Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Peripheral Nerves”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 829 records · Page 46Linked to original sources
PubMed2002

Turnover epineural sheath tube in primary repair of peripheral nerves.

The epineural repair technique, which is the gold standard of peripheral nerve injuries, is still far from being ideal. The purpose of this study was to investigate the effects of the turnover epineural sheath tube (TEST) when used over the primary nerve repair site to improve nerve regeneration. Twenty-five Wistar rats were divided into three groups and were operated. In the sham control group, the sciatic nerve was dissected from the sciatic notch to its bifurcation and was left intact. In the primary epineural repair group an incision was made on the nerve and it was repaired using six epineural sutures. In the TEST group, after the incision was made the nerve ends were approximated with two epineural sutures. A proximal circular epineural incision was then made to enable the epineurium to be turned and slid over the repair site. Functional recovery was evaluated by walking tract analysis, and the sciatic functional index was calculated. Histomorphometric studies of the sciatic nerves and gastrocnemius muscles were also performed 3 months postoperatively. Three months postoperatively, functional analysis and nerve and muscle histomorphometric studies revealed similar results in the primary repair and TEST groups. There was no significant difference (p > 0.05) between the results of the TEST and the primary nerve repair groups. However, during the microscopic examination, a decrease in both foreign material reaction and an inflammatory response with less fibrosis were observed in the TEST group. The TEST has a nerve-healing property similar to primary epineural repair, with the advantage of a reduced number of sutures, which decreases the fibrosis around the repair site. The TEST is an alternative treatment modality among other techniques, especially for polyfascicular peripheral nerves.

Animals↗
PubMed1984

Carbonic anhydrase activity of human peripheral nerves: a possible histochemical aid to nerve repair.

The return of usable function after injury of peripheral nerves depends upon the appropriate regeneration of axons to their end organs. Debridement trimmings of severed nerves harvested during surgery were stained to demonstrate carbonic anhydrase activity. This histochemical method can be accomplished within 3 to 4 hours of receiving the tissue. Nerve fascicles were readily discriminated from one another by the individual staining patterns of their constituent axons. Axoplasmic staining was predominantly a feature of sensory fibers, and myelin staining was characteristic of skeletal motor axons. Carbonic anhydrase histochemistry may provide a means of accurately matching fascicles in cut nerve ends.

Adult↗
PubMed2003

Experimental strategies to promote functional recovery after peripheral nerve injuries.

The capacity of Schwann cells (SCs) in the peripheral nervous system to support axonal regeneration, in contrast to the oligodendrocytes in the central nervous system, has led to the misconception that peripheral nerve regeneration always restores function. Here, we consider how prolonged periods of time that injured neurons remain without targets during axonal regeneration (chronic axotomy) and that SCs in the distal nerve stumps remain chronically denervated (chronic denervation) progressively reduce the number of motoneurons that regenerate their axons. We demonstrate the effectiveness of low-dose, brain-derived neurotrophic and glial-derived neurotrophic factors to counteract the effects of chronic axotomy in promoting axonal regeneration. High-dose brain-derived neurotrophic factor (BDNF) on the other hand, acting through the p75 receptor, inhibits axonal regeneration and may be a factor in stopping regenerating axons from forming neuromuscular connections in skeletal muscle. The immunophilin, FK506, is also effective in promoting axonal regeneration after chronic axotomy. Chronic denervation of SCs (>1 month) severely deters axonal regeneration, although the few motor axons that do regenerate to reinnervate muscles become myelinated and form enlarged motor units in the reinnervated muscles. We found that in vitro incubation of chronically denervated SCs with transforming growth factor-beta re-established their growth-supportive phenotype in vivo, consistent with the idea that the interaction between invading macrophages and denervated SCs during Wallerian degeneration is essential to sustain axonal regeneration by promoting the growth-supportive SC phenotype. Finally, we consider the effectiveness of a brief period of 20 Hz electrical stimulation in promoting the regeneration of axons across the surgical gap after nerve repair.

Animals↗
PubMed1979

[When should peripheral nerves be grafted? (author's transl)].

In the presence of peripheral nerve damage, the only acceptable procedure is suture without tension, carried out under excellent conditions of fascicular approximation. In the case of loss of substance, immediate or secondary suture should never be performed. In the experience of "S.O.S. Main" secondary suture has led to the most disastrous results. Nerve graft, as an emergency, is legitimate in the case or reimplantations, in view of the high degree of technical competence of the teams, and the experience acquired. Deffered nerve graft is envisaged at about the end of the second month:--either in the absence of suture,--or in the absence of recovery. When there is any doubt, further examination at the 4 th or 5 th month ensures that treatment is not delayed too long. At all events, examinations must be repeated every two months in order to study nerve regrowth and to determine the need for possible though difficult reoperation if it stops.

Humans↗
PubMed2006

Electrode array for reversing the recruitment order of peripheral nerve stimulation: experimental studies.

One of the most challenging problems in peripheral nerve stimulation is the ability to activate selectively small axons without large ones. Electrical stimulation of peripheral nerve activates large diameter fibers before small ones. Currently available techniques for selective activation of small axons without large ones require long-duration stimulation pulses (>500 micros) and large stimulation amplitude, which shorten battery life of the implanted stimulator and could lead to electrode corrosion. In the current study, the hypothesis that small axons can be recruited before large ones with narrow pulse width (50 micros) using an electrode array was tested in both simulations simulation and experiments in the cat lateral gastrocnemius (LG) model. The LG nerve innervates both LG and soleus muscle groups with axons within 10-13 and 8-12 microm diameter ranges, respectively. A finite element model of LG nerve was constructed and simulations showed that, when activating 40% of LG, a conventional tripolar electrode activated only 9% of soleus whereas the electrode arrays of 5, 7, and 11 contacts activated 39, 46, and 60% of soleus respectively, suggesting that the arrays could activate small axons before fully recruiting large axons. In animal experiments, peak twitch force of LG and soleus were plotted as a function of stimulation amplitude to indicate the recruitment curve. At 40% activation of LG, a conventional tripolar electrode activated only 7% of soleus whereas the electrode arrays of 5, 7, and 11 contacts activated 43, 48, and 72% of soleus respectively. The electrode arrays also decreased significantly the recruitment curve slopes to only 10-20% of the value obtained for the tripolar electrode in both computer simulations and experiments. In conclusion, the 5-, 7-, and 11-contact arrays can be used to reverse the recruitment order of peripheral nerve stimulation with a narrow pulse.

Animals↗
PubMed1992

Spatiotemporal increases in epidermal growth factor receptors following peripheral nerve injury.

Non-neuronal cells of peripheral nerve respond to axonal injury with a series of cellular changes that facilitate neuronal regeneration. To characterize the potential role of the epidermal growth factor (EGF) family of proteins in this response, we monitored the expression of EGF receptor mRNA and protein in the injured rat sciatic nerve. EGF receptor mRNA is synthesized in both primary cultured fibroblasts and Schwann cells, and Schwann cells express EGF receptor-like immunoreactivity. In situ hybridization and immunocytochemistry revealed that EGF receptor mRNA and protein are expressed in Schwann cells and fibroblasts of the sciatic nerve in vivo, and that receptor levels increase following nerve injury. Thirty-six hours postlesion, EGF receptors were expressed in gradients along the nerve both proximal and distal to the lesion, with the highest levels localized adjacent to the transection site. By 72 hr, receptor levels were maintained in a gradient in the proximal segment, but were uniformly increased throughout the portions of the distal segment that were analyzed. These changes were similar to those observed for low-affinity NGF receptor mRNA and protein, with transection causing increased expression in both Schwann cells and fibroblasts. Northern blots confirmed that primary cultured fibroblasts express low-affinity NGF receptor mRNA. To determine whether spatiotemporal gradients were a general characteristic of the nerve injury response, we monitored expression of the mRNA encoding the major myelin protein P0. Levels of P0 mRNA decreased initially in cells immediately adjacent to the transection site and, by 72 hr, were uniformly decreased throughout the distal segment. These data suggest that members of the EGF family of proteins may play a role in the peripheral nerve response to injury, and demonstrate a generalized gradient of cellular responses that commence at the transection site and progress distally in the nerve in the absence of intact axons.

Animals↗
PubMed1986

Isolation of peripheral nerve collagen.

A new method for the isolation of high yields of collagen from human peripheral nerve is described. A major technique adopted in the present work is sedimentation of the tissue homogenates in a sucrose density gradient. The defatted fibrous material isolated after the removal of myelin was shown to be a relatively pure collagenous substance by amino acid analysis, indicating that the removal of noncollagenous proteins, especially glycoproteins, from collagen fibrils was effectively achieved by this method. The yield of collagen at this step was more than 90% of the total collagen in peripheral nerve. Subsequent extractions with solutions of neutral saline and sodium citrate were found to give further purification of the collagenous protein. The collagens from embryonic peripheral nerves were composed of Type I and III collagens, while Type III collagen was found to be less abundant in adult peripheral nerves.

Adult↗
PubMed1981

Wallerian degeneration of peripheral nerve. Age-dependent loss of nerve lipids.

The age-dependent loss of the major peripheral nerve lipids (cholesterol, phospholipid, and total galactolipid) was quantitated over a period of 9 weeks of Wallerian degeneration induced by surgical transection of rabbit sciatic nerves in animals of several ages. Proportionate losses of these lipids were determined by calculating the content of each lipid on a per nerve and on a per gram fresh weight basis remaining after a given period of Wallerian degeneration as a percent of original normal values at several time following surgery. The proportionate loss of each lipid from the distal stump was the most prompt and the most complete in nerves transected at 2 weeks of age, and the least in nerves transected at 20 weeks of age. The prompter clearance of these lipids from younger than older degenerating nerve gives convincing evidence that the suggestion from light-microscopic studies of faster clearance of neural debris in younger than in older animals is correct. A possible relationship between these biochemical findings and the phenomenon of greater functional recovery from peripheral nerve injury in younger than in older subjects is discussed.

Age Factors↗
PubMed2001

Pericellular Griffonia simplicifolia I isolectin B4-binding ring structures in the dorsal root ganglia following peripheral nerve injury in rats.

Patients with a peripheral nerve injury often suffer from persistent chronic pain, but the underlying mechanism remains largely unknown. The persistent nature of the pain suggests injury-induced profound structural changes along the sensory pathways. In the present study, using the plant Griffonia simplicifolia I isolectin B4 (IB4) as a marker for nonpeptidergic small sensory neurons, we sought to examine whether these neurons sprout in the dorsal root ganglia (DRG) in response to peripheral nerve injury. The lumbar 5 (L5) spinal nerve was transected, and rats were allowed to survive for varying lengths of time before IB4 histology was performed. We found that a subpopulation of IB4-positive sensory neurons sprouted robustly after spinal nerve injury. Twelve weeks after spinal nerve injury, the IB4-positive ring structures became dramatic and encircled both large and small neurons in the DRG. The aberrant sprouting of small sensory neurons was also demonstrated by retrograde labeling. The processes of satellite cells surrounding large sensory neurons also became IB4 positive, and 87.8% of perineuronal IB4-positive ring structures intermingled and/or coexpressed with glial fibrillary acidic protein-positive satellite cells. Thus, the sprouting axons of IB4-positive neurons were intermingled with IB4-positive satellite cells, forming perineuronal ring structures surrounding large-diameter neurons. Ultrastructural examinations further confirmed that IB4-positive nerve terminals were entangled with satellite cells and IB4-negative unmyelinated sprouting fibers around sensory neurons. These studies have provided the first evidence that a subpopulation of IB4-binding small sensory neurons sprouts and forms perineuronal ring structures together with IB4-positive satellite cells in response to nerve injury. The significance of the sprouting of IB4-positive neurons remains to be determined.

Animals↗
PubMed1988

Surface anodal stimulation of human peripheral nerves.

Bipolar surface stimulation of human peripheral nerves with short square pulses elicits action potentials in the A-alpha fibers at the beginning of the stimulus pulse both at the cathode (cathodal stimulation) and simultaneously in a hypopolarized region surrounding the anode (anodal stimulation). When recording with a bipolar surface electrode on the "anodal side" of the stimulating electrode a stimulus of medium strength gives a double peak response of submaximal amplitude. The peak with long latency is generated by the cathode and the peak with short latency by the anode. With a strong stimulus and recording on the "anodal side" only the short latency peak (with a maximal amplitude) is recorded. With a weak stimulus only the long latency peak (with a submaximal or maximal amplitude) is seen. These findings have importance in standard neurography investigations since mistakes concerning the polarity of the stimulating electrode affect the calculation of latencies, nerve conduction velocities, F-responses and SEPs. A nerve action potential with dual peaks may also be mistaken as a sign of anomalous innervation or activation of nerve axon subpopulations.

Action Potentials↗
PubMed1998

Analysis of upper and lower extremity peripheral nerve injuries in a population of patients with multiple injuries.

BACKGROUND: The purpose of this study was to determine the prevalence, cause, severity, and patterns of associated injuries of limb peripheral nerve injuries sustained by patients with multiple injuries seen at a regional Level 1 trauma center. METHODS: Patients sustaining injuries to the radial, median, ulnar, sciatic, femoral, peroneal, or tibial nerves were identified using a prospectively collected computerized database, maintained by Sunnybrook Health Science Centre, and a detailed chart review was undertaken. RESULTS: From a trauma population of 5,777 patients treated between January 1, 1986, and November 30, 1996, 162 patients were identified as having an injury to at least one of the peripheral nerves of interest, yielding a prevalence of 2.8%. These 162 patients sustained a total of 200 peripheral nerve injuries, 121 of which were in the upper extremity. The mean patient age was 34.6 years (SEM +/- 1.1 year), and 83% of patients were male. The mean injury severity score was 23.1 (+/-0.90), and the mean length of hospital stay was 28 days (+/-1.8). CONCLUSIONS: Motor vehicles crashes predominated (46%) as the cause of injury. The most frequently injured nerve was the radial nerve (58 injuries), and in the lower limb, the peroneal nerve was most commonly injured (39 injuries). Diagnosis of a peripheral nerve injury was made within 4 days of admission to Sunnybrook Health Science Centre in 78% of the cases. Surgery was required to treat 54% of patients. Head injuries were the most common associated injury, occurring in 60% of patients. Other common associated injuries included fractures and dislocations. The present report aims to aid in identification and treatment of peripheral nerve injuries.

Adolescent↗
PubMed2006

Possible involvement of increase in spinal fibronectin following peripheral nerve injury in upregulation of microglial P2X4, a key molecule for mechanical allodynia.

We have recently demonstrated that the P2X4 receptor, an ATP-gated cation channel, in spinal microglia is a key molecule that mediates the mechanical allodynia induced by peripheral nerve injury. Although microglial P2X4 receptor expression is increased after peripheral nerve injury, the molecular mechanism(s) underlying its upregulation remains largely unknown. Fibronectin is a member of the extracellular matrix molecules and is actively produced in response to injury and diseases in the CNS. Here, we describe the influence of fibronectin on P2X4 receptor expression in microglia and the upregulation of fibronectin after peripheral nerve injury. Microglia that were cultured on fibronectin-coated dishes showed a marked increase in P2X4 receptor expression, both at the mRNA and protein levels, as compared to those cultured on control dishes. Fibronectin also enhanced the microglial Ca2+ responses mediated by P2X4 receptors. Moreover, Western blot examination of the spinal cord from a rat with spinal nerve injury indicated that fibronectin was upregulated on the ipsilateral side. Interestingly, intrathecal injection of ATP-stimulated microglia to the rat lumber spinal cord revealed that microglia cultured on fibronectin-coated dishes was more effective in the induction of allodynia than microglia cultured on control dishes. Taken together, our results suggest that spinal fibronectin is elevated after the peripheral nerve injury and it may be involved in the upregulation of the P2X4 receptor in microglia, which leads to the induction of neuropathic pain.

Adenosine Triphosphate↗
PubMed2003

Effects of immunosuppression on regrowth of adult rat retinal ganglion cell axons into peripheral nerve allografts.

Analysis of the effectiveness of allografts and immunosuppression in the repair of nerve defects in the adult peripheral nervous system (PNS) has a long experimental and clinical history. There is little information, however, on the use of allografts in peripheral nerve (PN) transplantation into the injured central nervous system (CNS). We assessed the ability of PN allografts (from Dark-Agouti rats) to support regeneration of adult rat retinal ganglion cell (RGC) axons in immunosuppressed host Lewis rats. PN allografts were sutured onto intraorbitally transected optic nerves. Three weeks after grafting, regenerating RGC axon numbers were determined using retrograde fluorescent labelling, and total axons within PN grafts were assessed using pan-neurofilament immunohistochemistry. In the absence of immunosuppression, PN allografts contained few axons and there were very few labelled RGC. These degenerate grafts contained many T cells and macrophages. Systemic (intraperitoneal) application of the immunosuppressants cyclosporin-A or FK506 reduced cellular infiltration into allografts and resulted in extensive axonal regrowth from surviving RGCs. The average number of RGCs regenerating axons into immunosuppressed allografts was not significantly different from that seen in PN autografts in rats sham-injected with saline. Many pan-neurofilament-positive axons, a proportion of which were myelinated, were seen in immunosuppressed allografts, particularly in proximal regions of the grafts toward the optic nerve-PN interface. This study demonstrates that PN allografts can support axonal regrowth in immunosuppressed adult hosts, and points to possible clinical use in CNS repair.

Animals↗
PubMed1997

An intact peripheral nerve preparation for monitoring inputs from single muscle afferent fibres.

A preparation is described that permits the monitoring of activity from individual muscle afferent nerve fibres in an intact peripheral nerve in the forelimb of the cat. The nerve is a fine branch of the deep radial that supplies the indicis proprius muscle. When it is freed from nearby tissue over a length of 2-5 cm and placed in continuity over a silver hook electrode, it becomes possible to identify and monitor the impulse activity from each muscle afferent fibre activated by stretch or vibration applied to the muscle tendon or by focal mechanical stimulation of the muscle at the presumed site of individual spindle receptors. With this preparation it is possible to examine the central actions and security of transmission at central synaptic targets for single, identified muscle afferent fibres arising in the cat's forearm.

Afferent Pathways↗
PubMed1982

Biocompatibility of a silicon based peripheral nerve electrode.

The biocompatibility of a silicon neuroelectric interface for chronic use in mammalian peripheral nerves was investigated. New Zealand white rabbits were used as the animal model. The implant was made of (110) silicon coated with one micron of silicon dioxide. An anisotropic etch was used to form a grid of ten silicon bars each 40 microns wide and spaced 160 microns apart. A Silastic nerve cuff was molded onto each side of the grid. Using microsurgical techniques, the nerve was transected and sutured into the implant cuff. One implanted rabbit was completely analyzed and is reported here. By 32 days post operatively, the EMG of the affected muscles had partially recovered. The EMG of the affected muscles was indistinguishable from the contralateral control muscles after 150 days. At 332 days, the conduction properties of the implanted nerve confirmed that the nerve was capable of conduction through the silicon grid. Histological observations were consistent with normal peripheral nerve regeneration following microsurgical neurrorhaphy. Seven additional rabbits have been implanted and will be fully analyzed in the future. It was concluded that the silicon peripheral nerve implant described here should be pursued as a substrate for a chronic neuroelectric interface.

Animals↗
PubMed1999

Migration of schwann cells in peripheral-nerve regeneration.

Schwann cells play a central role in peripheral-nerve regeneration, in which it has been shown that the addition of exogenous Schwann cells enhances the temporal and spatial sequence of events observed in regeneration. In this study, the authors investigated the fate of exogenous cells in this process by using fluorescently tagged autogenous Schwann cells in an established rat model of peripheral-nerve regeneration. Tracking labeled cells over a 4-week period revealed early migration of Schwann cells into the proximal nerve segment, followed by a concentration of migrating Schwann cells, leading the proximal growth cone throughout the regenerative process. The early proximal distribution of labeled cells suggests active migration in response to nerve damage, with spatial localization at the center of the proximal nerve segment and not the epineural surface. These observations demonstrate an interaction of exogenous Schwann cells with intact nerve tissue in vivo and affirm their role in the directional growth of regenerating axons.

Animals↗
PubMed2003

Immunohistochemical demonstration of EMA/Glut1-positive perineurial cells and CD34-positive fibroblastic cells in peripheral nerve sheath tumors.

To clarify the cellular composition of various peripheral nerve tumorous lesions (traumatic neuroma, 5 cases; schwannoma, 10 cases; neurofibroma, 14 cases; perineurioma, 3 cases; conventional malignant peripheral nerve sheath tumor (MPNST), 7 cases; perineurial MPNST, 4 cases), expression of several markers specific to nerve sheath cells, including glucose transporter protein 1 (Glut1) and CD34, were immunohistochemically investigated with highly sensitive detection methods. In normal nerves and neuromas, perineuriums were positive for Glut1 as well as for epithelial membrane antigen (EMA), and there were some CD34-positive fibroblast-like cells in the endoneurium. Schwannomas consisted principally of S-100 protein-positive Schwann cells, whereas a few CD34-positive fibroblastic cells were present in Antoni B areas. Neurofibromas and conventional MPNST exhibited a mixed proliferation of S-100 protein-, EMA/Glut1-, and CD34-positive cells, indicating a heterogeneous composition of the constituents. The catalyzed signal amplification (CSA) system demonstrated more numerous EMA-positive perineurial cells in neurofibromas than did the ENVISION+ method. Perineurial cell tumors (benign and malignant) were composed of EMA/Glut1-positive and S-100 protein-negative tumor cells. The present study confirmed the characteristic cellular composition to each nerve sheath tumor immunohistochemically and showed the usefulness of the nerve sheath cell markers. Glut1 as well as EMA are specific to perineurial cells, and CD34 seems to be immunoreactive to endoneurial fibroblasts.

Antigens, CD34↗
PubMed2006

Delayed acetyl-L-carnitine administration and its effect on sensory neuronal rescue after peripheral nerve injury.

Protection of sensory neurons after peripheral nerve injury is clinically crucial since inadequate sensory recovery is seriously affected by the death of up to 40% of sensory neurons. Immediate acetyl-L-carnitine (ALCAR) treatment eliminates this cell loss, but may not always be clinically feasible, hence we studied the effect of delaying the initiation of ALCAR treatment. Five groups of rats (n=5 per group) underwent unilateral sciatic nerve axotomy. ALCAR treatment (50 mg/kg/day) was initiated immediately, or after delays of 6 h, 24 h or 7 days after injury. A sham-treated group served as control. L4 and L5 dorsal root ganglia were harvested bilaterally 2 weeks after injury and stereological sensory neuron counts were obtained. Immediate sham treatment provided no neuroprotection (25% loss). Cell loss was eliminated when ALCAR was commenced within<or=24 h of axotomy. No statistically significant neuroprotective effect (18% loss) was evident compared to sham when ALCAR administration was initiated 7 days post-axotomy. When commenced within a clinically applicable time frame ALCAR treatment remains highly neuroprotective, potentially improving clinical outcome following peripheral nerve trauma.

Acetylcarnitine↗