Stocking of captive-bred fish can cause long-term population decline and gene pool replacement: predictions from a population dynamics model incorporating density-dependent mortality

Releasing captive-bred fish into natural environments (stocking) is common in fisheries worldwide. Although stocking is believed to have a positive effect on fish abundance over the short term, little is known about the long-term consequences of recurrent stocking and its influence on natural populations. In fact, there are growing concerns that genetically maladapted captive-bred fish can eventually reduce the abundance of natural population. In this study, we develop a simple model to quantitatively investigate the condition under which recurrent stocking has long-term effects on the natural population. Using a population dynamics model that takes into account a density-dependent recruitment, a gene responsible for the fitness difference between wild and captive-bred fish, and hybridization between them, we show that there is little or no contribution of recurrent stocking to the stock enhancement without a replacement of the wild gene pool by the captive-bred gene pool. The model further predicted that stocking of an intermediate level causes a reduction, rather than enhancement, of population size over the long term. The population decline due to stocking was attributed to the fitness disadvantage of captive-bred fish and strong overcompensation at recruitment stage. These results suggest that it would be difficult to simultaneously attain population size recovery and conservation of the local gene pool when captive-bred fish have fitness disadvantage in the wild, although caution is needed when applying the predictions from the simplified model to a specific species or population.

Comparative Czech and Polish Perspectives and Policies on the Eastern Enlargement of the EU and the Prominence of the German Factor

With the end of the Cold War, which for central and eastern Europe in many respects meant the real political end to the Second World War, Germany regained its central position in the region. The Federal Republic quickly established itself as a major political and economic partner for both the Czech Republic and Poland. More importantly, due to its support for the idea of EU and NATO enlargement. Germany also became the most active western advocate of the Czech and Polish 'return to Europe'. The question remains, however, of whether Germany's relations with Poland and the Czech Republic can mature into a close axis like that enjoyed between Paris and Bonn/Berlin, or whether they will continue to develop along the lines of 'strategic congruence' but 'emotional mistrust and reserve'. The research here looked at three aspects of this question. First it considered the idea of a link between perceptions of Germany and broader considerations of European integration in Poland and the Czech Republic and outlined the ways in which Germany has motivated Czech and Polish activities and policies on EU membership. The team then focused upon on-going Czech and Polish EU integration strategies and sought to identify the actual ways in which Germany's advocacy of EU enlargement in manifest in cooperation 'on the ground'. The group concluded by considering prospects for Czech/German and Polish/German cooperation in the context of the enlarged European Union.

Trends and Expertise Exchange within Rapid Manufacturing in Europe

Rapid Manufacturing (RM) umfasst den Begriff der direkten und wirtschaftlichen Bauteilherstellung des Serienprodukts aus 3D-Daten. Die Hauptvorteile sind u.a. das Wegfallen von Werkzeugen und eine Designfreiheit in der Produktentwicklung, die noch vor wenigen Jahren undenkbar war. Wenngleich heute eine Vielzahl von Werkstoffen im Kunststoff- und Metallbereich einsetzbar sind, konzentriert sich die Verbreitung des RM allerdings auf besondere Technologie- und Wirtschaftszweige, aufgrund mangelnder Erfahrungswerte, teilweise abweichender Werkstoffeigenschaften, fehlender Standards und ungeeigneter Testmethoden. In der Praxis sind Ingenieure und Techniker stark darauf bedacht, auf etablierte Abläufe und Standards zurückzugreifen. Es ist daher schwer einen geeigneten RM-Prozess aufzubauen, wo wichtige Eingangsgrößen meist unbekannt sind. In diesem Bericht wird beschrieben, welche Informationskanäle es innerhalb Europas zum Thema RM gibt und welche Hochschulen und Forschungszentren Aktivitäten aufweisen. Darüber hinaus werden Anwendungsfelder des RM aufgeführt, die über die bekannten Anwendungsfelder hinaus gehen. Dazu gehören Anwendungen im Bereich der Elektrotechnik, Raumfahrtinstrumentation und der Mode. Obwohl nicht alle Anwendungen des RM in diesem Bericht aufgeführt werden, sind einige Schlüsselinformationen im Bereich innovativer Anwendungen von RM enthalten.

Cell population, viability, and some key immunomodulatory molecules in different milk somatic cell samples in dairy cows

Immune cells in the milk are most important in combating pathogens that invade the mammary gland. This study investigated the immune competence and viability of somatic milk cells that are already resident in milk and udders free of infection. Cells were studied in freshly removed milk to simulate conditions in the udder. Effects of incubation, cell preparation, and immunological stimulation with 0.5 mug/ml lipopolysaccharide (LPS) from Escherichia coli were analysed. Viability and differential counts of milk cells between high and low somatic cell count (SCC) quarters, and cisternal and alveolar milk with and without LPS stimulation were compared. Incubation and preparation of cells caused a cell loss which further increased with time independently of SCC and milk fraction. The viability of these cells was stable until 3 h post incubation and decreased until 6 h. Cell populations differed between both investigations, but did not change during the course of the experiment. mRNA expression of immune and apoptosis factors of the cells, measured by qPCR, did not change substantially: mRNA expression of caspase 3, Toll like receptor 4, and GM-CSF did not change, whereas the expression of the death receptor Fas/APO-1 (CD95), lactoferrin and lysozyme was decreased at 6 h. Cyclooxygenase-2 and TNF-alpha mRNA expression were decreased after 6 h of LPS treatment. In comparison with other studies in vivo or in vitro (in cell culture), in this study where cells are studied ex vivo (removed from the udder but kept in their natural environment, the milk) resident milk cells seem to be more vulnerable, less viable, less able to respond to stimulation, and thus less immune competent compared with cells that have freshly migrated from blood into milk after pathogen stimulation. The cell viability and differential cell count differed between high- and low-SCC milk and between cisternal and alveolar milk depending on the individual cow. In conclusion, the results support the view that for a most effective defence against invading pathogens the mammary gland is reliant on the recruitment of fresh immune cells from the blood.