Animal model for sport-related concussion; ICP and cognitive function.

BACKGROUND: We have recently developed and characterized a rat model of mild traumatic brain injury which simulates the concussive injuries frequently encountered by players in American professional football. OBJECTIVES: To study the effect of multiple impacts to the head on intracranial pressure, cognitive function, and exploratory behavior. MATERIALS AND METHODS: The model was employed to cause concussion. Intracranial pressure, cognitive function, and exploratory behavior were examined following the multiple impacts of a 50 or 100 g projectile at a velocity of 9.3 or 11.2 m/s to the helmet protected head. RESULTS: Intracranial pressure measured at 6 and 10 h, and 1, 2, 3, 5, and 7 days. It was maximally elevated 10 h after impact and returned to the control levels 7 days later. Morris Water Maze assessment, 48 h after impact, revealed impaired cognitive function. Open field testing 2-4 days and 1 and 2 weeks after impacts indicated consistently reduced spontaneous exploratory activity. CONCLUSION: Multiple impacts to the head raise intracranial pressure and impair cognitive function and exploratory activity in this animal model.

Blast exposure causes redistribution of phosphorylated neurofilament subunits in neurons of the adult rat brain.

There is little information on threshold levels and critical time factors for blast exposures, although brain damage after a blast has been established both clinically and experimentally. Moreover, the cellular pathophysiology of the brain response is poorly characterized. This study employs a rat model for blast exposure to investigate effects on the neuronal cytoskeleton. Exposure in the range of 154 kPa/198 dB or 240 kPa/202 dB has previously been shown neither to cause visual damage to the brain, nor to affect the neuronal populations, as revealed with routine histology. Here, the brains were investigated immunohistochemically from 2 h to 21 days after blast exposure. A monoclonal antibody was used which detects only the phosphorylated epitope of the heavy subunit of the neurofilament proteins (p-NFH). This epitope is normally restricted to axons, that is, not demonstrable in the perikarya. Eighteen hours after exposure in the 240-kPa/202-dB range, p-NFH immunoreactivity accumulated in neuronal perikarya in layers II-IV of the temporal cortex and of the cingulate and the piriform cortices, the dentate gyrus and the CA1 region of the hippocampus. At the same time, the p-NFH immunoreactivity disappeared from the axons and dendrites of cerebral cortex neurons. The most pronounced immunostaining of neuronal perikarya was found in the hemisphere, which faced the blast source. The perikaryal accumulation of p-NFH was present also at 7 days but the neuronal perikarya had become negative at 21 days, at which time the axons again displayed p-NFH immunoreactivity. Exposure in the range of 154 kPa/198 dB caused similar, although less marked accumulation of p-NFH immunoreactivity in the neuronal perikarya. The findings are interpreted to show a dephosphorylation of NFHs in axons and dendrites and a piling up of p-NFHs in the perikarya due to disturbed axonal transport.

Neck injuries in car collisions--a review covering a possible injury mechanism and the development of a new rear-impact dummy.

A review of a few Swedish research projects on soft tissue neck injuries in car collisions is presented together with some new results. Efforts to determine neck injury mechanisms was based on a hypothesis stating that injuries to the nerve root region in the cervical spine are a result of transient pressure gradients in the spinal canal during rapid neck bending. In experimental neck trauma research on animals, pressure gradients were observed and indications of nerve cell membrane dysfunction were found in the cervical spinal ganglia. The experiments covered neck extension, flexion and lateral bending. A theoretical model in which fluid flow was predicted to cause the transient pressure gradients was developed and a neck injury criterion based on Navier-Stokes Equations was applied on the flow model. The theory behind the Neck Injury Criterion indicates that the neck injury occurs early on in the rearward motion of the head relative to the torso in a rear-end collision. Thus the relative horizontal acceleration and velocity between the head and the torso should be restricted during the early head-neck motion to avoid neck injury. A Bio-fidelic Rear Impact Dummy (BioRID) was developed in several steps and validated against volunteer test results. The new dummy was partly based on the Hybrid III dummy. It had a new articulated spine with curvature and range of motion resembling that of a human being. A new crash dummy and a neck injury criterion will be very important components in a future rear-impact crash test procedure.

[Nerve cell damages in whiplash injuries. Animal experimental studies]. / Nervenzellschäden bei Schleudertraumen. Tierexperimentelle Untersuchungen.

Mechanical loading of the cervical spine during car accidents often lead to a number of neck injury symptoms with the common term Whiplash Associated Disorders (WAD). Several of these symptoms could possibly be explained by injuries to the cervical spinal nerve root region. It was hypothesised that the changes in the inner volume of the cervical spinal canal during neck extension-flexion motion would cause transient pressure changes in the CNS as a result of hydro-dynamic effects, and thereby mechanically load the nerve roots and cause tissue damage. To test the hypothesis, anaesthetised pigs were exposed to experimental neck trauma in the extension, flexion and lateral flexion modes. The severity of the trauma was kept below the level where cervical fractures occur. Transient pressure pulses in the cervical spinal canal were duly recorded. Signs of cell membrane dysfunction were found in the nerve cell bodies of the cervical spinal ganglia. Ganglion injuries may explain some of the symptoms associated with soft-tissue neck injuries in car accidents. When the pig's head was pulled rearward relative to its torso to resemble a rear-end collision situation, it was found that ganglion injuries occurred very early on in the neck motion, at the stage where the motion changes from retraction to extension motion. Ganglion injuries did not occur when pigs were exposed to similar static loading of the neck. This indicates that these injuries are a result of dynamic phenomena and thereby further supports the pressure hypothesis. A Neck Injury Criterion (NIC) based on a theoretical model of the pressure effects was developed. It indicated that it was the differential horizontal acceleration and velocity between the head and the upper torso at the point of maximum neck retraction that determined the risk of ganglion injuries.

Membrane leakage in spinal ganglion nerve cells induced by experimental whiplash extension motion: a study in pigs.

Nerve cells in the cervical and upper thoracic spinal ganglia were examined for possible plasma membrane leakage, as revealed by their ability to exclude a dye-protein complex, after experimentally induced whiplash in a pig model system. The rationale for this approach is found in the fact that the interstitium of spinal ganglia differs from most other parts of the nervous system in that it lacks a barrier, allowing blood constituents to gain access. The dye Evans blue, which rapidly conjugates with blood proteins, is found in the interstitium of normal spinal ganglia after intravenous injection, but it is excluded from the nerve cells and their enveloping satellite cells. In contrast, after a simulated whiplash extension trauma many of the nerve cells were stained, reflecting the inability of their plasma membranes to exclude the dye-protein complex. Morphometric measurements revealed that the highest frequency of cellular dye uptake was observed in the C4-C7 spinal ganglia (mean 16 - 18%; range 5-27%). The blood-nerve barrier of the adjacent nerve fascicles remained intact, with rare exception. Several factors are considered to contribute to the induction of these cell abnormalities in the spinal ganglia after an experimentally induced, simulated whiplash trauma in this pig model system.

Comparison among different approaches for sampling cerebrospinal fluid in rats.

Two approaches for time-resolved sampling of cerebrospinal fluid (CSF) in rats were compared regarding performance, reproducibility, and extent of the inevitable trauma caused by the implantation of a sampling tube. Several parameters were checked to evaluate the injury: blood cell contamination of CSF; concentrations in CSF of the cytosolic proteins neuron-specific enolase (NSE) and S-100 (chiefly present in astrocytes); blood-brain barrier leakage of a dye-protein complex; viability of nervous tissue cells as assessed by dye exclusion; light and electron microscopy. In one sampling method, a tube was forced epidurally into the cisterna magna via a hole in the calvarium, consistently damaging the meninges and the nervous tissue. When using the alternative sampling method, the tube was instead affixed to the posterior atlanto-occipital membrane and connected with the cisterna magna via a hole in the membrane. Such a procedure caused negligible damage. Both techniques induced an inflammatory response. We advocate the use of the second approach, i.e., to sample CSF via a hole in the atlanto-occipital membrane, as the method of choice due to its high reproducibility. It is fairly rapid, and associated with a negligible injury.

A new approach for multiple sampling of cisternal cerebrospinal fluid in rodents with minimal trauma and inflammation.

A new approach was developed to minimize inevitable damage to nervous and meningeal tissue due to implantation of a sampling tube allowing multiple withdrawal of cerebrospinal fluid (CSF) from the cisterna magna in adult rats. A tube was secured on the atlanto-occipital membrane. Thereafter, a hole was cut through the membrane, allowing flow of CSF from the cisterna magna to the tube. CSF could be sampled repeatedly for at least 1 week. There was no blood-brain barrier damage. The pressure in the cisterna magna remained normal as did the estimated rate of CSF formation. Very few blood cells contaminated the CSF. There was very little evidence of inflammation. The nervous tissue was undamaged as shown by exclusion of a dye-protein complex. The CSF concentrations of the cytosolic neuronal protein neuron-specific enolase (NSE), and of the astrocyte protein S-100 were very low. The pattern of amino acids remained within normal limits. Scanning electron microscopy revealed that clot and reactive changes were restricted to the vicinity of the connecting hole. We conclude that our approach to positioning a tube on the atlanto-occipital membrane and then connecting it to the cisterna magna reproducibly and reliably enables 'atraumatic' multiple sampling of CSF.

Effects of ischemia and reperfusion on protein synthesis in livers with different glutathione levels.

The role of oxygen-free radicals for metabolic derangements in the ischemic and reperfused liver is controversial. The effect on hepatic protein synthesis of a 60-minute period of ischemia followed by two hours of reperfusion was studied in four groups of rats with different hepatic contents of the oxygen free radical scavenger glutathione (GSH): group 1, fed rats; group 2, fed rats treated with diethylmaleate (DEM) one hour before use (0.69 mL/kg, i.p.); group 3, 48-hour fasted rats; and group 4, 48-hour fasted rats treated with cobalt-chloride (45 mg/kg, s.c.) ten hours before use. Protein synthesis rates were determined by measuring incorporation of U-14C-leucine into protein in incubated liver slices. Treatment of fed rats with DEM and fasting for 48 hours significantly reduced liver GSH content. The effect of fasting on liver GSH was reversed by treatment with cobalt-chloride. The protein synthesis rate was reduced to approximately 30% of initial value at the end of the ischemic period and recovered to 70% to 100% of initial value after two hours of reperfusion with no differences between the experimental groups. Thus the effect of liver ischemia and reperfusion on protein synthesis was similar in groups of rats with different hepatic GSH contents at the onset of ischemia. The data suggest that oxygen free radicals do not play a major role for the impairment of protein synthesis in the ischemic and reperfused liver.

Studies on the possible role of oxygen-derived free radicals for impairment of protein and energy metabolism in liver ischemia.

The role of oxygen-derived free radicals for impaired protein and energy metabolism in ischemia and reperfusion injury to the liver is not known. In the present study, groups of rats received either catalase (20 mg/kg body weight), superoxide dismutase (SOD; 4 mg/kg body weight), or catalase + SOD i.v. 10 min before induction of ischemia in the left and median liver lobes. Control animals received corresponding volumes of solvent. The length of the ischemic period was 60 or 90 min. Protein synthesis was measured in incubated liver slices before induction of ischemia, at the end of the ischemia period, and during 2 h of reperfusion. Tissue concentrations of ATP, ADP, AMP, and hepatic tissue water were determined at the same time points. Protein synthesis and energy level were markedly reduced at the end of ischemia and were restituted during the 2-h reperfusion when the ischemic period was 60 min; they remained depressed during reperfusion when the ischemic period was 90 min. Hepatic tissue water was increased at the end of the ischemic period and remained elevated during reperfusion. There were no significant differences in protein synthesis, energy level or tissue water between catalase- or SOD-treated animals and controls either at the end of a 60- or 90-min ischemic period or during the 2-h reperfusion. The results suggest that oxygen-derived free radicals do not play a major role for impaired protein and energy metabolism in liver ischemia and following reperfusion.

Protein and energy metabolism in liver tissue following intravenous infusion of live E. coli bacteria in rats.

In the present study protein synthesis and energy level in liver tissue were studied in bacteremic rats following intravenous infusion of 8 +/- 4 X 10(9) live E. coli bacteria and in control animals receiving a corresponding infusion of sterile saline. For the study of protein synthesis, liver slices were incubated in a medium containing 14C-leucine and incorporation rate of amino acid into protein was determined. Hepatic concentrations of ATP, ADP, and AMP were measured and energy charge (EC) was calculated. Twenty-four hours after infusion of E. coli, hepatic protein synthesis rate was 55% higher than in control animals. Liver weight and hepatic protein content were also increased in bacteremic animals. There were no significant differences in adenine nucleotide levels or EC in liver tissue between control and bacteremic animals. Since impairment of various other liver functions has been reported during sepsis, the present results suggest that hepatic protein synthesis has high priority in this condition.

Effect of methylprednisolone, indomethacin, and diethylcarbamazine on survival rate following trauma and sepsis in rats.

The role of steroids in the treatment of sepsis and septic shock remains controversial, and it is not known if a possible beneficial effect is due to inhibition of the cyclooxygenase or lipoxygenase pathway of arachidonic acid metabolism. In this investigation we studied the effect of methylprednisolone (MP), the cyclooxygenase inhibitor indomethacin (IM), and the lipoxygenase inhibitor diethylcarbamazine (DE) on survival rate in an experimental trauma-sepsis model in rats consisting of laparotomy and intravenous infusion of live E. coli. Groups of rats received saline (control) or MP (30 mg/kg) intravenously 30 min before or after induction of trauma-sepsis. In other groups of animals IM (4 mg/kg) or DE (0.2 mmol/kg) was administered intravenously 30 min before trauma-sepsis. Survival rate was significantly improved by MP or DE given 30 min before trauma-sepsis while the other treatments did not affect the outcome. The results indicate that the beneficial effect of MP on survival rate in the present trauma-sepsis model did not reflect inhibited prostaglandin synthesis but might have been due to inhibited production of leukotrienes.

Protein turnover in skeletal muscle tissue from patients with hyperparathyroidism and the effect of calcium in vitro.

Protein synthesis and degradation rates in muscle tissue from hypercalcemic and normocalcemic patients were compared. Both protein synthesis and degradation rates were similar in muscle tissue from patients with hyperparathyroidism and age-matched, normocalcemic patients. When Ca++ concentration in the incubation medium was increased, protein breakdown was stimulated in muscle tissue from normocalcemic and hypercalcemic patients, while protein synthesis was increased only in muscle tissue from hypercalcemic patients. The results indicate that protein turnover in muscle tissue is not affected by varying serum calcium levels, but can be regulated by increased Ca++ concentration in vitro.

One instead of two knives for surgical incision. Does it increase the risk of postoperative wound infection?

We evaluated the rate of postoperative wound infection following the use of one or two knives for incision. The infection rate in 277 patients who were operated on with one knife was 3.6%, in 309 patients who were operated on with two knives the rate was 5.5%. This difference was not statistically significant. The limit of a one-sided confidence interval bound from the estimated difference of infection rates in the two groups of patients was 0.94% at a confidence level of 0.95. Thus, if there was any difference at all in favor of two knives with respect to infection, it was probably less than 1%. The present results indicate that the old surgical practice of discarding the skin knife and using a separate scalpel for the deep incision can be abandoned without increasing the risk of wound infection.

Postoperative wound infections in patients with long preoperative hospital stay.

In a prospective study of 1243 operations the rate of postoperative wound sepsis was 9.3%. Factors associated with high infection rate were high age, emergency operations, long duration of surgical procedure, potentially contaminated and contaminated operations, diabetes and treatment with steroids. The frequency of wound sepsis was also increased in patients with long preoperative hospital stay or 12.5% as compared to 4.5% in patients with a preoperative stay of one day. Among patients with long preoperative hospitalization, high age, long operative procedures, contaminated operations and treatment with steroids were significantly more common. 85% of the patients with long preoperative hospital stay and wound infection had three or more other factors associated with increased frequency of wound sepsis. No patient had long preoperative hospital stay as the only factor associated with high rate of wound infection. These data indicate that long preoperative hospitalization is not in itself a causative factor in wound infections, but might be related to other factors associated with increased likelihood of wound sepsis.

Postoperative wound infections--a prospective study in a newly opened hospital.

The rate of postoperative wound infections was determined in a prospective study during one year in a newly opened University hospital. Protocols which were part of the routine care of the patients were used for recording of wound infections. This method of registration was simple and proved to be efficient with a failure rate of only 1%. The overall infection rate was 9%--after clean surgery 2.6%, potentially contaminated surgery 14% and contaminated surgery 16%. Old age, long preoperative hospital stay, emergency operations and long operative times were associated with high frequency of wound infections. The importance of continuous recording of wound infections in a surgical unit was emphasized.