Approaches to Assess the Suitability of Zooplankton for Bioregenerative Life Support Systems

Future manned space exploration will send humans farther away from Earth than ever before (e.g., to Mars), leading to extended mission durations and thus to a higher demand for essentials such as food, water and oxygen. As resupplying these items from Earth is nearly impossible, aquatic bioregenerative life support systems (BLSS) appear to be a promising solution. Due to its central role in aquatic ecosystems, zooplankton could act as a key player in aquatic BLSS, linking oxygen liberating, autotrophic producers and higher trophic levels. However, prior to the utilization of BLSS in space, organisms proposed to inhabit these systems have to be studied thoroughly to evaluate any space-borne adverse traits, which may impede a proper function of the system. To investigate the impact of microgravity (μg), in particular, several platforms are available, providing μg periods ranging from seconds (Bremen drop tower and parabolic flights), to minutes (sounding rockets), up to even days and months (space flights and the International Space Station (ISS)). Furthermore, ground-based facilities, such as clinostats, enable the of candidate organisms to variable periods of simulated/functional μg. In this book chapter, research on zooplankton utilizing these methods is summarized

Observation of enhanced chiral asymmetries in the inner-shell photoionization of uniaxially oriented methyloxirane enantiomers

Most large molecules are chiral in their structure: they exist as two enantiomers, which are mirror images of each other. Whereas the rovibronic sublevels of two enantiomers are almost identical, it turns out that the photoelectric effect is sensitive to the absolute configuration of the ionized enantiomer - an effect termed Photoelectron Circular Dichroism (PECD). Our comprehensive study demonstrates that the origin of PECD can be found in the molecular frame electron emission pattern connecting PECD to other fundamental photophysical effects as the circular dichroism in angular distributions (CDAD). Accordingly, orienting a chiral molecule in space enhances the PECD by a factor of about 10

The localization and function of the calcium transporter in the inner ear of teleost fishes (Oreochromis mossambicus)

Die Schwerkraftwahrnehmung in Fischen erfolgt durch die Otolithenorgane im Innenohr. Diese Strukturen sind mit Endolymphe gefüllt und besitzen ein sensorisches Maculaepithel auf dem der Otolith, der sogenannte Schwerestein, aufliegt. Die Otolithen bestehen im Wesentlichen aus Calciumcarbonat, welches in eine Proteinmatrix eingebettet ist. Das Wachstum der Otolithen unterliegt einem diurnalen Rhythmus. Eine bislang noch nicht geklärte Frage ist, wie der Transport der zur Mineralisierung der Otolithen benötigten Calciumionen durch das sensorische Epithel in die Endolymphe erfolgt. Das Ziel dieser Arbeit war es, die Lokalisation und Funktion der Plasmamembran-Calcium ATPase (PMCA) als möglichen Kandidaten für den Calciumtransporter in den sensorischen Epithelien des Innenohrs von Oreochromis mossambicus im Hinblick auf die Biomineralisation der Otolithen zu untersuchen. Diese Untersuchung wurde an larvalen Buntbarschen in verschiedenen Entwicklungsstadien durchgeführt, da die Otolithen während der Larvalentwicklung durch eine rasche Größenzunahme, sowie dynamische Umgestaltungen gekennzeichnet sind. Zudem wurden weitere mineralisierte Gewebe wie Zähne und Schädelknochen analysiert. Ferner wurden die allgemein am Calciumstoffwechsel beteiligten Organe wie Kiemen, Darm und Niere in den gleichen Entwicklungsprofilen untersucht. Sämtliche untersuchten Epithelien und Gewebe sind durch eine Co-Expression der PMCA-Isoformen 1 bis 4 während der Larvalentwicklung gekennzeichnet. Aufgrund der in dieser Arbeit gewonnenen Daten kann angenommen werden, dass jede der vier PMCA-Isoformen eine spezialisierte Funktion in den untersuchten Epithelien und Geweben erfüllt. So ist PMCA1 in den sensorischen Epithelien des Innenohrs am Transport der Calciumionen in die Endolymphe beteiligt, während die Isoform 2 eher die Funktion eines "housekeeping gene" erfüllt und zur Aufrechterhaltung der basalen Calciumkonzentration wichtig ist. In den Knochen wird die Calciumexportfunktion hauptsächlich von den Isoformen 1 und 4 erfüllt, die basalen Calciumlevel innerhalb der Zelle werden durch Isoform 3 aufrechterhalten. Demnach könnte die Regulation der Calciumionen durch die Plasmamembran-Calcium ATPase ein komplexer und fein regulierter Prozess sein. Die Ergebnisse der Expressionanalyse - eine spezifische Reaktion sowohl mit der Sense-, wie auch mit der Antisense-Sonde - haben zu der Annahme geführt, dass für die vier Plasmamembran-Calcium ATPase Isoformen in Oreochromis mossambicus zusätzlich zur Sense-RNA auch natürlich vorkommende Antisense-RNA transkribiert wird. Diese Hypothese wurde durch die Methode des Northern Blot überprüft, wodurch weitere Hinweise auf die Existenz von natürlicher Antisense-RNA gewonnen werden konnten. Natürlich vorkommende antisense-Transkripte können entweder direkt als Matrize für die Translation verwendet werden oder haben Einfluss auf die Expression der korrespondierenden sense-RNA. Ob dies auch in Oreochromis mossambicus der Fall ist, wurde durch quantitative In-situ Hybridisierung im Kontext des diurnalen Wachstumsrhythmus der Otolithen untersucht. Mit Hilfe dieser Methode konnten sowohl Änderungen der Expressionslevel beider Transkripte, wie auch Veränderungen des Verhältnisses von Sense- zu Antisense-RNA beobachtet werden. Hieraus ließ sich ableiten, dass die Regulation der PMCA in den sensorischen Epithelien des Innenohrs zum einen durch die Transkriptionsrate, wie auch durch die Expression von Antisense-Transkripten erfolgen könnte, wobei hierbei wahrscheinlich das Verhältnis von Sense- zu Antisense-RNA eine Rolle spielt. Welcher Regulationsmechanismus der natürlichen antisense-RNA dabei im Detail wirksam wird bedarf weiterer Untersuchungen.In fish the perception of gravity takes place in the otolithic organs of the inner ear. These structures are filled with endolymph fluid and posses a sensory macula epithelium on which the otolith, the so called inner ear stone, is attached. The otoliths mainly consist of calcium carbonate which is embedded in a protein matrix. The otolith growth is subjected to a diurnal rhythm. Up to now, it is not clear how the calcium ions, which are needed for the otolith minerlisation, are transported through the sensory epithelium into the endolymph. The aim of this study was to analyze the localization and function of the plasmamembrane-calcium ATPase (PMCA) as a candidate for the calcium transporting protein in the inner ear sensory epithelia of Oreochromis mossambicus with regard to the otolith biomineralization. This study was carried out using larval cichlids in different developmental stages, because in the course of the larval development, the otoliths are characterised by a rapid increase in size and dynamic rearrangements. In addition, further mineralised tissues like the teeth and the skull bones have been analysed. Moreover, the organs generally participating in the calcium metabolism like gills, intestine and kidney have been examined in the same developmental profiles. All analysed epithelia and tissues are charaterised by a co-expression of the PMCA-isoforms 1 to 4 throughout the larval development. Based on the results of this study it can be assumed that each of the four PMCA-isoforms fullfills a specialised function in the examined epithelia and tissues. In the inner ear sensory epitehlia PMCA 1 is involved in the transport of calcium ions into the endolymph, whereas isoform 2 rather performs the function of a "housekeeping gene" and is important for the maintenance of the basal calcium concentration. In the bones, the calcium export function is mainly performed by the isoforms 1 and 4, the basal calcium levels are kept stable by isoform 3. Thus the regulation of the calcium ions may be a complex and delicately regulated process. The results of the expression analysis - a specific reaction with the sense-, as well as the antisense-probe - led to the assumption that, in addition to the sense-RNA, also naturally occuring antisense-RNA is transcribed for the four plasmamembrane-calcium ATPase isoforms in Oreochromis mossambicus. These hypothesis was tested with the Northern Blot method, thereby further clues for the existence of natural antisense-RNA have been obtained. Naturally occuring antisense-transcripts can either directly serve as a template for transcription or influence the expression of the corresponding sense-RNA. To check if this is also true for Oreochromis mossambicus quantitative in-situ hybridizations in the context of the diurnal otolith growth rhythm have been performed. By the help of this method it was possible to observe changes in the expression levels of both transcripts, as well as changes in the ratio between sense- and antisense-RNA. Herefrom it was deducible, that the regulation of PMCA in the inner ear sensory epithelia may occur via the transcription rate, as well as by the expression of the antisense-transcripts themselves, in this case probably the ratio between the sense- and antisense-RNA matters. Which of the regulatory mechanisms known for naturally occuring antisense-RNA is acting in detail requires further research

Inner Ear Otolith Asymmetry in Late-Larval Cichlid Fish (Oreochromis mossambicus, Perciformes) Showing Kinetotic Behaviour Under Diminished Gravity

The inner ears of all vertebrates are designed to perceive auditory and vestibular inputs. Although a tremendous diversity in the inner ear can be found even among bony fishes, the morphologies of the utricle and of the semicircular canals are rather conservative among vertebrates. Fish show kinetoses under reduced gravity (spinning movements and looping responses) and are regarded model organisms concerning the performance of the otolithic organs. Otoliths can be analysed easily because they are compact, in contrast to the otoconial masses of other vertebrates. Here, late-larval Oreochromis mossambicus were subjected to 0.0001 × g and 0.04 × g aboard a sounding rocket, their behavior was observed and morphometrical analyses on otoliths were carried out. Fish swimming kinetotically at 0.0001 × g had a higher asymmetry of utricular otoliths (gravity perception) but not of saccular otoliths (hearing process) than specimens behaving normally at this gravity level (p = 0.0055). Also, asymmetries of lapilli in animals swimming normally at 0.0001 × g were lower than asymmetries in specimens swimming normally at 0.04 × g (p = 0.06). This supports the “otolith asymmetry hypothesis”, an explanation for the susceptibility to kinetosis, particularly concerning the utricular otoliths. It would be interesting to identify processes generating asymmetric otoliths, also in regard to human motion sickness