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  • 1
    Electronic Resource
    Electronic Resource
    Scanning electron microscopical study of the neurofibrillary tangles of Alzheimer’s disease (1997)
    Springer
    Acta neuropathologica 94 (1997), S. 78-86 
    Details
    ISSN: 1432-0533
    Keywords: Key words Paired helical filament ; Neurofibrillary ; tangles ; Scanning electron microscopy ; Alzheimer’s ; disease
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Neurofibrillary tangles (NFTs) have been ultrastructually studied by various methods, leading to several three-dimensional models of paired helical filaments (PHFs). In this study, we present the scanning electron microscopic findings of NFTs in an autopsy case of Alzheimer’s disease and clarify the three-dimensional structures of NFTs. NFTs were clearly defined in freeze-cracked nerve cells and consisted of two types of filamentous structures, straight and helical filaments. Straight filaments measured from 20 to 25 nm in diameter and had a smooth surface. They were slightly bent but mostly straight with no constrictions. One type of straight filaments ran in a bundle in the same direction, another was intertwined to each other. Most of the helical profiles of filaments usually measured about 28 nm in diameter, with a distance of 100 nm between periodic constrictions. They seemed to consist of a pair of isodiametric filaments of 10 nm in diameter. In addition, two unusual types of helical filaments were occasionally observed. One comprised thick filaments of about 38 nm in diameter, with a distance of 100 nm between constrictions; these helical filaments appeared to consist of two or more strands. The other comprised thin helical filaments of about 20 nm in diameter and regularly constricted at an interval of 50 nm. All types of the helical filaments examined in this case were leotropic. This result supports a protofilament model of PHFs. Scanning electron microscopy using the freeze-cracked and maceration method is a useful and simple method for three-dimensional observation of the filamentous structures in NFTs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004010050675
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  • 2
    Electronic Resource
    Electronic Resource
    Scanning electron microscopical study of neurofibrillary tangles in a presenile patient with Down’s syndrome (1998)
    Springer
    Acta neuropathologica 96 (1998), S. 179-184 
    Details
    ISSN: 1432-0533
    Keywords: Key words Paired helical filaments ; Neurofibrillary ; tangles ; Down’s syndrome ; Alzheimer’s disease ; Scanning electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract An autopsy case of a 64-year old woman with Down’s syndrome (DS) is reported with a special reference to the ultrastructure of neurofibrillary tangles (NFTs). NFTs and senile plaques were diffusely observed throughout the brain. The most severe changes were seen in the amygdaloid nuclear complex and hippocampus. Immunohistochemistry of the NFTs and senile plaques indicated the features identical to those in Alzheimer’s disease (AD). Ultrastructurally, NFTs were composed of straight filaments and two profiles of paired helical filaments (PHFs). By transmission electron microscopy, straight filaments measured 25–28 nm in diameter. As to the PHFs, one type was 33 nm in maximum diameter and constricted at a 75– to 80-nm interval. The other was 16–18 nm in maximum diameter and constricted at a 35– to 40-nm interval. By scanning electron microscopy, the diameter of the straight filaments measured up to 28–30 nm. Two profiles of PHFs were observed. One type of PHF showed thick filaments about 34 nm in maximum diameter and constrictions at an 80-nm interval. The other was about 17 nm in diameter and constricted at a 40-nm interval. The helical directions of both PHFs were left-handed. The frequency of PHFs with short interval was much higher in DS than AD. Furthermore, the length of the periodicity of this type of PHF was somewhat less than that of AD. Thus, these findings suggest that the neuropathological changes in DS and AD share a common etiopathology, but that some differences in the PHFs between DS and AD may reflect on molecular difference in the proteins or peptides associated with PHF formation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004010050879
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  • 3
    Electronic Resource
    Electronic Resource
    Defect study of proton-irradiated liquid-encapsulated Czochralski GaAs using the positron-annihilation technique (1995)
    Springer
    Applied physics 60 (1995), S. 57-60 
    Details
    ISSN: 1432-0630
    Keywords: 78.70.Bj ; 72.80.Ey
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The positron lifetime of undoped Liquid-Encapsulated Czochralski (LEC)-GaAs and Si-doped (1.3×1018 cm−3) LEC-GaAs was measured before and after irradiation with protons (dose 1×1015/cm2, 15 MeV). In Si-doped GaAs, the decrease of positron lifetime at temperatures between 10 and 300 K are due to the decrease of the positron-diffusion length and the increase of the effective shallow traps such as antisite GaAs. The annealing stage of the proton-irradiation-induced defects which show the different behavior from that of electron-irradiation-induced defects suggests that proton irradiation creates more complicated defect complexes, containing vacancies rather than isolated vacancy-type defects or simple complexes which have been observed during electron-irradiation processes. Above 700 K, proton-irradiation-induced defects such as vacancy-type defects and simple vacancy complexes are almost annealed out, while Si-induced defects such as SiGa-VGa complexes cannot be annealed out above 973 K.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01577613
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  • 4
    Electronic Resource
    Electronic Resource
    Defect study on electron irradiated GaAs by means of positron annihilation (1994)
    Springer
    Applied physics 58 (1994), S. 59-62 
    Details
    ISSN: 1432-0630
    Keywords: 78.70.Bj ; 72.80.Ey
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Measurements of the positron lifetime and Doppler-broadened annihilation-radiation have been performed in electron-irradiated GaAs. The positron lifetime at the irradiation induced defects was ∼0.250 ns at 300 K. The defect clustering stage was found to occur at around 520–620 K, and the coarsening and annealing stage is believed to be above 620 K. Similar annealing stages were also observed in GaAs lightly doped with Si (0.2×1018 cm−3). Both the lifetime and the S-parameter in the irradiated GaAs were found to decrease with temperature from 300 K to 100 K, suggesting the coexistence of shallow traps in electron irradiated GaAs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00331517
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    Paper (German National Licenses)
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