A Lifetime to Learn

Second place winner of the MSU Maroon & White QEP/Maroon Edition Essay Competition (Upperclassmen) for 2016/2017

Uranium solubility in high temperature, reduced systems

The traditional paradigm declares tetravalent uranium to be immobile under reducing conditions – an assumption widely employed for nuclear waste management strategies. In contrast, experiments presented here demonstrate this assumption, although valid for low temperatures, can be erroneous for high temperature natural systems. This project focuses on the ability of sulfate-bearing solutions to transport uranium at reduced conditions and elevated temperatures, identifies the new species U(OH)2SO4, derives thermodynamic constants necessary for modeling, and expands the quantifiable range of U4+ mobility to more neutral pH conditions. The data obtained enable more accurate assessment of uranium mobility by updating the existing uranium thermodynamic databases and is applicable to uranium fluid transport in oreorming systems and nuclear waste repositories

Differences in navigation performance and postpartal striatal volume associated with pregnancy in humans.

Pregnancy is accompanied by prolonged exposure to high estrogen levels. Animal studies have shown that estrogen influences navigation strategies and, hence, affects navigation performance. High estrogen levels are related to increased use of hippocampal-based allocentric strategies and decreased use of striatal-based egocentric strategies. In humans, associations between hormonal shifts and navigation strategies are less well studied. This study compared 30 peripartal women (mean age 28 years) to an age-matched control group on allocentric versus egocentric navigation performance (measured in the last month of pregnancy) and gray matter volume (measured within two months after delivery). None of the women had a previous pregnancy before study participation. Relative to controls, pregnant women performed less well in the egocentric condition of the navigation task, but not the allocentric condition. A whole-brain group comparison revealed smaller left striatal volume (putamen) in the peripartal women. Across the two groups, left striatal volume was associated with superior egocentric over allocentric performance. Limited by the cross-sectional study design, the findings are a first indication that human pregnancy might be accompanied by structural brain changes in navigation-related neural systems and concomitant changes in navigation strategy

Expression of glial fibrillary acidic protein and its relation to tract formation in embryonic zebrafish ( Danio rerio )

To address possible roles of glial cells during axon outgrowth in the vertebrate central nervous system, we investigated the appearance and distribution of the glial-specific intermediate filament, glial fibrillary acidic protein (GFAP), during early embryogenesis of the zebrafish ( Danio rerio ). Immunopositive cells first appear at 15 hours, which is at the time of, or slightly before, the first axon outgrowth in the brain. Immunopositive processes are not initially present in a pattern that prefigures the location of the first tracts but rather are distributed widely as endfeet adjacent to the pia, overlying most of the surface of the brain with the exception of the dorsal and ventral midline. The first evidence for a specific association of immunopositive cells with the developing tracts is observed at 24 hours in the hindbrain, where immunopositive processes border axons in the medial longitudinal fasciculus. By 48 hours, immunopositive processes have disappeared from most of the subpial lamina and are found exclusively in association with tracts and commissures in three forms: endfeet, radially oriented processes, and tangentially oriented processes parallel to axons. This last form is particularly prominent in the transverse plane of the hindbrain, where they define the boundaries between rhombomeres. These results suggest that glial cells contribute to the development and organization of the central nervous system by supporting early axon outgrowth in the subpial lamina and by forming boundaries around tracts and between neuromeres. The results are discussed in relation to previous results A neuron-glia interactions and possible roles of glial cells in axonal guidance. © 1995 Wiley-Liss, Inc.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/50065/1/903590302_ftp.pd