Longitudinal extension of oedema in experimental spinal cord injury--evidence for two types of post-traumatic oedema

The relative contribution of edema and hemorrhage to raised intrathecal pressure after traumatic spinal cord injury

Raised intrathecal pressure (ITP) after traumatic spinal cord injury (SCI) is a critically important aspect of injury development that may result in significantly greater tissue damage and worsened functional outcome. Raised ITP is caused by the accumulation of blood and/or water (edema), and while their occurrence after traumatic SCI has been well established, the relative contribution of both processes to the development of ITP after SCI has not yet been determined. Accordingly, the current study investigates the temporal profile of raised ITP after traumatic SCI in relation to both hemorrhage and edema development. A closed balloon compression injury was induced at T10 in New Zealand White rabbits. Animals were thereafter assessed for spinal water content (edema), ITP, lesion and hemorrhage volume, and albumin immunoreactivity from 5 h to 1 week post-SCI. Early increases in ITP at 5 h post-injury were associated with significant increases in blood volume. ITP, however, was maximal at 3 days post-SCI, at which time there was an associated significant increase in edema that persisted for 1 week. We conclude that raised ITP after traumatic SCI is initially driven by volumetric increases in hemorrhage, while edema becomes the primary driver of ITP at 3 days post-injury.

NK1 receptor blockade is ineffective in improving outcome following a balloon compression model of spinal cord injury

The neuropeptide substance P (SP) is a well-known mediator of neurogenic inflammation following a variety of CNS disorders. Indeed, inhibition of SP through antagonism of its receptor, the tachykinin NK1 receptor, has been shown to be beneficial following both traumatic brain injury and stroke. Such studies demonstrated that administration of an NK1 receptor antagonist reduced blood-brain-barrier permeability, edema development and improved functional outcome. Furthermore, our recent studies have demonstrated a potential role for SP in mediating neurogenic inflammation following traumatic spinal cord injury (SCI). Accordingly, the present study investigates whether inhibition of SP may similarly play a neuroprotective role following traumatic SCI. A closed balloon compression injury was induced at T10 in New Zealand White rabbits. At 30 minutes post-injury an NK1 receptor antagonist was administered intravenously. Animals were thereafter assessed for blood spinal cord barrier (BSCB) permeability, spinal water content (edema), intrathecal pressure (ITP), and histological and functional outcome from 5 hours to 2 weeks post-SCI. Administration of an NK1 receptor antagonist was not effective in reducing BSCB permeability, edema, ITP, or functional deficits following SCI. We conclude that SP mediated neurogenic inflammation does not seem to play a major role in BSCB disruption, edema development and consequential tissue damage seen in acute traumatic SCI. Rather it is likely that the severe primary insult and subsequent hemorrhage may be the key contributing factors to ongoing SCI injury.

Substance P as a mediator of neurogenic inflammation after balloon compression induced spinal cord injury

Although clinical spinal cord injury (SCI) occurs within a closed environment, most experimental models of SCI create an open injury. Such an open environment precludes the measurement of intrathecal pressure (ITP), whose increase after SCI has been linked to the development of greater tissue damage and functional deficits. Raised ITP may be potentiated by edema, which we have recently shown to be associated with substance P (SP) induced neurogenic inflammation in both traumatic brain injury and stroke. The present study investigates whether SP plays a similar role as a mediator of neurogenic inflammation after SCI. A closed balloon compression injury was induced at T10 in New Zealand white rabbits. Animals were thereafter assessed for blood spinal cord barrier (BSCB) permeability, edema, ITP, histological outcome, and functional outcome from 5 h to 2 weeks post-SCI. The balloon compression model produced significant increases in BSCB permeability, edema, and ITP along with significant functional deficits that persisted for 2 weeks. Histological assessment demonstrated decreased SP immunoreactivity in the injured spinal cord while NK1 receptor immunoreactivity initially increased before returning to sham levels. In addition, aquaporin 4 immunoreactivity increased early post-SCI, implicating this water channel in the development of edema after SCI. The changes described in the present study support a role for SP as a mediator of neurogenic inflammation after SCI.

Spinal cord contusion models

Most human spinal cord injuries involve contusions of the spinal cord. Many investigators have long used weight-drop contusion animal models to study the pathophysiology and genetic responses of spinal cord injury. All spinal cord injury therapies tested to date in clinical trial were validated in such models. In recent years, the trend has been towards use of rats for spinal cord injury studies. The MASCIS Impactor is a well-standardized rat spinal cord contusion model that produces very consistent graded spinal cord damage that linearly predicts 24-h lesion volumes, 6-week white matter sparing, and locomotor recovery in rats. All aspects of the model, including anesthesia for male and female rats, age rather than body weight criteria, and arterial blood gases were empirically selected to enhance the consistency of injury.

Disturbances of cerebrospinal fluid flow attributable to arachnoid scarring cause interstitial edema of the cat spinal cord

OBJECTIVE

Spinal arachnoid scarring may be caused by trauma, inflammation, surgery, spinal instability, degenerative diseases, or malformations and may lead to progressive neurological deficits and syringomyelia. We wanted to investigate the effects of focal arachnoid scarring in the cervical spinal canal of cats on pressures in the subarachnoid space and spinal cord tissue, as well as on spinal cord histological features.

METHODS

Twenty-nine adult cats were used for this study. Nine animals served as control animals, whereas 20 animals received a focal arachnoid scar at C1-C2, which was produced by placement of a kaolin-soaked fibrin sponge on the posterior surface of the spinal cord. After 4 months, pressure recordings above and below the scar, in the subarachnoid space and spinal cord, were performed. Elasticity measurements were performed with small bolus injections. Morphometric analyses of brain and ventricle volumes, sizes of the central canal, and sizes of the perivascular spaces in gray and white matter were also performed.

RESULTS

No animal developed clinical or neurophysiological evidence of neurological symptoms at any time. In the kaolin-treated group, pressure recordings revealed a significant increase in the subarachnoid pressure at C1, because of the cerebrospinal fluid flow obstruction. Pressure gradients tended to increase at all measuring points. A significant difference was detected between the spinal cord and subarachnoid space at C2, where the intramedullary pressure exceeded the subarachnoid pressure. Elasticity was significantly increased in the spinal cord at C2. Intracranially, no evidence of hydrocephalus was observed. In the spinal cord, perivascular spaces were significantly enlarged in the posterior white matter above the arachnoid scar and in the central gray matter below the area of scarring in the cervical cord.

CONCLUSION

Arachnoid scarring at C1-C2 produces an interstitial type of edema in the central gray matter below the area of scarring in the cat cervical cord, because of altered cerebrospinal fluid and extracellular fluid flow dynamics. These changes may be interpreted as the initial stage in the development of syringomyelic cavities.

The prognostic impact of prior low grade histology in patients with anaplastic gliomas: a case-control study

At the time of recurrence, the majority of low-grade cerebral gliomas transform to a higher grade of histologic malignancy. The purpose of this study was to determine the survival outcome for patients whose anaplastic gliomas began as low-grade tumors compared with patients with de novo high-grade gliomas. Seventy-seven (11.5%) of 667 patients with anaplastic gliomas consecutively treated at the University of Alabama at Birmingham had histologically proven prior low-grade tumors. As a group, the patients with prior low-grade tumors would be expected to have a relatively favorable outcome, as they were younger and had a lower proportion of glioblastoma multiforme than the patients with de novo anaplastic gliomas. The provide a valid comparison, we performed a matched case-control study. We matched 68 patients from the prior low-grade group one-to-one with patients from de novo group for tumor histology, age, Karnofsky performance scores, and type of surgery, without knowledge of outcome. The two groups received comparable radiotherapy and chemotherapy. For the 68 patients with prior low-grade tumor, median actuarial survival from the time of diagnosis of malignant degeneration was 19.7 months and the 5-year survival rate was 22%, compared with 22.0 months and 28% for the 68 matched de novo patients. Kaplan-Meier survival curves for the two group did not significantly differ (p = 0.24 by logrank test). There were no significant survival differences between the patient subsets of prior low-grade versus de novo with glioblastoma, anaplastic astrocytoma, or anaplastic oligodendroglioma/mixed anaplastic glioma. The data indicate that the currently available treatment options, the survival outlook for patients with anaplastic gliomas, whose tumors arose from transformation of low-grade gliomas, is equivalent to the prognosis for patients with de novo anaplastic gliomas.

Effect of U-50488h, a selective opioid kappa receptor agonist, on vascular injury after spinal cord trauma

U-50488H, a selective opioid kappa receptor agonist has been shown to be a neuroprotective agent in animal models of spinal cord injury. The mechanism of action of U-50488H is not known. Methylprednisolone, the only neuroprotective drug proven in patients with acute spinal cord injury may prevent the secondary injury after an initial trauma. Secondary vascular injury develops after experimental spinal cord trauma. In this study we examined the effects of U-50488H on post-traumatic vascular injury based on the measurement of vascular permeability, edema and neutrophil infiltration in a rat spinal cord injury model. Vascular permeability was assessed by vascular extravasation of fluorescein isothiocyanate conjugated dextran (FITC-D), a macromolecular tracer. Tissue edema was determined by percentage water content and neutrophil infiltration by myeloperoxidase (MPO) activity, a marker enzyme for neutrophils. U-50488H at doses of 5, 10, 20 and 40 mg/kg i.p. administered twice (0.5 h before and 0.5 h after trauma) reduced vascular permeability in a dose-dependent manner. More frequent dosing (10 mg/kg, 0.5 h before and 0.5, 2, 8 and 22 h after injury) reduced vascular permeability 24 h after injury. U-50488H also reduced edema formation but did not affect neutrophil infiltration. Results from this study raise the possibility that the neuroprotective effect of U-50488H involves a secondary vascular event.

Spinal cord oedema due to venous stasis

Venous hypertension and stagnant hypoxia in the human spinal cord are poorly understood. We report a case in which a partial Brown-Séquard syndrome resulted from obstruction of venous drainage on one side of the spinal cord. Neurological deterioration and eventual recovery paralleled the formation and clearance of oedema. The clinical and MRI findings support the contention that spinal cord injury arising as a result of obstruction to venous outflow occurs primarily in the white matter, spreading secondarily to the grey matter, and observations that obstruction of venous flow in the high cervical spinal cord results in changes in the lower cervical cord.

Kininogen and kinin in experimental spinal cord injury

Activation of the kallikrein-kinin system has been implicated in the pathogenesis of vasogenic brain edema and posttraumatic vascular injury. We determined the levels of kininogen and kinin in an experimental spinal cord injury model in the rat. Kininogen content in traumatized cord segments increased in a time-dependent manner. Western blot analysis showed that the kininogen in traumatized cord comigrates with 68K low-molecular-weight kininogen or T-kininogen. Trypsin treatment of the kininogen in traumatized cord released both bradykinin and T-kinin, which were separated by HPLC and quantified with a kinin radioimmunoassay. Endogenous kinin levels in the frozen spinal cord also increased up to 40-fold 2 h after injury as compared with controls. The results demonstrate an increased accumulation of kininogen and its conversion to vasoactive kinins in experimental spinal cord injury.

Evaluation of traumatic spinal cord edema using evoked potentials recorded from the spinal epidural space. An experimental study in the rat

Spinal cord evoked potentials (SCEP) elicited by simultaneous distal tibial and sural nerve stimulation were continuously recorded from the epidural space at the T9 and T12 levels of urethane anaesthetized rats before and after a unilateral incision (about 3 mm deep and 5 mm long) in the right dorsal horn of the T10-11 segments. The changes in SCEP were correlated with the increase in spinal cord water content measured 5 h after injury. In addition, the influence of serotonin (5-HT) in mediating such changes was explored using a pharmacological approach. The changes in SCEP immediately after injury correlated well with development of spinal cord edema measured 5 h after injury. Thus, the maximal negative peak (MNP) amplitude of SCEP decreased by an average of 64.0% immediately after injury and the water content of the spinal cord was increased from 71.6% (controls) to 77.6% 5 h after injury. Pretreatment with p-CPA (a serotonin synthesis inhibitor) prevented the initial decrease of the MNP amplitude and also the increase of water content (72.5%). On the other hand, pretreatment with cyproheptadine (a 5-HT2 receptor antagonist) enhanced both the initial decrease of the MNP amplitude as well as the increase of water content (81.3%). The results show a good correlation between changes of SCEP immediately after injury and the magnitude of spinal cord edema (r = 0.9) measured 5 h after injury. The findings reveal a major role of serotonin in mediating early changes of SCEP and later development of spinal cord edema and demonstrate a prognostic value of early SCEP recordings in predicting the final outcome of traumatic spinal cord injuries.

Lipid alterations correlate with tissue magnesium decrease following impact trauma in rabbit spinal cord

Secondary neurochemical events contribute to progressive tissue damage and subsequent neurological deficit after traumatic spinal-cord injury (SCI). Among proposed injury factors are alterations of phospholipids and certain cations. To clarify the relationship of membrane lipid changes (phospholipids, cholesterol, and arachidonic acid) to changes in tissue content of water and selected ions (sodium, potassium, and magnesium) after SCI, these variables were examined in spinal-cord segments from anesthetized ventilated rabbits subjected to laminectomy or to moderate (40 g-cm) or severe (150 g-cm) impact trauma at the lumbar (L2) segment. Trauma caused significant increases in tissue sodium, water, and arachidonic acid content, and significant decreases in phospholipids, cholesterol, potassium, and magnesium content. Alterations in magnesium were significantly related to injury severity. In contrast, changes in spinal-cord water content occurred to a similar degree in the two injury groups, as did tissue sodium and potassium content. Decreases in phospholipids were strongly correlated with decreases in tissue magnesium content, whereas changes in sodium and potassium were less well-correlated. Because magnesium ions play a critical role with regard to cellular bioenergetic state, calcium flux, amino acid receptor function, and eicosanoid production, reductions in tissue magnesium after injury may be important in the progression of secondary tissue damage.

Increased 5-hydroxytryptamine immunoreactivity in traumatized spinal cord. An experimental study in the rat

The possibility that serotonin (5-hydroxytryptamine, 5-HT) is involved in the early tissue reactions occurring in spinal cord trauma was examined in a rat model using an immunocytochemical technique. The injury was made in the form of a 5-mm long and 2.5-mm wide lesion of the right dorsal horn at the level of T10-11. Injured rats, pretreated with the 5-HT synthesis blocking agent, p-chlorophenyl alanine (p-CPA) were compared with untreated injured controls and the animals were allowed to survive for 5 h. The distribution of 5-HT was examined in proximal and distal cross- sections of the cord, located 2 and 5 mm away from the injury. Normal rats showed immunoreactive material in nerve cell processes and in a few nerve cell bodies of the ventral horns. The trauma to the spinal cord caused a marked increase in 5-HT immunoreactivity in the segments located 2 mm proximal and distal to the injury, particularly in the ipsilateral ventral horn. The segment located 5 mm distal to the lesion showed a similar increase in immunoreactivity but it was apparently less pronounced in the corresponding proximal segment. Treatment with p-CPA markedly reduced the trauma-induced increase in 5-HT immunoreactivity in all the segments. These immunohistochemical findings were in line with the changes in the contents of 5-HT measured biochemically in corresponding spinal cord segments. At the onset of the trauma to the spinal cord 5-HT is thus present in the tissue, mainly in the form of 5-HT-containing nerve cell processes.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of p-chlorophenylalanine on microvascular permeability changes in spinal cord trauma. An experimental study in the rat using 131I-sodium and lanthanum tracers

The possibility that serotonin can take part in the initiation of the increased microvascular permeability occurring in a spinal cord trauma was investigated in a rat model with 131I-sodium and lanthanum as tracers. We influenced the serotonin content in the tissue pharmacologically by treating animals with a serotonin synthesis inhibitor, p-chlorophenylalanine (p-CPA), before the production of the injury and compared the results with injured, untreated controls. A small incision was made in the dorsal horn of the lower thoracic cord. It caused a progressive extravasation of 131I-sodium in the damaged segment, measured after 1, 2 and 5 h. Rostral and caudal segments also showed a significant but lower accumulation of 131I-sodium. Lanthanum added to the fixative was used as an ionic tracer detectable by electron microscopy. The endothelial cells of microvessels removed from the perifocal region after 5 h showed a marked increase in the number of lanthanum-filled vesicles. Many endothelial cells had a diffuse penetration of the tracer into the cytoplasm and the basement membrane. However, the tight junctions usually remained closed to lanthanum. Pretreatment with p-CPA markedly reduced the extravasation of 131I-sodium measured at 5 h in the traumatized cord. At the cellular level, the endothelial vesicles filled with lanthanum approached the condition of uninjured animals. The diffuse infiltration of lanthanum into endothelial cells and its spread into the basement membrane of the vascular wall were usually absent. Our results indicate that serotonin plays a role in the initiation of the increased microvascular permeability which occurs in spinal cord injuries.

Edema formation and cellular alterations following spinal cord injury in the rat and their modification with p-chlorophenylalanine

The possibility that serotonin can modify the early pathological sequences occurring in spinal cord trauma was investigated in a rat model. To that end we took advantage of the possibility of influencing serotonin pharmacologically by treating animals with a serotonin synthesis inhibitor, p-chlorophenylalanine (p-CPA) before the production of the injury and compared the results with injured, untreated controls. A unilateral incision was made into the dorsal horn of the lower thoracic cord (about 2.5 mm deep, 4.5 mm long) and the rats were allowed to survive up to 5 h after the trauma. The injured region from untreated animals showed macroscopically at that time a pronounced swelling and the water content had increased by 3.5% as compared to intact controls. The segments rostral and caudal to the lesion also exhibited a profound increase in water content. Light microscopy revealed a significant expansion of the spinal cord as compared to controls. The swelling was most pronounced in the gray matter on the injured side. Electron microscopy showed distorted neurons, swollen astrocytes and extracellular edema in the gray matter in and around the primary lesion. There was also a sponginess in the surrounding white matter with disruption of myelin, collapsed axons and widened periaxonal spaces. Pretreatment of the rats with p-CPA significantly reduced the swelling of the injured spinal cord and there was no visible expansion. The ipsilateral edema in the central gray matter was considerable less pronounced as compared to that in untreated animals. The increase in water content was less than 1% in these animals.(ABSTRACT TRUNCATED AT 250 WORDS)

Early accumulation of serotonin in rat spinal cord subjected to traumatic injury. Relation to edema and blood flow changes

Changes in the concentration of serotonin (5-hydroxytryptamine) in the early period after a focal traumatic injury to rat spinal cord were determined and related to the formation of edema and alterations in blood flow. A unilateral, 5-mm-long and 3-mm-deep traumatic injury located 2 mm from the midline was created in the T10-11 segment of the cord. Five hours after the injury the serotonin concentration in the traumatized segment had increased more than 100% compared with controls. There was also a progressive increase in water content of the traumatized segment measured 1-5 h after the injury. On the other hand, the spinal cord blood flow showed a progressive decrease to about 35% of its initial value at 5 h. Pretreatment with p-chlorophenylalanine, a serotonin synthesis inhibitor, impeded the elevation in water content measured 5 h after the trauma. The spinal cord blood flow remained close to normal values and the increase in serotonin was absent. Our results show that trauma to the rat spinal cord will induce changes in the serotonin concentration of the tissue and that the associated formation of edema and blood flow alterations can be alleviated in serotonin depleted rats. Obviously, serotonin plays a significant role in the pathophysiology of traumatic injury of rat spinal cord.

Edema development and ion changes in rat spinal cord after impact trauma: injury dose-response studies

Changes in the total tissue content of water, sodium, potassium, and magnesium were measured in spinal cord from pentobarbital-anesthetized rats subjected to impact trauma (T9) of varying severity (low, 25 g-cm; moderate, 50 g-cm; severe, 100 g-cm). Laminectomized animals served as controls. Spinal cord samples were taken from rats in the high injury group at 15 min, 60 min, 4 hr, 24 hr, 3 days, or 7 days posttrauma. Samples from the low and moderate injury groups were taken at 24 hr postinjury. In all groups, spinal cord tissue was rapidly removed (less than 30 sec), frozen in liquid N2, and dissected into the injured segment and adjacent two caudal and rostral segments. Severe injury caused significant increases in tissue water content; changes were present at 15 min, peaked at 24 hr, and continued at 3-7 days. Sodium levels were increased at 4 hr and remained elevated for up to 7 days. Potassium levels were decreased at 60 min, remained at low levels for up to 3 days, and partially recovered at 7 days. Tissue magnesium levels were significantly decreased only at 4 hr and 24 hr. Changes in water content and total sodium at 24 hr were not correlated with injury severity. Although potassium decreases did correlate with injury severity, alterations in magnesium levels had a much higher degree of correlation. Thus, reductions in magnesium content may contribute to the development of irreversible tissue damage. In contrast, edema formation after spinal cord trauma may be an epiphenomenon, since it was found to an equal degree in low, moderate, and severe injuries.

Effect of impact trauma on neurotransmitter and nonneurotransmitter amino acids in rat spinal cord

N-Methyl-D-aspartate (NMDA) administration exacerbates neurological dysfunction after traumatic spinal cord injury in rats, whereas NMDA antagonists improve outcome in this model. These observations suggest that release of excitatory amino acids contributes to secondary tissue damage after traumatic spinal cord injury. To further examine this hypothesis, concentrations of free amino acids were measured in spinal cord samples from anesthetized rats subjected to various degrees of impact trauma to the T9 spinal segment. Levels of excitatory and inhibitory neurotransmitter amino acids [gamma-aminobutyric acid (GABA), glutamate, aspartate, glycine, taurine] and levels of nonneurotransmitter amino acids (asparagine, glutamine, alanine, threonine, serine) were determined at 5 min, 4 h, and 24 h posttrauma. Uninjured surgical (laminectomy) control animals showed modest but significant declines in aspartate and glutamate levels, but not in other amino acids, at all time points. In injured animals, the excitatory amino acids glutamate and aspartate were significantly decreased by 5 min posttrauma, and remained depressed at 4 h and 24 h as compared with corresponding laminectomy controls. In contrast, the inhibitory amino acids, glycine, GABA, and taurine, were decreased at 5 min postinjury, had partially recovered at 4 h, and were almost fully recovered at 24 h. The nonneurotransmitter amino acids were unchanged at 5 min posttrauma and significantly increased at 4 h, with partial recovery at 24 h. At 4 h postinjury, severe trauma caused significantly greater decreases in aspartate and glutamate than did either mild or moderate injury. These findings are consistent with the postulated role of excitatory amino acids in CNS trauma.

A potential role for excitotoxins in the pathophysiology of spinal cord injury

It has been proposed that endogenously released excitatory amino acids may contribute to injury of the central nervous system in a variety of disorders including certain neurodegenerative diseases, epilepsy, and cerebral ischemia. In the present studies we evaluated the hypothesis that excitatory amino acids, acting at the N-methyl-D-aspartate (NMDA) receptor, contribute to secondary tissue damage following traumatic spinal cord injury. Administration of NMDA, adjacent to the trauma site, significantly worsened the outcome after thoracic cord injury in rats, whereas its stereoisomer, N-methyl-L-aspartate (NMLA), was without effect. Systemic treatment with MK-801--a selective, centrally active, NMDA antagonist--significantly improved neurological outcome after trauma. These findings extend the excitotoxin concept to central nervous system trauma and indicate that NMDA antagonists may be beneficial in the treatment of traumatic spinal cord injury.

Alterations in tissue Mg++, Na+ and spinal cord edema following impact trauma in rats

Alterations in water content and total tissue Na+ and Mg++ of rat spinal cord tissue were followed over time after a 100 g-cm impact injury to the T-9 spinal cord segment. Rats subjected to laminectomy but not trauma served as controls. In the injured segment there was a progressive increase in water content with increased Na+ and decreased Mg++ at 1 hour and 24 hours after trauma. At seven days, water and Na+ content remained elevated, whereas Mg++ levels had returned to preinjury baseline values. Because of its important role in many metabolic and physiological regulatory processes the early decline in Mg++ concentration after trauma may contribute to the development of secondary tissue damage after spinal cord injury.

Alterations in lipid metabolism, Na+,K+-ATPase activity, and tissue water content of spinal cord following experimental traumatic injury

Traumatic spinal cord injury has recently been shown to cause a rapid increase in free fatty acids (FFAs) and lipid degradation in cats. The present studies report a more delayed, time-dependent increase in FFAs and a concomitant decrease in phospholipids following traumatic spinal injury in rats. The largest percentage increases were found for polyunsaturated fatty acids, particularly arachidonic acid. Associated with these changes were a reduction in the activity of Na+,K+-ATPase and development of spinal cord edema. These findings support the hypothesis that traumatic spinal cord injury leads to delayed, as well as early, hydrolysis of membrane phospholipids, resulting in the liberation of FFAs. Such changes may contribute to secondary spinal cord injury either through direct effects on membranes or through the actions of secondary metabolic products such as the eicosanoids. The latter may cause tissue injury by contributing to the reduction in spinal cord blood flow or through inflammatory responses that follow trauma.

Proteolytic enzymes in experimental spinal cord injury

Experimental spinal cord injury was produced in rats by dropping a 10 g weight from 30 cm upon dura-invested exposed spinal cord. Proteolytic activities at neutral (pH 7.6) and acid (pH 5.5 and 3.6) pH were determined in whole homogenate and the cytosolic fraction of the lesion (lumbar) and cervical control segments. The enzyme activity was monitored by SDS-PAGE analysis of the extent of substrate myelin basic protein (MBP) degradation. Activities (neutral and cathepsin B-like) in the sham-operated spinal cord were lower than those of cervical autologous control at 24 h after injury. The increase in neutral proteinase activity was progressive and greater in the lesion than the autologous control. A 61.5% +/- 3.5 loss of MBP was observed at 2 h following injury and increased at 24 h (78.2% +/- 3.4). The loss of MBP coincided with the appearance of several low molecular weight peptides. The cathepsin B-like and cathepsin D activities were also increased in the lesion but to a lesser extent than the neutral proteinase. The neutral proteinase and cathepsin B-like activity were inhibited by leupeptin and not by pepstatin while the converse obtained for cathepsin D activity. The release of neutral proteolytic activity which is nonlysosomal in origin suggests a novel hypothesis for the mechanism of traumatic axon-myelin injury.

Potassium and calcium changes in injured spinal cords

In previous studies, we found large rises in extracellular potassium activity ([K+]e) and falls in extracellular Ca2+ activity ([Ca2+]e) in injured spinal cords. [K+]e recovered rapidly at the impact site within 2 h but ischemia onset at 2-3 h paradoxically did not cause further [K+]e rises. [Ca2+]e, in contrast, remained depressed for long periods of time, suggesting either an effective block of Ca diffusion to the injury site or a deep Ca2+ sink at the impact site. To resolve questions raised by the [K+]e and [Ca2+]e recovery patterns, we used atomic absorption spectroscopy to measure spatial distributions of tissue concentrations of K ([K]t) and Ca ([Ca]t) in cat spinal cords injured by a standardized contusion, compared with uninjured controls. At the impact site, [K]t fell to 51% and 35% of control at 1 and 3 h. The K content of cord surrounding the impact site did not change significantly at 1 h, but K gains in surrounding cord at 3 h approximated K losses from the impact site. The K results indicate that contusion disrupts greater than 80% of cells at the impact site with K loss to adjacent cord, blood, and cerebrospinal fluid. Such losses may explain why subsequent ischemia at the impact site did not cause [K+]e rises. [Ca]t at the impact site increased to 37% and 59% above control at 1 and 3 h. The Ca gain at the impact site exceeded the amount of free extracellular Ca2+ available before injury within 2 cm of the impact site. At 1 h, the Ca lost in cord surrounding the impact site approximated the Ca gain at the impact site. These findings indicate that Ca accumulated at the impact site comes largely from surrounding cord. We propose that Ca sequestration by inorganic phosphates causes a deep Ca sink at the impact site.

Spinal cord edema, 5-hydroxytryptamine, lipid peroxidation, and lysosomal enzyme release after acute contusion and compression injury in primates

Physical and biochemical changes in the spinal cord of monkeys at 1/2, 2, and 4 hours following 200 g cm contusion injury and 50 g of compression injury and 2 hours of decompression following 4 hours of compression were studied. The pathophysiologic changes were milder in compression compared to contusion injury. Following contusion injury, at 1/2 and 2 hours there was significant increase in % water content, lipid peroxidation, and alpha-L-fucosidase. alpha-D-Mannosidase was significantly increased at all time periods, and beta-D-hexosaminidase was increased at 1/2 and 4 hours. At 4 hours following injury, serotonin (5 HT) and 5-hydroxyindole-3-acetic acid (5-HIAA) showed a significant increase. From 10 minutes to 2 hours there was increased platelet aggregation. In compression injury, a significant increase in water content and 5 HT was observed only at 1/2 hour. Lipid peroxidation had increased at all time periods, whereas B-D-hexosaminidase, beta-D-galactosidase, and 5-HIAA were increased at 2 hours. alpha-D-Mannosidase had increased at 1/2 and 2 hours, and alpha-L-fucosidase had increased at 4 hours. After 2 hours decompression following 4 hours compression, water content, beta-D-galactosidase, and alpha-D-Mannosidase were significantly increased. An attempt was made to correlate the findings and to understand the sequential pathophysiologic changes in the first 4 hours following spinal cord trauma, providing a baseline for evaluation of the efficacy of any therapeutic maneuvers.

Effect of trauma dose on spinal cord edema

The spinal cord of anesthetized cats was subjected to impact trauma of different intensities to determine how changes in trauma magnitude affect the formation and distribution of edema. All animals underwent a laminectomy to expose the cord segments corresponding to the T5--7 vertebrae. Fourteen cats were injected with fluorescein-labeled albumin, and then subjected to 260, 360, 500, or 700 gm-cm injury to the spinal cord. They were sacrificed at 8 hours after trauma. Twelve cats were injected with fluorescein-labeled dextrans of 20,000, 40,000, 70,000, or 150,000 molecular weight (MW) prior to 500 gm-cm injury, and sacrificed 8 hours after trauma. Serial cord sections from both groups were studied by fluorescence microscopy. In nine cats, sections of cord were removed 8 hours after trauma of 260, 360, or 500 gm-cm impact, and 1-cm sections were assayed for dry weight. Extravasated tracers were present in areas of hemorrhage at the site of impact in all animals. Extension of tracers and increases in tissue water rostrally and caudally from the site of impact were observed consistently with time only in animals receiving 500 or 700 gm-cm trauma. The distance of migration was similar for all tracers. The longitudinal distribution of increased tissue water was consistent with the distribution of fluorescein markers. The findings indicate that the longitudinal extension of posttraumatic edema is directly related to the amount of initial trauma.

Serotonin in contused spinal cord

An intensive experimental spinal cord impact trauma in rabbits led, after 90 minutes, to a significant increase of serotonin content in the segments of spinal cord at the injury epicentres. Adjacent segments showed normal values. It is suggested that the existing contradictory published data concerning the serotonin concentration in a traumatized spinal cord are accounted for by differences between animal species, the method of analysis used, and the technique employed in causing the injury. Potential involvement of serotonin in the autodestructive process is discussed.