Doctor of Philosophy (PhD), Wright State University, 2021, Biomedical Sciences PhD

The carotid bodies (CB) are peripheral chemoreceptors that detect changes in arterial oxygenation and, via afferent inputs to the brainstem, correct the pattern of breathing to restore blood gas homeostasis. Elucidating the “signal” that couples carotid body sensory type I cell (CBSC) hypoxic mitochondrial inhibition with potassium channel closure has proven to be an arduous task; to date, a multitude of oxygen-sensing chemotransduction mechanisms have been described and altercated (Varas, Wyatt & Buckler, 2007; Gao et al, 2017; Rakoczy & Wyatt, 2018). Herein, we provide preliminary evidence supporting a novel oxygen-sensing hypothesis suggesting CBSC hypoxic chemotransductive signaling may in part be mediated by mitochondria-generated thermal transients in TASK-channel-containing microdomains. Confocal microscopy measured distances between antibody-labeled mitochondria and TASK-potassium channels in primary rat CBSCs. Sub-micron distance measurements (TASK-1: 0.33 ± 0.04µm, n = 47 vs. TASK-3: 0.32 ± 0.03µm, n = 54) provided the first direct evidence for CBSC oxygen-sensing microdomains. Using a temperature-sensitive dye (ERthermAC), hypoxic-inhibition of mitochondrial oxidative phosphorylation in CBSCs was suggested to cause a rapid and reversible inhibition of mitochondrial thermogenesis and thus temperature in these microdomains. Whole-cell perforated-patch current-clamp electrophysiological recordings demonstrated CBSC sensitivity of resting-Vm to temperature: lowering bath temperature from 37°C to 24°C induced consistent and reversible depolarizations (Vm at 37°C: -48.4 ± 4.11mV vs. Vm 24°C: -31.0 ± 5.69mV; n = 5; p<0.01) in isolated, primary rat CBSCs. We propose that hypoxic inhibition of mitochondrial thermogenesis may play a critical role in hypoxic chemotransduction in the carotid body. A reduction in temperature within cellular microdomains will inhibit plasma membrane ion channels, influence the balance of cellular phosphorylation–dephosphorylation, and (open full item for complete abstract)

Committee: Christopher N. Wyatt Ph.D. (Advisor); Eric S. Bennett Ph.D. (Committee Member); Paula A. Bubulya Ph.D. (Committee Member); Kathy Engisch Ph.D. (Committee Member); Robert M. Lober M.D., Ph.D. (Committee Member) Subjects: Biomedical Research; Cellular Biology; Neurobiology; Neurosciences; Physiology

Master of Science, The Ohio State University, 2013, Environment and Natural Resources

Hypoxia is a common phenomenon in aquatic environments which most frequently occurring during late summer or late winter. Hypoxic events are increasing in intensity as water temperatures increase, and it is important to understand how hypoxia affects aquatic ecosystems, particularly fish. Additionally, increases in ammonia concentrations have been shown to occur during periods of hypoxia. Ammonia is converted to nitrate in aquatic environments through nitrification, via the nitrogen cycle. However, this process is carried out by aerobic bacteria and is depressed by hypoxia. Ammonia has been shown to be more toxic to fish during hypoxia than during normoxia, indicating that it could have large implications on fish foraging activity in hypoxic waters. While fish have reduced growth in hypoxic water, the simultaneous accumulation of ammonia may result in death. Therefore, evaluation of how hypoxia affects fish simultaneously exposed to ammonia is essential to understand how fish are affected during natural hypoxic events, such as those that occur in the hypolimnion of Lake Erie. Juvenile yellow perch were reared under varied oxygen conditions to examine how hypoxia affects growth and survival of fish. Yellow perch are a physoclistous fish which can result in irreversible failure to inflate the swim bladder. Therefore, fish with both inflated and uninflated swim bladders were tested at different concentrations of oxygen for survival, growth, and oxygen consumption to gain a better understanding of how hypoxia affects yellow perch. Fish were stocked into 12 tanks with three levels of oxygen: 3, 4, and >7 mg O2/L (33, 45, & >78% saturation at 21 degrees Celsius). Fish were fed ad libitum with live brine shrimp nauplii over a 14-day period. Oxygen consumption was measured at the end of the experimental trial. Survival was not affected by lowered dissolved oxygen, but growth was reduced significantly in fish with both inflated (at 32% oxygen saturation) and uninflated swim (open full item for complete abstract)

Committee: Konrad Dabrowski (Advisor); Robert Gates (Committee Member); Roman Lanno (Committee Member) Subjects: Natural Resource Management

Master of Sciences, Case Western Reserve University, 2023, Clinical Research

While sleep disorders are implicated in atrial fibrillation (AF), interplay of physiologic alterations and symptoms remains unclear. Sleep-based subtypes can account for this complexity. We hypothesized discrete phenotypes of symptoms and polysomnography-based data on adult patients in the STARLIT Registry (n=43,433) differ in relation to incident AF (8.9%, n=3,596). Clusters, identified using latent class analysis, were used as predictors in multivariable-adjusted Cox proportional hazards models. Five clusters were identified: ‘Hypoxic + Sleepy' had 48% increased risk, ‘Apneas + Arousals' 22% increased risk, and ‘Short Sleep + Low %REM' 11% increased risk of incident AF compared to ‘Long Sleep + High %REM', and ‘Hypopneas' did not differ over a 7.6±3.4 year follow-up period. Consistent with prior evidence of hypoxia as an AF driver and cardiac risk of the sleepy phenotype, this constellation of symptoms and physiologic alterations illustrates risk in the clinical setting, providing potential value as a risk prediction tool.

Committee: Reena Mehra (Committee Chair); Anna May (Committee Member); Brittany Lapin (Committee Member); Michael Faulx (Committee Member) Subjects: Anatomy and Physiology; Biology; Biomedical Research; Biostatistics; Health; Health Care; Health Sciences; Medicine; Neurobiology; Neurology; Neurosciences; Statistics

Doctor of Philosophy (PhD), Wright State University, 2022, Biomedical Sciences PhD

Diffuse midline glioma, K27M-mutant (DMG) are intractable brain tumors, primarily occurring in the pediatric and adolescent population. Patients have a median survival of less than one year after diagnosis. A lack of therapeutic targets has been a barrier to improvement in patient survival. Irradiation therapy improves symptoms while chemotherapy and surgical intervention, for the most part, have not yet demonstrated utility for treatment. DMG are characterized by a histone H3 mutation that results in the genome-wide loss of epigenetic-repressive marks on K27 and is associated with the misexpression of genes, like Cancer/Testis antigens. A member of this group, transketolase-like 1 (TKTL1), is an enzyme that catalyzes reactions bridging glycolysis and the pentose phosphate pathway. This work demonstrates that DMG express TKTL1, which reprograms cellular metabolism in support of tumor cell growth and regulates the expression of hypoxia-inducible factor 1 alpha (HIF-1α). HIF-1α in tumor cells is associated with increased invasion, metastasis, increased survival, and resistance to therapy. Inhibition of HIF-1α in DMG cells decreased hypoxia-induced gene expression, glycolytic capacity, mitochondrial respiration, and tumor cell proliferation. TKTL1 knockdown similarly reduced tumor cell proliferation and the population of mitotic cells and decreased glycolytic rate. Loss of TKTL1 did not increase sensitivity to the chemotherapeutic agents, panobinostat or carboplatin, but rather slowed DMG cell growth independently of their cytotoxic effects. These data indicate TKTL1 expression in DMG alters metabolism and proliferation and is a potential therapeutic target.

Committee: Robert M. Lober M.D., Ph.D. (Committee Chair); Thomas L. Brown Ph.D. (Committee Co-Chair); Weiwen Long Ph.D. (Committee Member); David R. Ladle Ph.D. (Committee Member); Lynn K. Hartzler Ph.D. (Committee Member) Subjects: Biomedical Research; Cellular Biology; Oncology

Master of Science (MS), Wright State University, 2021, Pharmacology and Toxicology

Endothelial progenitor cells (EPCs) have been shown to provide beneficial effects on oxidative stress. Exosomes (EXs) released from these stem cells could be one of the major contributors, as they are known to convey the benefit of one cell to another cell via microRNAs (miRNA). At first, we determined that EPCs release more EXs when they are serum-starved for 48 hours., and by determining the microRNA-210 (miR-210) levels in the EXs, we found that miRNA is being transferred from cells to EXs. Meanwhile, miR-210 is gaining popularity in reducing elevated oxidative stress levels. In this study, we investigated the role of endothelial progenitor cells-EXs (EPC-EXs) and the beneficial effects of loading miR-210 into EPC-EXs (miR-210-EPC-EXs) on hypoxia and reoxygenation (H/R) induced reactive oxygen species (ROS) overproduction, apoptosis, and reduced viability of neuronal cells. It was found that EXs were uptaken by neurons and elevated the miR-210 levels in the neurons. In comparison with the vehicle, the EPC-EXs and EXs from scramble transfected EPCs (Scramble-EPC-EXs), were efficient in attenuating neuronal apoptosis, elevated oxidative stress, and restoring cell viability. Whereas the miR-210-EPC-EXs were more efficient in attenuating these inimical effects induced by H/R injury in neurons

Committee: Ji Chen Bihl M.D., Ph.D. (Advisor); Yanfang Chen M.D., Ph.D. (Committee Member); Ravi Sahu Ph.D. (Committee Member) Subjects: Biomedical Research; Medicine; Pharmaceuticals; Pharmacology; Science Education; Toxicology

Doctor of Philosophy, Case Western Reserve University, 2019, Molecular Medicine

The beta-adrenergic receptor (bAR) exists in an equilibrium of inactive and active conformational states, which is modulated by ligands resulting in downstream signaling. In addition to cAMP, bAR regulates hypoxia-inducible factor 1 (HIF-1). We hypothesized that HIF-1 signaling occurs via a unique, independent bAR conformation and that Pulmonary Arterial Hypertension (PAH) patients with HIF-biased conformations would have blunted cAMP response. We found isoproterenol and salbutamol, both cAMP agonists, had opposing effects on HIF-1 in cells and mice. Additionally, hypoxia blunted agonist-stimulated cAMP in vitro, consistent with receptor equilibrium shifting towards HIF-activating conformations. bAR overexpression in cells increased HIF-1 activity and glycolysis which was blunted by HIF-1 inhibitors, suggesting increased bAR increases basal HIF-1 signaling. Because PAH is also characterized by HIF-related glycolytic shift, we dichotomized PAH patients in the PAHTCH trial (NCT01586156) based on right ventricular glucose uptake to evaluate bAR signaling. Patients with high glucose uptake had more severe disease than those with low uptake and had no response to bAR ligands. The findings expand the paradigm of bAR regulation and uncover a novel PAH subtype that might benefit from b-blockers. Circulating cell-free mitochondrial components are well characterized as mediators of inflammation. Recent studies show cells also release microparticles (MPs) containing intact mitochondria under conditions of stress or injury. However, detection of cell-free mitochondria and their cellular origin has not been studied in non-pathological conditions. Thus, we hypothesize that intact mitochondria are detectable in the circulation under physiological conditions. To test this, plasma MPs were analyzed via flow cytometry. Murine platelet-depleted plasma showed a small cluster of MPs which was 65% positive for the mitochondrial marker MitoTracker Green (MT Green). Additionally, transg (open full item for complete abstract)

Committee: Serpil Erzurum MD (Advisor); Sathyamangla Prasad PhD (Committee Chair); Kristin Highland MD (Committee Member); Bela Anand-Apte MBBS, PhD (Committee Member); Satish Kalhan MD (Committee Member) Subjects: Biology; Biomedical Research; Molecular Biology; Physiology

Doctor of Philosophy, University of Toledo, 2014, College of Natural Sciences and Mathematics

Yellow Perch within Lake Erie's Central Basin must contend with the development of hypolimnetic hypoxia, which generally occurs August - October and reaches thicknesses of up to 8 meters off the lake bottom. Since Yellow Perch are primarily demersal benthivores, large portions of their primary habitat becomes unsuitable during hypoxic events. Field studies have shown that while Yellow Perch largely avoid hypoxia, they continue to forage for benthic prey despite hypoxic conditions. Little is known about the fine-scale behavioral changes of Yellow Perch during hypoxia, or the physiological consequences of hypoxic foraging. In controlled laboratory experiments, I analyzed the behavioral changes of Yellow Perch under simulated hypolimnetic hypoxia, and determined the physiological response of Yellow Perch to hypoxic exposure by measuring the response of a hypoxia-responsive protein, Hypoxic Inducible Factor-1-alpha (HIF-1a). Yellow Perch were subjected to normoxic (~8 mg DO/L), moderate hypoxic (~4 mg DO/L) or severe hypoxic (~2 mg DO/L) dissolved oxygen concentrations for durations of up to 8 hours, followed by a 40-hour normoxic recovery period. Baseline HIF-1a levels were detected in Yellow Perch liver tissues under normoxic conditions, and increased significantly after two hours of hypoxic exposure. HIF-1a peaked at 2 and 4 hours of hypoxic exposure under severe and moderate hypoxic conditions, respectively, but returned to levels similar to normoxic treatments by 8 hours of exposure. These results suggest Yellow Perch are well adapted to hypoxic conditions and that a direct negative feedback mechanism may aide survival under prolonged hypoxia. In order to observe the behavioral changes of Yellow Perch in stratified hypoxic conditions, I designed and constructed two experimental tank systems that simulated hypoxic conditions characteristic of temperate freshwater lakes. Using these systems, two behavioral experiments were conducted examining changes in be (open full item for complete abstract)

Committee: Thomas Bridgeman Ph.D. (Advisor); Christine Mayer Ph.D. (Committee Member); W. Von Sigler Ph.D. (Committee Member); Randall Ruch Ph.D. (Committee Member); Jessica Head Ph.D. (Committee Member) Subjects: Aquatic Sciences; Behavioral Sciences; Biology; Experiments; Freshwater Ecology; Limnology; Molecular Biology; Physiology

Master of Science (MS), Wright State University, 2013, Microbiology and Immunology

Hypoxia-inducible factor-1 alpha (HIF-1a) is a critical component of the cellular oxygen-sensing machinery and is essential for placental formation and embryonic survival. In this study, we promoted prolonged expression of HIF-1a, by using a form that is insensitive to oxygen, denoted as CA-HIF-1a. In order to have continual placental specific expression of the CA-HIF-1a, lentiviral infection was performed on embryos at the blastocyst stage of development and transferred into pseudo-pregnant mothers. Placental analysis was performed via in situ hybridization on embryonic day 14.5 (E14.5) to determine the effects of CA-HIF-1a prolonged expression. Data indicate that prolonged activity of CA-HIF-1a restricted to trophoblast cells in the mouse placenta results in the inability of cells to advance from their progenitor states, failure of the placenta to organize properly, and failure of trophoblasts to remodel the maternal arteries. Since HIF-1a has the ability to cause developmental placental disruption, its regulation in the placenta could be key in multiple pregnancy-associated disorders such as pre-eclampsia and intrauterine growth restriction (IUGR).

Committee: Thomas Brown Ph.D. (Advisor); Christopher Wyatt Ph.D. (Committee Member); Courtney Sulentic Ph.D. (Committee Member) Subjects: Biology; Developmental Biology

Doctor of Philosophy (PhD), Wright State University, 2009, Biomedical Sciences PhD

Early embryonic development occurs under low oxygen levels. The placenta is an organ transiently formed during pregnancy and plays a crucial role during development of the embryo. Alterations in the placental structure or function have been associated with the pathologies such as preeclampsia in humans. In mammals, the hypoxia inducible factor (HIF) transcription factors have been identified as the major regulators of cellular responses in low oxygen. In the current study, we investigated the effects of low oxygen on the differentiation of trophoblast stem cells, lineage committed trophoblast giant cells and labyrinthine lineage-committed cells. We examined the effects of an oxygen-insensitive form of HIF-1 alpha on the differentiation of lineage-committed trophoblast giant cells. Using a novel lentivirus–mediated, placental-specific gene expression strategy, we investigated the effect of prolonged HIF-1 alpha on placental and embryonic development in vivo. Our studies suggest that low oxygen inhibits differentiation of trophoblast cells and affects several placental lineages. The expression of the oxygen-insensitive form of HIF-1 alpha inhibited the molecular, morphological and functional differentiation of trophoblast giant cells. Placental specific expression of the oxygen-insensitive form of HIF-1 alpha, also led to significant alterations in placental morphology that mimic the pathology of two pregnancy-related conditions in humans, preeclampsia and intrauterine growth restriction (IUGR). Our studies show that HIF-1 alpha is a master regulator of trophoblast differentiation and placental development.

Committee: Thomas Brown PhD (Advisor); Paula Bubulya PhD (Committee Member); Michael Leffak PhD (Committee Member); Robert Putnam PhD (Committee Member); Christopher Wyatt PhD (Committee Member) Subjects: Cellular Biology; Molecular Biology

Doctor of Philosophy, The Ohio State University, 2007, Educational Policy and Leadership

Increased participation of competitive athletes in new methods of simulated altitude warrants research on changes in performances. PURPOSE: To ascertain the effects of intermittent simulated altitude exposure via re-breathing on cycling performance. METHODS: Eighteen, well-trained male cyclists use a re-breathing device for 15 days. Subjects were randomly assigned to either a low constant exposure group (CON) in which oxygen saturation was held constant (98%); or progressively increased exposure group (TRT), where oxygen saturation was progressively reduced (90% to 77% over 15 days). An exercise performance test was performed to familiarize subjects to the protocol (FAM), prior to simulated altitude exposure (PRE) and following simulated altitude exposure (POST). The critical power protocol was used to examine power output in varied time trial (TT) efforts. Performance was also investigated through measurements of lactate, oxygen consumption (VO2), and heart rate (HR). Blood characteristics examined include hematocrit, reticulocyte and serum Ferritin values. RESULTS: There was significant improvement (p=.004) for the TRT group at POST in the 15m TT (PRE = 325.0 ± 12.2 watts, POST = 335.0 ± 11.9 watts) and estimated 60m TT (PRE = 300.1 ± 28.4; POST = 322.4 ± 36.1) compared to no improvement in the CON group. The TRT group improvement was 3-4.5% in average power output. There were no significant differences in the power outputs of the 3m TT at POST for either group. There were no significant differences in haematological measures at POST for either group. A decreased VO2 Index (p=.075) and a significant decrease (p = .026) in HR Index (HRavg/wattavg) was revealed for the TRT group (PRE = 0.564 ± 0.044; POST = 0.544 ± 0.053). CONCLUSIONS: In competitive cyclists, the use of a re-breathing device resulted in improved performance for events which rely heavily on aerobic power but none for anaerobic power. These findings are similar in regard to performance adaptations fo (open full item for complete abstract)

Committee: Timothy Kirby (Advisor) Subjects: Health Sciences, Recreation

Master of Science in Environmental Science, Cleveland State University, 2024, College of Arts and Sciences

Despite the critical role of organic matter (OM) oxidation in depleting oxygen in the hypolimnetic waters of Lake Erie, uncertainties regarding the sources, quantity, and fate of OM continue to challenge our understanding and management of hypoxia in the lake. This study evaluates the effects of OM oxidation through the analysis of stable carbon isotopes (δ13C) of dissolved inorganic carbon (DIC) and dissolved organic carbon (DOC) in the central and eastern basins of Lake Erie. We disclose DIC contributions from OM oxidation and provide insight into the origins of OM in the hypolimnion. Our results reveal significant declines in δ13CDIC in hypolimnetic waters compared to surface waters, indicative of OM oxidation in the deepest portions of the lake. To further examine this process, we employed the Keeling plot method to estimate the composite isotopic signature of OM respiration (δ13CR). The good agreement between the respired source (-24.4‰) and the signature of the organic material (-24.6‰) support the idea that autochthonous material (internally produced OM) fuels OM oxidation in the central and eastern basins. Additionally, a binary mixing model was utilized to quantify the amount of DIC produced and the respective amount of oxygen required by OM oxidation. We estimate that 11.8 ± 1.6 % of DIC was produced in the central basin and 5.6 ± 1.2% in the eastern basin, which accounts, on average, for 89.3 ± 7.1 % of hypolimnetic oxygen depletion in the central basin and 99.2 ± 17.7 % in the eastern basin. This suggests OM oxidation accounts for most of the hypolimnetic oxygen depletion in the lake, however instances of hypoxia in the central basin may promote other mechanisms of oxygen depletion such as oxidation of CH4, Fe2+, and Mn2+. This study reveals a strong coupling between carbon cycling and oxygen depletion in Lake Erie. Our results underscore the applicability of δ13CDIC as a meaningful tracer to quantify the amount of oxygen-consuming OM in hypolimn (open full item for complete abstract)

Committee: Fasong Yuan (Advisor); Brice Grunert (Committee Member); Julie Wolin (Committee Member) Subjects: Biogeochemistry; Environmental Science; Limnology

PhD, University of Cincinnati, 2024, Arts and Sciences: Biological Sciences

Oxygen is a basic necessity of life for nearly all species. However, owing to environmental or medical conditions, the required concentration of oxygen to maintain metabolic demand may not be available. Interestingly, while some species struggle with even modest changes to oxygen concentration, others can withstand large fluctuations including periods of extremely low oxygen (hypoxia). Fishes inhabit nearly all aquatic environments, inclusive of well- and poorly- oxygenated conditions, making them especially suitable to study the effects of hypoxia. However, the evolutionary mechanisms that enabled these traits to arise are relatively unknown. The blind Mexican cavefish, Astyanax mexicanus, presents a unique model to study both adaptations to hypoxia as well as the underlying evolutionary mechanisms. This species is comprised of two morphotypes, an ‘ancestral-surrogate' surface morphotype that resides in well-oxygenated lakes, rivers, and streams of northeastern Mexico and the southwest United States, and an obligate cave-dwelling morphotype found in numerous distinct caves throughout the limestone karst of northeastern Mexico that are likely hypoxic. This drastic environmental shift prompted the necessity to adapt to the harsh conditions within caves. While many cavefish traits have been characterized, adaptations to hypoxia have received very little attention. In this dissertation, I aimed to begin to characterize traits in cavefish that may confer adaptive advantages to living in hypoxic conditions. First, we discuss empirical measurements of dissolved oxygen as well as the environmental features that likely contribute to the hypoxic condition of caves. We then investigated morphological changes to red blood cells that enable a higher concentration of hemoglobin protein in circulation. Subsequently, we set out to determine how individual hemoglobin orthologs are regulated to contribute to the aggregate increase of hemoglobin protein. Additionally, we revealed une (open full item for complete abstract)

Committee: Joshua Gross Ph.D. (Committee Chair); Stephanie Rollmann Ph.D. (Committee Member); Brian Carlson Ph.D. (Committee Member); Michael Booth Ph.D. (Committee Member); Daniel Buchholz Ph.D. (Committee Member) Subjects: Biology

Master of Science, The Ohio State University, 2023, Evolution, Ecology and Organismal Biology

Hypoxia, or low concentration of dissolved oxygen in the water, is becoming a more frequent and extensive phenomenon in many aquatic ecosystems around the world, impacting the ecology of lakes, estuaries, and marine fishes. This often-recurring state of low oxygen degrades habitat quality, affects fish physiology, and can lead to changes in the behavior and distribution of species. Hypoxia can alter predator-prey dynamics through species-specific responses to low oxygen and changes spatiotemporal distributions of populations. The central basin of Lake Erie experiences seasonal hypolimnetic hypoxia every year due to a combination of natural thermal stratification and human practices. Lake Erie supports ecologically important and lucrative recreational and commercial fisheries, so considerable research has gone into understanding the impacts of hypoxia on the Lake Erie ecosystem. In the last decade, adult yellow perch (Perca flavescens) catch in the central basin of Lake Erie has significantly declined, raising questions about the drivers of decreases in yellow perch catch. The goal of this research was to gain better understanding about how hypoxia and other environmental variables associated with the hypoxic season (i.e. higher temperatures) influence adult (2+) yellow perch distributions and overall abundance as well as their diets and foraging behavior. Towards this goal, we conducted hydroacoustic surveys, analyzed data from 2021 annual Ohio Department of Natural Resources – Division of Wildlife trawl surveys, collected data on environmental variables, quantified adult yellow perch stomach contents, and collected data on zooplankton and benthic macroinvertebrates. In the first chapter, we used paired bottom trawl-hydroacoustic surveys to investigate the effects of hypoxia on adult yellow perch distributions. We compared where yellow perch were located in the water column (both fish and site depth) and yellow perch densities between sampling months. The second cha (open full item for complete abstract)

Committee: Elizabeth Marschall (Advisor); Stuart Ludsin (Committee Member); Roman Lanno (Committee Member) Subjects: Biology; Ecology; Environmental Science; Freshwater Ecology

Doctor of Philosophy (PhD), Ohio University, 2023, Chemistry and Biochemistry (Arts and Sciences)

Stroke and heart attack are among the leading causes of death in the United States and worldwide. The high mortality rate is alarming given the wide availability of therapies for these illnesses. The mechanisms of action of these two diseases are remarkably similar, despite the fact that they are linked to two quite distinct organs in our body; in both, there is significant oxygen deprivation at the cellular level. Nitorooxidative stress occurs in physiological system due to the imbalance between Nitric Oxide (NO) and peroxynitrite (ONOO-). Using electrochemical nanosensors1,2 and a hypoxic chamber (which can control O2 from 21% to 0%), nitrooxidative stress in the endothelial and neural systems was studied, as well as two potential treatments (L-arginine and vitamin D3). Additionally, a connection was made between the protein HIF-1α and nitrooxidative stress. According to experimental data, L-arginine and vitamin D3 treatments can restore the [NO]/[ONOO-] balance in the endothelial system by up to 73 % and 69%, respectively. L-arginine and vitamin D can help the neural system's balance by up to 61% and 8%, respectively. Both L-arginine and vitamin D3 were also found to be effective in downregulation of HIF-1α in severe hypoxic conditions.

Committee: Tadeusz Malinski (Advisor); Michael Held (Committee Member); Katherine Cimatu (Committee Chair); Krisanna Machtmes (Committee Member); Howard Dewald (Committee Member) Subjects: Biochemistry; Chemistry

Doctor of Philosophy, The Ohio State University, 2022, Chemical Engineering

Despite the underlying role of hypoxia and oxidative stress in vascular and inflammatory diseases, little is understood about its role in early disease progression and no therapeutics exist to combat it. Hypoxia is suspected to disrupt the function of the endothelium, the inner lining of cells in all vessels which is responsible for regulating exchange between nutrients and waste metabolites in the blood stream and tissues. Due to the vital and far-reaching functions of the endothelium in modulating vascular tone, inflammatory pathways, and the formation of new vessels, endothelial dysfunction often precedes and can be propagated in vascular disease. Consequently, studying the relationship between hypoxia and endothelial dysfunction is an area of great interest in identifying potential therapeutic targets for early intervention. A pathophysiology of particular interest in this work is preeclampsia (PE), a pregnancy disorder which is poorly understood. In PE, early vascular dysregulation leads to later appearance of clinical symptoms. Hypoxia is intimately involved in the progression of PE and its potentially devastating effects on fetal development. No therapeutic interventions currently exist for PE. As such, PE is an excellent environment in which to investigate whether oxygen (O2) modulation can rescue vascular dysregulation. One promising candidate for therapeutically alleviating hypoxia associated with the vascular disease state is hemoglobin-based O2 carriers (HBOCs). However, commercially available HBOCs contain low molecular weight (LMW) species which induce cytotoxicity due to extravasation. This work focused on synthesizing and characterizing high molecular weight (HMW) polymerized human hemoglobins (hHb)(PolyhHbs) in order to achieve a therapeutic O2 carrier with an improved safety profile. To this end, a tunable platform replicating human microvasculature was developed and used to evaluate HMW PolyhHb's potential for extravasation and endothelial (open full item for complete abstract)

Committee: Andre Palmer (Advisor); Eduardo Reategui (Committee Member); Jeffrey Chalmers (Committee Member); Jonathan Song (Advisor) Subjects: Chemical Engineering

Master of Science (M.S.), University of Dayton, 2022, Mechanical Engineering

An understanding of how pilots complete their flight tasks is an essential element of preventing aviation incidents. Disorientation or a loss of control of the aircraft are some direct causes of such events. This study seeks to assess the impact of environmental factors on the ability of general aviation pilots to complete flight tasks. Certified Pilots (n=16) with experience flying a Cessna 172 or similar aircraft participated. They were tasked with flying a virtual model of a Cessna 172 Skyhawk. This was accomplished using X-Plane 11 flight simulation software, Honeycomb Alpha flight controls, and a Saitek throttle quadrant. The software was integrated with an HTC Vive Pro virtual reality headset. Within X-Plane 11, three environmental conditions were created: Clear, Partial Clouds (Partial Cover), and Full Clouds (Total Cover). All weather conditions other than cloud cover were the same across the environments with no wind present. No clouds are present in the Clear environment. Roughly 50% of the ground is obscured by clouds in the Partial Clouds environment. The ground is completely obscured by clouds in the Full Clouds environment. While in an environment, pilots were tasked with performing a series of 500 ft ascents, 500 ft descents, 90° turns to the right, and 90° turns to the left. These tasks were completed above the cloud layers of the environments. During Day A, the pilots flew in each of the environments twice. During Day B, pilots flew in the Full Clouds environment twice and were exposed to hypoxic air during one of those times. The hypoxic air is 10% oxygen and simulates an altitude of approximately 14,000 ft. The pilots were assessed based on their altitude error, heading error, heading rate of change, task duration, and the amount of motor control effort that was required to complete the task. When flying in environmental conditions that have fewer visual cues such as the Total Cover condition, pilots experienced more error a (open full item for complete abstract)

Committee: Megan Reissman (Advisor); Anne Crecelius (Committee Member); Timothy Reissman (Committee Member) Subjects: Aerospace Engineering; Biomechanics; Engineering; Mechanical Engineering

Doctor of Philosophy, The Ohio State University, 2021, Molecular Genetics

Fungal biofilm founder cells experience self-generated hypoxia leading to dramatic changes in their cell biology. For example, during Aspergillus nidulans biofilm formation microtubule (MT) disassembly is triggered causing dispersal of EB1(a MT ‘+' end binding protein) from MT tips. This process is dependent on SrbA, a sterol regulatory element binding transcription factor required for adaptation to hypoxia. We find that SrbA, an ER resident protein prior to activation, is proteolytically activated during early stages of biofilm formation and that its activating proteases are required for normal biofilm cell regulation. In addition to SrbA, the AtrR transcription factor is also found to be required to modulate cellular responses to gaseous signaling during biofilm development. Using co-cultures, we show that cells lacking srbA or atrR are capable of responding to biofilm generated hypoxia and are actually more sensitive to this signal than wild type cells. SrbA is a regulator of ergosterol biosynthetic genes and we find that the levels of seven GFP-tagged Erg proteins differentially accumulate during biofilm formation. This uncovers a complex pattern of regulation with biofilm accumulation of only some Erg proteins being dependent on SrbA with others accumulating to higher levels in its absence. Because different membrane sterols are known to influence cell permeability to gaseous molecules, including oxygen, we propose that differential regulation of ergosterol biosynthetic proteins by SrbA may calibrate the cell's responsiveness to gaseous signaling which in turn modifies the cell biology of developing biofilm cells.

Committee: Stephen Osmani (Advisor); Amanda Bird (Committee Member); Jian-Qiu Wu (Committee Member); Anita Hopper (Committee Member); Anna Dobritsa (Committee Member) Subjects: Genetics; Microbiology; Molecular Biology

Doctor of Philosophy, Case Western Reserve University, 2021, Physiology and Biophysics

In mammals, the carotid body (CB) chemosensitive glomus (type I) cells are the primary sensors of oxygen (O2) and secondary sensors of carbon dioxide (CO2) in the blood. Glomus cells also receive projections from sympathetic postganglionic fibers, whose cell bodies reside in the superior cervical ganglion (SCG) and receive sympathetic preganglionic input from fibers in the cervical sympathetic chain (CSC). Hypoxia (HX, low blood O2) and/or hypercapnia (HC, high blood CO2), activate CB glomus cells, which signals the brainstem respiratory pattern generator via chemoafferent fibers of the carotid sinus nerve (CSN). Hypoxia also activates small intensely fluorescent (SIF) cells in the SCG, which projects to the brainstem. In addition to CB chemoreceptors, mammals possess central chemoreceptors, including the retrotrapezoid nucleus (RTN), which are stimulated by increases in protons (H+) - via carbonic anhydrous catalyzed reaction of CO2 and water. Our data shows that: (1) HX (10% O2, 90% N2), HC (5% CO2, 21% O2, 74% N2) or the physiologically-relevant hypoxic-hypercapnic (HH) (5% CO2, 10% O2, 85% N2) gas challenges elicited robust ventilatory responses in juvenile postnatal (P) 25 Sprague Dawley SHAM rats, (2) ventilatory responses elicited by HX alone and HC alone were generally additive in SHAM rats, (3) ventilatory responses to HX, HC and HH were markedly attenuated in bilateral CSN transected (CSNX) rats compared to SHAM, and (4) ventilatory responses elicited by HX alone and HC alone were generally not additive in CSNX rats. Additionally, our data shows that adult male C57BL6 mice with bilateral CSC transection (CSCX) display numerous altered responses to a HX (10% O2, 90% N2) challenge that also occurred in male C57BL6 mice with SCG removal (SCGX), however SCGX mice also displayed changes during HX challenge that CSCX mice did not, including diminished total increases in minute ventilation. Therefore, our data proposes that CB chemoafferent input is essential fo (open full item for complete abstract)

Committee: Stephen J Lewis (Advisor); William Schilling (Committee Chair); Sudha Chakrapani (Committee Member); Derek Damron (Committee Member); Thomas Dick (Committee Member); David Friel (Committee Member) Subjects: Physiology

Doctor of Philosophy, Case Western Reserve University, 2021, Genetics

Interrogating how somatic stem cells interpret and transmit the intricate web of extracellular and intracellular signals that regulate cell state is foundational to biology and informs regenerative medicine approaches for treating disease. Oligodendrocyte progenitor cells (OPCs) are stem cells in the developing and adult brain that form oligodendrocytes, which are responsible for myelinating and supporting neuronal axons. Here, we elucidate transcriptional regulators of the oligodendrocyte lineage in both physiologic and pathologic contexts to identify strategies for promoting myelin regeneration in disease. Oligodendrocyte formation follows a multi-step process of OPC differentiation into immature oligodendrocytes, followed by subsequent maturation to myelinating oligodendrocytes. The transcriptional regulators of oligodendrocyte maturation remain unknown. Here, we discovered that the transcription factor Sox6 forms developmental condensates across gene bodies in immature oligodendrocytes to stabilize this intermediate state. Loss of Sox6 prevented condensate gene activation and accelerated maturation of OPCs directly to myelinating oligodendrocytes. This work offers a novel approach to regenerate myelinating oligodendrocytes in disease. This multi-step differentiation process is impaired by low oxygen (hypoxia) as seen in stroke, premature birth, and respiratory distress syndromes. Foundational to the hypoxic response is the accumulation of evolutionarily conserved transcription factors called hypoxia-inducible factors (HIFs). While HIFs are transiently protective, chronic HIF accumulation drives distinct pathological responses in numerous tissues and exerts a powerful influence over cell fate decisions in a multitude of stem cell types, including impairing oligodendrocyte formation from OPCs. In this study, we demonstrate that non-canonical, cell-type-specific targets of HIF1a are sufficient to impair the expression of Sox10, which is required for oligode (open full item for complete abstract)

Committee: Paul Tesar PhD (Advisor); Drew Adams PhD (Committee Chair); Tara DeSilva PhD (Committee Member); Anthony Wynshaw-Boris MD/PhD (Committee Member) Subjects: Genetics; Neurosciences

Master of Science, University of Toledo, 2021, Biology (Ecology)

Chapter 2: Stratification and hypoxia in the western basin of Lake Erie (WBLE) has been shown to result in phosphorus flux from the underlying sediment, which could provide necessary nutrients for harmful algal bloom (HAB) growth. Studying the duration and frequency of hypoxic events would provide pivotal information for estimations of phosphorus flux from underlying sediments. However, due to the ephemeral nature of hypoxic events in the WBLE, planned weekly vessel-based sampling trips are inadequate for alerting researchers of the onset of hypoxia, making sampling such events difficult. Instead, water quality instruments can be deployed to collect and relay live data to researchers in a much more frequent timeline. In this study, a buoy equipped with a thermistor string and an EXO3 sonde (Yellow Springs Institute) was deployed to monitor for potential stratification and depleting lake bottom oxygen concentrations. This system measured water quality parameters and posted the data online every 20 minutes. Using these data, immediate vessel-based sampling trips to 7 sites were made according to observed hypoxia. Data captured show a hypoxic event occurred in the WBLE during early July 2020 that persisted for several days before being mixed by a storm on July 11, 2020. This hypoxic event coincided with 8 days of stratification. In addition, hypolimnion water warmed to over 23 ℃ while remaining stratified from the overlying waters, which could facilitate higher phosphorus flux from sediments. On average, phosphorus concentrations in the hypolimnion were 1.06 µ/L (~43%) higher than in the epilimnion by the end of the event, suggesting that sediments were releasing phosphorus into the overlying waters. Chapter 3: The western basin of Lake Erie (WBLE) has been experiencing Harmful Algal Blooms (HABs) for over a decade. These blooms have been detrimental to the health of Lake Erie and the safety of drinking water for surrounding communities. Nutrient inputs (namel (open full item for complete abstract)

Committee: Thomas Bridgeman Dr. (Committee Chair); Michael Weintraub Dr. (Committee Member); William Hintz Dr. (Committee Member) Subjects: Ecology; Environmental Science; Limnology