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  • 2000-2004  (8)
  • 1
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Pseudomonas aeruginosa is a ubiquitous environmental bacterium that is one of the top three causes of opportunistic human infections. A major factor in its prominence as a pathogen is its intrinsic resistance to antibiotics and disinfectants. Here we report the complete sequence of P. ...
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The effects on high-voltage activated (HVA) calcium currents were examined in hippocampal CA1 cells and dentate gyrus (DG) granule neurons, 2 days (short-term; ST) and 2–3 months (long-term; LT) after electrically induced, limbic electrographic and behavioural seizures in rats. Whole-cell voltage-clamp recordings in dissociated CA1 neurons of LT rats showed a decrease in the sustained HVA calcium current amplitude and a faster inactivation of the current both in rats that had experienced a status epilepticus (post-SE rats) and those in which the stimulation did not lead to SE (non-SE rats). In CA1 neurons of LT–SE rats this resulted in a reduced Ca2+ entry through the HVA channels. Perforated-patch voltage-clamp recordings in dissociated DG granule neurons of LT–SE rats showed an increased sustained HVA current amplitude compared to controls and non-SE rats, leading to an increased Ca2+ entry via HVA calcium channels. Two days after SE, we observed an increased Ca2+ entry for a defined depolarization, although the change in HVA current amplitude and inactivation rate did not reach significance. We also observed a decrease in calbindin-D28k staining in DG post-SE neurons, but this change was not associated with a change in HVA current inactivation. The opposite changes in neuronal Ca2+ entry through HVA channels in CA1 vs. DG cells depended strongly on whether rats had experienced SE and later spontaneous seizure activity. These changes are likely to contribute to regionally different effects on local network excitability.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Sodium channels (NaChs) regulate neuronal excitability in both physiological and pathological conditions, including epilepsy and are therefore an important target for antiepileptic drugs. In the present study, we examined the distribution of mRNAs encoding neonatal NaChs II and III α-isoforms in control rat hippocampus and after electrically-induced status epilepticus (SE), using nonradioactive in situ hybridization (ISH). Only weak expression of neonatal NaCh II and III mRNAs was observed in control hippocampus. By contrast, increased expression of neonatal NaCh II and III mRNAs was observed 4 h after the induction of SE in neurons of CA1–CA3 and the dentate granule cell layer. These changes were detected only in rats in which SE was successfully induced and persisted, although less intense, for up to 3 months, when rats display spontaneous seizures. Strong expression of neonatal NaCh α-isoforms was observed 1 week after SE in microglial cells, as confirmed by double labelling, combining ISH with immunocytochemistry for microglia markers. The increased expression of neonatal isoforms of the NaCh in both neurons and microglial cells may represent a critical mechanism for modulation of neuronal excitability, glial function and pharmacological response to antiepileptic drugs in the course of epileptogenesis.
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  • 4
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Neuronal loss, gliosis and axonal sprouting in the hippocampal formation are characteristics of the syndrome of mesial temporal sclerosis (MTS). In the post-status epilepticus (SE) rat model of spontaneous seizures these features of the MTS syndrome can be reproduced. To get a global view of the changes in gene expression in the hippocampus we applied serial analysis of gene expression (SAGE) during the early phase of epileptogenesis (latent period), prior to the onset of the first spontaneous seizure. A total of 10 000 SAGE tags were analyzed per experimental group, resulting in 5053 (SE) and 5918 (control group) unique tags (genes), each representing a specific mRNA transcript. Of these, 92 genes were differentially expressed in the hippocampus of post-SE rats in comparison to controls. These genes appeared to be mainly associated with ribosomal proteins, protein processing, axonal growth and glial proliferation proteins. Verification of two of the differentially expressed genes by in situ hybridization confirmed the changes found by SAGE. Histological analysis of hippocampal sections obtained 8 days after SE showed extensive cell loss, mossy fibre sprouting and gliosis in hippocampal sub regions. This study identifies new high-abundant genes that may play an important role in post-SE epileptogenesis.
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  • 5
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Cystatin C (CSTC), a cysteine protease inhibitor, has been implicated in the processes of neuronal degeneration and repair of the nervous system. Using serial analysis of gene expression (SAGE), we recently identified CSTC as one of the genes that are overexpressed after electrically induced status epilepticus (SE). In the present study, Western blot analysis extended the SAGE results, showing increased CSTC protein in the hippocampus and entorhinal cortex. Immunocytochemistry revealed an increase in CSTC expression in glial cells, which was first apparent 24 h after onset of SE, and persisted for at least 3 months. Double immunolabelling confirmed that both reactive astrocytes, and activated microglia were CSTC immunopositive. Within the hippocampus, up-regulation was also observed in neuronal cells within one day after SE. Up-regulation was still present in hippocampal pyramidal cells and surviving interneurons of chronic epileptic rats (3–8 months post-SE). This study demonstrates that status epilepticus leads to a widespread and persistent up-regulation of CSTC in the hippocampus and entorhinal cortex, which may represent an intrinsic neuroprotective mechanism in the course of epileptogenesis that may counteract progression of the disease.
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  • 6
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: As several epilepsy syndromes are associated with changes in sodium channel subunits we investigated the expression of β1 sodium channel protein in a rat epilepsy model. In this model a chronic epileptic syndrome develops after electrically induced status epilepticus (SE). Many neuropathological characteristics of mesial temporal lobe epilepsy can be reproduced (cell loss, gliosis and synaptic reorganization). In control hippocampus β1 subunit protein was moderately expressed in neurons and weakly expressed in resting astrocytes. β1 sodium channel immunoreactivity increased markedly within 1 week after SE mainly in astrocytes that were colocalized with vimentin (marker for reactive astrocytes). This up-regulation was still present in reactive astrocytes of chronic epileptic rats (〉 3 months after SE). Considering the fact that the β1 subunits may function as cell adhesion molecules interacting with extracellular matrix, the observed increase in reactive astrocytes might subserve a function in cellular and synaptic reorganization during epileptogenesis.
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  • 7
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: In order to reveal axonal rewiring in the hippocampal and parahippocampal regions after status epilepticus, we investigated the temporal evolution of growth-associated protein-43 (GAP-43) mRNA and protein expression in two rat models of mesial temporal lobe epilepsy (MTLE). Status epilepticus (SE) was induced by electrical stimulation of the angular bundle or by intraperitoneal kainic acid (KA) injections. Despite increased GAP-43 mRNA expression in dentate granule cells at 24 h after SE, GAP-43 protein expression in the inner molecular layer (IML) of the dentate gyrus decreased progressively after 24 h after SE in both models. Nevertheless robust mossy fiber sprouting (MFS) was evident in the IML of chronic epileptic rats. Remaining GAP-43 protein expression in the IML in chronic epileptic rats did not correlate with the extent of MFS, but with the number of surviving hilar neurons. In the parahippocampal region, GAP-43 mRNA expression was decreased in layer III of the medial entorhinal area (MEAIII) in parallel with extensive neuronal loss in this layer. There was a tendency of GAP-43 mRNA up-regulation in the presubiculum, a region that projects to MEAIII. With regard to this parahippocampal region, however, changes in GAP-43 mRNA expression were not followed by protein changes. The presence of the presynaptic protein GAP-43 in a neurodegenerated MEAIII indicates that fibers still project to this layer. Whether reorganization of fibers has occurred in this region after SE needs to be investigated with tools other than GAP-43.
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  • 8
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Reactive gliosis is a prominent morphological feature of mesial temporal lobe epilepsy. Because astrocytes express glutamate receptors, we examined changes in metabotropic glutamate receptor (mGluR) 2/3, mGluR5 and transforming growth factor (TGF)-β in glial cells of the hippocampal regions in an experimental rat model of spontaneous seizures. Rats that exhibited behavioural status epilepticus (SE) directly after 1 h of electrical angular bundle stimulation, displayed chronic spontaneous seizures after a latent period of 1–2 weeks as observed using continuous electrographic monitoring. SE resulted in hypertrophy of astrocytes and microglia activation throughout the hippocampus as revealed by immunolabelling studies. A dramatic, seizure intensity-dependent increase in vimentin immunoreactivity (a marker for reactive astrocytes) was revealed in CA3 and hilar regions where prominent neuronal loss occurs. Increased vimentin labelling was first apparent 24 h after onset of SE and persisted up to 3 months. mGluR2/3 and mGluR5 protein expression increased markedly in glial cells of CA3 and hilus by 1 week after SE, and persisted up to 3 months after SE. Double immunolabelling of brain sections with vimentin confirmed co-localization with glial fibrillary acidic protein (GFAP), mGluR2/3 and mGluR5 in reactive astrocytes. TGF-β, a cytokine implicated in mGluR3-mediated neuroprotection, was also upregulated during the first 3 weeks after SE throughout the hippocampus. This study demonstrates seizure-induced upregulation of two mGluR subtypes in reactive astrocytes, which − together with the increased production of TGF-β − may represent a novel mechanism for modulation of glial function and for changes in glial-neuronal communication in the course of epileptogenesis.
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