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Searching for the Testicular Clock : Comparing daily patterns of clock gene expression and the duration of the seminiferous epithelium cycle in three hamster species
No full textRhythmic oscillations that repeat every 24 hours can be found in numerous behavioral and physiological functions. Beside the endogenous master clock in the suprachiasmatic nucleus (SCN), peripheral oscillators exist that can disengage from the master clock rhythm by different mechanisms. The fact that core clock genes in peripheral tissues do not always have the same characteristics as in the SCN suggests that their function may vary in different organs. One main function of the mammalian testis is the production of sperm cells. The duration of the cycle of the seminiferous epithelium (DCSE) is species-specific and has a very low inter-individual variation. Various substances and environmental conditions failed to alter this duration which suggests that the exact timing of male germ cell development is mainly determined by the genetic background of the cell itself. The aim of this study was to search for a possible link between the DCSE and daily clock gene expression patterns in the testis.
Therefore, daily expression patterns of the clock genes Bmal1, Period1, Period2, Clock, Cryptochrome1 and Cryptochrome2 were recorded at each of eight time points during a 24 hour period in the testis, kidney, liver, spleen and heart of three hamster species (Phodopus sungorus, Phodopus roborovskii and Cricetulus griseus; family: Cricetidae). Additionally, the DCSE of P. roborovskii and C. griseus was estimated, whereas the DCSE of P. sungorus has already been published.
Clock gene expression was found to be rhythmic in all investigated organs, however with inconsistent results in the testis. Complex cosinor analysis revealed species differences in temporal gene expression patterns regarding their orthophase, number of peaks, and amplitude for all genes and organs with most pronounced differences in the testis. In this organ, all six gene expression patterns were more similar between P. roborovskii and C. griseus than between them and P. sungorus. However, the DCSE of P. roborovskii (9.2 days) was closer to that of P. sungorus (7.9 days, Van Haaster and De Rooij 1993a) than to that of C. griseus (17.1 days).
The main hypothesis of this study could not be confirmed, since there was no hint for a link between clock gene expression patterns in the testis and the DCSE in the investigated species. The results of this study strongly indicate that clock gene expression is species-specific and that their function in peripheral tissues might be at least partly connected to clock-unrelated traits that vary between the investigated species
Diversity and dynamics of bacterial populations in marine bioaerosols
No full textAirborne bacteria are omnipresent in the atmosphere, having a substantial impact on ecological patterns (distribution of organisms), medical concerns (spreading of pathogens) and climate functioning (condensation nuclei). Despite its unquestionable importance for ecosystem functioning, airborne bacteria, and particularly those in marine bioaerosols, are still understudied. The absence of standardised methods further complicates proper comparabilty of the few bioaerosol studies that exist to date.
The current thesis aimed to gather basic knowledge about abundances and composition of bacterial communities in marine bioaerosols and how their spatial and seasonal dynamics may be affected by environmental factors. The spatial dynamics were studied in samples which were taken during a cruise with the research vessel Heincke from the North to Baltic Sea, whereas seasonal dynamics were investigated in a yearlong sampling campaign at the remote island of Helgoland (German Bight, North Sea). Furthermore, a complementing evaluation of quantification methods was performed to identify suitable procedures that could potentially be used for standardised investigations. All analyses were carried out using culture-independent methods (pyrosequencing, ARISA, q-PCR) in order to avoid any possible biases.
All things considered, the current findings elucidated highly diverse bacterial communities in marine bioaerosols which were subject to strong temporal and spatial fluctuations. The observed patterns further supported the idea of an airborne bacterial core cumminty. The evaluation of modern methodologies to assess this diversity clearly underlined the urgent need for further investigations. Therefore, the current findings represent an important step towards a better understanding of patterns and processes within airborne bacterial communities, thereby advancing our knowledge on bioaerosols and their driving factors
Hydrothermal liquefaction of Nannochloropsis salina to biocrudes
No full textAs a consequence of a global appetite for fossil fuels which will continue to rise as the global population rises, innovative, renewable and sustainable solutions will be required to continue to satiate global energy demands of tomorrow. Microalgae display many of the desired attributes for future energy needs. One of the many ways to convert biomass into fuels is through a process known as hydrothermal liquefaction. Despite the possible range of product distributions, hydrothermal liquefaction renders a microorganism into thousands of discrete compounds with a complexity akin to petroleum crude oil. Via ultra high resolutions analysis by atmospheric pressure chemical ionization Fourier transform ion cyclotron resonance mass spectrometry (APCI FT-ICR MS), we analyzed the converted biocrudes of freshwater and saltwater reactions of Nannochloropsis salina and identified significant fractions of hydrocarbons, N1O1 class and O2 class compounds. A smaller number of chlorine, sulfur, and phosphorus containing compounds were also identified and discussed.
Hydrothermal liquefaction of Nannochloropsis salina was shown to be completely converted to a complex biocrude mixture. These biocrudes comprised a large number of classes of compounds well suited as a drop-in replacement for petroleum crude oil in both the fuel and lubricant industries. It was subsequently concluded that further catalytic upgrading would be required
Studies on a Dicer homolog(DrnA) and the Elongator Complex of Dictyostelium discoideum
No full textIn Dictyostelium discoideum several homologs of RNAi proteins have been identified, though their functional similarity is not yet clear. This study was designed to identify the role of Dicer protein(DrnA) in the RNAi mechanism of D. discoideum. The protein was successfully cloned and expressed in Dictyostelium, however, attempts to pulldown protein interaction partners as well as knockout the DrnA protein was not successful.The second part of the study was on the identification of the Elongator complex of Dictyostelium. The primary role of the complex involves tRNA modification as witnessed from yeast. Using sequence homology searches the core complex, involving protein Elp1,2 & 3 were identified. Further, the presence of a protein complex involving the above mentioned proteins were identified by mass spectrometry and their functional role in tRNA modification in Dictyostelium was shown for the first time
The Location of Coenzyme Q10 in Phospholipid Membranes Made of POPE
No full textCoenzyme Q10 is an ingredient of cosmetic products and pharmaceutical drugs due to its antioxidant effect. In fact, it is an essential component of eukaryotic cells, where it participates in the mitochondrial respiratory chain. It transports electrons and protons between the respiratory complexes I and III and between II and III Inside the inner mitochondrial membrane. Finding the precise location of Q10 inside the membrane is a topic of research, which aims at a deeper understanding of the mitochondrial respiratory chain.
This thesis deals with an investigation of the interaction of Q10 and model membranes made of 1-palmitoyl-2-oleoyl-phosphoethanolamine (POPE) by means of small-angle synchrotron X-ray diffraction, infrared spectroscopy and differential scanning calorimetry. Q10, which stands for ubiquinone-10 (UQ) or ubihydroquinone-10 (UH), did not influence the main phase transition temperature, but significantly decreased the lamellar-inverse hexagonal phase transition temperature (Th). The effect of UH on Th was stronger than the effect of UQ and the effect of liquid Q10 on Th was stronger than the effect of crystalline Q10. In presence of Q10, the lattice parameters of the lamellar phases remained unaffected, whereas the HII lattice parameter clearly changed. While UQ had an increasing effect, UH had a decreasing effect. Furthermore, Q10 prevented the formation of cubic phases.
The results of this thesis on the location of Q10 in lamellar and in the inverse hexagonal phases made of POPE were used to draw conclusions on the location inside the inner mitochondrial membrane. They suggest that the headgroup of Q10 penetrates into the lower chain region of the membrane away from its center, which could be required for the antioxidant effect of Q10. In addition, there is evidence, that Q10 possesses a conformational flexibility inside the membrane, which might be relevant for a conversion at the binding sites of the respiratory complexes. The side chain of Q10 appears to remain close to the center, such that it forms a dense barrier against proton leakage
Multinuclear Metal-Oxo Clusters Stabilized by Polyoxometalates: Synthesis, Structure, Magnetism, Electrochemistry, and Catalysis
No full textPolyoxometalates (POM) are a well-established class of discrete metal-oxides, with a large number of structures and compositions, and an unmatched combination of physicochemical properties. This work is focused on the deliberate synthesis of multinuclear metal-oxo clusters (e.g. Mn, Fe, Co) stabilized by POM fragments. Such compounds possess unique electronic, magnetic, optical, electrochemical, and catalytic properties. In the course of the synthetic work the influence of multiple parameters such as pH, ionic strength, temperature, counter cations, capping groups (e.g. phosphate, diphosphate), transition metal ions in different oxidation states, effect of halide ions, and POM precursors as different salts have been investigated systematically. Several multi-transition metal-containing heteropolytungstates comprising tetrameric, trimeric, and dimeric assemblies have been synthesized and structurally characterized by a multitude of analytical techniques in the solid state and in solution.
This thesis is subdivided into six chapters. Chapter 1 is a general introduction to the research area, presenting the historical background, structural aspects, properties, and applications of polyoxometalates (POMs). Chapter 2 describes the background of transition metal-containing heteropolytungstates and the motivation to perform this work. Chapter 3 is an experimental section and describes the synthetic procedures for the POM precursors and the analytical techniques used to characterize the products. Chapter 4 is devoted to tetrameric compounds, and nine polyanions are presented belonging to three different structure types. Polyanions 1 – 6 are tetrameric assemblies of the {M16(XW9)4} (M = Co2+, Mn2+/3+, Fe3+) structure type, comprising a central M4O4 cubane unit, surrounded by four {M3XW9} Keggin units, ande this assembly is capped by four phosphate groups. Polyanion 7 is alsoa tetrameric assembly comprising four {Co2GeW10} units connected by two pyrophosphate, two tungstate, and two {Ge2O7} groups. Polyanions 8 and 9 comprise a 15-copper(II)-oxo cluster surrounded by four {SiW9} units and a halide ion (Cl- (8), Br- (9)) in the center.
Chapter 5 presents the trimeric polyanion 10 comprising the assembly {Co9(GeW9)3} with two capping phosphate groups.
Finally, Chapter 6 describes three dimeric polyanions comprising four Co2+ (11), Ni2+ (12), and Zn2+ (13) ions where the {M4(OH)2(H2O)2} core is sandwiched by two {SiW10} units
Phytochemical Characterization and Antimicrobial Activity of Sudanese Medicinal Plants
No full textIn Sudan, a tropical country rich in biodiversity and biological resources, medicinal plants have been used for the treatment of several diseases and microbial infections in traditional medicine. However, the actual compounds responsible for the biological effects are still poorly characterized. In this project, extracts prepared from traditional medicinal plants native to Sudan and Europe were investigated for their phytoconstituents and biological effects. 457 phenolic compounds were unambiguously assigned to their regioisomeric level using LC–MSn. 332 of them were extracted for the first time from their sources, and 46 of them were not reported previously in nature. Chlorogenic acids, chlorogenic acid glycosides, phenolic acids, hydroxycinnamates, proanthocyanidins, flavonoid glycosides, flavonoid aglycones and derivatives thereof were identified as major phytoconstituents. Next, using preparative HPLC, 18 bioactive compounds including chlorogenic acids, flavonoid glycosides, coumarins and derivatives were isolated and identified in the plant extracts. Concerning the biological activities, various extracts showed antibacterial, antiparasitic and antioxidant activities. For example Acacia nilotica, Ocimum basilicam, Ziziphus spina-christi, Balanites aegyptiaca, Sonchus oleraceus, Punica granatum, Mimosa pigra and Ixora coccinea were the most interesting ones with antioxidative, antiplasmodial, antitrypanosomal and antibacterial activities. Moreover, the antibacterial activities of some naturally occurring phenolic compounds were investigated. Among the tested individual phytochemicals, phloretin, resveratrol, luteolin 7-O-glucoside and epigallocatechin gallate showed the highest antimicrobial activities. Most importantly, we investigated the influenza virus neuraminidase (NA) inhibitory activities of naturally occurring chlorogenic acids and synthesized derivatives against several viral NAs. The enzyme inhibition results indicated that chlorogenic acids and caffeic acid derivatives exhibited high antiviral effects.
This study provides a detailed molecular level understanding of the phytoconstituents in a wide selection of Sudanese medicinal plants. Consequently, the phytochemical and pharmacological knowledge is better understood in support of the use of such plants in traditional medicine.
As a highlight, the project presents a comprehensive LC-MS analysis for model mono and oligosaccharides based on their binding behavior to the sodium ion.
This contribution shows that the modern MS methods such as UPLC-ESI-Q-TOF-MS/MS and HPLC-ESI-MSn can be used as unambiguously assignment of regioisomers of flavonoids glycosides and phenolic natural products. They can also be applied as predictive reliable techniques in the assignment of mono and oligosaccharide relative stereochemistry
Unipolar and Ambipolar Thin-Film Transistors and Digital Circuits
No full textThin-film transistors (TFTs) are key building blocks for flat panel displays with active-matrix addressing. TFTs based on different material systems, ranging from inorganic to organic semiconductors, have been extensively researched for electronic applications requiring flexibility, low cost, large area and transparency. In the following thesis, different limiting aspects of the thin-film technology have been addressed and discussed.
The ability of some materials to accumulate both, electrons and holes, demonstrating an ambipolar behavior, has enabled realization of ambipolar transistors and digital circuits. An analytical model was developed describing their electrical behavior. A comparison between unipolar and ambipolar devices is presented with good experimental agreement. The results showed that the operation of ambipolar circuitry is limited by their low static noise margin and increased power consumption.
Increasing the device’s frequency range operation is usually achieved by scaling. A model describing the static and dynamic behavior was developed for CMOS inverters. The influence of device scaling on the performance was studied with good agreement to experiments. Scaling the lateral dimensions of the transistors down to few µm limits the circuit performance due to contact effects.
Reducing the contact resistance (RC) has been proven to be an effective way for achieving faster circuit operation. A method of using self-assembled monolayers treatment for RC reduction is discussed and a model describing its effect on the RC was developed. The results revealed that the RC is mainly determined by the molecular ordering, rather than the tuning of the work function.
The stability of TFTs is an important aspect for reliable circuit operation and high yield. A density-of-states model was used to study the environmental effects on the current/voltage characteristics of organic transistors. The results showed that the threshold voltage shift observed while biasing the devices in oxygen/moisture is caused by formation of acceptor- and/or donor-like states
Drifting Ethologists. Nikolaas Tinbergen and Gustav Kramer. Two Intellectual Life-Histories in an Incipient Darwinian Epistemic Community (1930-1983).
No full textThe present dissertation thesis understands itself as epistemological case study for the principles of scientific change. It presumes that the modern sciences established distinguishable subsystems of human culture yet, in principle, are still sharing culture’s inner reproductive dynamics. To evince this dynamic indirectly, this study asks for the formative impulse cyclic cultural wave movements may have entailed in the life-histories of two behavioural biologists, N. Tinbergen (1907-1988) and G. Kramer (1910-1959), during the formative period of their epistemic community in the middle of the 20th century (1930-1975).
Focusing on “behaviour”, both as a phenomenon and a multidimensional scientific concept, thereby appears to be particularly promising: Behaviour scientists not only made behaviour a subject of their research (scientization of behaviour) – Kramer’s and Tinbergen’s publications include an additional communicative function inasmuch as particularly the various performative forms of knowledge organization indicate a movement “to” and “away from” the Extended Synthesis consisting of the Modern Evolutionary Synthesis, on the one hand, and the “Ethological Synthesis”, on the other, whereby both syntheses are supposed to have originated both simultaneously and complementarily.
With help of the pheno-epistemological approach outlined in the introductory section of the presented thesis, it shall be demonstrated that Tinbergen’s and Kramer’s trajectories, though complementary in their arrangement, went through several analogous epistemic transitions. Both their linear order and their specific kind, which can be precisely determined on basis of methodological tools such as the concept of “scientific orientation” and the notion of “frame”, seem to reveal that epistemological appearances correlate with forms socio-biological transformation such as the repeal of ambivalent academic socialization, the diversification of an epistemic community, the development of receptive “hypes”, or the phenomenon of reverse socialization as a consequence of increased generation conflicts due to the shortening of cultural cycles. On basis of these correlations future transdisciplinary studies must clarify the psycho-physical origins of these phenomena.Die vorliegende Dissertation versteht sich selbst als epistemologische Fallstudie über die Prinzipien des wissenschaftlichen Wandels. Sie nimmt an, dass die modernen Wissenschaften unterscheidbare Teilsysteme innerhalb der menschlichen Kultur etabliert haben, aber im Prinzip dennoch die der Kultur innewohnende reproduktive Transformationsdynamik teilen. Um diese Dynamik indirekt nachzuweisen, fragt diese Studie nach dem formativen Impuls, der von periodischen kulturellen Wellenbewegungen ausgehend auf die Lebenszyklen zweier Verhaltensbiologen, nämlich N. Tinbergen (1907-1988) und G. Kramer (1910-1959), während der Entstehungsphase ihrer Wissenschaftsgemeinschaft in der Mitte des 20. Jahrhunderts eingewirkt hat (1930-1975).
Methodisch vielversprechend ist dabei der Fokus auf das Phänomen und den mehrdimensionalen Begriff des „Verhaltens“: Verhaltenswissenschaftler haben „Verhalten“ nicht nur zum Objekt ihrer Wissenschaft gemacht (Verwissenschaftlichung des Verhaltens) – die Publikationen G. Kramers und N. Tinbergens enthalten eine zusätzliche kommunikative Funktion insofern als besonders die verschiedenen Formen performativer Wissensorganisation eine Bewegung „hin zu“ und „weg von“ der Erweiterten Synthese nahelegen, welche als Verbindung bestehend aus der Synthetischen Evolutionstheorie, einerseits, und einer zeitgleich und komplementär entstandenen Ethologischen Synthese, andererseits, aufgefasst werden kann.
Mit Hilfe des in der Einleitung entwickelten phäno-epistemologischen Ansatzes soll gezeigt werden, dass Tinbergens und Kramers Lebenspfade, trotz ihrer Komplementarität, in analoger Weise mehrere epistemologische Umbrüche durchliefen. Deren Verlauf als auch ihre spezifische Natur zeigen, dass epistemologische Erscheinungen mit Formen soziologisch-biologischer Transformation korreliert sind, wie z.B. die Aufhebung einer Sozialisationsklemme, die Aufspaltung einer Wissenschaftsgemeinschaft, die Entwicklung kultureller „Hypes“, oder das Phänomen umgekehrter Sozialisation, wobei Letzteres als indirekte Folge verkürzter kultureller Zyklen und der daraus resultierenden erhöhten Wahrscheinlichkeit von Generationskonflikten erklärt werden kann. Die psycho-physische Grundlage dieser Korrelationen bleibt noch zu klären
Identification and Characterization of Vibrio species
No full textPotentially pathogenic Vibrio spp. in the marine environment are regarded to as emerging health risk in Europe, particularly infections caused by V. parahaemolyticus, V. vulnificus and non-O1/non-O139 V. cholerae strains. Thus, the inclusion of Vibrio spp. in surveillance programs and studies about the distribution of Vibrio spp. are urgently needed. This thesis contributes both: the evaluation of Matrix-assisted laser / desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) as tool for species identification in environmental samples and the analysis of spatial patterns of Vibrio spp. populations in the North and Baltic Seas.
Regarding MALDI-TOF MS, the specific reference database VibrioBase was developed. VibrioBase reveals Vibrio spp. identification agreements of 96.9% compared to the approved rpoB-sequence-based identification method as well as higher identifications scores and a better discrimination for closely related Vibrio spp. compared to the general BiotyperTM database of the manufacturer. Thus, the cost-effective and rapid MALDI-TOF MS method achieves accurate Vibrio spp. identification when used in combination with VibrioBase. In addition, single mass peaks were used to allow species identifications based on sensitive peaks (SIBOPS). The SIBOPS approach achieves 98% identification agreements with the conventional MALDI-TOF MS / VibrioBase system and is independend of the respective mass spectrometric eqipment and software tools. Furthermore, mass spectrometric biomarkers were found, that might be used for the direct identification of Vibrio spp. in environmental samples. Using ERIC-PCR genotyping, general patterns were not observed for the distribution of V. cholerae, V. parahaemolyticus and V. vulnificus in the North and Baltic Seas. Particularly the latter two species were separated into distinct regions, which are however not linked to geographical aspects and, to a minor extent, are asscociated with environmental parameters such as salinity.
In consequence, MALDI-TOF MS was confirmed as a promising tool for species identifications from environmental samples. VibrioBase and SIBOPS are important steps towards the implementation of Vibrio spp. in surveillance programs executed by health authorities. Future reseach has to be done to acquire knowledge about ecological aspects of Vibrio spp. in temperate waters, in particular the linkage to plankton species in the North and Baltic Sea and the influence of bacteriophages for shaping Vibrio spp. populations