Stable isotope fractionation of selenium by biomethylation in soil

Selen ist in geringen Mengen ein essentielles Nährelement, das aber in höheren Gehalten toxisch wird. Der Se-Kreislauf in der Umwelt ist eng mit Redoxreaktionen wie der Reduktion von Se-Oxyanionen zu Methylselenid verknüpft. Flüchtige Methylselenide sind weit verbreitet und stellen einen wichtigen Se-Fluss in der Umwelt dar. Das übergeordnete Ziel meiner Dissertation war, die Stabilisotopenfraktionierung von Se durch Biomethylierung verschiedener oxidierter Se-Spezies (Se[IV] und Se[VI]) im Boden aufzuklären. Zunächst wurde eine Methode entwickelt, die es erlaubte flüchte Methylselenide quantitativ zurückzuhalten. Es zeigte sich, dass alkalische Peroxid-Lösung dafür geeignet war. Mit alkalischer Peroxid-Lösung wurde eine Wiederfindung von 95,6 ± Standardabweichung 5,4% in Verflüchtigungsexperimenten mit Methylselenid-Standards erreicht. Bei Einsatz von alkalischer Peroxid-Lösung in geschlossenen Mikrokosmos-Experimenten kam es zu keinen Se-Verlusten und ausgeglichenen Se-Isotopenbilanzen. Die massengewichteten δ82/76Se-Werte lagen für Se(IV) und Se(VI) am Ende der Mikrokosmos-Inkubationen bei -0,31 ± 0,05‰ (n = 3) und -0,76 ± 0,07‰ (n = 3) verglichen mit -0,20 ± 0,05‰ und -0,69 ± 0,07‰ im jeweils zugegebenen Se. Im zweiten Teil meiner Dissertation wurde die Pilzart Alternaria alternata mit Se(VI) und Se(IV) in geschlossenen Mikrokosmen für 11-15 und Se(IV) zusätzlich für 3-5 Tage bei 30°C inkubiert. In 11-15 Tagen wurden 2,9-11% des Se(VI) und 21-29% des Se(IV) und in 3-5 Tagen, 3-5% des Se(IV) methyliert. Die anfänglichen δ82/76Se-Werte von Se(VI) und Se(IV) lagen bei -0,69 ± 0,07‰, und -0,20 ± 0,05‰. Die δ82/76Se-Werte der Methylselenide unterschieden sich nach 11-15 Tagen Inkubation signifikant zwischen Se(VI) (-3,97 bis -3,25 ‰) und Se(IV) (-1,44 bis -0,16‰) als Quellen. Die δ82/76Se-Werte der Methylselenide zeigen also die Quellen der Biomethylierung von Se an. Die kürzere Inkubation von Se(IV) für 3-5 Tage führte zu einer ausgeprägten Se-Isotopenfraktonierung von mindestens -6‰, bevor ein Fließgleichgewicht erreicht wurde. Im dritten Teil bestimmte ich die Bindungsformen von Se mit drei operativ definierten sequentiellen Extraktionen und die δ82/76S-Werte des gesamten Selens in zehn urbanen Oberböden mit 0,09-0,52 mg/kg Se, die fünf verschiedene Landnutzungstypen repräsentierten (Überschwemmungsgrünland, Garten, Park, Straßenrand und Wald). Nur ein kleiner Teil des Seleniums lag in austauschbarer und damit direkt bioverfügbarer und in residualer, wenig reaktiver Form vor. Das meiste Se war an die organische Substanz und Fe-(Hydr-)Oxide gebunden (42-77% des gesamten Selens). Der mittlere δ82/76Se-Wert des gesamten Selens in den Oberböden lag mit -0,03 ± 0,38‰ nahe beim Mittelwert der gesamten Erde. Geringfügig niedrigere Se-Isotopensignale von -0,59 bis -0,35‰ v.a. in Waldböden und geringfügig höhere von 0,26 to 0,45‰ in Überschwemmungsgrünland wurden vermutlich durch Boden-Pflanze-Recycling und Se-Kontaminationen durch das Flusswasser verursacht. Der vierte Teil umfasste ein “Natural Attenuation”-Experiment und Mikrokosmos-Inkubationen von Bodenproben mit A. alternata. Die Equilibrierung von zum Boden gegebenem Se(IV) und Se(VI) für drei Tage führte zu abnehmenden wasserlöslichen Se-Gehalten um 32-44% bzw. 8-14, die mit kleinen Isotopenfraktionierung (ε = -0,045 bis -0,12 ‰ and -0,05 to -0,07‰ verbunden waren. In zwei der inkubierten Böden mit mäßig sauren pH-Werten wurden zwischen 9,1 und 30% des zugefügten Se(IV) und 1,7% des zugefügten Se(VI) methyliert während in einem stark sauren Boden keine Methylierung auftrat. Das aus Se(IV) entstandene Methylselenid war deutlich gegenüber dem zugegebenen Se-Standard (0,20‰) an 82Se verarmt (δ82/76Se = -3,3 bis -4,5‰). Meine Ergebnisse zeigen, dass die stabilen Isotopenverhältnisse von Se neue Einblicke in Se-Transformationsprozesse erlauben.rn

Charakterisierung der Latenz des murinen Cytomegalovirus in vivo

Die primäre, produktive Cytomegalovirus (CMV)-Infektion wird im immunkompetenten Patienten effizient durch antivirale CD8+ T-Zellen kontrolliert. Das virale Genom besitzt jedoch die Fähigkeit, in einem nicht replikativen, Latenz genannten Zustand, in gewissen Zelltypen zu persistieren, ohne dass infektiöse Nachkommenviren produziert werden. Die molekularen Mechanismen, welche der Etablierung und Aufrechterhaltung der Latenz zugrundeliegen, sind noch weitestgehend unbekannt. Es gibt Hinweise darauf, dass zelluläre Verteidigungsmechanismen die Zirkularisierung und Chromatinisierung viraler Genome hervorrufen und dadurch die virale Genexpression größtenteils verhindert wird (Marks & Spector, 1984; Reeves et al., 2006).rnAllerdings liegen die Genome nicht in einem komplett inaktiven Zustand vor. Vielmehr konnte für das murine CMV (mCMV) bereits die sporadische Transkription der Gene ie1 und ie2 während der Latenz nachgewiesen werden (Kurz et al., 1999; Grzimek et al., 2001).rnIn der vorliegenden Arbeit wurde zum ersten Mal eine umfassende in vivo Latenz-Analyse zur Charakterisierung der viralen Transkription in einer Kinetik anhand der alle drei kinetischen Klassen repräsentierenden Transkripte IE1, IE3, E1, m164, M105 und M86 vorgenommen.rnNach Latenz-Etablierung, verifiziert durch Abwesenheit von infektiösem Virus, konnten alle getesteten Transkripte in der Lunge quantifiziert werden. Interessanterweise war die transkriptionelle Aktivität zu keinem Analyse-Zeitpunkt mit der klassischen IE-E-L-Kinetik der produktiven Infektion kompatibel. Stattdessen lag eine stochastische Transkript-Expression vor, deren Aktivität mit voranschreitender Zeit immer weiter abnahm.rnWährend der Latenz exprimierte Transkripte, die für antigene Peptide kodieren, können infizierte Zellen für das Immunsystem sichtbar machen, was zu einer fortwährenden Restimulation des memory T-Zell-pools führen würde. Durch zeitgleiche Analyse der Transkript-Expression, sowie der Frequenzen Epitop-spezifischer CD8+ T-Zellen während der Latenz (IE1, m164, M105), wurde eine möglicher Zusammenhang zwischen der transkriptionellen Aktivität und der Expansion des memory T-Zell-pools untersucht. Die weitere Charakterisierung von Subpopulationen der Epitop-spezifischen CD8+ T-Zellen identifizierte die SLECs (short-lived-effector cells; CD127low CD62Llow KLRG1high) als die dominante Population in Lunge und Milz während der mCMV-Latenz.rnIn einem weiteren Teil der Arbeit sollte untersucht werden, ob IE-Genexpression zur Etablierung von Latenz notwendig ist. Mit Hilfe der Rekombinanten mCMV-Δie2-DTR, die die Gensequenz des Diphtherietoxin-Rezeptors (DTR) anstelle des Gens ie2 trägt, konnten infizierte, DTR exprimierende Zellen durch eine DT-Applikation konditional depletiert werden.rnIm latent infizierbaren Zelltyp der Leber, den LSECs (liver sinusoidal endothelial cells) wurde die virale Load durch 90-stündige DT–Applikation nach mCMV-Δie2-DTR Infektion auf das Level latent infizierter LSECs reduziert. Diese Daten sprechen für die Hypothese eines von Beginn an inaktiven Genoms, das keine IE-Genexpression zur Latenz-Etablierung benötigt. Zusätzlich stellt dieser Ansatz ein neues Tier-Modell zur Latenz-Etablierung dar. Verringerte Wartezeiten bis zur vollständigen Latenz-Etablierung, im Vergleich zum bisherigen Knochenmarktransplantations-Modell, könnten anfallende Tierhaltungskosten erheblich reduzieren und das Voranschreiten der Forschung beschleunigen.

Novel porphyrin amino acids as building blocks for artificial photosynthetic reaction centers : photoinduced energy and electron transfer

This thesis reports on the synthesis and characterisation of trans-(M)AB2C meso-substituted porphyrin amino acid esters (PAr) (M = 2H or Zn) with tunable electron donating and electron withdrawing Ar substituents at B positions (Ar = 4-C6H4OnBu, 4-C6H4OMe, 2,4,6-C6H2Me3, 4-C6H4Me, C6H5, 4-C6H4F, 4-C6H4CF3, C6F5). These porphyrins were used as key building blocks for photosynthetic LHC (LHC = light-harvesting antenna complex) and RC (RC = reaction center) model compounds.rnBased on free-base or zinc(II) porphyrin amino acid esters and porphyrin acids several amide linked free-base bis(porphyrins) PAr1-PAr2 (Ar1 = 2,4,6-C6H2Me3, C6F5 and Ar2 = 2,4,6-C6H2Me3, 4-C6H4F, 4-C6H4CF3, C6F5), mono metallated bis(porphyrin) PAr1-(Zn)PAr2 (Ar1 = 2,4,6-C6H2Me3 and Ar2 =4-C6H4F) and its doubly zincated complexes (Zn)PAr1-(Zn)PAr2 were prepared. In the fluorescence spectra of free-base bis(porphyrins) the porphyrin with the strongest electron donating power of Ar substituents at B positions is the light emitting unity. The emission of mono metallated bis(porphyrin) occurs only from the free-base porphyrin building block. This phenomenon is caused by an efficient energy transfer likely via the Dexter through-bond mechanism.rnLinking of anthraquinone (Q) as electron acceptor (A) to the N-terminus of porphyrin amino acid esters ((M)PAr) and aminoferrocene (Fc) as electron donor (D) to the C-terminus of the porphyrin resulting in Q-(M)PAr-Fc triads (M = 2H or Zn, Ar = 4-C6H4OnBu, 4-C6H4OMe, 2,4,6-C6H2Me3, 4-C6H4Me, C6H5, 4-C6H4F, 4-C6H4CF3, C6F5) with tunable electron density at the porphyrin chromophore. In these triads initial oxidative PET (Q←(M)PAr) and reductive PET ((M)PAr→Fc) (PET = photoinduced electron transfer) are possible. Both processes leads to an emission quenching of (M)PAr. The efficiency of the PET pathways occurring in the Marcus normal region is controlled by the specific porphyrin electron density.rnAmide-linked conjugates PAr-Fc (Ar = 2,4,6-C6H2Me3, C6F5) and Fmoc-Fc-PAr1 (N-Fmoc-Fc = N-Fmoc protected 1,1’-ferrocene amino acid; Ar1 = C6H5, 4-C6H4F, 4-C6H4CF3, C6F5) as well as hinges PAr2-Fc-PAr1 (Ar1 = C6H5, 4-C6H4F and Ar2 = 2,4,6-C6H2Me3) were studied with respect to the reductive PET. The PET driving force (−GET) in dyads increases with the increasing electron withdrawing character of Ar substituents. Additionally, intramolecular energy transfer between porphyrins PAr1 and PAr2 is feasible in the hinges via the Förster mechanism.rn

Mythos und Mathematik : Hermann Brochs Roman "Die Schuldlosen" und seine Essays

„Natürlich habe ich mich [...] unausgesetzt mit Mathematik beschäftigt, umso mehr als ich sie für meine erkenntnistheoretisch-philosophischen Studien brauchte, denn ohne Mathematik lässt sich kaum mehr philosophieren.“, schreibt Hermann Broch 1948, ein Schriftsteller, der ca. zehn Jahre zuvor von sich selbst sogar behauptete, das Mathematische sei eine seiner stärksten Begabungen.rnDiesem Hinweis, die Bedeutung der Mathematik für das Brochsche Werk näher zu untersuchen, wurde bis jetzt in der Forschung kaum Folge geleistet. Besonders in Bezug auf sein Spätwerk Die Schuldlosen fehlen solche Betrachtungen ganz, sie scheinen jedoch unentbehrlich für die Entschlüsselung dieses Romans zu sein, der oft zu Unrecht als Nebenarbeit abgewertet wurde, weil ihm „mit gängigen literaturwissenschaftlichen Kategorien […] nicht beizukommen ist“ (Koopmann, 1994). rnDa dieser Aspekt insbesondere mit Blick auf Die Schuldlosen ein Forschungsdesiderat darstellt, war das Ziel der vorliegenden Arbeit, Brochs mathematische Studien genauer nachzuvollziehen und vor diesem Hintergrund eine Neuperspektivierung der Schuldlosen zu leisten. Damit wird eine Grundlage geschaffen, die einen adäquaten Zugang zur Struktur dieses Romans eröffnet.rnDie vorliegende Arbeit ist in zwei Teile gegliedert. Nach einer Untersuchung von Brochs theoretischen Betrachtungen anhand ausgewählter Essays folgt die Interpretation der Schuldlosen aus diesem mathematischen Blickwinkel. Es wird deutlich, dass Brochs Poetik eng mit seinen mathematischen Anschauungen verquickt ist, und somit nachgewiesen, dass sich die spezielle Bauform des Romans wie auch seine besondere Form des Erzählens tatsächlich aus dem mathematischen Denken des Autors ableiten lassen. Broch nutzt insbesondere die mathematische Annäherung an das Unendliche für seine Versuche einer literarischen Erfassung der komplexen Wirklichkeit seiner Zeit. Dabei spielen nicht nur Elemente der fraktalen Geometrie eine zentrale Rolle, sondern auch Brochs eigener Hinweis, es handele sich „um eine Art Novellenroman“ (KW 13/1, 243). Denn tatsächlich ergibt sich aus den poetologischen Forderungen Brochs und ihren Umsetzungen im Roman die Gattung des Novellenromans, wie gezeigt wird. Dabei ist von besonderer Bedeutung, dass Broch dem Mythos eine ähnliche Rolle in der Literatur zuspricht wie der Mathematik in den Wissenschaften allgemein.rnMit seinem Roman Die Schuldlosen hat Hermann Broch Neuland betreten, indem er versuchte, durch seine mathematische Poetik die komplexe Wirklichkeit seiner Epoche abzubilden. Denn „die Ganzheit der Welt ist nicht erfaßbar, indem man deren Atome einzelweise einfängt, sondern nur, indem man deren Grundzüge und deren wesentliche – ja, man möchte sagen, deren mathematische Struktur aufzeigt“ (Broch).

Investigating strategies and indicators for sustainable campus: Comparison and synergies between University of Bologna and Delft University of Technology

Sustainable development is one of the biggest challenges of the twenty fist-century. Various university has begun the debate about the content of this concept and the ways in which to integrate it into their policy, organization and activities. Universities have a special responsibility to take over a leading position by demonstrating best practices that sustain and educate a sustainable society. For that reason universities have the opportunity to create the culture of sustainability for today’s student, and to set their expectations for how the world should be. This thesis aim at analyzing how Delft University of Technology and University of Bologna face the challenge of becoming a sustainable campus. In this context, both universities have been studied and analyzed following the International Sustainable Campus Network (ISCN) methodology that provides a common framework to formalize commitments and goals at campus level. In particular this work has been aimed to highlight which key performance indicators are essential to reach sustainability as a consequence the following aspects has been taken into consideration: energy use, water use, solid waste and recycling, carbon emission. Subsequently, in order to provide a better understanding of the current state of sustainability on University of Bologna and Delft University of Technology, and potential strategies to achieve the stated objective, a SWOT Analysis has been undertaken. Strengths, weaknesses, opportunities and threats have been shown to understand how the two universities can implement a synergy to improve each other. In the direction of framing a “Sustainable SWOT” has been considered the model proposed by People and Planet, so it has been necessary to evaluate important matters as for instance policy, investment, management, education and engagement. Regarding this, it has been fundamental to involve the main sustainability coordinators of the two universities, this has been achieved through a brainstorming session. Partnerships are key to the achievement of sustainability. The creation of a bridge between two universities aims to join forces and to create a new generation of talent. As a result, people can become able to support universities in the exchange of information, ideas, and best practices for achieving sustainable campus operations and integrating sustainability in research and teaching. For this purpose the project "SUCCESS" has been presented, the project aims to create an interactive European campus network that can be considered a strategic key player for sustainable campus innovation in Europe. Specifically, the main key performance indicators have been analyzed and the importance they have for the two universities and their strategic impact have been highlighted. For this reason, a survey was conducted with people who play crucial roles for sustainability within the two universities and they were asked to evaluate the KPIs of the project. This assessment has been relevant because has represented the foundation to develop a strategy to create a true collaboration.

Patterns of morphological changes and hybridization between sympatric whitefish morphs (Coregonus spp.) in a Swiss lake: a role for eutrophication?

Whitefish, genus Coregonus, show exceptional levels of phenotypic diversity with sympatric morphs occurring in numerous postglacial lakes in the northern hemisphere. Here, we studied the effects of human-induced eutrophication on sympatric whitefish morphs in the Swiss lake, Lake Thun. In particular, we addressed the questions whether eutrophication (i) induced hybridization between two ecologically divergent summer-spawning morphs through a loss of environmental heterogeneity, and (ii) induced rapid adaptive morphological changes through changes in the food web structure. Genetic analysis based on 11 microsatellite loci of 282 spawners revealed that the pelagic and the benthic morph represent highly distinct gene pools occurring at different relative proportions on all seven known spawning sites. Gill raker counts, a highly heritable trait, showed nearly discrete distributions for the two morphs. Multilocus genotypes characteristic of the pelagic morph had more gill rakers than genotypes characteristic of benthic morph. Using Bayesian methods, we found indications of recent but limited introgressive hybridization. Comparisons with historical gill raker data yielded median evolutionary rates of 0.24 haldanes and median selection intensities of 0.27 for this trait in both morphs for 1948-2004 suggesting rapid evolution through directional selection at this trait. However, phenotypic plasticity as an alternative explanation for this phenotypic change cannot be discarded. We hypothesize that both the temporal shifts in mean gill raker counts and the recent hybridization reflect responses to changes in the trophic state of the lake induced by pollution in the 1960s, which created novel selection pressures with respect to feeding niches and spawning site preferences.

Glycogen-rich pleomorphic xanthoastrocytoma with clear-cell features: confirmatory report of a rare variant with implications for differential diagnosis

Central nervous system space-occupying lesions with clear-cell features encompass a nosologically heterogeneous array, ranging from reactive histiocytic proliferations to neuroepithelial or meningothelial neoplasms of various grades and to metastases. In the face of such differential diagnostic breadth, recognizing cytoplasmic lucency as part of the morphological spectrum of some low grade gliomas will directly have an impact on patient care. We describe a prevailing clear-cell change in an epileptogenic left temporal pleomorphic xanthoastrocytoma surgically resected from a 36-year-old man. Mostly subarachnoid and focally calcified, the tumor was composed of fascicles of moderately atypical spindle cells with optically lucent cytoplasm that tended to intermingle with a desmoplastic mesh of reticulin fibers. Immunohistochemically, coexpression of S100 protein, vimentin, GFAP, and CD34 was noted. Conversely, neither punctate staining for EMA nor positivity for CD68 was seen. Mitotic activity was absent, and the MIB1 labeling index was 2-3% on average. Diastase-sensitive PAS-positive granula indicated clear-cell change to proceed from glycogen storage. Electron microscopy showed tumor cell cytoplasm to be largely obliterated by non-lysosomal-bound pools of glycogen, while hardly any fat vacuole was encountered. Neither ependymal-derived organelles nor annular lamellae suggesting oligodendroglial differentiation were detected. The latter differential diagnosis was further invalidated by lack of codeletion of chromosomal regions 1p36 and 19q13 on molecular genetic testing. By significantly interfering with pattern recognition as an implicit approach in histopathology, clear-cell change in pleomorphic xanthoastrocytoma is likely to suspend its status as a "classic", and to prompt more deductive differential diagnostic strategies to exclude look-alikes, especially clear-cell ependymoma and oligodendroglioma.

Restricted or severely hindered diffusion of intramyocellular lipids in human skeletal muscle shown by in vivo proton MR spectroscopy

Although magnetic resonance spectroscopy can be used as a unique tool to study molecular diffusion, it is rarely used to measure the diffusion properties of intramyocellular and extramyocellular lipids. Lipids have very low apparent diffusion coefficients (ADCs), which make these measurements difficult and necessitate strong diffusion gradients and long diffusion times. Consequence is that these measurements have inherently low signal-to-noise ratio and are prone to artifacts. The addition of physiological triggering and individual storage and processing of the spectra is seen to be a possible approach to maximize signal intensity and achieve high reproducibility of the experiments. Thus, the optimized measurement protocol was used to investigate the diffusion properties of lipids in human skeletal muscle in vivo. At a diffusion time of about 110 ms, intramyocellular lipids show a significantly lower ADC (2.0 × 10(-6) mm(2)/s, 95% confidence interval 1.10 × 10(-6) to 2.94 × 10(-6) mm(2)/s) than extramyocellular lipids (1.58 × 10(-5) mm(2)/s, 95% confidence interval 1.41 × 10(-5) to 1.75 × 10(-5) mm(2)/s). Because the chemical properties of both lipid pools can be assumed to be similar, the difference can only be attributed to restricted or severely hindered diffusion in the intramyocellular droplets.

Spatial and temporal variation in population genetic structure of wild Nile tilapia (Oreochromis niloticus) across Africa

Background: Reconstructing the evolutionary history of a species is challenging. It often depends not only on the past biogeographic and climatic events but also the contemporary and ecological factors, such as current connectivity and habitat heterogeneity. In fact, these factors might interact with each other and shape the current species distribution. However, to what extent the current population genetic structure reflects the past and the contemporary factors is largely unknown. Here we investigated spatio-temporal genetic structures of Nile tilapia (Oreochromis niloticus) populations, across their natural distribution in Africa. While its large biogeographic distribution can cause genetic differentiation at the paleo-biogeographic scales, its restricted dispersal capacity might induce a strong genetic structure at micro-geographic scales. Results: Using nine microsatellite loci and 350 samples from ten natural populations, we found the highest genetic differentiation among the three ichthyofaunal provinces and regions (Ethiopian, Nilotic and Sudano-Sahelian) (R(ST) = 0.38 - 0.69). This result suggests the predominant effect of paleo-geographic events at macro-geographic scale. In addition, intermediate divergences were found between rivers and lakes within the regions, presumably reflecting relatively recent interruptions of gene flow between hydrographic basins (R(ST) = 0.24 - 0.32). The lowest differentiations were observed among connected populations within a basin (R(ST) = 0.015 in the Volta basin). Comparison of temporal sample series revealed subtle changes in the gene pools in a few generations (F = 0 - 0.053). The estimated effective population sizes were 23 - 143 and the estimated migration rate was moderate (m similar to 0.094 - 0.097) in the Volta populations. Conclusions: This study revealed clear hierarchical patterns of the population genetic structuring of O. niloticus in Africa. The effects of paleo-geographic and climatic events were predominant at macro-geographic scale, and the significant effect of geographic connectivity was detected at micro-geographic scale. The estimated effective population size, the moderate level of dispersal and the rapid temporal change in genetic composition might reflect a potential effect of life history strategy on population dynamics. This hypothesis deserves further investigation. The dynamic pattern revealed at micro-geographic and temporal scales appears important from a genetic resource management as well as from a biodiversity conservation point of view.

Screening of Swiss hot spring resorts for potentially pathogenic free-living amoebae

Free-living amoebae (FLA) belonging to Acanthamoeba spp., Naegleria fowleri, Balamuthia mandrillaris, and Sappinia pedata are known to cause infections in humans and animals leading to severe brain pathologies. Worldwide, warm aquatic environments have been found to be suitable habitats for pathogenic FLA. The present study reports on screening for potentially pathogenic FLA in four hot spring resorts in Switzerland. Water samples were taken from water filtration units and from the pools, respectively. Amoebae isolated from samples taken during, or before, the filtration process were demonstrated to be morphologically and phylogenetically related to Stenoamoeba sp., Hartmannella vermiformis, Echinamoeba exundans, and Acanthamoeba healyi. With regard to the swimming pools, FLA were isolated only in one resort, and the isolate was identified as non-pathogenic and as related to E. exundans. Further investigations showed that the isolates morphologically and phylogenetically related to A. healyi displayed a pronounced thermotolerance, and exhibited a marked in vitro cytotoxicity upon 5-day exposure to murine L929 fibroblasts. Experimental intranasal infection of Rag2-immunodeficient mice with these isolates led to severe brain pathologies, and viable trophozoites were isolated from the nasal mucosa, brain tissue, and lungs post mortem. In summary, isolates related to A. healyi were suggestive of being potentially pathogenic to immunocompromised persons. However, the presence of these isolates was limited to the filtration units, and an effective threat for health can therefore be excluded.

Cardiac sodium channel NaV1.5 distribution in myocytes via interacting proteins: the multiple pool model

The cardiac sodium current (INa) is responsible for the rapid depolarization of cardiac cells, thus allowing for their contraction. It is also involved in regulating the duration of the cardiac action potential (AP) and propagation of the impulse throughout the myocardium. Cardiac INa is generated by the voltage-gated Na(+) channel, NaV1.5, a 2016-residue protein which forms the pore of the channel. Over the past years, hundreds of mutations in SCN5A, the human gene coding for NaV1.5, have been linked to many cardiac electrical disorders, including the congenital and acquired long QT syndrome, Brugada syndrome, conduction slowing, sick sinus syndrome, atrial fibrillation, and dilated cardiomyopathy. Similar to many membrane proteins, NaV1.5 has been found to be regulated by several interacting proteins. In some cases, these different proteins, which reside in distinct membrane compartments (i.e. lateral membrane vs. intercalated disks), have been shown to interact with the same regulatory domain of NaV1.5, thus suggesting that several pools of NaV1.5 channels may co-exist in cardiac cells. The aim of this review article is to summarize the recent works that demonstrate its interaction with regulatory proteins and illustrate the model that the sodium channel NaV1.5 resides in distinct and different pools in cardiac cells. This article is part of a Special Issue entitled: Cardiomyocyte Biology: Cardiac Pathways of Differentiation, Metabolism and Contraction.

Talents in Migration Processes in the Conditions of the Czech Republic of the Nineties

The transformation of the 1990s has had a bearing on the academic and scientific world, as is becoming increasingly obvious with the changing numbers of foreign students wishing to study in the Czech Republic and of Czech students wishing to study abroad, the virtual collapse of doctoral studies, and the rapidly increasing age of Czech academics (placed at 48 by official sources and at rather more by this research). At the same time there is an apparent lack of interest in analysing and understanding these trends, which Mr. Cermak terms an ostrich policy, although his research showed that academics are in fact both aware and concerned about them. The mid-1990s migration of talent to and from R+D in the Czech Republic is also reflected in the number of talented Czech students studying abroad, who represent the largest and most interesting group of actual and potential migrants. Mr. Cermak's study took the form of a Delphi enquiry participated in by 44 specialists, including experts in the problems of higher education and science policy from the Presidium of the Higher Education Council (n = 23), members of the Council's Science and Research Commission (n = 14), former and current managers of higher education authorities (n = 4) and selected participants of the longitudinal talent research (n = 3). Questions considered included the influence of continuing talent migration from domestic R+D on the efficiency of domestic higher education, the diversification of forms of the brain drain and their impact on other processes in society, the possibility of positive influence on the brain drain processes to minimise the risks it presents, and the use of the knowledge obtained about the brain drain. The study revealed a clear drop of interest in brain drain problems in higher education in the mid-1990s, which is probably related to the collapsed of Czech R+D in the field of talent education. The effects on this segment of the labour market appeared earlier, with a major migration wave in 1991-1993 which significantly "cleared" the area of scientific talent. In addition, prospective talents from the ranks of younger students have not been integrated into domestic R+D, leading to the increasing average age of those working in this field. "Talent scouting" tended to be oriented towards much younger individuals, even in some cases towards undergraduate students. The R+D institutions deprived of human resources considered as basic in a functional R+D system have lost much of their dynamism and so no longer attract not only domestic talent but also talent from other regions. As a result the public, including the mass media and political structures, have stopped regarding the support of domestic science as a priority. This is clear both among the young people who are important for the future development of R+D (support for the education of talented children has dropped), from the drop in the prestige of this area as a profession among university students, and from the lack of explicit support for R+D by any of the political parties. On the basis of his findings Mr. Cermak concludes that there is no basis for the belief that the brain drain will represent a positive force in stimulating the development of the open society. Migration data shows that the outflow of talent from the Czech Republic far exceeds the inflow, and that the latter is largely short-term. Not only has the number of returning Czech professors dropped to half of its level at the beginning of the 1990s, but they also tend to take up only short-term contracts and retain their foreign positions. Recruitment of scientific talent from other countries, including the Slovak Republic, is limited. Furthermore internal contacts between those already involved in R+D have been badly hit by economic pressures and institutional co-operation has dropped to a minimum. There have been few moves to counteract this situation, the only notable one being the Program 250, launched in 1996 with government support to try and attract younger (i.e. under 40) talent into R+D. Its resources are however limited and its effects have not so far been evaluated. The deficit of academic and scientific talent in the Czech Republic is increasing and two major directions of academic work are emerging. Classic higher education science based on the teaching process is declining, largely due to economic factors, while there is an increasing emphasis on special; ad hoc projects which cannot be related directly to teaching but are often interesting to specialists outside the Czech Republic. This is shown clearly by the increase in publishing and in participation in domestic and foreign grant projects, which often serve to supplement the otherwise low salaries in the higher education sector. This tend was also accelerated by the collapse of applied R+D in individual sectors of the national economy and by substantial cutbacks in the Czech Academy of Sciences, which formerly fostered such research. Some part of the output of this research can be used in the education system and its financial contribution does significantly affect the stability of the present staff, but Mr. Cermak sees it as generally unfavourable for the development of talent education. In addition, it has led to a certain resignation on the question of integration into international structures, due to the emphasis on short-term targets, commercial advantages and individualism rather than team work. At the same time, he admits that these developments reflect those in other areas of the transformation in the Czech Republic.