Animal models of pediatric abusive head trauma.

BACKGROUND: Abusive head trauma (AHT), previously known as the shaken baby syndrome, is a severe and potentially fatal form of traumatic brain injury in infant children who have been shaken, and sometimes also sustained an additional head impact. The clinical and autopsy findings in AHT are not pathognomonic and, due to frequent obfuscation by perpetrators, the circumstances surrounding the alleged abuse are often unclear. The concept has evolved that the finding of the combination of subdural hemorrhage, brain injury, and retinal hemorrhages ("the triad") is the result of shaking of an infant ("shaken baby syndrome") and has led to the ongoing controversy whether shaking alone is able to generate sufficient force to produce these lesions. OBJECTIVE: In an attempt to investigate whether shaking can engender this lesion triad, animal models have been developed in laboratory rodents and domestic animal species. This review assesses the utility of these animal models to reliably reproduce human AHT pathology and evaluate the effects of shaking on the immature brain. RESULTS: Due largely to irreconcilable anatomic species differences between these animal brains and human infants, and a lack of resemblance of the experimental head shaking induced by mechanical devices to real-world human neurotrauma, no animal model has been able to reliably reproduce the full range of neuropathologic AHT changes. CONCLUSION: Some animal models can simulate specific brain and ophthalmic lesions found in human AHT cases and provide useful information on their pathogenesis. Moreover, one animal model demonstrated that shaking of a freely mobile head, without an additional head impact, could be lethal, and produce significant brain pathology.

Lysosomal LAMP1 immunoreactivity exists in both diffuse and neuritic amyloid plaques in the human hippocampus.

Lysosomal vesicles around neuritic plaques are thought to drive Alzheimer's disease by providing ideal microenvironments for generation of amyloid-ß. Although lysosomal vesicles are present at every amyloid plaque in mouse models of Alzheimer's disease, the number of amyloid plaques that contain lysosomal vesicles in the human brain remains unknown. This study aimed to quantify lysosomal vesicles at amyloid plaques in the human hippocampus. Lysosome-associated membrane protein 1 (LAMP1)-positive vesicles accumulated in both diffuse (Aß42-positive/AT8-negative) and neuritic (Aß42-positive/AT8-positive) plaques in all regions were analysed. In contrast to mouse models of Alzheimer's disease, however, not all amyloid plaques accumulated LAMP1-positive lysosomal vesicles. Even at neuritic plaques, LAMP1 immunoreactivity was more abundant than phospho-tau (AT8). Further, lysosomal vesicles colocalised weakly with phospho-tau such that accumulation of lysosomal vesicles and phospho-tau appeared to be spatially distinct events that occurred within dystrophic neurites. This quantitative study shows that diffuse plaques, as well as neuritic plaques, contain LAMP1 immunoreactivity in the human hippocampus.

Elevated Intracranial Pressure and Cerebral Edema following Permanent MCA Occlusion in an Ovine Model.

INTRODUCTION: Malignant middle cerebral artery (MCA) stroke has a disproportionately high mortality due to the rapid development of refractory space-occupying cerebral edema. Animal models are essential in developing successful anti-edema therapies; however to date poor clinical translation has been associated with the predominately used rodent models. As such, large animal gyrencephalic models of stroke are urgently needed. The aim of the study was to characterize the intracranial pressure (ICP) response to MCA occlusion in our recently developed ovine stroke model. MATERIALS AND METHODS: 30 adult female Merino sheep (n = 8-12/gp) were randomized to sham surgery, temporary or permanent proximal MCA occlusion. ICP and brain tissue oxygen were monitored for 24 hours under general anesthesia. MRI, infarct volume with triphenyltetrazolium chloride (TTC) staining and histology were performed. RESULTS: No increase in ICP, radiological evidence of ischemia within the MCA territory but without space-occupying edema, and TTC infarct volumes of 7.9+/-5.1% were seen with temporary MCAO. Permanent MCAO resulted in significantly elevated ICP, accompanied by 30% mortality, radiological evidence of space-occupying cerebral edema and TTC infarct volumes of 27.4+/-6.4%. CONCLUSIONS: Permanent proximal MCAO in the sheep results in space-occupying cerebral edema, raised ICP and mortality similar to human malignant MCA stroke. This animal model may prove useful for pre-clinical testing of anti-edema therapies that have shown promise in rodent studies.

Apoptosis in human compressive myelopathy due to metastatic neoplasia.

STUDY DESIGN: Immunohistochemical assessment of apoptotic markers in human cases of compressive myelopathy due to neoplastic compression. OBJECTIVE: To characterize the role of apoptosis in neoplastic compressive myelopathy in human postmortem tissue with extramedullary tumor involvement. SUMMARY OF BACKGROUND DATA: Neoplasms, whether primary or metastatic, may lead to compression of the spinal cord and development of a compressive myelopathy syndrome. Apoptotic processes of cell death are thought to contribute to cell death in chronic compressive myelopathy because of degenerative spondylosis, but this has not previously been described in neoplastic compression. METHODS: Six postmortem cases of human neoplastic compressive myelopathy were assessed for apoptosis using a panel of immunohistochemical markers including Fas, B-cell lymphoma 2 (Bcl-2), caspase-3 and 9, DNA-dependent protein kinase catalytic subunit (DNA-PKcs), poly (ADP-ribose) polymerase (PARP), apoptosis-inducing factor (AIF), and terminal deoxynucleotide transferase dUTP Nick End Labeling (TUNEL). RESULTS: Apoptosis was maximal at the site of tumor compression. Glial cells, predominantly oligodendrocytes, were immunopositive for DNA-PKcs, PARP, AIF, and TUNEL. Axons were immunopositive for caspase 3, DNA-PKcs, and AIF. Neurons were immunopositive for DNA-PKcs, PARP, AIF, and TUNEL. CONCLUSION: The current study demonstrates that apoptosis plays a role in human neoplastic compressive myelopathy. Necrosis dominates the severe end of the spectrum of compression. The prominent oligodendroglial involvement is suggestive that apoptosis may be important in the ongoing remodeling of white matter due to sustained compression. LEVEL OF EVIDENCE: 4.

Effect of long-term (2 years) exposure of mouse brains to global system for mobile communication (GSM) radiofrequency fields on astrocytic immunoreactivity.

This study was designed to determine whether long-term (2 years) brain exposure to mobile telephone radiofrequency (RF) fields produces any astrocytic activation as these glia react to a wide range of neural perturbations by astrogliosis. Using a purpose-designed exposure system at 900 MHz, mice were given a single, far-field whole body exposure at a specific absorption rate of 4 W/kg on five successive days per week for 104 weeks. Control mice were sham-exposed or freely mobile in a cage to control any stress caused by immobilization in the exposure module. Brains were perfusion-fixed with 4% paraformaldehyde and three coronal levels immunostained for glial fibrillary acidic protein (GFAP). These brain slices were then examined by light microscopy and the amount of this immunomarker quantified using a color deconvolution method. There was no change in astrocytic GFAP immunostaining in brains after long-term exposure to mobile telephony microwaves compared to control (sham-exposed or freely moving caged mice). It was concluded that long-term (2 years) exposure of murine brains to mobile telephone RF fields did not produce any astrocytic reaction (astrogliosis) detectable by GFAP immunostaining.

The neuroprotective activity of the amyloid precursor protein against traumatic brain injury is mediated via the heparin binding site in residues 96-110.

We have previously shown that following traumatic brain injury (TBI) the presence of the amyloid precursor protein (APP) may be neuroprotective. APP knockout mice have increased neuronal death and worse cognitive and motor outcomes following TBI, which is rescued by treatment with exogenous sAPPα (the secreted ectodomain of APP generated by α-secretase cleavage). Two neuroprotective regions were identified in sAPPα, the N and C-terminal domains D1 and D6a/E2 respectively. As both D1 and D6a/E2 contain heparin binding activity it was hypothesized that this is responsible for the neuroprotective activity. In this study, we focused on the heparin binding site, encompassed by residues 96-110 in D1, which has previously been shown to have neurotrophic properties. We found that treatment with APP96-110 rescued motor and cognitive deficits in APP-/- mice following focal TBI. APP96-110 also provided neuroprotection in Sprague-Dawley rats following diffuse TBI. Treatment with APP96-110 significantly improved functional outcome as well as preserve histological cellular morphology in APP-/- mice following focal controlled cortical impact injury. Furthermore, following administration of APP96-110 in rats after diffuse impact acceleration TBI, motor and cognitive outcomes were significantly improved and axonal injury reduced. These data define the heparin binding site in the D1 domain of sAPPα, represented by the sequence APP96-110, as the neuroprotective site to confer neuroprotection following TBI. The product of α-secretase cleavage of the amyloid precursor protein, sAPPα is neuroprotective following traumatic brain injury (TBI). Of interest was whether this neuroprotective activity could be further delineated to a heparin binding region within sAPPα, corresponding to the region APP96-110 (see diagram demonstrating the domain structure of sAPPα). Indeed treatment with APP96-110 improved functional outcome following TBI, an effect that was not seen with a mutated version of the peptide that had reduced heparin binding affinity.

Major histocompatibility complex class I and II expression in idiopathic inflammatory myopathy.

INTRODUCTION: We sought to study the intensity and pattern of major histocompatibility complex (MHC) I and II expression in muscle from patients with biopsy-proven idiopathic inflammatory myositis (IIM) including the subgroups, polymyositis (PM), dermatomyositis (DM), and inclusion body myositis (IBM). METHODS: A total of 120 muscle biopsies (61 PM, 14 DM, and 45 IBM) were immunostained for MHC I and II. Staining was graded as follows. 0: no staining, 1+: ≤10% fibers, 2+: 10% to 25%, 3+: 25% to 50%, 4+: 50% to 99%, and 5+ 100%. RESULTS: All IIM biopsies showed MHC I positivity; 93% showed MHC II positivity. The proportion of patients with MHC II score ≥3+ was higher in IBM than DM or PM. In DM, MHC I expression showed a perifascicular pattern. All IBM biopsies were immunopositive for MHC I and II; 30/45 were scored 5+. DISCUSSION: Immunostaining for MHC I and II is a useful adjunctive test in diagnosis and subclassification of IIM.

A surgical model of permanent and transient middle cerebral artery stroke in the sheep.

BACKGROUND: Animal models are essential to study the pathophysiological changes associated with focal occlusive stroke and to investigate novel therapies. Currently used rodent models have yielded little clinical success, however large animal models may provide a more suitable alternative to improve clinical translation. We sought to develop a model of acute proximal middle cerebral artery (MCA) ischemic stroke in sheep, including both permanent occlusion and transient occlusion with reperfusion. MATERIALS AND METHODS: 18 adult male and female Merino sheep were randomly allocated to one of three groups (n = 6/gp): 1) sham surgery; 2) permanent proximal MCA occlusion (MCAO); or 3) temporary MCAO with aneurysm clip. All animals had invasive arterial blood pressure, intracranial pressure and brain tissue oxygen monitoring. At 4 h following vessel occlusion or sham surgery animals were killed by perfusion fixation. Brains were processed for histopathological examination and infarct area determination. 6 further animals were randomized to either permanent (n = 3) or temporary MCAO (n = 3) and then had magnetic resonance imaging (MRI) at 4 h after MCAO. RESULTS: Evidence of ischemic injury in an MCA distribution was seen in all stroke animals. The ischemic lesion area was significantly larger after permanent (28.8%) compared with temporary MCAO (14.6%). Sham animals demonstrated no evidence of ischemic injury. There was a significant reduction in brain tissue oxygen partial pressure after permanent vessel occlusion between 30 and 210 mins after MCAO. MRI at 4 h demonstrated complete proximal MCA occlusion in the permanent MCAO animals with a diffusion deficit involving the whole right MCA territory, whereas temporary MCAO animals demonstrated MRA evidence of flow within the right MCA and smaller predominantly cortical diffusion deficits. CONCLUSIONS: Proximal MCAO can be achieved in an ovine model of stroke via a surgical approach. Permanent occlusion creates larger infarct volumes, however aneurysm clip application allows for reperfusion.

sAPPα rescues deficits in amyloid precursor protein knockout mice following focal traumatic brain injury.

The amyloid precursor protein (APP) is thought to be neuroprotective following traumatic brain injury (TBI), although definitive evidence at moderate to severe levels of injury is lacking. In the current study, we investigated histological and functional outcomes in APP-/- mice compared with APP+/+ mice following a moderate focal injury, and whether administration of sAPPα restored the outcomes in knockout animals back to the wildtype state. Following moderate controlled cortical impact injury, APP-/- mice demonstrated greater impairment in motor and cognitive outcome as determined by the ledged beam and Barnes Maze tests respectively (p < 0.05). This corresponded with the degree of neuronal damage, with APP-/- mice having significantly greater lesion volume (25.0 ± 1.6 vs. 20.3 ± 1.6%, p < 0.01) and hippocampal damage, with less remaining CA neurons (839 ± 245 vs. 1353 ± 142 and 1401 ± 263). This was also associated with an impaired neuroreparative response, with decreased GAP-43 immunoreactivity within the cortex around the lesion edge compared with APP+/+ mice. The deficits observed in the APP-/- mice related to a lack of sAPPα, as treatment with exogenously added sAPPα post-injury improved APP-/- mice histological and functional outcome to the point that they were no longer significantly different to APP+/+ mice (p < 0.05). This study shows that endogenous APP is potentially protective at moderate levels of TBI, and that this neuroprotective activity is related to the presence of sAPPα. Importantly, it indicates that the mechanism of action of exogenously added sAPPα is independent of the presence of endogenous APP.

Characterisation of the effect of knockout of the amyloid precursor protein on outcome following mild traumatic brain injury.

The amyloid precursor protein (APP) increases following traumatic brain injury (TBI), although the functional significance of this remains unclear largely because the functions of the subsequent APP metabolites are so different: Aß is neurotoxic whilst sAPPα is neuroprotective. To investigate this further, APP wildtype and knockout mice were subjected to mild diffuse TBI and their outcomes compared. APP knockout mice displayed significantly worse cognitive and motor deficits, as demonstrated by the Barnes Maze and rotarod respectively, than APP wildtype mice. This was associated with a significant increase in hippocampal and cortical cell loss, as well as axonal injury, in APP knockout mice and an impaired neuroreparative response as indicated by diminished GAP-43 immunoreactivity when compared to APP wildtype mice. This study is the first to demonstrate that endogenous APP is beneficial following mild TBI, suggesting that the upregulation of APP observed following injury is an acute protective response.

Evaluation of the effects of treatment with sAPPα on functional and histological outcome following controlled cortical impact injury in mice.

Treatment with sAPPα, the product of non-amyloidogenic processing of the amyloid precursor protein (APP) has been shown to be protective following diffuse traumatic brain injury (TBI), by improving motor outcome and reducing axonal injury. However the effects of treatment with sAPPα following a focal TBI have yet to be determined. To investigate this, mice were subjected to a controlled cortical impact injury and treated with either sAPPα or its vehicle at 30 min post-injury. Following treatment with sAPPα the mice showed a significant improvement in motor and cognitive function early following injury, as determined on the ledged beam and Barnes Maze, respectively, relating to a more rapid rate of recovery. However the effect of treatment with sAPPα was not as dramatic as that seen previously following a diffuse injury. Nonetheless, these improvements in functional outcome were acompanied by a small but significant improvement in the amount of cortical and hippocampal at 7 days post-injury, and provide further support for the efficacy of sAPPα as a potential neuroprotective agent following TBI.

Aquaporin-4 expression after experimental contusional injury in an ovine impact-acceleration head injury model.

Cerebral contusions are one of the principal lesions of traumatic brain injury and the attendant oedema formation contributes substantially to the clinicopathological manifestations. While it is now recognised that the membrane channel protein aquaporin-4 (AQP-4) plays a major role in the development and resolution of cerebral oedema, assessments of its expression in and around contusions have produced conflicting results. We used an ovine impact-acceleration model of closed head injury to examine contusion-related AQP-4 expression and found that there was a heterogeneous AQP-4 response within contusions, with some astrocytes being nonviable and immunonegative, while others showed increased AQP-4 expression. Pericontusional astrocytes in the penumbra region generally showed more robust AQP-4 immunopositivity than intracontusional glia. Thus, manipulation of AQP-4 expression could have therapeutic applications in controlling cerebral oedema associated with contusions.

The neuroprotective domains of the amyloid precursor protein, in traumatic brain injury, are located in the two growth factor domains.

The amyloid precursor protein (APP) is known to increase following traumatic brain injury (TBI). This increase in levels of APP may be deleterious to outcome due to the production of neurotoxic Aß. Conversely, this upregulation may be beneficial as cleavage of APP via the alternative non-amyloidogenic pathway produces the soluble α form of APP (sAPPα), which is known to have many neuroprotective and neurotrophic functions. Indeed it has previously been shown that treatment with sAPPα following a diffuse injury in rats improves outcome. However, the exact location within the sAPPα molecule which contains this neuroprotective activity has yet to be determined. The sAPPα peptide can consist of up to 6 domains, with the main isoform in the brain missing the 4th and 5th. Of the remaining domains, the D1 and D6a domains seem the most likely as they have been shown to have beneficial actions in vitro. This present study examined the effects of in vivo posttraumatic administration via an intracerebroventricular injection of the D1, D2 and D6a domains of sAPPα on outcome following moderate-impact acceleration TBI in rats. While treatment with either the D1 or D6a domains was found to significantly improve motor and cognitive outcome, as assessed on the rotarod and Y maze, treatment with the D2 domain had no effect. Furthermore axonal injury was reduced in D1 and D6a domain treated animals, but not those that received the D2 domain. As the D1 and D6a domains contain a heparin binding region while the D2 domain does not, this suggests that sAPPα mediates its neuroprotective response through its ability to bind to heparin sulfate proteoglycans.

Transmission of Synucleinopathies in the Enteric Nervous System of A53T Alpha-Synuclein Transgenic Mice.

Parkinson's disease (PD) and dementia with Lewy bodies (DLB) are characterized by abnormal deposition of α-synuclein aggregates in many regions of the central and peripheral nervous systems. Accumulating evidence suggests that the α-synuclein pathology initiates in a few discrete regions and spreads to larger areas in the nervous system. Recent pathological studies of PD patients have raised the possibility that the enteric nervous system is one of the initial sites of α-synuclein aggregation and propagation. Here, we evaluated the induction and propagation of α-synuclein aggregates in the enteric nervous system of the A53T α-synuclein transgenic mice after injection of human brain tissue extracts into the gastric walls of the mice. Western analysis of the brain extracts showed that the DLB extract contained detergent-stable α-synuclein aggregates, but the normal brain extract did not. Injection of the DLB extract resulted in an increased deposition of α-synuclein in the myenteric neurons, in which α-synuclein formed punctate aggregates over time up to 4 months. In these mice, inflammatory responses were increased transiently at early time points. None of these changes were observed in the A53T mice injected with saline or the normal brain extract, nor were these found in the wild type mice injected with the DLB extract. These results demonstrate that pathological α-synuclein aggregates present in the brain of DLB patient can induce the aggregation of endogenous α-synuclein in the myenteric neurons in A53T mice, suggesting the transmission of synucleinopathy lesions in the enteric nervous system.

A substance P antagonist reduces axonal injury and improves neurologic outcome when administered up to 12 hours after traumatic brain injury.

Previous studies have demonstrated that the compound N-acetyl-L-tryptophan (NAT) reduces brain edema and improves functional outcome following traumatic brain injury (TBI). In this study we examined whether this effect was mediated via the neurokinin-1 receptor, and whether there was an effect on axonal injury. We also explored whether the compound was effective, even when administered at delayed time points. Male Sprague-Dawley rats were subject to acceleration-induced, diffuse TBI and administered NAT, its inactive D-enantiomer, or saline vehicle. In contrast to NAT (2.5 mg/kg), the inactive D-enantiomer was ineffective at improving rotarod motor performance after TBI. NAT also improved cognitive outcome as assessed by the Morris water maze and novel object recognition tests, and reduced axonal injury at 5 and 24 h after TBI as assessed by amyloid precursor protein immunohistochemistry. However, efficacy of the membrane-impermeable NAT was limited to administration within 5 h, whereas administration of a form of NAT, L-732,138 (47 mg/kg), in which a trifluoromethyl benzyl ester group has been added, making it highly lipid soluble and able to cross the intact blood-brain barrier, significantly improved motor outcome, even when administration was delayed by as much as 12 h. We conclude that the neuroprotective effects of NAT are receptor-mediated, and that administration of the membrane-permeable form of the compound can be effective even up to 12 h after TBI.

Wallerian-like axonal degeneration in the optic nerve after excitotoxic retinal insult: an ultrastructural study.

BACKGROUND: Excitotoxicity is involved in the pathogenesis of a number neurodegenerative diseases, and axonopathy is an early feature in several of these disorders. In models of excitotoxicity-associated neurological disease, an excitotoxin delivered to the central nervous system (CNS), could trigger neuronal death not only in the somatodendritic region, but also in the axonal region, via oligodendrocyte N-methyl-D-aspartate (NMDA) receptors. The retina and optic nerve, as approachable regions of the brain, provide a unique anatomical substrate to investigate the "downstream" effect of isolated excitotoxic perikaryal injury on central nervous system (CNS) axons, potentially providing information about the pathogenesis of the axonopathy in clinical neurological disorders.Herein, we provide ultrastructural information about the retinal ganglion cell (RGC) somata and their axons, both unmyelinated and myelinated, after NMDA-induced retinal injury. Male Sprague-Dawley rats were killed at 0 h, 24 h, 72 h and 7 days after injecting 20 nM NMDA into the vitreous chamber of the left eye (n = 8 in each group). Saline-injected right eyes served as controls. After perfusion fixation, dissection, resin-embedding and staining, ultrathin sections of eyes and proximal (intraorbital) and distal (intracranial) optic nerve segments were evaluated by transmission electron tomography (TEM). RESULTS: TEM demonstrated features of necrosis in RGCs: mitochondrial and endoplasmic reticulum swelling, disintegration of polyribosomes, rupture of membranous organelle and formation of myelin bodies. Ultrastructural damage in the optic nerve mimicked the changes of Wallerian degeneration; early nodal/paranodal disturbances were followed by the appearance of three major morphological variants: dark degeneration, watery degeneration and demyelination. CONCLUSION: NMDA-induced excitotoxic retinal injury causes mainly necrotic RGC somal death with Wallerian-like degeneration of the optic nerve. Since axonal degeneration associated with perikaryal excitotoxic injury is an active, regulated process, it may be amenable to therapeutic intervention.

Innervation of anulus tears: an experimental animal study.

STUDY DESIGN: A prospective immunohistological study in an animal model. OBJECTIVE: To identify and describe the phenotype of neoinnervation in experimental anular tears. SUMMARY OF BACKGROUND DATA: Controversy surrounds neoinnervation of degenerate discs which has been proposed as the anatomic basis for discogenic pain. Ablation of neoinnervation has been postulated as the theoretical basis for the claimed successes of procedures such as intradiscal electrotherapy. The animal model of disc degeneration previously developed in our research center provides an opportunity to investigate the innervation of anular tears in an extensively characterized lesion. METHODS: A surgical anular tear was created in 5 lumbar discs in 11 sheep which were killed at 1, 2, 3, and 12 months. Each spine was x-rayed and divided into motion segments for histologic analysis. Serial sections through the tear were immunostained for protein gene product 9.5, tyrosine hydroxylase, and calcitonin gene receptor protein. RESULTS: Neoinnervation of the periphery of the anular tear was observed. Ingrowing nerves penetrated marginally deeper than the normal anular innervation but no nerves were identified in the inner anulus or nucleus. A minority of the new axons were calcitonin gene receptor protein or tyrosine hydroxylase positive. CONCLUSION: The anulus tears in this model are innervated only peripherally to a depth only marginally greater than that of the normal anulus.

Microglial activation as a measure of stress in mouse brains exposed acutely (60 minutes) and long-term (2 years) to mobile telephone radiofrequency fields.

AIM: To determine whether acute or long-term exposure of the brain to mobile telephone radiofrequency (RF) fields produces activation of microglia, which normally respond rapidly to any change in their microenvironment. METHODS: Using a purpose designed exposure system at 900 MHz, mice were given a single, far-field whole body exposure at a specific absorption rate (SAR) of 4 W/kg for 60 min (acute) or on five successive days per week for 104 weeks (long-term). Control mice were sham-exposed or freely mobile in a cage to control for any stress caused by immobilisation in the exposure module. Positive control brains subjected to a stab wound were also included to confirm the ability of microglia to react to any neural stress. Brains were perfusion-fixed with 4% paraformaldehyde and representative regions of the cerebral cortex and hippocampus immunostained for ionised calcium binding adaptor molecule (Iba1), a specific microglial marker. RESULTS: There was no increase in microglial Iba1 expression in brains short or long-term exposed to mobile telephony microwaves compared to control (sham-exposed or freely moving caged mice) brains, while substantial microglial activation occurred in damaged positive control neural tissue. CONCLUSION: Acute (60 minutes) or longer duration (2 years) exposure of murine brains to mobile telephone RF fields did not produce any microglial activation detectable by Iba1 immunostaining.

Diffuse neuronal perikaryal amyloid precursor protein immunoreactivity in an ovine model of non-accidental head injury (the shaken baby syndrome).

Non-accidental head injury ("shaken baby syndrome") is a major cause of death and disability in infants and young children, but it is uncertain whether shaking alone is sufficient to cause brain damage or an additional head impact is required. Accordingly, we used manual shaking in an ovine model in an attempt to answer this question since lambs have a relatively large gyrencephalic brain and weak neck muscles resembling a human infant. Neuronal perikaryal and axonal reactions were quantified 6 hours after shaking using amyloid precursor protein (APP) immunohistochemistry. Neuronal perikaryal APP was widely distributed in the brain and spinal cord, the first time such a diffuse neuronal stress response after shaking has been demonstrated, but axonal immunoreactivity was minimal and largely confined to the rostral cervical spinal cord at the site of maximal loading. No ischaemic-hypoxic damage was found in haematoxylin and eosin-stained sections.

Substance P immunoreactivity increases following human traumatic brain injury.

Recent experimental evidence suggests that neuropeptides, and in particular substance P (SP), are released following traumatic brain injury (TBI) and may play a significant role in the aetiology of cerebral edema and increased intracranial pressure. Whether SP may play a similar role in clinical TBI remains unknown and was investigated in the current study. Archival post-mortem material was selected from patients who had sustained TBI, had died and had undergone post-mortem and detailed neuropathological examination (n = 13). A second cohort of patients who had died, but who showed no neuropathological abnormality (n = 10), served as case controls. Changes in SP immunoreactivity were examined in the cerebral cortex directly beneath the subdural haematoma in 7 TBI cases and in proximity to contusions in the other 6 cases. Increased SP perivascular immunoreactivity was observed after TBI in 10/13 cases, cortical neurones in 12/13 and astrocytes in 10/13 cases. Perivascular axonal injury was observed by amyloid precursor protein (APP) immunoreactivity in 6/13 TBI cases. Co-localization of SP and APP in a small subset of perivascular fibres suggests perivascular axonal injury could be a mechanism of release of this neuropeptide. The abundance of SP fibres around the human cerebral microvasculature, particularly post capillary venules, together with the changes observed following TBI in perivascular axons, cortical neurones and astrocytes suggest a potentially important role for substance P in neurogenic inflammation following human TBI.