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At least 127 records · Page 7Linked to original sources
PubMed2001

Increased phosphorylation of cyclic AMP response element-binding protein (CREB) in the superficial dorsal horn neurons following partial sciatic nerve ligation.

Partial sciatic nerve injury causes neuropathic pain associated with behavioral changes such as spontaneous pain, hyperalgesia and allodynia. Both central and peripheral sensitization of pain pathways are likely to be involved in these alterations. Nerve injury induced plastic changes in the dorsal horn, where the second relay nociceptive neurons are located, may contribute to the central sensitization process. It is thus important to establish the intracellular events through which a partial nerve injury can induce plasticity leading to neuropathic pain. In this study, we investigated whether partial sciatic nerve ligation (PSNL), a well-characterized neuropathic pain model, is able to induce the phosphorylation of a transcription factor, known as the cyclic AMP response element-binding protein (CREB) which is believed to be involved in the transcriptional regulation of many genes. Using immunocytochemistry, we found that 3 weeks following PSNL, the number of phosphorylated (p) CREB-IR cells was significantly increased in the injured side dorsal horn of rats, particularly in the superficial laminae. Interestingly, the majority of pCREB-IR cells expressed protein kinase Cgamma, an enzyme shown to be involved in the development of neuropathic pain in PSNL model. Taken together, these results suggest that increased CREB phosphorylation induced by PSNL may be one of the key molecular events leading to synaptic alterations and persistent pain in the PSNL model of neuropathic pain.

Animals↗
PubMedDate not supplied

[Possibility of nerve lesions related to peripheral nerve blocks. A study of the human sciatic nerve using different needles].

UNLABELLED: When a needle tip comes too close to a nerve axon, the mechanical effect over the nerve membrane produces paresthesia. We examined the hypothetical mechanical damage of short bevel and long bevel needles over sciatic nerve bundles under scanning electron microscopy. METHODS: We obtained samples of sciatic nerve from three patients of 68, 74 and 76 years old. These samples were fixed, dehydrated and coated with gold microfilm for their observation under scanning electron microscopy. Ten short bevel needles and ten long bevel needles were studied under the same microscopic technique. We interpolated microscopic images from sciatic nerve samples and different needle bevels at various angles to study the mechanical damage of these needles to nerve axons. RESULTS: Sciatic nerve bundles were found 0.1 to 0.2 mm deep in the samples; information was given about the bevel length and angle of needles. The damage is perceptible under scanning electron microscopy, when the needle bevel is introduced 0.3-0.4 mm deep into the nerve bundle; here, the needle tip cuts through the perineurum, piercing the nerve bundle. At a depth of 1 mm, the lesion caused by short bevel needles is greater than that caused by long bevel needles. The type of epineural lesions caused by short bevel needles is also different from the ones caused by long bevel needles. CONCLUSIONS: Lesions that affect superficially the epineurum can cause paresthesia by compression of nerve fascicles without damaging the axons. If the perineurm is damaged, the lession will also affect the blood-nerve barrier, leading probably to posterior sequels.

Aged↗
PubMed1995

Exogenous NT-3 mitigates the transganglionic neuropeptide Y response to sciatic nerve injury.

Peripheral sciatic nerve transection injury produces a marked increase in immunoreactive NPY in rat lumbar DRG and, as a 'transganglionic' response, in their central axonal projections to the dorsal spinal cord and gracile nuclei. Local application of neurotrophin-3 (NT-3) using implanted silicone chambers applied to the proximal transected sciatic nerve stump significantly diminished the transganglionic NPY response in the gracile nucleus and spinal cord but did not affect the CGRP transganglionic response. Conversely, local application of NGF affected the transganglionic CGRP response to axotomy but did not substantially affect transganglionic gracile NPY upregulation.

Animals↗
PubMed1989

Neurotropism to tissue specificity in nerve regeneration. Experimental study on sciatic nerves of rat.

Using the left sciatic nerves of 44 rats we studied neurotropism in nerve regeneration. The proximal and distal cut ends of the nerves were separately introduced into the ends of a specially designed silastic Y- or cross-shaped tube. Either the distal stump or a cut end of the Achilles tendon was inserted into the other ends of the tube, or was left empty. The distance between the tissue ends, nerve-to-nerve or nerve-to-tendon, was 4 mm. Four weeks later, neurofibers sprung out from the proximal stump and grew towards the distal nerve end instead of the tendon end or the vacant channel of the tube. This finding suggests that neurotropic factors may influence the direction of growth of the newly formed neurofibers. This paper discusses the mechanism of neurotropism, the effect of the distance between the cut ends of the nerve, and the choice of the silastic material.

Achilles Tendon↗
PubMed2001

Expression of Schwann cell-specific proteins and low-molecular-weight neurofilament protein during regeneration of sciatic nerve treated with neurotrophin-4.

Neurotrophin-4 acts as a potent survival factor for subpopulations of motoneurons. To investigate its effect on Schwann cell sheath and axonal proteins during peripheral nerve regeneration, sciatic nerves in adult rats were transected and repaired, and fibrin glue containing neurotrophin-4 injected around the repair site. At 5, 15, 30 and 60 days after repair, 5-mm nerve segments distal to the repair were collected, and western blotting was used to measure myelin-associated glycoprotein, myelin basic protein and low-molecular-weight neurofilament protein. In control groups these dramatically declined at 5 and 15 days then increased from 30 and 60 days. However, in the neurotrophin-4 group there was a significant increase (to several times basal values) in myelin-associated glycoprotein and myelin basic protein at 5-15 days. The relatively small increases (<7%) in Schwann cell numbers suggest that this is mainly due to increased synthesis per cell. The neurotrophin-4 group also showed a small but significant increase at 15 days in low-molecular-weight neurofilament protein, which however remained much lower than basal. We conclude that neurotrophin-4 regulates the expression of myelin-associated glycoprotein, myelin basic protein, and to a lesser extent low-molecular-weight neurofilament protein, during peripheral nerve regeneration.

Animals↗
PubMed1997

Effects of 2.5 s mouse nerve growth factor on regeneration of injured sciatic nerves in mice and rats.

AIM: To study the promoting activity of 2.5 s murine nerve growth factor (NGF) for the regeneration of injuried sciatic nerve. METHODS: The sciatic nerves of mice and rats were crushed. The axon counts and differential axon counts were made. Evoked potential latency (NMEPL) was recorded at sites of proximal (Pro) and distal (Dis) segment of soleus muscles. RESULTS: In mice, NGF im 0.5-1 kBU.kg-1 increased the axon counts of regenerated nerves 20 d after crush; 2-4 kBU.kg-1 simultaneously alleviated the denervated atrophy of soleus muscles. In rats, NGF i.m. increased the axon counts at dose of 1 kBU.kg-1 for 40 d, 2 kBU.kg-1 for 30 d and 40 d, and 4 kBU.kg-1 for 20 d, 30 d and 40 d after crush; the number of large axons of regenerated nerves were also increased by NGF i.m. 2 kBU.kg-1 for 40 d and 4 kBU.kg-1 for 30 d and 40 d; Pro NMEPL was shortened by NGF 1, 2, and 4 kBU.kg-1, Dis-NMEPL was shortened by NGF 2 and 4 kBU.kg-1 for 40 d. CONCLUSION: NGF im evidently promotes the regeneration of injuried sciatic nerve, and attenuates the skeletal muscular atrophy caused by nerve injury.

Animals↗
PubMed1992

An experimental painful peripheral neuropathy due to nerve constriction. I. Axonal pathology in the sciatic nerve.

A constriction injury to the sciatic nerve of the rat produces a painful peripheral neuropathy that is similar to the conditions seen in man. The pathology of the sciatic nerve in these animals was examined at 10 days postinjury, when the abnormal pain sensations are near maximal severity. The nerves were examined with (1) complete series of silver-stained longitudinal sections of pieces of the nerve (3 cm or more) that contained the constriction injury in the center, (2) toluidine blue-stained semithin sections taken at least 1 cm proximal and 1 cm distal to the constriction, and (3) EM sections taken adjacent to those stained with toluidine blue. One centimeter or more proximal to the constriction, both myelinated and unmyelinated axons were all normal. Nearer to the constriction, extensive degeneration of myelinated axons became increasingly common, as did signs of endoneurial edema. Distal to the constriction, the nerve was uniformly edematous and full of myelinic degeneration. There was a profound loss of large myelinated axons and a distinctly less severe loss of small myelinated and unmyelinated axons. These observations show that at 10 days postinjury the constriction produces a partial and differential deafferentation of the sciatic nerve's territory. The absence of degeneration in the nerve 1 cm proximal to the constriction indicates the survival of the primary afferent neurons whose axons are interrupted.

Animals↗
PubMed2004

The influence of motor axon misdirection on muscle contraction force in early nerve repair in a rat sciatic nerve model.

We examined the influence of misdirection of regenerating motor axons toward the distal sensory Schwann tubes on the muscle contraction force in early nerve repair using a rat sciatic nerve model. At 0, 1, 2, 4 and 8 weeks after severing the tibial, peroneal and sural nerves, the proximal stump of the tibial nerve was anastomosed with the distal stumps of both the peroneal and sural nerves using tubulisation (n=10 in each of five groups). We intentionally used the distal stump of the sural nerve (a sensory nerve) to induce regeneration in motor axons from the proximal tibial nerve stump toward the distal sensory nerve stump. Twenty-four weeks after nerve repair, isometric contraction force and wet weight of the anterior tibial muscle were measured, and the numbers of regenerated myelinated axons (motor and sensory) in the distal sural and peroneal nerves were counted. The rates of sural nerve regeneration were significantly higher at weeks 0 and 1 than at the later repair times. However, muscle contraction force and muscle wet weight did not differ significantly between groups in which nerves were repaired within four weeks of severance. These results indicate that peripheral nerve repair within four weeks of severance does not influence the muscle contraction force of single muscle despite the misdirection of motor axons toward the distal sensory Schwann tubes.

Anastomosis, Surgical↗
PubMed2001

Detection of E-cadherin expression after nerve repair in a rat sciatic nerve model.

The authors investigated E-cadherin expression during nerve regeneration after nerve suture using the rat sciatic nerve model. Five rats were used during each postoperative period. E-cadherin expression was detected by Western blot analysis and immunofluorescent staining with an anti-E-cadherin monoclonal antibody. The level of E-cadherin expression was calculated as the amount relative to that found in normal control nerve. The level of E-cadherin expression was decreased at first, and then gradually increased. The maximum level of E-cadherin was 1.92 +/- 0.07 fold in the sutured nerve. The level of E-cadherin expression in the sutured nerve was significantly greater (p < 0.0001) than that of the normal control nerve from postoperative day 3 to 21, and that of sutured nerve returned to the control level by postoperative day 28. The immunofluorescent staining results indicated that E-cadherin expression was almost negative or decreased immediately after the operation, but the degree of expression increased gradually in Schwann's cells. The degree of E-cadherin expression was significantly greater than that of normal control nerves from postoperative day 7 to 14, and returned to the control level by postoperative day 21. These results demonstrate that E-cadherin expression increases during nerve regeneration, and the expression was observed mainly in Schwann's cells. The degree of E-cadherin expression may affect the rate of nerve regeneration.

Animals↗
PubMed1987

Scanning electron microscopic studies of the myelinated nerve fibres of the mouse sciatic nerve with special reference to the Schwann cell cytoplasmic network external to the myelin sheath.

The three-dimensional morphology of the surface of myelinated nerve fibres in the mouse sciatic nerve was studied by scanning electron microscopy after combined potassium hydroxide treatment and collagenase digestion (to remove the surrounding collagen fibrils and basal laminae from nerve fibres) as well as by transmission electron microscopy. The myelinated nerve fibre appeared as a long cylinder with sporadic annular constrictions corresponding to the nodes of Ranvier. Slight swellings of the surface due to Schwann cell nuclei were usually found at the middle of each internode. The surface of the nerve fibre clearly exhibited a network of bulges, which consisted of longitudinal bands extending from the nuclear swelling to the nodes of Ranvier through the internode, and transverse trabeculae bridging between these longitudinal bands. These bulges on the surface of nerve fibres were the site of the retained Schwann cell cytoplasm external to the myelin lamellae. These cytoplasmic networks on myelinated fibres presumably corresponded to the networks described by Cajal following silver impregnation. In addition, other thin elevations and focal round swellings were also found associated with these longitudinal bands and transverse trabeculae. These networks of Schwann cell cytoplasm are considered to be cytoplasmic channels for nutrition. The two apposing paranodal bulbs of nodes of Ranvier were often asymmetrical in their structure. The networks of the paranodal region were more complicated than those in the internode. The networks of Schwann cell cytoplasm converged into a continuous circumferential collar toward the node, which in turn gave rise to finger-like projections into the nodal gap.

Animals↗
PubMed1988

Calcium transfer at the blood-nerve barrier of the frog sciatic nerve.

Calcium transfer across the blood-nerve barrier of the frog sciatic nerve was studied using an in situ perfusion technique and an in vivo i.v. bolus injection technique. The permeability-surface area product of 45Ca at the blood-nerve barrier, (PA)BNB, calculated from radioactivity in the desheathed nerve segment after 5 min of circulation of tracer, and corrected for the residual radioactivity in the blood space, equaled 4.4 +/- 0.4 (S.E.M.) X 10(-5) ml.s-1.g-1 wet wt. The (PA)BNB of 45Ca was independent of [Ca2+] in the perfusion medium between 0.18 and 18 mM. The permeability-surface area products of 45Ca across the perineurium [(PA)per] also was measured by an in situ incubation technique, and equaled 1.45 +/- 0.41 X 10(-5) ml.s-1.g-1 wet wt. (n = 8). The half time (t 1/2) for nerve calcium to equilibrate with plasma calcium was calculated to be 60 min. The low, passive permeability to calcium of the blood-nerve barrier probably limits marked calcium concentration changes in nerve endoneurium following transient changes of plasma calcium, but should not alter steady-state responses.

Animals↗
PubMed1988

Nerve sheath tumors of the sciatic nerve and sacral plexus.

Eight patients with sciatic nerve and sacral plexus nerve sheath tumors, seen at Louisiana State University Medical Center in Shreveport, are presented. These cases illustrate the broad spectrum of pathology and modes of presentation of patients with nerve sheath tumors in this region. Patients can be divided into 4 groups. Group I includes subgluteal and/or thigh lesions with a well-defined mass on CT. Group II patients have neuroforaminal enlargement (defined by CT) and usually have radicular leg pain. Patients in group III have intrapelvic tumors with extension into the thigh. They usually have a poorly defined mass on CT. Group IV includes patients that have an intrapelvic mass (usually well defined) with radicular leg pain and/or mass effect. CT scanning proved to be the diagnostic procedure of choice. It delineated the location and extent of the tumor and thus was important in determining resectability. The variable course of these tumors is emphasized. A conservative nonoperative approach should be considered in asymptomatic and/or neurologically stable patients.

Adult↗
PubMed2003

Loss and recovery of the blood-nerve barrier in the rat sciatic nerve after crush injury are associated with expression of intercellular junctional proteins.

The blood-nerve barrier in peripheral nerves is important for maintaining the environment for axons. Breakdown of the barrier by nerve injury causes various pathologies. We hypothesized that the breakdown and recovery of the blood-nerve barrier after injury are associated with the changes in the expression of intercellular junctional proteins. To test this hypothesis, we induced crush injuries in the rat sciatic nerve by ligation and analyzed spatiotemporal changes of claudin-1, claudin-5, occludin, VE-cadherin, and connexin43 by immunoconfocal microscopy and morphometry and compared them with changes in the permeability of the blood-nerve barrier by intravenous and local administration of Evans blue-albumin (EBA). On day 1 after removal of the ligature EBA leaked into the connective tissue in the endoneurium and then the leakage gradually decreased and disappeared on day 7. On day 1 claudin-1, claudin-5, occludin, VE-cadherin, and connexin43 had totally disappeared from the perineurium and endoneurium. Thereafter, claudin-1, claudin-5, occludin, and VE-cadherin recovered from day 2, whereas connexin43 was redetected on day 5. These results indicate that the breakdown and following recovery of the blood-nerve barrier are closely associated with changes in the expression of claudins, occludin, VE-cadherin, and connexin43 and that the recovery time course is similar but nonidentical.

Animals↗
PubMed1991

Histological assessment of nerve lesions caused by epineurial electrode application in rat sciatic nerve.

The left sciatic nerve of 36 rats was exposed and four ring-shaped stainless steel wire electrodes were sutured to the epineurium of each nerve in the same manner as performed clinically for "carousel stimulation" in man. The rats were sacrificed 10 days (Group 1), 3 weeks (Group 2), or 3 months (Group 3) after implantation. The electrodes were excised, the nerves were embedded in Epon, and semithin sections were obtained for histological and planimetric assessment of lesions caused by the epineurially sutured electrodes. The right sciatic nerves served as controls. The total area of neural tissue within the perineurium was determined at three levels: at the site of the electrodes, 8 mm proximal, and 8 mm distal. The area of neural tissue damaged by the surgical procedure was expressed as a percentage of the total area. In Group 1, nine of 12 nerves showed lesions ranging from 0.39% to 25.39% of the total area of neural tissue, in Group 2 eight of 11 sciatic nerves showed lesions ranging from 0.24% to 13.03% of the total area, and in Group 3 five of 12 nerves showed lesions ranging from 0.21% to 4.96% of the total area. The pathologically altered areas in Groups 2 and 3 exhibited distinct signs of nerve fiber regeneration. The reasons for the decrease in damage from Group 1 to Group 3 and the clinical implications of the results for long-term electrical stimulation are discussed.

Animals↗