Gunfer Gurer

Loss of NeuN immunoreactivity after cerebral ischemia does not indicate neuronal cell loss: a cautionary note.

NeuN immunoreactivity is used as a specific marker for neurons. The number of NeuN-positive cells decreases under pathological conditions. This finding is usually considered as an evidence of neuronal loss. However, decrease in NeuN labeling may also be caused by depletion of the protein or loss of its antigenicity. Hence, we have investigated the morphological features of neurons that lost NeuN immunoreactivity and the NeuN protein levels in mouse brain after cerebral ischemia. The number of NeuN-labeled cells was decreased 6 h after a mild ischemic insult (30 min middle cerebral artery occlusion) in penumbral and core regions. Hematoxylin and eosin (H&E) staining of adjacent sections showed that neurons in the penumbra were not disintegrated but displayed early ischemic changes. The nuclear NeuN staining was dramatically reduced or lost in some neurons. However, Hoechst 33258 staining of the same sections revealed that these nuclei were preserved with an intact membrane. Labeling of neurons that had lost NeuN-positivity with antibodies against caspase-3-p20, which is constitutively not present but emerges in neurons after ischemia, disclosed that these neurons still preserved their integrity. Moreover, Western blots showed that NeuN protein levels were not decreased, suggesting that reduced NeuN antigenicity accounted for loss of immunoreactivity in this mild brain injury model. Supporting this idea, NeuN labeling was partially restored after antigenic retrieval. In conclusion, since NeuN immunoreactivity readily decreases after metabolic perturbations, reduced NeuN labeling should not be taken as an indicator of neuronal loss and, quantitative analysis based on NeuN-positivity should be used cautiously after central nervous system (CNS) injury.

Generalised periodic epileptiform discharges: clinical features, neuroradiological evaluation and prognosis in 37 adult patients

Generalised periodic epileptiform discharges (GPEDs) are very rare patterns and are classified as periodic short-interval diffuse discharges (PSIDDs), periodic long-interval diffuse discharges (PLIDDs) and suppression-burst patterns according to the interval between the discharges. In this study we analysed the demographics, history of the seizures during the current illness, mental status, diagnosis, metabolic abnormalities, neuroimaging studies and prognosis of 37 adult patients who had GPEDs in their EEGs. Ages ranged from 17 to 82 years (mean 45 years). There were 19 males and 18 females. The most common aetiology of GPEDs was metabolic and/or infectious disease which was established in 22 patients (59.5%). Other aetiologies included subacute sclerosing panencephalitis (SSPE) in 11 patients (29.7%) and Creutzfeld-Jakob disease (CJD) in 4 patients (10.8%). We showed that structural lesions were found in most of the patients with GPEDs, but concurrent metabolic abnormalities and/or infectious diseases were also detected. Consciousness was impaired and clinical conditions were poor in various degrees in all of the patients when GPEDs were seen. Relatively little is known regarding the mechanism of GPEDs. When GPEDs are seen in EEG, the patient should carefully be checked for metabolic abnormalities and/or infectious diseases and intracranial lesions. GPEDs may be helpful in the determination of prognosis, showing the poor prognosis especially in cases when suppression-burst pattern is seen.

Investigation of HSV-1, HSV-2, CMV, HHV-6 and HHV-8 DNA by real-time PCR in surgical resection materials of epilepsy patients with mesial temporal lobe sclerosis

OBJECTIVE The objective of this study is to investigate the presence of viral DNAs of HSV-1, HSV-2, HHV-6, HHV-8, and CMV in hippocampus of the patients with mesial temporal lobe epilepsy (MTLE) syndrome. METHODS Pathological specimens were obtained from 33 patients with MTLE undergone temporal lobectomy with amygdalo-hippocampectomy due to intractable seizures. Autopsy materials from the hippocampus of 7 patients without neurological disease were used as controls. The data was also correlated with the clinical history of patients including febrile convulsions, age, and history of CNS infections. Real-time polymerase chain reaction method was performed for detection of DNAs of these viruses. RESULTS HHV-6, HSV-1 and HHV-8 were detected in the hippocampus of 3, 2 and 1 patients with MTLE respectively. None of the hippocampus of patients with MTLE was positive for DNA of HSV-2 and/or CMV. Three patients with positive HHV-6 DNAs had febrile convulsions and family history for epilepsy. None of our control specimens showed PCR positivity to any of the 5 tested viruses. CONCLUSIONS Our study is the first to report the presence of HHV-8 viral genome in the brain tissue of patient with MTLE. Viral DNAs were detected in a total of 18% of the patients in this study; we can conclude that activity of the latent virus in patients with hippocampal sclerosis should be more extensively studied to establish its role in active infection.

Astrocytes are More Resistant to Focal Cerebral Ischemia Than Neurons and Die by a Delayed Necrosis

Several recent reports proposed that astrocyte death might precede neuronal demise after focal ischemia, contrary to the conventional view that astrocytes are more resistant to injury than neurons. Interestingly, there are findings supporting each of these opposing views. To clarify these controversies, we assessed astrocyte viability after 2‐h middle cerebral artery occlusion in mice. In contrast to neighboring neurons, astrocytes were alive and contained glycogen across the ischemic area 6 h after reperfusion, and at the expanding outer border of the infarct at later time points. These glycogen‐positive astrocytes had intact plasma membranes. Astrocytes lost plasmalemma integrity much later than neurons: 19 ± 22 (mean ± standard deviation), 58 ± 14 and 69 ± 3% of astrocytes in the perifocal region became permeable to propidium iodide (PI) at 6, 24, 72 h after ischemia, respectively, in contrast to 81 ± 2, 96 ± 3, 97 ± 2% of neurons. Although more astrocytes in the cortical and subcortical core regions were PI‐positive, their numbers were considerably less than those of neurons. Lysosomal rupture (monitored by deoxyribonuclease II immunoreactivity) followed a similar time course. Cytochrome‐c immunohistochemistry showed that astrocytes maintained mitochondrial integrity longer than neurons. EM confirmed that astrocyte ultrastructure including mitochondria and lysosomes disintegrated much later than that of neurons. We also found that astrocytes died by a delayed necrosis without significantly activating apoptotic mechanisms although they rapidly swelled at the onset of ischemia.

Lysosomal rupture, necroapoptotic interactions and potential crosstalk between cysteine proteases in neurons shortly after focal ischemia.

Ischemic cell death is a complex process and the initial distinction between apoptosis and necrosis appears to be an oversimplification. We previously reported that in ischemic neurons with disrupted plasmalemma, apoptotic mechanisms were also active. In the present study, we investigated cellular co-localization of another necrotic feature, lysosomal rupture, with apoptotic mechanisms in the mouse brain and assessed the potential interactions between cysteine proteases. The lysosomal enzymes were spilled into the cytoplasm 1-4h after ischemia/reperfusion, suggesting that lysosomal membrane integrity was rapidly lost, as occurs in necrosis. The same neurons also exhibited caspase-3 and Bid cleavage, and cytochrome-c release. Caspase-3 activity preceded cathepsin-B leakage in most neurons, and declined by 12h, while lysosomal leakage continued to increase. Concurrent inhibition of cathepsin-B and caspase-3 provided significantly better neuroprotection than obtained with separate use of each inhibitor. These data suggest that necrotic and apoptotic mechanisms may act both in concert as well as independently within the same cell beginning at the onset of ischemia to ensure the demise of damaged neurons. Therefore, combined inhibition of cysteine proteases may abrogate potential shifts between alternative death pathways and improve the success of stroke treatments.

Thrombotic distal middle cerebral artery occlusion produced by topical FeCl3 application: a novel model suitable for intravital microscopy and thrombolysis studies

Intravital or multiphoton microscopy and laser-speckle imaging have become popular because they allow live monitoring of several processes during cerebral ischemia. Available rodent models have limitations for these experiments; e.g., filament occlusion of the proximal middle cerebral artery (MCA) is difficult to perform under a microscope, whereas distal occlusion methods may damage the MCA and the peri-arterial cortex. We found that placement of a 10% FeCl3-soaked filter paper strip (0.3 × 1 mm2) on the duramater over the trunk of the distal MCA through a cranial window for 3 minutes induced intraarterial thrombus without damaging the peri-arterial cortex in the mouse. This caused a rapid regional cerebral blood flow decrease within 10 minutes and total occlusion of the MCA segment under the filter paper in 17 ± 2 minutes, which resulted in a typical cortical infarct of 27 ±4 mm3 at 24 hours and moderate sensorimotor deficits. There was no significant hemispheric swelling or hemorrhage or mortality at 24 hours. Reperfusion was obtained in half of the mice with tissue plasminogen activator, which allowed live monitoring of clot lysis along with restoration of tissue perfusion and MCA flow. In conclusion, this relatively simple and noninvasive stroke model is easy to perform under a microscope, making it suitable for live imaging and thrombolysis studies.

Expression of matrix metalloproteinases in vasculitic neuropathy

The aim of this study was to investigate the expression pattern and cellular source of matrix metalloproteinases (MMP) in vasculitic neuropathy. Matrix metalloproteinases are endopeptidases degrading components of extracellular matrix proteins, and they have been implicated in the pathogenesis of inflammatory demyelination. They are induced by cytokines, secreted by inflammatory cells, and enhance T cell migration. Vasculitic neuropathy occurs as a component of systemic vasculitis or as an isolated angiitis of the peripheral nervous system, and T cell-mediated inflammation is detected in its pathogenesis. Nerve biopsy sections of eight patients with nonsystemic vasculitic neuropathy (NSVN) and four with systemic vasculitic neuropathy were examined for the presence of CD4+, CD8+, and CD68+ cells and immunohistochemically for MMP-2 and MMP-9 expression. Nerve biopsies of eight patients with noninflammatory neuropathy were used as a control group. Semiquantitative polymerase chain reaction analysis was performed to detect MMP-2 and MMP-9 mRNA. The predominant cells were CD8+ and CD68+ T cells. Expression of MMP-9, but not MMP-2, was increased in perivascular inflammatory infiltrate in nerve tissues of vasculitic neuropathy patients. This MMP-9 expression correlated positively with immunostaining of CD8+ T cells. No difference was detected between immunostaining patterns of nonsystemic and systemic vasculitic neuropathies with the antibodies used, except in MMP-9 immunostaining, which was found to be enhanced in NSVN group. Polymerase chain reaction analysis revealed elevated mRNA levels of MMP-9 and MMP-2 compared with controls, but this did not reach statistical significance. Our results imply a pathogenic role for MMP-9 secreted from CD8+ cells in vasculitic neuropathy.

Epilepsia partialis continua: clinical and electrophysiological features of adult patients.

In this study we reviewed the clinical, electrophysiological and neuroimaging data of 21 patients with epilepsia partialis continua (EPC), which is a rare form of epilepsy with focal motor seizures persisting hours to years. We found infections, cerebrovascular events and tumors as the most common causes of EPC in adults. SSPE was also shown as a cause of EPC. EPC in SSPE patients was resistant to therapies and persisted more than 1 year. EPC is usually a predictor of poor outcome and 29% of patients died after EPC in this study. As prognosis is usually bad and as response to treatment is poor in patients who had EPC, early diagnosis and treatment of the underlying cause is important. Although the most common etiologies are infections, cerebrovasculer events and tumors, if EPC persists several months SSPE should be kept in mind as a rare cause of EPC. MRI should be repeated in chronic cases to show dysplastic cortex, which was shown in 1 patient in this study.

Alpha-synuclein aggregation induced by brief ischemia negatively impacts neuronal survival in vivo: a study in [A30P]alpha-synuclein transgenic mouse.

Alpha-synuclein oligomerization and aggregation are considered to have a role in the pathogenesis of neurodegenerative diseases. However, despite numerous in vitro studies, the impact of aggregates in the intact brain is unclear. In vitro, oxidative/nitrative stress and acidity induce α-synuclein oligomerization. These conditions favoring α-synuclein fibrillization are present in the ischemic brain, which may serve as an in vivo model to study α-synuclein aggregation. In this study, we show that 30-minute proximal middle cerebral artery (MCA) occlusion and 72 hours reperfusion induce oligomerization of wild-type α-synuclein in the ischemic mouse brain. The nonamyloidogenic isoform β-synuclein did not form oligomers. Alpha-synuclein aggregates were confined to neurons and colocalized with ubiquitin immunoreactivity. We also found that 30 minutes proximal MCA occlusion and 24 hours reperfusion induced larger infarcts in C57BL/6(Thy1)-h[A30P]alphaSYN transgenic mice, which have an increased tendency to form synuclein fibrils. Trangenics also developed more selective neuronal necrosis when subjected to 20 minutes distal MCA occlusion and 72 hours reperfusion. Enhanced 3-nitrotyrosine immunoreactivity in transgenic mice suggests that oxidative/nitrative stress may be one of the mechanisms mediating aggregate toxicity. Thus, the increased vulnerability of transgenic mice to ischemia suggests that α-synuclein aggregates not only form during ischemia but also negatively impact neuronal survival, supporting the idea that α-synuclein misfolding may be neurotoxic.

Involvement of the central nervous system in Miller Fisher syndrome: a case report

Miller Fisher syndrome (MFS) is characterised by ophthalmoplegia, ataxia and areflexia. Reports on cerebellar ataxia and supranuclear oculomotor derangement in MFS suggested an additional involvement of the central nervous system (CNS), resembling Bickerstaffs brainstem encephalitis (BBE). In the present report, a patient with a monophasic acute illness, early recovery and specific clinical-laboratory findings suggested both intrinsic brainstem and peripheral nerve disease (MFS and BBE). In pons and medulla oblangata, blurred to discrete T2-lesions were revealed by cranial MRI, while involvement of peripheral nerves was detected with EMG. The CSF showed no increase in protein or cell content, such as occurs in brainstem encephalitis.