No description available.

Invasive species are a known stressor on aquatic ecosystems, particularly in the waters of the Great Lakes basin. A recent invader, Hemimysis anomala, has had significant impacts on the food webs of Europe, where it invaded previous to its spread to North America. However, despite the fact that Hemimysis is now widespread in the Great Lakes basin, no analysis has been done on the trophic position of Hemimysis in North America invaded sites. This thesis used carbon (??13C) and nitrogen (??15N) stable isotopes to examine spatial and temporal patterns in Hemimysis trophic niche use in invaded North American sites in an attempt to broaden the knowledge base on this invader and to examine potential impacts this invader may have on the food webs of the Great Lakes. A spatial comparison of trophic niche use by Hemimysis among 13 sites in Lake Erie, Lake Ontario, and the St. Lawrence River was conducted between late July and mid-September of 2011. Main sources of carbon (benthic versus pelagic production) and trophic offset, or trophic distance from basal food web items, of Hemimysis were quantified using Hemimysis ??13C and ??15N values. Results indicated that: 1) Hemimysis relied predominantly on pelagic carbon sources at the majority of sites, and isotopic differences between life-stages existed at two of the 13 sites examined, 2) the trophic offset and reliance on pelagic food sources did not differ significantly between lotic and lentic sites, and 3) the isotopic niche width of Hemimysis was spatially heterogeneous, varying by an order of magnitude among sites, but was unrelated to the degree of isotopic variation in the basal food web at each site. Observed ranges in trophic offset and the pelagic fraction of dietary carbon indicate that Hemimysis derives carbon from both benthic and water column sources, as well as at multiple trophic levels. Results support the notion that Hemimysis is an opportunistic omnivore that displays significant dietary flexibility. To test the relative importance of key biotic and abiotic factors, taken from the literature, in driving Hemimysis isotopic variation, a temporal analysis was conducted at two North American sites, one in Lake Ontario and one in the St. Lawrence River, which were repeatedly sampled for Hemimysis and related food web items between September 2008 and January 2012. Seasonal patterns of winter enrichment ??? summer depletion were found in Hemimysis ??15N in Lake Ontario, but a similar pattern was not seen in the St. Lawrence River. Multiple regression models were used to determine the importance of water temperature, Hemimysis C:N ratios, Hemimysis length, and the isotopic values of basal food web components in explaining observed variation in Hemimysis ??13C and ??15N values. Significant relationships were found between Hemimysis isotopic values and water temperature, but relationships with the isotopic signatures of the pelagic basal food web were weak or nonexistent. Hemimysis ??13C values were significantly correlated with C:N ratios. Strong evidence of an ontogenetic dietary shift was found in Lake Ontario, with length showing a significant positive correlation with Hemimysis ??15N. All together the factors included in the models explained little of the observed variation in Hemimysis isotopic values, with approximately 20 % of the observed variation in Hemimysis ??13C, and just under half of Hemimysis ??15N variation, being explained by the included factors. As such, Hemimysis isotopic variation must be explained by factors not included in this study and may include factors such as species composition of the invaded site and availability of prey. Overall, the results of this thesis highlight the opportunistic and flexible nature of Hemimysis diet, and demonstrate the need for future work to determine the main drivers of isotopic variability and trophic niche selection of Hemimysis. The degree of trophic flexibility seen in Hemimysis implies that potential food web impacts will be site specific and heavily reliant on food web dynamics and environmental characteristics of the invaded site.

Nitric oxide (NO), a free radical released by macrophages (a subset of white blood cells) as a response to infection, is noxious to organisms due to its ability to disable crucial biomolecules such as lipids, proteins and DNA. Although normally effective at eradicating invading bacteria, several pathogens have developed mechanisms to detoxify NO and its toxic by-products, reactive nitrogen species (RNS). While some of these detoxification processes have been characterized, very little is known about the metabolic changes that enable microbes to survive this deleterious environment. Investigations into the effects of RNS on microbial physiology have shown that these harmful radicals inactivate the citric acid cycle and oxidative phosphorylation, the series of reactions responsible for making energy aerobically. The central aim of this thesis was to determine how the organism counteracts the detrimental effects of RNS, while bypassing the ineffective central metabolic pathways. The findings presented herein show that P. fluorescens engineers an elaborate metabolic network to generate ATP whilst withstanding the injurious effects of nitrosative stress. Crucial to this adaptation is the ability to produce energy via substrate level phosphorylation, a necessity that arises out of the cells’ inability to produce a substantial amount of ATP using the electron transport chain (ETC). The up-regulation of the enzymes citrate lyase (CL), phosphoenolpyruvate carboxylase (PEPC) and pyruvate, phosphate dikinase (PPDK) helps the organism accomplish this feat. Blue native polyacrylamide gel electrophoresis (BN-PAGE), high performance liquid chromatography (HPLC) as well as co-immunoprecipitation (CO-IP) studies were applied to demonstrate that these proteins form a metabolon, a transient complex of enzymes that ensures citrate is converted into its desired end products, pyruvate and ATP. In order to gauge the individual contributions iv of phosphoenolpyruvate-dependent kinases, a novel in-gel activity assay was developed to probe these enzymes under disparate conditions. These results suggest that the organism switches from an ATP-dependent metabolism to one based on the utilization of pyrophosphate (PPi). The rationale for this appears to be energy efficiency, as pyrophosphate-dependent glycolysis can theoretically produce five ATP rather than the two yielded by Embden-Meyerhof glycolysis. Additionally, the up-regulation in activity of the enzymes adenylate kinase, nucleoside diphosphate kinase and acetate kinase seem to ensure that ATP generated by PPDK is properly shuttled and stored when aerobic metabolism is defective. The lower activity of inorganic pyrophosphatase likely ensures an adequate supply of pyrophosphate for the activity of PPDK. Taken together, this research reveals the critical role metabolism plays in the survival of microbes under the onslaught of NO and RNS. As several of these enzymes are absent in mammalian systems, they present themselves as novel targets for the development of new antibacterial agents. A comprehensive awareness of bacterial defense systems in response to NO may lay the groundwork to developing more effective treatments to impede microbial infections.

Prior to 1993, freshwater angling in South Africa had been governed by the respective nature conservation legislation of the four South African provinces, the four “independent homelands" and the six so-called Bantustans. In 1993 a South Africa with nine provinces was created, of which only Limpopo and Mpumalanga promulgated its own laws governing freshwater angling. From 2008 angling for listed threatened and protected freshwater fish species has been regulated by the National Environmental Management: Biodiversity Act, supplemented by the Threatened or Protected Species Regulations. In addition, it is anticipated that the Alien and Invasive Species Regulations, which will regulate angling for listed alien and invasive freshwater fish, will be promulgated in the near future. The result is that freshwater angling is currently being governed by a plethora of pre-1993 provincial, homeland and Bantustan legislation, two post-1993 provincial acts, as well as post-1993 national legislation. In this dissertation the South African freshwater angling legislative framework was critically analysed. It was found that the multitude of fragmented and complex laws, created 15 “angling provinces” which leads to confusion amongst anglers and government officials alike. In the process legal certainty and reasonableness, cornerstones of a sound legal system, are being compromised, indigenous freshwater fish are not adequately protected and alien or invasive freshwater fish are not properly managed. In the light of the above, and after taking comments by anglers and enforcement officials into account, recommendations are made for an improved legislative framework for freshwater in South Africa. It is recommended that all freshwater fish species be managed and/or protected on a catchment basis, as opposed to the current provincial basis. This will ensure legal certainty and reasonableness and that all indigenous freshwater fish which are subject to the similar threats are protected adequately and uniformly. / Thesis (M. Environmental Management)--North-West University, Potchefstroom Campus, 2010.

Prior to 1993, freshwater angling in South Africa had been governed by the respective nature conservation legislation of the four South African provinces, the four “independent homelands" and the six so-called Bantustans. In 1993 a South Africa with nine provinces was created, of which only Limpopo and Mpumalanga promulgated its own laws governing freshwater angling. From 2008 angling for listed threatened and protected freshwater fish species has been regulated by the National Environmental Management: Biodiversity Act, supplemented by the Threatened or Protected Species Regulations. In addition, it is anticipated that the Alien and Invasive Species Regulations, which will regulate angling for listed alien and invasive freshwater fish, will be promulgated in the near future. The result is that freshwater angling is currently being governed by a plethora of pre-1993 provincial, homeland and Bantustan legislation, two post-1993 provincial acts, as well as post-1993 national legislation. In this dissertation the South African freshwater angling legislative framework was critically analysed. It was found that the multitude of fragmented and complex laws, created 15 “angling provinces” which leads to confusion amongst anglers and government officials alike. In the process legal certainty and reasonableness, cornerstones of a sound legal system, are being compromised, indigenous freshwater fish are not adequately protected and alien or invasive freshwater fish are not properly managed. In the light of the above, and after taking comments by anglers and enforcement officials into account, recommendations are made for an improved legislative framework for freshwater in South Africa. It is recommended that all freshwater fish species be managed and/or protected on a catchment basis, as opposed to the current provincial basis. This will ensure legal certainty and reasonableness and that all indigenous freshwater fish which are subject to the similar threats are protected adequately and uniformly. / Thesis (M. Environmental Management)--North-West University, Potchefstroom Campus, 2010.

The riparian forests are hotspots of biodiversity and serve important roles in maintainingthe water quality. The study and understanding of this ecosystem is basic to know how theriparian zones respond to the threat and the changes produced by the urbanization. Theobjective of this pilot study was to know the species richness and check the status of theriparian vegetation along two different rivers in Halmstad, Nissan and Fylleån. The studywas focus on the status of trees at both rivers to see if the proximity of the city has anyimpact on the biodiversity. In total 9 different species were found, nevertheless only 3 ofthese species were founded on both localizations: Quercus robur, Betula pendula and Pinussylvestris. The Shannon Index showed a higher biodiversity on Nissan riparian zones, whichis the river that present the urban component. The urban area is the one that presentshigher level of biodiversity, tree species and number of individuals but there are notenough to be in a good standard. The result just show that the urban area is in a bettercondition that the natural one. The institutional efforts should be focusing on preserveboth environments with special attention to the natural environment.

No description available.

Background: Hypertension is a pathological increase in blood pressure that affects nearly 30% of the U.S. population and is a primary modifiable risk factor for cardiovascular disease. Despite advancements in prevention and treatment, hypertension is still one of the most common conditions around the world, and for a majority of cases the causal mechanisms remain to be fully elucidated. A growing body of literature suggests that oxidative stress status may play an etiological role in many chronic conditions, including hypertension. Specifically, a systemic overabundance of reactive oxygen species may give rise to endothelial dysfunction, increased sodium and H2O retention, and alterations in sympathetic outflow, leading to an increase in blood pressure. Purpose: The main objective of this study is to investigate the prospective association between F2-isoprostanes, a validated biomarker of oxidative status, and development of hypertension in a large, multi-centered, multi-ethnic cohort of adults aged 40-69 at baseline. Methods: This is a secondary data analysis that utilized previously collected data from the Insulin Resistance Atherosclerosis Study. 844 participants were included in the analysis. Briefly, four urinary F2-isoprostane isomers (F2-IsoP1, F2-IsoP2, F2-IsoP3, and F2-IsoP4) were quantified using liquid chromatography/ tandem mass spectrometry and adjusted for urinary creatinine levels. Hypertension was assessed at baseline and follow-up visits and defined as systolic blood pressure > 140 mm Hg and/or diastolic blood pressure > 90 mm Hg and/or currently taking antihypertensive medications. Crude associations between study population characteristics and hypertensive status were analyzed with the chi-square and Wilcoxon-rank sum tests. Crude associations between study population characteristics and F2-isoprostane levels were analyzed with Wilcoxon-rank sum, Kruskal-Wallis, and Spearman’s rank correlation measures. Finally, the adjusted prospective associations between hypertensive status and F2-isoprostane concentrations were modeled using logistic regression. Results: Of the 844 participants who were included in the study, 258 (31%) were classified as hypertensive at baseline. Among the 586 participants who were normotensive at baseline, 123 (21%) developed hypertension over the five-year study period. Importantly, none of four F2-isoprostane isomers predicted a significant increase in the odds of developing hypertension, as indicated by their odds ratio 95% confidence intervals; F2-IsoP1: (0.85, 1.31), F2-IsoP2: (0.62, 1.13), F2-IsoP3: (0.80, 1.27), and F2-IsoP4: (0.84, 1.29). Conclusion: Previous studies have investigated the association between oxidative status and hypertension prevalence, however the cross sectional nature of the study designs have made it difficult to establish temporality between exposure and outcome. To our knowledge, this is the first study to model the odds of developing hypertension as a function of F2-isoprostane levels. The results of this study suggest that oxidative status is not involved in the development of hypertension.

No description available.

The pathogenesis of diabetic nephropathy (DN) remains incompletely understood. In previous studies, we observed the activation of Tyr kinase Src by high glucose (HG) and showed that Src is required for MAPK activation and synthesis of collagen IV in cultured rat mesangial cells (MCs). Reactive oxygen species (ROS) are also important mediators of DN, and our present study aimed to investigate the role of Src in HG-induced ROS generation. In MCs, we found that HG led to ROS accumulation that was blocked by Src inhibitors or Src-specific siRNA. Downstream of Src, Vav2 was phosphorylated/activated leading to Rac1-dependent NADPH oxidase activation. Long-term HG exposure resulted in Src-dependent Nox4 protein induction. Nox2-specific siRNA abrogated ROS production only in short-term HG, while Nox4-specific siRNA blocked ROS production only in long-term HG. Taken together, our data indicate Src to be important in mediating ROS generation from both Nox2- and Nox4-containing NADPH oxidases.