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  • 1995-1999  (5)
  • 1975-1979
  • 1999  (2)
  • 1996  (3)
Materialart
Erscheinungszeitraum
  • 1995-1999  (5)
  • 1975-1979
Jahr
  • 1
    Digitale Medien
    Digitale Medien
    Oxford, UK : Blackwell Science Ltd
    European journal of neuroscience 11 (1999), S. 0 
    ISSN: 1460-9568
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Human temporal lobe epilepsy is characterized by strong synaptic reorganization that leads to abnormal recurrent excitatory synaptic connections among hippocampal neurons. In addition, electrophysiological studies show that synaptic activity of the main afferent input to the hippocampus, the perforant path, is prolonged and amplified by changes in postsynaptic glutamate receptors. The current view is that these morphological and physiological abnormalities contribute significantly to the hyperexcitability seen in the hippocampus of temporal lobe epilepsy. Recently, it was found that presynaptic inhibitory metabotropic glutamate receptors are an important negative feedback mechanism that controls synaptic release of glutamate in the hippocampus. In this study, we assessed the functionality of this feedback system by investigating the metabotropic glutamate receptor mediated depression of excitatory synaptic transmission in surgically removed hippocampi from patients with marked synaptic reorganization (Ammon's horn sclerosis group) and from patients without detectable reorganization (lesion group). We report here that this control of synaptic transmission is lost in hippocampi from the Ammon's horn sclerosis group whereas this control is preserved in hippocampi from the lesion group. The data presented here suggest that the loss of feedback inhibition mediated by metabotropic glutamate receptors could be a further, previously not recognized, mechanism in the pathophysiology of temporal lobe epilepsy.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Archives of environmental contamination and toxicology 30 (1996), S. 373-378 
    ISSN: 1432-0703
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Energietechnik , Medizin
    Notizen: Abstract. The 96-h toxicity of four organophosphates (thiometon, disulfoton, malathion, and demeton-S-methyl, the oxygen analogue of thiometon) in the freshwater bivalve mollusc Dreissena polymorpha was tested using different nominal concentrations ranging between 6 and 50 mg/L. No mortalities were observed in mussels exposed to malathion and demeton-S-methyl (26 mg/L and 6 mg/L, respectively), and at the lowest concentrations of thiometon and disulfoton (6 and 10 mg/L, respectively). At higher thiometon and disulfoton concentrations, mortalities occurred. At the highest concentrations of 50 mg thiometon/L and 30 mg disulfoton/L, mussel mortalities of 88 and 93%, respectively, were determined. Organophosphate concentrations of up to a factor 10 times higher than in the ambient water were found in exposed mussels, irrespective of whether they were alive or dead. The search for organophosphate metabolites via GC/MS analysis of mussel tissue extracts was negative, suggesting lacking or low oxidative activation of the insecticides used. The mollusc is highly resistant to toxic effects of organophosphate insecticides and their biological active oxygen analogues.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 3
    Digitale Medien
    Digitale Medien
    Springer
    Archives of environmental contamination and toxicology 30 (1996), S. 373-378 
    ISSN: 1432-0703
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Energietechnik , Medizin
    Notizen: Abstract The 96-h toxicity of four organophosphates (thiometon, disulfoton, malathion, and demeton-S-methyl, the oxygen analogue of thiometon) in the freshwater bivalve mollusc Dreissena polymorpha was tested using different nominal concentrations ranging between 6 and 50 mg/L. No mortalities were observed in mussels exposed to malathion and demeton-S-methyl (26 mg/L and 6 mg/L, respectively), and at the lowest concentrations of thiometon and disulfoton (6 and 10 mg/L, respectively). At higher thiometon and disulfoton concentrations, mortalities occurred. At the highest concentrations of 50 mg thiometon/L and 30 mg disulfoton/L, mussel mortalities of 88 and 93%, respectively, were determined. Organophosphate concentrations of up to a factor 10 times higher than in the ambient water were found in exposed mussels, irrespective of whether they were alive or dead. The search for organophosphate metabolites via GC/MS analysis of mussel tissue extracts was negative, suggesting lacking or low oxidative activation of the insecticides used. The mollusc is highly resistant to toxic effects of organophosphate insecticides and their biological active oxygen analogues.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 4
    Digitale Medien
    Digitale Medien
    Springer
    Fresenius' journal of analytical chemistry 365 (1999), S. 255-257 
    ISSN: 1432-1130
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Reinforcement effects in composites are widely influenced by fibre coatings. A detailed understanding of their microstructure and chemical composition is of great interest. Boron nitride films were deposited continuously on fibre rovings of various ceramics in CVD reactors of vertical as well as horizontal position. XPS depth profilings show that the film compositions are close to stoichiometric BN with carbon and oxygen impurities in the range of 10 at%. Cross-sections of separated fibres were investigated by HREM and TEM diffraction. All BN films are hexagonal turbostratic. The (002) layers with an increased distance (about 0.36 nm) showed a mean stacking sequence near to graphite and a characteristic orientation to the fibre in the interface region. We assume the gas flow type and hence the exchange rate of matter and energy determines the film structure in this region. With increasing film thickness the (002) layers fold randomly in all directions or form nanocrystals at elevated temperatures.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 5
    Digitale Medien
    Digitale Medien
    Springer
    Journal of materials science 31 (1996), S. 5979-5984 
    ISSN: 1573-4803
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract Carbon fibres were coated with layers of silicon carbide (SiC) and boron nitride (BN) by conventional chemical vapour deposition. The SiC films were deposited by thermal decomposition of methyltrichlorosilane, whereas the BN films were deposited using the stepwise disproportion reaction of boron chloride with ammonia. Samples for electron microscopic investigations were prepared by separating film from fibre or by conventional mechanical thinning and subsequent ion milling of cross sections of coated fibres. Bright- and dark-field images of both planar and cross-sectional electron microscopic investigations on the fibre coatings gave detailed information on film thickness and morphology. High-resolution images improved the structural information of electron diffraction patterns. Crystal dimensions in the SiC film vary between 10 and 40 nm. Electron diffraction revealed the crystal structure to be a mixture of disordered hexagonal 2H-SiC and cubic β-SiC. High-resolution images showed the (1 1 1)-planes to be preferred for deposition. In BN films, a hexagonal turbostratic structure similar to turbostratic carbon was observed. Apart from amorphous regions, nanocrystalline parts were detected, which have a higher structural perfection in the stacking sequence of their (0 0 2)-planes compared to the (0 0 2)-planes of the turbostratic carbon fibre. High-resolution images located the film-fibre interface that was confirmed by electron energy loss spectroscopy.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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