Focal ischemic damage is reduced by CPP-ene studies in two animal models

We have studied a new high-affinity competitive N-methyl-D-aspartate antagonist, D-CPP-ene (SDZ-EAA 494), in two models of focal cerebral ischemia. In the cat middle cerebral artery occlusion model (6 hours' survival), pretreatment with D-CPP-ene reduced infarct size by 64% (15 mg/kg dose) and 60% (4.5 mg/kg dose). There was no reduction in infarct size at a dose of 1.5 mg/kg. Treatment 1 hour after the occlusion reduced infarct size slightly, but not significantly. In a new model of subdural hematoma in the rat, the zone of cortical ischemic damage beneath the blood clot was reduced by 54% with D-CPP-ene pretreatment. Neuroprotective efficacy in a gyrencephalic species comparable to that of noncompetitive antagonists thus can be achieved with this agent. These experiments also indicate that competitive N-methyl-D-aspartate antagonists may be clinically useful after traumatic intracranial hematomas.

Focal cerebral ischemia in the cat: pretreatment with a competitive NMDA receptor antagonist, D-CPP-ene

The effects of the competitive N-methyl-D-aspartate (NMDA) receptor antagonist D-(E)-4-(3-phosphonoprop-2-enyl)piperazine-2-carboxylic acid (D-CPP-ene; SDZ EAA 494) upon ischemic brain damage have been examined in anesthetized cats. Focal cerebral ischemia was produced by permanent occlusion of the middle cerebral artery (MCA) and the animals were killed 6 h later. The amount of early ischemic brain damage was assessed in coronal sections at 16 predetermined stereotaxic planes. Pretreatment with D-CPP-ene (15 mg/kg i.v. followed by continuous infusion at 0.17 mg/kg/min until death), 15 min prior to MCA occlusion, significantly reduced the volume of ischemic brain damage (from 20.6 +/- 9.9% of the cerebral hemisphere in vehicle-treated cats to 7.2 +/- 4.4% in drug-treated cats; p less than 0.01). The competitive NMDA receptor antagonist D-CPP-ene is as effective as noncompetitive NMDA antagonists in reducing the amount of ischemic brain damage in this model of focal cerebral ischemia in a gyrencephalic species.

Ischemic brain damage in a model of acute subdural hematoma

Ischemic brain damage is the most important neuropathological finding in humans who die after acute subdural hematoma; however, its causes are poorly understood. We have produced acute subdural hematoma in the rat by injecting 400 microliters of autologous blood (approximately 20% of intracranial volume) into the subdural space. Extensive areas of ischemic damage, involving 14 to 16% of the volume of the hemisphere, developed in this model at 4 and 24 hours after the lesion. The hematomas were associated with a brief peak in intracranial pressure (51 mm Hg), which remained at three times normal levels (14 mm Hg) for 3 hours. In this model, therefore, ischemic damage appears to be due to the local effects of blood overlying the cortex at 4 hours after the ictus, rather than to globally raised intracranial pressure. The implications for the pathophysiology of acute subdural hematomas in humans are discussed.

Studies on the pathogenesis of neurological diseases associated with Varicella-Zoster virus

Immunocytochemical techniques and in situ hybridization with three different Varicella-Zoster Virus (VZV)-specific RNA probes have been used to study the pathogenesis of VZV-associated neurological syndromes. Varicella-Zoster Virus antigens were not detected using the avidin-biotin peroxidase technique with a polyvalent anti-VZV antibody in any of the formalin-fixed tissue sections from eight cases of VZV-associated neurological disease (encephalitis, myelitis, ganglionitis); one case was immunosuppressed although inflammatory lesions were present. Intense labelling was detected within the inflammatory lesions in several representative VZV cases with a monoclonal antibody against Class II MHC antigens, whereas cases of Herpes Simplex Virus encephalitis and normal controls were not so labelled. Three VZV probes from open reading frames 62, 16 and 40, which show homology with the Herpes Simplex Virus immediate early 175 kd protein, the 65 kd DNA binding protein and the major capsid protein respectively, were used for in situ hybridization studies in these VZV tissues. Although the probes were able to detect VZV RNA in VZV-infected CV-1 and Flow 2002 cell cultures and formalin-fixed VZV skin biopsy sections, positive hybridization was not seen in any of the neurological cases studied. Thus neither VZV nucleic acid nor antigens were detected in any of the cases of VZV-associated neurological disease. It is proposed that the mechanism of neurological damage in the syndromes is immune-mediated, there being increased expression of Class II MHC antigens associated with persistent inflammation.

The JH2604 deletion variant of herpes simplex virus type 2 (HG52) fails to produce necrotizing encephalitis following intracranial inoculation of mice

The pathological changes and distribution of virus antigen in mouse brains were studied following intracranial inoculation of 3 week old BALB/c mice with the herpes simplex virus (HSV) type 2 strain HG52 and its deletion variant JH2604. The variant JH2604 failed to produce necrotizing encephalitis compared to the parental HG52. The morphological changes induced in JH2604-infected brains consisted of localized perivascular cuffing by lymphocytes and infiltration by immune cells. Immunohistochemical studies using polyclonal anti-HSV serum showed that JH2604 antigens were localized at the site of inoculation with no evidence of neuronal involvement. Wild-type HSV-infected brains demonstrated a wide distribution of antigens both in neuronal and supporting cells. These data provide evidence that the non-neurovirulent phenotype of JH2604 is due to inability to replicate within neuronal cells of the central nervous system and pinpoints a precise role for the HG52 sequences contained within the 1488 bp subfragment of TRL/IRL deleted in JH2604.

5 HT2 receptors in dementia of Alzheimer type: a quantitative autoradiographic study of frontal cortex and hippocampus

Using both quantitative autoradiography in sections and a homogenate preparation assay, the distribution and density of 3H-ketanserin binding to 5 HT2 receptors was examined in frontal cortex and the hippocampal region from six control subjects and seven subjects who had dementia of the Alzheimer type (DAT). There was no difference between control and DAT subjects in the levels of ketanserin binding in any region of the frontal cortex or hippocampus determined by quantitative autoradiography or in parallel experiments using homogenate preparations (e.g. left frontal cortex, layer III; controls, 34.4 +/- 1.6 pmol/g, DAT, 37.1 +/- 4.6 pmol/g). In all of the DAT brains there were abundant neuritic plaques (e.g. superficial layers of left frontal cortex; 35 +/- 7 plaques/mm2), and a marked reduction of choline acetyltransferase activity, (by 30-60% relative to controls), in both frontal cortex and the hippocampus. Thus, despite the presence of morphological abnormalities and a loss of cholinergic function, two classic features of DAT, 5 HT2 receptor binding was unaltered in this group of DAT brains compared to controls.

Experimental autoimmune uveoretinitis and pinealitis induced by interphotoreceptor retinoid-binding protein and S-antigen: induction of intraretinal and subretinal neovascularization

Experimental autoimmune uveoretinitis (EAU) and pinealitis were induced in Lewis rats following hind foot pad injection of interphotoreceptor retinoid-binding protein (IRBP) or S-antigen. A comparison is made in this study of the in vivo and histological changes in uveoretinitis and pinealitis induced by administering similar doses of highly-purified IRBP and S-antigen emulsified in complete Freund's adjuvant (CFA). The time of onset of ocular inflammation after inoculation was slightly later in S-antigen (14-18 days) as compared with IRBP-inoculated animals (10-14 days), while the severity of the inflammation was lower in the latter group. The distribution of inflammation in the anterior segment was similar in both the S-antigen and IRBP sensitized animals but there was major variation in the location of the posterior segment disease. Vasculitis was a predominant feature of IRBP induced disease while chorioretinitis and photoreceptor destruction was more prominent in the S-antigen sensitized animals. A striking feature of this study is that both antigens induced intraretinal and subretinal neovascularization, an observation which has not been reported previously. Inflammation was induced in all pineal glands and as with EAU the severity was closely related to the type of antigen inoculated.

Glycogen accumulation in axons after stretch injury

Thin-section cytochemistry has been used to demonstrate the formation of glycogen deposits within axons after stretch injury to the optic nerve of adult guinea pigs in a model of focal axonal injury. Glycogen deposits occurred within 17% of structurally normal but, we suggest, damaged fibres within the stretched optic nerve. Adjacent fibres did not stain for glycogen. Small numbers of beta glycogen particles were present 15 min after injury within damaged axons and increasing numbers of particles occurred until 72 h. Degeneration bulbs formed by 72 h, but beta glycogen particles were sparse within these. By 7-14 days after injury there was a marked reduction in the numbers of glycogen particles within axons. Alpha rosettes of glycogen were infrequent within damaged axons. Deposition of glycogen particles within astrocytes after nerve injury was confirmed. Alpha rosettes of glycogen occurred within astrocytes by 6 h and remained until 14 days after injury. Possible mechanisms for the development of glycogen deposits within damaged axons are discussed in relation to a hypothesized influx of Ca2+ at the time of injury into damaged axons. We suggest that glycogen deposition within reactive axons reflects Ca2+ mediated alteration of glycogen synthase activity and compromized axonal transport.

Selective alterations of high affinity [3H]forskolin binding sites in Alzheimer's disease: a quantitative autoradiographic study

Quantitative autoradiographic analysis of high affinity [3H]forskolin binding sites was carried out in postmortem brains from normal controls and patients dying with Alzheimer's disease. Choline acetyltransferase (ChAT) activity and senile plaque formation were also quantified. [3H]Forskolin binding was markedly reduced in all layers of middle frontal gyrus in the Alzheimer brains and the deficit correlated with the deficit in ChAT activity in this area. In the hippocampal region [3H]forskolin binding was no different in the Alzheimer brains compared to controls, although ChAT activity was significantly reduced. There was an inconsistent reduction in [3H]forskolin binding in all layers of middle temporal gyrus which did not correlate with the cholinergic deficit. Significant senile plaque formation was observed in all 3 brain regions examined and [3H]forskolin binding did not correlate with plaque formation in any brain region. Thus, while all 3 brain regions were affected by the pathological correlates of Alzheimer's disease, [3H]forskolin binding was consistently reduced only in frontal cortex.

Neuropathologic consequences of internal carotid artery occlusion and hemorrhagic hypotension in baboons

We studied eight anesthetized and physiologically monitored adult baboons (Papio cyanocephalus); four were subjected to hemorrhagic hypotension alone and four to hemorrhagic hypotension plus unilateral carotid artery occlusion. Cerebral blood flow was measured using xenon-133, the electroencephalogram was recorded using silver-silver chloride epidural electrodes, and histologic examination was carried out after perfusion-fixation. In the baboons subjected to hypotension alone (mean arterial blood pressure of 28 mm Hg) cerebral blood flow was 28.5 +/- 5.0 ml/100 g/min, whereas in the baboons subjected to hypotension plus unilateral carotid artery occlusion it was 21.8 +/- 1.8 ml/100 g/min at a mean arterial blood pressure of 27 mm Hg. There was no ischemic damage in the former group, but in the latter group there was necrosis in the arterial boundary zones of three baboons and in the distribution of the middle cerebral artery in one. We conclude that, when combined with hypotension, unilateral carotid artery occlusion may lead to hemodynamic ischemia accentuated in the arterial boundary zones of the ipsilateral cerebral hemisphere.

Differential alterations of cortical glutamatergic binding sites in senile dementia of the Alzheimer type

Involvement of cortical glutamatergic mechanisms in senile dementia of the Alzheimer type (SDAT) has been investigated with quantitative ligand-binding autoradiography. The distribution and density of Na(+)-dependent glutamate uptake sites and glutamate receptor subtypes--kainate, quisqualate, and N-methyl-D-aspartate--were measured in adjacent sections of frontal cortex obtained postmortem from six patients with SDAT and six age-matched controls. The number of senile plaques was determined in the same brain region. Binding of D-[3H]aspartate to Na(+)-dependent uptake sites was reduced by approximately 40% throughout SDAT frontal cortex relative to controls, indicating a general loss of glutamatergic presynaptic terminals. [3H]Kainate receptor binding was significantly increased by approximately 70% in deep layers of SDAT frontal cortex compared with controls, whereas this binding was unaltered in superficial laminae. There was a positive correlation (r = 0.914) between kainate binding and senile plaque number in deep cortical layers. Quisqualate receptors, as assessed by 2-amino-3-hydroxy-5-[3H]methylisoxazole-4-propionic acid binding, were unaltered in SDAT frontal cortex compared with controls. There was a small reduction (25%) in N-methyl-D-aspartate-sensitive [3H]glutamate binding only in superficial cortical layers of SDAT brains relative to control subjects. [3H]Glutamate binding in SDAT subjects was unrelated to senile plaque number in superficial cortical layers (r = 0.104). These results indicate that in the presence of cortical glutamatergic terminal loss in SDAT plastic alterations occur in some glutamate receptor subtypes but not in others.

Blood-brain barrier damage in traumatic brain contusions

Plasma proteins were used as an endogenous marker of blood-brain barrier damage in 19 patients dying with traumatic cortical contusions. Patients survived for a few hours to 31 days after head injury. Eight proteins (M WT 61-2,500 x 10(3) were demonstrated with standard immunohistochemical techniques. Proteins were not found in "control" brains or in macroscopically normal parasagittal cortex in the head injury patients. Proteins were found in all of the macroscopic contusion in all brains. Protein leakage appeared to be from the contusion itself. Protein staining around histologically normal vessels was unusual. There was a gradient of staining from the macroscopic contusion into the surrounding brain. There was a trend for staining to be most marked between 3 and 8 days survival after head injury. There was no gradient of leakage by molecular size of the protein.

Experimental intracerebral haematoma: the role of blood constituents in early ischaemia

In patients with intracerebral haematoma, ischaemic damage and final outcome are often more serious than the size of the lesion would suggest. The aetiology of the ischaemia in relation to space-occupying effects or specific factors present in blood is unclear. In a rat model of an intracerebral space-occupying lesion, the pathophysiological effects of a haematoma were compared with those of an equal volume of inert fluid (mock cerebrospinal fluid [CSF] or silicone oil). Cerebral blood flow was measured at 1 min by 14C iodoantipyrine autoradiography, and ischaemic cell damage was assessed by light microscopy at 4 h. In all animals, cerebral blood flow was reduced immediately adjacent to the lesion. In the group with a haematoma, blood flow was reduced (p less than 0.001) over a greater radius and also in the ipsilateral frontal and parietal cortex. Ischaemic damage was seen in animals lesioned with blood or oil of blood viscosity, but not in animals with CSF lesions. These data suggest that both tissue pressure and vasoactive substances are components of the immediate reduction in blood flow following intracranial haemorrhage. Tissue pressure may be the more important factor in later ischaemic neuronal damage.

Idiopathic granulomatous meningitis

A 69 year old female presented with eight discrete episodes of paraparesis over a period of six weeks. Each episode lasted between 10 and 30 minutes and resolved spontaneously. The cause of her symptoms was not established during life and at necropsy she was found to have granulomatous meningitis of the cerebral convexites. The clinical and pathological aspects of this rare condition are discussed.

Experimental intracerebral haematoma in the rat: sequential light microscopical changes

In a small animal model of controlled intracerebral haemorrhage, changes within the haematoma and surrounding tissues were examined by light microscopy in toluidine blue stained semithin sections. Groups of animals were killed at 2, 6, 15, 24 and 48 hours, 2, 4, 8 and 14 days, and 3 months survival. Sequential changes in neurons, glia and leucocytes, together with the gradual absorption of the blood clot and its replacement by an astrocytic scar are described.

Propofol: effects on indices of cerebral ischemia

The effects of propofol given before and during a period of profound hypotension that caused incomplete global cerebral ischaemia were investigated in anaesthetised cats. Cortical cerebral blood flow, extracellular fluid pH, potassium and calcium ion activities, and electroencephalogram were recorded. Neuropathological outcome was also assessed. Propofol-treated animals had higher cerebral blood flows than control animals after the period of hypotension (p <0.05); they also had better correction of extracellular fluid acidosis and hyperkalaemia (p <0.01) and a late improvement in calcium ion activity (p <0.05). Neuropathological outcome was not significantly different between the groups.

Axonal injury in the optic nerve: a model simulating diffuse axonal injury in the brain

A new model of traumatic axonal injury has been developed by causing a single, rapid, controlled elongation (tensile strain) in the optic nerve of the albino guinea pig. Electron microscopy demonstrates axonal swelling, axolemmal blebs, and accumulation of organelles identical to those seen in human and experimental brain injury. Quantitative morphometric studies confirm that 17% of the optic nerve axons are injured without vascular disruption, and horseradish peroxidase (HRP) studies confirm alterations in rapid axoplasmic transport at the sites of injury. Since 95% to 98% of the optic nerve fibers are crossed, studies of the cell bodies and terminal fields of injured axons can be performed in this model. Glucose utilization was increased in the retina following injury, confirming electron microscopic changes of central chromatolysis in the ganglion cells and increased metabolic activity in reaction to axonal injury. Decreased activity at the superior colliculus was demonstrated by delayed HRP arrival after injury. The model is unique because it produces axonal damage that is morphologically identical to that seen in human brain injury and does so by delivering tissue strains of the same type and magnitude that cause axonal damage in the human. The model offers the possibility of improving the understanding of traumatic damage of central nervous system (CNS) axons because it creates reproducible axonal injury in a well-defined anatomical system that obviates many of the difficulties associated with studying the complex morphology of the brain.

Diffuse axonal injury in head injury: definition, diagnosis and grading

Diffuse axonal injury is one of the most important types of brain damage that can occur as a result of non-missile head injury, and it may be very difficult to diagnose post mortem unless the pathologist knows precisely what he is looking for. Increasing experience with fatal non-missile head injury in man has allowed the identification of three grades of diffuse axonal injury. In grade 1 there is histological evidence of axonal injury in the white matter of the cerebral hemispheres, the corpus callosum, the brain stem and, less commonly, the cerebellum; in grade 2 there is also a focal lesion in the corpus callosum; and in grade 3 there is in addition a focal lesion in the dorsolateral quadrant or quadrants of the rostral brain stem. The focal lesions can often only be identified microscopically. Diffuse axonal injury was identified in 122 of a series of 434 fatal non-missile head injuries--10 grade 1, 29 grade 2 and 83 grade 3. In 24 of these cases the diagnosis could not have been made without microscopical examination, while in a further 31 microscopical examination was required to establish its severity.

Ischaemic brain damage is still common in fatal non-missile head injury

A detailed neuropathological examination has been undertaken on a consecutive series of head injuries dying in the Institute of Neurological Sciences, Glasgow, between 1968-72 (151 cases) and 1981-82 (112 cases) in order to determine the frequency and distribution of any ischaemic brain damage. Ischaemic damage was found in the brains of 92% of the 1968-72 cases and in 88% of the 1981-82 cases: there was no statistical difference in the amount of moderately severe and severe ischaemic damage in the two groups, 55% and 54% respectively. There was evidence, however, that an increased number of patients with severe ischaemic brain damage was admitted in 1981-82 as a result of a changed admission policy of the Department of Neurosurgery that resulted in an increased detection of intracranial haematomas. It is concluded that ischaemic brain damage is still common after severe head injury, and it seems likely that it remains an important cause of mortality and morbidity.

Ocular blood flow in unilateral carotid stenosis and hypotension

Ocular blood flow was measured in the juxtapapillary choroid, retrolaminar optic nerve and ciliary body mesoderm using 14C-labelled iodoantipyrine with quantitative autoradiography in seven anesthetized baboons in an experimental model of cerebral and ocular ischemia induced by hemorrhagic hypotension following unilateral common carotid stenosis, with external carotid ligation. The eyes of seven baboons with unilateral common carotid occlusion were also examined histologically for evidence of structural changes. This autoradiographic method allowed measurement of blood flow in different ocular structures and a significant change was noted in the optic nerve of stenosed animals, without structural damage.

Morphologic changes during hypertension

Circulation to the brain is greatly affected by hypertension and by its treatment. Neurologic dysfunction is prominent among the complications of increased arterial pressure and is also most susceptible to preventive antihypertensive therapy. The upward resetting of the limits of autoregulation of cerebral blood flow in hypertension is probably due largely to structural thickening of the walls (hyaline arteriosclerosis) of the resistance vessels. Other consequences of hypertensive vascular lesions in the brain include increased formation of atheroma, lacunae and lacunar infarction, cerebral infarction, multi-infarct dementia and Binswanger's disease. There is also an association between hypertension and hemorrhagic strokes, namely, subarachnoid and intracerebral hemorrhage. Brain lesions are also prominent in malignant hypertension and hypertensive encephalopathy. Antihypertensive treatment, especially if intensive, can result in boundary zone ischemia in the brain if arterial pressure decreases steeply.

Brain damage in fatal non-missile head injury in relation to age and type of injury

Brain damage in a series of 635 fatal non-missile head injuries has been analysed with particular reference to the age of the patient and the type of injury. The differences in the type of brain damage in relation to age were less than we had anticipated, lending further support to the contention that the aged brain has a reduced potential for recovery. The analysis confirms the relationship between road traffic accidents, diffuse axonal injury, gliding contusions and 'basal ganglia' haematomas, and the importance of diffuse brain swelling resulting from a head injury in children.

Fatal head injury in children

A comprehensive neuropathological study was undertaken on 87 children aged between 2 and 15 years with fatal head injuries to identify those features which occurred at the time of head injury (fractured skull, contusions, intracranial haematoma and diffuse axonal injury) and those which were subsequently produced by complicating processes (hypoxic brain damage, raised intracranial pressure, infection and brain swelling). The types of brain brain damage identified were remarkably similar to those seen in adults. The only difference was the prevalence of diffuse brain swelling in children.

Changes in the hippocampus and the cerebellum resulting from hypoxic insults: frequency and distribution

Detailed neurohistological studies were undertaken on 35 cases of cardiac arrest, 17 of hypoglycaemia and 16 of status epilepticus. It was found that the frequency and pattern of selective vulnerability in the hippocampus were similar following cardiac arrest, hypoglycaemia and status epilepticus with the exception that the lateral limb of the dentate fascia was more frequently involved in hypoglycaemia than in the other two groups of cases. Within each group, however, CA1 was the most vulnerable. The cerebellum was less frequently affected in hypoglycaemia and status epilepticus than after cardiac arrest. These findings are compared with recent experimental studies in the rodent which have suggested that the pattern of neuronal damage in each of the three conditions is different.