Pattern of expiratory muscle activation during lower thoracic spinal cord stimulation.

Large positive airway pressures (Paws) can be generated by lower thoracic spinal cord stimulation (SCS), which may be a useful method of restoring cough in spinal cord-injured patients. Optimal electrode placement, however, requires an assessment of the pattern of current spread during SCS. Studies were performed in anesthetized dogs to assess the pattern of expiratory muscle recruitment during SCS applied at different spinal cord levels. A multicontact stimulating electrode was positioned over the surface of the lower thoracic and upper lumbar spinal cord. Recording electromyographic electrodes were placed at several locations in the abdominal and internal intercostal muscles. SCS was applied at each lead, in separate trials, with single shocks of 0.2-ms duration. The intensity of stimulation was adjusted to determine the threshold for development of the compound action potential at each electrode lead. The values of current threshold for activation of each muscle formed parabolas with minimum values at specific spinal root levels. The slopes of the parabolas were relatively steep, indicating that the threshold for muscle activation increases rapidly at more cephalad and caudal sites. These results were compared with the effectiveness of SCS (50 Hz; train duration, 1-2 s) at different spinal cord levels to produce changes in Paw. Stimulation at the T9 and T10 spinal cord level resulted in the largest positive Paws with a single lead. At these sites, threshold values for activation of the internal intercostal (7-11th interspaces) upper portions of external oblique, rectus abdominis, and transversus abdominis were near their minimum. Threshold values for activation of the caudal portions of the abdominal muscles were high (>50 mA). Our results indicate that 1) activation of the more cephalad portions of the abdominal muscles is more important than activation of caudal regions in the generation of positive Paws and 2) it is not possible to achieve complete activation of the expiratory muscles with a single electrode lead by using modest current levels. In support of this latter conclusion, a two-electrode lead system results in more uniform expiratory muscle activation and significantly greater changes in Paw.     

Mechanism of expiratory muscle activation during lower thoracic spinal cord stimulation.

Lower thoracic spinal cord stimulation (SCS) may be a useful method to restore an effective cough mechanism. In dogs, two groups of studies were performed to evaluate the mechanism of the expiratory muscle activation during stimulation at the T(9)-T(10) level, which results in the greatest changes in airway pressure. In one group, expiratory muscle activation was monitored by evoked muscle compound action potentials (CAPs) from the internal intercostal muscles in the 10th, 11th, and 12th interspaces and from portions of the external oblique innervated by the L(1) and L(2) motor roots. SCS, applied with single shocks, resulted in short-latency CAPs at T(10) but not at more caudal levels. SCS resulted in long-latency CAPs at each of the more caudal caudal recording sites. Bilateral dorsal column sectioning, just below the T(11) spinal cord level, did not affect the short-latency CAPs but abolished the long-latency CAPs and also resulted in a fall in airway pressure generation. In the second group, sequential spinal root sectioning was performed to assess their individual mechanical contribution to pressure generation. Section of the ventral roots from T(8) through T(10) resulted in negligible changes, whereas section of more caudal roots resulted in a progressive reduction in pressure generation. We conclude that 1) SCS at the T(9)-T(10) level results in direct activation of spinal cord roots within two to three segments of the stimulating electrode and activation of more distal roots via spinal cord pathways, and 2) pathway activation of motor roots makes a substantial contribution to pressure generation.     

Absence of endogenous interleukin-10 enhances secondary inflammatory process after spinal cord compression injury in mice

Interleukin-10 (IL-10) exerts a wide spectrum of regulatory activities in the immune and inflammatory response. The aim of this study was to investigate the role of endogenous IL-10 on the modulation of the secondary events in mice subjected to spinal cord injury induced by the application of vascular clips (force of 24 g) to the dura via a four-level T5–T8 laminectomy. IL-10 wild-type mice developed severe spinal cord damage characterized by oedema, tissue damage and apoptosis (measured by Annexin-V, terminal deoxynucleotidyltransferase-mediated UTP end labeling staining, Bax, Bcl-2, and Fas-L expression). Immunohistochemistry demonstrated a marked increase of localization of TNF-α, IL-1β and S100β, while western blot analysis shown an increased immunoreactivity of inducible nitric oxide synthase in the spinal cord tissues. The absence of IL-10 in IL-10 KO mice resulted in a significant augmentation of all the above described parameters. We have also demonstrated that the genetic absence of IL-10 worsened the recovery of limb function when compared with IL-10 wild-type mice group (evaluated by motor recovery score). Taken together, our results clearly demonstrate that the presence of IL-10 reduces the development of inflammation and tissue injury events associated with spinal cord trauma.     

Restoration of motor functions in disruption of the spinal cord or cauda equina]

Eight patients with a rupture of the spinal cord at the level of middle thoracic vertebrae or cauda equina at the lumbar level showed partial recovery of motor functions. The development of the activity was revealed by electromyography in body muscles and M. gluteus media in all the patients who attempted voluntary movements. Appearance and development of the activity was also observed in the muscles of the femur and crus. The level of rehabilitation shown by the patients was high enough. They could walk in fixation apparatuses, returned to their occupational activities and could practice self-service. The motor functions recovered more rapidly at the low levels of injury; however, the same and possibly complete rehabilitation was attained in 2 patients with a higher level of injury. The mechanism of the function recovery is underlain by the compensatory development of activity in the muscles of the body and capacity of the distal strip of the spinal cord for elaboration of new motor reactions in which the muscles of the extremities participate.     

Effects of magnesium sulphate following spinal cord injury in rats

Neutrophil infiltration has been implicated in the secondary destructive pathomechanisms after initial mechanical injury to the spinal cord. Tissue myeloperoxidase (MPO) activity has been shown to be an exclusive indicator of the extent of post-traumatic neutrophil infiltration. We have studied the effect of magnesium sulphate on MPO activity after spinal cord injury in rats. Rats were randomly allocated into 5 groups. Group 1 was control and normal spinal cord samples were obtained after clinical examination. Forty g-cm contusion injury was introduced to Group 2. Group 3 was vehicle, 1 ml of physiological saline was injected post-trauma. Group 4 was given 30 mg/kg methylprednisolone sodium succinate (MPSS) immediately after trauma. Group 5 was given 600 mg/kg magnesium sulphate immediately after trauma. Animals were examined by inclined plane technique of Rivlin and Tator 24 h after trauma. Spinal cord samples obtained following clinical evaluations. Magnesium sulphate treatment improved early functional scores and decreased MPO activity. These findings revealed that magnesium sulphate treatment possesses neuroprotection on early clinical results and on neutrophil infiltration after acute contusion injury to the rat spinal cord.     

Early administration of methylprednisolone decreases apoptotic cell death after spinal cord injury

The purpose of this study is to evaluate, in an experimental model of spinal cord injury (SCI), the presence of apoptotic cell death after trauma and if early administration of a single bolus of methylprednisolone (MP) influences apoptosis in the zone of trauma and in adjacent spinal cord segments. For this study, a total of 96 adult female Wistar rats were subjected to spinal contusion at the T6-T8 level, producing immediate paraplegia. Forty-eight animals (treated group) received a single intraperitoneal injection of MP, at a dose of 30 mg/kg body weight, 10 minutes later. Cells undergoing apoptosis were detected by means of immunohistochemical labeling with the monoclonal antibody Apostain (anti-ssDNA MAb F7-26), in the injured spinal cord tissue, both in the zone of the lesion and in the adjacent spinal segments (rostral and caudal zones), 1, 4, 8, 24 and 72 hours and 1 week after injury. Apoptosis was detected in neurons and glial cells in the zone of the lesion 1 hour after trauma, with a pattern that showed no changes 4 hours later. Between 4 and 8 hours postinjury, the number of apoptotic cells increased, after which it decreased over the following days. In the adjacent spinal segments, apoptotic cells were detected 4 hours after trauma, and increased progressively over the remainder of the study, the number of apoptotic cells being similar in the lesion zone and in rostral and caudal zones one week after injury. When the group of MP-treated animals was considered, significant decreases in the number of apoptotic cells were detected in the lesion zone 24 hours after injury, and in the rostral and caudal zones, at 72 hours and at 1 week after trauma. These findings show that early administration of a single bolus of MP decreases apoptotic cell death after SCI, supporting the utility of MP in reducing secondary damage in injured spinal cord tissue.     

Neuroprotective Effects of Ebselen on Experimental Spinal Cord Injury in Rats

Spinal cord injury (SCI) results in rapid and significant oxidative stress. This study was aimed to investigate the possible beneficial effects of Ebselen in comparison with Methylprednisolone in experimental SCI. Thirty six Wistar albino rats (200–250 g) were divided in to six groups; A (control), B (only laminectomy), C (Trauma; laminectomy + spinal trauma), D (Placebo group; laminectomy + spinal trauma + serum physiologic), E (Methylprednisolone group; laminectomy + spinal trauma + Methylprednisolone treated), F (Ebselen group; laminectomy + spinal trauma + Ebselen treated), containing 6 rats each. Spinal cord injury (SCI) was performed by placement of an aneurysm clip, extradurally at the level of T11–12. After this application, group A, B and C were not treated with any drug. Group D received 1 ml serum physiologic. Group E received 30 mg/kg Methylprednisolone and, Group F received 10 mg/kg Ebselen intraperitoneally (i.p.). Rats were neurologically examined 24 h after trauma and spinal cord tissue samples had been harvested for both biochemical and histopathological evaluation. All rats were paraplegic after SCI except the ones in group A and B. Neurological scores were not different in traumatized rats than that of non-traumatized ones. SCI significantly increased spinal cord tissue malondialdehyde (MDA) and protein carbonyl (PC) levels and also decreased superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), and catalase (CAT) enzyme activities compared to control. Methylprednisolone and Ebselen treatment decreased tissue MDA and PC levels and prevented inhibition of the enzymes SOD, GSH-Px and CAT in the tissues. However, the best results were obtained with Ebselen. In groups C and D, the neurons of the spinal cord tissue became extensively dark and degenerated with picnotic nuclei. The morphology of neurons in groups E and F were very well protected, but not as good as the control group. The number of neurons in the spinal cord tissues of the groups C and D were significantly less than the groups A, B, E and F. We concluded that the use of Ebselen treatment might have potential benefits in spinal cord tissue damage on clinical grounds.     

Characteristics of the reflex to stretching in spinal cord injury]

This work is aimed at ascertaining the correlation in the state of spinal cord reflex apparatus in spinal patients with the presence or absence of clonus. The value of electrical response of m. Soleus to passive flexion of the foot at different speed was studied. Clonus was observed in 10 patients (the first group), and absent in 12 (the second group). Ten normal persons served as controls. The curves of the response value distribution displayed a marked difference in individual test groups. The first group was characterized by the mode shift to the right, and the second group--to the left, in comparison with the control. This was true of all angular speeds tested. The threshold speed proved to be statistically significantly increased in the second group as compared with the normal; in the first group it was about the normal. The activity in the shin muscle and the capacity to move and even to walk was observed in the majority of the patients of the first group and only in a few patients of the second group. The data obtained showed that in patients with clonus the state of the spinal cord reflex apparatus was more normalized and the clinical condition was better than in those without clonus.     

Free Radicals in Rabbit Spinal Cord Ischemia: Electron Spin Resonance Spectroscopy and Correlation with SOD Activity

1. In nonanesthetized rabbits temporal occlusion of the abdominal aorta was used to induce oxidative stress in the lower part of the body including distal segments of the spinal cord.2. Spinal cord samples were taken from the animals exposed to 25-min aortic occlusion (AO ) or to occlusion followed by 1- or 2-hr reperfusion (AO/R1 or AO/R2, respectively) or from sham-operated animals (C). The presence of free radicals (FR) in the spinal cord samples frozen in liquid N₂ was assessed by ESR spectroscopy without spin trapping. Moreover, superoxide dismutase (SOD) activity and conjugated diene (CD) levels were measured in the samples.3. In the AO group FR were detected in the spinal cord regions close to the occlusion (lower thoracic and distal segments) along with a decrease in SOD activity. The calculated g value (g = 2.0291) indicated that the paramagnetic signal recorded might be attributed to superoxide radicals. FR were absent in the AO/R1 group. Concurrently, the SOD activity revealed a significant tendency to return to the control level. FR appeared again in the AO/R2 group, mostly in the upper and middle lumbar regions, along with a decrease in SOD activity. No sample from the C group revealed FR. A significant increase in CD levels was observed in the thoracolumbar region only in the AO/R2 group. The temporary absence of FR in the AO/R1 group suggests activation of defense antioxidant mechanisms (e.g., specific enzymatic systems such as SOD), which might have been exhausted later.4. Changes in SOD activity similar to those observed in the thoracolumbar region, though less noticeable, occurred in the obviously noncompromised tissue (upper cervical region). This points to a kind of generalized reponse of the animal to aortic occlusion.5. Direct ESR spectroscopy revealed the presence of FR as well as their time course in the spinal cord during the early phase of ischemia/reperfusion injury and the inverse relationship between FR and SOD activity.     

Assessment of upper extremity muscle function in persons with tetraplegia

The objective was to investigate the actual level of muscle function impairment in tetraplegic persons and, inextricably related to this, the possibilities to compensate function loss using new muscle coalitions. In this cross-sectional group study, 20 persons with a cervical spinal cord injury (SCI) at segmental levels C5C6 or C7C8 and 10 control persons participated. Activity from 21 upper extremity and trunk muscles was recorded during standardised gross upper extremity task performance. No substantial differences in main activation patterns were found between C7C8 and control subjects. In contrast, main activation patterns in C5C6 persons showed an absence of selectivity, which may be explained by the participants activating every controllable muscle in an attempt to perform maximally. In order to identify more intricate differences in muscle activation between control and C7C8 persons a fine motor function task may be necessary. Muscle activation patterns during arm task performance were stable in all three groups.     

Degradation of cytoskeletal proteins in experimental spinal cord injury

Spinal cord injury was produced in rats by dropping a 10 g weight from 30 cm upon dura-invested exposed spinal cord. Examination of the fine structure of the traumatic lesion (15 min to 30 min) revealed granular degeneration of axons and occasional loosening of myelin lamellae. Older lesions (4 to 72 hours) showed degeneration of axons and vesiculation of myelin. At 15 minutes there is more loss of neurofilament proteins than of myelin proteins. Substantial decreases in the neurofilament and myelin proteins were observed at 30 minutes and the losses were even greater 2–72 hours after injury. This indicates that degeneration of axons may precede degradation of the myelin sheath and also that increased proteinase(s) activity, possibly activated by calcium, mediates the traumatic axonolysis and myelinolysis in experimental spinal cord trauma.     

Electrophysiological Analysis of Transmission Via Spinal Pathways After Vertebral Trauma

Complex electrophysiological examination of the state of spinal neuronal mechanisms was carried out in patients after complicated vertebral trauma (n = 52). Electromyographic responses of the muscles of the upper and lower limbs evoked by stimulation of the peripheral nerves, effects of magnetic stimulation (MS) of the brain cortex (transcranial MS, TMS) and spinal roots, and somatosensory evoked potentials (SSEPs) were recorded. Partial disorders of the motor functions of the lower limbs were observed in 21 patients. Subjects with complete absence of movements of the limbs demonstrated two variants of the patterns of electrophysiological phenomena. In 21 patients, evoked potentials were entirely absent, while reduced MS-evoked motor responses (MS MRs) and SSEPs could be observed in 10 subjects. The presence of these potentials was indicative of partial preservation of the cerebrospinal pathways after damage to the spinal cord. Thus, estimation of the results of complex electrophysiological examination allows one to objectively verify the state and dynamics of transmission via the spinal pathways, to make justified the tactics of treatment, and to estimate the efficacy of the measures directed toward recovery of the lost functions of spinal mechanisms.     

ERK 1/2 signaling pathway is involved in nicotine-mediated neuroprotection in spinal cord neurons

Evidence indicates that agonists of neuronal nicotinic receptors (nAChRs), including nicotine, can induce neuroprotective and anti-apoptotic effects in the CNS. To study these mechanisms, the present study focused on nicotine-mediated modulation of the extracellular regulated kinase 1 and 2 (ERK1/2) pathway in cultured spinal cord neurons. Exposure to nicotine (0.1-10 microM) for as short as 1 min markedly upregulated levels of phosphorylated ERK1/2 (pERK1/2) and increased total ERK1/2 activity. Inhibition studies with mecamylamine and alpha-bungarotoxin revealed that these effects were mediated by the alpha7 nicotinic receptor. In addition, pre-exposure to U0126, a specific inhibitor of the ERK1/2 signaling, prevented nicotine-mediated anti-apoptotic effects. To indicate if treatment with nicotine also can activate ERK1/2 in vivo, a moderate spinal cord injury (SCI) was induced in rats using a weight-drop device and nicotine was injected 2 h post-trauma. Consistent with in vitro data, nicotine increased levels of pERK1/2 in this animal model of spinal cord trauma. Results of the present study indicate that the ERK1/2 pathway is involved in anti-apoptotic effects of nicotine in spinal cord neurons and may be involved in therapeutic effects of nicotine in spinal cord trauma.     

Survival in vitro of motoneurons identified or purified by novel antibody-based methods is selectively enhanced by muscle-derived factors

Motoneurons were identified in vitro by a new method using the SC1 monoclonal antibody. They constituted up to 30% of total neurons in cultures of whole spinal cord from 4.5-day chicken embryos, and survived for at least 5 days in the presence of muscle extract, but not in its absence. By contrast, other neurons and floor-plate cells survived without muscle-derived factors. Motoneurons were purified to homogeneity by 'panning' on dishes coated with SC1 antibody; they developed rapidly even in the absence of other spinal cells. Concentrations of muscle extract required for half-maximal motoneuron survival were indistinguishable in pure and mixed cultures, suggesting that muscle-derived factors act directly on motoneurons. Other purified growth factors tested, including ciliary neurotrophic factor, did not have the survival-promoting activity of muscle.     

Spinal cord-muscle relations: their role in neuro-muscular development in birds

In the present study we focused our attention on the role of spinal cord-muscle interactions in the development of muscle and spinal cord cells. Four experimental approaches were used: 1) muscle fiber-spinal cord co-culture; 2) chronic spinal cord stimulation in chick embryos; 3) direct electrical stimulation of the denervated chick muscle; 4) skeletal muscle transplantation in close apposition to the spinal cord in chick embryos. The characteristics of mATPase and energetic metabolism enzyme activities and of myosin isoform expression were used as markers for fiber types in two peculiar muscles, the fast-twitch PLD and the slow-tonic ALD. In vitro, in the absence of neurons, myoblasts can express some characteristics of either slow or fast muscle types according to their origin, while in the presence of neurons, muscle fiber differentiation seems to be related to the spontaneous rhythm delivered by the neurons. The in ovo experiments of chronic spinal cord stimulation demonstrate that the differentiation of the fast and slow muscle features appears to be rhythm dependent. In the chick, direct stimulation of denervated muscles shows that the rhythm of the muscle activity is also involved in the control of muscle properties. In chick embryos developing ALD, the changes induced by modifications of muscle tension demonstrate that this factor also influences muscle development. Other experiments show that muscle back-transplantation can alter the early spinal cord development.     

Self-Sustained Motor Activity Triggered by Interlimb Reflexes in Chronic Spinal Cord Injury,Evidence of Functional Ascending Propriospinal Pathways

The loss or reduction of supraspinal inputs after spinal cord injury provides a unique opportunity to examine the plasticity of neural pathways within the spinal cord. In a series of nine experiments on a patient, quadriplegic due to spinal cord injury, we investigated interlimb reflexes and self-sustained activity in completely paralyzed and paretic muscles due to a disinhibited propriospinal pathway. Electrical stimuli were delivered over the left common peroneal nerve at the fibular head as single stimuli or in trains at 2–100 Hz lasting 1 s. Single stimuli produced a robust interlimb reflex twitch in the contralateral thumb at a mean latency 69 ms, but no activity in other muscles. With stimulus trains the thumb twitch occurred at variable subharmonics of the stimulus rate, and strong self-sustained activity developed in the contralateral wrist extensors, outlasting both the stimuli and the thumb reflex by up to 20 s. Similar behavior was recorded in the ipsilateral wrist extensors and quadriceps femoris of both legs, but not in the contralateral thenar or peroneal muscles. The patient could not terminate the self-sustained activity voluntarily, but it was abolished on the left by attempted contractions of the paralyzed thumb muscles of the right hand. These responses depend on the functional integrity of an ascending propriospinal pathway, and highlight the plasticity of spinal circuitry following spinal cord injury. They emphasize the potential for pathways below the level of injury to generate movement, and the role of self-sustained reflex activity in the sequelae of spinal cord injury.     

脊髓损伤后脊髓神经细胞膜PAF受体特性的变化

采用３ＨＰＡＦ放射配体结合试验方法测定脊髓神经细胞膜上ＰＡＦ受体的特异性位点,观察脊髓损伤后２、６ｈ、１、３周脊髓神经细胞膜ＰＡＦ受体结合特性变化。结果显示,脊髓神经细胞膜上存在ＰＡＦ高、低亲和力结合位点,脊髓损伤后２、６ｈ、１周组ＰＡＦ受体高、低亲和力位点Ｋｄ值和Ｂｍａｘ均有不同程度下降,与对照组比较,有显著性差异（Ｐ＜０．０５）。表明在伤后早期ＰＡＦ受体亲和力增加,结合位点减少。提示ＰＡＦ受体在脊髓损伤后继发性损害病理生理过程中起一定作用。     

Neurotrophic factors influence upregulation of constitutive isoform of heme oxygenase and cellular stress response in the spinal cord following trauma

The influence of brain derived neurotrophic factor (BDNF) or insulin like growth factor-1 (IGF-1) on spinal cord trauma induced carbon monoxide (CO) production and cellular stress response was examined using immunostaining of the constitutive isoform of the hemeoxygenase (HO-2) enzyme and the heat shock protein (HSP 72kD) expression in a rat model. Subjection of rats to a 5 h spinal trauma inflicted by an incision into the right dorsal horn at T10-11 segment markedly upregulated the HO-2 and HSP expression in the adjacent spinal cord segments (T9 and T12). Pretreatment with BDNF or IGF-1 significantly attenuated the trauma induced HSP expression. The upregulation of HO-2 was also considerably reduced. These results show that BDNF and IGF-1 attenuate cellular stress response and production of CO following spinal cord injury which seems to be the key factors in neurotrophins induced neuroprotection.