Browsing by Subject "Disease"
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Item The role of cellular calcium channels in planarian biology(2011-11) Zhang, DanIdentification of signaling pathways and therein drugable targets, to manipulate stem cell behavior in vivo is a major focus of regenerative medicine. This dissertation focuses on the role of Ca2+ channels in stem cell differentiation and regeneration in a simple in vivo model, the planarian flatworm. These animals maintain a totipotent population of stem cells that give rise to all the cell types in the worm. Previously, we discovered that the isoquinoline drug praziquantel (PZQ) caused a robust (100%) and complete duplication of the entire anterior-posterior (AP) axis during flatworm regeneration to yield two-headed (bipolar) organisms. My studies mechanistically dissect these observations to show that PZQ subverted regeneration via activation of a specific neuronal voltage-gated Ca2+ channel (VGCC) isoform (Cav1A). Surprisingly, another isoform Cav1B was found to play opposing roles in axis formation to promote tail regeneration, suggesting a delicate interplay between Ca2+ signals critical for nervous system regeneration. Further dissection of the downstream pathway showed that RNAi of Cav1A blocked PZQ-evoked bipolar regeneration, Ca2+ entry and decreases in Wnt levels, the output of Hedgehog signaling. Thus, these data demonstrated that calcium signaling regulated regeneration through modulating Hedgehog signaling, a pathway that has been shown to regulate neuronal stem cell behavior, patterning and growth in diverse development processes. Taken together, these findings add new insights into the mechanisms that govern planarian regeneration. Additionally, my work on intracellular Ca2+ release channels in this system led to the identification of the planarian inositol 1, 4, 5-trisphosphate receptor (IP3R). Studies designed to elucidate the biological significance of this protein by in vivo RNAi knockdown led to the discovery that sexual planarians underwent severe defects of laying eggs in the absence of IP3R, although it failed to produce an obvious phenotype in asexual worms. Thus, these data provided genetic evidence that IP3R plays an important role in regulating reproductive physiology in planarian flatworms. In summary, the data obtained in this thesis have revealed essential roles of Ca2+ signaling in regulating planarian stem cell differentiation and reproductive physiology.Item Source, Summer 2016(University of Minnesota Extension, 2016) University of Minnesota ExtensionItem Transcriptional and functional study of Arabidopsis defence response against Pseudomanas syringae.(2009-01) Wang, LinUsing a reverse genetic approach, we investigated genes that are potentially important for disease resistance against the bacterial pathogen of Arabidopsis thaliana: Pseudomonas syringae. Genes that were induced at least two-fold after infection by Pseudomonas syringae pv. maculicola ES4326 were chosen as candidates for our study. Arabidopsis T-DNA mutants were ordered and assayed for bacterial growth. Mutants that consistently supported more bacterial growth than wild type controls were selected for further analysis. We also monitored expression profiles of wild-type plants and mutants with defects in key components of the defense signaling network using a microarray. The data were used to model the Arabidopsis defense network 24 hours after infection by Pseudomonas syringae pv. maculicola strain Psm ES4326. From the identified novel genes that are likely important for plant defense, I chose two members from the Arabidopsis CBP60 family, CBP60g and CBP60h, for functional analyses. Mutants of CBP60g and CBP60h are more susceptible to bacterial infection than wild type. They accumulated less SA in response to MAMP (Microbe Associated Molecular Pattern) and/or pathogen inoculations. CBP60g binds to calmodulin and the calmodulin binding is important to its function in disease resistance and SA signaling. In contrast, CBP60h does not bind calmodulin and seems to function independently of calcium signaling. A cbp60g and cbp60h double mutant is highly susceptible to Pseudomonas syringae infection; it is more susceptible than sid2 and comparable to pad4. It is likely that CBP60g and CBP60h share partially redundant and crucial functions in defense signaling. The cbp60g and cbp60h double mutant was also found to affect both SA-dependent and independent signaling pathwaysItem Utility of the Visible Heart® and Micro-CT Imaging to Optimize the Treatments of Bifurcation Stenting(2021-05) Valenzuela, ThomasUsing the Visible Heart® Apparatus and methodologies allows for the ability to reanimate large mammalian hearts, including human, and thus to perform bifurcation stenting in an in vitro setting. This allows for novel uses of multimodal imaging for assessing/testing previous, current and future clinical recommendations for bifurcation techniques, without risking a living patient. After performing such procedures, high resolution 3D models were obtained via micro-CT imaging, which then allows for post implant device/tissue interface analyses. Utilizing reanimated swine hearts, we were able to uniquely visualize how the various bifurcation techniques performed could be optimized in specific anatomies. These findings again confirm that the Visible Heart® Apparatus is a valuable platform that should be used to further understand how next generation stents and/or bifurcation techniques can best be utilized. Recently, our laboratory also had the privilege to perform bifurcation stenting within three reanimated human hearts using the same methodologies. Additionally, similar PCI procedures were performed in three perfusion-fixed human hearts as further means to compare the differences in stenting technique and to identify potential differences between procedures performed in fixed versus reanimated human hearts. Also, it was identified that after the formalin fixation process, desecrations of the coronary vessels could readily be induced in healthy human hearts, while those presenting with coronary artery disease elicited little to no effects due to the plaque formations. If this holds true, this will open the Visible Heart® Laboratories’ human heart library of over 580 specimens, to perform clinically relevant bifurcation stenting techniques. Finally, a novel research method of detecting stent malappositions was created, as the current standard for intracoronary imaging, optical coherence tomography (OCT), has its limitations when there are multiple stents implanted. This method was then used alongside OCT in a step-by -step bifurcation intervention performed in a formalin fixed human heart. It was shown that stent apposition continuously improves if the operator adheres to the latest published guidelines; however future investigations should be performed in more diseased human hearts from the Visible Heart’s human heart library to focus on other bifurcation techniques and the consequences of straying from these guidelines in each case.