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  • 1
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 185 (1960), S. 250-251 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Immature oocytes of the Cecropia moth (family, Saturniidae), in which yolk formation was just beginning and in which the nucleus was clearly visible, provided a suitable material for this purpose. The ovarioles were removed from animals that had completed one-third of the pupal-adult moult, and ...
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 218 (1968), S. 184-185 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The principal objective of this investigation was to determine whether the breakdown of the nuclear envelope during mitosis is caused by a cytoplasmic factor. I have treated interphase nuclei with cytoplasm of dividing cells in these conditions, any degradation of the envelope would demonstrate the ...
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Cellular and molecular life sciences 29 (1973), S. 546-547 
    ISSN: 1420-9071
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Zusammenfassung Die relative Transportgeschwindigkeit von kolloidalem Gold durch die Membran des Zellkerns verringert sich, wenn die Temperatur von 34° auf 10°C herabgesetzt wird. Ein ähnlicher Temperatureffekt darf für den Transport von Ribonukleoproteinen angenommen werden, da diese Substanzen denselben Weg benützen wie kolloidale Teilchen. Werden die Zellen bei 2°C inkubiert, so machen sich Anzeichen einer Zerstörung der Kernmembrane bemerkbar. Die beobachteten Konzentrationsunterschiede von kolloidalem Gold innerhalb des Kernplasmas konnten nicht durch Grössenänderungen der Zentralkanäle in den Kernporen erklärt werden.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Molecular and cellular biochemistry 67 (1985), S. 87-99 
    ISSN: 1573-4919
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Summary A number of closely related post-transcriptional facets of RNA metabolism show nuclear compartmentation, including capping, methylation, splicing reactions, and packaging in ribonucleoprotein particles (RNP). These nuclear ‘processing’ events are followed by the translocation of the finished product across the nuclear envelope. Due to the inherent complexity of these interrelated events,in vitro systems have been designed to examine the processes separately, particularly so with regard to translocation. A few studies have utilized nuclear transplantation/ microinjection techniques and specialized systems to show that RNA transport occurs as a regulated phenomenon. While isolated nuclei swell in aqueous media and dramatic loss of nuclear protein is associated with this swelling, loss of RNA is not substantial, and most studies on RNA translocation have employed isolated nuclei. The quantity of RNA transported from isolated nuclei is related to hydrolysis of high-energy phosphate bonds in nucleotide additives. The RNA is released predominantly in RNP: messenger-like RNA is released in RNP which have buoyant density and polypeptide composition similar to cytoplasmic messenger RNP, but which have distinctly different composition from those in heterogeneous nuclear RNP. Mature 18 and 28S ribosomal RNA is released in 40 and 60S RNP which represent mature ribosomal subunits. RNA transport proceeds with characteristics of an energy-requiring process, and proceeds independently of the presence or state of fluidity of nuclear membranes. The energy for transport appears to be utilized by a nucleoside triphosphatase (NTPase) which is distributed mainly within heterochromatin at the peripheral lamina. Photoaffinity labeling has identified the pertinent NTPase as a 46 kD polypeptide which is associated with nuclear envelope and matrix preparations. The NTPase does not appear to be modulated via direct phosphorylation or to reflect kinase-phosphatase activities. A large number of additives (including RNA and insulin) produce parallel effects upon RNA transport and nuclear envelope NTPase, strengthening the correlative relationship between these activities. of particular interest has been the finding that carcinogens induce specific, long-lasting increases in nuclear envelope (and matrix) NTPase; this derangement may underlie the alterations in RNA transport associated with cancer and carcinogenesis. Two considerations for RNA transport studies are discussed: 1) RNA transportin vitro relates to nuclear swelling, and colloidally-active agents (such as polyvinylpyrrolidone) should be employed to prevent nuclear swelling; and 2) contamination of nuclear preparations by nucleus-absorbed cytoplasmic RNA is substantial, and a detergent-rinse procedure is required to remove this contamination. In considering trafficking of RNP through nuclear pores, conceptual difficulties are obvious. Flux studies with exogenous tracers have indicated patent pore diameters of 90–120 Å. However, the RNP which cross the nuclear envelope (presumably through pores) are all at least 200 Å in diameter. Further, evidence is presented showing that nucleoplasmin-coated gold particles (of diameter 200 Å) pass through central channels in nuclear pores. Whereas previous models of RNP transport have enjoyed the luxury of ascribing deformability (local unfolding) to these RNP, this clearly is not possible for the coated gold particles. These considerations suggest that facilitated translocation of RNP occurs in some manner, and that the mechanisms governing this translocation are not subject to the constraints suffered by exogenous tracers in a ‘rigid-channel’ model of the nuclear pore.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 205 (1980), S. 157-162 
    ISSN: 1432-0878
    Keywords: Nuclear envelope ; RNA transport ; Oocytes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Experiments were designed to determine if the synthesis, processing and transport of rRNA are affected by changes in nuclear permeability. RNA was labeled by microinjecting [3H]GTP into the cytoplasm of defolliculated oocytes. After injection, the nuclear envelopes were disrupted by puncturing the cells with glass needles. It has been shown that this procedure significantly alters the physical properties of the nuclear envelope. At appropriate intervals after puncturing, the oocytes were manually enucleated and RNA was extracted from both nuclear and cytoplasmic fractions. The extracts were analyzed on 2.5% polyacrylamide gels. The results indicate that over a period of 41/2 h neither the production nor the nucleocytoplasmic distribution of rRNA are affected by altering the permeability characteristics of the nuclear envelope.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 72 (1998), S. 214-219 
    ISSN: 0730-2312
    Keywords: nucleus ; nuclear envelope ; nuclear export ; nuclear import ; regulation ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The control of transcription and translation is of fundamental importance in cell biology. In this regard, the nuclear envelope is in a unique position to contribute to the regulation of these events, by directing macromolecular exchanges between the nucleus and cytoplasm. Such exchanges occur through the nuclear pore complexes, mainly by signal-mediated processes. Different signals are required for import and export. Specific cytoplasmic or nuclear receptors initially bind the signal-containing substrate, and the complex subsequently interacts with the pores. Additional factors then assist in translocation across the envelope. Current research is focused mainly on further characterization of transport receptors, translocation factors, as well as components of the nuclear pore complex, i.e., the nucleoporins. The ultimate goal is to understand the molecular interactions that occur among the different components of the transport apparatus, the energy sources for transport, and how variations in transport capacity are generated. J. Cell. Biochem. Suppls. 30/31:214-219, 1998. © 1998 Wiley-Liss, Inc.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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