Response of lysosomal hydrolases of dog spinal cord and cerebrospinal fluid to experimental trauma

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.

Characterization of axonal ultrastructural pathology following experimental spinal cord compression injury

The present study characterizes axonal pathology associated with traumatic compression injuries of the spinal cord and quantitatively assesses subtypes of axonal pathology in the acute, post-injury period. Eighteen adult female Wistar rats underwent spinal cord compression injury with a 53 g modified aneurysm clip at the C8-T1 segment. Six additional rats served as sham controls. Six experimental animals were sacrificed at each of the three post-injury time points: 15 min, 2 h and 24 h. From all animals, the C8-T1 spinal cord was dissected and processed for both light and electron microscopy. Axonal pathology included periaxonal swelling, organelle accumulation, vesicular myelin, myelin invagination, myelin rupture, and giant axons. Early myelin rupture and the ultrastructural features of giant axons are described here for the first time in the context of spinal cord compression injury. The quantitative analysis characterizes the prevalence of types of axonal pathology over the acute post-injury period and provides evidence for the secondary injury hypothesis regarding the evolution of axonal pathophysiology following trauma.

The effect of the treatment of high-dose methylprednisolone on Na(+)-K(+)/Mg(+2) ATPase activity and lipid peroxidation and ultrastructural findings following cerebral contusion in rat

BACKGROUND

Although use of corticosteroid in the management of head trauma has caused a great deal of controversy, corticosteroids have long been an adjunct in the management of severe closed head injury. The glucocorticoid steroid methylprednisolone (MP) has been proven to have significant antioxidant effect when administered in an antioxidant-high dose after central nervous system injury.

METHODS

The sodium-potassium activated and magnesium dependent adenosine-5'-triphosphatase (Na(+)-K(+)/Mg(+2) ATPase EC.3.6.1.3.) activity, lipid peroxidation, and early ultrastructural findings were determined during the immediate posttraumatic period in rats. Mechanical brain injury was produced when a calibrated weight-drop device is allowed to fall on the skull's convexity over the right hemisphere, 1 to 2 mm lateral from the midline. In group I, rats were used to determine Na(+)-K(+)/Mg(+2) ATPase activity, the extent of lipid peroxidation, by measuring the level of malondialdehyde content and normal ultrastructural findings in two different brain areas (cerebral cortex and brain stem). In group II, physiologic saline was administered right after trauma in the same amount as methylprednisolone. In group III rats, methylprednisolone (30 mg/kg) was administered intravenously right after trauma.

RESULTS

Na(+)-K(+)/Mg(+2) ATPase activity significantly decreased in the cerebral cortex and in brain stem within 2 hours after trauma (p < 0.05). There was significant difference in malondialdehyde content between groups II and III (p < 0.05). Methylprednisolone treatment reduced malondialdehyde content and induced the recovery of Na(+)-K(+)/Mg(+2) activity.

CONCLUSIONS

These data suggest that inactivation of Na(+)-K(+)/Mg(+2) ATPase is closely correlated to changes of lipid peroxidation and the alteration of the ultrastructural findings in the early phases after head trauma. The glucocorticoid steroid methylprednisolone has been proven to have significant effect in activation of Na(+)-K(+)/Mg(+2) ATPase with significant reduction of malondialdehyde content.

[Anesthesia of patients with injury to the cervical spine]

This paper reviews the principal aspects of the immediate management of patients suffering from spinal injury. An understanding of the pathophysiology of primary and secondary spinal cord injury enables appropriate initial care to be provided, thereby avoiding exacerbation and/or progressive deterioration of the lesion. It includes protective measures, restoration of vital functions to maintain adequate tissue perfusion and oxygenation, as well as pharmacological prevention of secondary injury. Protective measures include proper immobilisation of the spine with a semi-rigid collar and tape on a long backboard, or on vacuum mattress, taking great care to avoid deleterious in-line compression forces on the spinal column. The combination of cervical spine instability, a full stomach, unopposed vagal reflexes, hypoxia and hypercarbia makes airway management of these patients difficult. Tracheal intubation under fibroscopic control, with insertion of the tube only after topical anaesthesia of the airways under titrated intravenous sedation, offers safety and comfort to the patient. However, in cases of severe deterioration of vital functions, intubation must be performed without any delay at the site of the accident or in the emergency room. Three options are available: blind naso-tracheal intubation with spontaneous breathing, modified rapid sequence induction with orotracheal intubation under double protection, and immediate surgical airway if these techniques fail. Patients with cervical spine injury may demonstrate severe hypotension requiring sympathomimetic agents and careful fluid loading to avoid pulmonary oedema. To prevent aggravation of the spinal cord injury by systemic factors, the goal of initial resuscitation is to restore an adequate perfusion pressure of at least 60 mmHg, a PaO2 > 100 mmHg, and to keep PaCO2 below 45 mmHg.(ABSTRACT TRUNCATED AT 250 WORDS)

Evolution of tissue damage in compressive spinal cord injury in rats

The evolution of tissue damage in compressive spinal cord injuries in rats was studied using an immunohistochemical technique and by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis. The rupture of small vessels accompanied by intense tissue permeation of serum components in and around the hemorrhagic foci appeared to be immediate consequences of the mechanical insult. The loss of cell membrane integrity in neural elements became evident within 1 hour after injury as shown by the diffuse albumin-immunoreactivity of the cytoplasm. At the site of mechanical insult, approximately 30% of the neurofilament proteins were degraded within 1 hour, and 70% of them were lost within 4 hours after injury. A large number of cells positive for glial fibrillary acidic protein were found to demarcate the injured tissue within 1 hour after injury. The progression of tissue damage largely subsided within 48 hours. One week after injury, severe degeneration of the ascending tracts in the posterior funiculus was shown clearly by axon staining and less convincingly by myelin staining. Secondary degeneration of the corticospinal tract in distal segments remained inconspicuous for up to 3 months.

Mono- and diacylglycerol lipases in spinal cord of lean and obese Zucker rats

1. Genetically obese Zucker rats (fa/fa) contain 2-3 times higher activities mono- and diacylglycerol lipases in their spinal cords than their lean littermates. 2. When rats were exercised (1 hr daily, 5 days/week) on a treadmill for 6 months, there was a decrease of about 30% (P less than 0.05) in the activities of mono- and diacylglycerol lipases in lean rats but not in obese animals. 3. High activities of lipases in Zucker obese rats may be related to the elevated levels of beta-endorphin present in these animals. 4. The activities of arylsulfatase, beta-N-acetylhexosaminidase and alkaline phosphatase, tested to check the stability of spinal cord extracts, were similar in lean and obese rat spinal cords.

The post-injury responses in trauma and ischemia: secondary injury or protective mechanisms?

Transient injuries to the central nervous system, whether due to trauma or ischemia, often produce long lasting metabolic derangements, lipid peroxidation, edema, and falls in blood flow at the lesion site. Because these post-injury responses are believed to be causes of secondary injury, much research effort has been devoted to developing therapies that prevent them. Recent studies suggest that excessive Ca entry into injured cells instigates these post-injury responses. A new theory is proposed to explain these post-injury responses. This theory posits that Ca ions entering dying cells activate phospholipases that break down membranes to release phosphates. The phosphates then bind and precipitate Ca ions, producing the profound and prolonged decreases in extracellular Ca activity that have been observed in traumatized spinal cords and ischemic brains. The phospholipase activity also facilitates release of lipid peroxides which enhance edema and reduce blood flow. Both of these in turn decrease Ca diffusion to the lesion site and slow the recovery of extracellular Ca activity, giving the tissue time to recover and avoiding the consequences of rapid restoration of extracellular Ca activity. The theory suggests that central nervous tissues evolved these Ca-activated responses as a general mechanism to protect neurons against excessive Ca entry. Brain and spinal cord tissues contain very high concentrations of phosphates, many times greater than is necessary to bind all the Ca ions in the tissues. This excessive Ca buffering capacity enables the tissue to sacrifice a small proportion of severely injured cells to reduce Ca entry into less severely injured neurons. This process will also rapidly eliminate moribund cells that may otherwise linger and consume oxygen and metabolic substrates better utilized by the remaining cells. If confirmed, this theory raises serious questions concerning the current experimental therapeutic approaches to CNS trauma and stroke. Therapy should perhaps be designed to optimize rather than to abort the post-injury responses.

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.

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.

The therapeutic effects of drugs in injured central nervous system

A variety of physiologic, neurochemical, and morphologic sequelae have been either shown or postulated to result from spinal cord injury, yet the actual pathophysiologic substrate that leads to the loss of neurologic function remains uncertain. Several treatment modalities have been investigated in spinal cord injury, but little consensus exists regarding their efficacy. Steroids in particular have been studied extensively with little agreement about their effects and possible mechanism of action. Recently naloxone has been found to improve neurologic function following spinal cord injury, and its effectiveness has not been challenged to date. In the past most attempts at therapy in cases of brain injury were directed at control of edema, and, consequently, clinically beneficial effects were usually ascribed to control of the edematous process. This was particularly so in the case of steroids. Currently, emphasis has shifted to the study of various neurochemical systems (eicosanoids, serotonin, catecholamines) that, independently from edema may underlie functional disturbances resulting from trauma. Much of the pertinent information derives from the use of drugs in freezing lesion models of brain injury.

Effect of high-dose corticosteroid therapy on blood flow, evoked potentials, and extracellular calcium in experimental spinal injury

High-dose methylprednisolone (15 to 30 mg/kg), administered 45 minutes after severe contusion injury (400 gm-cm) to cat spinal cords, rapidly reverses the typical posttraumatic ischemia that occurs in spinal injuries. White matter blood flow improves despite the systemic hypotension associated with bolus intravenous injections of such massive corticosteroid doses. In addition, this treatment facilitates extracellular calcium ionic recovery in contused spinal cords, and salvages evoked potential activity that is lost in untreated cats. These data suggest that high-dose corticosteroid treatment causes local vasodilation of spinal cord blood vessels. The consequent blood flow increase may account for the beneficial effects of high-dose corticosteroid treatment on both functional recovery and histopathological appearance of injured spinal cords.

Effect of methylprednisolone in compression trauma to the feline spinal cord

The purpose of this study was to determine the effect of methylprednisolone sodium succinate on clincal recovery and tissue preservation following compression trauma of feline spinal cord. Cats were anesthetized with pentobarbital and injured by placing a 170-gm weight on the spinal cord for 5 minutes. One hour after injury, the animals were given intravenous steroid (15 mg/kg/day) for 2 days in three devided doses, 15 mg/kg/day for 1 day intramuscularly, 7.5 mg/kg/day intramuscularly for 3 days, and 3.75 mg/kg/day intramuscularly for 3 days, for a total of 9 days. In a control group, the animals were injured but untreated. At 60 days after injury, the animals were sacrifieced by perfusion fixation with 10% formalin. The spinal cord was removed and evaluated for a number of morphometric parameters, including percentage of spinal cord cross-sectional area containing the cavity (%area) and percentage of spinal cord volume occupied by the cavity (%volume). A clinical recovery score (recovery index) was devised to evaluate neurological recovery. Steroid-treated cats showed significantly greater recovery than the untreated controls (p less than 0.001). Moreover, the spinal cord of treated cats displayed greater tissue preservation as measured by %area (p leass than 0.005) and %volume (p less than 0.004). Correlation coefficients comparing the recovery index with morphometric parameters revealed a negative correlation between cavity size and recovery. These data provide evidence for a beneficial effect of methylprednisolone in promoting recovery and preserving spinal cord tissue following blunt injury to the feline spinal cord.

Inhibition of Na+-K+-activated ATPase activity following experimental spinal cord trauma

The specific activity of the membrane-bound enzyme, Na+-K+-activated adenosine triphosphatase (ATPase), has been shown to be decreased following experimental impact injury (400 gm-cm) to the spinal cord in dogs. The prompt and significant (p less than 0.01) fall in activity was evident as early as 5 minutes after injury, and remained at 56% to 67% of control for the 1-hour period studied. This decrease was most prominent in the central core of the traumatized segments of spinal cord. Central core samples, excised immediately adjacent to the trauma site, gave values for the Na+-K+-activated enzyme intermediate to those of the trauma and control sites. For these same samples, the activity of the Mg+2-dependent ATPase did not change appreciably. No alterations were observed in the tissue surrounding the zone of maximum injury at these early time periods. The relationship of membrane-bound enzyme alterations to blood flow, clotting mechanisms, and abnormal free radical reactions are briefly discussed.