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June 1, 2005
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June 1, 2005
Abstract
Creutzfeldt-Jakob disease and bovine spongiform encephalopathy are the best known forms of prion diseases. A basis for their pathogenesis is the transformation of normal prion protein to abnormal prion protein. This would mean that either loss of normal function or a gain of a toxic function of the prion protein would play a major role. Since the prime target for Creutzfeldt-Jakob disease in humans is the neocortex, and the intracort ical distribution of the destructive process in prion diseases appears not to be haphazard, it may be that a clear cortical study of normal prion protein production in the premorbid human neocortex might contribute to insight in the pathogenesis of prion diseases. As no such study is available, we performed a detailed study in normal human cortex using immunohistochemistry for prion protein, in both frozen and vibratomised tissue, and in situ hybridisation for prion protein mRNA. We have found normal prion protein production mainly in the upper cortical neurons in neocortex and Purkinje cells in the cerebellum. This finding implicates that normal prion protein is more important as an anti-apoptotic signal in disease than abnormal prion protein is as a toxic substance.
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June 1, 2005
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Apoptotic cell death is a fundamental and highly regulated biological process in which a cell is instructed to participate actively in its own demise. This process of cellular suicide is activated by developmental and environmental cues and normally plays an essential role in eliminating superfluous, damaged, and senescent cells of many tissue types. In recent years, a number of experimental studies have provided evidence of widespread neuronal and glial apoptosis following injury to the central nervous system (CNS). These studies indicate that injury-induced apoptosis can be detected from hours to days following injury and may contribute to neurological dysfunction. Given these findings, understanding the biochemical signaling events controlling apoptosis is a first step towards developing therapeutic agents which would target this cell death process. This review will focus on the molecular cell death pathways responsible for generating the apoptotic phenotype, summarize what is currently known about apoptotic signals activated in the injured CNS, and what potential strategies might be pursued to reduce this cell death process as a means to promote functional recovery.
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June 1, 2005
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Parkinson's disease is the most common movement disorder and the second most common neurodegenerative disease. Neuropathologically, it is characterized by the degeneration of nerve cells that develop filamentous inclusions in the form of Lewy bodies and Lewy neurites. Recent work has shown that rare, familial forms of Parkinson's disease are caused by missense mutations in the α-synuclein gene and that the filamentous lesions of Parkinson's disease are made of α-synuclein. The same is true of the Lewy body pathology that is associated with other neurodegenerative diseases, such as dementia with Lewy bodies. The filamentous inclusions of multiple system atrophy have also been found to be made of α-synuclein, thus providing an unexpected molecular link with Lewy body diseases. Recombinant α-synuclein assembles into filaments with similar morphologies to those found in the human diseases and with a cross-β diffraction pattern characteristic of amyloid. The related proteins β-synuclein and γ-synuclein are poor at assembling into filaments. They are not present in the pathological filamentous lesions and have not been found to be linked to genetic disease. The new work has established the α-synucleinopathies as a major class of neurodegenerative disease.
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June 1, 2005
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Chronic glial activation possibly plays a role in chronic neurodegeneration in Alzheimer's disease (AD). It has been shown that amyloid peptide is capable of activating microglial cells in vitro . The aim of this study was to further characterize the structural preconditions for amyloid peptide in order to activate glial cells and to investigate whether this peptide is also able to induce glial activation in the living brain. We observed that amyloid peptide induced strong cellular activation in primary microglial cell culture as detected by the release of stable metabolites of nitric oxide (NO), when the peptide was fibrillar. For this activation, co-stimulation with interferon-γ was a precondition. Using microdialysis of the living brain in a rat we observed pronounced NO generation when fibrillar amyloid peptide was stereotaxically injected. Non-fibrillar amyloid peptide did not induce such a glial reaction. No administration of interferon-γ or any other co-stimulatory factor was necessary in vivo . Thus, we show that fibrillar, but not non-fibrillar amyloid peptide induced glial activation also in vivo . In the case of the living brain, the presence of deposits of fibrillar amyloid peptide could maintain a chronic microglial activation, ultimately leading to the progressive neurodegeneration associated with Alzheimer's disease.
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June 1, 2005
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β-Amyloid (βA) is cytotoxic to neurons in culture by increasing hydrogen peroxide and altering calcium homeostasis. We have evaluated βA-induced cytotoxicity, peroxide generation and glutamate (Glu) uptake in cultured astrocytes. Twenty-four hours after a single addition of either βA 25–35 or βA 1–40 there was a concentration-dependentdecrease in viability. Catalase or vitamin E showed no protective effect against βA 25–35 . Dithiothreitol (DTT), N-acetylcysteine (NAC) and cyclosporine A significantly prevented the toxic effects of both βA 25–35 and peroxide, while inhibition of peroxide detoxifying enzymes enhanced toxicity. Exposure to βA 25–35 or βA 1–40 increased peroxides at 2 h and 24 h, which was prevented by DTT and NAC, but not vitamin E. βA 25–35 inhibited Glu uptake in astrocytes and neurons in culture. Following exposure of neurons to βA for 24 h there was decreased uptake and increased Glu levels in the culture medium, that resulted in gradual excitotoxicity.
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June 1, 2005
Abstract
The S-100B protein is released by injured astrocytes. After passage through a disintegrated blood-brain barrier (BBB) the molecule can be detected in the peripheral circulation. We investigated the association between the extent of brain injury and S-100B concentration in serum in cerebral injury caused by cerebral ischemia and cerebral fungal infection. Study I: The S-100B serum concentration was serially determined in 24 patients with ischemic stroke at 4, 8, 10, 24, 72 hours after the onset of symptoms. We observed that patients with brain lesions larger than 5 cm 3 exhibited significantly increased serum levels of S-100B at 10, 24 and 72 hours compared to those with lesion volumes below 5 cm 3 . Furthermore, an association between S-100B serum concentration and neurological outcome was observed. Study II: In a mouse model of systemic fungal infection with Candida albicans we observed that serum levels of S-100B increased at day 1 after intravenous infection. At this time we could histologically demonstrate brain tissue injury by invading hyphae which had crossed the BBB. Furthermore, reactive astrogliosis was demonstrated by immunohistochemistry. On day 7 we found a significant decrease of S-100B serum level compared to day 1 and 4. This was associated with a demarcation of the fungi with leukocytes in brain tissue at this late phase of infection. No further invasion through the BBB was seen on day 7. In conclusion, serum levels of S-100B reflect the time course of tissue injury in cerebral ischemia and cerebral infection to a similar extent. Thus, S-100B may be a useful marker to assess cerebral tissue injury.
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June 1, 2005
Abstract
The compilation of cerebrospinal fluid (CSF) patient data together with a graphic display of immunoglobulin patterns in a single CSF report has two main advantages: analytical and clinical plausibility control of a complex set of data improves quality assessment and allows improved clinical specificity and sensitivity for recognition of disease-related “typical” data patterns. The widespread use of automated on-line evaluation programs can now be combined with knowledge-based programs for interpretation by clinical chemists and neurologists. These programs are based on knowledge of neuroimmunology, blood-CSF barrier function and dysfunction, influence of CSF flow on concentrations of blood-derived and brain-derived proteins in CSF, specific intrathecal antibody synthesis and relevance of brain proteins for differential diagnosis of degenerative diseases. The relevance of hyperbolic discrimination functions in quotient diagrams for the detection of intrathecal immunoglobulin synthesis is compared with earlier, still frequently used, linear interpretation functions. Differences found in commercially available interpretation software are discussed.
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June 1, 2005
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In normal conditions, albumin and immunoglobulin (Ig)G in the cerebrospinal fluid (CSF) originate from the blood, and there is no antibody production within the central nervous system. Up to 20% of CSF proteins are intrathecally synthesized, but the major fraction is blood-derived. The CSF/serum albumin quotient (Q Alb ) is the best marker of the blood-CSF barrier function. The corresponding immunoglobulin quotients (Q IGG , Q IGA , Q IGM ) are not linearly related to Q Alb and their correlations are defined by an hyperbolic equation. This equation is used to discriminate between a blood-derived and a locally produced fraction of immunoglobulins in case of an intrathecal humoral immune response. The detection of CSF-specific oligoclonal IgG is more sensitive than the quantitative comparison between Q IGG and Q Alb . A further step is the determination of antibody indices and the detection of specific oligoclonal antibodies by antigen-driven immunoblots. CSF analysis remains a cornerstone for the diagnosis of various neurological disorders, including multiple sclerosis and infectious diseases of the central nervous system.
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June 1, 2005
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Endothelin-1 is the most potent vasoconstrictor known to date. This peptide is believed to play a pathophysiological role in the development of vasospasm, the most important complication of subarachnoid hemorrhage (SAH). In the present study we investigated the release of endothelin-1 in SAH and analyzed the cellular source of this peptide. At a protein and mRNA level we were able to show that endothelin-1 is produced by mononuclear leukocytes. Complementary in vitro studies revealed that aging and subsequent hemolysis of blood is sufficient to induce production of endothelin-1 by mononuclear leukocytes. Thus, cerebrospinal fluid-derived mononuclear leukocytes are a source of endothelin-1 in patients suffering from SAH. This finding may have important therapeutic implications as anti-leukocyte strategies could prevent cerebrovascular complications in SAH patients.
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June 1, 2005
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Although controversial, data on the genetic polymorphism of apoprotein E ( APOE ), methylenetetrahydrofolate ( MTHFR ) and paraoxonase ( PON1 ) genes implicate their role in the development of cerebrovascular disease. The aim of this study was to assess the association of polymorphism of APOE , MTHFR and PON1 genes in 56 stroke and 36 carotid stenosis patients, and in 124 control subjects by PCR-restriction fragment length polymorphism analysis. In the stroke group a significantly different MTHFR genotype distribution (p=0.004, odds ratio for T/T of 17.571), but no significant difference in APOE and PON1 allele and genotype distribution compared to the control was found. The carotid stenosis group exhibited a significantly different APOE allele and genotype distribution (p=0.023, odds ratio APOE∊3∊4 of 4.24), but no significant difference in the MTHFR and PON1 allele and genotype distribution from the control group. The preliminary results obtained in this study revealed an association of the MTHFR and APOE gene polymorphism with cerebrovascular disease, suggesting a significant risk for stroke in subjects who are homozygous for the T allele and for carotid stenosis in subjects having APOE∊3∊4 genotype. Additional studies in larger patient groups are needed to confirm these observations.
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June 1, 2005
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Over the past 15 years neurotrophic factors have generated considerable excitement for their potential as therapy for a wide variety of degenerative neurological disorders, for which there is currently no treatment. The first part of this period was marked by the discovery, characterization, and cloning of many new growth factors, and by successful testing of these factors in animal models of neurological disease. In recent years the biotechnology industry and pharmaceutical industry have attempted to replicate the success of the animal studies in clinical trials. Although some studies have demonstrated moderate efficacy, for the most part the clinical trials have been less successful at demonstrating the therapeutic efficacy of this new class of drugs. For example, nerve growth factor appeared to be efficacious in two phase II clinical trials for peripheral neuropathy, but failed in a large scale phase III trial. Ciliary neurotrophic factor, brain derived neurotrophic factor and insulin like growth factor-1 have all been tested in clinical trials for the treatment of amyotrophic lateral sclerosis, with at best, variable indications of efficacy. Nevertheless, there are still many reasons to be optimistic that some of these agents may be useful clinically. Many technical and pharmacological issues remain to be adequately addressed, before neurotrophic factors can live up to their potential. Our collective experience with them has re-adjusted previously wild expectations, so that they are now much more realistic. This is necessary and beneficial for the maturation of this field of study.
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June 1, 2005
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Transplanted human fetal dopamine neurons can reinnervate the striatum in patients with Parkinson's disease (PD). Recent findings using positron emission tomography indicate that the grafts are functionally integrated and restore dopamine release in the patient's striatum. The grafts can exhibit long-term survival without immunological rejection and despite an ongoing disease process and continuous antiparkinsonian drug treatment. In the most successful cases, patients have been able to withdraw L-dopa treatment after transplantation and resume an independent life. About two-thirds of grafted patients have shown clinically useful, partial recovery of motor function. The major obstacle for the further development of this cell replacement strategy is that large amounts of human fetal mesencephalic tissue are needed for therapeutic effects. Stem cells hold promise as a virtually unlimited source of self-renewing progenitors for transplantation. The possibility to generate dopamine neurons from such cells is now being explored using different approaches. However, so far the generated neurons have survived poorly after transplantation in animals.
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June 1, 2005
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Mediators of extracellular matrix proteins degradation, the matrix metalloproteinases (MMPs), involved in inflammation as well as facilitation of process outgrowth of oligodendrocytes are interesting targets for neural repair. Recent data reported their activation after seizures, cerebral ischemia and spinal cord injury. The present study was designed to localize at cellular level the gelatinase activity by in situ zymography in a rat spinal cord contusion model. The kinetic of gelatinase activation was monitored by in situ zymography on 20 μm cryostat sections. The fluorescein-quenched DQ gelatin digestion yielded cleaved fluorescent peptides enabling the detection of gelatinase activity at cellular level. Twenty four hours and 48 h after injury, a strong gelatinase activity was detected at the lesion site in and around vascular structures and infiltrated cells. A preincubation with either MMP-2 or MMP-9 antibodies significantly decreases the gelatinase activity pattern, suggesting the involvement of at least both MMPs. Our results are consistent with a role for MMPs in the blood spinal barrier disruption, the leukocytes infiltration, the disruption of the extracellular matrix and the clearance of debris.
