Arsenic (As) contamination presents an ecosystem and human health risk at Giant Mine, a historic gold mine near Yellowknife, NWT currently undergoing the final stages of assessment for remediation. Arsenic concentration is elevated in sediments at Giant Mine due to contamination from several forms of mine waste including flotation tailings, roaster calcine and impoundment spills. The Giant Mine Remediation Project has stated aims to remediate the surface of the site, including Baker Creek which runs through the property, to a condition that is a productive environmental habitat and spawning ground. Environmental scanning electron microscope (ESEM) and synchrotron-based micro- X-ray Absorption Near Edge Spectroscopy (µXANES), micro-X-ray fluorescence (μXRF) and micro-X-ray diffraction (μXRD) techniques were employed to characterize the As-host phases and determine the solid-phase speciation of As in mine waste and sediments. Arsenopyrite, Fe-oxides, Fe-root plaque, and As_2 O_3 were the major phases identified. Sediment toxicity was measured using 10-day Chironomus dilutes and 21-day Pimephales promelas exposure tests. The toxicity tests found responses ranging of from 100% mortality at the most contaminated site to no statistical difference to the control groups in the least As contaminated site. Toxicity test chamber conditions were directly monitored with dialysis probes (mini-peepers) and Diffusive Gradients in Thin Films (DGTs). DGT and mini-peeper deployment in the test beakers allowed for direct correlation of their measurements to trace metal uptake and bioaccumulation during the toxicity tests. Linear regression and ANOVA statistics were used to correlate, when possible, As tissue concentrations in Chironomus dilutes and Pimephales promelas to DGT, mini-peeper and surface water concentration measurements. Statistical analysis was also conducted for Co, Cr, Cu, Ni, Pb, Zn, and Sb though these other metal/metalloids were not always suitable for analysis due to constraints caused by detection limits. It was found that DGT As was statistically correlated (r2=0.836 and p<0.0005) to uptake in Pimephales promelas but that total element concentrations were also statistically relevant and slightly better at predicting uptake (r2=0.873 and p<0.0005). Mini-peepers could not be analyzed statistically due to challenges in their use within some highly vegetated sediment samples. / Thesis (Master, Geological Sciences & Geological Engineering) -- Queen's University, 2014-05-01 11:47:59.482

Botulism is a foodborne intoxication caused by ingestion of Clostridium botulinum neurotoxin (BoNT). Preliminary studies focussed on the production of polyclonal antisera against BoNT/E by immunizing a rabbit with botulinal toxoid type E. The antiserum was subsequently used to detect BoNT/E using the slot blot immunoassay where samples were applied to a slot blot filtration manifold and drawn by vacuum through a membrane. The membrane was then immunologically processed before chemiluminescent detection. However, the antisera lacked specificity and cross-reacted with closely related clostridia strains. / The specificity of the antisera was increased by adsorbing cross-reactive antibodies from whole antisera with affinity columns made with total proteins from culture supernatants of closely related clostridia. Alternatively, specific antibodies were isolated with an affinity column prepared with C. botulinum type E toxoid. / Different methods of concentrating BoNT/E in each sample prior to testing them were evaluated to increase the sensitivity of the assay. / The slot blot immunoassay was then evaluated for detection of BoNT/E in mixed cultures and in food samples. (Abstract shortened by UMI.)

My thesis focuses on copepod-diatom interactions, specifically on the effects of food quality and toxicity on copepod feeding, reproductive success and behavior but as a frame, also includes a quantitative evaluation of copepod carbon requirements compared to other trophic plankton groups. My aim was to evaluate the function of copepods in diatom-dominated spring blooms. I thereby used a series of mesocosm and laboratory experiments. For a realistic extrapolation of the results to natural environments I used different strains of a diatom species, Skeletonema marinoi, which is a common spring blooming species in the Baltic Sea. This species is known to produce polyunsaturated aldehydes (PUA; mainly heptadienal, octadienal and decadienal), which have previously been identified as the potential reasons for the detrimental effects of diatoms on copepod reproduction. All strains varied in size, mineral and biochemical content, and PUA production. I tested the effects on different dominant copepod species from northern temperate waters; Acartia sp. (A. clausi and A. tonsa), Calanus finmarchicus, Pseudocalanus elongatus, and Temora longicornis, as well as the dominant species in the northern Baltic Sea, Eurytemora affinis. The specific contributions of respiratory carbon requiment of mesozooplankton and lower size fractions to carbon cycling during PUA-producing diatom blooms are poorly documented. My results show that nanoplankton and microzooplankton dominated the carbon cycling (&gt; 50% of primary production) whereas the contribution of bacterioplankton varied. Mesozooplankton was always of minor importance with contribution of &lt;6% of primary production.  This illustrates the importance of lower size fractions during a phytoplankton spring bloom. Irrespective of their small contribution to the total community carbon cycling, copepods displayed non-selective and typically high feeding rate on different PUA-producing S. marinoi strains, indicating that there was no feeding deterrence. The effect of feeding on copepod reproductive success, however, varied between different strains, and depending on copepod species. In experiments with monospecific diatom diets reduced egg production rate and hatching success were mainly related to food quality measured as fatty acids and sterols, or algae growth rate, low assimilation efficiency or PUA production / ingestion. On the other hand, copepod reproduction and population development in the diverse diet, including a high concentration of S. marinoi and PUA (both particulate and dissolved), increased with increasing food concentration and was unaffected by the presence of toxic diatoms. I conclude that although a negative correlation between different reproductive variables and PUA production / ingestion may sometimes be observed in laboratory incubations, this is highly dependent on the strain / species used, and the effect of the algal strain can be stronger than the effect of the e.g., growth-stage dependent PUA production. Although copepod grazing might not be very important during a diatom spring bloom, even a highly PUA-producing S. marinoi can be considered an appropriate food source for copepods when occurring among the natural food assemblage, inducing a high reproductive output.

Thesis (M.S. - Hydrology and Water Resources)--University of Arizona, 1989. / Includes bibliographical references (leaves 147-156).

Thesis (M.S.)--Baylor University, 2007. / Includes bibliographical references (p. 44-46).

Thesis (M.Sc.) Uppsala : Sveriges lantbruksuniv.

Thesis (M.A.S.)--University of Delaware, 2008. / Principal faculty advisor: Chin-Pao Huang, Dept. of Civil and Environmental Engineering. Includes bibliographical references.

Ph.D.

Orientador: Carlos Eduardo Vergani / Resumo: A associação da prata a outros compostos vem sendo estudada em uma tentativa de acentuar as propriedades antimicrobianas e reduzir a citotoxicidade deste metal quando em altas concentrações. O presente estudo investigou o efeito dos microcristais: tungstato de prata (α-Ag2WO4) e molibdato de prata (β-Ag2MoO4), no comportamento das células gengivais em monocamada e em modelo de matriz de colágeno, simulando a reparação tecidual. Para isto, fibroblastos gengivais (FGH) foram cultivados e utilizados somente entre as passagens 3 e 8 para formação de monocamada e para a confecção do equivalente dermal em matriz de colágeno em três dimensões (3D). Ambos microcristais foram utilizados na concentração fungicida mínima (CFM) capaz de matar o fungo Candida albicans (C. albicans) e foram definidas como C2: 7,81 µg/mL para tungstato de prata e 15,62 µg/mL para molibdato de prata. A partir destes valores, concentrações 10 vezes concentradas (C3) e 10 vezes diluídas (C1) foram preparadas para melhor compreender a margem de efeito dos componentes sobre as células estudadas. Células incubadas com meio de cultura na ausência de microcristais foram utilizadas como controle negativo (C-) e células incubadas com tampão de lise (TL) como controle positivo, representando 100% de morte celular. O efeito dos microcristais na morfologia, viabilidade e proliferação das células foram inicialmente avaliados e direcionaram os experimentos sequenciais. A geração de espécies reativas de o... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Growing interest has been reported in combining silver with other metals to improve the antimicrobial properties, reduce silver concentration and consequently its toxicity. Herein, this study investigated the effect of microcrystals silver tungstate (α- Ag2WO4) and silver molybdate (β-Ag2MoO4) on the gingival cells and threedimensional (3D) collagen matrices behavior. For all experiments, human gingival fibroblasts cells (HGF) were used between the 3rd and 8th passage. To carry out the experiments, lowest concentrations of α-Ag2WO4 and β-Ag2MoO4 that prevents visible growth of Candida albicans (C. albicans) planktonic cells were defined as our test concentration (C2): 7,81 µg/mL for silver tungstate and 15,62 µg/mL for silver molybdate. Solutions prepared from initial MFC concentration, ten-folds diluted (C1) and ten-folds concentrated (C3), improved the knowledge about the concentration ranging effect against human cells. Complete medium (C-) was used as a negative control and lysis buffer (LB) served as positive control (C+), equating to 100% cell death. The effect of the microcrystals concentration on cell morphology, viability and proliferation of HGF cells led following experiments. Reactive oxygen species (ROS) generation and DNA integrity analyzes were mandatories to know the real impact of the microcrystals on human cells. The quantitative and qualitative results showed that α-Ag2WO4 did not affect mitochondrial enzymatic activity of HGF cells cultured in monolayer an... (Complete abstract click electronic access below) / Mestre

Increasingly, drug-induced liver injury is one of the main reason for drugs to be withdrawn from the market even after passing toxicity studies in pre-clinical and clinical trials because of risks of toxicity and ineffective treatments. Human immortalised hepatocyte cell lines used in drug testing are widely available, inexpensive and easy to culture. However, these cell lines are commonly known to have poor predictive capabilities and improved in vitro hepatic models are required for predicting hepatotoxicity of large numbers of compounds in drug discovery. In this study, the primary goal was to develop an improved in vitro human hepatic model using a combination of the C3A human hepatic cell line and human umbilical vein endothelial cells (HUVECs), for prediction of acetaminophen (APAP) hepatotoxicity. Initial experiments showed that co-culture of HUVEC:C3A in EGM-2, an endothelial medium, was essential to support both cell types, and that co-cultures maintained the initial cell seeding ratio of 1:1 (HUVEC:C3A) after 3 days. Phenotyping of co-cultured cells using platelet endothelial cell adhesion molecule (PECAM-1/CD31) for HUVECs, and hepatic epithelial (EpCAM) markers for C3As demonstrated that at ratio 1:1 (HUVEC:C3A), there is cross-talk between HUVECs and C3As and cells in co-culture showed properties of self-organisation. This interaction resulted in improved hepatic metabolic activity in vitro in respect of albumin synthesis and cytochrome P450 activity. Treatment with low (5 mM), intermediate (10 mM) and high doses (20 mM) of APAP, showed that prediction of hepatotoxicity using specific kits for cell viability and mitochondria function, was significantly improved in C3As in the presence of HUVECs, thus demonstrating an in vitro human hepatic co-culture could be an invaluable model for drug toxicity studies. We observed that the intermediate APAP dose had no effect on cell viability and mitochondrial function in co-cultures, whilst by comparison both lactate levels and oxidative stress were perturbed in mono-cultures. Co-cultures also up-regulated expression of vascular endothelial growth factor receptor-2 (VEGFR-2) in HUVECs following APAP exposure, which may be important in modulating the toxic effect of APAP on C3As. To further improve the in vitro liver-like model, Matrigel™ was incorporated to promote vascular formation by HUVECs and support hepatic organization, migration and function of C3As. In HUVEC mono-cultures, Matrigel™-promoted vascularization, haptotaxis and self-organization and in HUVEC:C3A co-cultures formation of structures reminiscent of liver sinusoids and maintenance of hepatic albumin synthesis and CYP3A4 activity. Time-lapse imaging showed haptotactic migration of hepatocytes towards endothelial cells, with Matrigel™ likely having a chemotactic effect on HUVECs and C3As, resulting in interconnected vascular network. APAP inhibited angiogenesis in HUVEC mono-cultures whereas APAP had no effect in HUVEC:C3A co-cultures. In conclusion, the development of an in vitro human organotypic co-culture model of HUVECs and C3As significantly enhanced hepatic function, demonstrated by significant improvement in hepatic metabolism, evidence of greater resistance to APAP toxicity, and improved cell-cell communication. Co-cultures markedly modulated APAP hepatotoxicity compared with C3A mono-cultures. Furthermore, co-culture of HUVECs and C3As using a complex basement membrane biomatrix (Matrigel™) produced a self-assembling interconnected vascular network, improved hepatocyte function as well as reproducibility of responses to APAP toxicity. The application of the described co-culture models may improve the accuracy, efficacy and predictive power of drug toxicity testing strategies in drug development.