectively, than in rats fed a normal Ca diet (CONT). The mean permeability-surface area product (PA) of 45Ca at the blood-nerve barrier was about eightfold higher than at the blood-brain barrier in the same animals and did not differ significantly between groups (greater than 0.05). Mean PA ratios of 45Ca/36Cl for the blood-nerve and blood-brain barriers in CONT rats, 0.52 +/- 0.04 and 0.40 +/- 0.02, respectively, were not significantly different from corresponding ratios in LOCA and HICA groups, and corresponded to the aqueous limiting diffusion ratio (0.45). Our results show no evidence for concentration-dependent transport of Ca over a plasma [Ca] range of 0.8-1.4 mmol/liter at the blood-nerve barrier of the rat peripheral nerve, and suggest that Ca and Cl exchange slowly between nerve and blood via paracellular pathways.

Animals↗
PubMed2003

Comparing the effects of femoral nerve block versus femoral and sciatic nerve block on pain and opiate consumption after total knee arthroplasty.

The goal of this study was to compare femoral and femoral plus sciatic nerve blocks in the postoperative pain management of patients undergoing total knee arthroplasty (TKA). A total of 97 patients participated in a convenience sample, comparative study. Patients who received femoral nerve block only (n = 30) reported statistically higher pain scores (P <.05) and showed 61% higher opiate consumption than those who received femoral and sciatic nerve blocks (n = 67) in the first 24 hours after surgery. The results suggest that the combined femoral and sciatic nerve block provides superior pain management in the early postoperative period after TKA.

Aged↗
PubMed2003

Carbon dioxide laser-assisted nerve repair: effect of solder and suture material on nerve regeneration in rat sciatic nerve.

In order to further improve and explore the role of lasers for nerve reconstruction, this study was designed to investigate regeneration of sharply transected peripheral nerves repaired with a CO(2) milliwatt laser in combination with three different suture materials and a bovine albumin protein solder as an adjunct to the welding process. Unilateral sciatic nerve repair was performed in 44 rats. In the laser group, nerves were gently apposed, and two stay sutures (10-0 nylon, 10-0 polyglycolic acid, or 25 microm stainless steel) were placed epi/perineurially. Thereafter, the repair site was fused at 100 mW with pulses of 1.0 s. In the subgroup of laser-assisted nerve repair (LANR), albumen was used as a soldering agent to further reinforce the repair site. The control group consisted of nerves repaired by conventional microsurgical suture repair (CMSR), using 4-6 10-0 nylon sutures. Evaluation was performed at 1 and 6 weeks after surgery, and included qualitative and semiquantitative light microscopy. LANR performed with a protein solder results in a good early peripheral nerve regeneration, with an optimal alignment of nerve fibers and minimal connective tissue proliferation at the repair site. All three suture materials produced a foreign body reaction; the least severe was with polyglycolic acid sutures. CMSR resulted in more pronounced foreign-body granulomas at the repair site, with more connective-tissue proliferation and axonal misalignment. Furthermore, axonal regeneration in the distal nerve segment was better in the laser groups. Based on these results, CO(2) laser-assisted nerve repair with soldering in combination with absorbable sutures has the potential of allowing healing to occur with the least foreign-body reaction at the repair site. Further experiments using this combination are in progress.

Albumins↗
PubMed2003

Microneurography in anesthetized rats for the measurement of sympathetic nerve activity in the sciatic nerve.

Microneurography is widely used for the measurement of human peripheral sympathetic nerve activity (SNA) in conscious subjects by virtue of its low invasive nature, but has rarely been employed in animal experiments. Because the low invasive nature sometimes is very useful even in animal experiments, we tested its feasibility for the measurement of SNA in the sciatic nerve of the anesthetized rat, aiming in particular to establish a methodology for measurement. A tungsten microelectrode was inserted into the nerve exposed at the thigh level to detect the "spontaneous, intermittent burst" signal that is one of the main characteristics of compound SNA. Such signals were found in more than 70% of experiments after surgical operators became accustomed to the method. Whenever such signals were detected, electrical stimulation of the sympathetic chain resulted in induced action potentials detected with the microelectrode after a reasonable conduction period. The spikes were successfully reduced after administration of hexamethonium bromide, a sympathetic ganglion blocker. On the other hand, induced spikes were never observed when we failed to find the "spontaneous, intermittent burst" signal. The results demonstrate the feasibility of microneurography in evaluating SNA in anesthetized small animals, and that the "spontaneous, intermittent burst" signal may be sufficient to identify SNA.

Anesthesia↗