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Pulmonary valve stenosis (PS) is the most common congenital heart defect in dogs. The condition is due to abnormal valve anatomy present at birth that leads to stenosis of the right ventricular outflow tract. The valve stenosis results in pressure overload of the right ventricle. If severe enough, the stenosis leads to right ventricular hypertrophy, arrhythmias, exercise intolerance, and right-sided heart failure. Severity of disease is typically determined based on velocity of blood flow across the lesion via echocardiography. The median survival time for dogs with severe PS is 4-5 years with medical management, while moderately affected cases have a variable prognosis. The prognosis for mild PS is generally good. The Bulldog, which is the fourth most popular breed according to AKC dog rankings, is a breed highly overrepresented in PS cases. Due to this breed predisposition PS is suspected to be inherited. Mildly affected dogs are frequently not diagnosed as traditional auscultation-based tests are insensitive in dogs with profound airway sounds and barrel-shaped chests such as the Bulldog. These subclinical cases make it incredibly difficult to successfully screen and remove affected individuals from the breeding program. Thus, hindering breeding efforts to reduce disease prevalence. Therefore, the development of a genetic screening test represents the most practical approach to identification and reduction of disease frequency in the breed. Additionally, severe and moderately affected PS cases are treated with traditional balloon valvuloplasty, which has good but variable success. The procedure has a significant cost, does not restore normal function, and there is considerable anesthetic risk for the brachycephalic breeds that are predisposed to PS. Additionally, some PS-affected dogs have concurrent coronary anomalies, which are expensive to identify and make balloon valvuloplasty contraindicated, further highlighting the need for genetic screening tests for this condition. There is limited information about the genetic cause of PS in humans with the majority of mutations involving the RAS-MAPK pathway. Although PS is commonly seen in puppies, no mutation to date has been identified, although literature suggests a possible recessive pattern of inheritance. Through the combined efforts of the clinical cardiology service at the University of California Davis, clinical cardiology service at Colorado State University, and the Translational Cardiac Genetics and Pharmacogenomics Laboratory in the University of California Davis School of Veterinary Medicine we aim to elucidate the genetic mechanisms of PS in Bulldogs. The goal of this dissertation is to compile and contribute to what is currently known about the genetics of PS in humans and animals. A retrospective study in a large referral hospital population allowed determination of the prevalence of this disease in dogs and confirmed common breed predisposition. A pedigree analysis was performed in the most affected breed, the Bulldog, to elucidate a common mode of inheritance. A genome-wide association study was performed to refine a region of interest in the canine genome that is associated with PS. Whole genome sequencing followed by variant analysis allowed identification of mutations associated with the disease. The most plausible variants underwent validation in a large population of dogs using MassArray and those that continued to segregate were followed up with immunohistochemistry in cardiac tissue. Finally, the results of this project will contribute to the understanding of heart development and congenital heart disease in dogs overall, thus guiding novel prevention and therapeutic strategies for PS.

Coral reefs are currently threatened by both natural and human-driven disturbances, and climate change scenarios suggest that the health of future reefs is uncertain. To better inform management and preservation of coral reef ecosystems, it is critical that we understand the mechanisms that support recovery of coral habitat after coral mortality events. Macroalgae can inhibit coral recovery by preventing recruitment and growth of corals after a disturbance, leading to a shift in the dominant benthic community from coral to macroalgae. These macroalgal habitats do not support the same diversity of fish and other species as healthy coral reefs, and are thus undesirable on large scales. This dissertation addresses some processes that are important in the establishment and persistence of these macroalgal phase shifts. Through an enhanced understanding of macroalgal persistence, we may be able to identify (and protect) key species and processes that are critical to promoting coral reef recovery.I used the macroalga Turbinaria ornata as a model species to examine the potential for herbivore-algal feedbacks that can promote persistent macroalgal phase shifts. This species is perennial and patches appear to persist inter-annually once established. In areas where macroalgae is present, Turbinaria largely dominates the benthic community. Results of observational studies of tagged Turbinaria patches suggest that Turbinaria populations exhibit positive population growth (both number of adult thalli and patch area increased over a 2 year period). Several factors including high turnover rates of thalli, year-round reproduction, and a buffer of immature individuals that may act as a “seed bank” following a disturbance may contribute to the expansion of this species in the lagoons of Moorea.In addition, I used field experiments to assess the potential for associational refuge to provide a mechanism for Turbinaria persistence in the lagoons of Moorea. Results from these experiments suggest that an associational refuge may facilitate persistence of Turbinaria, as predation on small vulnerable individuals (< 2 cm in length) is reduced when associated with larger, less palatable adults. However, the significance of this refuge depends on the local abundance of browsing herbivores that can consume macroalgae. An associational refuge that results in higher recruit survival in the presence of herbivory could represent a self-reinforcement mechanism that could facilitate the establishment and multi-generational persistence of Turbinaria patches on coral reefs.To determine the effects of herbivore pressure on the development and persistence of a macroalgal community, I examined the effects of herbivores on mature (dominated by the late stage macroalga Turbinaria ornata) and early stage (dominated by turf algae) algal communities. Results suggest that the effects of herbivores depend upon the initial conditions of the benthic community, and this may have implications for management practices for disturbed, degraded and healthy reefs. Herbivores, particularly browsing fish that can consume mature macroalgae, appear to be limited in their capacity to remove established macroalgae. These critical species appear to be present in low abundance in some habitats, and are targeted as part of a local fishery. In contrast, other herbivores (grazers that consume turf algae and immature macroalgae) appear to readily limit the development of macroalgal communities. I also found that herbivores differentially influence the richness of macroalgal communities depending on the initial macroalgal community. Specifically, an initial presence of the mature macroalga, Turbinaria ornata, enhanced richness of macroalgal assemblage even as herbivore pressure increased. At the same level of herbivore pressure, communities with Turbinaria present had greater richness than communities that initially were dominated by turf algae, even after two years. Results from this experiment provide some of the first empirical tests of hysteresis (path-dependency) in reef recovery, and reinforce the importance of different herbivore functional groups at different points along the recovery trajectory.Overall, this research highlights characteristics of macroalgae and interactions between macroalgal and herbivore communities that can drive persistent macroalgal phase shifts in coral reef ecosystems. This information may be used to develop sustainable management and conservation strategies to preserve these valuable ecosystems and the services that they provide for local communities.

Hydrogen sulfide is a toxic gas that has been found to be a rising cause of accidental deaths in high concentration. Currently there is no effective treatment for hydrogen sulfide poisoning. Paraquat is a widely used herbicide that is harmful when ingested and is especially concerning with its potential use in terrorist plots. Cobinamide, a vitamin B₁₂ precursor, has been proven to be an effective antidote for cyanide poisoning. Based on the chemical properties of cobinamide and of hydrogen sulfide and paraquat, we hypothesized that cobinamide could potentially reduce hydrogen sulfide- and paraquat-induced cellular toxicity. In this study, we tested that hypothesis by assessing whether cobinamide could rescue cells exposed to hydrogen sulfide and paraquat. Two cell lines, African Green Monkey Cercopithecus aethiops fibroblast-like kidney cells (COS7) and human foreskin fibroblast cells (HFF), were used in the experiments. After exposure to hydrogen sulfide or paraquat, with or without cobinamide, cells were counted at 24, 48, and 72 hour time points in order to obtain a growth curve and to calculate the number of cell doublings. Our results demonstrated that 1mM of hydrogen sulfide significantly inhibited cell growth and 400[um]M cobinamide treatment effectively reversed the inhibition in both cell lines. A 2mM cobinamide treatment was capable of preventing cell growth inhibition induced by 1.35mM paraquat in both COS7 and HFF cells. These results form the foundation for further studies to determine if cobinamide might be an effective treatment for hydrogen sulfide and paraquat poisoning

Hydrogen sulfide is a toxic gas that has been found to be a rising cause of accidental deaths in high concentration. Currently there is no effective treatment for hydrogen sulfide poisoning. Paraquat is a widely used herbicide that is harmful when ingested and is especially concerning with its potential use in terrorist plots. Cobinamide, a vitamin B₁₂ precursor, has been proven to be an effective antidote for cyanide poisoning. Based on the chemical properties of cobinamide and of hydrogen sulfide and paraquat, we hypothesized that cobinamide could potentially reduce hydrogen sulfide- and paraquat-induced cellular toxicity. In this study, we tested that hypothesis by assessing whether cobinamide could rescue cells exposed to hydrogen sulfide and paraquat. Two cell lines, African Green Monkey Cercopithecus aethiops fibroblast-like kidney cells (COS7) and human foreskin fibroblast cells (HFF), were used in the experiments. After exposure to hydrogen sulfide or paraquat, with or without cobinamide, cells were counted at 24, 48, and 72 hour time points in order to obtain a growth curve and to calculate the number of cell doublings. Our results demonstrated that 1mM of hydrogen sulfide significantly inhibited cell growth and 400[um]M cobinamide treatment effectively reversed the inhibition in both cell lines. A 2mM cobinamide treatment was capable of preventing cell growth inhibition induced by 1.35mM paraquat in both COS7 and HFF cells. These results form the foundation for further studies to determine if cobinamide might be an effective treatment for hydrogen sulfide and paraquat poisoning