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Thesis (Ph. D.)--Florida State University, 2006. / Advisor: Henry W. Bass, Florida State University, College of Arts and Sciences, Dept. of Biological Science. Title and description from dissertation home page (viewed June 15, 2006). Document formatted into pages; contains x, 83 pages. Includes bibliographical references.

Thèse (M.Sc.) -- Université Laval, 1997. / Bibliogr.: f. 98-115. Publié aussi en version électronique.

Mitochondria from Xenopus laevis and Ambystoma mexica- num embryos between fertilization and the beginning of feeding were studied: the former with respect to metabolic behaviour, enzyme pattern and carrier activity, and the latter with respect to morphological parameters. The metabolic behaviour of mitochondria was studied by assessing the rates of oxygen uptake in presence of various substrates. The rates of oxidation of most substrates change during development. The only substrate to be readily metabolized is glutamate (in presence of malate), whose rate of oxidation presents a peak during gastrulation and declines during larval development. The high rate of oxidation of glutamate and a high aspartate aminotransferase activity indicate that the glutamate- aspartate cycle may be predominant in early embryonic mitochondria. The activity of enzymes from the matrix, the inner membrane and the outer membrane were studied. During early development activities of enzymes in the various compartments change independently of each other. Furthermore, enzymes within one compartment may vary independently. Measurements of carrier activity reveal that the carrier for dicarboxylic acids displays a high activity before gastrulation and decreases thereafter, while the tricarboxylic acid, pyruvate and glutamate/OH carriers show the opposite pattern of change, their activities being low or undetectable during early development. This implies that a mitochondrial differentiation takes place ' during development, beginning at gastrulation when the first differentiated cells appear. In order to correlate mitochondrial and cellular differentiation, morphological parameters of mitochondria from undifferentiated and differentiated cells - Ruffini cells and epidermal cells - were analyzed. Mitochondria from the differentiated cells are significantly different from those in undifferentiated cells. Thus the processes of cell differentiation are accompanied by morphological and biochemical differentiation of the mitochondria. / <p>Diss. (sammanfattning) Umeå : Umeå universitet, 1981, härtill 5 uppsatser</p> / digitalisering@umu

A robotic microscope was designed using a microcontroller to take time-lapse digital photographs of developing salamander embryos. The microcontroller operated three stepper motors to control three-axis movement accurately, and two six mega-pixel digital cameras to capture through-focus time-lapse digital pictures of six views of Ambystoma mexicanum embryos (axolotl, a salamander). The device is designed to take images every five minutes for 80 hours of early development, from fertilization to stage 20, when the neural tube closes to form the brain and spinal column. Techniques to enhance the embryo images were investigated including image fusion to get in-focus views from a stack of images. In the early embryo surface epithelial cells differentiate to form neural tissue and external skin tissue. Observing the whole embryo surface at cellular level will give a better idea of the stress and strain each cell undergoes and what physical forces are involved in cell differentiation. / May 2007

A robotic microscope was designed using a microcontroller to take time-lapse digital photographs of developing salamander embryos. The microcontroller operated three stepper motors to control three-axis movement accurately, and two six mega-pixel digital cameras to capture through-focus time-lapse digital pictures of six views of Ambystoma mexicanum embryos (axolotl, a salamander). The device is designed to take images every five minutes for 80 hours of early development, from fertilization to stage 20, when the neural tube closes to form the brain and spinal column. Techniques to enhance the embryo images were investigated including image fusion to get in-focus views from a stack of images. In the early embryo surface epithelial cells differentiate to form neural tissue and external skin tissue. Observing the whole embryo surface at cellular level will give a better idea of the stress and strain each cell undergoes and what physical forces are involved in cell differentiation.

A robotic microscope was designed using a microcontroller to take time-lapse digital photographs of developing salamander embryos. The microcontroller operated three stepper motors to control three-axis movement accurately, and two six mega-pixel digital cameras to capture through-focus time-lapse digital pictures of six views of Ambystoma mexicanum embryos (axolotl, a salamander). The device is designed to take images every five minutes for 80 hours of early development, from fertilization to stage 20, when the neural tube closes to form the brain and spinal column. Techniques to enhance the embryo images were investigated including image fusion to get in-focus views from a stack of images. In the early embryo surface epithelial cells differentiate to form neural tissue and external skin tissue. Observing the whole embryo surface at cellular level will give a better idea of the stress and strain each cell undergoes and what physical forces are involved in cell differentiation.

Changes in the structure, content and morphology of chromosomes accumulate over evolutionary time and contribute to cell, developmental and organismal biology. The axolotl (Ambystoma mexicanum) is an important model for studying these changes because: 1) it provides important phylogenetic perspective for reconstructing the evolution of vertebrate genomes and amphibian karyotypes, 2) its genome has evolved to a large size (~10X larger than human) but has maintained gene orders, and 3) it possesses potentially young sex chromosomes that have not undergone extensive differentiation in the structure that is typical of many other vertebrate sex chromosomes (e.g. mammalian XY chromosomes and avian ZW chromosomes). Early chromosomal studies were performed through cytogenetics, but more recent methods involving next generation sequencing and comparative genomics can reveal new information. Due to the large size and inherent complexity of the axolotl genome, multiple approaches are needed to cultivate the genomic and molecular resources essential for expanding its utility in modern scientific inquiries. This dissertation describes our efforts to improve the genomic and molecular resources for the axolotl and other salamanders, with the aim of better understanding the events that have driven the evolution of vertebrate (and amphibian) chromosomes. First, I review our current state of knowledge with respect to genome and karyotype evolution in the amphibians, present a case for studying sex chromosome evolution in the axolotl, and discuss solutions for performing analyses of large vertebrate genomes. In the second chapter, I present a study that resulted in the optimization of methods for the capture and sequencing of individual chromosomes and demonstrate the utility of the approach in improving the existing Ambystoma linkage map and generating targeted assemblies of individual chromosomes. In the third chapter, I present a published work that focuses on using this approach to characterize the two smallest chromosomes and provides an initial characterization of the huge axolotl genome. In the fourth chapter, I present another study that details the development of a dense linkage map for a newt, Notophthalmus viridescens, and its use in comparative analyses, including the discovery of a specific chromosomal fusion event in Ambystoma at the site of a major effect quantitative trait locus for metamorphic timing. I then describe the characterization of the relatively undifferentiated axolotl sex chromosomes, identification of a tiny sex-specific (W-linked) region, and a strong candidate for the axolotl sex-determining gene. Finally, I provide a brief discussion that recapitulates the main findings of each study, their utility in current studies, and future research directions. The research in this dissertation has enriched this important model with genomic and molecular resources that enhance its use in modern scientific research. The information provided from evolutionary studies in axolotl chromosomes shed critical light on vertebrate genome and chromosome evolution, specifically among amphibians, an underrepresented vertebrate clade in genomics, and in homomorphic sex chromosomes, which have been largely unstudied in amphibians.