Browsing by Subject "Stem"

Now showing 1 - 5 of 5
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    Chromatin accessibility and its relationship to pluripotency and the induction of pluripotent stem cells
    (2015-01) Espland, Eric
    Chromatin within stem cells is dynamic and relaxed, allowing transcription and thus lineage specification to occur rapidly. To determine how this property can be used to enhance the generation of induced pluripotent stem cells (iPSC), I examined whether the expression of histone variants or peptidyl-prolyl isomerases (Ppiases) could increase the hyperdynamic, plastic nature of stem cell chromatin and thereby increase the efficiency and speed of reprogramming. I used molecular cloning to generate expression vectors containing the histone variants H3T and H2A.B. I used line-scanning microscopy to measure chromatin dynamics, with initial results suggesting that stem cells are more hyperdynamic in nature than differentiated cells. Although the research on the effect of histone variants and Ppiases on chromatin dynamics and reprogramming was not completed, another study showed that the expression of other histone variants does enhance reprogramming and may also induce an open chromatin structure. If this holds true for the histone variants studied here or Ppiase B (PpiB), this could further enhance the generation of iPSC and make future autologous engraftments of iPSC more feasible.
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    Functional leaf and stem traits of the Oaks of the Americas
    (2020-06-26) Kaproth, Matthew A; Hahn, Marlene; Manos, Paul S; Hipp, Andrew L; González-Rodríguez, Antonio; Cavender-Bares, Jeannine; cavender@umn.edu; Cavender-Bares, Jeannine; Oaks of the Americas Group
    Leaf and stem trait data: Measured interspecific variation of Quercus (L.) - totaling 15+ functional traits for 135* American oak species. Our goal was to hand-measure/characterize as many North American species as possible. Measurements include: (1) specific leaf area (SLA, mm2 mg), an important leaf economic spectrum (LES) trait associated with leaf lifespan, resource acquisition, and nutrient use (Wright et al., 2004; Reich, 2014), (2) perimeter per unit leaf area (PLA, cm−1), a leaf trait that increases with degree of lobing and decreases with leaf size and is associated with hydraulic conductance and boundary layer resistance for all species (Sack et al., 2003; Kaproth and Cavender‐Bares, 2016), (3) total length of major veins per area (cm−1), associated with leaf hydraulic function (Sack and Scoffoni, 2013), (4) leaf length (mm), (5) petiole length (mm), and (6) stem specific density (g·cm−3), associated with mechanical strength and drought tolerance (Cornelissen et al., 2003; Kunstler et al., 2015). Specimens from sunlit branches were pressed and dried alongside samples collected for herbarium specimens as part of the Oaks of the Americas Project (Hipp et al., 2018).
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    Genetics, Sources, and Mapping of Stem Rust Resistance in Barley
    (2017-04) Case, Austin
    Stem rust is a devastating disease of cereal crops worldwide. In barley (Hordeum vulgare), the disease is caused by two pathogens: Puccinia graminis f. sp. secalis (Pgs) and Puccinia graminis f. sp. tritici (Pgt). In North America, the stem rust resistance gene Rpg1 has protected barley from losses for more 60 years; however, widely virulent Pgt races from Africa in the Ug99 group threaten the crop. To identify novel quantitative trait loci (QTL) for stem rust resistance, bi-parental and association mapping studies were undertaken in the Barley iCore Collection (BCC) held by the USDA National Small Grains Collection. Association mapping studies of the BCC were conducted for seedling resistance to Pgt race TTKSK (Ug99 group) in the greenhouse and adult plant resistance (APR) to Pgt TTKSK composite in Njoro, Kenya and Pgt race QCCJB in St. Paul, MN. A major effect QTL (Rpg-qtl-5H-11_11355) for APR in all locations was identified on chromosome 5H. This QTL represents a unique locus for APR and has been confirmed in other studies. Subsequently, 290 of the most resistant BCC accessions, the BCC Selects (BCCS), were screened for resistance Pgt races MCCFC, QCCJB, HKHJC, TTKSK, TTKST, TKTTF, and TRTTF, and also Pgs isolate 92-MN-90. From this investigation, four BCCS accessions were postulated to carry Rpg1, 14 to carry Rpg2, 91 to carry Rpg3, four to carry rpg4/Rpg5, and 59 to carry potentially novel resistance genes. To map the APR genes of Rpg2 and Rpg3 in Hietpas-5 (CIho 7124) and GAW-79 (PI 382313), respectively, two biparental populations were developed with Hiproly (PI 60693), a stem rust susceptible accession. Both populations were phenotyped to the domestic Pgt races of MCCFC, QCCJB, and HKHJC in St. Paul and to Pgt TTKSK composite in Njoro. In the Heitpas-5/Hiproly population, a major effect QTL was identified on chromosome 2H, which is proposed as the location for Rpg2. In the GAW-79/Hiproly population, a major effect QTL was identified on chromosome 5H and is the proposed location for Rpg3. The resistance sources identified and characterized in this study enhance barley breeding programs focused on stem rust resistance.
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    Stabilized CD16a Expression on Pluripotent Stem Cell-Derived Natural Killer Cells
    (2015-12) Blum, Robert
    Human embryonic stem cells (hESC) and induced pluripotent stem cells (iPSC) have been shown to successfully generate functional hematopoietic cells of multiple lineages. One of the cells that these studies have shown is possible to generate are cytotoxic natural killer (NK) cells. These pluripotent stem cell-derived NK cells could potentially be used as a cell-based therapy to treat a wide range of cancers. A potent method through which NK cells kill their targets is antibody-dependent cell-mediated cytotoxicity (ADCC). During this process an Fc gamma receptor, CD16a, recognizes antibody coated target cells and leads to the stimulation of the NK cell’s cytotoxic pathways. However, upon CD16a activation, a metalloprotease known as ADAM17 has been shown to cleave CD16a leading to a decrease in NK cell ADCC. This project seeks to generate genetically modified NK cells that have CD16a expression stabilized to maximize ADCC. One method to accomplish this is the generation of a non-cleavable version of CD16a. This cDNA construct has been transfected into iPSCs using Sleeping Beauty transposase to stably express CD16a. These cell’s CD16a molecules are resistant to cleavage upon cell activation and are also highly expressed on the surface of the NK cells. Preliminary testing has shown that when combined with antibodies specific to their cognate target ligand, these cells have a greater cytolytic response than untransfected peripheral blood NK cells (PBNK). Also, CRISPR-Cas9 has been employed to knock-out ADAM17. Going forward, comparing the cytotoxicity of these two NK cells will show which is best to employ in the treatment of cancers that express ligands for therapeutic antibodies that have proven refractory to other therapies and adjuvants.
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    A study of grade level and gender differences in divergent thinking among 8th and 11th graders in a Mid-Western school district.
    (2011-10) Roue, Leah Christine
    This research study compared gender and grade level differences in divergent thinking among middle school and high school students in the Midwest, in an attempt to determine whether gender or grade level-based differences exist in divergent thinking. The instrument used was based on the Wallach and Kogan Creativity Test (WKCT). There were 166 public school students in the study from the 8th and 11th grades. The results were analyzed in an effort to answer two research questions: Are there gender differences in fluency, flexibility, or originality of a response? Are there grade level (age) differences in fluency, flexibility, or originality of a response? Quantitative and qualitative reporting is used.