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Isolation and characterization of neonatal Schwann cells from cryopreserved rat sciatic nerves.

Much of our knowledge about the development and maintenance of the peripheral nervous system has been learned through studying the interaction of neurons, or their isolated membranes, with Schwann cells (SC), in tissue culture. Numerous approaches have been employed to obtain an adequate quantity of SC, but all have been limited by either the uncertainty of obtaining a sufficient amount of starting material, the time and expertise required to isolate the SC, or by the limited number of SC that can be generated. We have developed a procedure to isolate SC from cryopreserved sciatic nerves. This procedure allows for sciatic nerves to be pooled until adequate numbers of nerves are obtained, yet still produces cells that retain the functional abilities of SC isolated from fresh nerves. Sciatic nerves were isolated from 2 day old rat pups, placed in either DME media and used fresh or placed in a freezing solution containing DME media (25%), DMSO (25%), fetal calf serum (50%), frozen at -70 degrees C and stored in liquid nitrogen. The frozen nerves were rapidly thawed to 37 degrees C and single cells were prepared from both fresh and frozen nerves using enzymatic and mechanical disruption as previously described (Brockes et al., Brain Res 165: 105-118, 1979). Comparable cell yields were obtained for SC isolated from both frozen and fresh nerves. Immunohistochemical staining of both fresh and frozen SC produced similar staining patterns with antibodies to GFAP, laminin, CNPase, S100, MBP, and P0 protein. Addition of axolemmal enriched membrane fractions to both the frozen and fresh SC gave a similar dose response curve of 3H-thymidine incorporation, with SC from frozen sciatic nerves responding even better than fresh sciatic nerves at higher doses (50 micrograms and 100 micrograms of protein/ml). As demonstrated by the cell yield, immunohistochemical staining and responses to axolemmal mitogens, this procedure produces SC from frozen sciatic nerves with similar characteristics to those isolated from fresh nerves. This procedure will allow the production and utilization of a large number of SC, which will be critical in further studies on the development and maintenance of the peripheral nervous system.

Animals↗

Sciatic nerve stimulation induces hypotension but not renal or lumbar sympathoinhibition in hypertensive Dahl rats.

Sustained reductions in arterial pressure and sympathetic nerve activity occur after prolonged sciatic nerve stimulation in spontaneously hypertensive and pre-hypertensive Dahl salt-sensitive rats whereas these responses are not observed in renal hypertensive or Dahl resistant rats. These observations suggest that the development of post-stimulation hypotension and sympathoinhibition may be related to the genetic predisposition for hypertension rather than to the increased level of arterial pressure. However, it is not known whether the magnitude of the post-stimulation blood pressure and sympathetic nerve responses are influenced by the increased level of arterial pressure in addition to the genetic predisposition to hypertension. In the present study, we sought to determine if sustained sciatic nerve stimulation induces post-stimulation hypotension in hypertensive Dahl sensitive (DS) rats. For this purpose, mean arterial pressure (MAP), heart rate (HR), renal (RSNA) and lumbar (LSNA) sympathetic nerve activity were recorded during and after sciatic nerve stimulation in hypertensive DS rats (n = 17) fed an 8.0% NaCl diet for 7-8 weeks. Sciatic nerve stimulation increased HR (control, 443 +/- 10 b.p.m.; stimulation, 487 +/- 8 b.p.m.; p < 0.05) and tended to increase MAP, RSNA and LSNA. Two hours after stimulation, MAP was reduced (control 145 +/- 5 mmHg; recovery, 124 +/- 8 mmHg; p < 0.01) from control values. In contrast, RSNA and HR remained unchanged whereas LSNA was increased (69 +/- 20%; p < 0.05) from control values 120 min after stimulation. MAP, HR and RSNA were unchanged from control values during and for 2 h after sham stimulation in eight DS rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Afferent Pathways↗

Functional projection of regenerated rat sural nerve axons to the hindpaw skin after sciatic nerve lesions.

The functional regeneration of polymodal C-fibers and low-threshold mechanoreceptive axons in the rat sural nerve was evaluated 3 months after a sciatic nerve crush lesion or neurotomy and suture. The distribution of polymodal C-fibers was tested through stimulation-induced extravasation of Evans blue albumin in the foot skin. As judged from the area of stained skin, the polymodal sural C-fibers regenerated efficiently after both lesion types. In regenerates, though, the borders of the stained domain were less clearly defined than in controls, and there were minor territorial abnormalities. The Evans blue-stained area on the unoperated side in neurotomy/suture cases was significantly smaller than in normal control animals. The area covered by low-threshold mechanoreceptors in the foot skin was tested through gentle mechanical stimulation with a blunt probe and electrophysiological recording from the sural nerve. In regenerates the foot skin area covered by functional low-threshold mechanoreceptors turned out to be reduced on the operated side compared to controls, particularly after neurotomy/suture. We conclude that sural nerve regeneration is accompanied by a spatially more complete reestablishment of functional C-fiber-related cutaneous polymodal nociceptors than of functional cutaneous low-threshold mechanoreceptors.

Animals↗

Appearance of myelin proteins in rat sciatic nerve during development.

Rats between 5 and 45 days of age were sacrificed and their sciatic nerves dissected. Myelin was prepared from these sciatic nerves by a procedure involving purification on discontinuous sucrose gradients. The proteins of whole sciatic nerves at different ages and the proteins derived from the myelin isolated from these sciatic nerves were examined by discontinuous polyacrylamide gel electrophoresis in buffers containing sodium dodecyl sulfate. Over half of the proteins of sciatic nerve myelin migrated in a single band on the gel (P0). There were only minor changes in the protein distribution of sciatic nerve mylein during development. In contrast, the polyacrylamide gel patterns of whole sciatic nerve homogenate changed markedly during development between 5 and 15 days of age. The amount of P0 protein as a proportion of the total sciatic nerve protein increased from 3% at 5 days of age to 13% at 15 days of age after which it remained constant. Several other proteins which were also characteristic of the isolated myelin increased in relative importance during this time period. Parallel experiments dealing with a metabolic parameter of myelinogenesis, incorporation of intraperitoneally injected [35S]sulfate into sulfatide, were conducted. The maximum synthesis of sulfatide occurred between 6 and 16 days of age, coincident with the marked accumulation of myelin proteins in sciatic nerve.

Age Factors↗

The effects of low level laser treatment on recovery of nerve conduction and motor function after compression injury in the rat sciatic nerve.

An animal study is presented examining the effect of low level laser (LLL) treatment on nerve regeneration following axonotmesis. Twenty animals received a standardised injury to the right sciatic nerve using a time, load and length sequence (10 min, 150 N, 5 mm) known to cause extensive axonal degeneration of the rat sciatic nerve. The LLL treatment was administered using a hand-held laser probe in light contact with the skin on the dorsal aspect of the hind leg overlying the site of the axonotmesis injury to the sciatic nerve. A group of 10 animals were treated with 6J of LLL (GaAlAs 830 nm) daily for a period of 28 d. Ten more animals were treated daily with a sham exposure setting and served as controls. Nerve function was assessed by a recognised method of walking tract print analysis; the "Sciatic Functional Index" (SFI), and nerve regeneration was assessed by recording the evoked compound action potentials (cAP) in the common peroneal nerve. At 21 d post-injury, the laser-treated group had a significantly lower median SFI than the sham laser-treated group, indicating that the real laser treatment had improved functional recovery in the nerve. However, no differences were found between the evoked cAP parameters that were measured in the laser-treated and sham laser-treated groups. Histological examination reiterated the lack of difference between the two groups. Consequently, the effects of LLL on recovery must have occurred more peripherally to the point measured.

Animals↗

Insulin-like growth factor I promotes nerve regeneration: an experimental study on rat sciatic nerve.

Insulin-like growth factor I (IGF-I; somatomedin C) has previously been demonstrated, with immunohistochemical methods, to accumulate locally at the site of trauma of an injured peripheral nerve. In the experiments reported here a Y-shaped silicone-chamber system was used to test if local infusion of IGF-I had supportive effects on nerve regeneration. The proximal end of a cut sciatic nerve was inserted into one channel of the Y-shaped chamber and the length and growth direction of the regenerating myelinated axons were evaluated after 1 month. When IGF-I (250 micrograms/ml 0.5 microliters/h) was infused into one channel by an osmotic pump, the length of the regenerating axons increased significantly compared to the control groups with no IGF-I added. In some instances the regenerating axons grew towards the osmotic pump. It is concluded that local infusion of IGF-I at appropriate concentration promotes regeneration of a peripheral nerve. It exerts a neuronotrophic but not a clear chemotactic effect.

Animals↗

Evidence for asymmetric distribution of sciatic nerve endometriosis.

OBJECTIVE: To investigate if a lateral asymmetry exists in the distribution of endometriotic lesions of the sciatic nerve. DATA SOURCES: All articles on sciatic nerve endometriosis identified by MEDLINE and EMBASE database searches were retrieved, and additional reports were collected by systematically reviewing all references. Monographs on endometriosis published in the last 15 years were consulted. METHODS OF STUDY SELECTION: We considered articles in which the presence of an endometriotic lesion of the sciatic nerve and the affected side were assessed. We also included reports lacking histological examination of sciatic nerve specimens but with a surgical diagnosis of pelvic endometriosis. Two authors abstracted data independently on standardized forms. The number of women and the side of the lesion were obtained from individual studies, and the combined frequency of left- and right-side sciatic nerve endometriosis in published reports was computed. TABULATION, INTEGRATION, AND RESULTS: Thirty-two reports including 63 subjects were selected. Endometriosis of the sciatic nerve was on the right side in 41 patients, on the left in 20, and bilateral in two. Considering only patients with unilateral sciatic nerve endometriosis, the observed proportion of right-side lesions (41 of 61 [67.2%]; 95% confidence interval 54.0%, 78.7%) significantly differed from the expected proportion of 50% (chi(2)(1) 7.23, P =.007). Among the 16 cases of histological demonstration of endometriosis infiltrating sciatic nerve roots or fibers, ten had it on the right side (62.5%) and six on the left. Twenty-six of the 38 subjects (68.4%) with surgical demonstration of pelvic endometriosis but without histopathologic evidence of direct sciatic nerve involvement were affected by right cyclic sciatica. CONCLUSION: The finding that two thirds of patients with sciatic nerve endometriosis had right-side lesions constitutes further evidence against the coelomic metaplasia theory. The interposition of the sigmoid colon between the regurgitated endometrial cells implanted on the left posterolateral pelvic peritoneum seems to protect the left lumbosacral plexus and sciatic nerve.

Adolescent↗

Peripheral nerve pathological findings in familial amyloid polyneuropathy: a correlative study of proximal sciatic nerve and sural nerve lesions.

To analyze the peripheral nerve pathological abnormalities in familial amyloid polyneuropathy, a correlative pathological study was carried out on the spinal nerve roots, proximal sciatic nerves, sural nerves, and brachial plexuses from 3 patients with the disease in Japan. The spinal nerve roots appeared to be unaffected except for amyloid deposition on the epineurium. In sciatic nerves and brachial plexuses the nerve lesions had a multifocal distribution, showing prominent interstitial edema in the endoneurium frequently adjacent to deposits of amyloid; in these regions the nerve fibers were severely depleted. A teased-fiber study revealed that segmental demyelination was the predominant type of nerve fiber abnormality. However, these findings were not seen in the sural nerves; instead a diffuse fiber loss with axonal degeneration was observed. It is suggested that multifocal lesions in the proximal portions of the long extremity nerves could summate distally to produce a symmetrical polyneuropathy in the disease. In addition to a space-occupying effect of amyloid deposits in the endoneurium, severe endoneurial edema associated with amyloid deposition in blood vessels and the endoneurial interstitium may induce ischemia in nerve fibers, thus causing the progressive polyneuropathy in this disorder.

Adult↗

Sciatic nerve palsy following hip surgery.

Sciatic nerve palsy following hip surgery is a rare but troublesome complication. Twenty cases of incomplete sciatic nerve lesions are presented and recommendations are made to prevent this potentially incapacitating lesion.

Causalgia↗

Biosynthesis of long-chain alcohols by developing and regenerating rat sciatic nerve.

Cell-free preparations of rat sciatic nerve were found to catalyze the reduction of fatty acid to alcohol in the presence of NADPH as reducing cofactor. The reductase was membrane-bound and associated primarily with the microsomal fraction. When fatty acid was the substrate, ATP, coenzyme A (CoA), and Mg2+ were required, indicating the formation of acyl CoA prior to reduction. When acyl CoA was used as substrate, the presence of albumin was required to inhibit acyl CoA hydrolase activity. Fatty acid reductase activity was highest with palmitic and stearic acids, and somewhat lower with lauric and myristic acids. It was inhibited by sulfhydryl reagents, indicating the participation of thiol groups in the reduction. Only traces of long-chain aldehyde could be detected or trapped as semicarbazone. Fatty acid reductase activity in rat sciatic nerve was highest between the second and tenth days after birth and decreased substantially thereafter. Microsomal preparations of sciatic nerve from 10-day-old rats exhibited about four times higher fatty acid reductase activity than brain or spinal cord microsomes from the same animals. Wallerian degeneration and regeneration of adult rat sciatic nerve resulted in enhanced fatty acid reductase activity, which reached a maximum at about 12 days after crush injury.

Aging↗

Alteration of phosphoinositide metabolism, protein phosphorylation, and carbohydrate levels in sciatic nerve from Wistar fatty diabetic rats.

Sciatic nerve from the Wistar fatty diabetic (FD) rat, a prospective model for non-insulin-dependent diabetes mellitus, was investigated to determine the content of carbohydrates and to measure the incorporation of 32P into phosphoinositides and proteins. This strain has been shown to develop structural abnormalities in nerves and to exhibit reduced conduction velocity. Males became diabetic between the ages of 8 and 10 wk and were maintained together with lean sibling controls until the animals were either 22 or 44 wk old. Throughout this period, FD rats displayed moderate hyperglycemia. The carbohydrate profile of FD rat sciatic nerve exhibited modest increases in glucose, fructose, and sorbitol levels and significantly reduced myo-inositol concentrations, which were comparable at both ages. When nerves from 22-wk-old animals were incubated with [32P]orthophosphate and incorporation of radioactivity into phospholipids was measured, an increase in isotope uptake into phosphatidylinositol-4,5-bisphosphate and phosphatidylinositol-4-phosphate in the distal portions of tissue from the FD rat was observed. This effect was more pronounced in nerves from 44-wk-old rats. Phosphorylation of the major myelin protein P0 was 70% higher in the most distal portion of FD sciatic nerve from 22-wk-old animals. A comparable rise in phosphorylation of P0 as well as the large (P1) and small (Pr) myelin basic proteins occurred in nerves from 44-wk-old rats. In these animals, an approximately 50% decrease in the uptake of 32P into P0 and P1 in the most proximal region of FD nerve was also apparent.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

[Neurotropism to tissue specificity in nerve regeneration: an experimental study on the sciatic nerves of the rat].

A study of neurotropism in nerve regeneration was carried out on 44 rats, using their left sciatic nerves severed to work up. The cut ends of proximal and distal stumps were separately introduced into amend of the specially designed silastic tube of Y- or cross-shape. Into the other ends of the tube were inserted either the end of the distal stump or a cut end of achilis tendon on the same side, or were left empty. The distance between the tissue ends, nerve-to-nerve or nerve-to-tendon, was 4 mm. Four weeks later, it was found in the specimens that the growth of neurofibers sprung out from the end of the proximal stump directed towards the distal nerve stump rather than towards the tendon end or the vacant limb of the tube. This fact strongly speaks for that there is some thing neurotropic factor, guiding the direction of growth of the newly formed neurofibers, a property of tissue specificity. The mechanism of neurotropism, the effect of the distance between the cut ends of the nerve and the choice of the silastic material were discussed.

Animals↗

[Ultrasound anatomy of the sciatic nerve of the thigh].

Ultrasound examinations of the sciatic nerve were performed using high-resolution transducers (7.5, 10 to 20 MHz) both in anatomical specimens and in healthy volunteers. The ultrasonographic anatomy (sono-anatomy) of the nerve, its course along the thigh and its echogenicity in comparison with muscles, tendons and adipose tissue were investigated in 10 isolated muscle/nerve preparations. In addition, the influence of the angle of the applied transducer on the various different tissues was evaluated. In the clinical part of the study, the sciatic nerve was identified ultrasonographically in both thighs of 50 sex-matched healthy volunteers aged between 2 and 76 years. The normal sciatic nerve presents as a tubular echogenic structure with parallel linear internal echoes in the longitudinal section, and as a punctiform moderately echoic structure in cross-section, with the perineurium producing bright boundary echoes. Varying the insonating angle of the transducer reduced echogenicity, but to a smaller degree than in muscles and tendons. Unequivocal identified of the sciatic nerve from the level of the gluteal fold to its bifurcation in the distal thigh was possible in all but one case. We conclude that the course of the sciatic nerve along the thigh can be reliably identified and imaged with high-resolution ultrasound.

Adolescent↗

Release of somatostatin and its role in the mediation of the anti-inflammatory effect induced by antidromic stimulation of sensory fibres of rat sciatic nerve.

1. The effect of antidromic stimulation of the sensory fibres of the sciatic nerve on inflammatory plasma extravasation in various tissues and on cutaneous vasodilatation elicited in distant parts of the body was investigated in rats pretreated with guanethidine (8 mg kg(-1), i.p.) and pipecuronium (200 microg kg(-1), i.v.). 2. Antidromic sciatic nerve stimulation with C-fibre strength (20 V, 0.5 ms) at 5 Hz for 5 min elicited neurogenic inflammation in the innervated area and inhibited by 50.3 +/- 4.67% the development of a subsequent plasma extravasation in response to similar stimulation of the contralateral sciatic nerve. Stimulation at 0.5 Hz for 1 h also evoked local plasma extravasation and inhibited the carrageenin-induced (1%, 100 microl s.c.) cutaneous inflammation by 38.5 +/- 10.0% in the contralateral paw. Excitation at 0.1 Hz for 4 h elicited no local plasma extravasation in the stimulated hindleg but still reduced the carrageenin-induced oedema by 52.1 +/- 9.7% in the paw on the contralateral side. 3. Plasma extravasation in the knee joint in response to carrageenin (2%, 200 microl intra-articular injection) was diminished by 46.1 +/- 12.69% and 40.9 +/- 4.93% when the sciatic nerve was stimulated in the contralateral leg at 0.5 Hz for 1 h or 0.1 Hz for 4 h, respectively. 4. Stimulation of the peripheral stump of the left vagal nerve (20 V, 1 ms, 8 Hz, 10 min) elicited plasma extravasation in the trachea, oesophagus and mediastinal connective tissue in rats pretreated with atropine (2 mg kg(-1), i.v.), guanethidine (8 mg kg(-1), i.p.) and pipecuronium (200 microg kg(-1), i.v.). These responses were inhibited by 37.8 +/- 5.1%, 49.7 +/- 9.9% and 37.6 +/- 4.2%, respectively by antidromic sciatic nerve excitation (5 Hz, 5 min) applied 5 min earlier. 5. Pretreatment with polyclonal somatostatin antiserum (0.5 ml/rat, i.v.) or the selective somatostatin depleting agent cysteamine (280 mg kg(-1), s.c.) prevented the anti-inflammatory effect of sciatic nerve stimulation (5 Hz, 5 min) on a subsequent neurogenic plasma extravasation of the contralateral paw skin. The inhibitory effect of antidromic sciatic nerve excitation on plasma extravasation in response to vagal nerve stimulation was also prevented by somatostatin antiserum pretreatment. 6. Cutaneous blood flow assessment by laser Doppler flowmetry indicated that antidromic vasodilatation induced by sciatic nerve stimulation was not inhibited by excitation of the sciatic nerve of the contralateral leg (1 Hz, 30 min) or by somatostatin (10 microg/rat, i.v.) injection. 7. Plasma levels of somatostatin increased more than 4 fold after stimulation of both sciatic nerves (5 Hz, 5 min) but the stimulus-evoked increase was not observed in cysteamine (280 mg kg(-1), s.c.) pretreated rats. 8. These results suggest that somatostatin released from the activated sensory nerve terminals mediates the systemic anti-inflammatory effect evoked by stimulating the peripheral stump of the sciatic nerve.

Animals↗

Ultrasound observation of the sciatic nerve and its branches at the popliteal fossa: always visible, never seen.

BACKGROUND: In studying patients with sciatic nerve (SN) varices the author found that the sciatic nerve and its major divisions, the tibial and peroneal nerves, could be readily identified on ultrasound imaging of the popliteal fossa. The sciatic nerve lies in the space between the popliteal vein and the small saphenous vein. OBJECTIVES: To confirm that the sciatic nerve can be identified on ultrasonography in patients with venous disease as well as in normal subjects. METHOD: Thirty unselected patients (60 limbs) attending for outpatient consultations were investigated by duplex ultrasound examination of the popliteal fossa. In 10 subjects varicose veins were present, in 20 no varices were visible on clinical examination. RESULTS: The sciatic nerve and its branches where visible and easily recognised in all cases. The sciatic nerve and the small saphenous vein lay in close proximity in cases with of small saphenous vein incompetence. CONCLUSIONS: Ultrasound identification of the sciatic nerve in the popliteal fossa allows assessment of its relationship with the adjacent veins. This technique may be useful in identifying the location of the nerve prior to surgical intervention for varices in the popliteal fossa as well as for endo-luminal occlusion procedures given the close proximity of the vein to the nerve. Sciatic nerve varices, tumours, extrinsic dislocation and nerve lesions may also be detected.

Female↗

Variation in rat sciatic nerve anatomy: implications for a rat model of neuropathic pain.

We discovered a variation of rat sciatic nerve anatomy as an incidental finding during the anatomical exploration of the nerve lesion site in a rat neuropathic pain model. To confirm the composition and distribution of rat sciatic nerve, macroscopic anatomical investigation was performed in both left and right sides in 24 adult Sprague-Dawley rats. In all rats, the L4 and L5 spinal nerves were fused tightly to form the sciatic nerve. However, the L6 spinal nerve did not fuse with this nerve completely as a part of the sciatic nerve, but rather sent a thin branch to it in 13 rats (54%), whereas in the remaining 11 rats (46%), L6 ran separately along with the sciatic nerve. Also, the L3 spinal nerve sent a thin branch to the L4 spinal nerve or sciatic nerve in 6 rats (25%). We conclude that the components of sciatic nerve in Sprague-Dawley rats vary from L3 to L6; however, the major components are L4 and L5 macroscopically. This finding is in contrast to the standard textbooks of rat anatomy which describe the sciatic nerve as having major contributions from L4, L5, and L6.

Animals↗

Effect of treating streptozotocin-induced diabetic rats with sorbinil, myo-inositol or aminoguanidine on endoneurial blood flow, motor nerve conduction velocity and vascular function of epineurial arterioles of the sciatic nerve.

Previously we have demonstrated that diabetes causes impairment in vascular function of epineurial vessels, which precedes the slowing of motor nerve conduction velocity. Treatment of diabetic rats with aldose reductase inhibitors, aminoguanidine or myo-inositol supplementation have been shown to improve motor nerve conduction velocity and/or decreased endoneurial blood flow. However, the effect these treatments have on vascular reactivity of epineurial vessels of the sciatic nerve is unknown. In these studies we examined the effect of treating streptozotocin-induced rats with sorbinil, aminoguanidine or myo-inositol on motor nerve conduction velocity, endoneurial blood flow and endothelium-dependent vascular relaxation of arterioles that provide circulation to the region of the sciatic nerve. Treating diabetic rats with sorbinil, aminoguanidine or myo-inositol improved the reduction of endoneurial blood flow and motor nerve conduction velocity. However, only sorbinil treatment significantly improved the diabetes-induced impairment of acetylcholine-mediated vasodilation of epineurial vessels of the sciatic nerve. All three treatments were efficacious in preventing the appropriate metabolic derangements associated with either activation of the polyol pathway or increased nonenzymatic glycation. In addition, sorbinil was shown to prevent the diabetes-induced decrease in lens glutathione level. However, other markers of oxidative stress were not vividly improved by these treatments. These studies suggest that sorbinil treatment may be more effective in preventing neural dysfunction in diabetes than either aminoguanidine or myo-inositol.

Aldehyde Reductase↗