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Translation in plastids : elucidation of decoding mechanisms and functions of ribosomal components
(2008)
Traffic of molecular motors
(2008)
Die Arbeitsgruppe von Ralph Gräf befasst sich mit der Rolle der Mikrotubuli bei dynamischen Bewegungsvorgängen der Zelle. Mikrotubuli sind röhrenförmige Elemente des Zellskeletts, die alle von einem zentralen Ort in der Nähe des Zellkerns, dem Centrosom, auswachsen und von dort organisiert werden. Neben ihrer Funktion als Transportweg für zahlreiche Substanzen und Zellorganelle spielen sie eine zentrale Rolle bei der Zellteilung, indem sie mit dafür sorgen, dass die Erbsubstanz korrekt auf die Tochterzellen verteilt wird. Den Schwerpunkt der Forschungsarbeiten bildet die Charakterisierung neuer Komponenten des Centrosoms und neuer Mikrotubuli- bindender Proteine im einfachen Modellsystem der Dictyostelium Amöbe. Diese Arbeiten sind von großer Bedeutung für die Erklärung Zellskelett-assoziierter Krankheiten und Störungen der geordneten Zellteilung, wie sie beispielsweise in Krebszellen auftritt.
Die Referentin erläutert den Ursprung embryonaler Stammzellen und woher sie kommen. Gezeigt wird weiter unter anderem die Gewinnung embryonaler Stammzellen aus der Blastozyste der Maus, und es wird auf die Differenzierung von glatter Muskulatur und Knochen eingegangen. Die Wissenschaftlerin sieht in der Etablierung neuer in vitro Modelle eine große Perspektive für die Forschung mit Maus-Stammzellen.
Die vorliegende Untersuchung von Fledermaeusen in Sommer- und Winterquartieren liefert neue daten zur Verbreitung und Haeufigkeit von Ektoparasiten aus Brandenburg und anderen Bundeslaendern. An 11 Fledermausarten wurden insgesamt 7 Floharten (Ischnosyllidae), zwei Lausfliegenarten (Nycteribiidae) und zwei Wanzenarten (Cimicidae) nachgewiesen. Die Floharten Ischnopsyllus intermedius und die Artengruppe I. simplex/mysticus ergaenzen die Liste der aktuellen Funde fuer Brandenburg. Nach dem milden Winter 2006-7 wurden in einigen Winterquartieren Veraenderungen im Artenspektrum der Parasiten festgestellt. Nycteribia kolenatii an Myotis daubentoni und Nycteribia eusarca an Nyctalus noctula traten bei der vorliegenden Untersuchung relativ haeufig auf. Die anderen ektoparasitischen Floehe und Lausfliegen waren sehr selten zu finden. Die meisten Parasitenarten und die hoechste Befallsintensitaet wies die Wasserfledermaus (Myotis daubentoni) auf.
Die in der Umgebung von potsdam untersuchten Nester der Mehlschwalbe (Delichon urbica) enthielten drei spezifische Ektoparasitenarten in unterschiedlicher Dichte. Pro nest fanden sich von der Mehlschwalbenlausfliege (Stenepteryx hirundinis) 0-12 Eier, von der Mehlschwalbenwanze (Oeciacus hirundinis)195-1104 Larven und Imagines und vom Mehlschwalbenfloh (Ceratophyllus hirundinis)9-135 Imagines. Zwischen 1. Oktober und dem 9.-16. mai des folgenden Jahres gab es im Durchschnitt nur einen geringfuegigen Rueckgang der Anzahl der Wanzen, waehrend die Abundanz adulter Floehe deutlich zunahm. Die Parasitendichte schwankte zwischen verschiedenen Fundorten und selbst innerhalb einer Nestreihe erheblich. In den am staerksten mit Parasiten belasteten Nestern ist eine erfolgreiche Aufzucht der Jungtiere durch die Mehlschwalben unwahrscheinlich. Die Hoehe der Parasitenlast koennte die Wahl der Schwalbenzwischen der Nutzung vorjaehriger Nester oder dem Ausbau aelterer nester wesentlich beeinflussen.
Preschool age is a biological stage of intensive longitudinal growth with high plasticity of the growing body and of body postures. It is the period where children learn to persist in a sitting posture for a longer time and to use furniture like chairs or other body supporting systems. The growing body shows a special sensitivity for the manifestation of inappropriate postures. In this study the development of body measurements and sitting behaviour of preschool age children is investigated as a precondition for an optimal adjustment of seats and desks to the growing body. Accordingly to the instructions of Knußmann (1988) and Jürgens (1988) 6 body measurements were taken from 122 German children aged 3 to 7 years from Potsdam, Province Brandenburg. Additionally, every child was videotaped for 10 minutes while crayoning in a sitting position of its own choice using a chair and a desk. To analyse the tapes, the software Noldus Observer was used and examined, picture by picture, to define the different types of sitting postures as well as the duration of persistence in a posture and the number of changes of postures. The used chairs and desks were also measured. Furthermore, the data of the furniture guideline DIN ISO 5970 (DIN, 1981), which regulates the dimensions of furniture for sitting in educational institutions, were compared with the results of the body measurements and with the dimensions of the furniture used by the children.
Modeling the impacts of grazing land management on land-use change for the Jordan River region
(2008)
In this article, we describe a simulation method for investigating the impacts of different grazing land management strategies on the productivity of (semi-)natural vegetation and the resulting feedback on land-use change. In a first application, we analyze the effects of sustainable and intensive grazing land management in the Jordan River region. For this purpose, we adapt and use the regional version of the spatially explicit modeling framework LandSHIFT. Our simulation experiments indicate that the modeled feedback mechanism has a strong effect on the spatial extent of grazing land. Consequently, the results of our study underline that the inclusion of such feedback mechanisms in land- use models can help to represent and analyze the complex interactions between humans and the environment in a more differentiated and realistic way, but they also identify the demand for more detailed empirical data on grazing land degradation in order to further improve the explanatory power of the model.
A method for construction of biosensors with membranous cytochrome P450 isoenzymes was developed based on clay/ detergent/protein mixed films. Thin films of sodium montmorillonite colloid with incorporated cytochrome P450 2134 (CYP2B4) with nonionic detergent were prepared on glassy carbon electrodes. The modified electrodes were electrochemically characterized, and bio-electrocatalytic reactions were followed. CYP2B4 can be reduced fast on clay- modified glassy carbon electrodes in the presence of the nonionic detergent Tween 80. In anaerobic solutions, reversible oxidation and reduction is obtained with a formal potential between -0.292 and - 0.305 V vs Ag/AgCl 1 M KCl depending on the preparation of the biosensor. In air-saturated solution, bio-electrocatalytic reduction currents can be obtained with the CYP2B4-modified electrode on addition of typical substrates such as aminopyrine and benzphetamine. This reaction was suppressed when methyrapone, an inhibitor of P450 reactions, was present. Measurement of product formation also indicates the bioelectrocatialysis by CYP2B4
Regional variation in nitrogen (N) deposition increases plant productivity and decreases species diversity, but landscape- or local -scale influences on N deposition are less well-known. Using ion-exchange resin, we measured variation of N deposition and soil N availability within Elk Island National Park in the ecotone between grassland and boreal forest in western Canada. The park receives regionally high amounts of atmospheric N deposition (22 kg ha(-1) yr(- 1)). N deposition was on average higher ton clay-rich luvisols than on brunisols, and areas burned 1-15 years previously received more atmospheric N than unburned sites. We suggest that the effects of previous fires and soil type on deposition rate act through differences in canopy structure. The magnitude of these effects varied with the presence of ungulate grazers (bison, moose, elk) and vegetation type (forest, shrubland, grassland). Available soil N (ammonium and nitrate) was higher in burned than unburned sites in the absence of grazing, suggesting an effect of deposition. On grazed sites, differences between fire treatments were small, presumably because the removal of biomass by grazers reduced the effect of fire. Aspen invades native grassland in this region, and our results suggest that fire without grazing might reinforce the expansion of forest into grassland facilitated by N deposition
Bushbuck (Tragelaphus scriptus) often deposit faeces at specific localised defecation sites (LDS). We tested whether LDS have a function in the context of parasite avoidance. In a population of bushbuck in Queen Elizabeth National Park, Uganda, seven radio-collared individuals were observed. We recorded feeding behaviour inside and outside LDS. Furthermore, pasture contamination with gastro-intestinal tract parasites inside and outside LDS was examined. There were significant differences between the expected and the observed feeding rates inside LDS, but, contrary to our prediction, the bushbuck increased their feeding rate inside LDS. There was no significant difference in the parasite contamination of pastures inside and outside LDS. We discuss the hypothesis that LDS mainly serve a social function in bushbuck communities, whereas parasite avoidance seems to play a minor or no role
Modelling the competitiveness of clonal plants by complementary analytical and simulation approaches
(1999)
Untersuchungen zur Entstehung morphogenetisch unterschiedlicher Kallustypen bei Beta vulgaris L.
(1992)
Pflanzenfamilien
(1993)
Vorwort, Einleitung
(1993)
Pflanzenfamilien
(1993)
Samenpflanzen
(1993)
Pflanzenfamilien
(1993)
Samenpflanzen
(1993)
Samenpflanzen
(1993)
Conformational states and substates of cytochrome P450cam - insight in protein dynamics and folding
(1994)
Untersuchungen zum mikrobiellen Abbau chlorierter Kohlenwasserstoffe am Beispiel von DDT und Lindan
(1994)
Three-dimensional organization of endoplasmatic reticulum in the ventral photoreceptors of Limulus
(1994)
Biosensoren
(1994)