Browsing by Subject "Freezing"
Now showing 1 - 4 of 4
Results Per Page
Sort Options
Item Algorithm Optimization of non-DMSO Cryopreservation Protocols to Improve Mesenchymal Stem Cell Post-Thaw Function(2016-09) Pollock, KathrynMesenchymal stem cells (MSCs) are a common transfusion cell therapy that have been used in over 300 clinical trials to treat over 2000 patients with diseases ranging from Crohn’s disease to heart failure. These cells are frequently cryopreserved to better coordinate the timing of cell administration with patient care regimes and to accommodate transport of samples between different sites of collection, processing, and administration. However, cryopreservation with DMSO (the current gold standard) can result in poor cell function post-thaw and adverse reactions upon infusion. We hypothesize that non-DMSO cryopreservative molecules, including sugars, sugar alcohols, amino acids, and other small molecule additives, can be used in combination to protect cell viability and function post-thaw. This research demonstrates that some combinations of non-DMSO cryopreservatives preserve cell functionality better than others, and these effects are dependent not on osmotic or physical changes in solution, but on biological changes that affect the cell during the freezing process. We observe that there is likely a sweet spot concentration combination that produces maximum recovery for each combination of molecules, and demonstrate that an evolutionary algorithm can be used to identify optimized combinations of molecules that yield high cell recovery post-thaw. Additionally, we demonstrate that these novel solutions maintain MSC functionality when evaluated using surface markers, attachment, proliferation, actin alignment, RNA expression, and DNA hydroxymethylation. These advances in cryopreservation can improve cell therapy, and ultimately patient care.Item An ecological and evolutionary perspective on functional diversity in the genus Salix(2010-05) Savage, Jessica AnneNatural selection, along with biochemical and architectural constraints can limit the trait combinations expressed by plants, creating functional trade-offs across species. These trade-offs often play a critical role in limiting species distributions by preventing them from performing well under all environmental conditions. For this dissertation, I examined the role of functional trade-offs in limiting species distributions at two geographic scales, focusing on species in the genus Salix (the willows). First, I examined whether species exhibited niche differentiation across a local water availability gradient, and investigated the extent that plant function and functional similarity influence species distributions and patterns of co-occurrence. For this analysis, I examined species distributions in relation to physiological and functional data collected in the field and in a greenhouse common garden. I also estimated a phylogeny of the species to examine patterns of species phylogenetic community structure and trait evolution. Second, I examined whether there was evidence for a trade-off between freezing tolerance and growth that could explain species range limits. This analysis involved comparing species freezing tolerances and growth rates under different environmental conditions and determining the extent that these traits related to species distributions. Overall, I found evidence that functional trade-offs are important in determining species distributions both within local plant communities and across broader geographic distributions. On a local level, species exhibit niche differentiation across a water availability gradient, and this differentiation is driven by a functional trade-off between drought tolerance and relative growth rate. Traits related to species drought tolerance and recruitment strategies also demonstrate correlated evolution with species water availability niches. At a broader geographic scale, species demonstrate a trade-off between freezing tolerance and growth. This trade-off is primarily the result of species dependence on photoperiod cues for growth regulation. The strong correlation between species growth rates, their freezing tolerances, and their modeled geographic ranges suggests that this trade-off could influence their geographic distributions. This research demonstrates the importance of functional trade-offs in determining the distributions of species in an ecological and economically important genus. It also demonstrates the value of integrative research that draws on physiological, evolutionary and ecological methodology.Item Heterogeneous protein distribution during rapid and equilibrium freezing(2013-04) Twomey, Alan MichaelInteractions between proteins and ice were studied in situ using FTIR and confocal Raman microspectroscopy under equilibrium and non-equilibrium conditions over a range of temperatures. During quasi-equilibrium freezing of aqueous solutions of dimethyl sulfoxide (DMSO) and bovine serum albumin, preferential exclusion of albumin and/or DMSO was observed. It was hypothesized that the albumin may be adsorbed onto the ice interface or entrapped in the ice phase. To investigate protein-ice interactions during freezing under non-equilibrium conditions, confocal Raman microspectroscopy was used to map the distribution of albumin and the cryoprotective agent trehalose. Microheterogeneity was found in the composition of the freeze-concentrated liquid phase that indicated that albumin was preferentially distributed near or at the boundary of the ice phase. The observed microheterogeneity did not occur under all freezing protocols, which suggests that the technique developed here could be used to develop freezing protocols that would reduce harmful protein-ice interactions.Item OT WARTS?(2012-09-24) Zant, Melissa