Browsing by Subject "University of Minnesota Medical School"

Now showing 1 - 9 of 9
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    Activation of the Inferior Olive
    (2011-04-13) Walter, Camille
    The inferior olive (IO) is a group of nuclei in the brainstem and is the sole origin of climbing fibers to the cerebellar cortex. While complete functions of the IO are unknown, it is believed to contribute to temporal processing. Functional magnetic resonance imaging (fMRI) studies have shown activation of the inferior olive by unexpected sensory stimuli. In this study, we tested the IO’s sensitivity to stimulus timing change to determine the time-change that is most efficient in activating the IO. We scanned normal human subjects while viewing sequences of visual stimuli and recognizing stimuli that deviated from isochronous stimuli by fifty to eight hundred milliseconds. The behavioral results showed that the subjects’ performance increased with timing change. The fMRI data were analyzed using event-related statistical parametric mapping of the hemodynamic responses; then we could see the activation of the inferior olive during all of the different stimulus timing changes. The 300 millisecond stimulus timing change produced the most activation of the IO, with time-changes of 200 to 600 (but not 50, 100, 700 or 800 ms) producing significant but less robust activation than 300 ms. These results were consistent with classical conditioning animal studies and indicate that reliable and robust activation of the inferior olive can be achieved in humans; they also can potentially be used to study diseases in which the IO is implicated.
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    Exercise and Psychological Stress: How Does Exercise Promote the Alleviation of Stress?
    (2011-04-13) Smith, Melissa
    Stress is an inevitable aspect of life, so how does one handle it on a daily basis? Exercise is an excellent coping mechanism for many. But how does exercise reduce stress? Previous research indicates a difference in cortisol levels, reactivity to, and recovery from stress (Jackson & Dishman, 2006).The purpose of this study was to examine cortisol levels between high and low fit groups as well as differences in reactivity to and recovery from stress. First, a fitness questionnaire was given to participants to assess total number of hours per week of exercise. Saliva samples were used to analyze cortisol levels and were obtained using a Salivette collection device. A saliva sample was first taken to establish baseline cortisol levels. Then, the participant completed a series of tasks in the following order: public speaking, mental arithmetic, and a cold pressor task followed by another saliva sample. Lastly, saliva samples were taken following a recovery period. An immunosorbent assay kit was used to measure cortisol levels in the saliva (IBL America, Minneapolis, MN). Following cortisol analysis, the fitness questionnaire was evaluated. Participants were divided into two groups based on a five hour per week median. Five or less hours was considered low fit (N=21) and more than five hours was considered high fit (N=24). A 2x7 ANOVA was used to analyze the differences in cortisol levels, reactivity, and recovery between high and low fit. A significant difference was found in cortisol levels between high and low fit participants (F4.1, 174=2.595, p= 0.036). High fit participants were also found to have greater reactivity to a stressor (F1, 42=3.780, p=0.059) as well as faster recovery from a stressor (F1, 42=7.656, p=0.008). These results imply that high fit individuals have lower overall cortisol levels and greater reactivity to and recovery from a stressor.
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    Fluorescence Analysis of the Sarcolipin:SERCA Protein Complex
    (2009-04-08) Rubin, John E.
    We have used fluorescence resonance energy transfer (FRET) to identify physical interactions between the sarcoplasmic reticulum Ca-ATPase (SERCA) and one of its regulatory proteins, sarcolipin (SLN), in cardiac and skeletal muscle. The sarcoplasmic reticulum (SR) is an intracellular membrane network found in muscle cells whose function is to uptake, store, and release calcium. SERCA functions to transport calcium into the SR to induce muscle relaxation. Theoretical models predict that SLN monomers regulate SERCA by binding the SERCA transmembrane domain, but SLN monomers also self-associate to form oligomers. To test these models, we expressed fluorescent fusion proteins of SLN and SERCA in Sf21 insect cells using the baculovirus system. Quantitative binding stoichiometries were determined by FRET measurements using live cell microscopy on plates coated with mollusk “glue” protein. FRET results indicate that (1) SLN monomers self-associate to form dimers and (2) SLN monomers interact with SERCA to form a 1:1 heterocomplex. We propose that SLN monomers compete in equilibrium between SLN oligomerization and SERCA binding.
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    Genetic Approach to Generating a Novel Mouse Model of Mammary Tumorigenesis
    (2011-04-13) Miller, Matthew
    Fibroblast growth factor receptors (FGFRs) and their ligands contribute to cellular functions including proliferation, survival, differentiation, migration, and angiogenesis. The growth factor receptor, FGFR1, chromosomal locus is amplified in 10% of breast cancer patients. Patients with this amplification do not respond well to current therapies and have been shown to develop a resistance to endocrine therapies, thus the inducible fibroblast growth factor receptor-1 (iFGFR1) was engineered. When activated, iFGFR1 promotes increased lateral budding of epithelial structures which develop into hyperplasias that progress to multicellular invasive lesions, characteristic of breast cancer. One pro-inflammatory protein upregulated by iFGFR1 activation is osteopontin. Osteopontin is a secreted glycophosphoprotein that is involved in a variety of different cancer types, including breast cancer. Data suggests that osteopontin is synthesized by breast carcinomas and acts to promote traits associated with increased aggressiveness. To study iFGFR1-induced osteopontin expression and the role osteopontin plays in cancer development and progression in mouse mammary glands in vivo, I developed a novel mouse model where mice are heterozygous for our FGFR transgene and osteopontin null (FGFR1 +/-; osteopontin -/-). In order to do this I backcrossed osteopontin -/- mice on a C57BL/6 genetic background to the FVB genetic background of the FGFR1 mice. The goal of this project was to master techniques in mouse husbandry and PCR-based genotyping as well as tissue staining. With the new transgenic mouse model we can better study the correlation between osteopontin levels and breast cancer in hopes of making osteopontin a targetable factor for therapeutic intervention.
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    The Identification of Girk Channel Domains that Facilitate Rapid and Efficient Coupling to G Protein- Coupled Receptors
    (2011-04-13) Young, Daniele
    G protein-gated inwardly rectifying potassium (GIRK or Kir3) channels constitute one subfamily of potassium-selective ion channels that regulate neuronal activity and heart rate. GIRK channels have been implicated in many biological processes, including pain perception, learning and memory, food intake, and reward. Structurally, GIRK channels consist of 4 subunits, able to form homotetramers or heterotetramers within the cell membrane. Activation of these channels occurs through a signal transduction cascade originating from ligandstimulated G-protein coupled receptors (GPCRs). This results in hyperpolarization of the cell membrane. With the variety of biological processes GIRK channels are involved in, understanding the interaction of the GPCR signaling cascade with GIRK channels could provide a beneficial therapeutic target. Using a variety of molecular biology techniques, I synthesized various chimeric proteins to investigate the GIRK channel and GPCR relationship, specifically focusing on amino acid residues promoting the coupling of GIRK1 with the GABAB receptor. Functional and biochemical assays in native systems suggest the Cterminal region and pore residue of the GIRK1 subunit are necessary to mediate a large receptor-induced response from the GIRK channel. Investigating this phenomenon further can determine how the identified GIRK1 channel domains are mediating efficient GABAB receptor coupling.
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    Injury by human complement causes large membrane lesions that reseal in IL-4-treated porcine endothelial cells
    (2011-04-13) Yeh, Alex
    Currently, successful xenotransplantation is restricted to theoretical conception due to the fact that an organism’s innate immune response rejects any tissue or organs transplanted from a different species. The complement system is a key component of this response in rejecting foreign substances, and mitigating the effects of this system could potentially revolutionize medical transplants. Complement system activation in an organism creates lesions in the membranes of foreign cells, leading to lysis and cell death. IL-4 is a cytokine, or a cell-signaling molecule, that seems to have a protective property against complement. Porcine endothelial cells first incubated in IL-4 exhibit decreased cell death after treatment with human complement, but the exact mechanism of protection is still unknown. A combination of the Neutral Red assay and the LDH assay were used to study cell recovery after complement treatment. Fluorescent microscopy was also used, in which labeled dextrans of different sizes were incubated with the cells along with complement. Should the mechanism of IL-4 protection be correctly identified, it may have potential uses in mitigating the innate immune response and the rejection of organs in xenotransplantation.
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    The Search for Novel Cancer Therapies : Catalytic Inhibition of Topoisomerase II by Substituted 9-aminoacridine Derivatives
    (2011-04-13) Etchison, Ryan; Jacobson, Blake; Dixon, Joe-Jay; Kratzke, Robert
    The objective of this research is to test the antiproliferative effects of four novel substituted 9-aminoacridine derivatives on lung cancer and to determine their viability as potential therapeutic agents for use in a clinical setting.
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    Sex Differences and Effects of Modafinil and Allopregnanolone on a Rat Model of Methamphetamine Relapse
    (2011-04-13) Rehbein, Tyler
    Modafinil (MOD) is an analeptic drug currently being examined as a treatment for stimulant dependence. This experiment examined MOD’s potential for use in treatment of methamphetamine (METH) addiction and further investigated the role of sex differences in drug-seeking behavior and treatment receptivity. The effects of allopregnanolone (ALLO), a progesterone metabolite that has been previously shown to reduce drug-seeking behavior in female rats, were also examined. Rats were trained to self-administer IV injections of METH during daily 5-hr sessions, and continued stable METH-seeking behavior over a 10 day maintenance period. Next, METH was replaced with saline, and drug-seeking behavior extinguished over an 18-day period. Following extinction, rats began a reinstatement procedure lasting 9 days in which an ALLO, MOD, or control pre-treatment injection was given 30 minutes prior to daily session, followed by a METH or saline priming injection that was given at the start of session. This reinstatement phase is considered an animal model of human relapse. Females showed greater responding on the previously METH-paired lever during reinstatement compared to males. MOD attenuated METH-seeking behavior equally in males and females, while MOD priming injections did not increase responding compared to saline control. ALLO attenuated METH-seeking behavior in females, but had no effect on males. These results illustrate the potential utility of MOD as a treatment for METH addiction and illustrate the role of gonadal hormones, such as ALLO, in the sex differences observed in drug-seeking behavior.