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  • Key words Pristionchus pacificus  (1)
  • Röntgenfluorescenz-Spektrometrie  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Development genes and evolution 209 (1999), S. 451-459 
    ISSN: 1432-041X
    Keywords: Key words Pristionchus pacificus ; Vulva ; Induction ; Caenorhabditis elegans ; Evolution and development
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  One of the best known features of vulva development in Caenorhabditis elegans is the induction of vulval precursor cells by the gonadal anchor cell. Induction is crucial for the initiation of pattern formation within the C. elegans vulva equivalence group, and it is therefore surprising to find that this aspect of vulva formation, in particular, varies greatly among nematodes. In some species which form vulvae in the posterior body region, no gonadal signal is necessary for vulva induction. In other nematodes, such as Panagrolaimus, Oscheius, and Rhabditella, vulva formation depends on two temporally distinct gonadal inductions which specify the different cell fates. Here we report our analysis of vulva induction in Pristionchus pacificus, a specieswhich has recently been used as a genetic system to analyze the evolution of vulva development. Cell ablation studies in P. pacificus show that another mode of vulva induction exists. P. pacificus vulva formation depends on a continuous gonadal induction that starts several hours after hatching and continues until the birth of the anchor cell, some 20 h later. Mutations defective in gonadal induction result in the absence of vulva differentiation, suggesting that only one signaling system is involved in the gonadal-epidermal interaction. This new mode adds further to the great variety of gonadal inductions among nematode species.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Fresenius' Zeitschrift für analytische Chemie 307 (1981), S. 177-184 
    ISSN: 1618-2650
    Keywords: Röntgenfluorescenz-Spektrometrie ; Eliminierung von Interelementeffekten ; Pulververdünnung
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Summary If the concentration of elements with Z〉22 (Ti) is to be determined in mineral samples and if the concentration of any of these elements is greater than ≈ 1%, the sample is diluted by grinding it together with an appropriate amount of quartz powder in an agate mortar mill. The diluted sample is measured in powdered form in a spectro-cup at practically infinite thickness by energy-dispersive X-ray fluorescence; the counting rates are corrected by means of the Compton scattering peak and evaluated by use of calibration curves obtained by measuring standards on the basis of silica gel. The applicability of this method is established by measuring the concentrations of 12 elements with Z〉22 in 14 mineral samples of varying composition.
    Notes: Zusammenfassung Wenn die Konzentration von Elementen mit Ordnungszahlen Z〉22 (Ti) in mineralischen Proben bestimmt werden soll, und wenn die Konzentration eines dieser Elemente größer als ≈ 1% ist, wird die Probe durch Mahlen mit einer geeigneten Menge Quarz-Pulver in einer Achatmörsermühle verdünnt. Die verdünnte Probe wird in Pulverform in einem „spectro-cup“ bei praktisch unendlicher Schichtdicke durch energiedispersive Röntgenfluorescenz gemessen, die Zählraten werden mit Hilfe des Compton-Streupeaks korrigiert und unter Verwendung von Eichkurven ausgewertet, die durch Messung von Standards auf der Basis von Silicagel erhalten werden. Die Anwendbarkeit dieser Methode wird überprüft durch Bestimmung der Konzentration von 12 Elementen mit Ordnungszahlen Z〉22 in 14 mineralischen Proben verschiedener Zusammensetzung.
    Type of Medium: Electronic Resource
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