215 research outputs found
“The colour of words. An analysis of the Gospel of John. From ‘social death’ to freedom, in the household”
No full textIn the text of John, the deep social reality of slavery, especially of the domestic one, comes to the surface. It is a widespread and influential reality that the Gospel of John seems to know very well. Its terminology demonstrates a knowledge of the actual functions of the slaves and of the forms of relationships that bind them to their masters. The author shows capacity in the symbolic use of the slave terminology and is able to adapt it to his project
The Ecological Importance of Amphipod–Parasite Associations for Aquatic Ecosystems
No full textAmphipods are a key component of aquatic ecosystems due to their distribution, abundance and ecological role. They also serve as hosts for many micro- and macro-parasites. The importance of parasites and the necessity to include them in ecological studies has been increasingly recognized in the last two decades by ecologists and conservation biologists. Parasites are able to alter survival, growth, feeding, mobility, mating, fecundity and stressors’ response of their amphipod hosts. In addition to their modulating effects on host population size and dynamics, parasites affect community structure and food webs in different ways: by increasing the susceptibility of amphipods to predation, by quantitatively and qualitatively changing the host diet, and by modifying competitive interactions. Human-induced stressors such as climate change, pollution and species introduction that affect host–parasite equilibrium, may enhance or reduce the infection effects on hosts and ecosystems. The present review illustrates the importance of parasites for ecosystem processes using examples from aquatic environments and amphipods as a host group. As seen from the literature, amphipod–parasite systems are likely a key component of ecological processes, but more quantitative data from natural populations and field evidence are necessary to support the results obtained by experimental research
Corrigendum to “Overlapping and distinct brain regions involved in estimating the spatial position of numerical and non-numerical magnitudes: An fMRI study” [Neuropsychologia 51(5) (2013) 979–989]
No full textOverlapping and distinct brain regions involved in estimating the spatial position of numerical and non-numerical magnitudes: An fMRI study
No full textHow are numerical and non-numerical magnitudes processed in the brain? Brain imaging research, primarily using comparison paradigms (i.e. judging which of two magnitudes is larger),. has provided strong evidence demonstrating that the intraparietal sulcus (IFS) is a key region for processing both numerical (e.g. Arabic numerals, arrays of dots) and non-numerical magnitudes (e.g. height, brightness). These studies have suggested that there is both activation overlap and segregation in the brain regions involved in processing different dimensions of magnitude. In the present functional Magnetic Resonance Imaging (fMRI) study, we extended this line of investigation by probing the brain mechanisms underlying the mapping of numerical (Arabic numerals) and non-numerical magnitudes (brightness levels) onto a number line. Consistent with previous studies the present results revealed that number and brightness estimation was associated with overlapping activation within right lateralized areas of the posterior IFS. In addition, the contrast between number and brightness estimation revealed that bilateral anterior regions of the IFS are specifically involved in the process of estimating the position of symbolic numbers onto a number line. Furthermore, we found a significant influence of landmark reference points (0, 50 and 100) on brain activation in the right IFS for number estimation only. No regions were found to be specifically associated with brightness estimation. The results of this study reveal that the estimation of both numerical and non-numerical magnitude are associated with the engagement of a right lateralized magnitude system, but that symbolic number estimation is associated with additional engagement of bilateral regions of the anterior IPS. (C) 2013 Elsevier Ltd. All rights reserved
Overlapping and distinct brain regions involved in estimating the spatial position of numerical and non-numerical magnitudes: An fMRI study
No full textThe left intraparietal sulcus adapts to symbolic number in both the visual and auditory modalities: Evidence from fMRI
No full textA growing body of evidence from functional Magnetic Resonance Imaging adaptation (fMRIa) has implicated the left intraparietal sulcus (IPS) as a crucial brain region representing the semantic of number symbols. However, it is currently unknown to what extent the left IPS brain activity can be generalized across modalities (e.g., Arabic digits and spoken number words) and how robust and reproducible numerical adaptation effects are. In two separate fMRIa experiments we habituated the brain response of 20 native English-speaking (Experiment 1) and 34 native German-speaking (Experiment 2) adults to Arabic digits or spoken number words. Consistent with previous findings, experiment 1 revealed numerical ratio dependent adaptation to Arabic numerals in the left IPS using both conventional and cortex-based alignment techniques. Experiment 2 revealed numerical ratio dependent signal recovery in the left IPS following adaptation to both Arabic numerals and spoken number words using both conventional and cortex-based alignment techniques. Together, these findings suggest that the left IPS is involved in symbolic number processing across modalities
Investigations on life-cycle and host specificity of the Malacosporea (Myxozoa)
No full textEs ist bekannt, dass Parasiten der Klasse Malacosporea (Myxozoa) sowohl Fische als auch Süßwasserbryozoen infizieren, allerdings wurden die meisten Malacosporea bisher nur im Wirbellosenwirt beschrieben. Kenntnisse über Wirtsspektrum, Übertragungsmechanismen und innerartliche Unterschiede in der Empfänglichkeit gegenüber Malacosporea-Erregern sind bislang rar. Daher war es das Ziel dieser Dissertation Biologie und Lebenszyklen einiger Malacosporea-Parasiten intensiver zu untersuchen.
Die Übertragung von T. brysalmonae auf Bryozoen war bisher nur mittels infizierter Bachforellen (Salmo trutta) erfolgreich. Daher wurde untersucht, ob neben Bachforellen möglicherweise andere Fischarten geeignete Wirte für T. bryosalmonae darstellen. Es konnte nachgewiesen werden, dass auch Bachsaiblinge (Salvelinus fontinalis) den Parasiten auf Bryozoen übertragen können. Im Gegensatz dazu lösten infizierte Regenbogenforellen (Oncorhynchus mykiss) und Äschen (Thymallus thymallus) keine Infektion bei Letzteren aus. Hechte konnten in diesen Versuchen nicht infiziert werden.
Über die Anheftung und die Penetration von Sporen der Malacosporea bei Kontakt mit dem Fischwirt sind nur wenige Details bekannt. Offensichtlich dringen die Sporoplasmen dieser Sporen in die Epithelien des Wirts mittels amöboider Bewegungen ein. Zudem deuten die ultrasturkturellen Untersuchungen darauf hin, dass die Kiemen die Haupteintrittspforte für diesen Parasiten sind.
Die Variabilität der Empfänglichkeit von vier Regenbogenforellenstämme und Bachforellen gegenüber T. bryosalmonae wurde mittels quantitativer real-time PCR untersucht. Dabei erwiesen sich Bachforellen als empfänglicher als Regenbogenforellen. In der Anfangsphase des Experiments wiesen zwei der Regenbogenforellenstämme eine geringere Parasitenlast auf als alle anderen Gruppen, allerdings vermehrten sich bei diesen beiden Stämmen die Parasiten schneller, was am letzten Entnahmezeitpunkt letztlich zur Angleichung der relativen Infektionsrate bei allen Stämmen führte. Mittels Immunhistochemie konnten Stadien von T. bryosalmonae in histologischen Schnitten detektiert werden, jedoch war ihre Anzahl gering.
Im Gegensatz zu T. bryosalmonae sind die Kenntnisse zu den Lebenszyklen von Buddenbrockia spp. unvollständig und alle bekannten Arten dieser Gattung sind lediglich als Stadien im Bryozoenwirt beschrieben. In der vorliegenden Arbeit konnten bisher unbekannte Infektionen in den Nieren von Karpfen (Cyprinus carpio) und Elritzen (Phoxinus phoxinus) nachgewiesen werden. Der Elritzenparasit konnte als Buddenbrockia plumatellae identifiziert werden, wohingegen es sich bei dem Karpfenparasiten höchst wahrscheinlich um eine unbeschriebene Art handelt. Die Kohabitation von im Labor gezüchteten Bryozoen mit infizierten Karpfen führte nicht zu einem offenen Ausbruch der Infektion.
Die Ergebnisse der vorliegenden Arbeit haben in entscheidendem Maße die Kenntnisse über das Wirtsspektrum und die Lebenszyklen von verschiedenen, auch mutmaßlich neuen, Malacosporea-Arten erweitert. Ebenso ergaben sich Hinweise auf Resistenzunterschiede verschiedener Regenbogenforellenstämme gegenüber T. bryosalmonae. Untersuchungen zu Aspekten der Invasion von T. bryosalmonae in den Fisch trugen entscheidend zur weiteren Aufklärung der frühen Infektionsprozesse der Malacosporea bei.The class Malacosporea is the most enigmatic, and probably the basal group of the unique metazoan phylum Myxozoa. They are known to parasitize fish and freshwater bryozoans, but still, most malacosporeans were only described from the invertebrate host. A complete life-cycle is merely known for Tetracapsuloides bryosalmonae, the parasite causing proliferative kidney disease in salmonid fish. Knowledge about host range, transmission mechanisms and intraspecific differences in resistance against malacosporean pathogens remains scarce hitherto. Therefore, the aim of the present thesis was to investigate the biology and the life-cycles of some malacosporean parasites in more detail. Firstly, the necessary culture of freshwater bryozoans to keep the life-cycle of these parasites in the laboratory could be established in the course of this study. Spores obtained from cultured bryozoans infected with malacosporeans thus enabled laboratory transmission experiments.
It is well known that most salmonid species are susceptible to T. bryosalmonae-infection, but even in Northern pike (Esox lucius) developmental stages similar to this parasite were described previously. Nevertheless, transmission of this parasite to bryozoans was only achieved with infected brown trout (Salmo trutta). To find out whether other teleosts besides brown trout may also be suitable hosts for T. bryosalmonae, infection experiments with different fish species were conducted in the present study. By cohabitation of T. bryosalmonae-infected fish and laboratory raised bryozoans it was demonstrated that also brook trout (Salvelinus fontinalis) transmitted the disease to bryozoans. In contrast, infected rainbow trout (Oncorhynchus mykiss) and grayling (Thymallus thymallus) did not cause infection of the latter. Peculiarly, pike did not become infected at all in this experiment.
For infection of such a wide range of fish species, a general mode of host invasion is necessary. Virtually no details about attachment and penetration of malacosporean spores encountering the fish host were known. To characterize these life-cycle stages ultra-structurally, infection trials and in vitro experiments with T. bryosalmonae actinospores were conducted. In vitro activation experiments, light microscopy and scanning electron microscopy (SEM) showed that sporoplasms of these spores penetrate host epithelia by means of amoeboid movement. Additionally, ultrastructural examinations indicated that the gills are main entry site for this parasite. Upon contact, the spores seemed to impair the gill epithelium to allow the entry of the sporoplasm at these sites. After penetration, the parasite is exposed to the immune system of the host, so the number of stages that enter and the intensity of the host response against the parasite will influence its development and multiplication. This variability in susceptibility was addressed in the present study, as reliable data about intra-specific differences in the response of fish to malacosporean infections was lacking up to this point. Four rainbow trout strains and brown trout were infected with T. bryosalmonae and infection intensity was monitored. According to results from quantitative real-time-PCR analysis, brown trout were more susceptible than rainbow trout. Two rainbow trout strains showed lower relative parasite load than all other groups early during the experiment, but parasites multiplied faster in these strains, resulting in an equal level of relative infection rate for all strains upon final sampling. T. bryosalmonae-stages were found stained by immuno-histochemistry in histological sections although their number was low, unfortunately impeding quantitative evaluation of parasite load.
In contrast to T. bryosalmonae, knowledge of life-cycles of Buddenbrockia spp. was incomplete and all known species of this genus were described as stages in bryozoan hosts. In this study, cohabitation challenges with bryozoans containing the peculiar worm-like malaco-sporean stages and fish resulted in novel infections detected in kidneys of common carp (Cyprinus carpio) and minnow (Phoxinus phoxinus). Sequence comparison of 18S rDNA identified the parasite in minnows as Buddenbrockia plumatellae, while the carp infecting malacosporean is very likely a new species. Light and electron-microscopy of kidney samples of infected minnows and carp revealed parasite stages in the kidney tubules. Only single parasite cells were observed in minnow, while in carp, multicellular sporogonic stages were found in sections of kidney tubules. Cohabitation of laboratory raised bryozoans with infected carp did not yield in overt infection. Therefore, the complete life-cycle of this parasite has yet to be established. Phylogenetic analysis of the Buddenbrockia spp. known to date sub-stantiated the split of the B. plumatellae-clade into two lineages, but could not fully clarify the placement of the carp-infecting malacosporean.
The results of this thesis fundamentally increased the knowledge on the range of compatible hosts and life-cycles of different, even putatively new, malacosporean species. Also, indi-cations for differential resistance of rainbow trout strains to T. bryosalmonae were found. Investigations on aspects of invasion of fish by T. bryosalmonae spores further clarified the early infection process of malacosporeans
Author Correction: Mechanisms of simultaneous linear and nonlinear computations at the mammalian cone photoreceptor synapse
No full textWem gehören die Medien? Oder doch: Was gehört den Medien?
No full textWem gehören die Medien in Deutschland? Das wollten drei Österreicher wissen. Einer von ihnen, Hendrik Theine, war zu Besuch bei Medienrealität Live und hat die Studie mitgebracht. Die Zuschauer reagierten auf seinen Vortrag teils mit Fassungslosigkeit und artikulierten einem klaren Wunsch nach Veränderung. Benjamin Ferschli, Daniel Grabner, Hendrik Theine: Zur Politischen Ökonomie der Medien in Deutschland. München: isw – sozial-ökologische Wirtschaftsforschung e.V. 2019. Medienrealität Podc..
- …
