Cardiovascular and metabolic effects of dietary selenomethionine exposure in fishes

Selenium (Se) is an essential micronutrient involved in important metabolic functions for all vertebrate species. As Se is reported to have a narrow margin between essentiality and toxicity, there is growing concern surrounding the adverse effects of elevated Se exposure caused by anthropogenic activities. Recent studies have reported that elevated dietary exposure of fish to selenomethionine (Se-Met) can alter aerobic metabolic capacity, energetics and swimming performance. My thesis aimed to further investigate mechanisms of sublethal Se-Met toxicity, particularly potential underlying cardiovascular implications of chronic exposure to environmentally relevant concentrations of dietary Se-Met in adult zebrafish (Danio rerio) and juvenile (yearling) rainbow trout (Oncorhynchus mykiss). In my first experiment, adult zebrafish were fed either control food (1.1 μg Se/g dry mass [d.m.]) or Se-Met spiked food (10.3 or 28.8 μg Se/g d.m.) for 90 d at 5% body weight per day. In the second experiment, juvenile rainbow trout were fed either control food (1.3 μg Se/g d.m.) or Se-Met spiked food (6.4, 15.8 or 47.8 μg Se/g d.m.) for 60 d at 5% body weight per day. Following exposure, ultrahigh resolution B-mode and Doppler ultrasound was used to characterize cardiac function. Chronic dietary exposure to elevated Se-Met had opposing results in zebrafish when compared to the rainbow trout. Zebrafish exposed to the highest dietary concentrations of Se-Met (28.8 μg Se/g d.m.) had significantly reduced ventricular contractile rate, stroke volume, and cardiac output, while Se-Met exposed rainbow trout had significantly greater stroke volume, ejection fraction, and cardiac output. Following ultasonography, energy stores were measured via whole body (zebrafish) and liver, heart and muscle (rainbow trout) glycogen and triglyceride concentrations. Zebrafish in the highest exposure group were observed to have greater whole body glycogen concentrations when compared to the control group, while rainbow trout exposed to Se-Met concentrations greater than 15.8 μg Se/g showed significant increases in both glycogen and triglycerides in liver relative to the control group. In addition, rainbow trout in the highest exposure group had significantly reduced capability of managing blood glucose levels as was evident after 48hrs in a glucose tolerance test. Exposure to Se-Met significantly decreased mRNA expression of a key cardiac remodelling enzyme, matrix metalloproteinase 2 (MMP2), in adult zebrafish heart, however significantly increased it (MMP9) in rainbow trout heart. Selenomethionine significantly increased echodensity at the junction between atrium and ventricle in zebrafish, and these results combined with increased MMP2 expression are consistent with cardiac remodelling and fibrosis. However, rainbow trout did not show any fibrosis and also had a significant decrease in SERPINH mRNA abundance, a molecular chaperone essential for the post-translational folding of fibril-forming collagens. This, taken together with the increase in MMP9, suggests an anti-fibrotic response in the rainbow trout heart, compared to the fibrosis seen in the zebrafish, which could help explain why there were opposing cardiovascular results. Due to the anti-fibrotic response in rainbow trout, the heart was apparently able to pump blood more effectively leading to the increase in stroke volume, ejection fraction, and cardiac output observed. The results of this study suggest that chronic exposure to dietary Se-Met can impact cardiac function, energy homeostasis and cause cellular perturbations, and such physiological consequences could reduce the aerobic capacity and survivability of fish. The varying results seen could be attributed to species sensitivity differences or perhaps due to the cold vs warm water fish selenium sensitivity

USE OF HIGH SURFACE NANOFIBROUS MATERIALS IN MEDICINE

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Life-history Characteristics of Recreational Lake Trout (Salvelinus namaycush) Fisheries in Manitoba

Contemporary data concerning lake trout (Salvelinus namaycush) populations have been lacking in the province of Manitoba for several decades. I compared life history characteristics (age, condition, growth, maturity, and survival) of lake trout from seven lakes in order to assess their present state. Furthermore, lake trout have been observed to have different ecotypes that exhibit different life-history traits and behaviours, therefore lake trout otolith morphology was compared to potentially identify suspected sympatric ecotypes in Clearwater Lake, Manitoba. Summer profundal index netting (SPIN) gillnets were set at varying depths during summer months in 2021 and 2022 to complete this project. Otolith morphology was compared using elliptic Fourier analyses. Length-at-age was back-calculated for lake trout individuals, and growth data was fitted by von Bertalanffy growth curves. Growth curves differed significantly across lakes based on several parameters (L8, K, t0, and w). Northern lakes had the propensity to hold trophy-sized lake trout, while southern lakes did not. Significant otolith morphological differences between suspected lake trout ecotypes within Clearwater Lake. However, it is not possible to ascertain that otolith morphological differences are a result of different ecotypes or differing growth rates. There was a notable scarcity of lake trout in most southern lakes, while northern lake trout populations appear to be healthy. Historical high fishing pressure might be a culprit associated with the poor status of several southern lake trout populations. Fisheries Manitoba should consider using the SPIN program to further evaluate lake trout fisheries in Manitoba.Master of Science in Bioscience, Technology, and Public Polic

Taxonomy and Ecology of Marine Algae

The term “algae” refers to a large diversity of unrelated phylogenetic entities, ranging from picoplanktonic cells to macroalgal kelps. Marine algae are an important primary producer in the marine food chain, responsible for the high primary production of coastal areas, providing food resources in situ for many grazing species of gastropods, peracarid crustaceans, sea urchins or fish. Recent findings indicate that marine environments have rapidly changed due to global warming over the past several decades. This change has led to significant variations in marine algal ecology. For example, a long-term increase in ocean temperatures due to global warming has facilitated the intensification of harmful algal blooms, which adversely impact public health, aquatic organisms, and aquaculture industries. Thus, extensive studies have been conducted, but there is still a gap in our understanding of the variation in their ecology in accordance with future marine environmental changes. To fill this gap, studies on the taxonomy and ecology of marine algae are highly necessary. We have invited algologists to submit research articles that enable us to advance our understanding of the taxonomy and ecology of marine algae. Fourteen papers have been collected so far, which cover different aspects of the taxonomy and ecology of marine algae, including understudied species, interspecific comparisons, and new techniques

Photoactive Molecules in Supramolecular Architectures and Photoredox Reactions

My PhD reasearch activity was mainly focused on two different fields: the study of the formation of supramolecular architectures and the investigation of the photophysical behaviour of different photocatalysts in organic reactions. The first supramolecular system shown in this thesis derives from a shapepersistent molecule, featuring four bipyridinium units, that upon reduction undergoes intermolecular pimerization because of the rigid architecture of the molecule. The same tetramer, with non-methylated bipyridium units, is able to form a supramolecular architecture upon complexation with four ruthenium porphyrins: the resulting multichromophoric system features a shape-persistent arrangement of the chromophores. During my PhD, I spent four months at the ETH, in Zurich, working in the group of Prof. Schlüter. Throughout my stay, I worked on the design, synthesis and characterization of a 2D polymer obtained at the air-water interface with Langmuir-Blodgett technique. In the field of photocatalysis, I studied four photoredox reactions, two of them photocatalyzed by a metal complex, and the other two by an organic chromophore. The first photoredox reaction studied provides an efficient access to indole 2- and 3-carboxylates in a single step (with good yields under mild reaction conditions), i.e. the direct photocatalytic carboxylation with CBr4/MeOH, visible light ad [Ru(bpy)3](PF6)2 as photocatalyst. In the second reaction, the complex [Fe(bpy)3]Br2 is involved in the enantioselective organocatalytic photoredox alkylation of aldehydes with various alpha-bromo carbonyl compounds, in presence of visible light. Then, we moved toward the use of organic dyes as photocatalysts. We found that a iodo-boron-dipyrromethene (iodo-BODIPY) dye derivate is able to promote the atom-transfer radical addition (ATRA) between bromoderivatives and alkenes, using ascorbate as sacrificial reductant. Finally, we investigated the mechanism of the reduction of aryl halides promoted by a two-photon mechanism by perylenediimide derivate