Ischemia is characterized by reduced blood flow to an area of the body which can then cause cellular injury through the generation of reactive oxygen species (ROS), activation of inflammation, and induction of apoptosis. Although rapid reestablishment of flow is required to prevent organ death, the reperfusion phase of this injury can cause its own deleterious effects often exacerbating the initial insult. The combined action of the two injuries is termed ischemia/reperfusion (I/R) injury. Oxidative stress that results from ischemia/reperfusion injury is a common pathological condition that accompanies many human diseases including stroke, heart attack and traumatic injury. In addition, neurodegenerative diseases including Parkinson’s, Alzheimer’s, and Huntington’s disease appear to involve oxidative stress. Although actively investigated by the medical and pharmaceutical industry; limited progress has been made to ameliorate I/R injury and to date there is no drug approved for treatment for I/R injury. Therapeutic approaches to treat I/R injury have included the administration of compounds to scavenge ROS or induce protective pathways or genetic responses. It was previously reported that caffeic acid phenethyl ester (CAPE), a plant-derived polyphenol, displayed cytoprotective effects against menadione (MD)-induced oxidative stress in human umbilical vein endothelial cells (HUVEC), and the induction of heme oxygenase-1 (HMOX1), a phase II enzyme, played an important role for CAPE cytoprotection. In an effort to improve this cytoprotection, other phase II enzyme inducers were investigated and, 2-cyano-3,12 dioxooleana-1,9 dien-28-imidazolide (CDDO-Im) and 2-cyano-3,12-dioxooleana-1,9-dien-28-oyl methyl ester (CDDO-Me), were found to be potent inducers with a rapid onset of action. CDDO-Im and CDDO-Me, synthetic olenane triterpenoids, developed as anticancer agents were compared to CAPE revealing that CDDO-Im was a more potent inducer of Phase II enzymes including HMOX1 and provided better cytoprotection than CAPE. Gene expression profiling showed that CDDO-Im was more potent inducer of protective genes like HMOX1 than CAPE and additionally induced heat shock proteins. To better understand the mechanism of action of CDDO-IM, a gene expression time-course was undertaken to identify early initiators of the transcriptional response preceding cytoprotection. Application of systems pharmacology identified molecular networks of cell mediating processes.

SAMMANFATTNING Hjärt-kärlsjukdom är det största folkhälsoproblemet för både män och kvinnor i Sverige. I hjärtkärlsjukdom inkluderas kranskärlsjukdom (koronarsjukdom), plötslig hjärtdöd, hjärtsvikt, claudicatio intermittens, stroke och övriga hjärtkärlmanifestationer (Schenk-Gustafsson, 2011). Hjärtinfarkt är den vanligaste dödsorsaken för kvinnor över femtiofem år och män över fyrtiofem år i Sverige (Schenck-Gustafsson, 2011). Mortaliteten i hjärt-kärlsjukdomar sjunker i Sverige och kvinnors medelöverlevnad är fortfarande högre än männens, men denna skillnad har minskat då hjärtsjukvården har förbättrats. Kvinnors medelöverlevnad har sjunkit från 84 till 81 år det senaste decenniet medan männens medelöverlevnad har ökat från 75 till 78 år. Antalet hjärtinfarkter hos svenska kvinnor kan komma att öka på grund av livsstilsfaktorer såsom rökning och psykosociala faktorer. Det pågår en diskussion bland forskare om kvinnor får sämre vård än män och om kvinnor upplever symtom annorlunda än män vid kranskärlssjukdom. Studier har visat att kvinnor har längre fördröjning än män för att söka hjälp vid insjuknandet i kranskärlssjukdom. Syftet var att belysa kvinnors upplevelse av symtom och hur de hanterar dessa symtom i samband med insjuknandet i akut kranskärlssjukdom. För att få svar på syftet valdes litteraturöversikt som metod. Arton artiklar identifierades och inkluderades i denna litteraturöversikt. Sju av artiklarna hade kvalitativ ansats och elva artiklar hade kvantitativ ansats. Slutsatsen var att kvinnor upplevde prodromala symtom månader/år innan kranskärlsdiagnosen ställdes och det var ovanligt att kvinnor sökte sjukvård för dessa symtom. Bröstsmärta var det vanligaste symtomet hos kvinnor vid insjuknande i kranskärlssjukdom men ospecifika symtom förekom också. Kvinnor upplevde illamående i högre grad än män i detta sammanhang. Kvinnor hanterade symtom på kranskärlssjukdom genom att kontakta anhöriga eller med självmedicinering innan de kontaktade sjukvården, vilket bidrog till fördröjning av vården. Kunskapsnivå, känslomässiga och psykosociala faktorer inverkade på hur kvinnor hanterade symtom på kranskärlssjukdom. Sjukvården och kvinnor behövde ökad kunskap och förståelse angående hur kvinnor upplevde symtom på kranskärlssjukdom och hur kvinnor hanterade dessa symtom.

The main goal of this dissertation was to investigate if rehabilitative training after ischemic damage can increase cell proliferation and encourage the differentiation and maintenance of newly formed neurons. For all studies, I utilized a rehabilitative training task which has repeatedly been found to enhance behavioral performance after ischemic lesions of the sensorimotor cortex. Training was focused on the impaired forelimb in order to (1) target forelimb deficits induced by the lesions and (2) engage remaining cortex in potential plastic events. The level of cell proliferation was investigated by measuring and phenotyping cells labeled with a mitotic marker (bromodeoxyuridine) in the peri-lesion area and various other regions. First, in an animal model of cortical ischemia, the level of cell proliferatoin measured in rehabilitated animals after ischemic damage was significantly decreased in peri-lesion cortex compared to non-rehabilitated animals. In order to investigate which component of cell generation, proliferation or maintenance, was affected by rehabilitative training, pulse labeling of new cells followed by short or long term training periods was accomplished. This study revealed thatrehabilitative training had increased cell proliferation that occurred early after ischemic damage and the maintenance of these early generated cells were significantly increased in the peri-lesion cortex of rehabilitated animals compared to controls. Lastly, in order to verify the results of the first study (experience induced reduction of new cells in periinfarct tissue) pulse labeling of new cells during a mid-time point of rehabilitation period after ishemic lesions was employed and resulted in the same significantly reduced level of new cells in peri-infarct tissue of rehabilitated animals compared to controls. In all studies, the proportion of the neuronal and astrocyte phenotype of newly generated cells was not significantly affected by rehabilitative training after ischemic damage. However, a significant increased accumulation of new microglia was seen in rehabilitated animals, but reactive microglia produced early after ischemic damage were not significantly maintained which indicates a possible dual role that microglia during post-operative rehabilitative training. Together these studies indicate that functionally beneficial behavioral experience can affect cell proliferative responses, and mainitenance of newly generated non-neuronal cells early after ischemic damage. / text

The aim of this study was to determine motor unit firing patterns during ischemic versus non-ischemic sustained submaximal isometric contractions of the tibialis anterior muscle. 10 healthy adults attended two experimental sessions approximately 48 hours apart. Both sessions were identical except that the fatigue task in one was performed with a pressure cuff placed above the knee and inflated to 180 mm Hg. Three 5s maximum voluntary contractions (MVCs) were performed prior to and after the fatigue task. Each participant held a target force of 20% MVC until endurance time (peak-to-peak tremor amplitude exceeded 5% MVC). Single motor unit firing rates (11 non ischemic, 9 ischemic) were recorded with intramuscular fine wire electrodes. Mean interspike intervals over 5s time bins were calculated at every 5% endurance time. The endurance time for the ischemic (3.7 ± 0.58 min) fatigue task was significantly (p<0.001) shorter than the non-ischemic (9.5 ± 0.57 min) task. There was no significant difference in mean motor unit firing rates between the two conditions (p=0.883). Within both tests, there was a significant decline in firing rate (ischemic initial: 12.95 ± 0.71 Hz, minimum: 11.41 ± 0.81 Hz, p=0.023; non-ischemic initial: 13.13 ± 0.87 Hz, minimum: 11.15 ± 0.48 Hz, p=0.012). The time to minimum firing rate was significantly (p<0.001) less in the ischemic (1.29 ± 0.2 min) compared to non-ischemic (3.14 ± 0.23 min) condition. Muscle ischemia significantly reduced endurance time and the time to minimum firing rate. However, there were no differences in average motor unit firing rates between the two conditions across the relative phases of endurance time. / text

published_or_final_version / abstract / toc / Physiology / Master / Master of Philosophy

published_or_final_version / Physics / Master / Master of Philosophy

published_or_final_version / Anatomy / Master / Master of Philosophy

No description available.

The work described in this dissertation was motivated by a desire to better understand the cellular pathology of ischemic stroke. Two of the three bodies of research presented herein address and issue directly related to the investigation of ischemic stroke through the use of diffusion weighted magnetic resonance imaging (DWMRI) methods. The first topic concerns the development of a computationally efficient finite difference method, designed to evaluate the impact of microscopic tissue properties on the formation of DWMRI signal. For the second body of work, the effect of changing the intrinsic diffusion coefficient of a restricted sample on clinical DWMRI experiments is explored. The final body of work, while motivated by the desire to understand stroke, addresses the issue of acquiring large amounts of MRI data well suited for quantitative analysis in reduced scan time. In theory, the method could be used to generate quantitative parametric maps, including those depicting information gleaned through the use of DWMRI methods. Chapter 1 provides an introduction to several topics. A description of the use of DWMRI methods in the study of ischemic stroke is covered. An introduction to the fundamental physical principles at work in MRI is also provided. In this section the means by which magnetization is created in MRI experiments, how MRI signal is induced, as well as the influence of spin-spin and spin-lattice relaxation are discussed. Attention is also given to describing how MRI measurements can be sensitized to diffusion through the use of qualitative and quantitative descriptions of the process. Finally, the reader is given a brief introduction to the use of numerical methods for solving partial differential equations. In Chapters 2, 3 and 4, three related bodies of research are presented in terms of research papers. In Chapter 2, a novel computational method is described. The method reduces the computation resources required to simulate DWMRI experiments. In Chapter 3, a detailed study on how changes in the intrinsic intracellular diffusion coefficient may influence clinical DWMRI experiments is described. In Chapter 4, a novel, non-steady state quantitative MRI method is described.

Connexins are a family of gene products sharing a similar topology that mediate transmembrane and intercellular diffusion of ions and small molecules through hemichannels (HCs) and gap junction channels (GJCs), respectively, and participate in intracellular signaling through protein-protein interaction. Connexin 37 (Cx37) and Cx40 are co-expressed by endothelial cells, suggesting a unique role for each connexin in regulating cellular function. Through gene knockout studies in mice, Cx37 was found to regulate vascular cell proliferation while Cx40 regulates conduction of upstream vasomotor signals and leukocyte infiltration. The unique functions of Cx37 and Cx40 result in contrasting effects of ischemic injury in mice lacking expression of either Cx37 or Cx40 genes. Cx37 knockout mice (Cx37-/-) have significantly improved recovery due to an increase in both vasculogenesis and angiogenic processes. In the current studies, the mechanism by which Cx37 mediates cellular proliferation is explored by examining the role of functional GJCs and HCs. Channel function is necessary, but HC function is not sufficient for Cx37-mediated suppression of proliferation. These results suggest that Cx37 requires a competent GJC that supports a specific conformation of the carboxyl terminus that is able to interact with necessary growth regulatory protein(s). Conversely, Cx40-/- mice have reduced angiogenic and arteriogenic processes and impaired post-ischemic recovery. In the current study, we explored the inflammatory response following the femoral artery ligation (FAL) surgery, in wildtype (WT) and Cx40-/- mice. Cx40-/- mice had an excessive infiltration of activated neutrophils to the ischemic gastrocnemius muscle and a prolonged presence of activated macrophages. We depleted mice of circulating neutrophils during the induction of ischemia to evaluate if the excessive infiltration of neutrophils impaired recovery and found no improvement in post-ischemic recovery in either WT or Cx40-/- mice. These data indicate that, although Cx40-/- mice have a pro-inflammatory state that results in an excessive and prolonged presence of leukocytes post-ischemia, reduction of acute leukocyte infiltration does not improve post-ischemic recovery. Additional information is necessary to determine the mechanisms by which Cx37 and Cx40, individually or in concert with each other, regulate endothelial cell function and arterial vascular response to ischemic injury.