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Strategien zur Bekämpfung der Roßkastanienminiermotte (Cameraria ohridella) im urbanen Bereich
(2006)
Von einzelnen Ausnahmen abgesehen befällt die Rosskastanienminiermotte, Cameraria ohridella Deschka & Dimic 1986, die weißblühende Rosskastanie Aesculus hippocastanum L. Die Blütenpracht der Bäume im Frühjahr, die großen schattenspendenden Blätter im Sommer und die als Spielzeug begehrten Früchte im Herbst verhalfen der Rosskastanie zu großer Beliebtheit. Mittlerweile spielen die Bäume in Parks und entlang von Straßen eine ebenso bedeutende Rolle wie in privaten Gärten und sind aus vielen Städten in ganz Europa nicht mehr wegzudenken. Der kontinuierliche Massenbefall der Bäume durch die Kastanienminiermotte und die daraus resultierenden Folgekosten stellen deshalb vor allem im städtischen Siedlungsbereich nicht nur ein ästhetisches, sondern auch ein beträchtliches ökonomisches Problem dar, außerdem verlieren die Bäume bei starken Befall ihre wichtige stadtklimatische Funktion (BALDER, 2002). Im Projekt „BerlinCam“ werden Bekämpfungsmethoden gesucht, die den speziellen Bedürfnissen des Pflanzenschutzes im urbanen Grün gerecht werden sollen. Auf ihre Unbedenklichkeit gegenüber der Bevölkerung wird dabei genauso geachtet wie auf ihre Anwendbarkeit an stark frequentierten oder verkehrsbelasteten öffentlichen Flächen. Nicht zuletzt müssen die Bekämpfungsmaßnahmen auch modernen, hohen Umweltstandards genügen und trotz allem ökonomisch vertretbar sein. Im folgenden wird ein Beispiel aus dem Projekt vorgestellt, das zum jetzigen Zeitpunkt Ansatzpunkte für eine erfolgreiche Bekämpfung von C. ohridella im urbanen Bereich zeigen könnte. Dabei handelt es sich um die Anwendung von systemischen Pflanzenschutzmitteln als Depotverfahren. Diese Methode und die applizierten Produkte sind derzeit noch nicht in Deutschland zur Bekämpfung der Kastanienminiermotte zugelassen.
Informationen zu historischen Fraßschäden durch Forstinsekten konnten in der Vergangenheit allein über die Anlage von Langzeituntersuchungsflächen erhoben oder mit Hilfe von Jahrringanalysen abgeschätzt werden. Ein Langzeitmonitoring, wie es auch seit 1984 auf Level II - Flächen in Bundesforsten durchgeführt wird, ist allerdings mit hohem zeitlichen und finanziellem Aufwand verbunden und deckt zudem nur einen kurzen Zeitraum ab. Mittels Jahrringanalysen erhält man zwar weiter zurückreichende Informationen, diese sind jedoch mit einer gewissen Unsicherheit behaftet, da nur über ein Ausschlußverfahren klimatische bzw. abiotische Ursachen für Zuwachsstörungen ausgeschlossen werden. Eine Methode, mit der man direkt dort ansetzen kann, wo der Schaden passiert – an der Belaubung eines Baumes – war in der Vergangenheit nicht gegeben. Seit Anfang der 1990er Jahre ist dies jedoch mit dem sog. Nadelspurverfahren (KURKELA & JALKANEN 1990) möglich. Mit Hilfe dieser Technik kann die Benadelung von Koniferen retrospektiv entlang von Hauptachsen (Stamm, Äste) über das gesamte Lebensalter eines Baumes aufgedeckt werden, wobei die erhobenen Benadelungsparameter eine direkte Auskunft über Auffälligkeiten im enadelungsmuster geben (JALKANEN 1995, SANDER 1997) können.
The map of “Regional natural forest composition by main tree species” (WALENTOWSKI et al. 2001) depicts Bavaria as a region largely predominated by the European beech (Fagus sylvatica). Analyses of climatope, hygrotope and trophotope of fir-dominated regional natural units make evident that the reasons for the preponderance of the European silver fir (Abies alba) are edaphic. In terms of regeneration vigour, growth and yield the fir particularly dominates in habitats with a combination of humus cover, acid-oligotrophic topsoils and clayey or waterlogged subsoils, where the beech usually exhibits stunted and malformed growth forms. This ecological preference has the effect that Bavarian Abies alba-forests are restricted to small patches within a matrix of potential natural vegetation formed by mixed deciduous-coniferous mountain forests. Within European Natura 2000 areas Abies- forests should be recorded carefully as special habitats. Their transitional character between temperate beech forests (habitat type 9130) and boreal spruce forests (habitat type 9410), the ecological preference of Abies alba as an endangered tree species and their sensitivity against environmental stressors, including changes in forest structure, air quality, and climate, make them important objects for nature conservation.
Background The EGF receptor has been shown to internalize via clathrin-independent endocytosis (CIE) in a ligand concentration dependent manner. From a modeling point of view, this resembles an ultrasensitive response, which is the ability of signaling networks to suppress a response for low input values and to increase to a pre-defined level for inputs exceeding a certain threshold. Several mechanisms to generate this behaviour have been described theoretically, the underlying assumptions of which, however, have not been experimentally demonstrated for the EGF receptor internalization network. Results Here, we present a mathematical model of receptor sorting into alternative pathways that explains the EGF-concentration dependent response of CIE. The described mechanism involves a saturation effect of the dominant clathrin-dependent endocytosis pathway and implies distinct steady-states into which the system is forced for low vs high EGF stimulations. The model is minimal since no experimentally unjustified reactions or parameter assumptions are imposed. We demonstrate the robustness of the sorting effect for large parameter variations and give an analytic derivation for alternative steady-states that are reached. Further, we describe extensibility of the model to more than two pathways which might play a role in contexts other than receptor internalization. Conclusions Our main result is that a scenario where different endocytosis routes consume the same form of receptor corroborates the observation of a clear-cut, stimulus dependent sorting. This is especially important since a receptor modification discriminating between the pathways has not been found. The model is not restricted to EGF receptor internalization and might account for ultrasensitivity in other cellular contexts.
Die Naturraumerkundung nach KOPP, JÄGER & SUCCOW (1982) ist ein umfassendes landschaftsökologisches Methodenkonzept, auf welchem die forstliche Standortserkundung in Ostdeutschland basiert (siehe KOPP & SCHWANECKE 1994, SCHULZE & KOPP 1995) und auch bereits bei der Moorforschung breite Anwendung gefunden hat (siehe SUCCOW 1988, SUCCOW & JOOSTEN 2001). Mit der Naturraumerkundung lassen sich die Zusammenhänge zwischen Standort, Vegetation und Nutzung sehr gut erfassen, und bezüglich ökologischer Funktionen und Nutzbarkeit interpretieren. Deshalb wird die Methode auch bei anwendungsorientierten landschaftsökologischen Untersuchungen im Tienschan eingesetzt (GOTTSCHLING 2003). Im Folgenden werden Erfahrungen mit der in Mitteleuropa entwickelten Naturraumerkundung unter den Bedingungen des Tienschan-Gebirges in Mittelasien dargestellt.
Zur Biodiversität von Spinnen (Araneae) und Laufkäfern (Carabidae) auf sächsischen Ackerflächen
(2006)
Im Rahmen eines Forschungsprojektes der Sächsischen Landesanstalt für Landwirtschaft erfolgten zönologische Studien in vier praxisrelevanten Bewirtschaftungsvarianten. Das primäre Untersuchungsziel bestand in der Einschätzung des Förderprogramms „Umweltgerechte Landwirtschaft (UL)“ hinsichtlich seiner Effekte auf die Biodiversität typischer Ackerstandorte im Freistaat Sachsen. Unter anderem wurden dazu Laufkäfer (Coleoptera: Carabidae) und Webspinnen (Araneae) als Indikatoren genutzt. Über die ökologische Bewertung der verschiedenen Bewirtschaftungsvarianten hinaus wird die Nutzung der Biodiversität von Ackerflächen und deren Indikation anhand von Raubarthropoden und anderen Organismengruppen diskutiert.
Chemo-communication is an important mode of interaction within ecosystem. The living organism in the ecosystem can deliver signals to conspecifics, to co-organisms, and unintentionally to their enemies, by emitting the volatile organic compounds (VOCs) to the atmosphere. There are some insect-fungi-associations displaying interesting relationships. For example, some bark beetle species (PAINE et al. 1997) introduce fungi into the conifers during the attack process. Fungi take advantage by associating with the insect in transport to new trees and passage through the bark. Insects may get advantage by feeding on fungi and overcoming the tree defence. Questions arise how fungus vectoring insects can recognize the weakness of defense mechanism in the case to introduce the fungus to the host tree and successfully overcome the remaining defence mechanisms. The interspecific communication among insects, fungi and host trees are not completely clarified, but there was the evidence that a number of forest scolytids including species in the genera Scolytus, Dendroctonus, Hylurgops, Trypodendron and Tomicus can be attracted to the host volatile compounds (BYERS 1995).
Die Gefährdung der Eiche durch biotische Schaderreger ist in der einschlägigen Fachliteratur umfänglich beschrieben (u.a. PATOKA 1980, HARTMANN 1995, ALTENKIRCH et al. 2000). Im Jahr 2004 rückte die Fraßgesellschaft der Eiche im Zusammenhang mit den beobachteten „Austriebsdepressionen“ in den besonderen Fokus der Waldschutzüberwachung in Brandenburg. Im Mai 2004 gab es aus allen Ämtern für Forstwirtschaft Brandenburgs Meldungen über massive Austriebsstörungen, d.h. die Terminalknospen waren nur schwach entwickelt oder bereits abgestorben, nicht selten war die gesamte Triebspitze kaum noch lebensfähig. Die Untersuchung des Materials zeigte, dass keine primären pilzlichen Schaderreger und die Eichenfraßgesellschaft in unterschiedlichem Maß, zumeist aber mit sehr geringen Populationsdichten, an den Blattmasseverlusten beteiligt waren. Ursächlich schien die Austriebsstörung zu sein. Die überregionale Verbreitung der Schäden und die Symptomausprägung deuten auf eine abiotische Beeinträchtigung der Eichen hin. Die Annahme einer witterungsbedingten Schädigung ist nahe liegend, da im Rekordsommer“ 2003 mit über dem Durchschnitt liegenden Temperaturen, erheblichen Niederschlagsdefiziten und überdurchschnittlich hoher Sonnenscheindauer extreme Witterungsverhältnisse herrschten. Im Oktober 2003 kam es zu einem plötzlichen, gravierenden Temperatursturz. Überhöhte Temperaturen im Februar führten zu einer erneuten Belastung des Stoffwechsels der Eichen (HEYDECK & MÖLLER 2004).
Anfang Mai 2004 wurden die ersten Anzeichen für die Einschleppung einer invasiven gebietsfremden Art, des baumschädigenden Bockkäfers Anoplophora glabripennis, nach Bayern festgestellt. Ein Ahornbaum am Rande des Parkplatzes vom Friedhof in Neukirchen am Inn (Gemeinde Neuburg am Inn, Landkreis Passau) wies verdächtige Symptome wie Fehlstellen in der Belaubung und kraterförmige Vertiefungen (Eiablagegruben?) in seiner Rinde auf. In unmittelbarer Nachbarschaft zum Friedhof liegt zudem eine Spedition, bei der Granitsteine und andere Granitwaren, teilweise aus dem asiatischen Raum, umgeschlagen bzw. auf Holzpaletten auf dem Betriebsgelände längere Zeit gelagert werden. Von diesem Ahorn wurden verdächtige Aststücke entnommen und im Labor an der Landesanstalt für Landwirtschaft (LfL) in Freising vorsichtig aufgespalten. Es fanden sich Bohrgänge und Bockkäferlarven, die jedoch eine unterschiedliche Größe aufwiesen. Die dorsale Chitinplatte der Vorderbrust hatte aber die typische burgzinnenartige Form, die als morphologisches Bestimmungskriterium von A. glabripennis in der Literatur angegeben wird (HOYER et al. 2003). Zur eindeutigen Absicherung wurden die Larven an das Bundesamt und Forschungszentrum für Wald (BFW) in Wien geschickt. Die Kolleginnen und Kollegen aus Österreich hatten aufgrund des aufsehenerregenden Fundes von A. glabripennis in Braunau am Inn (Erstfund für Europa, 2001) inzwischen die größte Erfahrung in der sicheren Diagnose des Asiatischen Laubholzbockkäfers. Da bereits damals eine erhöhte Gefahr des „unerlaubten Grenzübertrittes“ ins 300 m entfernte bayerische Simbach am Inn bestand, waren schon Kontakte geknüpft und es wurde auch kollegiale Hilfe angeboten. Die schnelle und unbürokratische Hilfe führte beim Verdachtsfall in Neukirchen am Inn zu einer raschen Aufklärung. Über eine DNA-Analyse mittels PCR konnte in Wien innerhalb kürzester Zeit bestätigt werden, dass es sich bei den Larven um A. glabripennis handelte. Mit hoher Wahrscheinlichkeit stand auch fest, dass der Einschleppungsweg über die asiatischen Holzpaletten der Spedition abgelaufen sein musste. Wenn man eine einjährige Generationsdauer des Käfers in Mitteleuropa voraussetzt, dann war das Einschleppungsjahr 2003. Da aber bei den meisten Wirtsbäumen inzwischen sogar ein zweijähriger Zyklus angedacht wird, war die Einschleppung vermutlich schon 2002.
Für die Ernährung der Waldbiozönose spielt der Honigtau, das Exkret phloemsaugender Homopteren, eine wesentliche ernährungsphysiologische Rolle (ZÖBELEIN 1954a, b, WELLENSTEIN 1952). Insbesonders stehen Ameisen mit zahlreichen Spezies von Aphiden und Cocciden in mehr oder weniger enger trophobiotischer Beziehung, denn sie decken ihren Kohlenhydratbedarf fast ausschließlich durch den Honigtau ab (WELLENSTEIN 1952, BUCKLEY 1987; HÖLLDOBLER & WILSON 1990). Die Sesshaftigkeit und der Aufbau großer volkstarker Kolonien bei den forstlich bedeutsamen Waldameisen (Formica s.str.) in den gemäßigten Breiten ist wesentlich auf die trophobiotische Nutzung quantitativ besonders starker Honigtauerzeuger, wie etwa die Lachniden und Lecanien, zurückzuführen (GÖßWALD 1990). An der Fichte (Picea abies) leben 5 Lachnidenarten (Cinara spec.) und 2 Lecanienarten (Physokermes spec.), deren Beziehung zu Ameisen unterschiedlich stark ist (KLOFT et al. 1985). Die vorliegende Freilandstudie befasst sich mit der saisonalen Entwicklung von 2 koexistierenden Fichtenlachnidenarten – der obligatorisch myrmekophilen Cinara piceicola (CHOLODKOVSKY) und der fakultativ myrmekophilen Cinara pruinosa (HARTIG) – in Abhängigkeit des Besuches der Kleinen Roten Waldameise Formica polyctena FÖRSTER. Inwieweit eine interspezifische Konkurrenz der beiden Cinara-Arten um den Mutualisten F. polyctena vorherrscht, ist ebenso Gegenstand der Untersuchung.
Im Bereich der Baumkronen ist eine auffallend hohe biologische Vielfalt von Arthropoden zu finden. Nicht nur in naturnahen Räumen, sondern auch im unmittelbaren Siedlungsbereich kann diese Diversität nachgewiesen werden. Als Basis für den Naturschutz und die Biodiversitätsforschung sind kontinuierliche Beobachtungen notwendig. Parasitoide Hymenopteren spielen eine wichtige Rolle als Regulatoren im Naturhaushalt. Sie begrenzen das Auftreten wirtschaftlich bedeutender Schädlinge und sind somit ein Baustein im integrierten Pflanzenschutz. Die Reduktion von Pflanzenschutzmitteln trägt zur Schonung und Förderung von nützlichen Arthropoden, den räuberischen Insekten und parasitoiden Hymenopteren bei. Übersichten zur Biodiversität in Deutschland zeigen, dass im Bereich der sogenannten ´Schlupfwespen´ viele Gruppen für Deutschland nur wenig bearbeitet sind (DATHE et al. 2001), obwohl es sich bei den parasitoiden Hymenopteren neben den Coleopteren um die größte Insektengruppe überhaupt handelt. Die Chalcidoidea und die Ichneumonoidea stellen hier die größten Überfamilien der parasitoiden Hymenopteren. Weltweit liegt der Anteil der Chalcidoidea nach Arten bei 25%, in Deutschland bei 15%. In dieser Überfamilie finden sich die wichtigsten der in der biologischen Schädlingsbekämpfung genutzten Arthropoden: z.B. Encarsia formosa, die Gegenspielerin der ´Weißen Fliege´ im Gewächshaus oder Trichogramma-Arten als natürliche Feinde von Schadmotten. Insgesamt sind für Deutschland etwa 1.800 Chalcidoidea bekannt. Sie werden in 18 Familien unterteilt, wobei die Pteromaliden die größte Familie darstellen.
Two botanical pesticides, Neem Azal-T/S (NA) and Quassia amara, one biopesticide, Bacillus thuringiensis subsp. aizawai (Bta) and one combination of Bta + NA were tested against 2nd and 4th instar larvae of the noctuids Helicoverpa armigera (Hübner) and Spodoptera exigua (Hübner) on field beans under both laboratory and greenhouse conditions. The maximum mortality of 58 and 27 % was obtained in Bta + NA treatments in case of 2nd and 4th instar larvae of H. armigera under laboratory conditions followed by Bta (50 and 14 %) and NA (34 and 7 %) alone treatments. Under greenhouse conditions a mortality of 69 and 26 % was observed in case of Bta + NA treatments in 2nd and 4th instar larvae of H. armigera followed by Bta (67 and 20 %) and NA (56 and 10 %) alone. The mortality of H. armigera larvae was higher under greenhouse conditions. There was a significant difference in the mortality between 2nd and 4th instar larvae both under laboratory and greenhouse conditions. The mortality of H. armigera was higher in 2nd instar than in the 4th instar larvae in all treatments. Similar results were obtained in case of S. exigua both under laboratory and greenhouse conditions. The results indicate that Bta and NA have the potential to the control of H. armigera and S. exigua either independently or in combination, when used at the right stage of the field populations. The uassia-extracts tested did not show a high efficacy against larvae of H. armigera and S. exigua.
Die Nonne gehört zu den Kieferngroßschädlingen des norddeutschen Tieflandes. Bei Gradationen werden bisher zur Verhinderung bestandesbedrohender Fraßschäden großflächig Insektizide eingesetzt. Nach bisherigen Beobachtungen dauern Gradationen dieser Art in mitteleuropäischen Kiefernbestockungen meist nur 2 Vegetationsperioden. Als Ursachen für den Zusammenbruch einer Gradation werden Nahrungsmangel sowie der Ausbruch von Krankheiten genannt (WELLENSTEIN &. SCHWENKE 1978). Für das Überleben der Kiefern und damit den Erhalt der Bestände ist entscheidend, dass die jeweiligen Maitriebnadeln und Knospenanlagen vom Fraß der Larven verschont bleiben. Somit ist der Zeitpunkt des Zusammenbruchs der Gradation vor, während oder nach der Konsumption der neuen Nadeln im 2. Gradationsjahr für das Überleben der Wirtspflanze entscheidend. Das Ziel dieser Untersuchung war die Beschreibung möglicher Wechselwirkungen zwischen der Entnadelung der Kiefer im 1. und 2. Jahr des Fraßes und der Larvalentwicklung der Nonnen-Population.
Stechmücken der Art Stegomyia aegypti (ehemals Aedes aegypti, REINERT et al. 2004) sind die wichtigsten Überträger von Gelbfieber- und Dengueviren. Diverse Arten der Gattung Anopheles verbreiten die Erreger der Malaria. Bei Versuchen, Malaria, Gelbfieber und Dengue einzudämmen, wurden in den letzten Jahrzehnten wiederholt Kampagnen gegen Stechmücken geführt. Dabei wurden Insektizide vielfach flächendeckend ausgebracht. Dies führte kurzfristig zu geringeren Mückendichten, allerdings entwickelten sich auch vielerorts gegen diese Gifte resistente Mückenpopulationen. Anstelle des flächendeckenden Gifteinsatzes wird heute versucht, die Insektizide örtlich und zeitlich effektiv einzusetzen, um so die Gefahr weiterer Resistenzbildung zu minimieren und sowohl die Kosten als auch die Belastung für Umwelt und Bevölkerung möglichst gering zu halten. Um Insektizide zur richtigen Zeit gezielt ausbringen zu können, ist ein Monitoring der Mücken erforderlich. Mückenfallen, die durch optische Effekte und Duftstoffe gezielt anthropophile Stechmückenarten anlocken, sind für ein derartiges Bestandsmonitoring besonders geeignet. Auf der Suche nach attraktiven Duftstoffen, welche die Effektivität solcher Fallen erhöhen, wurde unter anderem auch 2-Undecanon getestet. In Verhaltensversuchen mit den anthropophilen Mückenarten Stegomyia aegypti und Anopheles stephensi konnte die Attraktivität dieser Substanz sowohl als Einzelreiz als auch in Kombination mit anderen Attraktanzien gezeigt und quantifiziert werden.
Mittelasien (Kasachstan, Kirgistan, Tadschikistan, Turkmenistan, Usbekistan) ist neben dem Mediterranraum das bedeutendste paläarkische Bienen-Diversitätszentrum (MICHENER 1979). POPOV (1957) schätzt für den Raum 1.200 Arten aus 70 Gattungen, die Gesamtzahl dürfte jedoch bei über 2.000 Arten liegen. Über die innere biogeographische Gliederung der Region und die Lage von Endemiezentren ist bei den Bienen jedoch kaum etwas bekannt (POPOV 1958, MARIKOVSKAYA 1999). Am Beispiel der Seidenbienengattung Colletes, die hier aufgrund ihres Artenreichtums sowie des breiten Spektrums besiedelter Lebensraumtypen und Klimagebiete repräsentativ für andere Bienengruppen behandelt wird, werden Verbreitungsbilder analysiert und Endemiezentren identifiziert. Faunistisches und biogeographisches Arbeiten in Mittelasien ist bis heute ein aufwändiges Unternehmen. Die Größe des Raumes – mit 4 Mio. km² fast halb so groß wie Europa –, die in vielen Regionen unterentwickelte Infrastruktur sowie die in vergangenen und gegenwärtigen bürokratischen Hemmnissen begründete schwierige Zugänglichkeit vieler Gebiete ist ursächlich für den unzureichenden Bearbeitungsstand vieler Taxa. Durch uneinheitliche Transliteration, Schreibfehler bei der Etikettierung und Umbenennung von Orten ist die Identifikation von Fundorten häufig schwierig und in einigen Fällen selbst unter Zuhilfenahme historischen Kartenmaterials unmöglich. Die begrenzte Verfügbarkeit lokalfaunistischer Literatur in deutschen Bibliotheken und die Sprachbarriere bei der Nutzung kyrillisch geschriebener Arbeiten sind ein weiteres Hindernis. Aufgrund dieser Schwierigkeiten und dem daraus resultierenden niedrigen Erfassungsgrad in weiten Teilen Mittelasien haben die hier vorgelegten Ergebnisse vorläufigen Charakter.
Anfang der 80er Jahre wurde zum ersten Mal von SIMOVA-TOSIC & FILEV (1985) in der Nähe des Ohrid Sees (Balkan) eine unbekannte Miniermotte bei einem Massenauftretten an Aesculus hippocastanum L. festgestellt. Die neue Art wurde von DESCHKA & DIMIC (1986) Cameraria ohridella genannt. Seit dieser Erstentdeckung der Motte am Balkan lässt sich eine rasche Ausbreitung des Schädlings in Europa beobachten. Aufgrund der inzwischen erfolgten zahlreichen Veröffentlichungen ist davon auszugehen, dass bis jetzt nahezu ganz Europa, ausgenommen Skandinavien, von der Motte besiedelt wurde. In Griechenland wurde die Motte 1996 von SKUHRAVY (1999) bei Florina (Nord Griechenland) erstmals festgestellt. Ziel der vorliegenden Arbeit war, Erkenntnisse über die Biologie der Motte in Griechenland zu gewinnen. Die durchgeführten Untersuchungen beziehen sich auf die Jahre 2001 bis 2004 und wurden im Rahmen des E.U. Programms CONTROCAM durchgeführt.
Seit 2001 wird in Belgien, Luxemburg und Rheinland-Pfalz der Befall augenscheinlich vitaler Buchen durch den Laubnutzholzborkenkäfer Trypodendron domesticum L. beobachtet (EISENBARTH et al. 2001). Die befallenen Bäume sind voll belaubt und weisen keine erkennbaren äußeren Verletzungen auf. Allerdings muss, entsprechend den bisherigen Erkenntnissen zur Brutraumfindung der Art (KERCK 1971, RAMISCH 1984), von einer individuellen Disposition der betroffenen Buchen ausgegangen werden. Die einzelbaum- bis gruppenweise Verteilung der befallenen Bäume innerhalb der Bestände stützt diese Vermutung. Die Bäume zeigen nicht die typischen Symptome der Buchenrindennekrose, deren erneutes Auftreten seit 1999 in der Region beobachtet wird. Das zeitlich und räumlich parallele Auftreten beider Krankheitsbilder macht einen Zusammenhang allerdings wahrscheinlich. Die Buchen werden vornehmlich an den nordexponierten Stammseiten im unteren Stammdrittel befallen. Der Befall ist in der Regel auf kleinflächige Stammpartien (< 1 m² Mantelfläche) beschränkt. Dieser Stehendbefall, durch die als Lagerholzschädling bekannte Art, ist ein grundlegend neues Schadbild, das bisher noch nicht beobachtet wurde. Die erfolgreiche Besiedlung vitaler Buchen durch pilzzüchtende Borkenkäfer wäre eine ernstzunehmende Gefahr für die mitteleuropäische Buchenwirtschaft und die Buchenwaldökosysteme.
Am Zoologischen Institut der Uni Heidelberg wurde bereits seit einigen Jahren an der Entwicklung einer biologischen Bekämpfungsstrategie gegen Maikäfer gearbeitet. Neben einem Bacillus thuringiensis-Stamm, der bei einigen Maikäfer-Verwandten wirksam ist (WAGNER & SCHNETTER 2001), wurde vor allem mit entomopathogenen Nematoden der Gattungen Steinernema und Heterorhabditis geforscht (BERNER & SCHNETTER 2001). Die Anfälligkeit der Larven sowohl des Feld- als auch des Waldmaikäfers gegenüber diesen Nematoden ist jedoch im Vergleich zu anderen Scarabaeiden, wie dem Gartenlaubkäfer (Phylloperta horticola), relativ gering (SULISTYANTO & EHLERS 1996), so dass auch die bisher durchgeführten Freilandversuche wenig Erfolg brachten (BERNER & SCHNETTER 2002). Neben der Suche nach möglichst infektiösen Nematodenarten und -stämmen ist für den Erfolg einer Nematodenapplikation im Freiland eine vorausgehende Systemanalyse des Standortes von entscheidender Bedeutung. Hierbei sind neben abiotischen Faktoren wie der Witterung und den Bodenverhältnissen auch biotische Faktoren wie dem Vorkommen von Pathogenen in der Engerling-Population zu erfassen. Insbesondere eine Vorinfektion der Engerling-Population kann einen falschen Wirkungsgrad der Nematoden vortäuschen, da unter diesen Bedingungen antagonistische oder synergistische Wechselwirkungen zwischen den latenten Pathogenen und den applizierten Nematoden zu erwarten sind. Ausgangspunkt der hier vorgestellten Arbeit war eine Engerling-Population des Waldmaikäfers (Melolontha hippocastani), die 1999 in der Nähe von Lorsch gefunden wurde und einen hohen Prozentsatz an Engerlingen aufwies, der mit Rickettsien (Rickettsiella popilliae) infiziert war. Aufgrund der hohen Dichte und der ausgeprägten Symptome der als „Lorscher Seuche“ bei Engerlingen bekannten Rickettsien-Infektion konnte die Krankheit bereits im Feld diagnostiziert werden (vgl. NIKLAS 1960).
Natürlicherweise war die Tanne (Abies alba) in den bayerischen Wäldern mit Anteilen von bis zu 20% vertreten (nach ROTHE & BORCHERT 2003). Seit 150 Jahren aber gehen die Tannenbestände in drastischem Ausmaß zurück, was nicht nur auf die wachsende Schadstoffbelastung der Luft, sondern auch auf hohe Wildbestände und die einseitige Waldbewirtschaftung zugunsten der Fichte (Picea abies) zurückzuführen ist. In jüngster Zeit wird seitens der Staatsforstverwaltung angestrebt, der Tanne ihren angestammten Platz in unseren Wäldern wieder einzuräumen (BAYERISCHES STAATSMINISTERIUM FÜR LANDWIRTSCHAFT UND FORSTEN 1993). Es stellt sich die Frage, welchen Beitrag die Tanne zur Biodiversität in Wäldern und speziell in Mischwäldern leistet. Frühere Untersuchungen beschrieben die Tannenfauna als artenarm im Vergleich mit anderen Baumarten (BÖHME 2001, BUCKING 1998), allerdings wurde die Kronenfauna dabei stets vernachlässigt. Da aber 90% eines Hochwaldes über der Reichhöhe eines Menschen liegt (BUßLER et al. 2004), sind Untersuchungen im Kronenraum höheren Straten für eine umfassende Aussage über die Fauna auf Bäumen von großer Bedeutung. Bis jetzt gibt es trotz des generell wachsenden Interesses an der Kronenfauna keine umfassenden Untersuchungen an Tanne (MÜLLER & GOSSNER 2004). Mit dem hier vorgestellten Projekt sollte begonnen werden, die Wissenslücke um die Insektenfauna in Tannenkronen zu schließen. Den xylobionten Käfern galt besondere Aufmerksamkeit, da sie als eine baumartengebundene Insektengruppe für vergleichendeUntersuchungen sehr gut geeignet und sowohl taxonomisch als auch ökologisch gut untersucht sind. Daneben wurden Heteroptera, Neuropterida und Hymenoptera bearbeitet .
Background Over the past years a variety of host restriction genes have been identified in human and mammals that modulate retrovirus infectivity, replication, assembly, and/or cross-species transmission. Among these host-encoded restriction factors, the APOBEC3 (A3; apolipoprotein B mRNA-editing catalytic polypeptide 3) proteins are potent inhibitors of retroviruses and retrotransposons. While primates encode seven of these genes (A3A to A3H), rodents carry only a single A3 gene. Results Here we identified and characterized several A3 genes in the genome of domestic cat (Felis catus) by analyzing the genomic A3 locus. The cat genome presents one A3H gene and three very similar A3C genes (a-c), probably generated after two consecutive gene duplications. In addition to these four one-domain A3 proteins, a fifth A3, designated A3CH, is expressed by read-through alternative splicing. Specific feline A3 proteins selectively inactivated only defined genera of feline retroviruses: Bet-deficient feline foamy virus was mainly inactivated by feA3Ca, feA3Cb, and feA3Cc, while feA3H and feA3CH were only weakly active. The infectivity of Vif-deficient feline immunodeficiency virus and feline leukemia virus was reduced only by feA3H and feA3CH, but not by any of the feA3Cs. Within Felidae, A3C sequences show significant adaptive selection, but unexpectedly, the A3H sequences present more sites that are under purifying selection. Conclusion Our data support a complex evolutionary history of expansion, divergence, selection and individual extinction of antiviral A3 genes that parallels the early evolution of Placentalia, becoming more intricate in taxa in which the arms race between host and retroviruses is harsher.
Manche mögen’s salzig : Anpassungsstrategien und Biotechnologie Salz liebender Mikroorganismen
(2008)
Sie lieben extreme Bedingungen: Einige leben in tiefen Gesteinsschichten oder ohne Licht und Sauerstoff an kochend heißen Quellen der Tiefsee, andere bevorzugen die eisigen Temperaturen der Polargebiete, und wieder andere fühlen sich erst richtig wohl in kochender Schwefelsäure. Doch wie passen sich Mikroorganismen an diese extremen Bedingungen an? Die Forschung hat darauf bereits Antworten gefunden, die sich auch biotechnologisch nutzen lassen.
Ohne das Eingreifen des Menschen wäre Mitteleuropa fast ein reines Waldgebiet. Noch heute beheimaten die Wälder eine große Vielfalt an Pflanzen und Tieren, die für diese Region spezifisch sind. Regionale Besonderheiten gehen aber verloren, je mehr Menschen in die Ökosysteme eingreifen: So unterscheiden sich die Pflanzenarten auf der North Charles Street in Baltimore nur wenig von denjenigen der Mainzer Landstraße in Frankfurt. Gleichzeitig verdrängen zugewanderte und eingeschleppte Arten heimische Tiere und Pflanzen. Allerdings gibt es auch im Frankfurter Stadtgebiet echte Horte der Biodiversität.
From sea to land and beyond : new insights into the evolution of euthyneuran Gastropoda (Mollusca)
(2008)
Background The Euthyneura are considered to be the most successful and diverse group of Gastropoda. Phylogenetically, they are riven with controversy. Previous morphology-based phylogenetic studies have been greatly hampered by rampant parallelism in morphological characters or by incomplete taxon sampling. Based on sequences of nuclear 18S rRNA and 28S rRNA as well as mitochondrial 16S rRNA and COI DNA from 56 taxa, we reconstructed the phylogeny of Euthyneura utilising Maximum Likelihood and Bayesian inference methods. The evolution of colonization of freshwater and terrestrial habitats by pulmonate Euthyneura, considered crucial in the evolution of this group of Gastropoda, is reconstructed with Bayesian approaches. Results We found several well supported clades within Euthyneura, however, we could not confirm the traditional classification, since Pulmonata are paraphyletic and Opistobranchia are either polyphyletic or paraphyletic with several clades clearly distinguishable. Sacoglossa appear separately from the rest of the Opisthobranchia as sister taxon to basal Pulmonata. Within Pulmonata, Basommatophora are paraphyletic and Hygrophila and Eupulmonata form monophyletic clades. Pyramidelloidea are placed within Euthyneura rendering the Euthyneura paraphyletic. Conclusion Based on the current phylogeny, it can be proposed for the first time that invasion of freshwater by Pulmonata is a unique evolutionary event and has taken place directly from the marine environment via an aquatic pathway. The origin of colonisation of terrestrial habitats is seeded in marginal zones and has probably occurred via estuaries or semi-terrestrial habitats such as mangroves.
Poster presentation In pharmaceutical research and drug development, machine learning methods play an important role in virtual screening and ADME/Tox prediction. For the application of such methods, a formal measure of similarity between molecules is essential. Such a measure, in turn, depends on the underlying molecular representation. Input samples have traditionally been modeled as vectors. Consequently, molecules are represented to machine learning algorithms in a vectorized form using molecular descriptors. While this approach is straightforward, it has its shortcomings. Amongst others, the interpretation of the learned model can be difficult, e.g. when using fingerprints or hashing. Structured representations of the input constitute an alternative to vector based representations, a trend in machine learning over the last years. For molecules, there is a rich choice of such representations. Popular examples include the molecular graph, molecular shape and the electrostatic field. We have developed a molecular similarity measure defined directly on the (annotated) molecular graph, a long-standing established topological model for molecules. It is based on the concepts of optimal atom assignments and iterative graph similarity. In the latter, two atoms are considered similar if their neighbors are similar. This recursive definition leads to a non-linear system of equations. We show how to iteratively solve these equations and give bounds on the computational complexity of the procedure. Advantages of our similarity measure include interpretability (atoms of two molecules are assigned to each other, each pair with a score expressing local similarity; this can be visualized to show similar regions of two molecules and the degree of their similarity) and the possibility to introduce knowledge about the target where available. We retrospectively tested our similarity measure using support vector machines for virtual screening on several pharmaceutical and toxicological datasets, with encouraging results. Prospective studies are under way.
Background Differential expression of genes can be regulated on many different levels. Most global studies of gene regulation concentrate on transcript level regulation, and very few global analyses of differential translational efficiencies exist. The studies have revealed that in Saccharomyces cerevisiae, Arabidopsis thaliana, and human cell lines translational regulation plays a significant role. Additional species have not been investigated yet. Particularly, until now no global study of translational control with any prokaryotic species was available. Results A global analysis of translational control was performed with two haloarchaeal model species, Halobacterium salinarum and Haloferax volcanii. To identify differentially regulated genes, exponentially growing and stationary phase cells were compared. More than 20% of H. salinarum transcripts are translated with non-average efficiencies. By far the largest group is comprised of genes that are translated with above-average efficiency specifically in exponential phase, including genes for many ribosomal proteins, RNA polymerase subunits, enzymes, and chemotaxis proteins. Translation of 1% of all genes is specifically repressed in either of the two growth phases. For comparison, DNA microarrays were also used to identify differential transcriptional regulation in H. salinarum, and 17% of all genes were found to have non-average transcript levels in exponential versus stationary phase. In H. volcanii, 12% of all genes are translated with non-average efficiencies. The overlap with H. salinarum is negligible. In contrast to H. salinarum, 4.6% of genes have non-average translational efficiency in both growth phases, and thus they might be regulated by other stimuli than growth phase. Conclusions For the first time in any prokaryotic species it was shown that a significant fraction of genes is under differential translational control. Groups of genes with different regulatory patterns were discovered. However, neither the fractions nor the identity of regulated genes are conserved between H. salinarum and H. volcanii, indicating that prokaryotes as well as eukaryotes use differential translational control for the regulation of gene expression, but that the identity of regulated genes is not conserved For 70 H. salinarum genes potentiation of regulation was observed, but for the majority of regulated genes either transcriptional or translational regulation is employed.
Background The phylogenetic tree of Galliformes (gamebirds, including megapodes, currassows, guinea fowl, New and Old World quails, chicken, pheasants, grouse, and turkeys) has been considerably remodeled over the last decades as new data and analytical methods became available. Analyzing presence/absence patterns of retroposed elements avoids the problems of homoplastic characters inherent in other methodologies. In gamebirds, chicken repeats 1 (CR1) are the most prevalent retroposed elements, but little is known about the activity of their various subtypes over time. Ascertaining the fixation patterns of CR1 elements would help unravel the phylogeny of gamebirds and other poorly resolved avian clades. Results We analyzed 1,978 nested CR1 elements and developed a multidimensional approach taking advantage of their transposition in transposition character (TinT) to characterize the fixation patterns of all 22 known chicken CR1 subtypes. The presence/absence patterns of those elements that were active at different periods of gamebird evolution provided evidence for a clade (Cracidae + (Numididae + (Odontophoridae + Phasianidae))) not including Megapodiidae; and for Rollulus as the sister taxon of the other analyzed Phasianidae. Genomic trace sequences of the turkey genome further demonstrated that the endangered African Congo Peafowl (Afropavo congensis) is the sister taxon of the Asian Peafowl (Pavo), rejecting other predominantly morphology-based groupings, and that phasianids are monophyletic, including the sister taxa Tetraoninae and Meleagridinae. Conclusions The TinT information concerning relative fixation times of CR1 subtypes enabled us to efficiently investigate gamebird phylogeny and to reconstruct an unambiguous tree topology. This method should provide a useful tool for investigations in other taxonomic groups as well.
Background Today it is widely accepted that plastids are of cyanobacterial origin. During their evolutionary integration into the metabolic and regulatory networks of the host cell the engulfed cyanobacteria lost their independency. This process was paralleled by a massive gene transfer from symbiont to the host nucleus challenging the development of a retrograde protein translocation system to ensure plastid functionality. Such a system includes specific targeting signals of the proteins needed for the function of the plastid and membrane-bound machineries performing the transfer of these proteins across the envelope membranes. At present, most informations on protein translocation are obtained by the analysis of land plants. However, the analysis of protein import into the primitive plastids of glaucocystophyte algae, revealed distinct features placing this system as a tool to understand the evolutionary development of translocation systems. Here, bacterial outer membrane proteins of the Omp85 family have recently been discussed as evolutionary seeds for the development of translocation systems. Results To further explore the initial mode of protein translocation, the observed phenylalanine dependence for protein translocation into glaucophyte plastids was pursued in detail. We document that indeed the phenylalanine has an impact on both, lipid binding and binding to proteoliposomes hosting an Omp85 homologue. Comparison to established import experiments, however, unveiled a major importance of the phenylalanine for recognition by Omp85. This finding is placed into the context of the evolutionary development of the plastid translocon. Conclusion The phenylalanine in the N-terminal domain signs as a prerequisite for protein translocation across the outer membrane assisted by a primitive translocon. This amino acid appears to be optimized for specifically targeting the Omp85 protein without enforcing aggregation on the membrane surface. The phenylalanine has subsequently been lost in the transit sequence, but can be found at the C-terminal position of the translocating pore. Thereby, the current hypothesis of Omp85 being the prokaryotic contribution to the ancestral Toc translocon can be supported.
Rezensionen zu: Thomas Junker : Die Evolution des Menschen. Verlag C. H. Beck, München 2006 ISBN 978-3-406-53609-0, 127 Seiten, 7,90 Euro. Guillaume Lecointre, Hervé Le Guyader : Biosystematik. Verlag Springer, Heidelberg 2006. ISBN 978-3-540-24037-2. 696 Seiten, 39,95 Euro. Ulrich Kutschera : Evolutionsbiologie. 2. Auflage, Verlag Eugen Ulmer, Stuttgart 2006. ISBN 978-3-8252-8318-6 303 Seiten, 39,90 Euro. Volker Knoop, Kai Müller : Gene und Stammbäume. Verlag Elsevier/Spektrum, München 2006 ISBN 978-3-8274-1642-1. 310 Seiten, 29,50 Euro.
Die Paläoanthropologie beschäftigt sich mit der Erforschung der Ursprünge und der Evolution des Menschen. Die Vermittlung dieser Forschungsergebnisse in deutschen Schulen stellt eine wichtige Aufgabe dar und ist curricularer Bestandteil der Sekundarstufe I und II. Ein zentrales Anliegen des »Hominids for Schools«-Projekts ist es, die Vermittlung dieses Wissens nicht nur in Deutschland zu fördern, sondern auch dort, wo die Menschheitsgeschichte begann – in Afrika, der Wiege der Menschheit. Doch ein Schädelabguss allein bereichert noch nicht den Biologie- oder Evolutionsunterricht. Gefragt sind fachdidaktische Konzepte, die Schülern die neuesten Forschungsergebnisse inhaltlich näher bringen und buchstäblich begreifbar machen. An dieser Stelle ist die Kooperation zwischen Fachwissenschaft und Fachdidaktik unverzichtbar. Der vom Forschungsinstitut Senckenberg und dem Institut für Didaktik der Biowissenschaften gemeinsam entwickelte Lernkoffer ist ein Beispiel für fruchtbare Entwicklungsforschung, die zu den grundlegenden Aufgaben einer inhaltsorientierten Fachdidaktik gehört. Ausgangspunkt für das »Hominids for Schools«-Projekt war die Idee des Paläoanthropologen Prof. Dr. Friedemann Schrenk vom Forschungsinstitut Senckenberg, die Bildung in Afrika zu fördern und einen interkulturellen Dialog zwischen deutschen und afrikanischen Partnerschulen anzuregen. Als Basis dienen Fossilien von Hominiden, die zu den ältesten Vorfahren des heutigen Menschen gezählt werden, und zwar Nachbildungen eines Schädels und eines Unterkiefers. Der Schädel gehört zu dem in Kenia gefundenen Turkana Boy, einem Homo erectus. Der Unterkiefer ist einem Homo rudolfensis zuzuordnen. Er stammt aus Malawi und stellt mit einem Alter von 2,5 Millionen Jahren das älteste Fundstück der Gattung Homo dar: UR 501 – so die Katalognummer des fossilen Urahns [siehe auch Stefanie Müller »Wissenschaftsvermittlung in der Wiede der Menschheit«, Forschung Frankfurt 2 – 3/2006]. Friedemann Schrenk, der seit über 20 Jahren auf dem afrikanischen Kontinent nach den Überresten unserer Vorfahren gräbt, fand mit seinem Team 1992 den Unterkiefer in Malawi. Der von Schrenk gegründete Verein »Uraha Foundation Germany « setzt sich für die Förderung von Wissenschaft und Forschung in und über Afrika ein. Im Rahmen des »Hominids for Schools«-Programms können deutsche Schulen über den Erwerb von Abgüssen zusätzliche Kopien für afrikanische Partnerschulen mitfinanzieren. In dem Beitrag von 150 Euro für einen Abguss des Unterkiefers von UR 501 sowie 350 Euro für den Abguss des Schädels des Turkana Boy ist die kostenlose Lieferung weiterer Abgüsse an zwei afrikanische Partnerschulen enthalten. Diese verfügen aufgrund eingeschränkter finanzieller Mittel nicht über die Möglichkeit, das Material selbst zu erwerben. Gerade die Lehr- und Lernmaterialausstattung ist an vielen afrikanischen Schulen, besonders in ländlichen Gebieten, mehr schlecht als recht. ...
Die vorliegende Untersuchung wurde im Rahmen des Verbundprojekts „BIOTA West Afrika“ durchgeführt und befasst sich mit der raum/zeitlichen Analyse der Landbedeckung und der räumlichen Modellierung von Mustern der Pflanzenvielfalt in drei Untersuchungsgebieten in Burkina Faso und Benin. Der erste Teil der Untersuchung beinhaltet die Dokumentation und Analyse der Landbedeckung und Landnutzung und ihrer raum/zeitlichen Veränderungen entlang eines Klimagradienten vom ariden Norden Burkina Fasos bis in den semiariden Norden Benins. Auf der Basis von multitemporalen LANDSAT - Satellitendaten und umfangreichen Geländedaten werden im sahelischen und den sudanischen Untersuchungsgebieten Karten der Landbedeckung mit hoher räumlicher und thematischer Auflösung erstellt. Je nach Untersuchungsgebiet können zwischen zehn und fünfzehn Landbedeckungsklassen differenziert werden. Die Gesamtklassifikationsgüte erreicht Werte zwischen 74% und 87%. In den sudanischen Untersuchungsgebieten werden Landnutzungsveränderungen mit Hilfe von LANDSAT - Satellitendaten, Luftbildern und Geländedaten über einen Zeitraum von ca. 15 Jahren (1986 – 2001) dokumentiert. Für beide Untersuchungsgebiete werden gravierende Landnutzungsveränderungen festgestellt. Der Anteil der ackerbaulich genutzten Fläche steigt für das nordsudanische Untersuchungsgebiet von 17% auf 41% und für das südsudanische Untersuchungsgebiet von 10% auf 14%. Im Mittelpunkt des zweiten Teils dieser Untersuchung steht die Frage nach den räumlichen Mustern der Pflanzenvielfalt und ihrer zeitlichen Veränderungen in den Untersuchungsgebieten der Sahel-, der Nord- und Südsudanzone. Zur Bearbeitung dieser Aufgabenstellungen kommt ein breites Methodenspektrum zur Anwendung. Kernstück der Untersuchung ist die Entwicklung eines verbesserten methodischen Ansatzes der Biodiversitätsmodellierung. Dazu werden bereits existierende räumliche Modellierungsansätze durch die Einbindung von Satellitendaten weiterentwickelt. Auf der Basis von georeferenzierten botanischen Daten (aktuell über 4500 pflanzensoziologische Aufnahmen mit insgesamt 104000 Datensätzen) werden für das sahelische, nord- und südsudanische Untersuchungsgebiet modellierte Verbreitungskarten von 138, 123 und 165 Pflanzenarten erstellt. Die Güte der Karten wird auf der Basis von unabhängigen Geländedaten überprüft. Die einzelnen Verbreitungskarten werden gebietsweise zusammengefasst, so dass im Ergebnis für jedes Untersuchungsgebiet eine hochauflösende Karte der Pflanzenvielfalt vorliegt. Im Rahmen einer Fallstudie werden die zeitlichen Veränderungen der Verbreitungsgebiete von Nutzbaumarten über einen Zeitraum von 13 Jahren untersucht. Es werden aktuelle und historische Verbreitungsgebiete der Nutzbaumarten auf der Basis von hochauflösenden Satellitendaten modelliert und die Veränderungen der Verbreitungsgebiete vor dem Hintergrund des Landnutzungswandels im Untersuchungsgebiet analysiert. Für 17 der 18 untersuchten Baumarten werden rückgängige Verbreitungsgebiete beobachtet.
In den hoch entwickelten Industriestaaten wird seit längerem eine dramatische Veränderung der Bevölkerungsstruktur beobachtet. Bei einer Erhöhung der Lebenserwartung und einer gleichzeitigen Abnahme der Geburtenrate verschiebt sich das Verhältnis von jungen zu alten Individuen immer mehr hin zu den Älteren. Längst wird von einem »Ergrauen« oder gar einer »Vergreisung« Europas gesprochen. Hieraus ergeben sich bereits heute schwerwiegende Probleme für die bestehenden Sozial- und Gesundheitssysteme. Diese drohen sich in der Zukunft dramatisch zu verschärfen. Eine Entlastung wird sicher nur dann erreicht werden können, wenn es gelingt, das Auftreten gesundheitlicher Beeinträchtigungen und Erkrankungen nachhaltig zu verhindern oder zumindest zu verzögern und damit eine Verbesserung der Lebensqualität in fortgeschrittenen Lebensabschnitten zu gewährleisten. Entscheidende Voraussetzung zum Erreichen dieser Ziele ist ein grundlegendes Verständnis der Mechanismen biologischen Alterns.
Ob das Alter ein Segen oder ein Fluch ist, darüber gehen seit der Antike die Meinungen auseinander, und es hat nicht an Versuchen gefehlt, für die doch unleugbaren Gebrechen und Gebresten die Gegenrechnung aufzumachen. Auf der einen Seite also Verfall des Körpers, Krankheit, Nachlassen oder Absterben der Sinnesvermögen und des fleischlichen Begehrens, auf der anderen Seite dafür aber Weisheit, Gelassenheit, Gemütsruhe, Abgeklärtheit, Milde, vielleicht Heiterkeit, da nichts mehr erreicht werden will. Prudentia – Klugheit – und Sophrosyne – Beherrschung der Begierden durch Vernunft und Besonnenheit – heißen die altersgemäßen Stichwörter, die vielleicht sogar Handlungsspielräume eröffnen, die den früheren Lebensaltern fehlten. ...
The experience of pain is mediated by a specialized sensory system, the nociceptive system. There is considerable evidence that the cGMP/cGMP kinase I (cGKI) signaling pathway modulates the nociceptive processing within the spinal cord. However, downstream targets of cGKI in this context have not been identified to date. In this study we investigated whether cysteine-rich protein 2 (CRP2) is a downstream effector of cGKI in the spinal cord and is involved in nociceptive processing. Immunohistochemistry of the mouse spinal cord revealed that CRP2 is expressed in superficial laminae of the dorsal horn. CRP2 is colocalized with cGKI and with markers of primary afferent C fibers. Importantly, the majority of CRP2 mRNA-positive dorsal root ganglion (DRG) neurons express cGKI and CRP2 is phosphorylated in a cGMP-dependent manner. To elucidate the functional role of CRP2 in nociception, we investigated the nociceptive behavior of CRP2-deficient (CRP2-/-) mice. Touch perception and acute thermal nociception were unaltered in CRP2-/- mice. However, CRP2-/- mice showed an increased nociceptive behavior in models of persistent pain as compared to wild type mice. Intrathecal administration of cGKI activating cGMP analogs increased the nociceptive behavior in wild type but not in CRP2-/- mice, indicating that the presence of CRP2 was essential for cGMP/cGKI-mediated nociception. These data indicate that CRP2 is a new downstream effector of cGKI-mediated spinal nociceptive processing and point to an inhibitory role of CRP2 in the generation of inflammatory pain.
cGMP- and cAMP-dependent protein kinases (cGK and cAK) mediate the inhibitory effects of endothelium-derived messenger molecules nitric oxide and prostacyclin on platelets. To understand the mechanisms involved in platelet inhibition we searched for new substrates of cGK and cAK. We identified Rap1GAP2, the only GTPase-activating protein of Rap1 in platelets. Rap1 is a guanine-nucleotide binding protein that controls integrin activity, platelet adhesion and aggregation. Rap1GAP2 is required to turn over Rap1-GTP to Rap1-GDP resulting in the inactivation of integrins and reduced cellular adhesion. Using phospho-specific antibodies we demonstrate phosphorylation of endogenous Rap1GAP2 on serine 7 by cGK and cAK in intact platelets. Yeast-two-hybrid screening revealed an interaction of the phosphoserine/-threonine binding adapter protein 14-3-3 with Rap1GAP2, and we mapped the 14-3-3 binding site to the N-terminus of Rap1GAP2 close to the cGK/cAK phosphorylation site. We could show that 14-3-3 binding to Rap1GAP2 requires phosphorylation of serine 9. Platelet activation by ADP and thrombin treatment induces Rap1GAP2 serine 9 phosphorylation and enhances the attachment of 14-3-3 to Rap1GAP2. In contrast, phosphorylation of serine 7 by cGK/cAK leads to the detachment of 14-3-3. Furthermore, Rap1GAP2 serine 7 phosphorylation correlates with the inhibition of Rap1-GTP formation by cGMP and cAMP in platelets. Cell adhesion experiments provide additional evidence that Rap1GAP2 is activated by the detachment of 14-3-3. Point mutants of Rap1GAP2 deficient in 14-3-3 binding inhibit Rap1-mediated cell adhesion significantly stronger than a Rap1GAP2 mutant that binds 14-3-3 constitutively. Our findings define a novel regulatory mechanism that might contribute to both platelet activation and endothelial inhibition of platelet adhesion and aggregation.
Oxidative stress attenuates the NO-cGMP pathway, e.g. in the vascular system, through scavenging of free NO radicals by superoxide O2•-, by inactivation of soluble guanylyl cyclase (sGC) via oxidation of its central Fe2+ ion, and by down-regulation of sGC protein levels. While the former pathways are well established, the molecular mechanisms underlying the latter are still obscure. Using oxidative sGC inhibitor ODQ we demonstrate rapid down-regulation of sGC protein in mammalian cells. Co-incubation with proteasomal inhibitor MG132 results in accumulation of ubiquitinated sGC whereas sGC activator BAY 58–2667 prevents ubiquitination. ODQ-induced down-regulation of sGC is mediated through selective ubiquitination of its b subunit, and BAY 58–2667 abrogates this effect. Ubiquitination of sGC-b is dramatically enhanced by E3 ligase CHIP. Our data indicate that oxidative stress promotes ubiquitination of sGC b subunit through E3 ligase CHIP, and that sGC activator 58–2667 reverts this effect, most likely through stabilization of the heme-free b subunit. Thus the deleterious effects of oxidative stress can be counter-balanced by an activator of a key enzyme of vascular homeostasis.
Bypassing of DNA lesions by damage-tolerant DNA polymerases depends on the interaction of these enzymes with the monoubiquitylated form of the replicative clamp protein, PCNA. We have analyzed the contributions of ubiquitin and PCNA binding to damage bypass and damage-induced mutagenesis in Polymerase {eta} (encoded by RAD30) from the budding yeast Saccharomyces cerevisiae. We report here that a ubiquitin-binding domain provides enhanced affinity for the ubiquitylated form of PCNA and is essential for in vivo function of the polymerase, but only in conjunction with a basal affinity for the unmodified clamp, mediated by a conserved PCNA interaction motif. We show that enhancement of the interaction and function in damage tolerance does not depend on the ubiquitin attachment site within PCNA. Like its mammalian homolog, budding yeast Polymerase {eta} itself is ubiquitylated in a manner dependent on its ubiquitin-binding domain.
To facilitate the measurement of intramolecular distances in solvated RNA systems, a combination of spin-labeling, electron paramagnetic resonance (EPR), and molecular dynamics (MD) simulation is presented. The fairly rigid spin label 2,2,5,5-tetramethyl-pyrrolin-1-yloxyl-3-acetylene (TPA) was base and site specifically introduced into RNA through a Sonogashira palladium catalyzed crosscoupling on column. For this purpose 5-iodouridine, 5-iodo-cytidine and 2-iodo-adenosine phosphoramidites were synthesized and incorporated into RNA-sequences. Application of the recently developed ACE (R) chemistry presented the main advantage to limit the reduction of the nitroxide to an amine during the oligonucleotide automated synthesis and thus to increase substantially the reliability of the synthesis and the yield of labeled oligonucleotides. 4-Pulse Electron Double Resonance (PELDOR) was then successfully used to measure the intramolecular spin–spin distances in six doubly labeled RNA-duplexes. Comparison of these results with our previous work on DNA showed that A- and B-Form can be differentiated. Using an all-atom force field with explicit solvent, MD simulations gave results in good agreement with the measured distances and indicated that the RNA A-Form was conserved despite a local destabilization effect of the nitroxide label. The applicability of the method to more complex biological systems is discussed.
Riboswitches are highly structured elements in the 50-untranslated regions (50-UTRs) of messenger RNA that control gene expression by specifically binding to small metabolite molecules. They consist of an aptamer domain responsible for ligand binding and an expression platform. Ligand binding in the aptamer domain leads to conformational changes in the expression platform that result in transcription termination or abolish ribosome binding. The guanine riboswitch binds with high-specificity to guanine and hypoxanthine and is among the smallest riboswitches described so far. The X-ray-structure of its aptamer domain in complex with guanine/ hypoxanthine reveals an intricate RNA-fold consisting of a three-helix junction stabilized by longrange base pairing interactions. We analyzed the conformational transitions of the aptamer domain induced by binding of hypoxanthine using highresolution NMR-spectroscopy in solution. We found that the long-range base pairing interactions are already present in the free RNA and preorganize its global fold. The ligand binding core region is lacking hydrogen bonding interactions and therefore likely to be unstructured in the absence of ligand. Mg2+-ions are not essential for ligand binding and do not change the structure of the RNA-ligand complex but stabilize the structure at elevated temperatures. We identified a mutant RNA where the long-range base pairing interactions are disrupted in the free form of the RNA but form upon ligand binding in an Mg2+-dependent fashion. The tertiary interaction motif is stable outside the riboswitch context.
Background Cryptic species are two or more distinct but morphologically similar species that were classified as a single species. During the past two decades we observed an exponential growth of publications on cryptic species. Recently published reviews have demonstrated cryptic species have profound consequences on many biological disciplines. It has been proposed that their distribution is non-random across taxa and biomes. Results We analysed a literature database for the taxonomic and biogeographical distribution of cryptic animal species reports. Results from regression analysis indicate that cryptic species are almost evenly distributed among major metazoan taxa and biogeographical regions when corrected for species richness and study intensity. Conclusion This indicates that morphological stasis represents an evolutionary constant and that cryptic metazoan diversity does predictably affect estimates of earth´s animal diversity. Our findings have direct theoretical and practical consequences for a number of prevailing biological questions with regard to global biodiversity estimates, conservation efforts and global taxonomic initiatives.
Infektionen mit Herpesviren sind bereits seit der Antike bekannt. So beschrieb zum Beispiel schon Hippokrates in seinem »Corpus Hippocraticum« die sich auf der Haut ausbreitenden Herpes Simplex Läsionen und gab der Krankheit ihren bis heute gültigen Namen. Verbürgt ist auch, dass der römische Kaiser Tiberius vor etwa 2000 Jahren während einer auftretenden Herpes labialis-Epidemie das Küssen bei öffentlichen Zeremonien per Dekret verbat. Shakespeare war ebenfalls bestens vertraut mit den periodisch auftretenden Herpes-Bläschen; in seinem Werk »Romeo & Julia« spricht Mercutio zu Romeo: »O’er ladies lips, who straight on kisses dream, which oft the angry Mab with blisters plagues, ….« Doch erst in den 1960er Jahren erkannte man die virale Herkunft der Erkrankung.
Ahnenforschung unter sozialen Amöben : die morphologische Taxonomie muss umgeschrieben werden
(2007)
Seit fast 150 Jahren forschen Wissenschaftler aus aller Welt über den faszinierenden Wechsel zwischen Einzelligkeit und Vielzelligkeit im Lebenszyklus der »zellulären Schleimpilze«. Diese Forschung war bisher so erfolgreich, dass einem Vertreter der zellulären Schleimpilze, Dictyostelium discoideum, vom US-amerikanischen Gesundheitsministerium National Institutes of Health (NIH) ganz offiziell der Status eines Modellorganismus für biomedizinische Forschung verliehen wurde. Obwohl wir inzwischen glauben, viel über die »sozialen Amöben«, die sich bei Nahrungsmangel von Einzellern zu einem vielzelligen Verband zusammenlagern, gelernt zu haben, basiert unser Wissen doch fast ausschließlich auf Arbeiten mit der einen Art D. discoideum. Man kennt allerdings heute mehr als 100 Arten sozialer Amöben. Alle bilden multizelluläre Fruchtkörper aus, die aus Stielen und Sporenpaketen bestehen. Bisher ging man davon aus, dass die Spezies mit azellulären Stielen in ihren Fruchtkörpern phylogenetische Vorläufer der Vertreter mit zellulären Stielen sind, und dass die Vertreter mit verzweigten Fruchtkörpern näher mit sich selbst als mit den anderen sozialen Amöben verwandt sind. Diese Hypothesen wurden nun durch aktuelle molekulargenetische Analysen widerlegt.
Expeditionen ins Pilzreich Panamas : Pionierarbeit in einer der artenreichsten Regionen unserer Erde
(2007)
Als Bindeglied zwischen Nord- und Südamerika ist Panama ein »Biodiversitäts-Hotspot« – es beherbergt eine außerordentlich hohe Artenvielfalt an Pflanzen, Tieren und Pilzen. Pilze übernehmen in tropischen Ökosystemen wichtige Aufgaben: Sie zersetzen totes organisches Material, helfen den Pflanzen bei der Aufnahme von Wasser und Mineralstoffen aus dem Boden, und sie leisten sogar als Parasiten einen Beitrag zum Erhalt einer großen Artenvielfalt. Aufgrund einzelner Stichproben wissen wir, dass die Anzahl der Pilzarten in den Tropen diejenige der Pflanzen um ein Vielfaches übertrifft. Doch während für Panama zirka 9500 verschiedene Arten von Gefäßpflanzen bekannt sind, zählt eine im Rahmen unserer Arbeit erstellte Checkliste der Pilze nur zirka 1800 Arten. Das zeigt, dass für die Erforschung der Pilze noch umfangreiche Pionierarbeit geleistet werden muss. Zwischen 2003 und 2006 geschah dies im Rahmen einer Universitätspartnerschaft der Universität Frankfurt mit der Universidad Autónoma de Chiriquí, die durch den Deutschen Akademischen Austauschdienst (DAAD) gefördert wurde. Im Zentrum eines Projekts der Deutschen Forschungsgemeinschaft (DFG) steht die Erforschung der Vielfalt und Ökologie pflanzenparasitischer Pilze. Des Weiteren untersucht unsere Arbeitsgruppe Pilze an Insekten sowie an menschlichen Haut- und Nagelläsionen.
Background Synchronous neuronal firing has been discussed as a potential neuronal code. For testing first, if synchronous firing exists, second if it is modulated by the behaviour, and third if it is not by chance, a large set of tools has been developed. However, to test whether synchronous neuronal firing is really involved in information processing one needs a direct comparison of the amount of synchronous firing for different factors like experimental or behavioural conditions. To this end we present an extended version of a previously published method NeuroXidence [1], which tests, based on a bi- and multivariate test design, whether the amount of synchronous firing above the chance level is different for different factors.
Background The synchrony hypothesis postulates that precise temporal synchronization of different pools of neurons conveys information that is not contained in their firing rates. The synchrony hypothesis had been supported by experimental findings demonstrating that millisecond precise synchrony of neuronal oscillations across well separated brain regions plays an essential role in visual perception and other higher cognitive tasks [1]. Albeit, more evidence is being accumulated in favour of its role as a binding mechanism of distributed neural responses, the physical and anatomical substrate for such a dynamic and precise synchrony, especially zero-lag even in the presence of non-negligible delays, remains unclear. Here we propose a simple network motif that naturally accounts for zero-lag synchronization for a wide range of temporal delays [3]. We demonstrate that zero-lag synchronization between two distant neurons or neural populations can be achieved by relaying the dynamics via a third mediating single neuron or population. Methods We simulated the dynamics of two Hodgkin-Huxley neurons that interact with each other via an intermediate third neuron. The synaptic coupling was mediated through alpha-functions. Individual temporal delays of the arrival of pre-synaptic potentials were modelled by a gamma distribution. The strength of the synchronization and the phase-difference between each individual pairs were derived by cross-correlation of the membrane potentials. Results In the regular spiking regime the two outer neurons consistently synchronize with zero phase lag irrespective of the initial conditions. This robust zero-lag synchronization naturally arises as a consequence of the relay and redistribution of the dynamics performed by the central neuron. This result is independent on whether the coupling is excitatory or inhibitory and can be maintained for arbitrarily long time delays (see Fig. 1). Conclusion We have presented a simple and extremely robust network motif able to account for the isochronous synchronization of distant neural elements in a natural way. As opposed to other possible mechanisms of neural synchronization, neither inhibitory coupling, gap junctions nor precise tuning of morphological parameters are required to obtain zero-lag synchronized neuronal oscillation.
Background The cell cycle of all organisms includes mass increase by a factor of two, replication of the genetic material, segregation of the genome to different parts of the cell, and cell division into two daughter cells. It is tightly regulated and typically includes cell cycle-specific oscillations of the levels of transcripts, proteins, protein modifications, and signaling molecules. Until now cell cycle-specific transcriptome changes have been described for four eukaryotic species ranging from yeast to human, but only for two prokaryotic species. Similarly, oscillations of small signaling molecules have been identified in very few eukaryotic species, but not in any prokaryote. Results A synchronization procedure for the archaeon Halobacterium salinarum was optimized, so that nearly 100% of all cells divide in a time interval that is 1/4th of the generation time of exponentially growing cells. The method was used to characterize cell cycle-dependent transcriptome changes using a genome-wide DNA microarray. The transcript levels of 87 genes were found to be cell cycle-regulated, corresponding to 3% of all genes. They could be clustered into seven groups with different transcript level profiles. Cluster-specific sequence motifs were detected around the start of the genes that are predicted to be involved in cell cycle-specific transcriptional regulation. Notably, many cell cycle genes that have oscillating transcript levels in eukaryotes are not regulated on the transcriptional level in H. salinarum. Synchronized cultures were also used to identify putative small signaling molecules. H. salinarum was found to contain a basal cAMP concentration of 200 uM, considerably higher than that of yeast. The cAMP concentration is shortly induced directly prior to and after cell division, and thus cAMP probably is an important signal for cell cycle progression. Conclusions The analysis of cell cycle-specific transcriptome changes of H. salinarum allowed to identify a strategy of transcript level regulation that is different from all previously characterized species. The transcript levels of only 3% of all genes are regulated, a fraction that is considerably lower than has been reported for four eukaryotic species (6% - 28%) and for the bacterium C. crescentus (19%). It was shown that cAMP is present in significant concentrations in an archaeon, and the phylogenetic profile of the adenylate cyclase indicates that this signaling molecule is widely distributed in archaea. The occurrence of cell cycle-dependent oscillations of the cAMP concentration in an archaeon and in several eukaryotic species indicates that cAMP level changes might be a phylogenetically old signal for cell cycle progression.
Effects of BPA in snails
(2006)
It is an ethical requirement that new findings be presented in light of and in conjunction with a balanced evaluation of the current knowledge and published literature. We believe that Oehlmann et al. (2006) violated this general principle in several ways. For example, the authors inferred that prosobranch snails have a functional estrogen receptor and therefore a much higher sensitivity to estrogens and endocrine-disrupting compounds (EDCs) than other species previously reported in the literature. We found several other problems in their article...
We welcome critical appraisals that help to provide balance; however, Dietrich et al. gave an unjustified reproach. We feel that Dietrich’s position is severely compromised because he serves as an expert for the bisphenol A (BPA) Industry Group (Brussels, Belgium). We would like to respond to the issues raised by Dietrich et al., as well as to their oversights and inappropriate interpretations of our findings...
There is a growing body of evidence that indicates common environmental pollutants are capable of disrupting reproductive and developmental processes by interfering with the actions of endogenous hormones. Many reports of endocrine disruption describe changes in the normal development of organs and tissues that are consistent with genetic damage, and recent studies confirm that many chemicals classified to have hormone-modulating effects also possess carcinogenic and mutagenic potential. To date, however, there have been no conclusive examples linking genetic damage with perturbation of endocrine function and adverse effects in vivo. Here, we provide the first evidence of DNA damage associated with the development of imposex (the masculinization of female gastropods considered to be the result of alterations to endocrine-mediated pathways) in the dog-whelk Nucella lapillus. Animals (n = 257) that displayed various stages of tributyltin (TBT)-induced imposex were collected from sites in southwest England, and their imposex status was determined by physical examination. Linear regression analysis revealed a very strong relationship (correlation coefficient of 0.935, p < 0.0001) between the degree of imposex and the extent of DNA damage (micronucleus formation) in hemocytes. Moreover, histological examination of a larger number of dog-whelks collected from sites throughout Europe confirmed the presence of hyperplastic growths, primarily on the vas deferens and penis in both TBT-exposed male snails and in females that exhibited imposex. A strong association was found between TBT body burden and the prevalence of abnormal growths, thereby providing compelling evidence to support the hypothesis that environmental chemicals that affect reproductive processes do so partly through DNA damage pathways.
Previous investigations have shown that bisphenol A (BPA) induces a superfeminization syndrome in the freshwater snail Marisa cornuarietis at concentrations as low as 1 μg/L. Superfemales are characterized by the formation of additional female organs, enlarged accessory sex glands, gross malformations of the pallial oviduct, and a stimulation of egg and clutch production, resulting in increased female mortality. However, these studies were challenged on the basis of incomplete experimentation. Therefore, the objective of the current approach was to bridge several gaps in knowledge by conducting additional experiments. In an initial series of experiments, study results from the reproductive phase of the snails were evaluated in the sub-micrograms per liter range. Before and after the spawning season, superfemale responses were observed [NOEC (no observed effect concentration) 7.9 ng/L, EC10 (effective concentration at 10%) 13.9 ng/L], which were absent during the spawning season. A further experiment investigated the temperature dependence of BPA responses by exposing snails at two temperatures in parallel. The adverse effect of BPA was at least partially masked at 27°C (EC10 998 ng/L) when compared with 20°C (EC10 14.8 ng/L). In M. cornuarietis, BPA acts as an estrogen receptor (ER) agonist, because effects were completely antagonized by a co-exposure to tamoxifen and Faslodex. Antiandrogenic effects of BPA, such as a significant decrease in penis length at 20°C, were also observed. Competitive receptor displacement experiments indicate the presence of androgen- and estrogen-specific binding sites. The affinity for BPA of the estrogen binding sites in M. cornuarietis is higher than that of the ER in aquatic vertebrates. The results emphasize that prosobranchs are affected by BPA at lower concentrations than are other wildlife groups, and the findings also highlight the importance of exposure conditions.
Tens of thousands of man-made chemicals are in regular use and discharged into the environment. Many of them are known to interfere with the hormonal systems in humans and wildlife. Given the complexity of endocrine systems, there are many ways in which endocrine-disrupting chemicals (EDCs) can affect the body’s signaling system, and this makes unraveling the mechanisms of action of these chemicals difficult. A major concern is that some of these EDCs appear to be biologically active at extremely low concentrations. There is growing evidence to indicate that the guiding principle of traditional toxicology that “the dose makes the poison” may not always be the case because some EDCs do not induce the classical dose–response relationships. The European Union project COMPRENDO (Comparative Research on Endocrine Disrupters—Phylogenetic Approach and Common Principles focussing on Androgenic/Antiandrogenic Compounds) therefore aims to develop an understanding of potential health problems posed by androgenic and antiandrogenic compounds (AACs) to wildlife and humans by focusing on the commonalities and differences in responses to AACs across the animal kingdom (from invertebrates to vertebrates).
Polyploidy is common in higher eukaryotes, especially in plants, but it is generally assumed that most prokaryotes contain a single copy of a circular chromosome and are therefore monoploid. We have used two independent methods to determine the genome copy number in halophilic archaea, 1) cell lysis in agarose blocks and Southern blot analysis, and 2) Real-Time quantitative PCR. Fast growing H. salinarum cells contain on average about 25 copies of the chromosome in exponential phase, and their ploidy is downregulated to 15 copies in early stationary phase. The chromosome copy number is identical in cultures with a twofold lower growth rate, in contrast to the results reported for several other prokaryotic species. Of three additional replicons of H. salinarum, two have a low copy number that is not growth-phase regulated, while one replicon even shows a higher degree of growth phase-dependent regulation than the main replicon. The genome copy number of H. volcanii is similarly high during exponential phase (on average 18 copies/cell), and it is also downregulated (to 10 copies) as the cells enter stationary phase. The variation of genome copy numbers in the population was addressed by fluorescence microscopy and by FACS analysis. These methods allowed us to verify the growth phase-dependent regulation of ploidy in H. salinarum, and they revealed that there is a wide variation in genome copy numbers in individual cells that is much larger in exponential than in stationary phase. Our results indicate that polyploidy might be more widespread in archaea (or even prokaryotes in general) than previously assumed. Moreover, the presence of so many genome copies in a prokaryote raises questions about the evolutionary significance of this strategy.
Background Olfactory receptors work at the interface between the chemical world of volatile molecules and the perception of scent in the brain. Their main purpose is to translate chemical space into information that can be processed by neural circuits. Assuming that these receptors have evolved to cope with this task, the analysis of their coding strategy promises to yield valuable insight in how to encode chemical information in an efficient way. Results We mimicked olfactory coding by modeling responses of primary olfactory neurons to small molecules using a large set of physicochemical molecular descriptors and artificial neural networks. We then tested these models by recording in vivo receptor neuron responses to a new set of odorants and successfully predicted the responses of five out of seven receptor neurons. Correlation coefficients ranged from 0.66 to 0.85, demonstrating the applicability of our approach for the analysis of olfactory receptor activation data. The molecular descriptors that are best-suited for response prediction vary for different receptor neurons, implying that each receptor neuron detects a different aspect of chemical space. Finally, we demonstrate that receptor responses themselves can be used as descriptors in a predictive model of neuron activation. Conclusions The chemical meaning of molecular descriptors helps understand structure-response relationships for olfactory receptors and their 'receptive fields'. Moreover, it is possible to predict receptor neuron activation from chemical structure using machine-learning techniques, although this is still complicated by a lack of training data.
Background Identification and evaluation of surface binding-pockets and occluded cavities are initial steps in protein structure-based drug design. Characterizing the active site's shape as well as the distribution of surrounding residues plays an important role for a variety of applications such as automated ligand docking or in situ modeling. Comparing the shape similarity of binding site geometries of related proteins provides further insights into the mechanisms of ligand binding. Results We present PocketPicker, an automated grid-based technique for the prediction of protein binding pockets that specifies the shape of a potential binding-site with regard to its buriedness. The method was applied to a representative set of protein-ligand complexes and their corresponding apo-protein structures to evaluate the quality of binding-site predictions. The performance of the pocket detection routine was compared to results achieved with the existing methods CAST, LIGSITE, LIGSITEcs, PASS and SURFNET. Success rates PocketPicker were comparable to those of LIGSITEcs and outperformed the other tools. We introduce a descriptor that translates the arrangement of grid points delineating a detected binding-site into a correlation vector. We show that this shape descriptor is suited for comparative analyses of similar binding-site geometry by examining induced-fit phenomena in aldose reductase. This new method uses information derived from calculations of the buriedness of potential binding-sites. Conclusions The pocket prediction routine of PocketPicker is a useful tool for identification of potential protein binding-pockets. It produces a convenient representation of binding-site shapes including an intuitive description of their accessibility. The shape-descriptor for automated classification of binding-site geometries can be used as an additional tool complementing elaborate manual inspections.
Background The connection of the variable part of the heavy chain (VH) and and the variable part of the light chain (VL) by a peptide linker to form a consecutive polypeptide chain (single chain antibody, scFv) was a breakthrough for the functional production of antibody fragments in Escherichia coli. Being double the size of fragment variable (Fv) fragments and requiring assembly of two independent polypeptide chains, functional Fab fragments are usually produced with significantly lower yields in E. coli. An antibody design combining stability and assay compatibility of the fragment antigen binding (Fab) with high level bacterial expression of single chain Fv fragments would be desirable. The desired antibody fragment should be both suitable for expression as soluble antibody in E. coli and antibody phage display. Results Here, we demonstrate that the introduction of a polypeptide linker between the fragment difficult (Fd) and the light chain (LC), resulting in the formation of a single chain Fab fragment (scFab), can lead to improved production of functional molecules. We tested the impact of various linker designs and modifications of the constant regions on both phage display efficiency and the yield of soluble antibody fragments. A scFab variant without cysteins (scFabdeltaC) connecting the constant part 1 of the heavy chain (CH1) and the constant part of the light chain (CL) were best suited for phage display and production of soluble antibody fragments. Beside the expression system E.coli, the new antibody format was also expressed in Pichia pastoris. Monovalent and divalent fragments (DiFabodies) as well as multimers were characterised. Conclusion A new antibody design offers the generation of bivalent Fab derivates for antibody phage display and production of soluble antibody fragments. This antibody format is of particular value for high throughput proteome binder generation projects, due to the avidity effect and the possible use of common standard sera for detection.
Background The Radical Pair model proposes that magnetoreception is a light-dependent process. Under low monochromatic light from the short-wavelength part of the visual spectrum, migratory birds show orientation in their migratory direction. Under monochromatic light of higher intensity, however, they showed unusual preferences in other directions or axial preferences. To determine whether or not these responses are still controlled by the respective light regimes, European robins, Erithacus rubecula, were tested under UV, Blue, Turquoise and Green light at increasing intensities, with orientation in migratory direction serving as a criterion whether or not magnetoreception works in the normal way. Results Under low light with a quantal flux of 8 times 10 to 15 power quanta s-1 m-2, the birds were well oriented in their seasonally appropriate migratory direction under 424 nm Blue, 502 nm Turquoise and 565 nm Green light, indicating unimpaired magnetoreception. Under 373 nm UV of the same quantal flux, they were not oriented in migratory direction, showing a preference of the east-west axis instead, but they showed excellent orientation in migratory direction under UV of lower intensity. Intensities of above 36 times 10 to 15 power quanta s-1 m-2 of Blue, Turquoise and Green light elicited a variety of responses: disorientation, headings along the east-west axis, headings along the north-south axis or 'fixed' direction tendencies. These responses changed as the intensity was increased from 36 times 10 to the 15 power quanta s-1 m-2 to 54 and 72 times 10 to 15 power quanta s-1 m-2. Conclusion The specific manifestation of responses in directions other than migratory direction clearly depends on the ambient light regime. This implies that although mechanisms normally providing magnetic compass information seem disrupted, processes that are activated by light still control the behavior. It suggests complex interactions between different types of receptors, magnetic and visual. The nature of the receptors involved and details of their connections are not yet known; however, a role of the color cones in the processes mediating magnetic input is suggested.
Oral presentations Background: We selected peptide ligands for the HIV-1 packaging signal PSI by screening phage displayed peptide libraries. Peptide ligands were optimized by screening spot synthesis peptide membranes. The aim of this study is the functional characterization of these peptide ligands with respect to inhibition of HIV-1 replication. Methods: Phage displayed peptide libraries were screened with PSI-RNA structures. The Trp-rich peptide motifs were optimized for specific binding on spot synthesis peptide membranes. The best binding peptide was expressed intracellularly in fusion with RFP or linked to a protein transduction domain (PTD) for intracellular delivery. The effects on virion production were analyzed using pseudotyped lentiviral particles. Results: After positive and negative selection rounds, phages binding specifically to PSI-RNA were identified by ELISA. Peptide inserts contained conserved motifs of aromatic amino acids known to be implicated in binding of PSI-RNA by the natural Gag ligand. The filter assay identified HKWPWW as the best binding ligand for PSI-RNA, which is delivered into several cell lines by addition of a PTD. Compared to a control peptide, the HKWPWW peptide inhibited HIV-1 replication as deduced from reduced titers of culture supernatants. As HKWPWW also binds to the TAR-RNA like the natural nucleocapsid PSI-RNA ligand, the effect on Tat-TAR inhibition will also be analyzed. Currently T-cell lines are established which stably express HKWPWW as well as a control peptide, which will be infected with HIV-1 to monitor the ability of HKWPWW to inhibit wild type HIV-1 replication. Conclusion: The selection of a peptide ligand for PSI-RNA able to inhibit HIV-1 replication proves the suitability of the phage display technology for the selection of peptides binding to RNA-structures. This enables the indentification of peptides serving as leads to interfere with additional targets in the HIV-1 replication cycle.
In an effort to link quantitative morphometric information with molecular data on the population level, we have analysed 19 populations of the conchologically variable land snail Candidula unifasciata from across the species range for variation in quantitative shell traits and at the mitochondrial 16S ribosomal (r)DNA locus. In genetic analysis, including 21 additional populations, we observed two fundamental haplotype clades with an average pairwise sequence divergence of 0.209 ± 0.009 between clades compared to 0.017 ± 0.012 within clades, suggesting the presence of two different evolutionary lineages. Integrating additional shell material from the Senckenberg Malacological Collection, a highly significant discriminant analysis on the morphological shell traits with fundamental haplotype clades as grouping variable suggested that the less frequent haplotype corresponds to the described subspecies C. u. rugosiuscula, which we propose to regard as a distinct species. Both taxa were highly subdivided genetically (FST = 0.648 and 0.777 P < 0.001). This was contrasted by the partition of morphological variance, where only 29.6% and 21.9% of the variance were distributed among populations, respectively. In C. unifasciata, no significant association between population pairwise FST estimates and corresponding morphological fixation indices could be detected, indicating independent evolution of the two character sets. Partial least square analysis of environmental factors against shell trait variables in C. u. unifasciata revealed significant correlations between environmental factors and certain quantitative shell traits, whose potential adaptational values are discussed.
Ribosomal proteins are assumed to stabilize specific RNA structures and promote compact folding of the large rRNA. The conformational dynamics of the protein between the bound and unbound state play an important role in the binding process. We have studied those dynamical changes in detail for the highly conserved complex between the ribosomal protein L11 and the GTPase region of 23S rRNA. The RNA domain is compactly folded into a well defined tertiary structure, which is further stabilized by the association with the C-terminal domain of the L11 protein (L11ctd). In addition, the N-terminal domain of L11 (L11ntd) is implicated in the binding of the natural thiazole antibiotic thiostrepton, which disrupts the elongation factor function. We have studied the conformation of the ribosomal protein and its dynamics by NMR in the unbound state, the RNA bound state and in the ternary complex with the RNA and thiostrepton. Our data reveal a rearrangement of the L11ntd, placing it closer to the RNA after binding of thiostrepton, which may prevent binding of elongation factors. We propose a model for the ternary L11–RNA–thiostrepton complex that is additionally based on interaction data and conformational information of the L11 protein. The model is consistent with earlier findings and provides an explanation for the role of L11ntd in elongation factor binding.
In the inundation area - the basin of the former larger Lake Chad - a special type of sorghum is grown on the clay soils (firgi). This dry-season guinea corn is also called dwarf sorghum or masakwa. In Kanuri, the dominant language in the region, sorghum is called ngawuli. The dry-season types are called ngawuli firgibe (lit. translated: sorghum of the firgi). During the dry season when the natural vegetation becomes dry and yellow, masakwa fields appear in prominent green covering large areas of the clay plains. The most important natural factor for this specialized dry season cropping is the presence of soils with a high clay content. For a better understanding of masakwa and its related issues, a multidisciplinary sub-project (G1) has been established within the SFB 268 (Joint Research Project: History of Culture and Language in the Natural Environment of the West-African Savannah). This project in which all disciplines participate is entitled: "Natural basis for masakwa cultivation and its meaning for the settlement history of the clay plains (firgi) in the Chad basin".
Während über Flora und Vegetation der Wälder, Savannen und Äcker Westafrikas zahlreiche Veröffentlichungen vorliegen, hat man sich mit der ruderalen Flora und Vegetation der Siedlungen bisher nur wenig beschäftigt. Im Rahmen der Forschungen des SFB 268 wurde daher in zwei Ortschaften von Burkina Faso eine Bestandsaufnahme der spontan im Siedlungsbereich und in seiner engeren Umgebung an Ruderalstandorten auftretenden Pflanzenarten durchgeführt, wobei, gemäß den Zielen des SFB 268, auf eine interdisziplinäre Relevanz der Ergebnisse Wert gelegt wurde. Daher standen die Fragen nach der Nutzung der Spontanflora durch die Bevölkerung im Vordergrund des Interesses. In der vorliegenden Arbeit wird über die für die menschliche Ernährung genutzten krautigen Wildpflanzen des Siedlungsbereiches berichtet.
The investigations carried out within the project in NE-Nigeria since 1989 have been focussing on the late Pleistocene and Holocene landscape development of the south eastern Chad basin. Areas of interest include palaeodune fields, clay plains and former beach ridge systems of Lake Chad. Transgressions and regressions of Lake Chad played an important role in the younger landscape history of NE-Nigeria and have also caused great environmental changes. The term „Megachad“ is well known and describes an enormous lake with an extension comparable with the Caspian Sea of today. The term „Microchad“ stands for the other recent extreme in terms of the lake dimensions varying during the times. Environmental changes in the surroundings of Lake Chad are closely connected with transgressions and regressions of the lake. These lake level changes can be climatically induced as well as non-climatically, due to human impact. Nearly all land units have more or less been influenced by the lake, spatially as well as temporally. It is important, though, to notice the scales of the changes. Some changes took place in a millennial scale, some in the scales of centuries or decades, and at least – as can be observed every year – in a seasonal scale.
Numerous ecologists postulate that West African savannas are mostly the result of degradation of formerly closed forests. This hypothesis can only be tested by palaeoecological investigations. The palynological results summarised in this paper document the history of the Sudanian and Sahelian savanna of NE-Nigeria during the last 11.500 years (uncal. BP). Both sites investigated provide evidence for the persistence of savanna throughout the entire Holocene. Patches of closed dry forest may have occurred, but never completely displaced the savanna vegetation. Humid conditions during the early and mid Holocene (from 10.000 BP onwards) caused a rapid spread of Guinean and Sudanian taxa into the northern vegetation zones. A slow return to drier climatic conditions between ca. 6800 BP and ca. 5500 BP can be recorded at both sites. Finally, between 3800 BP and 3300 BP a strong aridification resulted in the establishment of the modern vegetation zones. In both the Sahelian and Sudanian zone the vegetational changes appear to have been primarily controlled by climatic changes, whereas the effects of human activities remain palynologically silent even for the late Holocene.
Two sites situated in the Sahelian and Sudanian zones of NE-Nigeria were chosen for pollen analysis. A sediment core from an interdunal depression in the eastern Manga Grassland provides information on the Holocene vegetation history of the Sahel between c. 9600-3400 B.P. The 3 m pollen record indicates an open savanna during the mid-Holocene. The presence of Sudano-Guinean taxa, which were mainly restricted to the interdunal depressions, points to more humid conditions. Already before c. 4000 B.P., a slow change towards drier conditions and the establishment of the modern Sahelian vegetation is visible in the diagram. This development was accompanied by high fire frequencies. A 16 m core from a crater lake (Lake Tilla) in the Sudanian zone of NE-Nigeria provides a pollen record which can be dated back to approximately 11-12000 B.P. Preliminary pollen spectra show a relatively constant pattern with a dominance of grass pollen even during the middle Holocene.
Im SW Burkina Fasos (sechs Monate Regenzeit und durchschnittlich über 1000 mm Niederschlag) wurden mehrere Trockenwälder auf ihr Artenspektrum und die Bodenverhältnisse hin untersucht. Die Waldformationen fallen durch die Dichte der Gehölzbedeckung, ihren Lianenreichtum und das fast vollständige Fehlen von Gräsern auf. Typische Gehölzarten sind Anogeissus leiocarpus, Diospyros mespiliformis und die Liane Saba senegalensis. Der dichte Strauchunterwuchs und die fehlende Grasschicht verhindern das regelmäßige Eindringen von Buschfeuern. Wegen der Dichte und des Alters der Bäume belegen diese Waldformationen, daß an den Standorten, zumindest für einen sehr langen Zeitraum, kein Feldbau betrieben wurde. Daher konnten sich, auch auf eher als ungünstig zu bewertenden Böden, Trockenwälder ausbilden, die zumindest in ihrer Physiognomie der potentiellen natürlichen Vegetation entsprechen. Jedoch finden sich in den Wäldern oft Spuren menschlicher Aktivitäten aus der Vergangenheit, so z.B. Steinsetzungen, Siedlungshügel und Gruben. Außerdem lassen sich vielfach Anzeichen einer rezenten Nutzung beobachten, so z.B. für die Entnahme von Werkholz, das Schneiteln mancher Baumarten zur Viehfuttergewinnung, gelegentliche Beweidung und das Sammeln von Wildpflanzen.
Les ferrières sont par définition les amas des déchets de la réduction du fer. De par son origine elles constituent des lithosols qui ont beaucoup évolué dans l’espace et dans le temps. A notre connaissance très peu d’études se sont penchées sur cette végétation qui couvre actuellement les sites de réduction du fer. L’inventaire floristique de plusieurs sites en zone soudanienne montre la fréquence de certaines espèces sur les ferrières. L’étude de la chorologie de toutes les espèces confondues ligneuses et herbacées, montrent que la plupart sont constituées par des espèces zoochores et quelques espèces anémochores. Elles sont disséminées principalement par les animaux d’élevage, par les oiseaux. Cette communication synthétise les données des différentes prospections et les premiers résultats de nos observations et analyses. Elle a deux objectifs : de montrer l’importance des activités anthropiques dans la formation du paysage végétal d’une part, et d’autre part de mettre en évidence le processus de colonisation des sols nus et des ferrières en zone soudanienne.
Au Sahel du Burkina Faso, le diagramme pollinique d'Oursi fournit des évidences sur l'apparition de l'agriculture, il y a environ 3000 ans. A partir de ces faits, le but principal des recherches archéologiques dans le cadre du SFB 268 était de trouver et de fouiller des sites qui seraient à même d'apporter des informations sur cette période décisive autour de 3000 ans avant l'actuel. Pour cela, nous avons concentré notre travail sur les provinces du Séno et plus particulièrement de l'Oudalan. Le paysage de cette région est marqué par des dunes qui s'organisent grossièrement en cordons d'orientation nord-est/sud-ouest à travers notre terrain.
La variation dans l'utilisation des ressources végétales est liée aux changements de mode de vie. Le Burkina Faso fait parti des pays habituellement indiqués comme en voie de développement. Ce qualificatif est vrai si on ne regarde que la croissance technologique. Le pays accuse certes un retard sur ce plan, mais la population sait bel et bien développer son intelligence humaine pour faire face à telle ou telle situation. Ainsi, devant une mauvaise récolte, personne n'acceptera de mourir de faim tant que dans l'environnement naturel existeront tous les éléments nécessaires pour survivre: l'eau, les plantes et les animaux. A ce moment-là, le mode de vie change; il ne s'agit plus de récolter, mais il s'agit de prélever, de cueillir. La cueillette, c'était un mode de vie dans l'époque préhistorique. L'homme se rabat sur tout ce qui peut fournir un aliment substantiel: les gros tubercules, les feuilles les plus tendres, les fruits et les graines. Si les trois dernières catégories d'aliments ne posent pas trop de problèmes, la première et les autres organes souterrains sont en général toxiques. Et là encore, l'homme va développer son intelligence pour éliminer cette toxicité mais après une grande perte en vie humaine. Dans le but de savoir un peu plus sur ces différentes périodes de disette et de famine, nous avons mené une enquête à Ouahigouya (Yatenga) et à Toma (Sourou), deux zones qui appartenaient à un même cercle pendant l'époque coloniale, période de la suppression de la Haute-Volta. Par ailleurs nous voulons vérifier la marge d'erreur qu'on peut avoir lors d'une enquête ethnobotanique en se situant dans le temps et l'espace. Cette communication entre en plus dans le cadre de nos travaux de recherche sur l'histoire de la végétation et de l'utilisation des ressources végétales.
L'homme vivant de la cueillette existe toujours au Burkina Faso. Les espèces que nous allons exposer par la suite ne font pas l'objet d'une culture. La plupart certes sont des espèces protégées lors des défrichements. Elles caractérisent souvent les différents faciès de savane rencontrés à travers le pays. Certaines ont des usages généralisés en temps normal, d'autres le sont en temps de disette ou de soudure. Ces espèces ligneuses sont à usages culinaires par leurs feuilles, leurs graines et leurs exsudats. Leur composition chimique montre un certain équilibre énergétique à la consommation et permet de comprendre la santé de nos paysans malgré ce qu'on laisse entendre sur la pauvreté et la sous-alimentation. Dans le cadre de nos travaux pour une meilleure connaissance des espèces tant sur le plan taxonomique, biologique qu'ethnobotanique, nous avons mené depuis cinq ans une enquête sur les différentes utilisations des espèces ligneuses. Le présent travail concerne particulièrement les espèces ligneuses dont certains organes sont utilisés dans alimentation humaine. Nous nous sommes limités à ne parler que d'une vingtaine d'espèces.
La métallurgie du fer jouit d'un regain d'intérêt en Afrique depuis une décénnie. Alors que les diffusionistes et les antidiffusionistes se sont affrontés dans les années 1970, on assiste aujourd'hui à une nouvelle fièvre du "fer" où les chercheurs, mettant de côté l'idéologie, travaillent avec acharnement sur les fourneaux de réduction et sur toutes les traces de cette métallurgie. Les résultats obtenus sont déja impressionnants. L'environnement constituent aussi, désormais, une préoccupation majeure des chercheurs. Les recherches en paléométallurgie au Burkina Faso n'échappent pas totalemennt à cette critique. C'est pour attirer plus d'attention sur l'important complément sociologique des investigations archéologiques que nous proposons en ces lignes les quelques informations relatives aux conditions sociales des forgerons, potiers et potières, réunis dans plusieurs nationalités du Burkina Faso par une sorte de communauté de destin: les arts du feu.
Le Burkina Faso est situé dans la zone soudano-sahélienne où les cultures sont quelquefois aléatoires; dans ces conditions les plantes ligneuses occupent une place importante dans la vie socio-économique du pays. Pourtant, une sécheresses climatique persistante de ces dernières décennies a entraîné une mortalité massive de ces ligneux surtout dans la zone sahélienne. Cette forte dégradation des ressources naturelles est variable d’une zone géo-graphique à une autre pour des raisons diverses. Si les phénomènes généraux de cette dégradation de la végétation et leurs causes sont souvent décrits par de nombreux auteurs, il existe par contre très peu de connaissances détaillées et spécifiques en fonction des zones géographiques sur la menace qui pèse sur les différentes espèces. Dans l’absence de bases scientifiques fiables sur la végétation du passé pour chacune des régions qui permettrait ainsi d’établir avec précision la liste des espèces disparues, il est donc nécessaire de se baser sur la perception de la population rurale qui se trouve bien placée pour déceler tout changement dans la flore. Dans ce contexte, cette étude menée auprès des gourmantchés, vise surtout à identifier les espèces disparues ou celles en voie de disparition dans les différentes zones écologiques à l’est du Burkina Faso; en outre, elle aborde les raisons évoquées par ces populations pour expliquer cette menace qui pèse sur chacune des espèces. L’enquête a enfin contribué à connaître les solutions envisagées par ces dernières pour anéantir ou réduire la menace.
L’inventaire floristique du Burkina Faso est loin d’être clos. Les récentes investigations floristiques ont permis de recenser un grand nombre d’espèces qui n’avaient jamais été mentionnées sur la liste floristique nationale. Une partie de ces espèces sont d’ailleurs guinéocongolaises. Cet inventaire a concerné les aires classées et protégées situées dans le secteur Sudsoudanien. Les richesses floristiques se retrouvent concentrées dans ces aires classées et protégées car ce sont des formations qui jouissent d’une relative bonne gestion par rapport aux autres aires non protégées qui ont été fortement dégradées par l’homme. L’objectif de cette communication est de donner les informations issues de ces différentes investigations sur l’état de connaissance de la diversité végétale du Burkina Faso avec un accent particulier sur le mode de gestion et les utilisations de quelques espèces de la zone sud soudanienne.
Kagbeni and its irrigated oasis are surrounded by subdesert dwarf scrubland. In the present study, a list of 78 species of vascular plants is presented for Kagbeni and its immediate surroundings, supplemented with data on the distribution of the species within the entire Mustan District. The data are arrived from own investigations and the geobotanical literature. A phytogeographical analysis shows the prevalence of western over eastern elements. Species with a wide distribution in Eurasia, which constitute one third of the total flora of Kagbeni, are of great importance as weeds on arable fields and in ruderal places within the irrigated oasis. Their occurrence is closely related to human activity. Presumably, most of these weeds have reached the area under study in connection with agriculture a long time ago. Weeds from the New World, although recorded in other villages of Mustan District, have not been found in Kagbeni. The weed vegetation of Kagbeni is documented by nine vegetation releves, and is compared to releves from Jomsom and Mzrpha. A floristic gradient from south to north that has been detected by earlier investigations throughout the whole district can be reproduced at the local scale. With regard to the weed flora, the effects of different crops are minimal, compared to effects of altitude and other factors related to altitude.
Changes in settlement pattern and culture - the process of down-hill migration in Tula, Bauchi State
(1996)
The process of down-hill migration of the Tula people started during the 1920s and has not yet finished. The resulting present situation might give information how far terraces play any role in the economy, ecology and ideology of the Tula. Approaching this question from a socio-agricultural point of view some facts which indicate the pertaining or overcoming of traditional structures will be presented. In the following the land tenure system, the adoption of innovations and the role of women in agriculture will be discussed comparatively for Tula Wange and Tula Baule on the plateau, Fantami, which is generated by down-hill dwellers of Tula Wange, with its more or less bad farming conditions on shallow sandy soils and Kaltin, where the down migrants of Tula Baule settle in a more fertile area. Tula Wange numbers around 2000 households, Baule 1000, Fantami about 200 and Kaltin 350 of which the sample survey includes 15% in the plateau sites and 25% in the plain settlements.
Notre communication porte sur le thème suivant: "Anthropisation du couvert végétal dans la province de Namentenga et ses conséquences socioéconomiques: cas de la région de Tougouri, en zone subsahélienne" (centre-nord du Burkina Faso). A travers cette étude de cas, nous voulons attirer l'attention sur les problèmes environnementaux du Burkina Faso. En effet, les déficits pluviométriques cumulés, depuis quelques décennies, sont à l'origine de la dégradation des écosystèmes. La surexploitation des terres entraîne également l'épuisement des sols et la diminution des ressources végétales. Un telle situation n'est pas sans conséquence sur les activités socioéconomiques des populations. Le plan de notre communication sera donc comme suit: 1. Présentation du degré-carré de Tougouri, sur le plan physique 2. Dynamique du couvert végétal sous l'action anthropique, et les conséquences socioéconomiques 3. Perspectives d'avenir
La coupure que l'on constate dans les forêts denses africaines au niveau du Togo et du Bénin soulève de nombreuses questions sur les rapports forêt/savane au cours des derniers millénaires. Le projet Dahomey Gap vise à y répondre, par une approche pluridisciplinaire intégrant botanique et histoire de la végétation dans le Sud-Bénin et le Sud-Ouest du Nigéria. A partir de travaux déjà avancés sur la végétation du Bénin et des premières prospections palynologiques, quelques aspects du projet sont exposés ici: tels la caractérisation des différentes formations forestières du Bénin, les premiers résultats sur l'histoire holocène de la végétation du Sud-Bénin (mangroves, forêts, savanes) enregistrée depuis près de 7000 ans dans les lagunes.
Population structure was estimated in a continuous population of a small land snail (Trochoidea geyeri). Mark-recapture experiments and randomly amplified polymorphic DNA analyses indicate that the population structure can be described by the isolation by distance model of Wright (1946). Estimates of density and dispersal suggest a neighbourhood size of 70-208 individuals on an area of 13-21 m². A principal component analysis of the randomly amplified polymorphic DNA data reveals clinal variation of genetic composition across the population, as predicted by the neighbourhood concept. An analysis of molecular variance indicates substantial genetic structuring. Comparisons of the genetic distances, expressed as euclidean distances among individuals, versus the geographic distance between sampling sites yield a highly significant positive correlation (Mantel test: r = 0.567, p<0.0001). The revealed pattern of populational subdivision on a microgeographic scale seems to be one of the principal processes generating and maintaining genetic diversity within populations of small land gastropods.
In the present study the population genetic structure of the terrestrial snail Pomatias elegans was related to habitat structure on a microspatial scale. The genetic variability of 1607 individuals from 51 sampling sites in five different populations in Provence, France, was studied with an allozyme marker using population genetic methods, Mantel tests and spatial autocorrelation techniques were applied to different connectivity networks accounting for the structural features of the landscape. It is suggested that the population structure is, to a large extent, a function of the habitat quality, quantified as population density, and of the spatial arrangement of the habitat in the landscape and not of the geographical distance per se. In fragmented habitats, random genetic drift was the prevailing force for sampling sites separated by a few hundred meters.
Background: Growth rate is central to the development of cells in all organisms. However, little is known about the impact of changing growth rates. We used continuous cultures to control growth rate and studied the transcriptional program of the model eukaryote Saccharomyces cerevisiae, with generation times varying between 2 and 35 hours.
Results: A total of 5930 transcripts were identified at the different growth rates studied. Consensus clustering of these revealed that half of all yeast genes are affected by the specific growth rate, and that the changes are similar to those found when cells are exposed to different types of stress (>80% overlap). Genes with decreased transcript levels in response to faster growth are largely of unknown function (>50%) whereas genes with increased transcript levels are involved in macromolecular biosynthesis such as those that encode ribosomal proteins. This group also covers most targets of the transcriptional activator RAP1, which is also known to be involved in replication. A positive correlation between the location of replication origins and the location of growth-regulated genes suggests a role for replication in growth rate regulation.
Conclusion: Our data show that the cellular growth rate has great influence on transcriptional regulation. This, in turn, implies that one should be cautious when comparing mutants with different growth rates. Our findings also indicate that much of the regulation is coordinated via the chromosomal location of the affected genes, which may be valuable information for the control of heterologous gene expression in metabolic engineering.
Length variations of repetitive sequences in different AT-rich loop-coding regions of mitochondrial 16S rDNA in two gastropod species were discovered during intraspecific haplotype surveys. Examination of the discrete length variation of the basic repeat unit in a phylogenetic framework led to the conclusion of a microsatellite-like mutational dynamic. The observations suggest that the presence of a repetitive sequence structure alone is sufficient to trigger this dynamic.
I analysed the importance of shell size, shell shape, habitat preferences and availability, experienced climate, active dispersal and influence of Pleistocene glaciations for the range sizes of 37 Western Palaearctic Helicidae s.l. species for which a phylogeny was available. In both cross-species and phylogenetically controlled analyses, the range sizes were positively correlated to climatic tolerance, shell size, active dispersal and influence of Pleistocene glaciations. In addition, range sizes increased significantly with latitude. Multiple regression suggested that, predominantly, the influence of Pleistocene glaciations, tolerance to large annual temperature ranges and shell size influenced the distributional range sizes. Habitat preference, range and availability, active dispersal and shell shape explained no additional variance. The results suggest that the processes influencing species range size of the Helicidae s.l. are mainly related to the climatic shifts after the Pleistocene.
Alzheimer's disease-related mutations in the presenilin-1 gene (PS1) are leading to an elevated production of neurotoxic beta-amyloid 1-42 and may additionally enhance oxidative stress. Here, we provide in vivo evidence indicating that brains of transgenic mice expressing different human Alzheimer-linked PS1 mutations exhibit a reduced activity of two antioxidant enzymes. For this purpose, mice transgenic for human PS1 and for single and multiple PS1 mutations were generated. Mice with multiple PS1 mutations showed a significantly decreased activity of the antioxidant enzymes Cu/Zn superoxide dismutase and glutathione reductase already at an age of 3-4 months. As expected, this effect was less pronounced for the mice with a single PS1 mutation. By contrast, animals bearing normal human PS1 showed significantly elevated enzyme activities relative to non-transgenic littermate controls.
Background Reliable taxonomic identification at the species level is the basis for many biological disciplines. In order to distinguish species, it is necessary that taxonomic characters allow for the separation of individuals into recognisable, homogeneous groups that differ from other such groups in a consistent way. We compared here the suitability and efficacy of traditionally used shell morphology and DNA-based methods to distinguish among species of the freshwater snail genus Radix (Basommatophora, Pulmonata). Results Morphometric analysis showed that shell shape was unsuitable to define homogeneous, recognisable entities, because the variation was continuous. On the other hand, the Molecularly defined Operational Taxonomic Units (MOTU), inferred from mitochondrial COI sequence variation, proved to be congruent with biological species, inferred from geographic distribution patterns, congruence with nuclear markers and crossing experiments. Moreover, it could be shown that the phenotypically plastic shell variation is mostly determined by the environmental conditions experienced. Conclusion Contrary to DNA-taxonomy, shell morphology was not suitable for delimiting and recognising species in Radix. As the situation encountered here seems to be widespread in invertebrates, we propose DNA-taxonomy as a reliable, comparable, and objective means for species identification in biological research.
Enhanced apoptosis and elevated levels of reactive oxygen species (ROS) play a major role in aging. In addition, several neurodegenerative diseases are associated with increased oxidative stress and apoptosis in neuronal tissue. Antioxidative treatment has neuro-protective effects. The aim of the present study was to evaluate changes of susceptibility to apoptotic cell death by oxidative stress in aging and its inhibition by the antioxidant Ginkgo biloba extract EGb761. We investigated basal and ROS-induced levels of apoptotic lymphocytes derived from the spleen in young (3 months) and old (24 months) mice. ROS were induced by 2-deoxy-D-ribose (dRib) that depletes the intracellular pool of reduced glutathione. Lymphocytes from aged mice accumulate apoptotic cells to a significantly higher extent under basal conditions compared to cells from young mice. Treatment with dRib enhanced this difference, implicating a higher sensitivity to ROS in aging. Apoptosis can be reduced in vitro by treatment with EGb761. In addition, mice were treated daily with 100mg/kg EGb761 per os over a period of two weeks. ROS-induced apoptosis was significantly reduced in the EGb761 group. Interestingly, this effect seemed to be more pronounced in old mice.
Apoptosis seems to be involved in immunosenescence associated with aging. Moreover, in lymphocytes (PBL) of patients with Alzheimer's disease, an increased susceptibility to the apoptotic pathway has been described possibly due to impaired protection of oxidative stress. Accordingly, it seemed to be of particular interest to investigate the contribution of normal aging to the susceptibility from human lymphocytes to programmed cell death. We could show that PBL from elderly individuals (>60 years) accumulate apoptosing cells to a significant higher extent in spontaneous and activation-induced cell death compared to younger controls (<35 years). Treatment with the oxidative stressor 2-deoxy-D-ribose or with agonistic-CD95-antibody pronounced this effect even more implicating a higher sensitivity to reactive oxygen species and a higher functional CD95 expression, respectively. In addition, expression of the activation markers HLA-DR and CD95 was significantly increased in CD3+-cells of aged subjects, while expression of CD25 did not seem to be affected by age. Expression of Bcl-2 was increased in aging and correlated with the number of apoptotic cells.
The relevance of physiological immune aging is of great interest with respect to determining disorders with pathologic immune function in aging individuals. In recent years, the relevance of changes in peripheral lymphocytes in age-associated neurologic diseases has become more evident. Due to the lack of immunological studies, covering more than one event after mitogenic activation, we envisaged a new concept in the present study, aiming to investigate several events, starting from T cell receptor (TCR) ligation up to T cell proliferation. In addition, we addressed the question whether changes are present in the subsets (CD4, CD8) with aging. Phosphorylation of tyrosine residues declines with increasing age in CD4+ cells. Fewer levels of CD69 positive cells after 4 h mitogenic activation, altered expression of cytokines (IL2, IFN-gamma and TNF-alpha; 22 h) and lower proliferation (72 h) were determined in aging. Moreover, it could be shown that CD8+ lymphocytes react more effectively to mitogenic stimulation with reference to CD69 expression and proliferation in both age groups (<35 and >60 years old). These data indicate that T cell activation, mediated by TCR engagement, is significantly impaired in aging and both subsets are affected. However, bypassing the TCR does not fully restore T cell function, indicating that there are more mechanisms involved than impaired signal transduction through TCR only. The results will be discussed in relation to their relevance in neurodegenerative and psychiatric disorders.
In vivo manipulation of interleukin-2 expression by a retroviral tetracycline (tet)-regulated system
(1999)
We have used the tetracycline (tet)-regulated system as described previously to evaluate the applicability of controlled gene expression in cancer gene therapy. As a model gene, we used the human interleukin-2 (IL-2) gene, which has been placed under the transcriptional control of the tetO/promoter. Human melanoma cells were transduced by two modified retroviral tet vectors containing the transactivator regulatory unit and the IL-2 gene driven by the tetO/promoter, respectively. In the absence of tet, IL-2 expression in the target cells was stable over several months. IL-2 production was in the range of 40 U/106 cells/24 hours. A fine tuning of IL-2 expression could be achieved by culturing the transduced cells with increasing doses of tet, whereby a concentration of 500 ng/mL tet in the culture medium abrogated IL-2 expression. Most importantly for clinical application, IL-2 expression by the transduced melanoma cells could also be regulated in vivo. When nu/nu mice were inoculated with the transduced tumor cells, they failed to develop tumors. Instead, the inhibition of IL-2 expression in the transduced tumor cells by oral administration of tet led to subcutaneous tumor growth; this growth rate was comparable with the growth rate of subcutaneously inoculated untransduced parental cells. The finding demonstrates the applicability of the tet-regulated system in cancer gene therapy.
Many cases of early-onset inherited Alzheimer's disease (AD) are caused by mutations in the presenilin-1 (PS1) gene. Expression of PS1 mutations in cell culture systems and in primary neurons from transgenic mice increases their vulnerability to cell death. Interestingly, enhanced vulnerability to cell death has also been demonstrated for peripheral lymphocytes from AD patients. We now report that lymphocytes from PS1 mutant transgenic mice show a similar hypersensitivity to cell death as do peripheral cells from AD patients and several cell culture systems expressing PS1 mutations. The cell death-enhancing action of mutant PS1 was associated with increased production of reactive oxygen species and altered calcium regulation, but not with changes of mitochondrial cytochrome c. Our study further emphasizes the pathogenic role of mutant PS1 and may provide the fundamental basis for new efforts to close the gap between studies using neuronal cell lines transfected with mutant PS1, neurons from transgenic animals, and peripheral cells from AD patients. Copyright 2001 Academic Press.
In large models of neuronal cell death, there is a tight correlation between Cdk5 deregulation and cell-cycle dysfunction. However, pathways that link Cdk5 to the cell cycle during neuronal death are still unclear. We have investigated the molecular events that precede p25/Cdk5-triggered neuronal death using a neuronal cell line that allows inducible p25 expression. In this system, no sign of apoptosis was seen before 24 hours of p25 induction. Thus, at that time, cell-cycle-regulatory proteins were analysed by immunoblotting and some of them showed a significant deregulation. Interestingly, after time-course experiments, the earliest feature correlated with p25 expression was the phosphorylation of the retinoblastoma protein (Rb). Indeed, this phosphorylation was observed 6 hours after p25 induction and was abolished in the presence of a Cdk5 inhibitor, roscovitine, which does not inhibit the usual Rb cyclin-D kinases Cdk4 and Cdk6. Furthermore, analyses of levels and subcellular localization of Cdk-related cyclins did not reveal any change following Cdk5 activation, arguing for a direct effect of Cdk5 activity on Rb protein. This latter result was clearly demonstrated by in vitro kinase assays showing that the p25-Cdk5 complex in our cell system phosphorylates Rb directly without the need for any intermediary kinase activity. Hence, Rb might be an appropriate candidate that connects Cdk5 to cell-cycle deregulation during neuronal cell death.
The identification of specific genetic (presenilin-1 [PS1] and amyloid precursor protein [APP] mutations) and environmental factors responsible for Alzheimer's disease (AD) has revealed evidence for a shared pathway of neuronal death. Moreover, AD-specific cell defects may be observed in many other nonneuronal cells (e.g., lymphocytes). Thus, lymphocytes may serve as a cellular system in which to study risk factors of sporadic, as well as genetic AD in vivo. The aim of our present study was to clarify whether lymphocytes bearing genetic or sporadic risk factors of AD share an increased susceptibility to cell death. Additionally we examined whether a cell typespecific vulnerability pattern was present and how normal aging, the main risk factor of sporadic AD, contributes to changes in susceptibility to cell death. Here, we report that lymphocytes affected by sporadic or genetic APP and PS1 AD risk factors share an increased vulnerability to cell death and exhibit a similar cell type-specific pattern, given that enhanced vulnerability was most strongly developed in the CD4+ T-cell subtype. In this paradigm, sporadic risk factors revealed the highest impact on cell type-specific sensitivity of CD4+ T cells to apoptosis. In contrast, normal aging results in an increased susceptibility to apoptosis of both, CD4+ and CD8+ T cells.
Introduction: Reactive oxygen species (ROS) have been implicated in neurodegeneration and seem to be involved in the physiology and pathophysiology of several diseases, including normal aging and Alzheimer’s disease (AD). Enhanced ROS production in aging or AD is not restricted to the brain, but can also been seen in several peripheral tissues. The objective of the present study was to evaluate whether the mechanisms involved in the generation of oxidative stress in normal senescence and Alzheimer’s disease are identical or not. Methods: We analysed intracellular basal levels of ROS in lymphocytes from AD patients and healthy young and aged not-demented subjects as well as ROS levels following stimulation with d-ribose and staurosporine in all three groups. ROS levels were measured by flow cytometry using the intracellular fluorescence dye dihydrorhodamine123 (DHR123). Results: Our study shows that AD lymphocytes have increased basal levels of ROS, low susceptibility to ROS stimulation by 2-deoxy-D-ribose (dRib) and an increased response to staurosporine when compared with age-matched controls. Discussion: The data suggest that the defect(s) responsible for enhanced ROS production in AD may involve different or additional biological pathways than those involved in enhanced ROS generation during aging.
As major sources of reactive oxygen species (ROS), mitochondrial structures are exposed to high concentrations of ROS and may therefore be particularly susceptible to oxidative damage. Mitochondrial damage could play a pivotal role in the cell death decision. A decrease in mitochondrial energy charge and redox state, loss of transmembrane potential (depolarization), mitochondrial respiratory chain impairment, and release of substances such as calcium and cytochrome c all contribute to apoptosis. These mitochondrial abnormalities may constitute a part of the spectrum of chronic oxidative stress in Alzheimer's disease. Accumulation of amyloid beta (Abeta) in form of senile plaques is also thought to play a central role in the pathogenesis of Alzheimer's disease mediated by oxidative stress. In addition, increasing evidence shows that Abeta generates free radicals in vitro, which mediate the toxicity of this peptide. In our study, PC12 cells were used to examine the protective features of EGb 761(definition see editorial) on mitochondria stressed with hydrogen peroxide and antimycin, an inhibitor of complex III. In addition, we investigated the efficacy of EGb 761 in Abeta-induced MTT reduction in PC12 cells. Moreover, we examined the effects of EGb 761 on ROS levels and ROS-induced apoptosis in lymphocytes from aged mice after in vivo administration. Here, we will report that EGb 761 was able to protect mitochondria from the attack of hydrogen peroxide, antimycin and Abeta. Furthermore, EGb 761 reduced ROS levels and ROS-induced apoptosis in lymphocytes from aged mice treated orally with EGb 761 for 2 weeks. Our data further emphasize neuroprotective properties of EGb 761, such as protection against Abeta-toxicity, and antiapoptotic properties, which are probably due to its preventive effects on mitochondria.
FGF-2, a potent multifunctional and neurotrophic growth factor, is widely expressed in the brain and upregulated in cerebral ischemia. Previous studies have shown that intraventricularly or systemically administered FGF-2 reduces the size of cerebral infarcts. Whether endogenous FGF-2 is beneficial for the outcome of cerebral ischemia has not been investigated. We have used mice with a null mutation of the fgf2 gene to explore the relevance of endogenous FGF-2 in brain ischemia. Focal cerebral ischemia was produced by occlusion of the middle cerebral artery (MCAO). We found a 75% increase in infarct volume in fgf2 knock-out mice versus wild type littermates (P < 0.05). This difference in the extent of ischemic damage was observed after 24 h, and correlated with decreased viability in fgf2 mutant mice following MCA occlusion. Increased infarct volume in fgf2 null mice was associated with a loss of induction in hippocampal BDNF and trkB mRNA expression. These findings indicate that signaling through trkB may contribute to ameliorating brain damage following ischemia and that bdnf and trkB may be target genes of FGF-2. Together, our data provide the first evidence that endogenous FGF-2 is important in coping with ischemic brain damage suggesting fgf2 as one crucial target gene for new therapeutic strategies in brain ischemia.
Background The reciprocal (9;22) translocation fuses the bcr (breakpoint cluster region) gene on chromosome 22 to the abl (Abelson-leukemia-virus) gene on chromosome 9. Depending on the breakpoint on chromosome 22 (the Philadelphia chromosome – Ph+) the derivative 9+ encodes either the p40(ABL/BCR) fusion transcript, detectable in about 65% patients suffering from chronic myeloid leukemia, or the p96(ABL/BCR) fusion transcript, detectable in 100% of Ph+ acute lymphatic leukemia patients. The ABL/BCRs are N-terminally truncated BCR mutants. The fact that BCR contains Rho-GEF and Rac-GAP functions strongly suggest an important role in cytoskeleton modeling by regulating the activity of Rho-like GTPases, such as Rho, Rac and cdc42. We, therefore, compared the function of the ABL/BCR proteins with that of wild-type BCR. Methods We investigated the effects of BCR and ABL/BCRs i.) on the activation status of Rho, Rac and cdc42 in GTPase-activation assays; ii.) on the actin cytoskeleton by direct immunofluorescence; and iii) on cell motility by studying migration into a three-dimensional stroma spheroid model, adhesion on an endothelial cell layer under shear stress in a flow chamber model, and chemotaxis and endothelial transmigration in a transwell model with an SDF-1α gradient. Results Here we show that both ABL/BCRs lost fundamental functional features of BCR regarding the regulation of small Rho-like GTPases with negative consequences on cell motility, in particular on the capacity to adhere to endothelial cells. Conclusion Our data presented here describe for the first time an analysis of the biological function of the reciprocal t(9;22) ABL/BCR fusion proteins in comparison to their physiological counterpart BCR.