The role of reactive oxygen species in the stabilisation of hypoxia-inducible factor-1α (HIF-1α)

At physiological oxygen concentrations ([O2]) hypoxia-inducible factor-1α (HIF-1α) is constantly hydroxylated and thus prepared for proteosomal degradation through the action of the prolyl hydroxylases (PHDs) (Jiang et al., 1996). In hypoxia, however, the oxygen-sensitive PHDs are inhibited and HIF-1α is stabilised. Other agents, including cytokines and growth factors have been shown to stabilise HIF-1α at physiological [O2] through different mechanisms such as activation of the phosphatidylinositol 3-kinase (PI3K) or mitogen-activated protein kinase pathways (Semenza, 2003). Increased production of reactive oxygen species (ROS) during hypoxia have also been claimed to stabilise HIF-1α (Chandel et al., 1998) and we have now investigated the effect of endogenous ROS on HIF-1α stabilisation. HIF-1α stabilisation and ROS production in human embryonic kidney (HEK 293T) cells were determined by immunoblotting and the use of fluorescent probes, respectively. γGlutamyl cysteine synthetase (γGCS) is the rate limiting enzyme of glutathione (GSH) biosynthesis and therefore a crucial antioxidant. We used small interfering RNA (siRNA) to silence this enzyme and thus impair the capacity of the cells to detoxify ROS. In order to determine whether mitochondria are a major source of ROS we used cells depleted of mitochondrial DNA (Rho0); these were characterised in vitro by monitoring oxygen consumption. RT-PCR was used to determine mitochondrial DNA content and immunoblotting to assess mitochondrial-encoded protein expression. The effects of a Rho0 phenotype were then assessed in relation to HIF-1α stabilisation and ROS production. HIF-1α is stabilised in an oxygen-dependent manner. HIF-1α stabilisation at low [O2] (3%), but not at 0.5% O2 is prevented by treatment with antioxidants. Silencing γGCS augmented free radical production in HEK 293T cells. This was associated with HIF-1α stabilisation at ambient [O2] (21%) and could be prevented by treatment with antioxidants. Rho0 cells produced less ROS than wild-type cells and did not stabilise HIF-1α either at low [O2] (3%) in wild-type cells or at 21% O2 in γGCS silenced cells. The data suggest that HIF-1α can be stabilised by ROS generated by the mitochondria

A choice system for environmental design and development.

Massachusetts Institute of Technology. Dept. of City and Regional Planning. Thesis. 1969. Ph.D.Vita.Bibliography: leaves 182-185.Ph.D

Interpreting the transnational material culture of the 19th-Century North American Plains Indians: creators, collectors, and collections

Doctor of PhilosophyDepartment of HistoryBonnie Lynn-SherowAmerican Indian material culture collections are protected in tribal archives and transnational museums. This dissertation argues that the Plains Indian people and Euroamerican people cross pollinated each other’s material culture. Over the last two hundred years’ interpretations of transnational material culture acculturation of the 19th - Century North American Plains Indians has been interpreted in venues that include arts and crafts, photography, museums, world exhibitions, tourism destinations, entertainments and literature. In this work, exhibit catalogs have been utilized as archives. Many historians recognize that American Indians are vital participants and contributors to United States history. This work includes discussions about North American Indigenous people and others who were creators of material culture and art, the people who collected this material culture and their motives, and the various types of collections that blossomed from material culture and oral history proffering. Creators included Plains Indian women who tanned bison hides and their involvement in crafting the most beautiful art works through their skill in quillwork and beadwork. Plains Indian men were also creators. They recorded the family’s and tribe’s histories in pictograph paintings. Plains Indian storytellers created material that was saved and collected through oral tradition. Euroamerican artists created biographical images of the Plains Indian people that they interacted with. Collections of objects, legends, and art resulted from those who collected the creations made by the creators. Thus today there exists fine examples of ethno-heirlooms that pay tribute to the transnational acculturation and survival of the American Indian people of the Great Western Northern American Plains. What is most important is the knowledge, and an appreciation for the idea that a transnational cross-pollination of cultures enriched and became rooted in United States history

The influence of thermal maturity on the stable isotope compositions and concentrations of molybdenum, zinc and cadmium in organic-rich marine mudrocks

The concentrations and isotopic compositions of molybdenum (Mo), zinc (Zn) and cadmium (Cd) in organic-rich marine mudrocks may be used to characterize ocean chemistry in the geological past. These approaches rely on the rarely tested assumption that the geochemical signatures of these metals are not affected by the thermal maturation of the organic matter with which they are associated. We have conducted a series of artificial maturation experiments on two well-known immature organic-rich mudrocks, the Kimmeridge Blackstone Band (Late Jurassic age), and the Posidonia Shale (Early Jurassic age). These pyrolysis experiments allow us to trace changes in the composition of organic matter through varying stages of maturation, and the concentration and isotopic compositions of metals in rock residues and evolved organic fluids. Our results indicate that the thermal maturation of organic matter does not result in significant alteration of the isotopic compositions of Mo, Zn and Cd in the rock residues, which thus retain primary palaeodepositional information. Systematic increases in the concentrations of Mo, Zn and Cd in rock residues with progressively higher thermal maturity are attributed to the loss of substrate mass in the form of fluids released during pyrolysis-induced cracking of kerogen, and to the relatively low concentrations of Mo, Zn and Cd in these fluids. The Mo-isotope compositions of fluids produced during pyrolysis are isotopically similar to the bulk rock; in contrast the isotopic composition of Zn in organic fluids is ∼0.4–0.6‰ lighter than the bulk rock. The progressive loss of organic matter from rock residues during maturation coupled with the increases in metal concentrations leads to an increase of metal/TOC ratios, which may be up to double their original (syn-depositional) value in thermally mature rocks. This observation must be taken into account when using metal/TOC ratios as proxies for oceanic metal inventories throughout geological time. Finally, calculations using the mass of asphaltenes recovered during the pyrolysis experiments suggest that organically bound Mo, Zn and Cd account for several percent of the total rock metal inventory