Refining outcome prediction after traumatic brain injury with machine learning algorithms.

Outcome after traumatic brain injury (TBI) is typically assessed using the Glasgow outcome scale extended (GOSE) with levels from 1 (death) to 8 (upper good recovery). Outcome prediction has classically been dichotomized into either dead/alive or favorable/unfavorable outcome. Binary outcome prediction models limit the possibility of detecting subtle yet significant improvements. We set out to explore different machine learning methods with the purpose of mapping their predictions to the full 8 grade scale GOSE following TBI. The models were set up using the variables: age, GCS-motor score, pupillary reaction, and Marshall CT score. For model setup and internal validation, a total of 866 patients could be included. For external validation, a cohort of 369 patients were included from Leuven, Belgium, and a cohort of 573 patients from the US multi-center ProTECT III study. Our findings indicate that proportional odds logistic regression (POLR), random forest regression, and a neural network model achieved accuracy values of 0.3-0.35 when applied to internal data, compared to the random baseline which is 0.125 for eight categories. The models demonstrated satisfactory performance during external validation in the data from Leuven, however, their performance were not satisfactory when applied to the ProTECT III dataset.

High Intravascular Signal Arterial Transit Time Artifacts Have Negligible Effects on Cerebral Blood Flow and Cerebrovascular Reserve Capacity Measurement Using Single Postlabel Delay Arterial Spin-Labeling in Patients with Moyamoya Disease.

BACKGROUND AND PURPOSE: Arterial spin-labeling-derived CBF values may be affected by arterial transit time artefacts. Thus, our aim was to assess to what extent arterial spin-labeling-derived CBF and cerebrovascular reserve capacity values in major vascular regions are overestimated due to the arterial transit time artifacts in patients with Moyamoya disease. MATERIALS AND METHODS: Eight patients with Moyamoya disease were included before or after revascularization surgery. CBF maps were acquired using a 3D pseudocontinuous arterial spin-labeling sequence, before and 5, 15, and 25 minutes after an IV acetazolamide injection and were registered to each patient's 3D-T1-weighted images. Vascular regions were defined by spatial normalization to a Montreal Neurological Institute-based vascular regional template. The arterial transit time artifacts were defined as voxels with high signal intensity corresponding to the right tail of the histogram for a given vascular region, with the cutoff selected by visual inspection. Arterial transit time artifact maps were created and applied as masks to exclude arterial transit time artifacts on CBF maps, to create corrected CBF maps. The cerebrovascular reserve capacity was calculated as CBF after acetazolamide injection relative to CBF at baseline for corrected and uncorrected CBF values, respectively. RESULTS: A total of 16 examinations were analyzed. Arterial transit time artifacts were present mostly in the MCA, whereas the posterior cerebral artery was generally unaffected. The largest differences between corrected and uncorrected CBF and cerebrovascular reserve capacity values, reported as patient group average ratio and percentage point difference, respectively, were 0.978 (95% CI, 0.968-0.988) and 1.8 percentage points (95% CI, 0.3-3.2 percentage points). Both were found in the left MCA, 15 and 5 minutes post-acetazolamide injection, respectively. CONCLUSIONS: Arterial transit time artifacts have negligible overestimation effects on calculated vascular region-based CBF and cerebrovascular reserve capacity values derived from single-delay 3D pseudocontinuous arterial spin-labeling.

Grafted neural progenitors migrate and form neurons after experimental traumatic brain injury.

PURPOSE: Neural stem and progenitor cells (NSPC) generate neurons and glia, a feature that makes them attractive for cell replacement therapies. However, efforts to transplant neural progenitors in animal models of brain injury typically result in high cell mortality and poor neuronal differentiation. METHODS: In an attempt to improve the outcome for grafted NSPC after controlled cortical impact we transplanted Enhanced Green Fluorescent Protein (EGFP)-positive NSPC into the contra lateral ventricle of mice one week after injury. RESULTS: Grafted EGFP-NSPC readily migrated to the injured hemisphere where we analyzed the proportion of progenitors and differentiated progeny at different time points. Transplantation directly into the injured parenchyma, resulted in few brains with detectable EGFP-NSPC. On the contrary, in more than 90% of the mice that received a transplant into the lateral ventricle detectable EGFP-positive cells were found. The cells were integrated into the lateral ventricle wall of the un-injured hemisphere, throughout the corpus callosum, and in the cortical perilesional area. At one-week post transplantation, grafted cells that had migrated to the perilesion area mainly expressed markers of neural progenitors and neurons, while in the corpus callosum and the ventricular lining, grafted cells with a glial fate were more abundant. After 3 months, grafted cells in the perilesion area were less abundant whereas cells that had migrated to the walls of the third- and lateral- ventricle of the injured hemisphere were still detectable, suggesting that the injury site remained a hostile environment. CONCLUSION: Transplantation to the lateral ventricle, presumably for being a neurogenic region, provides a favorable environment improving the outcome for grafted NSPC both in term of their appearance at the cortical site of injury, and their acquisition of neural markers.

A furosemide-sensitive K+-Cl- cotransporter counteracts intracellular Cl- accumulation and depletion in cultured rat midbrain neurons.

Efficacy of postsynaptic inhibition through GABAA receptors in the mammalian brain depends on the maintenance of a Cl- gradient for hyperpolarizing Cl- currents. We have taken advantage of the reduced complexity under which Cl- regulation can be investigated in cultured neurons as opposed to neurons in other in vitro preparations of the mammalian brain. Tightseal whole-cell recording of spontaneous GABAA receptor-mediated postsynaptic currents suggested that an outward Cl- transport reduced dendritic [Cl-]i if the somata of cells were loaded with Cl- via the patch pipette. We determined dendritic and somatic reversal potentials of Cl- currents induced by focally applied GABA to calculate [Cl-]i during variation of [K+]o and [Cl-] in the patch pipette. [Cl-]i and [K+]o were tightly coupled by a furosemide-sensitive K+-Cl- cotransport. Thermodynamic considerations excluded the significant contribution of a Na+-K+-Cl- cotransporter to the net Cl- transport. We conclude that under conditions of normal [K+]o the K+-Cl- cotransporter helps to maintain [Cl-]i at low levels, whereas under pathological conditions, under which [K+]o remains elevated because of neuronal hyperactivity, the cotransporter accumulates Cl- in neurons, thereby further enhancing neuronal excitability.

Insulin-like growth factor 1 and a cytosolic tyrosine kinase activate chloride outward transport during maturation of hippocampal neurons.

The development of hyperpolarizing inhibition is an important step in the maturation of neuronal networks. Hyperpolarizing inhibition requires Cl(-) outward transport that is accomplished by KCC2, a K(+)/Cl(-) cotransporter. We show that cultured hippocampal neurons initially contain an inactive form of the KCC2 protein, which becomes activated during subsequent maturation of the neurons. We also show that this process is accelerated by transient stimulation of IGF-1 receptors. Because the transporter can be rapidly activated by coapplication of IGF-1 and an Src kinase and can be deactivated by membrane-permeable protein tyrosine kinase inhibitors, we suggest that activation of K(+)/Cl(-) cotransporter function by endogenous protein tyrosine kinases mediates the developmental switch of GABAergic responses to hyperpolarizing inhibition.

Increased cytochrome c-mediated DNA fragmentation and cell death in manganese-superoxide dismutase-deficient mice after exposure to subarachnoid hemolysate.

BACKGROUND AND PURPOSE: We sought to investigate the mechanisms for oxidative injury caused by subarachnoid hemolysate, a pro-oxidant. METHODS: Injection of 50 microL of subarachnoid hemolysate or saline was performed in CD1 mice (n=75), mutant mice deficient in Mn-superoxide dismutase (Sod2+/-; n=23), and their wild-type littermates (n=23). Subcellular location of cytochrome c was studied by immunocytochemistry, immunofluorescence, and immunoblotting of cellular fractions. DNA fragmentation was assessed though DNA laddering and terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end-labeling (TUNEL). Cell death was examined through basic histology. RESULTS: Cytochrome c immunoreactivity was present in the cytosol of neurons at 2 hours after hemolysate injection and increased by 4 hours compared with saline-injected animals (P:<0.02). Cytosolic cytochrome c was more abundant in Sod2+/- mutants. DNA fragmentation was evident at 24 hours, but not 4 hours, after hemolysate injection as determined by DNA laddering and TUNEL staining (P:<0.02). DNA fragmentation colocalized to cells with cytosolic cytochrome c and iron. In Sod2+/- mutants, the extent of fragmentation was increased as determined by TUNEL staining (52% increase; P:<0.02) and DNA laddering (optical density=0.819 versus 0.391; P:<0.01). Cell death was evident on basic histology as early as 4 hours after hemolysate injection. No cell death was evident in controls. In Sod2+/- mutants, cell death was increased by 51% compared with wild-type littermates (P:<0.05). CONCLUSIONS: These results demonstrate that subarachnoid blood products are associated with the presence of cytochrome c in the cytosol and subsequent cell death in neurons. It appears that Mn-superoxide dismutase plays a role in preventing cell death after exposure to subarachnoid blood products.

Neuronal expression of the DNA repair protein Ku 70 after ischemic preconditioning corresponds to tolerance to global cerebral ischemia.

BACKGROUND AND PURPOSE: Oxidative stress after ischemia/reperfusion has been shown to induce DNA damage and subsequent DNA repair activity. Ku 70/86, multifunctional DNA repair proteins, bind to broken DNA ends and trigger a DNA repair pathway. We investigated the involvement of these proteins in the development of neuronal tolerance to global cerebral ischemia after ischemic preconditioning. METHODS: Adult male Sprague-Dawley rats were subjected to either 5 minutes of lethal global ischemia with or without 3 minutes of sublethal ischemic preconditioning or 3 minutes of ischemia only. Neuronal injury was histologically assessed, and DNA damage was visualized by in situ labeling of DNA fragmentation and DNA gel electrophoresis. Ku expression was also examined by immunohistochemistry and Western blot analysis. RESULTS: Hippocampal CA1 neurons underwent DNA-fragmented cell death 3 days after 5 minutes of ischemia. However, these neurons showed a strong tolerance to 5 minutes of ischemia 1 to 3 days after ischemic preconditioning. Immunohistochemistry showed virtually no constitutive expression of Ku proteins in CA1 neurons; however, ischemic preconditioning induced neuronal Ku 70 expression 1 to 3 days later. Western blot confirmed an increase in Ku 70 in this region at the same time. CONCLUSIONS: The temporal and spatial expression of Ku 70 corresponded to tolerance of the hippocampal CA1 neurons to subsequent ischemia, suggesting the involvement of Ku proteins in the development of neuronal tolerance after ischemic preconditioning.

Neuronal, but not microglial, accumulation of extravasated serum proteins after intracerebral hemolysate exposure is accompanied by cytochrome c release and DNA fragmentation.

Vasogenic edema after oxidative injury has been accompanied by intracellular accumulation of serum proteins and nuclear damage. This study sought to determine whether serum protein accumulation, along with other markers of brain injury, was present after exposure to intracerebral hemolysate, an oxidant model of intracerebral hemorrhage (ICH). Saline (n = 24) or hemolysate (n = 30) was injected into the caudate-putamen of adult Sprague-Dawley rats. Compared with saline, hemolysate deposition was associated with intracellular accumulation of serum proteins as evidenced by Evans blue uptake in neurons and microglia at 4 and 24 hours. Intracellular Evans blue colocalized with DNA fragmentation detected by nick end-labeling and whose presence was confirmed by gel electrophoresis. Immunoblots of cytosolic fractions confirmed cytochrome c release. Immunostaining established colocalization of cytosolic cytochrome c and intracellular Evans blue at 4 hours. At 24 hours, cytosolic cytochrome c was evident in astrocytes surrounding Evans blue-positive cells. Immunoblot analysis and immunostaining revealed HSP70 induction at 24 hours in regions adjacent to intracellular serum accumulation. Neuronal accumulation of extravasated serum proteins in this model of ICH was associated with cytochrome c release, DNA fragmentation, and cell death. Stress protein induction in adjacent regions suggested that vasogenic edema might have exacerbated cellular dysfunction and cell death after ICH.

Evidence of phosphorylation of Akt and neuronal survival after transient focal cerebral ischemia in mice.

The serine-threonine kinase, Akt, prevents apoptosis by phosphorylation at serine-473 in several cell systems. After phosphorylation, activated Akt inactivates other apoptogenic factors, such as Bad or caspase-9, thereby inhibiting cell death. The present study examined phosphorylation of Akt at serine-473 and DNA fragmentation after transient focal cerebral ischemia in mice subjected to 60 minutes of focal cerebral ischemia by intraluminal blockade of the middle cerebral artery. Phospho-Akt was analyzed by immunohistochemistry and Western blot analysis. The DNA fragmentation was evaluated by terminal deoxynucleotidyl transferase-mediated uridine 5-triphosphate-biotin nick end-labeling (TUNEL). Immunohistochemistry showed the expression of phospho-Akt was markedly increased in the middle cerebral artery territory cortex at 4 hours of reperfusion compared with the control, whereas it was decreased by 24 hours. Western blot analysis showed a significant increase of phospho-Akt 4 hours after focal cerebral ischemia in the cortex, whereas phospho-Akt was decreased in the ischemic core. Double staining with phospho-Akt and TUNEL showed different cellular distributions of phospho-Akt and TUNEL-positive staining. Phosphorylation of Akt was prevented after focal cerebral ischemia by LY294002, a phosphatidylinositol 3-kinase inhibitor, which facilitated subsequent DNA fragmentation. These results suggest that phosphorylation of Akt may be involved in determining cell survival or cell death after transient focal cerebral ischemia.

Oxidative stress-dependent release of mitochondrial cytochrome c after traumatic brain injury.

Mitochondrial cytochrome c translocation to the cytosol initiates the mitochondrial-dependent apoptotic pathway. This event has not been previously reported in traumatic brain injury (TBI). The authors determined the expression of cytochrome c in cytosolic and mitochondrial fractions after severe TBI produced by the controlled cortical impact model in the mouse. One hour after trauma there was an increase in cytosolic cytochrome c immunoreactivity. The increases in cytosolic cytochrome c preceded DNA fragmentation, which started at 4 hours. Western blots of mitochondrial and cytosolic fractions confirmed that there was a translocation of cytochrome c from the mitochondria after TBI. Mice deficient in manganese superoxide dismutase (MnSOD) showed an increased loss of mitochondrial cytochrome c after trauma, but less apoptotic cell death 4 and 24 hours after injury compared with wild-type control mice. However, the overall cell death was increased in MnSOD mice, as illustrated by a larger cortical lesion in these animals. The results show that cytochrome c is released from the mitochondria after severe TBI partly by a free radical-dependent mechanism, and that massive mitochondrial cytochrome c release is a predictor of necrotic cell death rather than apoptosis.

Paradoxical increase in neuronal DNA fragmentation after neuroprotective free radical scavenger treatment in experimental traumatic brain injury.

The mechanisms and role of nerve cell death after traumatic brain injury (TBI) are not fully understood. The authors investigated the effect of pretreatment with the oxygen free radical spin trap alpha-phenyl-N-tert-butyl-nitrone (PBN) on the number of neurons undergoing apoptosis after TBI in rats. Apoptotic cells were identified by the TUNEL method combined with the nuclear stain, Hoechst 33258, and immunohistochemistry for the active form of caspase-3. Numerous neurons became positive for activated caspase 3 and TUNEL in the cortex at 24 hours after injury, suggesting ongoing biochemical apoptosis. In PBN-treated rats, a significantly greater number of cells were found to be TUNEL positive at 24 hours compared with controls. However, PBN treatment resulted in a reduced cortical lesion volume and improved behavioral outcome two weeks after injury. The authors conclude that a treatment producing an increase in DNA fragmentation in the early phase may be compatible with an overall beneficial effect on outcome after TBI. This should be considered in the screening process for future neuroprotective remedies.

Regulation of pituitary adenylate cyclase activating polypeptide and its receptor type 1 after traumatic brain injury: comparison with brain-derived neurotrophic factor and the induction of neuronal cell death.

Neurotrophic factors are known to promote neuronal survival during development and after acute brain injury. Recent data suggest that some neuropeptides also exhibit neurotrophic activities, as shown for the pituitary adenylate cyclase activating polypeptide, which increases the survival of various neuronal populations in culture. Employing in situ hybridization techniques, we have studied the regulation of messenger RNA for pituitary adenylate cyclase activating polypeptide and its receptor type 1 after a moderate traumatic brain injury to rat brain cortex. We have further compared their messenger RNA expression to that of brain-derived neurotrophic factor and to the amount of cell death occurring in the brain at various times after the brain injury. Levels of brain-derived neurotrophic factor messenger RNA increased rapidly within 2 h after trauma in cortex and hippocampus, and returned to control levels thereafter. The levels of messenger RNA for pituitary adenylate cyclase activating polypeptide also increased with time in the injured brains and reached maximal expression at 72 h, i.e. the end of the observation period. The alterations in pituitary adenylate cyclase activating polypeptide messenger RNA levels were particularly pronounced in the perifocal region and in the ipsilateral dentate gyrus of the brain injury. In contrast, the messenger RNA levels encoding pituitary adenylate cyclase activating polypeptide receptor type 1 first decreased after trauma and were then normalized in the dentate gyrus. There was a large increase in the number of cells labelled for DNA breaks at 12 h post-trauma, indicative of enhanced cell death. The number of labelled cells, however, decreased at later stages concomitant with an increase in the expression of pituitary adenylate cyclase activating polypeptide messenger RNA. Pituitary adenylate cyclase activating polypeptide rescued cortical neurons in cultures against ionomycin-induced cell death, supporting the concept of a neuroprotective effect for the peptide. These results demonstrate a differential regulation of messenger RNA for brain-derived neurotrophic factor and the pituitary adenylate cyclase activating polypeptide and its receptor after brain trauma. The data also suggest that pituitary adenylate cyclase activating polypeptide might have a beneficial effect in brain injury by counteracting neuronal cell death.

The cytosolic antioxidant, copper/zinc superoxide dismutase, attenuates blood-brain barrier disruption and oxidative cellular injury after photothrombotic cortical ischemia in mice.

Oxidative stress has been associated with the development of blood-brain barrier disruption and cellular injury after ischemia. The cytosolic antioxidant, copper/zinc superoxide dismutase, has been shown to protect against blood-brain barrier disruption and infarction after cerebral ischemia-reperfusion. However, it is not clear whether copper/zinc superoxide dismutase can protect against evolving ischemic lesions after thromboembolic cortical ischemia. In this study, the photothrombotic ischemia model, which is physiologically similar to thromboembolic stroke, was used to develop cortical ischemia. Blood-brain barrier disruption and oxidative cellular damage were investigated in transgenic mice that overexpress copper/zinc superoxide dismutase and in littermate wild-type mice after photothrombotic ischemia, which was induced by both injection of erythrosin B (30 mg/kg) and irradiation using a helium neon laser for 3 min. Free radical production, particularly superoxide, was increased in the lesioned cortex as early as 4 h after ischemia using hydroethidine in situ detection. The transgenic mice showed a prominent decrease in oxidative stress compared with the wild-type mice. Blood-brain barrier disruption, evidenced by quantitation of Evans Blue leakage, occurred 1 h after ischemia and gradually increased up to 24 h. Compared with the wild-type mice, the transgenic mice showed less blood-brain barrier disruption, a decrease in oxidative DNA damage using 8-hydroxyguanosine immunohistochemistry, a subsequent decrease in DNA fragmentation using the in situ nick-end labeling technique, and decreased infarct volume after ischemia. From these results we suggest that superoxide anion radical is an important factor in blood-brain barrier disruption and oxidative cellular injury, and that copper/zinc superoxide dismutase could protect against the evolving infarction after thromboembolic cortical ischemia.

MAP2 and neurogranin as markers for dendritic lesions in CNS injury. An immunohistochemical study in the rat.

We compared two staining methods for the demonstration of dendrites under normal and pathological conditions of the rat central nervous system. MAP2- and neurogranin immunohistochemistry was applied to samples from normal tissue, spinal cord subjected to graded compression trauma, cerebral cortex following contusion trauma, and brains with focal ischemic lesions induced by occlusion of the middle cerebral artery (MCAO). Normal rats showed MAP2 immunoreactivity in nerve cell bodies and dendrites of brain and spinal cord. However, neurogranin staining was present only in nerve cell bodies and dendrites of the normal brain, and not in the spinal cord. Reduction of MAP2 immunoreactivity was seen in lesions of spinal cords subjected to compression trauma. Neurogranin staining was of no value in this experimental condition since it was not present under normal conditions. The brain contusions showed loss of both MAP2- and neurogranin immunoreactivity at the site of the lesion. MCAO resulted in an extensive loss of MAP2- and neurogranin staining in the ipsilateral hemisphere. In conclusion, our study shows that MAP2 immunostaining is a sensitive method for identifying dendritic lesions of various CNS injuries in the rat. Neurogranin immunostaining is an alternative method for investigations of dendritic pathology in the brain but not in the spinal cord.

Involvement of reactive oxygen species in membrane phospholipid breakdown and energy perturbation after traumatic brain injury in the rat.

Interstitial glycerol may be a useful marker for posttraumatic and postischemic membrane phospholipid (PL) breakdown. Degradation of membrane PLs is thought to be triggered by both calcium and reactive oxygen species (ROS)-mediated mechanisms and to be associated with disturbed energy metabolism. In this study, we investigated the temporal changes of interstitial glycerol, lactate, and glucose after traumatic brain injury in the rat and the effect of pretreatment with the free radical spin trap alpha-phenyl-N-tert-butyl nitrone (PBN; 30 mg/kg i.v.). Microdialysate was sampled continuously in 10-min fractions from 1 h before, until 2 h after a cortical contusion injury produced by the weight-drop technique. The maximal concentration of interstitial glycerol (a ninefold increase) was seen 10-30 min after trauma and subsided during the following 2 h, but remained above base line as compared to sham operated animals. Concomitantly, there was an increase in interstitial lactate (fivefold) and a fall in interstitial glucose, indicating a posttraumatic energy perturbation. PBN treatment significantly attenuated the interstitial accumulation of glycerol and lactate. The results support the concept that ROS are involved in posttraumatic membrane PL breakdown and that PBN improves mitochondrial function after CNS injury. Monitoring of interstitial glycerol with microdialysis may be a valuable tool for studies on membrane PL degradation and the efficacy of neuroprotective drugs in acute CNS injury.

Free radical pathways in CNS injury.

Free radicals are highly reactive molecules implicated in the pathology of traumatic brain injury and cerebral ischemia, through a mechanism known as oxidative stress. After brain injury, reactive oxygen and reactive nitrogen species may be generated through several different cellular pathways, including calcium activation of phospholipases, nitric oxide synthase, xanthine oxidase, the Fenton and Haber-Weiss reactions, by inflammatory cells. If cellular defense systems are weakened, increased production of free radicals will lead to oxidation of lipids, proteins, and nucleic acids, which may alter cellular function in a critical way. The study of each of these pathways may be complex and laborious since free radicals are extremely short-lived. Recently, genetic manipulation of wild-type animals has yielded species that over- or under-express genes such as, copper-zinc superoxide dismutase, manganese superoxide dismutase, nitric oxide synthase, and the Bcl-2 protein. The introduction of the species has improved the understanding of oxidative stress. We conclude here that substantial experimental data links oxidative stress with other pathogenic mechanisms such as excitotoxicity, calcium overload, mitochondrial cytochrome c release, caspase activation, and apoptosis in central nervous system (CNS) trauma and ischemia, and that utilization of genetically manipulated animals offers a unique possibility to elucidate the role of free radicals in CNS injury in a molecular fashion.

Glycerol as a marker for post-traumatic membrane phospholipid degradation in rat brain.

Degradation of membrane phospholipids (PLs) is a well known phenomenon in acute brain injuries and is thought to underlie the disturbance of vital cellular membrane functions. In the present study glycerol, an end product of PL degradation, was examined in brain interstitial fluid as a marker of PL breakdown following experimental traumatic brain injury (TBI) using microdialysis. TBI was induced in artificially ventilated rats using the weight-drop technique. The trauma caused a significant, eight-fold increase of dialysate glycerol in the injured cortex, with the peak concentration in the second 10 min fraction after trauma. Glycerol then levelled off but remained significantly above sham-operated controls for the entire 4 h observation period in the perimeter of the injury region where scattered neuronal death is seen. The results support the concept that PL degradation occurs early after TBI and that interstitial glycerol, harvested by microdialysis, may be useful as a marker allowing in vivo monitoring of PL breakdown.

Expression of serine/threonine kinase receptors in traumatic brain injury.

The aim of this study was to investigate the expression of serine/threonine kinase receptors in the brain following traumatic brain injury. We report here that, the recently cloned and characterized bone morphogenetic protein (BMP) receptor type II (BMPR-II) and the activin receptor type IA (ActR-1) Act: mRNAs were simultaneously up-regulated in neurones in the dentate gyrus 6 h after a mild cerebral contusion injury. This findings was specific for these receptors since other investigated genes (i.e. ActR-II, ActR-IB, trkB and c-fos) showed other temporal patterns. These data suggest that type I and type II receptors act together in signal transduction in vivo and that BMPs may be involved in neuronal plasticity after traumatic brain injury.

Traumatic brain injury in rat produces changes of beta-amyloid precursor protein immunoreactivity.

beta-Amyloid precursor protein immunoreactivity (APP) was studied after a mild compression contusion trauma to rat parietal cortex. Neurones in the periphery of the cortical lesion, i.e. tissue subjected to shear stress, showed markedly reduced immunoreactivity 1 and 3 days after injury. Numerous axons in the ipsilateral subcortical white matter and thalamus became immunoreactive. At 21 days, small rounded profiles appeared in the neuropil of the damaged cortex and in the thalamus. Thus, traumatic brain injury appears to induce several types of APP changes. The accumulation in neuronal processes is probably caused by disturbed axonal transport induced by trauma. Since APP is assumed to be excitoprotective, modulating intracellular Ca2+ responses, the decreased immunoreactivity noticed in the periphery of the lesion may render the neurones in this region more vulnerable to secondary injury mechanisms.

Changes in microtubule-associated protein 2 and amyloid precursor protein immunoreactivity following traumatic brain injury in rat: influence of MK-801 treatment.

We investigated by immunohistochemistry dendritic and axonal changes occurring in the rat brain after mild focal cortical trauma produced by the weight drop technique. One and 3 days after injury, nerve cell bodies and dendrites in the perimeter of the impact site displayed decreased microtubule-associated protein 2 (MAP2) immunoreactivity. Some dendrites in the immediate adjacent region were more intensely stained and distorted. The dentate hilar region of the hippocampus showed a reduction of immunoreactive nerve cell bodies and dendrites. Twenty-one days after injury the strongly stained cortical dendrites and the reduction of immunoreactivity in the hippocampus remained, whereas the reduced staining in the perimeter of the lesion had normalised. These results indicate that there is a long-lasting disturbed dendritic organisation implicating impaired neurotransmission after this type of mild brain trauma. beta-Amyloid precursor protein (APP) immunohistochemistry revealed numerous stained axons in the ipsilateral subcortical white matter and thalamus indicating local and remote axonal injuries with disturbed axonal transport. Twenty-one days after injury, numerous small immunostained profiles appeared in the neuropil of the cortical impact site and in the ipsilateral thalamus. The axonal changes indicate disturbed connectivity between the site of the impact and other brain regions, chiefly the thalamus. The presence of beta-amyloid was investigated 21 days after trauma. There were no signs of beta-amyloid depositions in the brain after injury. Finally, we tested if the non-competitive NMDA receptor antagonist dizocilpine maleate (MK-801) could influence the observed MAP2 and APP changes. Pretreatment with this compound did not affect the early MAP2 and APP alterations. Instead, an increased expression of the APP antigen in the thalamus was observed 21 days after trauma in the MK-801-treated animals. The cause of this phenomenon is not known but may be related to a delayed neurotoxic action of MK-801 treatment.