La GlcNAcylation est une modification post-traductionnelle dynamique des protéines cytosoliques et nucléaires qui peut entrer en compétition avec la phosphorylation pour le même résidu de Ser/Thr. Des modifications des taux de GlcNAcylation sont rapportées dans différentes pathologies et dans les cas de cancer du sein, une relation étroite entre GlcNAcylation et tumorigénèse pourrait exister. La delta-lactoferrine est un suppresseur de tumeur potentiel puisqu’elle est sous-exprimée dans le cancer du sein et que son expression conduit à l’arrêt du cycle cellulaire. Nous avons démontré que la delta-lactoferrine est un facteur de transcription régulant l’expression de différents gènes impliqués dans la régulation des acteurs moléculaires du cycle cellulaire (Skp1), dans le déclenchement de l’apoptose (Bax) ou dans la dégradation des ARNm (DcpS). La delta-lactoferrine doit être hautement régulée et nous avons montré que la GlcNAcylation inhibe son activité transcriptionnelle alors que la phosphorylation a l’effet inverse. La mutation des quatre sites de GlcNAcylation conduit à une isoforme de la delta-lactoferrine constitutivement activée possédant une activité pro-apoptotique accrue comparée à l’isoforme sauvage. L’utilisation de mutants de glycosylation, pour lesquels un site unique est préservé, nous a permis de démontrer que la GlcNAcylation du site Ser 10 est cruciale dans la régulation de l’activité de la delta-lactoferrine. Nous avons également localisé une séquence PEST fonctionnelle ainsi que les résidus de lysine cible de l’ubiquitinylation et démontré que la GlcNAcylation de la Ser10 inhibe la polyubiquitinylation et augmente la demi-vie de la protéine. De plus, nous montrons que le complexe transcriptionnel de la delta-lactoferrine interagit avec le ΔLfRE sous une forme phosphorylée et ubiquitinylée suggérant que l’activité transcriptionnelle de la delta-lactoferrine et sa dégradation sont concomitantes / The GlcNAcylation is a dynamic posttranslational modification of cytoplasmic and nuclear proteins which can compete directly with phosphorylation for the same or nearby Ser/Thr residues. Alterations of the GlcNAcylation profile are observed in different pathologies and in case of breast cancer a close relationship between GlcNAcylation and tumorigenesis may exist. Down-regulated in breast cancer, delta-lactoferrin is a potential tumor suppressor the expression of which leads to cell cycle arrest. We demonstrated that delta-lactoferrin is a transcription factor which controls the expression of different proteins involved in the regulation of cell cycle actors (Skp1), apoptosis induction (Bax) or mRNA turnover (DcpS). Therefore, delta-lactoferrin should be highly regulated and our investigations have shown that GlcNAcylation inhibits its transcriptional activity while phosphorylation activates it. The directed mutagenesis of the four GlcNAcylation sites leads to a constitutively active delta-lactoferrin isoform with increased pro-apoptotic effects compared to wild type. Using a series of different mutants in which only one glycosylation site is preserved, we showed that Ser 10 is crucial and regulates delta-lactoferrin activity. We also mapped a functional PEST sequence and the lysine residues which are the ubiquitin ligase targets and we demonstrated that GlcNAcylation of Ser 10 inhibits polyubiquitination of delta-lactoferrin and increases its half-live. Moreover, we showed that delta-lactoferrin transcriptional complex binds to ΔLfRE as a phosphorylated and ubiquinated isoform suggesting that delta-lactoferrin transcriptional activity and degradation are concomitant events.

The Niger Delta clastic wedge formed along the West Africa passive margin. This wedge has been divided into three formations that reflect long-term progradation: 1) pro-delta shales of the Akata Formation (Paleocene to Recent), 2) deltaic and paralic facies of the Agbada Formation (Eocene to Recent) and 3) fluviatile facies of the Benin Formation (Oligocene-Recent). This study combines a three-dimensional seismic image with well log data from Delta field to describe lithic variations of the Agbada Formation and develop a sequence stratigraphic framework. The 5000-feet thick Agbada Formation in Delta field is divided by five major sequence boundaries, each observed in seismic cross sections to significantly truncate underlying strata. Sequence boundaries developed as mass flows eroded slopes steepened by the structural collapse of the Niger Delta clastic wedge. Basal deposits directly overlying areas of deepest incision along sequence boundaries formed by the migration of large, sinuous turbidite channels. Upward-coarsening sets of inclined beds, hundreds of feet thick, record progradation of deltas into turbidite-carved canyons and onto down faulted blocks. Thinner, more continuous seismic reflections higher within sequences are associated with blocky and upward-fining well-log patterns interpreted to reflect deposition in shoreline, paralic, and fluvial environments. Episodes of structural collapse of the Niger Delta clastic wedge appear to be associated with progradation of Agbada Formation sediments and the loading of underlying Akata Formation shales. Progradation may have been more rapid during third order eustatic sea level falls. Effects of syn-sedimentary deformation on patterns of sediment transport and deposition are more pronounced in lower sequences within the Agbada Formation, and include: 1) incision into foot walls of listric normal faults, 2) abrupt reorientation of channelized flow pathways across faults, and 3) thinning of deposits across crests of rollover anticlines on down thrown fault blocks. Structural controls on deposition are less pronounced within younger sequences and canyon incisions along sequence boundaries are more pronounced, suggesting that the locus of sediment accumulation and structural collapse of the clastic wedge moved farther basinward as accommodation was filled in the area of Delta field.

xii, 77 leaves : ill., appendices / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Electrical Engineering, 1973

Thesis (Ph.D.) -- University of Adelaide, Dept. of Electrical Engineering, 1973.

Thèses (M.Sc.)--Université de Sherbrooke (Canada), 2000. / Titre de l'écran-titre (visionné le 20 juin 2006). Publié aussi en version papier.

Saarbrücken, Univ., Diss., 1994. / Computerdatei im Fernzugriff.

Universiẗat, Diss., 1994--Saarbrücken.

Thesis (Ph.D.)--Boston University / [delta]'-Pyrazolines were prepared in which one or more of the groups R, Rl, R2, R3 are alkyl or phenyl and the other groups are hydrogen. In addition, the molecule was modified by the use of four other activating groups in the place of the carboxyl group, i.e. -CN, -CONH2 , -COCH3, and -No2. The compounds were decomposed thermally and the kinetics of the decomposition was followed by measuring the volume of nitrogen evolved as a function of time. From the data obtained, the rate constants and energies of activation were calculated. The purpose of the investigation was to determine the effects upon the rate constants and energies of activation produced by the alteration of the molecule at the above-indicated positions. The pyrazolines were prepared by the addition of diazomethane to the appropriate olefin, or by the addition of the appropriate diazoalkane to ethyl methacrylate. [TRUNCATED]

acase@tulane.edu / Natural systems can be altered, over a wide range of time scales, through changes in environmental conditions. In the Mississippi Delta, which has been shaped by changes in sediment deposition and sea level at the land-ocean interface over the Holocene, changes to environmental conditions lead to state changes that can be observed in both modern ecosystems and the depositional record. Alluvial strata (which comprise the bulk of the world’s sedimentary record) can provide insight into past triggers for ecosystem state changes and can be compared to modern monitoring data to paint a fuller picture of system response to environmental change. Given the large potential impact of anthropogenic climate change on natural systems, this combination of modern and paleo-environmental information may improve our ability to predict future conditions. This dissertation explores coastal and delta plain ecosystem responses to environmental change, particularly relative sea-level rise over annual to millennial timescales (Chapters 2 and 3) and rates of carbon storage by organic and clastic deposits in the Mississippi Delta (Chapter 4). Chapter 2 describes the results of an analysis of how subsidence and relative sea-level rise affect modern wetlands in coastal Louisiana. Using 274 rod surface-elevation table – marker horizon records, GPS measurements, and satellite altimetry data from the Gulf of Mexico, this chapter assesses present-day wetland vulnerability given current environmental conditions. Chapter 3 describes an analysis of how changes in past environmental conditions, specifically variable rates of relative sea-level rise, impacted marshes in the Mississippi Delta throughout the Holocene. Using 355 sediment cores, this chapter identifies relative sea-level rise tipping points that lead to marsh collapse and a state shift from marsh to open water. Using 14C dating, foraminiferal assemblage analysis, and stable isotope geochemistry, this chapter also estimates the time necessary for reestablishment of terrestrial conditions after an initial marsh collapse and conversion to open water at one selected location. Together, these results provide a framework for projecting likely marsh response to future increased rates of relative sea-level rise in coastal Louisiana. The combination of these studies provides a more complete picture of modern and future wetland vulnerability in coastal Louisiana and provides unique insights into the limitations of short-term observational studies of marsh conditions for projecting long-term outcomes in response to environmental change. Chapter 4 describes the results of a comparative analysis of carbon storage rates in organic and clastic deposits within the Holocene sedimentary record near Bayou Lafourche in the Mississippi Delta. Using 14C and OSL dating, elemental analysis, and bulk density measurements collected from three sediment cores, this chapter calculates carbon storage rates to determine the relative carbon storage efficiency of these deposits. This chapter provides an important comparison to similar work in deltaic deposits of the Wax Lake Delta. Furthermore, the high rates of carbon storage within the dominantly clastic deposits, which are interpreted as a proxy for planned sediment diversions in the region, provide an estimate for future carbon storage potential by these coastal restoration efforts. / 1 / Krista L. Jankowski

Increasing municipal and regional water demands have reduced freshwater inflows to the Nueces Delta. These flow reductions impair the marsh ecosystem’s functionality. As part of a United States Army Corps of Engineers multi-agency collaboration to restore the Nueces River and its tributaries, we have developed a mass-conservative hydrodynamic model to analyze fate and transport of freshwater and tidal inflows to the Nueces Delta. The model is built upon the LIDAR bathymetric data collected by the Coastal Bend Bays and Estuaries Program (CBBEP). Input data includes tidal, salinity, and wind data obtained from the Texas Coastal Ocean Observation Network (TCOON), pumping data from the Nueces River Authority, precipitation data from NOAA, and river flow from the USGS. The underlying modeling method uses conservative finite-difference/volume discretization on a Cartesian rectangular grid to simulate the movement of water and salt fluxes across the delta. Sub-models to represent the hydraulic influence of flow constrictions (e.g. railroads trestles, culverts) have been developed. The model’s response to forcing from wind, precipitation, and roughness were analyzed. The time to spin up for the model was analyzed and found to be approximately seven days. Preliminary validation of the model was qualitative but the overall trend of the tide coming in appears correct at the monitoring stations analyzed, indicating that the lowest frequency forcing of the tide and wind are correct. The effects of pumping into the delta were investigated under different pumping conditions to reveal the area inundation and impacts on salinity from pumping. / text