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  • 79.90  (1)
  • Calcitonin mRNA  (1)
  • Chemoreception  (1)
  • 1
    ISSN: 1432-0630
    Schlagwort(e): 78.70.Bj ; 79.90 ; 72.20.Ht
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract Positron lifetime spectroscopy measurements have been carried out for semi-insulating GaAs with applied electric fields in the samples directed towards, and away from the positron injecting contact. The lifetime spectra have been decomposed into two components, the longer of which (≈400 ps) is characteristic of open volume defects at the metal-semiconductor interface through which positrons are injected. The interesting feature of these experiments is the large increase in the intensity of this interface component as the field is directed towards the contact. We show that this increase is caused by a significant fraction of implanted positrons drifting under the influence of a strong electric field produced by a layer of space-charge formed adjacent to the positron injecting contact. The general trend of the intensity variation is well explained by the proposed model. Experiments involving the application of an ac bias to the samples strengthen the suggestion that the space charge region is largely formed from ionized EL2 donors. The results of the present work indicate that semi-insulating GaAs possesses properties that make it a suitable material for the fabrication of a high efficiency (≈10%) room-temperature field-assisted positron moderator. The extraction of positrons from the GaAs substrate into the vacuum through a thin metalization is discussed based upon available positron affinities for the GaAs and various elemental metals. These data suggest that a few monolayers of a strongly electronegative metal such as Au or Pd may allow vacuum emission through quantum tunneling.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 276 (1994), S. 399-402 
    ISSN: 1432-0878
    Schlagwort(e): Carotid body ; Calcitonin ; Calcitonin mRNA ; Gene expression ; Oligonucleotide probe ; In situ hybridization ; Human ; Monkey, Macaca fascicularis (Primates)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract Calcitonin mRNA was detected in human and monkey carotid bodies by in situ hybridization histochemistry, using a 35S-labeled oligonucleotide probe for human calcitonin. In both human and monkey carotid body, moderate to high hybridization signal for calcitonin mRNA was observed in all cases. The hybridization signal in the formalin-fixed, paraffin-embedded samples was comparable to that obtained from frozen paraformaldehyde-fixed tissue. Our observations extend the finding of calcitonin-like immunoreactivity in the carotid body chief cells and indicate that calcitonin is produced in the carotid body, probably in the chief cells.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
    ISSN: 1432-0878
    Schlagwort(e): Carotid body ; Calcitonin ; Cholecystokinin ; Immunoreactivity ; Chemoreception ; Human infant
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract Previous immunohistochemical studies have identified several regulatory peptides in the carotid body chief cells in both humans and animals. These peptides, together with amines, may be important in the modulation of the chemoreflex by the carotid body. We report the localization and distribution of calcitonin and cholecystokinin-like (CCK) immunoreactivity in chief cells of human infant carotid body by light- and electron-microscopic immunohistochemical techniques. Consecutive sections immunostained with calcitonin and/or CCK antibodies revealed positively stained chief cells, both alone and in clusters, scattered throughout the carotid body lobule. Generally more chief cells were positive for calcitonin than for CCK. This was confirmed by quantiative analysis showing that the ratio of calcitonin to CCK immunoreactive cells was consistently 〉2:1 in all cases studied. There was no apparent correlation between the immunoreactivity for the two peptides and the age, sex, or postmortem interval. Calcitonin-like and CCK-like immunoreactivities were localized electron-microscopically over the dense core granules of the chief cells. Calcitonin and CCK-like peptides in carotid body chief cells may act as neutransmitters or neuromodulators involved in chemoreception.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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