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Palaeoecological aspects and evolution of the Late Cretaceous oyster assemblages
Rantuch, Jakub ; Košťák, Martin (advisor) ; Mergl, Michal (referee) ; Reháková, Daniela (referee)
The presented thesis explores the palaeoecological aspects of the evolution of the well-known fossil oyster genus Rhynchostreon Bayle, 1874, a significant representative of Cretaceous fauna. The study integrates sedimentological (quartz grain size), geochemical (concentration of major oxides) and palaeobiological (taphonomy) proxies to categorise five oyster-bearing localities in the Bohemian Massif and the Pieniny Klippen Belt (Western Carpathians) into three environments with differing substrate characteristics, environmental energy levels and salinity regimes. Subsequently, the five specific palaeopopulations of Rhynchostreon suborbiculatum (Lamarck, 1801), occupying these habitats (including the dynamic Cenomanian nearshore, the quiet environment of the Turonian hemipelagic sea and the Cenomanian-Turonian marginal marine system influenced by variable fluvial activity), underwent a series of morphological and population studies. These studies involved the analyses of size-frequency distributions, morphotype structure, and shell thickness. Results from this multidisciplinary approach suggest that the salinity tolerance of R. suborbiculatum may be higher than commonly assumed, and its ecological response to climatic changes (i.e. the fluctuation of salinity, level of eutrophism, etc.) aligns with...
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Genome stability of human induced pluripotent stem cells
ŘEHÁKOVÁ, Daniela
Human induced pluripotent stem cells (hiPSCs) play roles in both disease modeling and regenerative medicine. It is critical that the genomic integrity of the cells remains intact and that the DNA repair systems are fully functional. I focused on the detection of DNA double-strand breaks (DSBs) by phosphorylated histone H2AX (known as H2AX) and p53-binding protein 1 (53BP1) in multiple lines of hiPSCs, their source cells, human embryonic stem cells (hESCs) and cells differentiated from hiPSCs. I measured spontaneously occurring DSBs throughout the process of reprogramming and during long-term in vitro culture and differentiation process. To assess the variations in the functionality of the DNA repair system among the samples, the number of DSBs induced by gamma irradiation and the decrease over time was analyzed. The foci number was detected by fluorescence microscopy separately for the G1 and S/G2 cell cycle phases. Source cells contained a low number of non-replication-related foci, while this number increased after reprogramming into hiPSCs and then decreased again after long-term in vitro passaging or differentiation. The artificial induction of DSBs revealed that the repair mechanisms function well in the source cells and hiPSCs at low passages but fail to recognize a substantial proportion of DSBs at high passages. Observations suggest that cellular reprogramming increases the DSB number but that the repair mechanism functions well. However, with long-term hipSCs culture reparation capacity decreases.
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