acase@tulane.edu

acase@tulane.edu

acase@tulane.edu

acase@tulane.edu

acase@tulane.edu

This thesis deals with the distribution and potential roles of 5-methylcytosine (m('5)C) in the DNA of vertebrates. First, the levels of m('5)C in several tissues from different vertebrates were investigated by high performance liquid chromatography (HPLC) of enzymatic digests of DNA. Using samples derived from humans, 4 types of monkeys, rats, mice, a rat snake and a frog, we showed unequivocally the existence of tissue-specific differences in the levels of 5-methylcytosine in the DNA. The tissue-specific differences in overall DNA methylation did not correlate with what is known about cell turnover rates nor with the percent of the genome that is transcribed. In all the organisms studied, the nervous and lymphoid tissues showed the highest levels of genomic m('5)C among the tissues studied. In humans and mice, the tissue-specific differences in DNA methylation previously found in whole cellular DNA were also present in the different fractions of genomic DNA fractionated by reassociation kinetics. The highly repetitive sequences were enriched in m('5)C compared to the middle repetitive and unique sequences DNA methylation in the human placental mitochondria DNA was probed with HpaII and MspI and by HPLC. No m('5)C was detected at the sequence C-C-G-G. However, low levels of m('5)C were detected by HPLC By HPLC the m('5)C content in the DNA from 103 human tumors including benign, primary malignant, and secondary tumors were analyzed. Most of the malignant tumors had a lower m('5)C content in their genome compared to those of benign tumors or normal organs from which the neoplasias were derived Lastly, by Southern blot analysis of human placental and brain DNA samples digested with several restriction endonucleases, the methylation and organization of a human glycine (CCG) tRNA gene and homologous sequences was investigated. No methylation was found within the major repeat of this tRNA gene at HpaII and ThaI sites / acase@tulane.edu

This research includes four parts: (1) synthesis of tetrahydropyran derivatives, (2) novel alkyne-aldehyde coupling reaction and a novel alkyne-alcohol cyclization reaction, (3) synthesis of polysubstituted naphthalene derivatives and (4) synthetic studies directed toward Epicalyxin F Part one. Synthesis of tetrahydropyran derivatives. Various Lewis acids mediate the cyclization between homoallylic alcohols and aldehydes to generate 4-chlorotetrahydropyans and 4-hydroxytetrahydropyrans Part two. Novel alkyne-aldehyde coupling reaction and a novel alkyne-alcohol cyclization reaction. Gallium trichloride catalyzed cyclization between alkynes and aldehydes to generate unsaturated ketones and five membered indenes. Also, gallium trichloride catalyzed a novel, unusual cyclization between alkynes and allyl alcohols to generate a very interesting 5 membered ring system Part three. Synthesis of polysubstituted naphthalene derivatives . Polysubstituted naphthalene derivatives were conveniently synthesized via a gallium trichloride catalyzed cyclization between aromatic alkynes and phenyl aldehydes and ketones Part four. Synthetic studies of Epicalyxin F. Studies are currently underway to synthesize Epicalyxin F, a natural product based on the various Lewis acid promoted couplings and cyclization reactions discovered in our laboratory / acase@tulane.edu

acase@tulane.edu

Zero polymer concentration diffusion coefficients, D$\sb{\rm o}$, of heparin and chondroitin-6-sulfate were independent of ionic strength Cs. Since static dimensions of such linear polyelectrolytes are sensitive functions of Cs, the constant D$\sb{\rm o}$ may represent a partial draining effect. Similar measurements were made for polystyrene sulfonate fractions. For high weights RMS radii of gyration $\langle$S$\sp2\rangle\sp{1/2}$ vs. Cs were determined. 1/D$\sb{\rm o}$ followed $\langle$S$\sp2\rangle\sp{1/2}$ at high Cs ($>$100mM), climbed less steeply at intermediate Cs, and reached a plateau below 30mM. Although tempting to interpret these regimes as non-draining, partial draining, and free-draining, respectively, 1/D$\sb{\rm o}$ $\alpha$ M$\sp{0.5}$ for all Cs. Thus, although some type of draining condition seems implicated, a simplistic free-draining condition in the plateau region is inconsistent with the mass scaling. The data show that dynamic light scattering may not be an appropriate particle sizing technique for many linear polyelectrolytes. The 'extraordinary' diffusional phase, present in some samples, could always be permanently removed by proper filtration. Using polyethylene glycol and dextran as osmotic stressing agents, the concentrations of hyaluronate and heparin were measured as a function of osmotic pressures $\Pi$ over the range of 0.03 to nearly 50 atmospheres. The experimental results were analyzed in terms of the Donnan osmotic pressure, the virial expansion, and Flory's first neighbour interaction parameter. In addition, $\Pi$ was looked at as a function of the reciprocal cube root of the concentration, which represents an average intermonomer spacing at high concentrations. The decay lengths in the so-called hydration region were found to be around 2.6A, and in the electrostatically dominated region the decay lengths were found to be dependent on the ionic strength, but not simply so. The osmotic compressibilities were also calculated and compared to compressibility data of corneal stroma and articular cartilage. These latter compressibilities were close to those for the pure hyaluronate and heparin, strengthening the evidence that glycosaminoglycans (GAGs) are largely responsible for connective tissue compressibility. Higher compressibilities for previously reported GAG data is thought to be related to the protein content of those samples / acase@tulane.edu

Diderot's portrayal of the complex and enigmatic figure of the mid-eighteenth century, Le Neveu de Rameau, continues to generate interest in his profoundly original text. The abundant critical interpretations of this and other works by the philosophe are evidence of the multilayered complexities of his thought. His experimentation with forms and themes, especially in Le Neveu de Rameau, coincides with that of many of his contemporaries including one whom he portrayed, Jean-Francois Rameau, as well as to modern ones The intricate composite of elements Diderot used in his depiction of the nephew often parallels contemporary portraits of the younger Rameau, especially in Cazotte's text, La Nouvelle Rameide, where many of the same motifs and themes characterize the nephew's parasitic nature and its correlative role, that of the fool. Jean-Francois Rameau whose self-portrait, La Rameide, can be seen as a demonstration of his parasitism, possessed a personality that his contemporaries, Diderot especially, drew on in order to use him as a reference point to criticize the society that he both represents and stands out from Other writers have drawn inspiration from Diderot's portrayal of the nephew and incorporated their own modes of interpreting his unique character. These varied attempts to portray, or reinterpret, the character in Diderot's dialogue reveal an interest in the stylistic and esthetic modernity in Diderot whose approach to every subject was always challenging to his reader and to his critic. A comparison with other writers' texts dealing with the nephew demonstrates Diderot's artistic genius and offers interesting insights into the creative abilities of other artists / acase@tulane.edu