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Developmental and structural analysis of similarities among calcified and keratinized tooth structures in mouth of vertebrates
Karpecká, Zuzana ; Černý, Robert (advisor) ; Hovořáková, Mária (referee)
Calcified teeth comprise the hardest vertebrate tissues (enamel and dentine) and they undoubtedly represent a key evolutionary advantage for their users. Nevertheless, teeth have been lost many times and they were often replaced by keratinised structures, such as rhamphoteca of birds or of turtle beaks, or labial tooth structures and scratching laminae of many aquatic vertebrates. This thesis is intended to analyse levels of similarities among keratinised teeth and structures of three phylogenetically distinct lineages of amniotes and to compare them to morphogenesis of true teeth. Detailed developmental and structural characteristics of oral apparatus possessing keratinous teeth of lampreys, Loricarid cathfishes and frog tadpoles were identified and distinguished. Keratinous structures of cathfishes include only horny projections from single cell surface (unculi), whereas in frog tadpoles both horny jaw sheet and unicellular labial teeth composed by cell columns were found; the lamprey oral apparatus consists of multicellular teeth and laminae instead. Disparate phenotypes of these keratinous structures can, however, developmentally derive from a general process of keratinization: morphological disparities arise by distinct gradual accretion of keratinous layers and collumns during development. My...
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Dental stem cells during development of vertebrate dentitions
Pešanová, Věra ; Soukup, Vladimír (advisor) ; Hovořáková, Mária (referee)
Vertebrate dentition is a dynamic structure, which continuously renews its elements, the teeth. Continuous tooth renewal is enabled thanks to the presence of epithelial and mesenchymal dental stem cells. Epithelial stem cells are located in the dental lamina, which, together with the adjacent mesenchyme, takes part in regulation of the stem cells through a complicated signalling network. This network is responsible for the positioning, correct amount, inactivity, proliferation and differention of the stem cells. Vertebrate dentitions are morphologically diverse. However, their development is, to a certain extent, controlled by shared evolutionarily conserved mollecular mechanisms. For example, epithelial stem cells of all vertebrate groups examined so far express the transcription factor Sox2 and are shown to be regulated by signalling pathways, such as Wnt/β-catenin, Shh, Fgf and Bmp. Due to the rich diversity in dental lamina morphologies, the locations of presumptive stem cells correspondingly differ among vertebrates. This thesis summarizes current knowledge on dental stem cells in each lineage to identify shared and derived aspects of vertebrate dentitions.
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Developmental and structural analysis of similarities among calcified and keratinized tooth structures in mouth of vertebrates
Karpecká, Zuzana ; Černý, Robert (advisor) ; Hovořáková, Mária (referee)
Calcified teeth comprise the hardest vertebrate tissues (enamel and dentine) and they undoubtedly represent a key evolutionary advantage for their users. Nevertheless, teeth have been lost many times and they were often replaced by keratinised structures, such as rhamphoteca of birds or of turtle beaks, or labial tooth structures and scratching laminae of many aquatic vertebrates. This thesis is intended to analyse levels of similarities among keratinised teeth and structures of three phylogenetically distinct lineages of amniotes and to compare them to morphogenesis of true teeth. Detailed developmental and structural characteristics of oral apparatus possessing keratinous teeth of lampreys, Loricarid cathfishes and frog tadpoles were identified and distinguished. Keratinous structures of cathfishes include only horny projections from single cell surface (unculi), whereas in frog tadpoles both horny jaw sheet and unicellular labial teeth composed by cell columns were found; the lamprey oral apparatus consists of multicellular teeth and laminae instead. Disparate phenotypes of these keratinous structures can, however, developmentally derive from a general process of keratinization: morphological disparities arise by distinct gradual accretion of keratinous layers and collumns during development. My...
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