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PubMed2005

Induction of tumor necrosis factor-alpha in Schwann cells after gradual elongation of rat sciatic nerve.

BACKGROUND: Although limb lengthening has become a common treatment, the biochemical responses underlying the adaptation of elongated nerves are unclear. The purpose of this study was to clarify whether expression of cytokines and neurotrophins is altered in gradually elongated peripheral nerves. METHODS: Left sciatic nerves of adult rats were elongated by lengthening the femur up to 20 mm at a rate of 1, 2, or 20 mm/day. The ipsilateral and contralateral sciatic nerves of each group were resected 1, 4, 8, and 16 days after 20 mm of lengthening. mRNAs for interleukin-1beta, interleukin-6, tumor necrosis factor-alpha (TNFalpha), nerve growth factor, brain-derived neurotrophic factor, neurotrophin-3, and neurotrophin-4/5 were semiquantified by reverse transcription-polymerase chain reaction. Histological changes were assessed by immunoperoxidase and immunofluorescence staining. RESULTS: Expression of TNFalpha mRNA was markedly induced in the ipsilateral sciatic nerves of the gradually elongated, 1 mm/day and 2 mm/day groups, although to a lesser extent than in the acutely elongated, 20 mm/day group. In contrast, mRNAs for other factors remained undetectable. The mRNA level for TNFalpha in each group was highest 1 day after 20 mm of lengthening. The highly up-regulated level in the acute group declined rapidly within 4 days and slowly thereafter; in contrast, the decrease in the gradual groups was always slow. Even 16 days later, the levels in all groups remained significantly elevated. Unexpectedly, TNFalpha mRNA expression was also induced in the contralateral side of all groups. Immunohistochemical staining showed that TNFalpha-immunoreactive cells in gradually elongated nerves were also positive for S-100 protein but negative for proliferating nuclear cell antigen, indicating that TNFalpha was produced by nonproliferating Schwann cells. CONCLUSIONS: Gradual nerve elongation by limb lengthening induces production of TNFalpha in Schwann cells. Presumably, TNFalpha plays a critical role in the adaptation of peripheral nerves to elongation.

Animals↗
PubMed1987

Changes of nerve growth factor synthesis in nonneuronal cells in response to sciatic nerve transection.

The intact sciatic nerve contains levels of nerve growth factor (NGF) that are comparable to those of densely innervated peripheral target tissues of NGF-responsive (sympathetic and sensory) neurons. There, the high NGF levels are reflected by correspondingly high mRNANGF levels. In the intact sciatic nerve, mRNANGF levels were very low, thus indicating that the contribution of locally synthesized NGF by nonneuronal cells is small. However, after transection an increase of up to 15-fold in mRNANGF was measured in 4-mm segments collected both proximally and distally to the transection site. Distally to the transection site, augmented mRNANGF levels occurred in all three 4-mm segments from 6 h to 2 wk after transection, the longest time period investigated. The augmented local NGF synthesis after transection was accompanied by a reexpression of NGF receptors by Schwann cells (NGF receptors normally disappear shortly after birth). Proximal to the transection site, the augmented NGF synthesis was restricted to the very end of the nerve stump that acts as a "substitute target organ" for the regenerating NGF-responsive nerve fibers. While the mRNANGF levels in the nerve stump correspond to those of a densely innervated peripheral organ, the volume is too small to fully replace the lacking supply from the periphery. This is reflected by the fact that in the more proximal part of the transected sciatic nerve, where mRNANGF remained unchanged, the NGF levels reached only 40% of control values. In situ hybridization experiments demonstrated that after transection all nonneuronal cells express mRNANGF and not only those ensheathing the nerve fibers of NGF-responsive neurons.

Animals↗
PubMed1998

Late sciatic nerve entrapment following pelvic plate reconstruction in total hip arthroplasty.

Delayed sciatic neuropathy due to pelvic reconstruction plate loosening following complex acetabular reconstruction in total hip arthroplasty seems not be have been previously reported. We identified a 79-year-old woman who developed progressive neurologic signs of entrapment 6 months following reconstruction of a pelvic discontinuity due to fracture nonunion caused by radiation necrosis. Magnetic resonance imaging of the lumbar spine was unrevealing and electromyography demonstrated a peripheral neurogenic process involving the sciatic nerve. Sciatic nerve exploration was done at 12 months after surgery finding a loose screw in the pelvic plate impinging the nerve. Substantial improvement in clinical symptoms resulted from removal and nerve release.

Acetabulum↗
PubMed1993

Impaired induction of vasoactive intestinal polypeptide after sciatic nerve injury in the streptozotocin-diabetic rat.

This study was designed to assess the effects of experimental diabetes and nerve crush injury upon vasoactive intestinal polypeptide (VIP) content and axonal transport in the dorsal root ganglia (DRG) and sciatic nerve. Sciatic nerve crush injury in control and 3-week streptozotocin-diabetic rats was followed 6.5 days later by placement of 2 constricting ligatures above the site of injury. After 12 h, the L4 and L5 DRG and sciatic nerve were removed for VIP radioimmunoassay. Similar samples were also taken from control and diabetic rats whose nerve had been ligated without a preceding crush. VIP was increased over 2-fold in ganglia and 4-fold in nerves of crush-injured controls compared to uninjured controls (both P < 0.01). Crush injury also increased ganglion and nerve VIP in diabetic rats (P < 0.05 and 0.01, respectively) but the increase was less than what occurred in crush-injured controls (both P < 0.05). The accumulation of VIP proximal to a sciatic ligature was similar in control and diabetic rats and was not altered in either group by crush injury, while retrograde transport of VIP was initiated by crush injury in both control and diabetic rats. These data show that short-term diabetes does not alter the amount and peripheral axonal transport of VIP in the sciatic nerve but impairs the ability of peripheral nerve to respond to injury.

Animals↗
PubMed1999

Increase of galanin mRNA in lumbar dorsal root ganglion neurons of adult rats after partial sciatic nerve ligation.

Partial sciatic nerve ligation (PSNL) is a widely used model for the study of neuropathic pain. However, there is little information on neuropeptide expression in primary sensory neurons after PSNL. We examined galanin (GAL) mRNA expression in L4 and L5 dorsal root ganglion (DRG) neurons of adult rats after PSNL. We found that 4 and 14 days after PSNL the percentages of GAL mRNA positive neurons were significantly increased in the ipsilateral DRG compared to the contralateral side. Using combined retrograde fluorescent dye tracing and in situ hybridization, we found that 47% of the injured neurons and 10% of the spared neurons were GAL mRNA positive. Since only 2-3% of neurons in the contralateral uninjured DRG were GAL mRNA positive, PSNL induced up-regulation of GAL mRNA in both injured and spared DRG neurons.

Animals↗
PubMed1971

The geometry of peripheral myelin sheaths during their formation and growth in rat sciatic nerves.

In rat sciatic nerves, a small bundle of fibers was identified in which myelin sheaths were absent at birth, appeared within 3 days, and grew rapidly for 2 wk. During this interval, nerves were removed from littermates and were sectioned serially in the transverse plane. Alternating sets of thin and thick sections were used to prepare electron micrograph montages in which single myelinating axons could be identified and traced distally. During the formation of the first spiral turn, the mesaxon's length and configuration varied when it was studied at different levels in the same Schwann cell. The position of the mesaxon's termination shifted while its origin, at the Schwann cell surface, remained relatively constant. Along myelin internodes composed of two to six spiral turns, there were many variations in the number of lamellae and their contour. Near the mesaxon's origin, longitudinal strips of cytoplasm separated the myelin layers. Thicker sheaths were larger in circumference, more circular in transverse sections, and more uniform at different levels. Irregularities were confined to the paranodal region, and separation of lamellae by cytoplasm occurred at Schmidt-Lantermann clefts. Approximate dimensions of the bundle, its largest fibers, and their myelin sheaths were measured and calculated. The myelin membrane's transverse length and area increased exponentially with time; the growth rate increased rapidly during the formation of the first four to six spiral layers and remained relatively constant during the subsequent enlargement of the compact sheath.

Age Factors↗
PubMed1987

Differential regulation of mRNA encoding nerve growth factor and its receptor in rat sciatic nerve during development, degeneration, and regeneration: role of macrophages.

In newborn rats the levels of nerve growth factor (NGF) mRNA (mRNANGF) and NGF receptor mRNA (mRNA(rec)) in the sciatic nerve were 10 and 120 times higher, respectively, than in adult animals. mRNA(rec) levels decreased steadily from birth, approaching adult levels by the third postnatal week, whereas mRNANGF levels decreased only after the first postnatal week, although also reaching adult levels by the third week. Transection of the adult sciatic nerve resulted in a marked biphasic increase in mRNANGF with time. On the proximal side of the cut, this increase was confined to the area immediately adjacent to the cut; peripherally, a similar biphasic increase was present in all segments. mRNA(rec) levels were also markedly elevated distal to the transection site, in agreement with previous results obtained by immunological methods [Taniuchi, M., Clark, H. B. & Johnson, E. M., Jr. (1986) Proc. Natl. Acad. Sci. USA 83, 4094-4098]. Following a crush lesion (allowing regeneration), the mRNA(rec) levels were rapidly down-regulated as the regenerating nerve fibers passed through the distal segments. Down-regulation of mRNANGF also occurred during regeneration but was slower and not as extensive as that of mRNA(rec) over the time period studied. Changes in mRNANGF and mRNA(rec) occurring in vivo after transection were compared with those observed in pieces of sciatic nerve kept in culture. No difference was found for mRNA(rec). Only the initial rapid increase in mRNANGF occurred in culture, but the in vivo situation could be mimicked by the addition of activated macrophages. This reflects the situation in vivo where, after nerve lesion, macrophages infiltrate the area of the Wallerian degeneration. These results suggest that mRNANGF synthesis in sciatic non-neuronal cells is regulated by macrophages, whereas mRNA(rec) synthesis is determined by axonal contact.

Animals↗
PubMedDate not supplied

Changes in endoneurial blood flow, motor nerve conduction velocity and vascular relaxation of epineurial arterioles of the sciatic nerve in ZDF-obese diabetic rats.

BACKGROUND: We have previously reported that in streptozotocin-induced diabetic rats, reduction in endoneurial blood flow (EBF) and impairment of acetylcholine-mediated vascular relaxation of arterioles that provide circulation to the sciatic nerve precedes slowing of motor nerve conduction velocity (MNCV). However, in animal models of type 2 diabetes it is unknown whether slowing of MNCV is accompanied by vascular dysfunction. METHODS: Using ZDF-lean and ZDF-obese diabetic rats we examined whether diabetes-induced slowing in MNCV was associated with a reduction in EBF and impaired vascular relaxation in epineurial arterioles of the sciatic nerve. We measured MNCV in the sciatic nerve using a non-invasive procedure, and sciatic nerve nutritive blood flow using microelectrode polarography. In vitro videomicroscopy was employed to quantify arteriolar diameter responses to acetylcholine in arterioles overlying the sciatic nerve. RESULTS: MNCV and EBF in hyperglycemic (4-week duration) ZDF-obese diabetic rats were significantly decreased by 30% and 63%, respectively, compared to age-matched ZDF-lean rats. Acetylcholine elicited a dose-dependent dilation of epineurial vessels from ZDF-lean and ZDF-obese diabetic rats, although acetylcholine-induced dilation was significantly reduced in ZDF-obese diabetic rats. Determination of markers of oxidative stress provided ambiguous results. Superoxide levels were increased in epineurial vessels from ZDF-obese diabetic rats. Lens glutathione levels were decreased and serum thiobarbituric acid reactive substances increased in ZDF-obese diabetic rats but sciatic nerve conjugated diene and glutathione levels were not significantly different compared to ZDF-lean rats. CONCLUSIONS: Diabetes causes a reduction in EBF and impairment in vascular relaxation in epineurial vessels in ZDF-obese diabetic rats. This impaired vascular response is associated with neural dysfunction.

Animals↗
PubMed2004

The role of MAP kinases in rapid gene induction after lesioning of the rat sciatic nerve.

Lesion of the sciatic nerve caused a rapid activation of p38MAP kinase in the injured nerve adjacent to the site of transection. This activation was detectable 3 min after lesioning, increased during the next 15 min and remained high for several hours. Erk1/2 activation was also observed as early as 15 min after lesioning. Activation of these MAP kinases was seen in both the external sheaths and the endoneurium. The separation of the external sheaths from the endoneurium accelerated the p38MAP kinase activation. To evaluate whether the injury-activated MAP kinase cascades are implicated in the rapid gene induction observed after nerve lesion, experiments were performed with an ex vivo model. Segments of sciatic nerves were incubated in oxygenated Krebs-Ringer buffer. MAP kinases were activated at 15 min and remained active after 6 h. Induction of mRNA was also observed for nerve growth factor (NGF), interleukin 6 (IL-6), leukaemia inhibitory factor (LIF) and deiodinases of type 2 (D2) and type 3 (D3). Thus, the ex vivo model mimics events occurring in the animal after nerve section. Finally, nerve segments were incubated in the presence of specific inhibitors of Erk1/2 activation (U0126) and of p38MAP kinase activity (SB203580). U0126 inhibited D3, LIF and to a lesser extent NGF mRNA induction, but did not affect significantly the induction of D2 and IL-6 mRNAs. SB203580 inhibited the expression of the genes for D3 and LIF. We conclude that MAP kinase cascades, activated by nerve transection, are involved in the rapid gene induction in the nerve.

Animals↗
PubMedDate not supplied

Sensory nerve innervation of epineurial arterioles of the sciatic nerve containing calcitonin gene-related peptide: effect of streptozotocin-induced diabetes.

The authors have determined that epineurial arterioles of the sciatic nerve are innervated by nonadrenergic, noncholinergic nerves that contribute to the regulation of vasodilation. Using immunohistochemistry, the authors determined that nerves innervating epineurial arterioles contain the neuropeptide calcitonin gene-related peptide (CGRP). Using streptozotocin-induced diabetic rats, the authors demonstrated that CGRP content in sensory nerves innervating epineurial arterioles and vasodilation in response to exogenous CGRP was decreased. In summary, epineurial arterioles of the sciatic nerve are innervated by sensory nerves containing the neuropeptide CGRP. The diabetes-like condition induced by streptozotocin reduces the content of CGRP in these nerves and exogenous CGRP-mediated vasodilation. CGRP is likely an important regulator of vascular tone and compromising its function could contribute to nerve ischemia and diabetic neuropathy.

Animals↗
PubMed2000

Compensatory projection of primary nociceptors and c-fos induction in the spinal dorsal horn following neonatal sciatic nerve lesion.

The sciatic nerve was cut in newborn rats, and prevented from regenerating for 8 weeks. The number of dorsal root ganglion (DRG) neurons in L4 and L5, the distribution of central axon terminals of primary nociceptors, and the activity of secondary nociceptors were examined in the lumbar dorsal horn. The neonatal sciatic lesion caused about 60% reduction of DRG neurons. The central terminal field of the sciatic primary nociceptors negatively labeled by in situ binding of Bandeiraea simplicifolia isolectin B4 (BsIB4) markedly shriveled. Instead, the central representation of the saphenous nerve and the posterior cutaneous nerve of the thigh (PC) expanded. The laminae I/II neuropil in the medialmost (1/4) of the L3 dorsal horn and in the second lateral (1/4) around the L4/5 junction was occupied by the BsIB4 binding sites derived from the saphenous and the PC primary neurons, respectively. Noxious stimuli applied to the receptive fields of the saphenous and the PC nerves induced c-Fos-like immunoreactivity in many neurons in the expanded central terminal fields of the nerves. The collateral sprouts of uninjured primary nociceptors did not only invade the deafferented area of the dorsal horn but also established functional synaptic connections.

Afferent Pathways↗
PubMed2002

Pre-degenerated peripheral nerve extracts applied to the proximal stump of transected sciatic nerve enhance both regeneration and autotomic behavior in rats.

BACKGROUND: Peripheral nerve regeneration after traumatic injury and standard repair with a nerve autograft is often incomplete and results in neuropathic pain. Peripheral nerve extracts applied to the proximal nerve stump by means of autologous, dead-ended connective tissue chambers (deCTC) are known to accelerate the rate of axon regeneration. This study tested if such extracts would influence autotomy, which is a behavioral measure of neuropathic pain in animal models. MATERIAL/METHODS: The study was performed on Wistar rats. DeCTCs, filled with postmicrosomal fraction obtained from 7-day-predegenerated nerves (7D group) or fibrin (F group), were implanted into transected sciatic nerve. In the control group (C), sciatic nerve was transected and its distal part was removed. The self-mutilation behavior in rats was assessed daily for seven weeks after sciatic nerve transection. The onset as well as intensity of autotomy was measured. The progress of regeneration was assessed under light microscopy and histochemistry. RESULTS: The earliest onset and greatest severity of autotomy were found in the 7D group. Regeneration progress was also highest in this group. In the F group, we found weaker regeneration and less autotomy. The control group showed no regeneration, but more autotomy than the F group. CONCLUSIONS: Intensified autotomy may be the price paid for enhanced peripheral nerve regeneration after application of growth-promoting substances.

Animals↗
PubMed1985

Synthesis of myelin proteins and ultrastructural investigations in regenerating rat sciatic nerve.

Myelin protein synthesis, as well as ultrastructural and morphometric changes in regenerating peripheral nerve, was studied. Sciatic nerves of rats were crushed unilaterally; sham-operated nerves of the contralateral side served as controls. For the in vivo experiments, rats were killed at selected periods after the nerves were crushed (30, 60, 90, and 120 days); seven days prior to killing, the animals were injected intravenously with L-[4,5-3H]leucine. For the in vitro experiments, proximal and distal segments of sciatic nerve and equivalent sham-operated nerves were labeled with 3H-amino acid mixture 90 days after axotomy. Purified myelin was isolated from nerve segments; specific radioactivity and gel electrophoretic patterns of proteins were analyzed. Cross-sectional electron microscope (EM) preparations of proximal, distal, and contralateral segments of nerves also were examined. Results showed that the incorporation of labeled amino acids into total myelin proteins was enhanced significantly in the distal segment of sciatic nerves at all of the periods of regeneration studied. The yield of myelin protein per mm distal nerve segment increased as regeneration proceeded. The remyelination of fibers early after nerve crush was weak, whereas it gradually attained the normal range 90-120 days after axotomy. Morphometric analysis of myelin sheath thickness of regenerating axons was consistent with the data obtained for myelin protein synthesis.

Animals↗
PubMed1995

Relation between functional deficit and intraneural local anesthetic during peripheral nerve block. A study in the rat sciatic nerve.

BACKGROUND: During peripheral nerve block, local anesthetic (LA) penetrates within and along the nerve to produce the observed functional deficits. Although much is known about the kinetics and steady-state relation for LA inhibition of impulse activity in vitro in isolated nerve, little is known about the relation between functional loss and intraneural LA content in vivo. This study was undertaken to investigate the relation of functional change to intraneural LA. METHODS: A sciatic nerve block was performed in rats with 0.1 ml 1% lidocaine radiolabeled with 14C. The total intraneural uptake of LA was determined at different times after injection, and the distribution of lidocaine along the nerve was assayed at different stages of functional block. Drug content was also compared with equilibrium lidocaine uptake in the isolated rat sciatic nerve. RESULTS: Total intraneural lidocaine in vivo increased to near steady-state in about 3 min, stabilizing at approximately 14.3 nmol/mg wet tissue for about 12 min before decreasing to zero at 70 min after injection. Although intraneural lidocaine was 1.6% of the injected dose during full block, only 0.3% was left when deep pain sensation returned and 0.065% was still detected when functions fully recovered. Despite these large differences in total lidocaine content, the longitudinal distribution remained constant. Intraneural lidocaine concentrations obtained at full block and partial recovery could be achieved in vitro by equilibration in 0.7-0.9 and 0.2-0.3 mM lidocaine, respectively. CONCLUSIONS: During peripheral nerve block only a small amount of injected LA penetrates into the nerve. The intraneural content of LA correlates with the depth of functional block.

Animals↗
PubMed1997

Ciliary neurotrophic factor immunoreactivity in rat intramuscular nerve during reinnervation through a silicone tube after severing of the rat sciatic nerve.

The immunoreactivity of ciliary neurotrophic factor (CNTF) and S100 was studied in the degenerating and regenerating intramuscular nerves after the sciatic nerve was severed. The sciatic nerves of male Wistar rats were transected at the midpoint of the thigh, and silicone tubing was used to obtain effective reinnervation. The strong immunoreactivity of CNTF and S100 was observed in the Schwann cell cytoplasm of intramuscular nerves (IMN) and at the neuromuscular junction (NMJ) on the control sections. The CNTF immunoreactivity gradually became weak and indistinct in the Schwann cell cytoplasm after the operation. However, it was recognized again in the IMN at 4 weeks after the operation. On the other hand, the S100 immunoreactivity was continuously observed except at the NMJ through the denervating and reinnervating period. At 12 weeks after the operation, the strong immunoreactivity of both CNTF and S100 was observed again. These findings suggest that the amount of CNTF protein decreased in Schwann cells of the IMN and NMJ during the denervating period and increased during the reinnervating period in proportion to the number of remyelinated Schwann cells after severing of the sciatic nerve. They also suggest that CNTF was more highly correlated than the S100 protein with the reinnervation activity of Schwann cells.

Animals↗
PubMed1998

[Functional characteristics of foot skin mechanoreceptors and afferent nerve fibers of the sciatic nerve after central axotomy of sensory neurons].

The activity of mechanoreceptors was studied in normal rats' hindfoot and compared with that of rhizotomised animals. Evoked nerve impulses were recorded from afferent fibres of the n.tibialis. A possible autonomous functioning of decentralised mechanoreceptors, even though in an altered fashion, was shown. The registered shifts comprised a decrease in sensitivity to mechanical stimulation and lower adaptive properties. The findings suggest that the underlying mechanism involves a probable lack of trophic interaction leading to interruption of a link between the CNS and the peripheral nervous system.

Afferent Pathways↗
PubMed1985

Regulation of myelination: axons not required for the biosynthesis of basal levels of the major myelin glycoprotein by Schwann cells in denervated distal segments of the adult cat sciatic nerve.

The adult cat sciatic nerve was examined for Schwann cell biosynthesis of the major myelin glycoprotein (P0) in the distal segments after permanent nerve transection, where there is no axonal regeneration or myelin assembly. Endoneurial slices (intrafascicular tissue) from the distal segment of the desheathed cat sciatic nerves at 10 wk after transection and from normal adult desheathed brachial nerves were incubated with radioactive mannose; [3H]mannose incorporation into P0 was observed by fluorography after sodium dodecyl sulphate-pore gradient electrophoresis (SDS-PGE). Analysis of immune precipitates by SDS-PGE after incubation of an aliquot of an endoneurial fraction with rabbit antichick P0 gamma globulin verified that the [3H]mannose-labeled glycoprotein was P0. The level of incorporation of [3H]mannose into P0 and into other endoneurial glycoproteins in the normal brachial nerve from the adult cat was at substantially reduced levels compared with the transected nerve. Such incorporation was detectable by fluorography only after prolonged exposure to X-ray film (15 days). As a result, the level of biosynthesis of P0 in the normal adult cat is substantially reduced, suggesting that the extent of active myelination in the adult cat nerve is at a low level. Furthermore, Schwann cells are capable of continued synthesis of P0 in the adult, permanently transected nerve in the absence of axonal influence, suggesting that axonal association is not an absolute requirement for specifying myelin protein synthesis.

Animals↗