The object of diploma thesis is a loading determination for strength calculation of HPH 2 Twin Shark glider matching the requirements of Certification Specification for Sailplanes (CS-22). Loading of the wing, tail section, fuselage and undercarriage is determined in this work.

We consider tail empirical processes for long memory stochastic volatility models with heavy tails and leverage. We show a dichotomous behaviour for the tail empirical process with fixed levels, according to the interplay between the long memory parameter and the tail index; leverage does not play a role. On the other hand, the tail empirical process with random levels is not affected by either long memory or leverage. The tail empirical process with random levels is used to construct a family of estimators of the tail index, including the famous Hill estimator and harmonic moment estimators. The limiting behaviour of these estimators is not affected by either long memory or leverage. Furthermore, we consider estimators of risk measures such as Value-at-Risk and Expected Shortfall. In these cases, the limiting behaviour is affected by long memory, but it is not affected by leverage. The theoretical results are illustrated by simulation studies.

We model Normal Inverse Gaussian distributed log-returns with the assumption of stochastic volatility. We consider different methods of parametrization of returns and following the paper of Lindberg, [21] we assume that the volatility is a linear function of the number of trades. In addition to the Lindberg’s paper, we suggest daily stock volumes and amounts as alternative measures of the volatility. As an application of the models, we perform Value-at-Risk and Expected Tail Loss predictions by the Lindberg’s volatility model and by our own suggested model. These applications are new and not described in the literature. For better understanding of our caluclations, programmes and simulations, basic informations and properties about the Normal Inverse Gaussian and Inverse Gaussian distributions are provided. Practical applications of the models are implemented on the Nasdaq-OMX, where we have calculated Value-at-Risk and Expected Tail Loss for the Ericsson B stock data during the period 1999 to 2004.

Sexual selection is one of main selective pressure affecting body size, and subsequently leads to the evolution of sexual size dimorphism (SSD). The eyelid geckoes, family Eublepharidae, are a monophyletic group with considerable variability in SSD, including both male-larger and female-larger species. In general, it was supposed that eyelid geckos are highly variable in presence of male combats and in complexity of male pre-copulatory behaviour, and that this variability in this conspicuous male behaviour may lead to differences in SSD. The aim of this study was to reveal relationships between the direction of SSD and presence/absence of tail vibration during precopulatory phase and male combat behaviour. Using behavioural testing, it was revealed that male combats are present in all tested species, even in species, where the absence of such behaviour was supposed so far. In several species, the strong effect of seasonality to male aggression was observed, which may play a role in the evolution of SSD. The evolutionary changes in the presence/absence of tail vibration during precopulatory phase were independent on changes in the direction of SSD, the presence of tail vibration seems to be ancestral state for these lizards. During the evolution of this group, the tail vibrations disappeared four...

The tail in mammals is an important organ, which in contrast to most vertebrae, doesn't add to the motor function of their bodies. The use of the mamals' tail is much more varied and it can fulfill many different functions. This work includes a survey of these functions and analyzes collected data concerning 553 spieces of mammals across all families. The data includes information about the length of tail, the length of body, body mass, living environment and outer signs on the anal pole of these species. The resulting analysis concludes that the tail length is dependent both on the length of the mammal's body and its living environment. Outward signs of the tail depend on its length as well as the length of the body and the living environment. Distinctive tail ending and tail base probably fulfill a communicative function. The tail is more likely to have communication than cryptic significance.

In this thesis, fast Viterbi Decoder algorithms for a multi-core system are studied. New parallel Viterbi algorithms for decoding convolutional codes are proposed based on tail biting trellises. The performances of the new algorithms are first evaluated by MATLAB and then Eagle (E-UTRA algorithms for LTE) link level simulations where the optimal parameter settings are obtained based on various simulations. One of the algorithms is proposed for implementation in the product due to its good BLER performance and low implementation complexity. The new parallel algorithm is then implemented on target DSPs for Ericsson internal multi-core system to decode the PUSCH (Physical Uplink Shared Channel) CQI (Channel Quality Indicator) in LTE (Long Term Evolution). And the performance of the new algorithm in the real multi-core system is compared against the current implementation regarding both cycle and memory consumption. As a fast decoder, the proposed parallel Viterbi decoder is computationally efficient which reduces significantly the decoding latency and solves memory limitation problems on DSP.

It has been noticed that one of the main challenges for e-commerce sites is providing the users with an efficient search function. It has also been noticed that the search function is one of the things the user is valuing the most when evaluating an e-commerce. The information technology enables the possibility to consume almost anything one could wish for. The challenge is in how to find this specific item. It is hence of interest to examine how to improve the search tool and what effect the updated search tool results in. The objective of this research is twofold. The objective motivated by economic factors is to examine how a user’s ability to find relevant items is affected by being able to refine a search result by selecting relevant attribute values. The other objective has a more technical character and is to examine how the rule based method performs in terms of extracting attribute values for enable the creation of the filtering function. The examinations for this research is conducted at a Swedish online auction company that due to the structure of its e-catalogue provides a suitable setup for the examinations. Because of the examinations being conducted in the environment of the auction company’s system this limits the result to only being representative for data with the same characteristics as the auction company’s. For answering the questions stated in the objective two methods are applied. One for examining the economic part and one for examining the technical part. The economic question is answered after analysing the result of an A/B-test conducted at the auction company. For answering the technical examination an information extraction technique is evaluated. The result of the economical examination is that a significant increase in conversion rate can be concluded for the system version with filtering enabled. The result of the technical examination shows that the rule based method can be used for information extraction in some cases. However, the obtained accuracy will be affected by the characteristics of the data the information extraction is performed on.

Masters of Commerce / If share price fluctuations follow a simple random walk then it implies that forecasting models based on historical growth rates have little ability to forecast acceptable share price movements over a certain period. The simple random walk description of share price dynamics is obtained when a large number of investors have equal probability to buy or sell based on their own opinion. This simple random walk description of the stock market is in essence the Efficient Market Hypothesis, EMT. EMT is the central concept around which financial modelling is based which includes the Black-Scholes model and other important theoretical underpinnings of capital market theory like mean-variance portfolio selection, arbitrage pricing theory (APT), security market line and capital asset pricing model (CAPM). These theories, which postulates that risk can be reduced to zero sets the foundation for option pricing and is a key component in financial software packages used for pricing and forecasting in the financial industry. The model used by Black and Scholes and other models mentioned above are Gaussian, i.e. they exhibit a random nature. This Gaussian property and the existence of expected returns and continuous time paths (also Gaussian properties) allow the use of stochastic calculus to solve complex Black- Scholes models. However, if the markets are not Gaussian then the idea that risk can be. (educed to zero can lead to a misleading and potentially disastrous sense of security on the financial markets. This study project test the null hypothesis - share prices on the JSE follow a random walk - by means of graphical techniques such as symmetry plots and Quantile-Quantile plots to analyse the test distributions. In both graphical techniques evidence for the rejection of normality was found. Evidenceleading to the rejection of the hypothesis was also found through nonparametric or distribution free methods at a 1% level of significance for Anderson-Darling and Runs test.

The cytoskeletal protein vinculin plays a key role in the control of cell-cell or cell-matrix adhesions. It is involved in the assembly and disassembly of focal adhesions and affects their mechanical stability. While many facts highlight the importance and significance of vinculin for vital processes, its precise role in the regulation of cell adhesions is still only partially understood. Various EPR methods are used in this work in order to study the vinculin tail (Vt) domain in an aqueous buffer solution and its structural changes induced by F-actin and acidic phospholipids. EPR results in combination with a rotamer library approach (RLA), MD simulation and other computational methods allowed the construction of molecular models of Vt and dimeric Vt in the presence and absence of its binding partners. Furthermore, X-band orientation selective DEER measurements were applied on a Vt double mutant. It could be shown that the determination of the mutual orientation of protein bound spin labels is possible at X-band frequencies, if the orientation correlation of the spin label pair is strong. The method established here can be used to determine valuable information about proteins and nucleic acids, expanding the virtue of DEER spectroscopy as a tool for structure determination.

The vertebrate tail is unique for each species and fulfils a broad spectrum of functions. In the axolotl (Ambystoma mexicanum), a tailed amphibian, the tail constitutes one-third of the full body length and is necessary for swimming. Despite its size, most of the tail's tissues are derived from the posterior neural plate of the neurula. Although giving rise to neuronal structures of the central nervous system along most of its length, the most posterior part of the neural plate develops preponderantly into presomitic mesoderm (PSM) which forms muscle, bone and cartilage of the tail and posterior trunk. During development, the posterior neural plate reverses its orientation during an anterior turn movement (Taniguchi et al., 2017). Cells of the most posterior plate region become now localised in an anterior position while previously more anterior neural plate cells land at a more posterior site. Simultaneously, the axial neural tube and notochord extend themselves posteriorly. The PSM, developing bilaterally to the central axis, is integrated into posterior tail expansion while forming new somites at its anterior end. It is still elusive which morphological changes the PSM undergoes to facilitate tail formation and posterior elongation of the embryo. Furthermore, it remains enigmatic in what way PSM cells change their shape, orientation, migration behaviour and distribution to meet the requirements needed for adjusting PSM and somite morphology. With homotopic tissue transplantations of posterior neural plate cells from a gfp-expressing donor to a white (d/d) recipient, enabled specific labelling of all mesodermal cells of the tail. Otherwise, mesodermal cells of the trunk and tail can not be distinguished, neither genetically nor morphologically. With this cell labelling approach, the entire tail mesoderm could be imaged in toto. Thus, measurements of the morphological changes of the PSM and cell tracking in 3D was possible during development. With this technique, posterior neural plate cells could be shown to form parts of the posterior neural tube, the entire posterior PSM and the somites of the tail. During this course of development, the PSM becomes longer but does not increase its volume. Only when forming the somites, an increase in volume could be measured in the mesoderm. Single-cell labelling showed an anterior shift of cell movement led by medial PSM cells and followed by more laterally located cells. The anterior displacement happens simultaneously to the posterior elongation of the embryo. A hypothetical push by newly generated cells at the tail tip could be ruled out. Mitotic cells were evenly distributed in all tissues of the tail with a low proliferation rate. The morphological changes and anterior relocations of the tail mesoderm could, therefore, mainly be explained by cell migration. Therefore, further analyses focussed on cell migration, particularly on cellular characteristics displayed during migration such as shape, orientation, volume, distribution and filopodia organisation to obtain more profound information about how PSM cells migrate and contribute to somite formation. The net movement of tail elongation is directed posteriorly regardless of anteriorly relocating PSM cells. That is only feasible if a lateral expansion of the PSM by laterally migrating PSM cells is counteracted. There have been no studies on the lateral boundary so far. In the axolotl, the PSM is covered laterally by a two-layered epidermis and a fibronectin-rich extracellular matrix. After removing the tail epidermis, operated embryos showed missing or malformed tails, especially with lateral and dorsal curvatures and shortenings. Tail mesoderm examined in these cases showed an increased PSM volume and a lateral expansion of the tissue. A nearly normal tail developed when, after removing the epidermis, the embryos developed in 1% agarose supplemented with fibronectin. In contrast, a simple covering of the PSM with a nitrocellulose membrane, incubation in the softer methylcellulose or in agarose without fibronectin did not rescue tail formation. The lateral pressure on the PSM and a fibronectin-rich extracellular matrix seem necessary to preserve the tissue architecture of the PSM during tail formation. This study unravels the behaviour of individual PSM cells during their morphogenesis from single cells in the posterior plate of the neurula until somite formation in the tail bud. Overall, with specific labelling of tail mesodermal cells, their contribution to PSM morphology could be elucidated, and a more detailed model of tail elongation could be proposed: The posterior expansion of the neural tube and notochord pushes the posterior neural plate tissue posteriorly and squeezes the cells into an elongated mediolaterally oriented form. Labelling experiments of small individual cell groups showed that the ventral posteriormost cells are the first to escape this pressure by relocating anteriorly. Then, more anteriorly located cells follow, as well as dorsally located cells. These movements explain the anterior turn. Thereby, mesodermal cells start to migrate randomly, become elongated and change their orientation from mediolateral to anterior-posterior. Random cell migration leads to homogeneous cell mixing, which results in an aligned uniform tissue of trunk and tail PSM. The lateral constriction by the epidermis channels the undirected migration movements in an anterior direction. In this way, cells are directed towards the site of somite formation, the PSM narrows, and the embryo elongates posteriorly. This extension model includes the individual cell behaviour, which on the whole shapes PSM morphology. The analysed dynamic morphological changes of the PSM can be linked to the developmental processes of the tail and the posterior elongation of the axis.:1 Introduction 1.1 Embryonic tail formation . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1.1.1 Mechanism of tail formation . . . . . . . . . . . . . . . . . . . . . 1 1.1.2 Molecular determination of cell populations in the tail bud . . . . . 5 1.2 Axial elongation of the vertebrate body plan . . . . . . . . . . . . . . . . . 8 1.2.1 Anterior body elongation (elongation of the trunk) . . . . . . . . . 8 1.2.2 Posterior body elongation (tail elongation) . . . . . . . . . . . . . . 9 1.3 Studying tissue morphology during development . . . . . . . . . . . . 11 1.4 Aim of the project . . . . . . . . . . . . . . . . . . . . . . .. . . . . . 12 2 Materials 2.1 Chemicals and solutions . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 2.2 Antibodies and dyes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 2.3 Techniqual equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 2.4 Software . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 3 Methods 3.1 Animals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 3.1.1 Breeding of axolotls and embryo collection . . . . . . . . . . . . 19 3.1.2 Injections with the vital dye DiI . . . . . . . . . . . . . . . . . . . 19 3.1.3 Tissue transplantation techniques . . . . . . . . . . . . . . . . . . . 19 3.2 Immunohistochemical staining . . . . . . . . . . . . . . . . . . . . . . . . 20 3.2.1 Vibratome sections . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 3.2.2 Whole-mount staining . . . . . . . . . . . . . . . . . . . . . . . . . 21 3.3 Optical tissue clearing protocols . . . . . . . . . . . . . . . . . . 21 3.3.1 Ethyl cinnamate based optical tissue clearing protocol . . . . . . . 21 3.3.2 SeeDB optical clearing protocol . . . . . . . . . . . . . . . . . . . . 22 3.4 Image analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 3.4.1 3D image generation and processing . . . . . . . . . . .. . . . . . 22 3.4.2 Length measurements . . . . . . . . . . . . . . . . . . . . . . . . . . 22 3.4.3 Manual segmentation . . . . . . . . . . . . . . . . . . . . . . . . . 24 3.4.4 Automatic segmentation . . . . . . . . . . . . . . . . . . . . . . . . 25 3.5 Determination of cellular parameters . . . . . . . . . . . . . . .. . . . . 25 3.5.1 Cell shape . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 3.5.2 Cell and tissue volume . . . . . . . . . . . . . . . . . . . . . . . . . 25 3.5.3 Cellular distribution . . . . . . . . . . . . . . . . . . . . . . . . . . 25 3.5.4 Closest neighbour analysis . . . . . . . . . . . . . . . . . . . . . . . 26 3.5.5 Cell orientation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 3.5.6 Length and orientation of filopodia . . . . . . . . . . . . . . . . . . 31 3.5.7 Distance of cells to a plane . . . . . . . . . . . . . . . . . . . . . . . 31 3.5.8 Mitotic rate and spindle orientation . . . . . . . . . . . . . . . . . 32 4 Results 4.1 The presomitic mesoderm is associated with axial elongation. . . . . . 33 4.1.1 Elongation of the body axis . . . . . . . . . . . . . . . . . . . . . . 33 4.1.2 Contribution of different tissues . . . . . . . . . . . . . . . . . . . . 34 4.1.3 Differential contribution of mesoderm and epidermis . . . . . . . . . 40 4.1.4 Dual potential of mesodermal progenitors . . . . . . . . . . . . . . . 42 4.1.5 Mesodermal tissue expansion . . . . . . . . . . . . . . . . . . . . . 46 4.2 Cellular behaviour influences mesodermal morphology . . . . . . . . . 50 4.2.1 Cell division . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 4.2.2 Positional changes . . . . . . . . . . . . . . . . . . . . . . . . . . . 53 4.2.3 Cellular characteristics . . . . . . . . . . . . . . . . . . . . . . . . . 59 Cell shape changes . . . . . . . . . . . . . . . . . . . . . . . . . . . 59 Change of cell orientation . . . . . . . . . . . . . . . . . . . . . . . 61 Orientation of filopodia . . . . . . . . . . . . . . . . . . . . . . . . . 63 Cell distribution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66 4.3 The epidermis fascilitates mesodermal tissue integrity . . . . . . .. . . . 67 4.3.1 Mesodermal tissue integrity . . . . . . . . . . . . . . . . . . . . . . 68 4.3.2 Malformed tails after epidermis removal . . . . . . . . . . . . . . . 70 4.3.3 Alteration in mesodermal tissue dimensions . . . . . . . . . . . . . 73 4.3.4 Alteration of cell density after epidermis removal . . . . . . . . . . 77 4.3.5 Rescue of tail formation . . . . . . . . . . . . . . . . . . . . . . . . 80 5 Discussion 5.1 Cell migration of the presomitic mesodermal cells . . . . . . . . .. . . . 85 5.1.1 Continuity of gastrulation movements . . . . . . . . . . . . . . . . . 85 5.1.2 Directed migration . . . . . . . . . . . . . . . . . . . . . . . . . . . 86 5.1.3 Random cell migration . . . . . . . . . . . . . . . . . . . . . . . . . 88 5.1.4 Lateral mechanical constriction . . . . . . . . . . . . . . . . . . . . 90 5.2 Non-volumetric growth of the presomitic mesoderm . . . . . . . . . . . . . 91 5.3 Models of tail presomitic mesoderm formation . . . . . . . . . . . . . . . . 93 / Der Schwanz der Wirbeltiere ist bei jeder Art einzigartig und erfüllt ein breites Spektrum an Funktionen. Beim Salamander Axolotl (Ambystoma mexicanum), macht der Schwanz ein Drittel der gesamten Körperlänge aus und ist zum Schwimmen notwendig. Trotz seiner Größe stammen die meisten Gewebe des Schwanzes von der posterioren Neuralplatte der Neurula ab. Obwohl der größte Teil der Neuralplatte neuronale Strukturen des Zentralnervensystems hervorbringt, entwickelt sich der posteriore Teil der Neuralplatte überwiegend zu präsomitischem Mesoderm (PSM), das Muskeln, Knochen und Knorpel des Schwanzes und des hinteren Rumpfes bildet. Während der Entwicklung kehrt die posteriore Neuralplatte ihre Orientierung in einer anterioren Drehbewegung um (Taniguchi et al., 2017). Zellen der hintersten Plattenregion werden in eine anteriore Position verschoben, während zuvor anteriorere Neuralplattenzellen an einer posterioren Stelle landen. Gleichzeitig verlängert sich das axiale Neuralrohr und das Notochord nach posterior. Das PSM, das sich bilateral zur Zentralachse entwickelt, ist im Prozess der Schwanzverlängerung involviert, während es gleichzeitig an seinem vorderen Ende neue Somiten bildet. Es ist immer noch unklar, welche morphologischen Veränderungen das PSM durchläuft, um die Schwanzbildung und die posteriore Ausdehnung des Embryos zu ermöglichen. Darüber hinaus ist unbekannt, auf welche Weise PSM-Zellen ihre Form, Orientierung, ihr Migrationsverhalten und ihre Verteilung ändern, die für eine Veränderung der PSM- und Somitenmorphologie erforderlich sind. Mit homotopen Gewebetransplantationen von posterioren Neuralplattenzellen von einem gfp-exprimierenden Spender auf einen weißen (d/d) Empfänger, konnte eine spezifische Markierung aller mesodermalen Zellen des Schwanzes erreicht werden. Andernfalls können mesodermale Zellen des Rumpfes und des Schwanzes weder genetisch noch morphologisch unterschieden werden. Mit diesem Zellmarkierungsansatz konnte das gesamte Schwanzmesoderm in toto abgebildet werden. So waren Messungen der morphologischen Veränderungen des PSM und Zellverfolgung in 3D während der Entwicklung möglich. Mit dieser Technik konnte gezeigt werden, dass die Zellen der posterioren Neuralplatte Teile des posterioren Neuralrohrs, das gesamte posteriore PSM und die Somiten des Schwanzes bilden. Dabei wird das PSM länger, ohne sein Volumen zu vergrößern. Erst während der Bildung von Somiten wurde eine Volumenzunahme gemessen Einzelzellmarkierungen zeigten eine anteriore Verschiebung der Zellen, angeführt von medialen PSM-Zellen und gefolgt von lateral gelegenen Zellen. Diese anteriore Verschiebung geschieht gleichzeitig mit der posterioren Streckung des Embryos. Ein hypothetischer Schub durch neugebildete Zellen an der Schwanzspitze konnte ausgeschlossen werden. Mitotischen Zellen waren gleichmäßig in allen Geweben des Schwanzes verteilt und wiesen eine geringe Proliferationsrate auf. Die morphologischen Veränderungen und anterioren Verlagerungen des Schwanzmesoderms können daher hauptsächlich durch Zellmigration erklärt werden. Die Analysen konzentrierten sich daher auf die Zellmigration, insbesondere auf die zellulären Charakteristika, die sich während der Migration zeigen, wie z.B. Form, Orientierung, Volumen, Verteilung und Filopodienorganisation. So konnten neue Informationen darüber gewonnen werden, wie PSM-Zellen wandern und zur Somitenbildung beitragen. Die Nettobewegung der Schwanzverlängerung ist, unabhängig von nach anterior wandernden PSM-Zellen, nach posterior gerichtet. Das ist nur möglich, wenn einer lateralen Ausdehnung des PSM durch ungerichtet migrierenden Zellen entgegengewirkt wird. Über die Rolle einer laterale Begrenzung bei diesem Prozess gibt es bisher keine Untersuchungen. Beim Axolotl ist das PSM seitlich von einer zweischichtigen Epidermis und einer Fibronektin-reichen extrazellulären Matrix bedeckt. Nach Entfernung der Schwanzepidermis zeigten operierte Embryonen fehlende oder missgebildete Schwänze, insbesondere mit einer lateralen und dorsalen Krümmung und einer Verkürzung. Untersuchungen des Schwanzmesoderms zeigten ein erhöhtes PSM-Volumen und eine laterale Ausdehnung des Gewebes. Ein nahezu normaler Schwanz entwickelte sich, wenn die Embryonen nach Entfernung der Epidermis mit 1% Agarose, ergänzt mit Fibronektin, bedeckt wurden. Im Gegensatz dazu konnte eine einfache Abdeckung des PSM mit einer Nitrozellulosemembran, die Inkubation in der weicheren Methylzellulose oder in Agarose ohne Fibronektin die Schwanzbildung nicht normalisieren. Der seitliche Druck auf das PSM und eine Fibronektin-reiche extrazelluläre Matrix scheinen notwendig zu sein, um die Gewebearchitektur des PSM während der Schwanzbildung zu erhalten. Diese Studie zeigt das Verhalten einzelner PSM-Zellen während der Morphogenese der hinteren Neuralplatte bis zur Somitenbildung. Insgesamt konnte durch die spezifische Markierung von mesodermalen Zellen des Schwanzes deren Beitrag zur PSM-Morphologie aufgeklärt und ein detaillierteres Modell der Schwanzverlängerung vorgeschlagen werden: Die posteriore Ausdehnung des Neuralrohrs und des Notochords schiebt das posteriore Neuralplattengewebe nach hinten und quetscht die Zellen in eine verlängerte, mediolateral orientierte Form. Markierungsexperimente einzelner Zellgruppen zeigten, dass die ventralen, posterior gelegenen Zellen diesem Druck als erste entkommen, indem sie sich nach anterior verschieben. Ihnen folgen weiter anterior gelegene Zellen sowie dorsal gelegene Zellen. Diese Bewegungen erklären die anteriore Drehung. Dabei beginnen mesodermale Zellen ungerichtet zu wandern, verlängern sich und ändern ihre Orientierung von mediolateral nach anterior-posterior. Die ungerichtete Zellwanderung führt zu einer homogenen Zelldurchmischung, so dass zusammen mit dem PSM des Rumpfes ein einheitliches Gewebe gebildet wird. Die laterale Begrenzung durch die Epidermis kanalisiert die ungerichteten Migrationsbewegungen in anteriore Richtung. Auf diese Weise werden die Zellen in Richtung der Somitenbildungsstelle gelenkt, das PSM verengt sich, und der Embryo streckt sich nach hinten. Dieses Ausdehnungsmodell beinhaltet das individuelle Zellverhalten, das insgesamt die Morphologie des PSM prägt. Die analysierten dynamischen morphologischen Veränderungen des PSM können mit Schwanzentwicklungsprozessen und der posterioren Elongation der Achse in Verbindung gebracht werden.:1 Introduction 1.1 Embryonic tail formation . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1.1.1 Mechanism of tail formation . . . . . . . . . . . . . . . . . . . . . 1 1.1.2 Molecular determination of cell populations in the tail bud . . . . . 5 1.2 Axial elongation of the vertebrate body plan . . . . . . . . . . . . . . . . . 8 1.2.1 Anterior body elongation (elongation of the trunk) . . . . . . . . . 8 1.2.2 Posterior body elongation (tail elongation) . . . . . . . . . . . . . . 9 1.3 Studying tissue morphology during development . . . . . . . . . . . . 11 1.4 Aim of the project . . . . . . . . . . . . . . . . . . . . . . .. . . . . . 12 2 Materials 2.1 Chemicals and solutions . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 2.2 Antibodies and dyes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 2.3 Techniqual equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 2.4 Software . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 3 Methods 3.1 Animals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 3.1.1 Breeding of axolotls and embryo collection . . . . . . . . . . . . 19 3.1.2 Injections with the vital dye DiI . . . . . . . . . . . . . . . . . . . 19 3.1.3 Tissue transplantation techniques . . . . . . . . . . . . . . . . . . . 19 3.2 Immunohistochemical staining . . . . . . . . . . . . . . . . . . . . . . . . 20 3.2.1 Vibratome sections . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 3.2.2 Whole-mount staining . . . . . . . . . . . . . . . . . . . . . . . . . 21 3.3 Optical tissue clearing protocols . . . . . . . . . . . . . . . . . . 21 3.3.1 Ethyl cinnamate based optical tissue clearing protocol . . . . . . . 21 3.3.2 SeeDB optical clearing protocol . . . . . . . . . . . . . . . . . . . . 22 3.4 Image analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 3.4.1 3D image generation and processing . . . . . . . . . . .. . . . . . 22 3.4.2 Length measurements . . . . . . . . . . . . . . . . . . . . . . . . . . 22 3.4.3 Manual segmentation . . . . . . . . . . . . . . . . . . . . . . . . . 24 3.4.4 Automatic segmentation . . . . . . . . . . . . . . . . . . . . . . . . 25 3.5 Determination of cellular parameters . . . . . . . . . . . . . . .. . . . . 25 3.5.1 Cell shape . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 3.5.2 Cell and tissue volume . . . . . . . . . . . . . . . . . . . . . . . . . 25 3.5.3 Cellular distribution . . . . . . . . . . . . . . . . . . . . . . . . . . 25 3.5.4 Closest neighbour analysis . . . . . . . . . . . . . . . . . . . . . . . 26 3.5.5 Cell orientation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 3.5.6 Length and orientation of filopodia . . . . . . . . . . . . . . . . . . 31 3.5.7 Distance of cells to a plane . . . . . . . . . . . . . . . . . . . . . . . 31 3.5.8 Mitotic rate and spindle orientation . . . . . . . . . . . . . . . . . 32 4 Results 4.1 The presomitic mesoderm is associated with axial elongation. . . . . . 33 4.1.1 Elongation of the body axis . . . . . . . . . . . . . . . . . . . . . . 33 4.1.2 Contribution of different tissues . . . . . . . . . . . . . . . . . . . . 34 4.1.3 Differential contribution of mesoderm and epidermis . . . . . . . . . 40 4.1.4 Dual potential of mesodermal progenitors . . . . . . . . . . . . . . . 42 4.1.5 Mesodermal tissue expansion . . . . . . . . . . . . . . . . . . . . . 46 4.2 Cellular behaviour influences mesodermal morphology . . . . . . . . . 50 4.2.1 Cell division . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 4.2.2 Positional changes . . . . . . . . . . . . . . . . . . . . . . . . . . . 53 4.2.3 Cellular characteristics . . . . . . . . . . . . . . . . . . . . . . . . . 59 Cell shape changes . . . . . . . . . . . . . . . . . . . . . . . . . . . 59 Change of cell orientation . . . . . . . . . . . . . . . . . . . . . . . 61 Orientation of filopodia . . . . . . . . . . . . . . . . . . . . . . . . . 63 Cell distribution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66 4.3 The epidermis fascilitates mesodermal tissue integrity . . . . . . .. . . . 67 4.3.1 Mesodermal tissue integrity . . . . . . . . . . . . . . . . . . . . . . 68 4.3.2 Malformed tails after epidermis removal . . . . . . . . . . . . . . . 70 4.3.3 Alteration in mesodermal tissue dimensions . . . . . . . . . . . . . 73 4.3.4 Alteration of cell density after epidermis removal . . . . . . . . . . 77 4.3.5 Rescue of tail formation . . . . . . . . . . . . . . . . . . . . . . . . 80 5 Discussion 5.1 Cell migration of the presomitic mesodermal cells . . . . . . . . .. . . . 85 5.1.1 Continuity of gastrulation movements . . . . . . . . . . . . . . . . . 85 5.1.2 Directed migration . . . . . . . . . . . . . . . . . . . . . . . . . . . 86 5.1.3 Random cell migration . . . . . . . . . . . . . . . . . . . . . . . . . 88 5.1.4 Lateral mechanical constriction . . . . . . . . . . . . . . . . . . . . 90 5.2 Non-volumetric growth of the presomitic mesoderm . . . . . . . . . . . . . 91 5.3 Models of tail presomitic mesoderm formation . . . . . . . . . . . . . . . . 93