No description available.

The master‘s thesis is aimed on numerical simulation of autofrettage of high pressure fuel vessel – rail in Common Rail system. First there is described Chaboche model, which is later used for simulation of autofrettage. There are described different approaches which can be used to obtain sufficient material model. Then there is observed influence of these different approaches on stress state of rail within the process of autofrettage. Suitability of Chaboche model for autofrettage and re-autofrettage simulations is assessed by comparing with more complex Jiang model. In the end there is a study of influence of autofrettage pressure on different properties, especially on residual stresses.

<p>Zebrafish regenerate amputated caudal fins, restoring the size and shape of the original appendage. Regeneration requires generation of diverse cell types comprising the adult fin tissue. Knowledge of the cellular source of new cells and the molecules involved is fundamental to our understanding of regenerative responses. In this dissertation, the contribution made by the bone cells towards fin regeneration is investigated. Fate mapping of osteoblasts revealed that spared osteoblasts contribute only to regenerating osteoblasts and not to other cell types, thereby suggesting lineage restriction during fin regeneration. The functional significance of osteoblast contribution to fin regeneration is tested by developing an osteoblast ablation tool capable of drug induced loss of bone cells. Normal fin regeneration in the absence of resident osteoblast population suggests that the osteoblast contribution is dispensable and provides evidence for cellular plasticity during fin regeneration. To uncover the genes involved in proliferation of osteoblasts within the fin regenerate, a candidate in-situ screen was carried out and revealed bone specific expression of fgfr4 and twist3. Transgenic tools for visualization of gene expression confirmed the screen results. Knockdown of twist3 by morpholino antisense technology impedes fin regeneration. Mutant heterozygotes for twist3 were generated using genome editing reagents, which will enable loss-of-function study in future.</p> / Dissertation

Chronic hypersensitive pain states can become established following sustained, repeated or earlier noxious stimuli and are notably difficult to treat, especially in cases where nerve injury contributes to the trauma. A key underlying reason is that a variety of plastic changes occur in the central nervous system (CNS) at spinal and potentially also supraspinal levels to upregulate functional activity in pain processing pathways. A major component of these changes is the enhanced function of excitatory amino acid receptors and related signalling pathways. Here we utilised rodent models of neuropathic and inflammatory pain to investigate whether evidence could be found for lasting hypersensitivity following neonatal (or adult) noxious stimuli, in terms of programming hyper-responsiveness to subsequent noxious stimuli, and whether we could identify underlying biochemical mechanisms. We found that neonatal (postnatal day 8, P8) nerve injury induced either long lasting mechanical allodynia or shorter lasting allodynia that nonetheless was associated with hyper-responsiveness to a subsequent noxious formalin stimulus at P42 despite recovery of normal mechanical thresholds. By developing a new micro-scale method for preparation of postsynaptic densities (PSD) from appropriate spinal cord quadrants we were able to show increased formalin-induced trafficking of GluA1- containing AMPA receptors into the PSD of animals that had received (and apparently recovered from) nerve injury at P8. This was associated with increased activation of ERK MAP kinase (a known mediator of GluA1 translocation) and increased expression of the ERK pathway regulator, Sos-1. Synaptic insertion of GluA1, as well as its interaction with a key partner protein 4.1N, was also seen in adults during a nerve injury-induced hypersensitive pain state. Further experiments were carried out to develop and optimise a new technological platform enabling fluorometric assessment of Ca2+ and membrane potential responses of acutely isolated CNS tissue; 30-100 μm tissue segments, synaptoneurosomes (synaptic entities comprising sealed and apposed pre- and postsynaptic elements) and 150 × 150 μm microslices. After extensive trials, specialised conditions were found that produced viable preparations, which could consistently deliver dynamic functional responses. Responsiveness of these new preparations to metabotropic and ionotropic receptor stimuli as well as nociceptive afferent stimulant agents was characterised in frontal cortex and spinal cord. These studies have provided new opportunities for assessment of plasticity in pain processing (and other) pathways in the CNS at the interface of in vivo and in vitro techniques. They allow for the first time, valuable approaches such as microscale measurement of synaptic insertion of GluA1 AMPA receptor subunits and ex vivo assessment of dynamic receptor-mediated Ca2+ and membrane potential responses.

Virtually all multicellular organisms are capable of developing differently in response to environmental variation. At the molecular level, such developmental plasticity requires interpretation and perpetuation of environmental signals without changing the underlying genotype. Such non-genetic, heritable information is known as epigenetic information. This dissertation examines epigenetic information among social insects, and how differences in such information relate to phenotypic caste differences. The studies included herein primarily focus on one form of epigenetic information: DNA methylation. In particular, these studies explore DNA methylation as it relates to and impacts (i) alternative phenotype and particular gene expression differences in two social insect species, (ii) histone modifications, another important form of epigenetic information, in insect genomes, and (iii) molecular evolutionary rate of underlying actively transcribed gene sequences. We find that DNA methylation exhibits marked epigenetic and evolutionary associations, and is associated with alternative phenotype in multiple insect species. Thus, DNA methylation is emerging as one important epigenetic mediator of phenotypic plasticity in social insects.

No description available.

No description available.

No description available.

No description available.

Forensic entomology is a well-established science linking arthropod biology and ecology to legal investigations. Specifically, immature development on a decomposing corpse may give insight into the minimum time elapsed since death. Until recently, biological variation within a single species has been overlooked when estimating colonization events. Variation in the form of phenotypic plasticity, or the ability of a single genotype to produce multiple phenotypes under alternative stresses, has been documented in genetic and ecological literature and spans across all phyla. Taking this into account, different subpopulations of forensically pertinent insect species should also possess the ability to adapt to changing environments as geographic distribution increases. Thus, plastic responses of a species to alternative stresses may be measured in biological parameters, such as development time. In this research, three geographically distinct strains of the blow fly Cochliomyia macellaria Fabricius (Diptera Calliphoridae) were reared in two distinct environments in order to measure development time, as well as pupal and adult masses. Strains exhibited genetic variance when compared to each other, and each strain exhibited variable responses across environments (phenotypic plasticity). Plasticity in the form of genotype by environment (GxE) interactions was also exhibited by C. macellaria, although consistent adherence to any single rule explaining ontogenetic trends was not apparent. This research supports the existence of intraspecific variation in a common blow fly of forensic importance. Results of this study will impact the forensic entomology community by encouraging the generation of either strain;specific developmental datasets or statistical models to minimize variation caused by genetic, environment, or GxE effects in order to compare developmental data across strains.