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  • 1
    ISSN: 1432-0428
    Keywords: Keywords Islet amyloid ; pancreatic beta cells ; Type II (non-insulin-dependent) diabetes mellitus ; peptide precursors ; amylin.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Most non-insulin dependent diabetic patients have amyloid deposits in their pancreatic islets. It is not known whether chronic hyperglycaemia contributes to the formation of amyloid fibrils from the islet amyloid polypeptide that is produced by the pancreatic beta cells. Since islet amyloid exhibits islet amyloid polypeptide precursors immunoreactivity, we examined whether sustained in vitro exposure to raised glucose increases the abundance of these precursors in human beta cells. After 6 days stimulation with 20 mmol/l glucose the cellular content of insulin but not islet amyloid polypeptide was decreased leading to an increase in the ratio of the latter over insulin (3.0 ± 0.6 vs 1.8 ± 0.3 after 6 mmol/l glucose culture, p 〈 0.05). Similar changes occurred in rat beta cells cultured for 3 days in the presence of 20 mmol/1 glucose plus 3-isobutyl-1-methylxanthine. Western blot analysis of cellular islet amyloid polypeptide after prolonged exposure to high glucose indicated the presence of higher proportions of its precursor- and intermediate forms. In human beta cells cultured in 20 mmol/l glucose, the major form corresponds to an intermediate species which exhibits an immunoreactivity for the N-flanking peptide, as is also the case in islet amyloid. We concluded that prolonged in vitro exposure of beta cells to raised glucose concentrations increases the relative proportion of islet amyloid polypeptide over insulin, as well as of its precursors over the mature form of islet amyloid polypeptide. [Diabetologia (1999) 42: 188–194]
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 86 (1999), S. 6940-6944 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A stable GaS passivating layer was deposited on GaAs using α-Ga2S3 powder as a single-source precursor. Both good crystal quality and clean GaS/GaAs interface were achieved. Electron-energy-loss spectra showed that the sulfide material has a band gap of 3.0 eV. The valence band discontinuity of the heterostructure was determined to be 1.9 eV from a series of ultraviolet photoelectron spectra with increasing deposition thickness. Al/GaS/GaAs metal-insulator-semiconductor structures exhibited typical high frequency capacitor versus voltage (C–V) behavior with very small loop hysteresis. The C–V curves showed no aging after 20 months. © 1999 American Institute of Physics.
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  • 3
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 74 (1999), S. 670-672 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Direct measurements of electronic properties have been made for the metal/organic and organic/organic interfaces in a multilayer organic light-emitting diode (LED) using ultraviolet photoemission spectroscopy. The device configuration considered is indium–tin oxide (ITO)/copper phthalocyanine (CuPc)/N,N′-bis-(1-naphyl)-N,N′-diphenyl-1,1′-biphenyl-4,4′-diamne (NPB)/8-hydroxyquinoline aluminum (Alq)/Mg. For the material interfaces considered here, our result indicates that the traditional concept of vacuum-level alignment, though not valid for metal/organic interfaces, still holds at organic/organic interfaces. This implies that little charge transfer occurs at the interfaces due to the small interaction between organic molecules. The largest band offsets are observed between the lowest unoccupied state levels of the organic molecules. Based on the directly measured energy-level alignments, a model is proposed to explain the improved efficiency of multilayer organic LEDs, as compared to those with a single organic layer structure. © 1999 American Institute of Physics.
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  • 4
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A comparative study of the Raman spectra of ZnSe films grown by molecular beam epitaxy on GaAs(100) substrates passivated by NH4)2)Sx and S2Cl2 solutions is presented. Based on the analysis of the line shape of the first-order longitudinal-optical phonon of ZnSe with spatial correlation model of Raman scattering, it is shown that the ZnSe films grown on the GaAs substrates passivated by S2Cl2 solutions have longer coherence lengths, which indicate that their crystalline qualities are better than those passivated by NH4)2Sx solutions. In addition, the barrier heights of ZnSe/GaAs interfaces for different S passivations have been obtained from the ratios of the intensity of the coupled longitudinal-optical phonon-plasmon mode to that of the longitudinal-optical mode of GaAs Raman peak. The results show that the ZnSe/GaAs samples passivated by S2Cl2 solutions have lower density of interfacial states. © 1995 American Institute of Physics.
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  • 5
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 3465-3467 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: ZnS1−xTex(0〈x〈1) alloys grown on (100) GaAs substrates by molecular beam epitaxy are investigated using the x-ray diffraction and Raman scattering. The frequencies of long wavelength ZnTe-like and ZnS-like longitudinal optical phonons determined from Raman scattering show linear variation with the composition x. The frequency of the zone-center optical phonons as a function of x of the ZnS1−xTex mixed crystal shows a typical two-mode behavior, which is in good agreement with the theoretical results from a modified random-element isodisplacement model.© 1997 American Institute of Physics.
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  • 6
    ISSN: 1573-7381
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The cellular response to axonal injury in the superior cervical ganglion was examined by immunofluoresence at intervals from 6 h to 14 days after transection of the internal and external carotid nerves. GAP-43-immunoreactivity (IR) appeared in some neurons in the ganglia 1 day after axotomy, while neurons in control ganglia were GAP-43 negative. In 3 days axotomized ganglia GAP-43-IR structures were increased in number and intensity in nerve fiber bundles, while GAP-43-positive perikarya were restricted to the middle and caudal parts of the ganglia and showed an intensity that was stronger than at 1 day after axotomy. These GAP-43-positive neurons were also galanin positive. In the cranial part of the ganglia, S100-IR in satellite cells was weak at 18 h after axotomy. Peripheral to this area, S100-IR was stronger and co-localized with HSP-72-IR, preferentially located in satellite cells. HSP-72-IR was, however, occasionally observed also in principal neurons at 1 and 3 days after axotomy. In eosin-stained sections, neurons and satellite cells in the cranial part of 1 day axotomized ganglia were reduced in number, and a further loss was noted at 3 days. At 12 h some satellite cells in the cranial part of the ganglia were labelled by the in situ DNA 3'-end labelling method, indicating apoptosis, and at 18 h many cells were labelled. Some neuronal perikarya were also labelled in this region. Labelling was not observed at 1 day or later after axotomy, nor in control ganglia. The results may imply that not only neurons but also satellite cells react to neuronal axonal injury with apoptosis. Neurons in the middle and caudal part of the ganglia survived and showed increased content of GAP-43 and galanin, possibly a sign of regeneration/neuronal plasticity.
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  • 7
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 75 (1999), S. 2731-2733 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A simple, compact, and inexpensive method for shear force distance regulation is presented. A single piezoelectric cantilever is employed to both dither a fiber probe and to detect the decrease in piezotension-induced voltage as it approaches the sample surface. On resonance, the large piezotension-induced voltage (∼0.2 mV/nm) allows for simple electronics to be used. It is expected to find application both in shear force microscopy and for shear force distance regulation in near-field optical microscopy. © 1999 American Institute of Physics.
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  • 8
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report the fabrication of a vacuum-deposited light-emitting device which emits light from its top surface through an Al cathode using p-type doped silicon as the anode material. Enhanced hole injection is clearly demonstrated from the p-Si anode as compared to the indium–tin–oxide (ITO) anode. The mechanisms of hole injection from both the p-Si and ITO anodes into the organic layer are investigated and a possible model based on anode surface band bending is proposed. During the operation of the organic light-emitting device, the surface band bending of the anode plays a very important role in modifying the interfacial barrier height between the anode and the organic layer. © 1999 American Institute of Physics.
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  • 9
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 72 (1998), S. 1593-1595 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The energy level alignment for both Mg/8-hydroxyquinoline aluminum (Alq) and Au/Alq interfaces has been determined by the ultraviolet photoemission measurements. For both interfaces, the difference between the Fermi level and the low-energy edge of the highest occupied molecular orbital (HOMO) is around 1.7 eV. This implies that the Fermi level with respect to the HOMO edge of Alq is independent of the work function of Mg and Au despite a large difference in the metal work function. A Fermi level alignment model is proposed, invoking a charge transfer between the metal and Alq and the formation of a dipolar layer at the metal/Alq interface. © 1998 American Institute of Physics.
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  • 10
    ISSN: 1432-0827
    Keywords: Key words: Osteopenia — Periosteum — Osteocytes — TGF-β2.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Abstract. The effects of tail suspension hypokinesia on the gene expression for TGF-β2 at different sites within bone were evaluated. TGF-β2 mRNA signal levels were determined quantitatively by an image analysis system. The osteopenia induced by tail suspension was verified by histomorphometry. In the periosteum of nonsuspended control rats, TGF-β2 mRNA was highly expressed in the preosteoblasts and osteoblast-rich cambial layers; very little signal was present within the middle and outer fibroblastic layers. Gene expression was significantly reduced in suspended rats, and this was evident both in terms of the number of silver grains in unit area or length of tissue and in each osteoblast and preosteoblast. Hypokinesia also reduced the expression of TGF-β2 mRNA level in cortical and trabecular bone osteocytes, but did not adversely affect the mRNA level in chondrocytes in growth plate. The results affirm the site-specific response of TGF-β2 gene expression in rats, and suggest that the cortical and trabecular bone osteopenia associated with hypokinesia in rats may be associated with a deficit in osteoblastic and osteocytic TGF-β2 level.
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