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A lamin in lower eukaryotes?
(2012)
Lamins are the major components of the nuclear lamina and serve not only as a mechanical support, but are also involved in chromatin organization, epigenetic regulation, transcription and mitotic events. Despite these universal tasks, lamins have so far been found only in metazoans. Yet, recently we have identified Dictyostelium NE81 as the first lamin-like protein in a lower eukaryote. Based on the current knowledge, we draw a model for nuclear envelope organization in Dictyostelium in this Extra View and we review the experimental data that justified this classification. Furthermore we provide unpublished data underscoring the requirement of posttranslational CaaX-box processing for proper protein localization at the nuclear envelope. Sequence comparison of NE81 sequences from four Dictyostelia with bona fide lamins illustrates the evolutional relationship between these proteins. Under certain conditions these usually unicellular social amoebae congregate to form a multicellular body. We propose that the evolution of the lamin-like NE81 went along with the invention of multicellularity.
Aus dem Inhalt:
- Die Rolle Nationaler Menschenrechtsinstitutionen bei der Umsetzung der UN-Leitprinzipien für Wirtschaft
und Menschenrechte: Paradoxien und Potenziale
- Lehrbuchbeispiel des Versagens: Die Schutzverantwortung und die Rohingya in Myanmar
- Rechtsfragen der Umsetzung von Urteilen des Europäischen Gerichtshofs für Menschenrechte
Am 25. und 26. Juni 2004 fand die sechste Konferenz des Forschungskreises Vereinte Nationen an der Universität Potsdam statt. Die Konferenz befaßte sich mit dem Thema „Integrative Konzepte in der Reform der Vereinten Nationen". Kennzeichnend für die „Potsdamer UNO-Konferenzen", die traditionell am letzten Wochenende im Juni veranstaltet werden, sind die Verbindung von Wissenschaft und Praxis auf der einen Seite und die Beteiligung unterschiedlicher Disziplinen auf der anderen. Sieben Referate beschäftigten sich mit bisher nicht oder nicht genügend in der Arbeit der Vereinten Nationen einbezogenen Aspekten bei der Struktur-Reform. Die nachstehend abgedruckten sechs Beiträge - von Dr. Jochen Prantl, der zum Thema „Informelle Staatengruppen als Instrument zur Konfliktregulierung: Auswirkungen auf die Arbeitsweise des Sicherheitsrates der Vereinten Nationen" referiert hatte, lag bei der Drucklegung der Broschüre kein Manuskript vor - und die zugehörigen Diskussionen, die hier zusammengefaßt wiedergegeben werden, geben ein anschauliches Bild von der Komplexität der Aufgabe „UN-Reform". Die damit verbundenen Fragen, die für das zukünftige Funktionieren der Vereinten Nationen, aber auch für das Klima innerhalb der internationalen Gemeinschaft sehr wichtig sind, werden in dieser Dokumentation diskutiert. Die im Forschungskreis vertretene deutschsprachige UN-Forschung machte auf der Konferenz deutlich, daß man zu kurz greift, wenn sich die Reformdiskussion auf den ständigen Sitz für die Bundesrepublik Deutschland im Sicherheitsrat beschränkt. Der Forschungskreis möchte mit dieser Broschüre allen Interessierten die Möglichkeit geben, andere, nicht minder wichtige Aspekte dieser Diskussion kennenzulernen. Der Forschungskreis dankt der Juristischen Fakultät der Universität Potsdam für die Gastfreundschaft und dem MenschenRechtsZentrum der Universität Potsdam für die Kooperation bei der Organisation der Konferenz.
Polyanion-polycation complex formation as a function of the position of the functional groups
(1996)
Background
The hypopharyngeal gland of worker bees contributes to the production of the royal jelly fed to queens and larvae. The gland consists of thousands of two-cell units that are composed of a secretory cell and a duct cell and that are arranged in sets of about 12 around a long collecting duct.
Results
By fluorescent staining, we have examined the morphogenesis of the hypopharyngeal gland during pupal life, from a saccule lined by a pseudostratified epithelium to the elaborate organ of adult worker bees. The hypopharyngeal gland develops as follows. (1) Cell proliferation occurs during the first day of pupal life in the hypopharyngeal gland primordium. (2) Subsequently, the epithelium becomes organized into rosette-like units of three cells. Two of these will become the secretory cell and the duct cell of the adult secretory units; the third cell contributes only temporarily to the development of the secretory units and is eliminated by apoptosis in the second half of pupal life. (3) The three-cell units of flask-shaped cells undergo complex changes in cell morphology. Thus, by mid-pupal stage, the gland is structurally similar to the adult hypopharyngeal gland. (4) Concomitantly, the prospective secretory cell attains its characteristic subcellular organization by the invagination of a small patch of apical membrane domain, its extension to a tube of about 100 μm in length (termed a canaliculus), and the expansion of the tube to a diameter of about 3 μm. (6) Finally, the canaliculus-associated F-actin system becomes reorganized into rings of bundled actin filaments that are positioned at regular distances along the membrane tube.
Conclusions
The morphogenesis of the secretory units in the hypopharyngeal gland of the worker bee seems to be based on a developmental program that is conserved, with slight modification, among insects for the production of dermal glands. Elaboration of the secretory cell as a unicellular seamless epithelial tube occurs by invagination of the apical membrane, its extension likely by targeted exocytosis and its expansion, and finally the reorganisation of the membrane-associated F-actin system. Our work is fundamental for future studies of environmental effects on hypopharyngeal gland morphology and development.
Background
The hypopharyngeal gland of worker bees contributes to the production of the royal jelly fed to queens and larvae. The gland consists of thousands of two-cell units that are composed of a secretory cell and a duct cell and that are arranged in sets of about 12 around a long collecting duct.
Results
By fluorescent staining, we have examined the morphogenesis of the hypopharyngeal gland during pupal life, from a saccule lined by a pseudostratified epithelium to the elaborate organ of adult worker bees. The hypopharyngeal gland develops as follows. (1) Cell proliferation occurs during the first day of pupal life in the hypopharyngeal gland primordium. (2) Subsequently, the epithelium becomes organized into rosette-like units of three cells. Two of these will become the secretory cell and the duct cell of the adult secretory units; the third cell contributes only temporarily to the development of the secretory units and is eliminated by apoptosis in the second half of pupal life. (3) The three-cell units of flask-shaped cells undergo complex changes in cell morphology. Thus, by mid-pupal stage, the gland is structurally similar to the adult hypopharyngeal gland. (4) Concomitantly, the prospective secretory cell attains its characteristic subcellular organization by the invagination of a small patch of apical membrane domain, its extension to a tube of about 100 μm in length (termed a canaliculus), and the expansion of the tube to a diameter of about 3 μm. (6) Finally, the canaliculus-associated F-actin system becomes reorganized into rings of bundled actin filaments that are positioned at regular distances along the membrane tube.
Conclusions
The morphogenesis of the secretory units in the hypopharyngeal gland of the worker bee seems to be based on a developmental program that is conserved, with slight modification, among insects for the production of dermal glands. Elaboration of the secretory cell as a unicellular seamless epithelial tube occurs by invagination of the apical membrane, its extension likely by targeted exocytosis and its expansion, and finally the reorganisation of the membrane-associated F-actin system. Our work is fundamental for future studies of environmental effects on hypopharyngeal gland morphology and development.