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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The concentration of free calcium ions in the cytosol has been shown to influence many components of growth cone behaviour, including the extension of filopodia and veils, the addition of new membrane to the plasmalemma, the retraction and disappearance of filopodia, and gross collapse and retraction of the growth cone. A spatially localized modulation of these processes by very local calcium changes has been proposed to underlie the steering of growth cones by gradients of neurotransmitters, voltage and cell adhesion molecules. Such local control can be studied in mouse neuroblastoma cells, where depolarization causes calcium to rise in a limited number of spatially restricted hotspots, triggering a localized advance. We have studied the simple, club-shaped growth cones that are characteristically found on advancing neurites. Depolarization caused calcium to increase most at the distal, leading tip. Agents that disrupt calcium-induced calcium release do not affect growth cone calcium dynamics, ruling out a local release of calcium at the tip as a cause of the gradient. Using cell-attached patch recording, we find that L-type calcium channels are present at a higher density at the distal tip than in the proximal growth cone. Our results show that the calcium gradients seen in depolarized growth cones are a direct consequence of a gradient of calcium channel density.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0044-281X
    Keywords: Schlüsselwörter Intelligenzentwicklung – Altern – Informationsverarbeitungsgeschwindigkeit –“Latent Growth Curve Models” ; Key words Cognitive development – elderly – mental speed – latent growth curve model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary According to the “speed”-hypothesis of cognitive development, the slowing of information processing in old age is at the core of negative age differences in psychometric intelligence. The present study investigates the “speed”-hypothesis for fluid intelligence at the individual level using Latent Growth Curve Methodology. Date on 4 measurement points come from the Bonn Longitudinal Study of aging (N=128, mean age 67.2, 53% women). Based on principal factor analysis, markers of mental speed were the WAIS Digit Symbol Test and simple psychomotor task. As indicators of fluid intelligence the WAIS Object Assembly and Block Design were used. After separately fitting Latent Growth Curve Models for the trajectory of mental speed and fluid intelligence, a combined model showed no statistically significant improvement of fit for freeing the covariance between the two slope-factors. Interpreting this result, contrary to the “speed”-hypothesis the intraindividual change of fluid intelligence does not relate to the according change of mental speed.
    Notes: Zusammenfassung Die “Speed”-Hypothese der Intelligenzentwicklung postuliert, daß die im Alter zurückgehende Geschwindigkeit der Informationsverarbeitung die zentrale kritische Ressource für psychometrische Intelligenz darstellt. Die vorliegende Arbeit unternimmt den Versuch, die “Speed”-Hypothese unter Verwendung von “Latent Growth Curve Models” auf ihre individuelle Gültigkeit für die Entwicklung der fluiden Intelligenz hin zu überprüfen. Dazu wird auf 4 Meßzeitpunkte des Datenmaterials der Bonner Längsschnittstudie zurückgegriffen (N=128, mittleres Alter 67,2 Jahre, 53% Frauen). Basierend auf einer Hauptfaktorenanalyse werden der HAWIE-Zahlen-Symbol-Test sowie die Leistungen bei einer einfachen psychomotorischen Geschwindigkeitsaufgabe als Indikatoren für Informationsverarbeitungsgeschwindigkeit und die HAWIE-Subtests Figurenlegen und Mosaiktest als Indikatoren für fluide Intelligenz herangezogen. Nach dem getrennten Anpassen zweier “Latent Growth Curve Models” für “speed” und fluide Intelligenz kann in einem kombinierten Modell die Übereinstimmung mit dem Datenmaterial durch eine freie Schätzung der Kovarianz zwischen den beiden “Slope”-Faktoren nicht verbessert werden. Dieses Ergebnis spricht gegen die “Speed”-Hypothese, da die intraindividuellen Veränderungen von fluider Intelligenz nicht mit den entsprechenden Veränderungen der Informationsverarbeitungsgeschwindigkeit zusammenhängen.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: The actions of exogenous and endogenous opioids are mediated by at least three different opioid receptors, called μ, κ, and δ. Recently, we have detected a new variant of the rat μ-opioid receptor, which we termed rMOR1B and which differs from rMOR1 (now also called rMOR1A) in the amino acid sequence at the C-terminus. Both isoforms were proposed to be splicing variants of the same gene. To elucidate the molecular mechanism leading to the formation of the new variant, the exon/intron structure of the rat μ-opioid receptor gene in the respective area has been determined by analyzing a genomic P1 phage clone. In addition, we have investigated the putative promoter region of this gene. The present study revealed that rMOR1B is generated by an alternative splicing event whereby a previously unknown exon will be placed behind exon 3 to form rMOR1B mRNA, which is separated from the latter by an intron. Therefore, this new exon has to be called exon 4, whereas the former exon 4, which encodes the C-terminus of MOR1A, now becomes exon 5. Examination of the putative rat promoter region revealed a high degree of nucleotide sequence homology to the mouse gene. Using an RNase protection approach, one single transcription initiation site could be located at 230 bp upstream of the translation start. This is similar to the situation in the mouse, where four major transcription start sites were reported to lie close together around 270 bp upstream of the protein coding region.
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  • 4
    ISSN: 1432-2013
    Keywords: Key words Calcium oscillations ; Development ; In situ ; Intracellular calcium ([Ca2+]i) measurement ; Neurons ; Zebrafish
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  We have developed a non-invasive technique to measure intracellular calcium ([Ca2+]i) in neurons growing within intact embryos of the zebrafish (Danio rerio). A single blastomere was injected with a calcium-sensitive fluorescent dye (Calcium Green dextran) between the 32- and 128-cell stage and the embryo imaged between 16 h and 20 h postfertilisation using laser scanning confocal microscopy. Labelled nerve cells from embryos preinjected with dye and dissociated at 16 h showed a fluorescence increase (66±22%; n=11) in response to depolarisation with KCl confirming that the dye remained intracellular and was sensitive to calcium. In addition, fluorescence changes in activated muscle cells of intact embryos showed that the dye was capable of responding to [Ca2+]i changes in vivo. Imaging of dye loaded cells over 30-min periods in embryos between 16 and 20 h revealed that the majority of neurons within the brain and spinal cord did not show spontaneous fluorescence changes distinguishable from noise. However, a subset of neurons within the ventral spinal cord exhibited spontaneous, repetitive [Ca2+]i oscillations which may have a functional significance during neuronal development.
    Type of Medium: Electronic Resource
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