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.

Impulse noise includes all forms of high-intensity short duration-sounds, i.e. from impacts produced by industrial equipment, airbag deployment to intense blast waves associated with military operations. The brain has for a long time been considered less susceptible to injuries caused by impulse noise. We have measured the intra-cranial and intra-abdominal sound pressure levels during impulse noise exposure. The brain seems to be as susceptible to impulse noise as other organs. The intra-abdominal sound pressure level was highly dependent on the orientation of the animal to the pressure source. Immunohistochemical studies on rats exposed to impulse noise demonstrate the hallmarks of diffuse brain injury. Threshold levels allowed in MIL-STD may protect the inner organs but not necessarily the brain. Shock-tube experiments will provide information in the relative importance of the parameters of the pressure wave.

A single exposure to intense impulse noise may cause diffuse brain injury, revealed by increased expression of immediate early gene products, transiently altered distribution of neurofilaments, accumulation of beta-amyloid precursor protein, apoptosis, and gliosis. Neither hemorrage nor any gross structural damage are seen. The present study focused on whether impulse noise exposure increased the permeability of nerve and glial cell membranes to proteins. Also, we investigated whether a preceding,,minor focal surgical brain lesion accentuated the leakage of cytosolic proteins. Anaesthetized rats were exposed to a single impulse noise at either 199 or 202 dB for 2 milliseconds. Transiently elevated levels of the cellular protein neuron specific enolase (NSE) and the glial cytoplasmic protein S-100 were recorded in the cerebrospinal fluid (CSF) during the first hours after the exposure to 202 dB. A surgical brain injury, induced the day before the exposure to the impulse noise, was associated with significantly increased concentrations of both markers in the CSF. It is concluded that intense impulse noise damages both nerve and glial cells, an effect aggravated by a preexisting surgical lesion. The impulse of the shock wave, i.e. the pressure integrated over time, is likely to be the injurious mechanism. The abnormal membrane permeability and the associated cytoskeletal changes may initiate events, which eventually result in a progressive diffuse brain injury.

Exposure to impulse noise, above a certain intensity, is harmful to auditory function. Effects of impulse noise on the central nervous system (CNS) are largely unexplored, and there is little information on critical threshold values and time factors. We have recently shown that neurofilament proteins are affected in the cerebral cortex and the hippocampus. Now we show that impulse noise induces expression of the immediate early gene c-Jun products, proposed to play a role in the initiation of neuronal death, and apoptosis as revealed by TUNEL staining. Rat brains were investigated immunohistochemically 2 h to 21 days after exposure to impulse noise of 198 dB or 202 dB. c-Jun was expressed in neuronal perikarya in layers II-VI of the temporal cortex, the cingulate and the piriform cortices at 2 h to 21 days after both exposure levels. Granule neurons of the dentate gyrus and the CA1-3 in the hippocampus pyramidal neurons were similarly affected. The elevated expression of c-Jun products remained high at all postexposure times. TUNEL staining was positive among the same nerve cell populations 6 h after exposure and persisted even at 7 days at both exposure levels.

There is increasing evidence that impulse noise causes brain damage, but little is known about the mechanisms and extent of the response. Here, rat brains were investigated immunohistochemically for the expression of c-Fos, c-Myc, and beta-APP during the first 3 weeks postexposure to impulse noise of 198 or 202 dB. The expression of c-Fos and c-Myc increased at 2 h after exposure in neurons of the cerebral cortex, thalamus, and hippocampus, and this c-Fos immunoreactivity remained elevated for the entire observation period. The c-Myc immunoreactivity peaked at 18 h in both neurons and astrocytes but returned to control levels at 7 days. Abnormal deposition of beta-APP was evident within 6 h in the same brain regions. The beta-APP immunoreactivity was most prominent at 18 h and remained increased over the 21-day period assessed. The observed effects were similar to those described in humans following traumatic brain injury and in Alzheimer's disease. We conclude that impulse noise influences the brain in a fashion similar to that in cases with progressive CNS degeneration.

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.

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.

Die mechanische Belastung der Halswirbelsäule (HWS) bei Autounfällen verursacht oft eine Reihe von Halsverletzungen, die unter dem Begriff Schleudertrauma zusammengefaßt werden. Mehrere dieser Symptome können möglicherweise durch Verletzungen im Bereich der Nervenwurzeln der HWS erklärt werden. Die Hypothese wurde aufgestellt, daß während der Extensions- und Flexionsbewegungen des Halses, aufgrund von hämodynamischen Auswirkungen, Änderungen des inneren Volumens des Halswirbelkanals kurzzeitige Druckveränderungen im ZNS verursachen und daß dadurch Gewebeschäden durch die mechanische Belastung der Nervenwurzel entstehen. Um die Hypothese zu überprüfen, wurden anästhesierte Schweine einem experimentellen Schleudertrauma mit Extensions-, Flexions- und Seitneigungsbewegungen ausgesetzt. Die traumatische Belastung wurde unterhalb einer Stufe gehalten, bei der eine Halswirbelfraktur stattfinden könnte. Während der Belastung wurde der Pulsdruck im Halswirbelkanal gemessen. In diesem Zusammenhang ergaben sich Hinweise einer Dysfunktion der Zellmembran bei Nervenzellkörpern der Spinalganglien. Die ganglionären Verletzungen können möglicherweise einige der mit Weichteilverletzungen des Halses nach Autounfällen einhergehenden Symptome erklären. Um die Situation bei einem Auffahrunfall zu simulieren, wurde der Kopf des Schweines rückwärts vom Torso weggezogen. Dabei wurde festgestellt, daß die ganglionären Verletzungen zu einem sehr frühen Zeitpunkt während der Halsbewegungen stattfinden und zwar in der Phase, in der die Bewegung von der Retraktion zur Extension wechselt. Bei einer ähnlichen, jedoch statischen Belastung des Halses wurden keine ganglionären Verletzungen bei den Schweinen festgestellt. Dies ist ein Hinweis darauf, daß diese Verletzungen durch dynamische Faktoren verursacht werden und bietet somit weitere Unterstützung für die Druckhypothese. Auf der Basis eines theoretischen Modells wurden Kriterien für Halsverletzungen (neck injury criterion = NIC) entwickelt. Es weist darauf hin, daß das Risiko von ganglionären Verletzungen am Punkt der maximalen Halsretraktion durch die unterschiedliche horizontale Beschleunigung und Geschwindigkeit zwischen Kopf und oberem Torso bestimmt wird.

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.

Zusammenfassung Die mechanische Belastung der Halswirbelsäule (HWS) bei Autounfällen verursacht oft eine Reihe von Halsverletzungen, die unter dem Begriff Schleudertrauma zusammengefaßt werden. Mehrere dieser Symptome können möglicherweise durch Verletzungen im Bereich der Nervenwurzeln der HWS erklärt werden. Die Hypothese wurde aufgestellt, daß während der Extensions- und Flexionsbewegungen des Halses, aufgrund von hämodynamischen Auswirkungen, Änderungen des inneren Volumens des Halswirbelkanals kurzzeitige Druckveränderungen im ZNS verursachen und daß dadurch Gewebeschäden durch die mechanische Belastung der Nervenwurzel entstehen. Um die Hypothese zu überprüfen, wurden anästhesierte Schweine einem experimentellen Schleudertrauma mit Extensions-, Flexions- und Seitneigungsbewegungen ausgesetzt. Die traumatische Belastung wurde unterhalb einer Stufe gehalten, bei der eine Halswirbelfraktur stattfinden könnte. Während der Belastung wurde der Pulsdruck im Halswirbelkanal gemessen. In diesem Zusammenhang ergaben sich Hinweise einer Dysfunktion der Zellmembran bei Nervenzellkörpern der Spinalganglien. Die ganglionären Verletzungen können möglicherweise einige der mit Weichteilverletzungen des Halses nach Autounfällen einhergehenden Symptome erklären. Um die Situation bei einem Auffahrunfall zu simulieren, wurde der Kopf des Schweines rückwärts vom Torso weggezogen. Dabei wurde festgestellt, daß die ganglionären Verletzungen zu einem sehr frühen Zeitpunkt während der Halsbewegungen stattfinden und zwar in der Phase, in der die Bewegung von der Retraktion zur Extension wechselt. Bei einer ähnlichen, jedoch statischen Belastung des Halses wurden keine ganglionären Verletzungen bei den Schweinen festgestellt. Dies ist ein Hinweis darauf, daß diese Verletzungen durch dynamische Faktoren verursacht werden und bietet somit weitere Unterstützung für die Druckhypothese. Auf der Basis eines theoretischen Modells wurden Kriterien für Halsverletzungen (neck injury criterion = NIC) entwickelt. Es weist darauf hin, daß das Risiko von ganglionären Verletzungen am Punkt der maximalen Halsretraktion durch die unterschiedliche horizontale Beschleunigung und Geschwindigkeit zwischen Kopf und oberem Torso bestimmt wird.

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.

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. Copyright © 1996 Elsevier Science Inc.

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.

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.

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.

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.

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 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.