Interaction between mercury and selenium has previously been observed both in man and in animals. The aim of this work was to study expressions of interaction between mercury and selenium in human K-562 cells. Inorganic and organic forms of mercury and selenium were used and cells were either pre-treated with selenium or simultaneously exposed to selenium and mercury. Concentrations of selenium and mercury chosen were indicated by a study of growth inhibition in the individual compounds: a low concentration of selenium and selenomethionine induced slight cell growth inhibition, while a high concentration resulted in a notable growth inhibition. Two mercury concentrations were chosen: one with minimal toxicity and another with high cell toxicity. In addition, uptake and retention patterns of selenomethionine and selenite differed in both selenocompounds. All simultaneous treatments with 3.5 μM methylmercury produced a reduction in cellular mercury with increased selenium concentration. This was particularly obvious in selenite treatments. Growth curves from the simultaneous 3.5 μM methylmercury and selenite treatments indicated protection with increased selenite concentrations. In both exposure protocols, the 5 μM methylmercury treatments were toxic to the cells. In both study protocols, cells exposed to selenite and mercuric chloride manifested increased cellular mercury uptake with increased selenium concentration. In all selenite and 35 μM mercuric chloride treatments, no inhibition of growth was observed, while the 50 μM mercuric chloride treatments were toxic to the cells. Selenite-dependent protection was achieved in both exposure protocols when considering the cellular uptake of mercury. With few exceptions, selenomethionine produced similar effects as selenite on mercuric chloride uptake and growth inhibition.

The use of nano- and micro-particulate carriers as delivery systems for oral vaccines has been under investigation for several decades. Surprisingly little is known of their uptake in the human intestine, despite the fact that substantial improvement is required to achieve adequate immune responses in man after oral administration. In this thesis, various aspects of particle transcytosis across the human intestinal epithelium were studied, in order to identify strategies for improved uptake of nano- and micro-particulate drug delivery systems. The follicle associated epithelium (FAE) overlying Peyer´s patches contains M-cells, which have an increased capacity for uptake of particulate antigens. Therefore, a model of human FAE was developed to study mechanisms of particle uptake and transport. Receptors that could be used for targeting to the FAE had previously not been identified in humans. By use of the model FAE, two new targets were identified on human intestinal FAE; CD9 and β1-integrin. Furthermore, studies of isolated human intestinal tissue showed that an integrin-adherent peptide motif, RGD, could be utilized to achieve selective and improved transport of nanoparticles into human Peyer´s patches. Studies of factors influencing intestinal particle uptake and transcytosis revealed that two cytokines, TNF-α and LTα1/β2, but also one growth factor, TGF-β1, induced uptake of particles in Caco-2 cells and transcytosis of particles in the model FAE. Furthermore, it was shown that an enteric bacterium, Yersinia Pseudotuberculosis, could trigger uptake and transcytosis of particles across model absorptive epithelial cells. In conclusion, this thesis provides a platform for further investigations of particle transcytosis across the human intestinal epithelium. The identification of two new proteins with increased expression in human FAE and a targeting sequence that improves particle uptake into Peyer’s patches, gives new hope for the development of subunit oral vaccines.

Metal contaminated stormwater, i.e. surface runoff in urban areas, can be treated in percolation systems, ponds, or wetlands to prevent the release of metals into receiving waters. Plants in such systems can, for example, attenuate water flow, bind sediment, and directly accumulate metals. By these actions plants affect metal mobility. This study aimed to examine the accumulation of Zn, Cu, Cd, and Pb in roots and shoots of plant species common in stormwater areas. Furthermore, submersed plants were used to examine the fate of metals: uptake, translocation, and leakage. Factors known to influence metal accumulation, such as metal ion competition, water salinity, and temperature, were also examined. The following plant species were collected in the field: terrestrial plants – Impatiens parviflora, Filipendula ulmaria, and Urtica dioica; emergent plants – Alisma-plantago aquatica, Juncus effusus, Lythrum salicaria, Sagittaria sagittifolia, and Phalaris arundinacea; free-floating plants – Lemna gibba and Lemna minor; and submersed plants – Elodea canadensis and Potamogeton natans. Furthermore, the two submersed plants, E. canadensis and P. natans, were used in climate chamber experiments to study the fate of the metals in the plant–water system. Emergent and terrestrial plant species accumulated high concentrations of metals in their roots under natural conditions but much less so in their shoots, and the accumulation increased further with increased external concentration. The submersed and free-floating species accumulated high levels of metals in both their roots and shoots. Metals accumulated in the shoots of E. canadensis and P. natans derived mostly from direct metal uptake from the water column. The accumulation of Zn, Cu, Cd, and Pb in submersed species was in general high, the highest concentrations being measured in the roots, followed by the leaves and stems, E. canadensis having higher accumulation capacity than P. natans. In E. canadensis the Cd uptake was passive, and the accumulation in dead plants exceeded the of living with time. The capacity to quickly accumulate Cd in the apoplast decreased with successive treatments. Some of the Cd accumulated was readily available for leakage. In P. natans, the presence of mixtures of metal ions, common in stormwater, did not alter the accumulation of the individual metals compared to when presented separately. It is therefore, proposed that the site of uptake is specific for each metal ion. In addition cell wall-bound fraction increased with increasing external concentration. Further, decreasing the temperature from 20ºC to 5ºC and increasing the salinity from 0‰ to 5‰ S reduced Zn and Cd uptake by a factor of two. In P. natans the metals were not translocated within the plant, while in E. canadensis Cd moved between roots and shoots. Thus, E. canadensis as opposed to P. natans may increase the dispersion of metals from sediment via acropetal translocation. The low basipetal translocation implies that neither E. canadensis nor P. natans will directly mediate the immobilisation of metal to the sediment via translocation. To conclude, emergent and terrestrial plant species seem to enhance metal stabilization in the soil/sediment. The submersed plants, when present, slightly increase the retention of metals via shoot accumulation.

This thesis reports on interactions between microgels and oppositely charged proteins. Two types of negatively charged microgels are investigated: poly(acrylic acid) microgels of 60-80 µm in diameter, and colloidal poly(NIPAM-co-acrylic acid) microgels of around 1 µm in diameter. The proteins used are lysozyme and cytochrome c, which both have positive net charge. The experimental techniques used in the studies of the larger microgels are mainly micromanipulator-assisted microscopy and confocal microscopy, while the smaller microgels are studied mainly with dynamic light scattering. It is observed that large amounts of protein are absorbed by the microgels, and that the uptake involves a substantial deswelling of the microgel. The uptake generally decreases as the ionic strength is increased, which is characteristic of electrostatic interactions. An ionic strength optimum is however observed in the case of lysozyme and poly(acrylic acid) microgels, where the highest uptake (10 gram lysozyme / gram microgel) is observed at ionic strength 40 mM. Cytochrome c uptake in poly(acrylic acid) microgels results in homogenous cytochrome c distribution throughout the microgel, whereas lysozyme uptake results in core-shell formation; the lysozyme concentration becomes much higher in the shell (outer part of the microgel) than in the core (inner part of the microgel). The shell constitutes a stress-bearing network which is sufficiently porous to allow protein diffusion through the shell. The different protein distributions are associated with different protein-protein interactions; strong protein-protein attraction promotes shell formation. In the case of colloidal microgels, lysozyme uptake decreases the electrophoretic mobility and the colloidal stability of the microgels. The microgels flocculate as the uptake reaches charge ratio 0.6-0.7 (positive lysozyme charges/negative microgel charges), largely independent of ionic strength. Initial experiments on the combination of cytochrome c and colloidal microgels show that colloidal stability is maintained at a range of conditions (ionic strength, protein concentration) where flocculation occurred in the case of lysozyme.

Sustainable polymeric materials put emphasis on mastering the whole life-cycle of polymeric materials. This includes the choice of raw materials, selection of synthesis and processing, environmental impact during long-term use followed by detailed knowledge about recycling and waste management.  Within this large efforts are put in the design and development of new biocomposites using renewable fibres instead of inert ones. The thesis deals with surface modifications of agricultural fibres and the design of biocomposites with optimal long-term properties balancing the potential risk for biodegradation.  The first part of this thesis involved surface modifications of oil palm fibres and production of biocomposites with PP as matrix. The chemical surface modifications of oil palm fibres explored propionylation, PPgMA grafting via solution modification and reactive blending and vinyltrimethoxy silanization as methods. All modified fibre/PP biocomposites showed improvements in the mechanical properties followed also by an improvement of water resistance. In comparison with unmodificed fibres/PP matrix the highest water resistance after the surface modifications of oil palm fibres were observed for silanization followed by PPgMA modified,  PPgMA blending and  propionylation. The second part aimed at producing fully biodegradable biocomposites and analysing the resulting properties with respect to potential risk for biodegradation. Sisal fibres were incorporated in PLA and PHBV and the resulting risk for biodegradation using a fungus, Aspergillus niger, monitored. Neat PLA and PHBV were compared with the corresponding biocomposites and already without fibres both polymers were notably biodegraded by Aspergillus niger. The degree of biodegradation of PLA and PHBV matrices was related to the extent of the growth on the material surfaces. Adding sisal fibres gave a substantial increase in the growth on the surfaces of the biocomposites. Correlating the type of surface modification of sisal fibres with degree of biodegradation, it was demonstrated that all chemically modified sisal/PLA biocomposites were less biodegraded than unmodified sisal biocomposites.  Propionylated sisal/PLA demonstrated the best resistance to biodegradation of all biocomposites while sisal/CA/PLA demonstrated high level of biodegradation after severe invasion by Aspergillus niger. In general, the biodegradation correlated strongly with the degree of water absorption and surface modifications that increase the hydrophobicity is a route to improve the resistance to biodegradation. Designing new biocomposites using renewable fibres and non-renewable and renewable matrices involve the balancing of the increase in mechanical properties, after improved adhesion between fibres and the polymer matrix, with the potential risk for biodegradation. / <p>QC 20130325</p>

Diagnosis of diabetes mellitus, presence of hyperglycemia, and/or insulin resistance confer cardiovascular risk, particularly for diastolic dysfunction. Diabetes is associated with elevated myocardial norepinephrine (NE) content, enhanced sympathetic nervous system (SNS) activity, altered resting heart rate, and depressed heart rate variability. Positron emission tomography (PET) using the NE analogue [11C]meta-hydroxyephedrine ([11C]HED) provides an index of myocardial sympathetic neuronal integrity at the NE reuptake transporter (NET). The hypothesis of this project is that (i) hyperglycemia imparts heightened sympathetic tone and NE release, leading to abnormal sympathetic neuronal function in the hearts of diabetic rats, and (ii) these abnormalities may be reversed or prevented by treatments to normalize glycemia. Sprague Dawley rats were rendered insulin resistant by high fat feeding and diabetic by a single dose of streptozotocin (STZ). Diabetic rats were treated for 8 weeks with insulin, metformin or rosiglitazone, starting from either 1 week (prevention) or 8 weeks (reversal) after STZ administration. Sympathetic neuronal integrity was evaluated longitudinally by [11C]HED PET. Echocardiography measures of systolic and diastolic function were completed at serial timepoints. Plasma NE levels were evaluated serially and expression of NET and β-adrenoceptors were tested at the terminal endpoints. Diabetic rats exhibited a 52-57% reduction of [11C]HED standardized uptake value (SUV) at 8 weeks after STZ, with a parallel 2.5-fold elevation of plasma NE and a 17-20% reduction in cardiac NET expression. These findings were confirmed by ex vivo biodistribution studies. Transmitral pulse wave Doppler echocardiography established an extension of mitral valve deceleration time and elevated early to atrial velocity ratio, suggesting diastolic dysfunction. Subsequent treatment with insulin but not metformin restored glycemia, reduced plasma NE by 50%, normalized NET expression, and recovered [11C]HED SUV towards non-diabetic age-matched control. Diastolic dysfunction in these rats persisted. By contrast, early treatment with insulin, metformin, or rosiglitazone delayed the progression of diastolic dysfunction, but had no effect on elevated NE and reduced [11C]HED SUV in diabetic rats, potentially owing to a latent decrease in blood glucose. In conclusion, diabetes is associated with heightened circulating and tissue NE levels which can be effectively reversed by lowering glycemia with insulin. Noninvasive interrogation of sympathetic neuronal integrity using [11C]HED PET may have added value in the stratification of cardiovascular risk among diabetic patients and in determining the myocardial effects of glycemic therapy.

Success of hybrid poplar plantations will rely on the efficient management of nutrients and weeds. Relatively little is known about the root uptake characteristics of hybrid poplar and weeds, their belowground interactions and particularly, the quantitative understanding of nutrient uptake using mechanistic models under weed-competing conditions. Therefore, the objectives of this study were to investigate the effects of dandelion and quackgrass on the growth of hybrid poplar, to establish their root uptake characteristics and to quantify their nutrient uptake using the soil supply and nutrient demand (SSAND) model. In a pot study, hybrid poplar stem height, root collar diameter, shoot and root biomass, root length, and N, P and K uptake significantly decreased in the presence of dandelion and quackgrass weeds. Similar weed competition effects on growth of hybrid poplar were also observed in the field at the Pasture and Alfalfa sites where hybrid poplar was grown with and without weeds for 50, 79 and 100 days. In a hydroponic experiment, Imax values for NH4-N, NO3-N, P and K varied significantly among hybrid poplar seedlings and dandelion and quackgrass weed species and was greatest for dandelion followed by hybrid poplar and then quackgrass. The Km values were lowest for quackgrass compared to the other plant species for all of the nutrients. Simulation results from the SSAND model for the pot study showed that N uptake was underpredicted in hybrid poplar by 58 to 73%, depending upon soil type and weed treatment. Incorporation of N mineralization as a model input improve the hybrid poplar N uptake predictions by 24 and 67% in the Pasture and Alfalfa soil, respectively, when grown without weeds. SSAND model underestimated P uptake by 84-89% and overestimated K uptake by 28 to 59% for hybrid poplar depending upon the soil type and weed treatment. In the field, N uptake by hybrid poplar was in close agreement to measured N uptake in the control treatment. N uptake was greatly underestimated for both hybrid poplar and weeds in the weed treatment. Including changing water content greatly improves the N uptake by hybrid poplar and weeds in weed treatments. Results from this study suggest weed control is an essential practice to establish successful hybrid poplar plantations. Also, SSAND model can be an effective tool for predicting the nutrient uptake under two plant species competing environment if all the processes of nutrient supply are adequately described in the model.

Uranium mining and milling operations at Key Lake, Saskatchewan, Canada, have been releasing effluent since 1983, resulting in the accumulation of selenium in surface water, sediment, and biota in downstream lakes relative to pre-development and reference lake conditions. Elevated selenium can pose a risk to fish and bird populations in aquatic ecosystems as a result of the trophic transfer of selenium from the base of the aquatic food web. This research program was designed to address specific knowledge gaps related to the bioaccumulation of selenium at the benthic-detrital link of aquatic food webs. To fulfill this objective, laboratory and in situ field experiments were conducted using the benthic invertebrate Chironomus dilutus to identify the exposure pathway(s) and selenium species associated with the bioaccumulation of selenium by benthic invertebrates downstream from the Key Lake operation. Laboratory bioaccumulation tests that exposed midge larvae to 4.3 µg/L as dissolved selenate for 10 d resulted in negligible accumulation of selenium. However, larvae rapidly accumulated selenium over 10 d of exposure to 3.8 and 1.8 µg/L selenite and seleno-DL-methionine (Se-met), respectively. Furthermore, once selenium was accumulated by the larvae from the selenite and Se-met treatments, the majority of it was retained after a 10 d depuration period in clean water. When additional midge larvae were exposed to selenium until emergence, selenium accumulated during the larval stage was passed onto the adults following metamorphosis, with only a small percentage of the selenium (< 5%) transferred to the exuvia. Selenium speciation analysis using X-ray absorption spectroscopy showed that increases in total selenium concentrations corresponded to increased fraction of organic selenides, modeled as selenomethionine, in C. dilutus larvae and adults. Results from the 2008 in situ caging study confirmed that surface water is not a significant selenium exposure pathway for benthic invertebrates at Key Lake. Chironomus dilutus larvae accumulated between 20- and 90-fold more selenium from exposure to sediment compared to exposure to surface water in the high exposure lake. In response to these findings, a second in situ experiment was conducted in 2009 to investigate the importance of dietary selenium (biofilm or detritus) vs. whole-sediment as an exposure pathway. Larvae exposed to sediment detritus (top 2 â 3 mm of sediment) from the exposure site had the highest selenium concentrations after 10 d of exposure (15.6 ± 1.9 µg/g) compared to larvae exposed to whole-sediment (12.9 ± 1.7 µg/g) or biofilm (9.9 ± 1.6 µg/g). Biofilm had lower total selenium concentrations than the detritus and whole-sediment fractions, but nearly 80% of the selenium was present as organic selenides similar to selenomethionine. Biofilms appear to be an enriched source of organic selenium and are important food items for many benthic consumers. Integrating the separate lines of evidence that were generated during laboratory and in situ bioaccumulation tests helped strengthen the understanding of selenium accumulation in the benthic-detrital food web and subsequent trophic transfer of selenium to benthic invertebrates.

There are no seeding rates established for organic production of field pea and lentil in Saskatchewan and organic producers must rely upon rates recommended for conventional production of these crops. These seeding rates may not be suitable for organic production as the two systems differ in the use of inputs and in pest management. The objectives of this study were to determine an optimal seeding rate for organic production of field pea and lentil in Saskatchewan considering a number of factors, including yield, weed suppression, soil nitrogen (N) and phosphorus (P) concentrations, soil water storage, colonization of crop roots by arbuscular mycorrhizal fungi (AMF), plant P uptake, and profitability. A field experiment was conducted to determine the optimal seeding rates of field pea and lentil. Field pea seeding rates were 10, 25, 62, 156 and 250 plants m-2 and lentil seeding rates were 15, 38, 94, 235 and 375 plants m-2. Sites were established at Vonda, Vanscoy and Delisle, SK using a randomized complete block designs with summerfallow and green manure treatments included for each crop. Seed yield increased with increasing seeding rate for both crops, up to 1725 kg ha-1 for field pea and 1290 kg ha-1 for lentil. Weed biomass at physiological maturity decreased with increasing seeding rate for both crops. In field pea, weeds were reduced in weight by 68%, while lentil reduced weed biomass by 59% between the lowest and highest seeding rates. <p>Post-harvest soil phosphate-P levels did not change consistently between treatments, indicating that there was no trend in soil P concentration with seeding rate. Post-harvest soil inorganic N, however, was higher for the summerfallow and green manure treatments than for the seeding rate treatments in both crops. Inorganic N was higher at some sites for the highest two seeding rates in field pea. Soil water storage following harvest was not affected by treatment.<p>Colonization of crop roots by AMF increased for lentil with increasing seeding rate, but the same trend was not observed in field pea. A growth chamber experiment to study the rate of colonization of field pea between 10 and 50 d after emergence did not show any differences in AMF colonization between seeding rates. Colonization levels were high (70 to 85%) for both crops in both the field and growth chamber. Arbuscular mycorrhizal fungi colonization and seeding rate had no effect on plant P concentration for either field pea or lentil. Both crops became increasingly profitable as seeding rate increased. Field pea reached a maximum return at 200 plants m-2 and lentil return increased to the highest seeding rate of 375 plants m-2. Organic farmers should increase seeding rates of these crops to increase returns and provide better weed suppression.

In durum wheat (<i>Triticum turgidum</i> L. var <i>durum</i>), grain protein concentration (GPC) and gluten quality are among the important factors influencing pasta-making quality. Semolina with high protein content produces pasta with increased tolerance to overcooking and greater cooked firmness. However, genetic improvement of GPC is difficult largely because of its negative correlation with grain yield, and a strong genotype x environment interaction. Therefore, identification of quantitative trait loci (QTL) for high GPC and the associated markers is a priority to enhance selection efficiency in breeding durum wheat for elevated GPC. At a physiological level, GPC is influenced by several factors including nitrogen remobilization from vegetative organs and direct post-anthesis nitrogen uptake (NUP) from the soil. Understanding the relationship between elevated GPC and nitrogen remobilization, and post-anthesis NUP will enable durum wheat breeders to develop varieties that not only produce high yield and high GPC, but also exhibit better nitrogen use efficiency. The objectives of this study were: (1) to identify and validate QTL for elevated GPC in two durum wheat populations; and (2) to determine if elevated GPC is due to more efficient nitrogen remobilization and/or greater post-anthesis NUP. A genetic map was constructed with SSR and DArT® markers in a doubled haploid population from the cross Strongfield x DT695, and GPC data were collected in replicated trials in six Canadian environments from 2002 to 2005. Two stable QTL for high GPC, QGpc.usw-B3 on chromosome 2B and QGpc.usw-A3 on 7A, were identified. Strongfield, the high GPC parent, contributed the alleles for elevated GPC at both QTL. These two QTL were not associated with variation in grain weight (seed size) or grain yield. QGpc.usw-A3 was validated in a second Strongfield-derived population as that QTL was significant in all six testing environments. Averaged over five locations, selection for QGpc.usw-A3 resulted in a +0.4% to +1.0% increase in GPC, with only small effects on yield in most environments. A physiological study of grain protein accumulation revealed that regardless of the growing condition, nitrogen remobilization was the major contributor for grain nitrogen in durum genotypes evaluated, accounting for an average of 84.3% of total GPC. This study confirmed that introgression of Gpc-B1 into Langdon resulted in increased GPC, and this GPC increase was due to higher N remobilization. Strongfield expressed greater N remobilization than DT695 and the semi-dwarf cultivar Commander, but N remobilization was not the determining factor for Strongfields elevated GPC. Strongfield expressed greater post-anthesis NUP than DT695. Similarly, a selection of six high-GPC doubled haploid (DH) lines from the cross DT695 x Strongfield expressed significantly greater post-anthesis NUP than six low-GPC DH selections, supporting the hypothesis that elevated GPC in Strongfield is derived from greater post-anthesis NUP. All six high-GPC DH selections carried the Strongfield allele at QGpc.usw-A3, suggesting this QTL maybe associated with post-anthesis NUP.