Engulfing cells promote neuronal regeneration and remove neuronal debris through distinct biochemical functions of CED-1

Two important biological events happen coincidently soon after nerve injury in the peripheral nervous system in C. elegans: removal of axon debris and initiation of axon regeneration. But, it is not known how these two events are co-regulated. Mutants of ced-1, a homolog of Draper and MEGF10, display defects in both events. One model is that those events could be related. But our data suggest that they are actually separable. CED-1 functions in the muscle-type engulfing cells in both events and is enriched in muscle protrusions in close contact with axon debris and regenerating axons. Its two functions occur through distinct biochemical mechanisms; extracellular domain-mediated adhesion for regeneration and extracellular domain binding-induced intracellular domain signaling for debris removal. These studies identify CED-1 in engulfing cells as a receptor in debris removal but as an adhesion molecule in neuronal regeneration, and have important implications for understanding neural circuit repair after injury.

Neuropathic Pain: Central vs. Peripheral Mechanisms

PURPOSE OF REVIEW

Our goal is to examine the processes-both central and peripheral-that underlie the development of peripherally-induced neuropathic pain (pNP) and to highlight recent evidence for mechanisms contributing to its maintenance. While many pNP conditions are initiated by damage to the peripheral nervous system (PNS), their persistence appears to rely on maladaptive processes within the central nervous system (CNS). The potential existence of an autonomous pain-generating mechanism in the CNS creates significant implications for the development of new neuropathic pain treatments; thus, work towards its resolution is crucial. Here, we seek to identify evidence for PNS and CNS independently generating neuropathic pain signals.

RECENT FINDINGS

Recent preclinical studies in pNP support and provide key details concerning the role of multiple mechanisms leading to fiber hyperexcitability and sustained electrical discharge to the CNS. In studies regarding central mechanisms, new preclinical evidence includes the mapping of novel inhibitory circuitry and identification of the molecular basis of microglia-neuron crosstalk. Recent clinical evidence demonstrates the essential role of peripheral mechanisms, mostly via studies that block the initially damaged peripheral circuitry. Clinical central mechanism studies use imaging to identify potentially self-sustaining infra-slow CNS oscillatory activity that may be unique to pNP patients. While new preclinical evidence supports and expands upon the key role of central mechanisms in neuropathic pain, clinical evidence for an autonomous central mechanism remains relatively limited. Recent findings from both preclinical and clinical studies recapitulate the critical contribution of peripheral input to maintenance of neuropathic pain. Further clinical investigations on the possibility of standalone central contributions to pNP may be assisted by a reconsideration of the agreed terms or criteria for diagnosing the presence of central sensitization in humans.

Functional outcomes of Gartland III supracondylar humerus fractures with early neurovascular complications in children: A retrospective observational study

This was a retrospective observational study. The aim of this study was to evaluate functional outcomes in children treated for Gartland III supracondylar humerus (SCH) fracture with neurovascular (NV) injuries using validated outcome measures. A secondary goal was to determine whether clinical parameters such as age at injury, sex, weight, fracture site, and/or direction of displacement could predict NV injury at the time of fracture or long-term functional outcomes in these patients.One hundred fifty-four patients of Gartland III SCH fractures between March 2004 and May 2013 were studied retrospectively. The patients were divided into 2 groups according to the presence of NV injury. Medical records and radiographs were reviewed to assess several parameters, including age, sex, weight, treatment intervention, the extremity involved, direction of fracture displacement, and NV injury. Functional outcome was assessed on final follow-up using the Pediatric Outcomes Data Collection Instrument (PODCI) and Quick Disabilities of the Arm, Shoulder, and Hand (Quick DASH) outcome measures. Statistical analysis was used to determine the relationship between NV injury and functional outcomes.There were 33 cases with Gartland III SCH fracture associated with NV injuries (10 cases of vascular compromise, 14 cases of neural injury, and 9 cases involving both vascular compromise and neural injury). There were significant differences between the 2 groups in age (P  =  .048), weight (P  =  .009), and direction of displacement (P  =  .004). Vascular compromise and median nerve injury were most common in fractures with posterolateral displacement, and radial nerve injuries were common in fractures with posteromedial displacement. The mean global function score in the PODCI was 91.4 points, and the mean Quick DASH score was 11.7 points, with excellent functional outcomes. No differences in outcomes were identified based upon age, fracture site, sex, weight, direction of displacement, or operative technique in NV injury patients (P > .05).The majority of patients with Gartland III SCH fractures associated with NV injuries returned to a high functioning level after treatment of their injuries. NV injury does not appear to influence functional outcomes. Good functional results can be expected regardless of age, fracture site, sex, weight, direction of displacement, and operative technique.

AlphaB-crystallin expression correlates with aging deficits in the peripheral nervous system

In an effort to identify factors that contribute to age-related deficits in the undamaged and injured peripheral nervous system (PNS), we noted that Brady and colleagues found that mice null for a small heat shock protein called alphaB-crystallin (αBC) developed abnormalities early in life that are reminiscent of aging pathologies. Because of our observation that αBC protein levels markedly reduce as wild-type mice age, we investigated whether the crystallin plays a role in modulating age-related deficits in the uninjured and damaged PNS. We show here that the presence of αBC correlates with maintenance of myelin sheath thickness, reducing macrophage presence, sustaining lipid metabolism, and promoting remyelination following peripheral nerve injury in an age-dependent manner. More specifically, animals null for αBC displayed a higher frequency of thinly myelinated axons, enhanced presence of Iba1+ macrophages, and fewer immunoreactive profiles of the cholesterol biosynthesis enzyme, squalene monooxygenase, before and after sciatic nerve crush injury. These findings thus suggest that αBC plays a protective and beneficial role in the aging PNS.

Canadian Association of Neuroscience Review: Axonal Regeneration in the Peripheral and Central Nervous Systems – Current Issues and Advances

Injured nerves regenerate their axons in the peripheral (PNS) but not the central nervous system (CNS). The contrasting capacities have been attributed to the growth permissive Schwann cells in the PNS and the growth inhibitory environment of the oligodendrocytes in the CNS. In the current review, we first contrast the robust regenerative response of injured PNS neurons with the weak response of the CNS neurons, and the capacity of Schwann cells and not the oligodendrocytes to support axonal regeneration. We then consider the factors that limit axonal regeneration in both the PNS and CNS. Limiting factors in the PNS include slow regeneration of axons across the injury site, progressive decline in the regenerative capacity of axotomized neurons (chronic axotomy) and progressive failure of denervated Schwann cells to support axonal regeneration (chronic denervation). In the CNS on the other hand, it is the poor regenerative response of neurons, the inhibitory proteins that are expressed by oligodendrocytes and act via a common receptor on CNS neurons, and the formation of the glial scar that prevent axonal regeneration in the CNS. Strategies to overcome these limitations in the PNS are considered in detail and contrasted with strategies in the CNS.

[Evaluation and management of adult peripheral nerve lesions]

Adult peripheral nerve pathology is quite extensive, it comprises traumatic injuries (closed and open), compressive neuropathies and lesions secondary to other medical procedures. It is important to have a well established protocol for diagnosis, as in some lesions time is a key factor for recovery. This is important for the primary care physician that makes the diagnosis, regardless of who will treat the patient. When proposing a management plan it is important to set goals, as some lesions may be completely resolved, but in other cases all we can offer is palliative treatment due to the evolution and severity of the case.

Phenotypic switching of nonpeptidergic cutaneous sensory neurons following peripheral nerve injury

In adult mammals, the phenotype of half of all pain-sensing (nociceptive) sensory neurons is tonically modulated by growth factors in the glial cell line-derived neurotrophic factor (GDNF) family that includes GDNF, artemin (ARTN) and neurturin (NRTN). Each family member binds a distinct GFRα family co-receptor, such that GDNF, NRTN and ARTN bind GFRα1, -α2, and -α3, respectively. Previous studies revealed transcriptional regulation of all three receptors in following axotomy, possibly in response to changes in growth factor availability. Here, we examined changes in the expression of GFRα1-3 in response to injury in vivo and in vitro. We found that after dissociation of adult sensory ganglia, up to 27% of neurons die within 4 days (d) in culture and this can be prevented by nerve growth factor (NGF), GDNF and ARTN, but not NRTN. Moreover, up-regulation of ATF3 (a marker of neuronal injury) in vitro could be prevented by NGF and ARTN, but not by GDNF or NRTN. The lack of NRTN efficacy was correlated with rapid and near-complete loss of GFRα2 immunoreactivity. By retrogradely-labeling cutaneous afferents in vivo prior to nerve cut, we demonstrated that GFRα2-positive neurons switch phenotype following injury and begin to express GFRα3 as well as the capsaicin receptor, transient receptor potential vanilloid 1(TRPV1), an important transducer of noxious stimuli. This switch was correlated with down-regulation of Runt-related transcription factor 1 (Runx1), a transcription factor that controls expression of GFRα2 and TRPV1 during development. These studies show that NRTN-responsive neurons are unique with respect to their plasticity and response to injury, and suggest that Runx1 plays an ongoing modulatory role in the adult.

Surgical technique: the anterosuperior approach for reverse shoulder arthroplasty

BACKGROUND

The anterosuperior approach used for reverse shoulder arthroplasty is an intermediate between the transacromial approach originally proposed by Paul Grammont and the anterosuperior approach described by D. B. Mackenzie for shoulder arthroplasty. As an alternative to the deltopectoral approach, the anterosuperior approach has the advantages of simplicity and postoperative stability.

DESCRIPTION OF TECHNIQUE

The anterior deltoid is divided from the anterior edge of the acromioclavicular arch, allowing exposure to the glenoid for glenosphere implantation.

PATIENTS AND METHODS

We used the findings of published studies to assess instability, function and pain scores, scapular notching, and complications after this approach.

RESULTS

In a comparison of the deltopectoral and anterosuperior approaches in 527 reverse arthroplasties with a minimum 2-year followup, postoperative instability rate was greater with the deltopectoral (5.1%) than with the anterosuperior (0.8%) approach. Other published studies confirm this finding. No differences in Constant-Murley score or active mobility were found. Scapular notching occurred at similar rates after the anterosuperior (74%) and deltopectoral (63%) approaches. Humeral diaphyseal fracture rates were similar, whereas the acromial fracture rate was higher using the deltopectoral approach. Loosening tended to occur more often with the anterosuperior approach.

CONCLUSIONS

The anterosuperior approach can be used in primary and revision reverse shoulder arthroplasty, as well as in acute humeral head fracture. Its main apparent advantages are simplicity, ease of axial humerus preparation, quality of frontal exposure of the glenoid, and due to subscapularis tendon preservation, a low risk of postoperative instability. Its drawbacks are risk of inaccurate glenoid positioning, axillary nerve palsy, and deltoid weakening.

6-Sulphated chondroitins have a positive influence on axonal regeneration

Chondroitin sulphate proteoglycans (CSPGs) upregulated in the glial scar inhibit axon regeneration via their sulphated glycosaminoglycans (GAGs). Chondroitin 6-sulphotransferase-1 (C6ST-1) is upregulated after injury leading to an increase in 6-sulphated GAG. In this study, we ask if this increase in 6-sulphated GAG is responsible for the increased inhibition within the glial scar, or whether it represents a partial reversion to the permissive embryonic state dominated by 6-sulphated glycosaminoglycans (GAGs). Using C6ST-1 knockout mice (KO), we studied post-injury changes in chondroitin sulphotransferase (CSST) expression and the effect of chondroitin 6-sulphates on both central and peripheral axon regeneration. After CNS injury, wild-type animals (WT) showed an increase in mRNA for C6ST-1, C6ST-2 and C4ST-1, but KO did not upregulate any CSSTs. After PNS injury, while WT upregulated C6ST-1, KO showed an upregulation of C6ST-2. We examined regeneration of nigrostriatal axons, which demonstrate mild spontaneous axon regeneration in the WT. KO showed many fewer regenerating axons and more axonal retraction than WT. However, in the PNS, repair of the median and ulnar nerves led to similar and normal levels of axon regeneration in both WT and KO. Functional tests on plasticity after the repair also showed no evidence of enhanced plasticity in the KO. Our results suggest that the upregulation of 6-sulphated GAG after injury makes the extracellular matrix more permissive for axon regeneration, and that the balance of different CSs in the microenvironment around the lesion site is an important factor in determining the outcome of nervous system injury.

Schwannoma in head and neck: preoperative imaging study and intracapsular enucleation for functional nerve preservation

PURPOSE

In treating schwannoma patients, it is critical to determine the origin of the tumor to preserve nerve function. We evaluated the validity of preoperative imaging studies in distinguishing the neurological origin of the schwannomas of the head and neck, and the efficacy of intracapsular enucleation in preserving nerve function.

MATERIALS AND METHODS

In 7 cases of schwannomas in the head and neck region, we predicted whether the tumor originated from the vagus nerve or the cervical sympathetic chain through imaging studies including computed tomography (CT) and magnetic resonance imaging (MRI). All patients were performed intracapsular enucleation, and the function of the vagus nerve and the sympathetic nerve was evaluated preoperatively and postoperatively.

RESULTS

Preoperative imaging studies showed 6 cases where the tumor was located between the carotid artery and the internal jugular vein, and 1 case where the tumor was located posteriorly, displacing the carotid artery and the internal jugular vein anteriorly. At the time of operation, we confirmed schwannoma originating from the vagus nerve on the first 6 cases, and schwannoma originating from the sympathetic nervous system on the last case. All patients went through successful intracapsular enucleation, and of the seven schwannoma cases, 6 patients maintained normal postoperative neurological function (85.7%).

CONCLUSION

Preoperative imaging studies offer valuable information regarding the location and origination of the tumor, and intracapsular enucleation helped us to preserve the nerve function.

Effects of hyperthermia on the peripheral nervous system: a review

The present paper overviews the current knowledge about effects of hyperthermia at temperatures used in clinical oncology on the peripheral nervous system. From the experimental studies it may be concluded that the heat sensitivity of the nerve is determined by the sensitivity of the nerve vasculature. These studies show that in order to avoid induction of severe neuropathy, application of heat to the peripheral nerves should not be in excess of doses of 30 min at 44 degrees C or equivalent. Using modern equipment for application of loco-regional hyperthermia the incidence of even mild neurological complications is very low. In hyperthermic isolated limb perfusion (HILP) neurotoxicity is an often-mentioned side effect, this is in spite of the fact that in all studies a relatively mild hyperthermic temperature is used that, based on the experimental studies, should be well tolerated by the nerves and other normal tissues in the limbs. It seems that the neurotoxicity observed after HILP results from thermal enhancement of drug toxicity, very probably combined with effects of a high tourniquet pressure that is used to isolate the blood flow in the leg. Whole body hyperthermia (WBH), using anesthesia and appropriate monitoring to avoid cardiovascular stress is at present considered a safe procedure. Still in the recent past cases of neuropathy after treatment have been described. When chemotherapy, and notably cisplatin, is administered before or during hyperthermia there are several clinical and experimental observations that indicate a limited tolerance of the peripheral nervous tissue in such case. Also previous radiotherapy may limit the tolerance of nerves to hyperthermia, notably when radiation is applied with a large field size. Experimental studies show that combined treatment with radiation and heat leads to enhancement of effects of radiation (enhancement ratio approximately 1.5 at 60 min at 44 degrees C). A clear contraindication for the application of hyperthermia in patients is the presence of a neurodegenerative disease, such as multiple sclerosis. Vigilance is also required in the treatment of diabetic patients with hyperthermia, this based on experimental animal studies, but so far no clear clinical data are available.

[Construction and evaluation of the tissue engineered nerve of bFGF-PLGA sustained release microspheres]

OBJECTIVE

To study the outcomes of nerve defect repair with the tissue engineered nerve, which is composed of the complex of SCs, 30% ECM gel, bFGF-PLGA sustained release microspheres, PLGA microfilaments and permeable poly (D, L-lactic acid) (PDLLA) catheters.

METHODS

SCs were cultured and purified from the sciatic nerves of 1-day-old neonatal SD rats. The 1st passage cells were compounded with bFGF-PLGA sustained release microspheres and ECM gel, and then were injected into permeable PDLLA catheters with PLGA microfilaments inside. In this way, the tissue engineered nerve was constructed. Sixty SD rats were included. The model of 15-mm sciatic nerve defects was made, and then the rats were randomly divided into 5 groups, with 12 rats in each. In group A, autograft was adopted. In group B, the blank PDLLA catheters with PBS inside were used. In group C, PDLLA catheters, with PLGA microfilaments and 30% ECM gel inside, were used. In group D, PDLLA catheters, with PLGA microfilaments, SCs and 30% ECM gel inside, were used. In group E, the tissue engineered nerve was applied. After the operation, observation was made for general conditions of the rats. The sciatic function index (SFI) analysis was performed at 12, 16, 20 and 24 weeks after the operation, respectively. Electrophysiological detection and histological observation were performed at 12 and 24 weeks after the operation, respectively.

RESULTS

All rats survived to the end of the experiment. At 12 and 16 weeks after the operation, group E was significantly different from group B in SFI (P < 0.05). At 20 and 24 weeks after the operation, group E was significantly different from groups B and C in SFI (P < 0.05). At 12 weeks after the operation, electrophysiological detection showed nerve conduct velocity (NCV) of group E was bigger than that of groups B and C (P < 0.05), and compound amplitude (AMP) as well as action potential area (AREA) of group E were bigger than those of groups B, C and D (P < 0.05). At 24 weeks after the operation, NCV, AMP and AREA of group E were bigger than those of groups B and C (P < 0.05). At 12 weeks after the operation, histological observation showed the area of regenerated nerves and the number of myelinated fibers in group E were significantly differents from those in groups A, B and C (P < 0.05). The density and diameter of myelinated fibers in group E were smaller than those in group A (P < 0.05), but bigger than those in groups B, C and D (P < 0.05). At 24 weeks after the operation, the area of regenerative nerves in group E is bigger than those in group B (P < 0.05); the number of myelinated fibers in group E was significantly different from those in groups A, B, C (P < 0.05); and the density and diameter of myelinated fibers in group E were bigger than those in groups B and C (P < 0.05).

CONCLUSION

The tissue engineered nerve with the complex of SCs, ECM gel, bFGF-PLGA sustained release microspheres, PLGA microfilaments and permeable PDLLA catheters promote nerve regeneration and has similar effect to autograft in repair of nerve defects.

Blast related neurotrauma: a review of cellular injury

Historically, blast overpressure is known to affect primarily gas-containing organs such as the lung and ear. More recent interests focus on its ability to cause damage to solid organs such as the brain, resulting in neurological disorders. Returning veterans exposed to blast but without external injuries are being diagnosed with mild traumatic brain injury (Warden 2006) and with cortical dysfunction (Cernak et al 1999). Decades of studies have been conducted to elucidate the effects of primary blast wave on the central nervous system. These studies were mostly concerned with systemic effects (Saljo et al 2000-2003; Kaur et al 1995-1997, 1999; Cernak et al 1996, 2001). The molecular mechanism of blast-induced neurotrauma is still poorly understood. This paper reviews studies related to primary blast injury to the nervous system, particularly at the cellular level. It starts with a general discussion of primary blast injury and blast wave physics, followed by a review of the literature related to 1) the blast wave/body interaction, 2) injuries to the peripheral nervous system, 3) injuries to the central nervous system, and 4) injury criteria. Finally, some of our preliminary data on cellular injury from in vitro and in vivo studies are presented. Specifically, we report on the effects of overpressure on astrocytes. In the discussion, possible mechanisms of blast-related brain injury are discussed, as well as the concerns and limitations of the published studies. A clearer understanding of the injury mechanisms at both the molecular and macroscopic (organ) level will lead to the development of new treatment, diagnosis and preventive measures.

Traumatic neuralgia from pressure-point strikes in the martial arts: results from a retrospective online survey

CONTEXT

Many techniques in Asian martial arts hand-to-hand combat systems emphasize hitting or striking specific sites on the body that correlate with exposed portions of peripheral nerves.

OBJECTIVE

To evaluate the prevalence and clinical effects of this unique sports-related injury.

METHODS

An anonymous self-administered retrospective 20-question electronic survey was posted on a high-traffic martial arts Web site. Primary outcome measures were demographic and medical history data, including martial arts experience and neuropathic symptoms associated with injury from this form of combat. Risk of symptoms was calculated by dividing the number of individuals with symptoms in each pressure-point area by the number of individuals who were struck in these areas during martial arts training.

RESULTS

Of the 651 survey responses received, 605 met inclusion criteria. Neuropathic symptoms were reported by 291 subjects. Most symptoms occurred in individuals aged between 20 and 30 years as well as in individuals with less than 1 year of martial arts training. The majority of respondents with neuropathic symptoms reported a symptom duration of less than 1 year (207 [71%]). Individuals with more than 5 years of combat training experience had a greater risk of chronic symptoms than individuals with less experience. Strikes to pressure points on the back had the greatest risk of inducing neuropathic symptoms.

CONCLUSION

Symptoms of neurapraxia can occur in individuals as a result of practicing martial arts involving strikes on pressure points. Although the majority of symptoms resolve within 1 year, individuals with prolonged exposure to pressure-point strikes may be more likely to have chronic symptoms.

Risk of neurovascular injuries in flexor hallucis longus tendon transfers: an anatomic cadaver study

BACKGROUND

Flexor hallucis longus (FHL) tendon transfer is a frequently used treatment for both posterior tibial tendon insufficiency and chronic Achilles tendinopathy. We observed difficulties in harvesting the FHL tendon that may arise from cross-attachments with the flexor digitorum longus (FDL) tendon near the knot of Henry. The posterior tibial nerve is located nearby the decussation of these tendons. This study examined whether the difficult harvesting may be the cause of nerve injury.

METHODS

A cadaver study was performed on 24 foot specimens. In all feet, we used a double-incision technique. The FHL tendon was transected in the distal medial midfoot incision and retracted through the posteromedial hindfoot incision. After harvesting the FHL tendon, we exposed the posterior tibial nerve and its lateral and medial plantar branches to identify if any lesion had occurred.

RESULTS

The retraction failed at the first attempt in all specimens because of the presence of cross-attachments between the FHL and FDL tendons. A more extensive dissection of the FHL and FDL tendons was therefore required. We found lesions in 33% of all foot specimens, including two complete ruptures of the medial plantar nerve.

CONCLUSIONS

Harvesting of the FHL tendon when transection is made distal to the knot of Henry may cause injuries to the medial and lateral plantar nerves. Experience in this procedure may reduce the risk of nerve injuries but even then nerve lesions remain possible. The clinical significance of these nerve lesions is not described in literature and remains to be determined.

Immunolabelling of the 5-HT3B receptor subunit in the central and peripheral nervous systems in rodents

The 5-HT(3) receptor is a member of the superfamily of neurotransmitter-gated ion channels involved in fast synaptic signalling and in modulation of neurotransmitter release. As for many other channel receptors, the electrophysiological properties and the functions of the 5-HT(3) receptor are determined by subunit composition of the pentameric channel. Because in situ hybridization did not allow the detection of mRNA encoding the 5-HT(3B) subunit in the rodent central nervous system, or in nearly half of the neurons expressing the 5-HT(3A) subunit in peripheral ganglia, it has been suggested that subunit composition could define at least two 5-HT(3) receptor-expressing neuronal populations. In order to challenge this hypothesis, we have developed polyclonal antibodies directed against a portion of the second intracytoplasmic loop of the mouse 5-HT(3B) subunit. Immunohistochemical analysis in the mouse and the rat revealed that immunolabelling was most prominent in peripheral ganglia, particularly in trigeminal ganglia (TG). In rats, transection or ligature of the infraorbital nerve resulted in a pronounced accumulation of immunoreactive material at the proximal side of the lesioned nerve, and an up-regulation of both subunits in 5-HT(3) receptor-expressing TG neurons. Surprisingly, nearly 100% of neurons expressing 5-HT(3A) subunits were also labelled by anti-5-HT(3B) antibodies. We also detected 5-HT(3B) immunoreactivity in the rat hippocampal CA1 layer and in scattered cortical neurons, indicating that detection of 5-HT(3) subunit mRNA by in situ hybridization might not provide really complete mapping of heteromeric 5-HT(3A/B) vs. homomeric 5-HT(3A) receptors in the peripheral and central nervous systems in rodents.

Auditory plasticity in a basal ganglia-forebrain pathway during decrystallization of adult birdsong

Adult male zebra finches maintain highly stable songs via auditory feedback. Prolonged exposure to distorted feedback may cause this stable (i.e., "crystallized") song to change its pattern, a process known as decrystallization. In the songbird, the telencephalic nucleus LMAN (lateral magnocellular nucleus of anterior nidopallium) is necessary for feedback-dependent song decrystallization, although whether and how electrophysiological properties of LMAN neurons change during decrystallization is unknown. In normal adult zebra finches, LMAN neurons exhibit highly selective responses to auditory presentation of the bird's own song (BOS), possibly providing a permanent referent for song maintenance. If so, LMAN neurons should maintain selectivity for the originally crystallized BOS after exposure to distorted feedback and during decrystallization. Alternatively, LMAN auditory selectivity in the adult may change during decrystallization. To distinguish between these possibilities, we sectioned the vocal nerve in adult male zebra finches, which spectrally distorted the birds' songs. Over the course of several weeks, experience of distorted feedback caused the song to decrystallize in a subset of birds. At various times after nerve section, electrophysiological recordings made under anesthesia revealed that auditory selectivity in LMAN could shift to the spectrally distorted song. Such auditory plasticity could be detected during the second week after nerve section, before the time birds typically decrystallized their songs. Moreover, all birds that underwent decrystallization at later times always manifested auditory plasticity in LMAN. To our knowledge, the present findings afford the first example of an electrophysiological correlate of song decrystallization.

Peripheral nerve injury induced expression of mRNA for serine protease inhibitor 3 in the rat facial and hypoglossal nuclei but not in the spinal cord

The current work has documented the expression of the mRNAs for serine protease inhibitor 3 (SPI-3) in the facial and hypoglossal nuclei following peripheral nerve transection by using the in situ hybridization method. The signals appeared 6 hour after nerve injury; they became stronger on day 1 of injury and persisted for 21 days. SPI-3 may be involved during early events of modulating the activities of serine proteases following nerve injury. Such activities may include synaptic stripping and re-organization and facilitation of glial cell reaction to nerve injury. In the later stages of nerve injury SPI-3 may enhance neuronal survival, growth of neurites and re-establishment of synaptic contacts in the facial and hypoglossal nuclei. Hypoglossal but not facial nerve transection caused the expression of mRNAs for SPI-3 in the pineal gland. The signals appeared 6 hours after nerve injury and persisted for 21 days. The significance of this observation is not known but it indicates that the pineal gland senses injury to some peripheral nerves including the hypoglossal nerve. The study has also showed that axotomy of the sciatic nerve did not give rise to the up-regulation of the mRNAs for SPI-3 in the spinal cord. There was no hybridization signals in the lumbar segments; an indication that SPI-3 may not form part of molecules that are released during sciatic nerve transaction by the neural and non-neural cells of the spinal cord. At the moment there are no antibodies for SPI-3 and therefore future studies are needed to verify the findings. It will be interesting also to study on the role of pineal gland during peripheral nerve injuries.

Schwann cells: activated peripheral glia and their role in neuropathic pain

Schwann cells provide trophic support and in some cases, insulation to axons. After injury, Schwann cells undergo phenotypic modulation, acquiring the capacity to proliferate, migrate, and secrete soluble mediators that control Wallerian degeneration and regeneration. Amongst the soluble mediators are pro-inflammatory cytokines that function as chemoattractants but also may sensitize nociceptors. At the same time, Schwann cells produce factors that counterbalance the pro-inflammatory cytokines, including, for example, interleukin-10 and erythropoietin (Epo). Epo and its receptor, EpoR, are up-regulated in Schwann cells after peripheral nerve injury. EpoR-dependent cell signaling may limit production of TNF-alpha by Schwann cells within the first five days after injury. In addition, EpoR-dependent cell signaling may reduce axonal degeneration and facilitate recovery from chronic pain states. Other novel factors that regulate Schwann cell phenotype in nerve injury have been recently identified, including the low-density lipoprotein receptor related protein (LRP-1). Our recent studies indicate that LRP-1 may be essential for Schwann cell survival after peripheral nerve injury. To analyze the function of specific Schwann cell gene products in nerve injury and sensory function, conditional gene deletion and expression experiments in mice have been executed using promoters that are selectively activated in myelinating or non-myelinating Schwann cells. Blocking ErbB receptor-initiated cell-signaling in either myelinating or non-myelinating Schwann cells results in unique sensory dysfunctions. Data obtained in gene-targeted animals suggest that sensory alterations can result from changes in Schwann cell physiology without profound myelin degeneration or axonopathy. Aberrations in Schwann cell biology may lie at the foundation of neuropathic pain and represent an exciting target for therapeutic intervention.

A Means for Targeting Therapeutics to Peripheral Nervous System Neurons with Axonal Damage

OBJECTIVE

Delivery of biological therapeutics to motor and dorsal root ganglion neurons remains a major hurdle in the development of treatments for a variety of neurological processes, including peripheral nerve injury, pain, and motor neuron diseases. Because nerve cell bodies are important in initiating and controlling axonal regeneration, targeted delivery is an appealing strategy to deliver therapeutic proteins after peripheral nerve injury.

METHODS

Tet1 is a 12-aa peptide, isolated through phage display that is selected for tetanus toxin C fragment-like binding properties. In this study, we surveyed its uptake and retrograde transport using compartmented cultures and sciatic nerve injections. We then characterized the time course of this delivery. Finally, to confirm the retrograde transport involvement, a colchicine pretreatment was performed. We also performed competitive binding studies between Tet1 and a recombinant tetanus toxin C fragment using recombinant tetanus toxin C fragment enzyme-linked immunosorbent assay.

RESULTS

We were able to demonstrate efficient uptake and retrograde axonal transport of the Tet1 peptide in vitro and in vivo. Intraneural colchicine pretreatment partially blocked fluorescence detection in the spinal cord, revealing a retrograde axonal transport mechanism. Finally, a competitive enzyme-linked immunosorbent assay experiment revealed Tet1-specific binding to the recombinant tetanus toxin C fragment axon terminal trisialogangliosides receptor.

CONCLUSION

These properties of Tet1 can be applied to the development of therapeutic viral vectors and fusion proteins for neuronal targeting and enhanced spinal cord delivery in the treatment of nerve regeneration, neuroprotection, analgesia, and spasticity. Small peptides can be easily fused to larger proteins without significantly modifying their function and can be used to alter the binding and uptake properties of these proteins.

Relationship Between the Firing Frequency of Injured Peripheral Neurons and Inhibition of Firing by Sodium Channel Blockers

Animal models of neuropathic pain in which a peripheral nerve is damaged result in spontaneous activity in primary afferents that can be inhibited by intravenous administration of sodium channel blockers. Many of these compounds exhibit use-dependent block of sodium current, leading to the prediction that they should more readily inhibit neurons that fire at higher frequencies. This prediction was tested in 2 rat models of nerve injury, L5 spinal nerve section and sciatic nerve section. Sciatic nerve section produced average firing frequencies that were higher than spinal nerve section and often manifested as high-frequency bursting. Inhibition of firing by intravenous sodium channel blockers was longer lasting in this model. Within each model, higher frequency of firing did not translate into more effective block. In the spinal nerve section model, there was a robust inverse correlation between frequency and inhibition. Within the sciatic section model, only neurons that fired in rhythmic bursts were inhibited, and again, those firing at lower mean frequencies were more effectively inhibited. These results indicate that the efficacy of sodium channel blockers depends on the nature of the injury and the pattern of the resulting activity rather than simply the frequency of action potentials generated.

PERSPECTIVE

This study examines the ability of frequency-dependent sodium channel blockers to inhibit spontaneous firing of injured peripheral nerves in vivo. It outlines the conditions under which inhibition is more and less effective and will provide insight into conditions under which sodium channel blockers are likely to be therapeutically useful.

Loss of spinal substance P pain transmission under the condition of LPA1 receptor-mediated neuropathic pain

Among various machineries occurring in the experimental neuropathic pain model, there exists the loss of pain transmission through C-fiber neurons as well as the hypersensitivity through A-fibers. The current study reveals that molecular machineries underlying the latter hypersensitivity are derived from the events through LPA₁ receptor and its downstream RhoA-activation following peripheral nerve injury. The loss of C-fiber responses, which are mediated by spinal substance P (SP) pain transmission was observed with the nociceptive flexor responses by intraplantar injection of SP in nerve-injured mice. The immunohistochemistry revealed that SP signal in the dorsal horn was markedly reduced in such mice. All these changes were completely abolished in LPA₁^-/- mice or by the pretreatment with BoNT/C3, a RhoA inhibitor. In addition, the loss of C-fiber responses and the down-regulation of spinal SP signal induced by single intrathecal LPA injection were also abolished in such treatments. All these results suggest that the loss of pain transmission through polymodal C-fiber neurons is also mediated by the LPA₁ activation following nerve injury.

Persistent postsurgical pain: risk factors and prevention

Acute postoperative pain is followed by persistent pain in 10-50% of individuals after common operations, such as groin hernia repair, breast and thoracic surgery, leg amputation, and coronary artery bypass surgery. Since chronic pain can be severe in about 2-10% of these patients, persistent postsurgical pain represents a major, largely unrecognised clinical problem. Iatrogenic neuropathic pain is probably the most important cause of long-term postsurgical pain. Consequently, surgical techniques that avoid nerve damage should be applied whenever possible. Also, the effect of aggressive, early therapy for postoperative pain should be investigated, since the intensity of acute postoperative pain correlates with the risk of developing a persistent pain state. Finally, the role of genetic factors should be studied, since only a proportion of patients with intraoperative nerve damage develop chronic pain. Based on information about the molecular mechanisms that affect changes to the peripheral and central nervous system in neuropathic pain, several opportunities exist for multimodal pharmacological intervention. Here, we outline strategies for identification of patients at risk and for prevention and possible treatment of this important entity of chronic pain.

Neuroanatomy of the brachial plexus: The missing link in the continuity between the central and peripheral nervous systems

The brachial plexus is a complex network of nerves which extends from the neck to the axilla and which supplies motor, sensory, and sympathetic fibers to the upper extremity. Generally it is formed by the union of the ventral primary rami of the spinal nerves, C5-C8 and T1, the so-called "roots" of the brachial plexus. The goal here is to examine the neural architecture of the brachial plexus. The most constant arrangement of nerve fibers will be delineated, and then the predominant variations in neural architecture will be defined, particularly the prefixed and postfixed plexus, as well as the microanatomy and anatomy of the major terminal branches of the plexus. Multiple tracts connect many parts of the nervous system, and multiple ascending and descending tracts connect the peripheral nervous system (PNS) and lower spinal centers with the brain. This reflects that the nervous system is able to extract different pieces of sensory information from its surroundings and encode them separately, and that it is able to control specific aspects of motor behavior using different sets of neurons. Examination of the major sensory or motor pathways reveals a highly and tightly organized nervous system. In particular, at each of many levels, we see fairly exact maps of the world within the brain. In an effort to understand the functional neuroanatomy of the brachial plexus, this paper will focus briefly on the nervous connections of the nerves of the upper extremity with the brain. The goal here is to better understand "what the brain sees" after nerve injury and repair.

Nanofunctionalisation for the treatment of peripheral nervous system injuries

A construct based on the electrostatic layer-by-layer self assembly technique has been fabricated, to be used as a tailored device to encourage nerve regeneration. A multilayered nanocoating composed of three precursor bilayers of cationic poly(dimethyldiallylammonium) chloride (PDDA) and anionic poly(styrenesulfonate) (PSS), followed by bilayers of poly-D-lysine (PDL) and antibody specific to transforming growth factor 1 (anti-TGF-1), has been deposited on HYAFF 11. The assembly process has been monitored by quartz crystal microbalance (QCM) for its characterisation and then it has been used on HYAFF 11. Structural studies of the resulting multilayers confirmed stepwise deposition of anti-TGF-1, with an average layer thickness of 2.2+/-0.2 nm and an average surface density of 0.36+/-0.03 mug cm(-2). Scanning electron microscopy has been used to characterise multilayer uniformity. Finally, the immunological activity of the multilayered structure has been assessed. The results show that anti-TGF-1 can be included in its active form in a predetermined multilayered structure onto HYAFF 11 with quantitative control of layer thickness and weight, providing a high tool with great potential in tissue engineering.

Rehabilitation for the Neurologic Patient

A properly designed rehabilitation program should be an important component of the treatment plan of animals with neurologic disease. Such a program should be designed in conjunction with appropriate treatment of the underlying problem and after special consideration of the origin of the neurologic problem, the severity of the signs, the cause of the signs, their anticipated progression, and the needs of the owner and the pet. This article describes the pathophysiology of injury and recovery in the central and peripheral nervous systems, assessment of the neurologic patient, data on the prognosis and expected course of recovery for a variety of different diseases, and rehabilitation exercises appropriate for neurologic patients.

End-to-side neurorrhaphies in a rodent model of peripheral nerve injury: a preliminary report of a novel technique

OBJECT

The standard techniques for repair of peripheral nerve injuries with neuroma formation are typically suboptimal. To begin to explore alternative techniques, the authors used an established model in rodents by using end-to-side "terminolateral" neurorrhaphies (TLNs) to study alternative grafting techniques. The TLN "jump grafts" bypass a neuromain-continuity, hypothetically maintaining functional units within the neuroma to facilitate functional regeneration. Evaluation of the extent and origin of the regenerating fibers within the grafts was also undertaken.

METHODS

The right tibial nerve in four adult Sprague-Dawley rats was injured using either a crush or transection technique and compared with four uninjured controls. The contralateral peroneal nerve was immediately harvested for microsurgical repair by using TLN jump grafts in all animals. Following a 3-month recovery, the repaired nerves were evaluated electrophysiologically by using evoked electromyography (EMG). Histological preparation was then performed using dual-fluorescent labeling to study axonal regeneration and origins. Evoked EMG evaluation confirmed healthy electrical conduction across the repair, which was unchanged after transection of the neuroma, but was abolished after transection of the jump graft, indicating functional neural regeneration across both the proximal and distal TLNs of the jump grafts. Fluorescent tracing analysis confirmed regeneration across both the proximal and distal portion of the jump grafts, demonstrated both motor and sensory neurons as the source of the regenerating fibers, and demonstrated significant numbers of double-labeled cell bodies, indicating that collateral sprouting was the primary source of regenerating fibers.

CONCLUSIONS

The authors have preliminarily shown that regeneration occurs both electrophysiologically and histologically with a double-TLN jump graft. Clinically, this method could offer an alternative strategy for the technique and timing of neuroma repair.

Use of genetically engineered transgenic mice to investigate the role of galanin in the peripheral nervous system after injury

The neuropeptide galanin is present at high levels within the dorsal root ganglia (DRG) and spinal cord during development and after peripheral nerve damage in the adult. This pattern of expression suggests that it may play a role in the adaptive response of the peripheral nervous system (PNS) to injury. Several experimental paradigms have demonstrated that galanin modulates pain transmission, particularly after nerve injury. In our laboratory we have used a transgenic approach to further elucidate the functions of galanin within the somatosensory system. We have generated mice which over-express galanin (either inducibly after nerve injury, or constitutively), and knock-out (KO) mice, in which galanin is absent in all cells, throughout development and in the adult. Analysis of the nociceptive behaviour of the galanin over-expressing animals, before and after nerve injury, supports the view that galanin is an inhibitory neuromodulator of spinal cord transmission. In apparent contradiction to these findings, galanin KO animals fail to develop allodynia and hyperalgesia after nerve injury. However, further studies have shown that galanin is critical for the developmental survival of a subset of small diameter, unmyelinated sensory neurons that are likely to be nociceptors. This finding may well explain the lack of neuropathic pain-like behaviour after injury in the KO animals. Furthermore, the developmental survival role played by galanin is recapitulated in the adult where the peptide is required for optimal neuronal regeneration after injury, and in the hippocampus where it plays a neuroprotective role after excitotoxic injury.

Stem-cell plasticity and therapy for injuries of the peripheral nervous system

Numerous publications have investigated stem-cell biology and the possible therapeutic use of stem cells in a wide range of injuries and diseases. This interest has been fueled by recent reports suggesting that mesenchymal stem cells can show unorthodox plasticity, their being able to transdifferentiate into cells of different lineages, such as neuronal phenotypes. This capability has obvious implications for their potential application in tissue engineering and tissue regeneration. The peripheral nervous system has an inherent capacity for regeneration, but this is limited and not matched by the level of reinnervation of target organs, with a resulting loss of functional recovery. Several approaches have been attempted in order to overcome this deficiency, and transplant of cultured Schwann cells into bioengineered conduits has been shown to improve regeneration. An alternative may be the use of stem-cell technology, whereby cultured and differentiated stem cells can be transplanted to the site of injury in order to promote enhanced regeneration. The present review discusses the use of stem cells applied to the repair of peripheral nerve injury and their role in the regeneration process.

Peripheral Nervous System Injuries in Sport and Recreation

Many sports are associated with a variety of peripheral nervous system (PNS) injuries specific to that sport. A systematic review of sport-specific PNS injuries has not been attempted previously, and will assist in the understanding of morbidities and mortality associated with particular sporting activities, either professional or amateur. A systematic review of the literature using PubMed (1965-2003) was performed examining all known sports and a range of possible PNS injuries attributable to that sport. Numerous sporting activities (53) were found to have associated PNS injuries. The sports most commonly reported with injuries were football, hockey, soccer, baseball and winter activities. There are a number of sporting activities with injuries unique to the individual sport. This review should be of assistance for the neurologist, neurosurgeon, orthopaedic surgeon, physiatrist, sports medicine doctor, athletic trainer and general physician in contact with athletes possessing neurological injuries.

An uncommon peripheral nerve injury after penetrating injury of the forearm: the importance of clinical examination

A 22 year old woman presented to the accident and emergency department with a self inflicted stab wound to the radial side of the volar aspect of the left forearm caused by a pen knife. Her wounds were sutured on the day of injury. Over the course of next three weeks her wounds healed well but she noticed difficulty in using the hand. She therefore attended her general practitioner who suspected a possible nerve injury and referred the patient back to the A&E department. On follow up examination, she was noticed to have a loss of finger and thumb extension and weakness of thumb abduction. Active extension of the wrist (with radial deviation) was intact. There was no sensory deficit. Posterior interosseous nerve (PIN) palsy was diagnosed and the patient was referred to the regional hand surgery unit where she underwent exploration of the wound. A complete transection of the PIN in the supinator canal was found and repaired with good functional outcome. This case reflects the importance of clinical examination in uncommon peripheral nerve injuries and appropriate referral to a specialist department in case of doubtful penetrating wound that pose a threat to an underlying important structure.

Selective expression of L-serine synthetic enzyme 3PGDH in schwann cells, perineuronal glia, and endoneurial fibroblasts along rat sciatic nerves and its upregulation after crush injury

Non-essential amino acid L-serine functions as a highly potent, glia-derived neurotrophic factor, because it is a precursor for syntheses of proteins, other amino acids, membrane lipids, and nucleotides, and also because its biosynthetic enzyme 3-phosphoglycerate dehydrogenase (3PGDH) is preferentially expressed in particular glial cells within the brain. Here we pursued 3PGDH expression in peripheral nerves and its change after crush injury. In the pathway of rat sciatic nerves, 3PGDH was selectively expressed in non-neuronal elements: Schwann sheaths and endoneurial fibroblasts in sciatic nerves, satellite cells in dorsal root ganglia, and astrocytes and oligodendrocytes in the spinal ventral horn. In contrast, 3PGDH was immunonegative in axons, somata of spinal motoneurons and ganglion cells, and endoneurial macrophages. One week after crush injury, 3PGDH was upregulated in the distal segment of injured nerves, where 3PGDH was intensified in activated Schwann cells and fibroblasts. 3PGDH was still negative in activated macrophages, which were instead associated or surrounded by activated Schwann cells with intensified 3PGDH. These results suggest that in the peripheral nervous system, these non-neuronal cells synthesize and may supply L-serine to satisfy metabolic demands for maintenance and regeneration of peripheral nerves and for proliferation and activation of macrophages upon nerve injury.

Traumatic injury to CNS fiber tracts--what are the genes telling us?

In contrast to the peripheral nervous system (PNS) nerve fiber tracts of the adult central nervous system (CNS) cannot spontaneously regenerate in response to lesions. As a result injured individuals suffer from chronically impaired neuronal connections leading to major motor-, sensory- and cognitive deficits. It is generally assumed that combinatorial effects account for this regeneration failure including a growth non-permissive environment within CNS lesion zones as well as incomplete activation of axonal growth programmes. In order to design CNS repair strategies it is, therefore, imperative to address the molecular mechanisms responsible for this abortive growth behaviour by means of large scale screening techniques. This review summarizes the outcome of recent gene expression profiling studies investigating local and remote molecular reactions following CNS axotomy.

NG2 proteoglycan expression in the peripheral nervous system: upregulation following injury and comparison with CNS lesions

The chondroitin sulphate proteoglycan NG2 blocks neurite outgrowth in vitro and thus may be able to inhibit axonal regeneration in the CNS. We have used immunohistochemistry to compare the expression of NG2 in the PNS, where axons regenerate, and the spinal cord, where regeneration fails. NG2 is expressed by satellite cells in dorsal root ganglia (DRG) and in the perineurium and endoneurium of intact sciatic nerves of adult rats. Endoneurial NG2-positive cells were S100-negative. Injury to dorsal roots, ventral rami or sciatic nerves had no effect on NG2 expression in DRG but sciatic nerve section or crush caused an upregulation of NG2 in the damaged nerve. Strongly NG2-positive cells in damaged nerves were S100-negative. The proximal stump of severed nerves was capped by dense NG2, which surrounded bundles of regenerating axons. The distal stump, into which axons regenerated, also contained many NG2-positive/S100-negative cells. Immunoelectron microscopy revealed that most NG2-positive cells in distal stumps had perineurial or fibroblast-like morphologies, with NG2 being concentrated at the poles of the cells in regions exhibiting microvillus-like protrusions or caveolae. Compression and partial transection injuries to the spinal cord also caused an upregulation of NG2, and NG2-positive cells and processes invaded the lesion sites. Transganglionically labelled ascending dorsal column fibres, stimulated to sprout by a conditioning sciatic nerve injury, ended in the borders of lesions among many NG2-positive processes. Thus, NG2 upregulation is a feature of the response to injury in peripheral nerves and in the spinal cord, but it does not appear to limit regeneration in the sciatic nerve.

Regulation of stearoyl-CoA desaturase-1 after central and peripheral nerve lesions

Background

Interruption of mature axons activates a cascade of events in neuronal cell bodies which leads to various outcomes from functional regeneration in the PNS to the failure of any significant regeneration in the CNS. One factor which seems to play an important role in the molecular programs after axotomy is the stearoyl Coenzyme A-desaturase-1 (SCD-1). This enzyme is needed for the conversion of stearate into oleate. Beside its role in membrane synthesis, oleate could act as a neurotrophic factor, involved in signal transduction pathways via activation of protein kinases C.

Results

In situ hybridization and immunohistochemistry demonstrated a strong up-regulation of SCD at mRNA and protein level in regenerating neurons of the rat facial nucleus whereas non-regenerating Clarke's and Red nucleus neurons did not show an induction of this gene.

Conclusion

This differential expression points to a functionally significant role for the SCD-1 in the process of regeneration.

A New Way to Lose Your Nerve

Peripheral nerve damage results in loss of sensation in the affected region of the body. Oaklander and Brown now report that, in the rat, transection of a peripheral nerve in only one side of the body also results in profound loss of the innervation of the same region on the opposite side of the body. Peripheral nerve damage may also produce persistent (neuropathic) pain conditions that are presumed to arise from maladaptive reorganization of the central nervous system. Thus, the possibility that comparable bilateral changes occur in patients and that such changes contribute to neuropathic pain conditions must be considered.

[Microtraumatic peripheral neuropathies in sports]

The microtraumatic peripheral neuropathies encountered during athletic activities are not related to a specific sport, and are induced by overuse or forced constraints as seen in scapular syndromes, in distal neuropathies of upper and lower limbs, and in the foot. These neuropathies are less frequently seen than those following direct traumatic conditions. The constant increase in sport activities in the general population implies that each neurologist should ask for athletic habits of his patient in order not to miss the repetitive activities that can induce an atypical nerve injury. Electrodiagnostic (ENMG) studies in the background of sporting activities are performed in similar ways as in a general setting, but the synthesis may be more complex in relation to frequent associated orthopaedic disorders. ENMG studies are useful in the diagnosis of pain syndromes with or without paresthesia in sports-related nerve injuries.

[Gunshot injuries of peripheral nervous system: the questions of classification and diagnostics]

Two hundreds and sixty-seven patients with gunshot injuries of 394 nerves and plexus underwent clinical and electromyographic investigation and H-reflex evaluation as well. Based on the results of the data obtained, 3 types of nerves trunk injuries: neuroapraxia, axonothmesis and neurothmesis, were identified. The reduction of biopotential amplitude and synergic muscular activity, decrease of impulse conduction velocities (ICVeff--up to 30%), M-response amplitude (up to 50% and more) and motor units functioning were characteristic of neuroapraxia of nerve trunks. Axonothmesis of nerve trunks featured by the reduction of the amplitude and frequency of muscular biopotentials, decrease of its synergic activity, marked reduction of ICVeff (30--60%), rough fall of M-response amplitude and motor units functioning. In neurothmesis of nerve trunks, "bioelectrical silence" and disappearance of synergic muscular activity as well as an absence of M-response of denervated muscles were observed. An evaluation of monosynaptic reflex has a substantial significance for the determination of the level of low extremities injuries.

Expression of complement components in the peripheral nervous system

We have generated a SAGE (serial analysis of gene expression) library of normal sciatic nerve and found tags encoding for mRNAs of the complement system highly represented. RNA (RT-PCR and northern blot hybridization) and protein (western blot analysis and immunohistochemistry) studies confirmed these findings. High expression of classical pathway components, alternative pathway components and inhibitory components was observed in specific regions of the sciatic nerve. The first components of complement were found in axons, whereas the inhibitory components were detected in the perineurium, thereby protecting the nerve from a complement attack. Immunoreactivity towards activated complement factors was noted in post traumatic neuromas and after acute crush injury, which exemplify nerve regeneration and degeneration. We propose that local production of complement in the peripheral nervous system participates in the protection of healthy nerve and is needed for efficient clearance of myelin after injury: a prerequisite for normal regeneration and remyelination of the peripheral nerve.

Plasticity of the human motor system following muscle reconstruction: a magnetic stimulation and functional magnetic resonance imaging study

OBJECTIVE

Although motor system plasticity in response to neuromuscular injury has been documented, few studies have examined recovered and functioning muscles in the human. We examined brain changes in a group of patients who had a muscle transfer.

METHODS

Transcranial magnetic stimulation (TMS) was used to study a unique group of 9 patients who had upper extremity motor function restored using microneurovascular transfer of the gracilis muscle. The findings from the reconstructed muscle were compared to the homologous muscle of the intact arm. One patient was also studied with functional magnetic resonance imaging (fMRI).

RESULTS

TMS showed that the motor threshold and short interval intracortical inhibition was reduced on the transplanted side while at rest but not during muscle activation. The difference in motor threshold decreased with the time since surgery. TMS mapping showed no significant difference in the location and size of the representation of the reconstructed muscle in the motor cortex compared to the intact side. In one patient with reconstructed biceps muscle innervated by the intercostal nerves, both TMS mapping and fMRI showed that the upper limb area rather than the trunk area of the motor cortex controlled the reconstructed muscle.

CONCLUSIONS

Plasticity occurs in cortical areas projecting to functionally relevant muscles. Changes in the neuronal level are not necessarily accompanied by changes in motor representation. Brain reorganization may involve multiple processes mediated by different mechanisms and continues to evolve long after the initial injury.

SIGNIFICANCE

Central nervous system plasticity following neuromuscular injury may have functional relevance.