Herbivorous fishes include a diverse assemblage of species that target primarily benthic autotrophs. This is perhaps one of the most well-studied groups of coral reef fishes, often reputed to be key components of coral reef communities, contributing to coral reef health in numerous ways. Through their feeding ecology and benthic interactions, they help mediate algae-coral interactions which can allow for improved coral survival and health. Despite the wealth of literature documenting the prominent roles of these fishes in coral reef ecosystems, studies from the Red Sea are surprisingly lacking. The Red Sea is a marginal reef environment, with a host of unique environmental and biological characteristics making it a unique environment where dynamics of herbivory may differ. This dissertation aims to fill key gaps in our knowledge of herbivorous fishes through the study of their distribution and trophic ecology. Herein, I describe habitat-specific partitioning of Red Sea herbivorous fish assemblages, discovering higher diversity and abundance found in reefs closer to shower, dissimilar to findings from other regions. Cross-shelf variation in assemblage structure seems to be quite robust through time, indicating short-term stability in herbivore assemblages. Through the use of stomach contents and stable isotope analyses, I then investigate the trophic ecology of browsing herbivores across the same shelf-gradient. I found higher trophic redundancy on nearshore reefs through time, with increased variation in diet and high levels of complementarity on offshore reefs where macroalgae are scarce. Stable isotope analyses of both liver and muscle revealed the stability of this resource partitioning through time, demonstrating for the first-time temporal stability of resource partitioning within this group. This dissertation broadens our knowledge of herbivorous fishes, filling important gaps. It offers new insight into the role of habitat in structuring trophic ecology and how flexible the diets of browsing species can be. Together, this information creates a foundation where improved knowledge of herbivorous fish ecology could be incorporated into future management plans of ongoing giga projects within the Kingdom. Incorporating herbivores into these plans could allow for increased resiliency for Red Sea coral reefs in the face of future development and shifting climatology.

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Understanding how diversity is partitioned along natural and anthropogenic gradients within ecosystems is important to predict the persistence of species and the ecological functions they provide. Dottybacks (Pseudochromidae) are a diverse group of mesopredators that feed on cryptic macroinvertebrates and newly recruited fishes. This diet behavior may modify the composition and abundance of cryptobenthic fauna within coral reef ecosystems. Understanding how mesopredators partition their diet and the functional role provided by available prey within reefs can assist in understanding the ecological role these predators contribute to coral reef trophodynamics and the effect of their population changes on the reef ecosystem. To assess the diet of three common Pseudochromis species and two distinct color morphs of P. flavivertex in the Red Sea, I used a combination of i) visual stomach content analysis, ii) stomach DNA metabarcoding (18S, COI), and iii) stable isotope analysis (δ15N, δ13C). I evaluated i) dietary niche breadth, ii) variation in diet composition, iii) degree of dietary specialization, and iv) trophic level. These techniques revealed partitioning in the dietary composition and resource use between P. flavivertex, P. fridmani, and P. olivaceus. Although the two technics used for stomach content analysis did not show differences in the dietary composition within color morphs of P. flavivertex, the isotopic signature showed marked differences in the isotopic niche and resource use between morphs. Resource partitioning appears to be driven by variation in resource availability in the fish habitat and by subtle differences in the ecology of these species. These findings provide evidence of species-specific differences in the trophic ecology of pseudochromids in the Red Sea and demonstrate their important role as predators of cryptic invertebrates and small fish, being key components in energy transfer in coral reef ecosystems by acting as a link between cryptofauna and higher trophic levels. This study highlights the importance of combining several approaches (short-term: visual analysis and DNA metabarcoding; and long-term: isotope analysis) when assessing the feeding habits of coral reef fish, as they provide different and complementary information necessary to delimit their niches and understand the role that small mesopredators play in coral reef ecosystems.

<p><em>Helicobacter pylori </em>is a bacterial infection of the stomach lining known to cause ulcers and stomach cancer This infection has become a major concern of Indigenous peoples living in the Northwest Territories, where <em>H. pylori </em>infection and stomach cancer are more prevalent relative to much of southern Canada and the United States. I joined the Canadian North <em>Helicobacter pylori</em> (CAN<em>Help</em>) Working Group in 2010 to conduct participant observation in the Aklavik <em>H. pylori </em>Project (AHPP) and identify ways that ethnography can be integrated into the ongoing multi-pronged research that incorporates epidemiology, microbiology, gastroenterology, knowledge translation, and the development of public health policy.</p> <p>Between September, 2011 and June, 2012, I lived as a participant observer in Aklavik. I led an epidemiological study of the incidence and re-infection of <em>H. pylori </em>infection. I examined how different risk perceptions emerge from processes of “making sense” of <em>H. pylori </em>as a “pathogen” or as a “contaminant” and described how these different constructions influence people’s behaviours. Ethnography, in this way, can make visible the lenses through which different groups of actors perceive, experience, and react to <em>H. pylori </em>infection. The recognition that the social inequities most strongly associated with <em>H. pylori </em>infection and re-infection that exist today are the result of Aklavik’s colonial history is one example of a space in which different lenses can be brought into a shared focus. From such shared understandings, consensus knowledge can be built collaboratively between outside researchers and Indigenous Arctic communities in an ongoing, and community-driven, research project. Furthermore, I critically examined the definition and use of the “household” as a level-unit of risk assessment and have outlined steps for assessing possible risk factors as these are distributed across multi-household extended kin groups that can be identified and followed in long-term research.</p> / Doctor of Social Science

In aquatic environments Cu is both a vital nutrient and an important toxicant. Consequently fish require Cu as a micronutrient and can obtain this metal from either water or their diet. Inadequate intake of Cu is associated with reduced growth and development, while decreased growth rates, mortality and reduced swimming capacity have been reported in fish when Cu accumulates in excess of cellular needs. Characterization of Cu uptake is therefore critical in understanding the dynamics that govern toxicity and the risks associated with exposure to an aquatic contaminant. While mechanisms of waterborne uptake and toxicity are well understood, far less is known about gastrointestinal Cu uptake in fish. In vivo and in vitro techniques were therefore used in this study to investigate dietary Cu uptake in freshwater rainbow trout. The mid and posterior regions of the intestine emerged as important sites for Cu absorption in trout, while the role of the stomach and anterior intestine in Cu absorption requires further investigation. The intestinal uptake route was kinetically characterized as a low affinity absorption pathway as compared to the branchial route. Cu uptake appeared to occur via a hypoxia-resistant, carrier-mediated, saturable process which could be fueled by Cu(II)^2+ at concentrations typically found in the fluid phase of chyme in the trout intestine. Experimental manipulation of mucosal NaCl levels stimulated Cu uptake, Na2SO4 had an identical effect, implicating Na rather than the anion. These responses were unrelated to solvent drag, osmotic pressure or changes in TEP. The presence of excess luminal Ag and L-histidine stimulated Cu and Na uptake indicating that a portion of Cu transport was mediated by a Na-Cu co-transport system. Partial inhibition of Cu and Na uptake by phenamil and hypercapnia stimulated Na and Cu transport suggest Cu entry could also occur via the apical Na channel. The Na-dependent mechanism thus either involves more than one component or a unique Na-Cu co-transport mechanism with these combined characteristics mediates part of Cu uptake. Cu uptake was sensitive to pH and competed by Fe and Zn implicating DMT1 in the transport of Cu in the trout intestine. These factors had no effect on Na uptake, leading to the identification of a Na-independent mechanism for Cu uptake in the trout intestine. While the Na dependent nature of Cu uptake and Ag stimulated Cu transport argue against a role for Ctrl in this process, Cu transport characteristics identified in this study compare well with a recently identified Cu transporter in Ctr1 deficient mouse embryonic cells, indicating the existence of a similar transport mechanism in the trout intestine. / Thesis / Master of Science (MSc)

INTRODUÇÃO: O adenocarcinoma gástrico precoce (AGP) atinge até a camada submucosa em profundidade, independentemente da presença de metástases linfonodais (MLF). Tumores mucosos, bem diferenciados, menores que 20 mm e sem ulceração são candidatos à ressecção endoscópica (RE) por mucosectomia com taxas de MLF praticamente nulas. Com o advento da técnica de dissecção endoscópica da submucosa (ESD) e após observar ausência de MLF em grande série de pacientes no Japão, foi sugerido que os critérios clássicos pudessem ser expandidos, evitando a gastrectomia em alguns pacientes. Em países ocidentais autores e sociedades têm visto com restrição a ESD para critérios expandidos devido à observação de MLF em alguns subgrupos. A análise crítica e validação dos critérios expandidos de RE para tratamento do AGP em coorte brasileira poderá indicar os pacientes com menor risco de metástases linfonodais nesta população, de modo a individualizar o tratamento com excelência e qualidade de vida. OBJETIVO: Avaliar a presença MLF em produtos de gastrectomia com linfadenectomia de pacientes elegíveis à ressecção endoscópica seguindo os critérios clássicos e expandidos. MÉTODO: Inclusão de pacientes com AGP submetidos a tratamento cirúrgico com dissecção linfonodal. Estadiamento linfonodal e avaliação de características clínicas, macroscópicas e histopatológicas segundo critérios de RE. RESULTADOS: Foram incluídos 389 espécimens cirúrgicos de gastrectomia, dentre os quais 135 cumpriam critérios para ressecção endoscópica. Nenhum dos 31 pacientes com critérios clássicos apresentou MLF (N = 31; 0% IC95% 0 - 13,4%). Dos 104 com critérios expandidos, 3 apresentaram MLF (N = 104; 2,9% IC95% 0,7 - 8,6%), todos pertencentes ao grupo de tumores indiferenciados sem ulceração e menores que 20 mm. Dos pacientes com indicação de tratamento cirúrgico houve 50 MLF positivos (N = 254; 19,7% IC95% 15,3 - 25,1%). CONCLUSÃO: Existe risco mínimo de metástases linfonodais quando adotados os critérios expandidos de RE. Este risco é praticamente nulo para os critérios clássicos e quando se exclui o tumor indiferenciado do critério expandido / INTRODUCTION: Early gastric cancer (EGC) is known to present low rate of lymph nodal metastasis (LNM). Gastrectomy with D2 lymphadenectomy is usually curative for EGC. Endoscopic submucosal dissection (ESD) is a well-accepted treatment modality for lesions that meet the classic criteria, a well-differentiated adenocarcinoma measuring less than 20 mm size and without ulceration. Expanded criteria for ESD have been recently proposed, based on null LNM rate from large gastrectomies series coming from Japan. The expanded criteria for ESD are as follows: intramucosal non-ulcerative well-differentiated tumor > 20 mm, intramucosal ulc mo <= 30 mm, intramucosal non-ulcera mo <= 20 mm, or superficially submucosal ( m1) mo <= 30 mm. There is some resistance to adoption of the expanded criteria, since patients with positive LNM have already been reported in western centers. OBJECTIVE: Evaluate LNM staging in patients who met the expanded endoscopic treatment criteria for ESD. METHOD: Evaluation of gastrectomy specimens including LNM staging of patients submitted to gastrectomy for EGC in a 39-year retrospective cohort. A senior pathologist reviewed the histology slides. RESULTS: A total of 389 surgical specimens were included, of whose 135 met criteria for endoscopic resection. None of the 31 patients with classic criteria had LNM. Of the 104 patients with expanded criteria, 3 had LNM (n = 104, 2.9% CI 95% 0.7 - 8.6%), all of them with undifferentiated tumors without ulceration and less than 20 mm. In the patients with surgical criteria there were 50 LNM positive (n = 254; 19.7% CI 95% 15.3 - 25.1%). CONCLUSION: There is minimal risk of LNM in EGC when expanded criteria for ESD are met. This risk is practically nil for the classic criteria and when the undifferentiated tumor is excluded of the expanded criteria. Refinement of the expanded criteria for the risk of LNM may be desirable. Meanwhile the decision to complement the endoscopic treatment with LNM dissection or D2 gastrectomy will have to take into consideration the individual risk of perioperative morbidity and mortality

O Sistema nervoso entérico está localizados entre as camadas constituintes das paredes do trato gastrintestinal, entre as camadas musculares longitudinal e circular, que se estende por todo o trato digestório, desde o esôfago até o reto. Desordens gastrintestinais são complicações comuns causadas pela lesão térmica. A presente pesquisa avalia, em estômagos de ratos alterações na mucosa e no plexo mioentérico submetidos à lesão térmica corporal. O número de neurônios NADH-d e NADPH-d aumentaram significativamente nos animais queimados. Analisando a média da área do perfil dos neurônios NADH-dr e NADPH-dr evidenciaram uma diminuição significativa de 26% e 24%, respectivamente, na área do perfil dos neurônios dos animais queimados. Assim, associados o VIP o NO e a acetilcolina se apresentaram de maneira a interferir no esvaziamento gástrico causando ulcerações que foram observadas pela técnica da MEV na mucosa gástrica. Com esses dados, pode-se concluir que a LTC interfere no plexo mioentérico do estômago de ratos causando uma gastroparesia. / The enteric nervous system is located among the layer constituents of the gastrintestinal tract. Between the longitudinal and circular muscle layers, which extend throughout the digestory tract from the esophagus to the rectum. Gastrintestinal disorders are common complications caused by burn injury. This research evaluates, in stomach of rats changes in the mucosal and myenteric plexus, subjected burn injury. The number of neurons NADH-d and NADPH-d significantly increased in burned animals. Analyzing the average area of the profile of the neurons NADH-dr and NADPH-dr, showed a significant decrease of 26% and 24%, respectively, in the area of the profile of the neurons of the burned animals. Thus, the association of VIP, NO and acetylcholine is presented so as to interfere with gastric emptying causing changes in the mucosal wich were observed by the technique of MEV. With this data, it can be conclude that the burn injury interferes in the myenteric plexus of the stomach of rats causing a gastroparesis.

O estômago do rato completa sua maturação durante a fase de transição alimentar, em que ocorre ingestão de ração juntamente com leite materno. No desmame precoce (DP) esta fase é interrompida e provoca elevação da corticosterona (CORT). Nosso objetivo foi avaliar, através do tratamento com RU486 (RU), se a CORT elevada modifica a maturação gástrica. Grupos experimentais: amamentado (A), ARU, DP e DPRU. Resultados de PCRq, em filhotes: o DP elevou a expressão de Muc5ac, Bhlha15, Pgc e diminuiu a expressão de Pga5, enquanto que o RU486 reverteu os resultados para Pgc e Muc5ac,. Ainda em filhotes, DP aumentou o número de células mucosas do colo (CMCs), células Mist1-positivas e PGC-positivas, e o RU486 reverteu o resultado para as CMCs e para as PGC-positivas. Em adultos, obtivemos os seguintes dados: redução de Pga5, causada pelo RU486; manutenção dos efeitos do DP sobre Pgc; manutenção dos dados, tanto de DP quanto de RU486, sobre as CMCs; e dos efeitos do RU486 sobre as células PGC-positivas. Portanto, a CORT elevada pelo DP é fundamental na maturação gástrica. / Rat´s gastric mucosa completes their maturation throughout the food transition process, when pups ingest chow and maternal milk. Early weaning (EW) consists in an abrupt suckling (S) interruption that increases corticosterone (CORT) levels. Our aim was to evaluate, using RU486 (RU), if these increase in CORT levels could affect gastric maturation. Experimental groups: S, SRU, EW and EWRU. By RT-qPCR, in 17-d-old rats, EW increased Muc5ac, Bhlha15 and Pgc and decreased Pga5 expression, while RU486 reverted the results for Pgc and Muc5ac. In 17 and 18-d-old pups, EW increased mucous neck cells (MNC), Mist1-positive and PGC-positive cells, although CORT inhibition reverted the result for MNC and PGC. In 30-d-old rats, we had the following results: reduction on Pga5 expression provoked by RU486; the results over Pgc were maintained; the results, caused both by EW as RU486, over MNC were maintained, as well as the effects of RU486 over PGC-positive cells. We concluded that the increase in CORT levels, caused by EW, plays a fundamental role in gastric maturation.