Nuclear pore complexes (NPCs) mediate both active transport and passive diffusion across the nuclear envelope (NE). Determination of NE electrical conductance, however, has been confounded by the lack of an appropriate technical approach. The nuclear patch clamp technique is restricted to preparations with electrically closed NPCs, and microelectrode techniques fail to resolve the extremely low input resistance of large oocyte nuclei. To address the problem, we have developed an approach for measuring the NE electrical conductance of Xenopus laevis oocyte nuclei. The method uses a tapered glass tube, which narrows in its middle part to 2͞3 of the diameter of the nucleus. The isolated nucleus is sucked into the narrow part of the capillary by gentle fluid movement, while the resulting change in electrical resistance is monitored. NE electrical conductance was unexpectedly large (7.9 ؎ 0.34 S͞cm 2 ). Evaluation of NPC density by atomic force microscopy showed that this conductance corresponded to 3.7 ؋ 10 6 NPCs. In contrast to earlier conclusions drawn from nuclear patch clamp experiments, NPCs were in an electrically ''open'' state with a mean single NPC electrical conductance of 1.7 ؎ 0.07 nS. Enabling or blocking of active NPC transport (accomplished by the addition of cytosolic extracts or gp62-directed antibodies) revealed this large NPC conductance to be independent of the activation state of the transport machinery located in the center of NPCs. We conclude that peripheral channels, which are presumed to reside in the NPC subunits, establish a high ionic permeability that is virtually independent of the active protein transport mechanism.nucleus ͉ electrophysiology N uclear envelopes (NEs) of Xenopus laevis oocytes have been the favored preparation for evaluation of nuclear transport and for studies of nuclear pore complexes (NPCs) structure and function, but only limited data are available on the electrophysiological properties of this important barrier, mainly because of technical limitations.Electrophysiological evaluation of NE started in the early sixties. Using two microelectrodes impaling the nucleus of a Drosophila salivary gland cell, Loewenstein and his coworkers (1) measured the electrical conductance of the NE. The conductance was much smaller than they had expected. At that time, NPCs were thought to be open gaps in the nuclear membrane with a diameter of at least 40 nm. From their electrical conductance measurements, Loewenstein and coworkers concluded that a protein structure must be present in these gaps that restricts the opening to less than 10 nm, resulting in an electrical conductance of about 1 nS per nuclear pore (2). This observation came very close to the view of the nuclear pore that has emerged as a result of much later studies, in which the diffusion of differently sized molecules was measured. According to this view, the NPC forms an aqueous channel of 8-12 nm in diameter and 40-50 nm in length (3). From this data, a NPC electrical conductance of 1-2 nS can be calculated (4).In ...

Zusammenfassung Dieser Beitrag wirft einen kritischen Blick auf die Frage, ob ökonomische Bildung zum besseren Verständnis, erhöhtem Interesse und letztlich gesteigerter Aktivität im Hinblick auf eigenverantwortliche private Vorsorge in Deutschland führt. Zu diesem Zweck wurde unter 600 Studierenden der Fachbereiche Wirtschafts-, Sprach-und Rechtswissenschaften der Universität Münster eine Umfrage mit angeschlossenem Financial Literacy-Test durchgeführt. Insbesondere der Financial Literacy-Test offenbart sowohl Selektions-als auch Indoktrinationsbzw. Lerneffekte ökonomischer Bildung. Ein höherer Bildungsgrad in Finanzfragen erweist sich ferner als wichtiger Treiber einer positiven Einstellung gegenüber privater Altersvorsorge. Im Hinblick auf die Einstellung und Affinität gegenüber der privaten Altersvorsorge bestehen jedoch nur noch schwache Unterschiede zwischen Ökonomen und Nicht-Ökonomen (Selektionseffekt), sowie zwischen Ökonomen verschiedener Ausbildungsstufen (Indoktrinationseffekt). Vor dem Hintergrund der zunehmenden Bedeutung privater Vorsorge lässt sich demnach die Handlungsempfehlung aussprechen, explizit die Altersvorsorge als Bestandteil der ökonomischen Bildung -etwa in Schulen -zu etablieren. Schlüsselwörter Private Altersvorsorge · Financial Literacy · Ökonomen vs. Nicht-Ökonomen · Selektionseffekt · Indoktrinationseffekt 326 B. Kramer, R. RuskeAbstract This paper takes a critical look at the question of whether Economic Education leads to a better understanding of an increased interest in and ultimately to a higher level of private provision in Germany. For this purpose, a survey was carried out with an attached Financial Literacy test among 600 students of economics, linguistics and law from the University of Münster. In particular, the Financial Literacy test reveals both selection-and indoctrination-or learning effects of economic education. A higher level of Financial Literacy also showed to be an important driver of a positive attitude towards private provision. With regard to the attitude and affinity towards private pensions, however, only weak differences between economists and non-economists (selection effect), and between economists of different levels of education can be found (indoctrination effect). Given the increasing importance of private provision one can thus express the recommendation to explicitly establish "retirement" as part of economic education-for example in schools.