Thesis--Frankfurt a. M. / Vita. Includes bibliographical references (p. 210-214).

The author's thesis, Louvain. / "Table des ouvrages le plus fréquemment cités": p. [xxvi]-xxviii.

Pharmaceuticals are environmental contaminants causing steadily increasing concern due to their high usage, ubiquitous distribution in the aquatic environment, and potential to exert adverse effects on the ecosystems. After being discharged from wastewater treatment plants (WWTPs), pharmaceuticals can undergo transformation processes in surface waters, of which microbial degradation in river sediments is considered highly significant. In spite of a substantial number of studies on the occurrence of pharmaceuticals in aquatic systems, a comprehensive understanding of their environmental fate is still limited. First of all, very few consistent datasets from lab-based experiments to field studies exist to allow for a straightforward comparison of observations. Secondly, data on the identity and occurrence of transformation products (TPs) is insufficient and the relation of the behavior of TPs to that of their parent compounds (PCs) is poorly understood. In this thesis, these knowledge gaps were addressed by integrating the TP identification using suspect/non-target screening approaches and PC/TP fate determination. The overarching objective was to improve the understanding of the fate of pharmaceuticals in rivers, with a specific focus on water-sediment interactions, and formation and behavior of TPs. In paper I, 11 pharmaceutical TPs were identified in water-sediment incubation experiments using non-target screening. Bench-scale flume experiments were conducted in paper II to simultaneously investigate the behavior of PCs and TPs in both water and sediment compartments under more complex and realistic hydraulic conditions. The results illustrate that water-sediment interactions play a significant role for efficient attenuation of PCs, and demonstrate that TPs are formed in sediment and released back to surface water. In paper III the environmental behavior of PCs along stretches of four wastewater-impacted rivers was related to that of their TPs. The attenuation of PCs is highly compound and site specific. The highest attenuation rates of the PCs were observed in the river with the most efficient river water-pore water exchange. This research also indicates that WWTPs can be a major source of TPs to the receiving waters. In paper IV, suspect screening with a case-control concept was applied on water samples collected at both ends of the river stretches, which led to the identification of several key TPs formed along the stretches. The process-oriented strategies applied in this thesis provide a basis for prioritizing and identifying the critical PCs and TPs with respect to environmental relevance in future fate studies. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Submitted. Paper 4: Manuscript.</p>

Designed for the protection of major agricultural crops, neonicotinoids are the fastest-growing class of insecticides used against a broad spectrum of insect pests. Although neonicotinoid toxicity toward non-target organisms (e.g., bees, aquatic insects) has been well-studied, less is known about their distribution of use, transport, and fate in North American agroecosystems. This is especially true of neonicotinoid interactions with wetlands in the Canadian Prairies. Between 2009 and 2012, neonicotinoid use as a seed treatment increased by 30% across the Canadian Prairies. During spring 2012 to spring 2013, I sampled water and sediment from 136 wetlands situated in a range of crop types across central Saskatchewan to determine the extent of neonicotinoid contamination. Wetlands situated in oat, canola, and barley fields consistently contained higher neonicotinoid concentrations in water than in grasslands, but no single crop influenced overall detections. Neonicotinoid detections in water varied from 16% (fall 2012) to 91% (spring 2013) with peak concentrations up to 3110 ng/L found in summer. I found numerous detections of neonicotinoids in spring, after ice-off, but before seeding. Through sampling snow, snow meltwater, and soil particulates from previously treated (clothianidin) and untreated fields, meltwater showed the strongest relationship to initial spring concentrations in wetland water. Neonicotinoid concentrations increased with time in shallow temporary wetlands which appeared most at risk for annual contamination. While snowmelt contamination influenced water concentrations in spring, peak concentrations in wetlands were consistently found during summer sampling completed in 2012-2014. Rapid wetland assessments completed on 238 wetlands (summer of 2012 and 2013) revealed key ecological, hydrological and landscape features that influenced neonicotinoid detections and peak concentrations in Prairie wetlands. The results of my exploratory analysis indicated that plant community composition is a key indicator and/or driver of both detection and concentration of neonicotinoids in Prairie wetlands. In particular, specific shallow marsh plants were commonly associated with either higher (e.g., Scirpus validus) or lower (e.g., Mentha arvensis) neonicotinoid concentrations in natural wetlands suggesting wetland macrophytes in this zone may be either indicators of agricultural disturbance intensity or differentially capable of accumulating the insecticide in its tissue. Therefore, in 2014, I conducted an outdoor microcosm experiment to evaluate thiamethoxam uptake from water by Typha latifolia and Alisma triviale using two concentrations over a 7-day period. Experimental results found some trace positive detections but no quantifiable accumulation of the insecticide in plant tissues. This is despite the fact that results of my 2015 field study found species of Typha, Alisma and Equisetum had neonicotinoids more frequently detected in their tissues, at concentrations ranging from 1.01-8.44 ug/kg. My findings demonstrate that neonicotinoid distribution and fate in Canadian Prairie agroecosystems is driven by interactions between ecological, hydrological, and landscape characteristics. Consequently, these drivers regulate neonicotinoid exposure and persistence in ecologically important regional wetlands. In order to effectively conserve these critical waterbodies, conservation planning should consider the importance of maintaining naturally diverse vegetation zones to mitigate insecticide exposure to wetland-dependant organisms.

abstract: In this work, the vapor transport and aerobic bio-attenuation of compounds from a multi-component petroleum vapor mixture were studied for six idealized lithologies in 1.8-m tall laboratory soil columns. Columns representing different geological settings were prepared using 20-40 mesh sand (medium-grained) and 16-minus mesh crushed granite (fine-grained). The contaminant vapor source was a liquid composed of twelve petroleum hydrocarbons common in weathered gasoline. It was placed in a chamber at the bottom of each column and the vapors diffused upward through the soil to the top where they were swept away with humidified gas. The experiment was conducted in three phases: i) nitrogen sweep gas; ii) air sweep gas; iii) vapor source concentrations decreased by ten times from the original concentrations and under air sweep gas. Oxygen, carbon dioxide and hydrocarbon concentrations were monitored over time. The data allowed determination of times to reach steady conditions, effluent mass emissions and concentration profiles. Times to reach near-steady conditions were consistent with theory and chemical-specific properties. First-order degradation rates were highest for straight-chain alkanes and aromatic hydrocarbons. Normalized effluent mass emissions were lower for lower source concentration and aerobic conditions. At the end of the study, soil core samples were taken every 6 in. Soil moisture content analyses showed that water had redistributed in the soil during the experiment. The soil at the bottom of the columns generally had higher moisture contents than initial values, and soil at the top had lower moisture contents. Profiles of the number of colony forming units of hydrocarbon-utilizing bacteria/g-soil indicated that the highest concentrations of degraders were located at the vertical intervals where maximum degradation activity was suggested by CO2 profiles. Finally, the near-steady conditions of each phase of the study were simulated using a three-dimensional transient numerical model. The model was fit to the Phase I data by adjusting soil properties, and then fit to Phase III data to obtain compound-specific first-order biodegradation rate constants ranging from 0.0 to 5.7x103 d-1. / Dissertation/Thesis / Ph.D. Civil and Environmental Engineering 2012

The risk associated with the application and co-occurrence of atrazine and sulfentrazone, two herbicides applied to a corn and soybean rotational field, was evaluated in the current study. Peak field concentrations were found in the soil matrix, with atrazine and sulfentrazone values of 144 ng/g dry weight (dw), and 318 ng/g dw, respectively; however, due to the physicochemical properties of the compounds, the two herbicides were also transported to field water matrices. The highest mean runoff water concentrations for atrazine and sulfentrazone were 4.72 µg/L and 10.3 µg/L, respectively. A direct spray event of atrazine to the runoff water sampler caused concentrations as high as 1.6 mg/L, effectively becoming a worst case scenario concentration. Individual and mixture laboratory bioassays were also conducted to determine the effects of atrazine and sulfentrazone on the survival of D. magna, and P. promelas. Sub-lethal effects including germination of L. sativa, and growth of P. promelas, S. capricornutum and L. minor were also evaluated. Results showed that S. capricornutum and L. minor were the most susceptible non-target species tested, and synergistic effects were observed for both species when equipotent mixtures were tested. Margin of safety of 10% (MOS10) values were calculated for each species using field concentrations and bioassay benchmark concentrations. Atrazine MOS10 values, calculated with environmental concentrations not including the direct spray event, were 0.83 and 0.10 for S. capricornutum and L. minor, respectively. The MOS10 value for sulfentrazone effects on S. capricornutum was 0.31, and effects on L. minor was 1.39. There was a slight risk to S. capricornutum and L. minor growth associated with exposure to atrazine and sulfentrazone in an agricultural field. Although the co-occurrence of atrazine and sulfentrazone was observed, and synergistic effects were observed in the equipotent binary mixture bioassays for S. capricornutum and L. minor, it is believed that there is minimal increase in risk potential due to the co-occurrence, because field concentrations do not proportionally mimic the concentrations that produced synergism in the plant species.

Neurons in the central nervous system are typically not replaced and must therefore maintain their choice of fate and their synaptic connections throughout the life of an organism. I have used Drosophila genetics to analyze genes that prevent neurons from switching fates and allow them to form synapses onto target neurons. The Drosophila fly eye is composed of approximately 750 ommatidia, each comprising eight photoreceptor neurons (R1-R8) surrounded by non-neuronal accessory cells. These photoreceptor neurons undergo a well-defined developmental specification process and form synapses at defined locations in the brain. I have taken advantage of this system to investigate two questions: 1) how do neurons maintain their fate after specification? and 2) how do neurons form stable synapses? For the first half of my dissertation, I have focused my research on a gene, Sce, that I have shown is essential to prevent R7 neurons from undergoing a late switch in cell fate. Sce is an integral component of the Polycomb Group (PcG) complex that is essential for maintaining repression of multiple genes throughout the genome. I found that PcGs are required to prevent R7s from derepression of the R8-specific transcription factor Senseless. For the second half of my dissertation, I focused on the gene syd-1 that was identified to be required for proper presynaptic formation of R7 neurons. Previous studies in Caenorhabditis elegans suggested that Syd-1 acts upstream of Liprin-α and that Liprin-α promotes presynaptic development by binding the kinesin Kif1a to promote axon transport. I used live image analysis to show that, unlike Liprin-α, Syd-1 is not necessary to promote axon transport. Instead, we show that in R7s, Syd-1 acts upstream of Trio, and our results suggest that Syd-1's function is to promote Trio activity. This dissertation includes both my previously published and co-authored materials. / 10000-01-01

The adoption and subsequent retention of distinct cellular fates upon cell division is a critical phenomenon in the development of multicellular organisms. A well-studied example of this process is stem cell divisions; stem cells must possess the capacity to self-renew in order to maintain a stem cell population, as well as to generate differentiated daughters for tissue growth and repair. Drosophila neuroblasts are the neural stem cells of the central nervous system and have emerged as an important model for stem cell divisions and the genetic control of daughter cell identities. Neuroblasts divide asymmetrically to generate daughters with distinct fates; one retains a neuroblast identity and the other, a ganglion mother cell, divides only once more to generate differentiated neurons and glia. Perturbing the asymmetry of neuroblast divisions can result in the failure to self-renew and the loss of the neural stem cell population; alternatively, ectopic self-renewal can occur, resulting in excessive neuroblast proliferation and tumorigenesis. Several genetic lesions have been characterized which cause extensive ectopic self-renewal, resulting in brains composed of neuroblasts at the expense of differentiated cells. This contrasts with wild type brains, which are composed mostly of differentiated cells and only a small pool of neuroblasts. We made use of these mutants by performing a series of microarray experiments comparing mutant brains (consisting mostly of neuroblasts) to wild type brains (which are mostly neurons). Using this approach, we generated lists of over 1000 putatively neuroblast-expressed genes and over 1000 neuronal genes; in addition, we were able to compare the transcriptional output of different mutants to infer the neuroblast subtype specificity of some of the transcripts. Finally, we verified the self-renewal function of a subset of the neuroblast genes using an RNAi-based screen, resulting in the identification of 84 putative self-renewal regulators. We went on to show that one of these genes, midlife crisis (mammals: RNF113a), is a well-conserved RNA splicing regulator which is required in postmitotic neurons for the maintenance of their differentiated state. Our data suggest that the mammalian ortholog performs the same function, implicating RNF113a as an important regulator of neuronal differentiation in humans.

This dissertation explores the identity formation of Ethiopian and Nigerian immigrants, their second generation children, and native born African Americans who reside in the Seattle metropolitan area. Using boundary formation theory, I argue that African immigrants and their second generation children are developing a shared sense of Black identity and racial solidarity (linked fate) with native born African Americans. This shared Black identity is illustrated through both Africans and African Americans’ recognition of one another as racial group members, the constraints on their Black identities, and their navigation of similar institutional and political contexts. I argue that this is highly suggestive of an expansion of the Black racial boundary, and the reconstitution of Black identity in the post-Civil Rights Era. Despite some boundary contraction within the Black racial category by some 1st generation Africans, the African 1.5 and second generation are engaging in boundary crossing particularly with African Americans through their bicultural identities. This process appears to be leading to the blurring of boundaries between the children of African immigrants and native born African Americans, especially through the 1.5 and second generations involvement and integration into African American social and professional organizations. Evidence presented in this dissertation suggests that there is a weakening of ethnic identity among the African 1.5 and second generation. This weakening of ethnic identity among the children of Ethiopians and Nigerians suggest subsequent generations of Africans born here in the United States will eventually be absorbed into an undifferentiated African American/Black category. Keywords: Ethiopians, Nigerians, African Americans, linked fate, Black identity, Africans

Doctor of Philosophy / Division of Biology / Susan J. Brown / A segmented body plan is conserved in vertebrates and arthropods. Comparative studies implicate a conserved mode of A-P axis patterning and segmentation among vertebrates: Wnt signaling is involved in fate map patterning along the A-P axis and in segmentation in the posterior region of the embryo. On the other hand, comparative studies in arthropods have revealed distinct modes of development between long and short germ insects, which differ both morphologically and genetically. In the short germ insect Tribolium, a Wnt activity gradient contributes to A-P axis patterning and generates a posterior Tc-cad expression gradient that regulates segmentation through a pair-rule gene clock, forming segments sequentially as in vertebrates. In contrast, instead of Wnt activity, a hierarchy of regulatory genes regionalizes the blastoderm and defines segments simultaneously in the long germ insect Drosophila. In Tribolium, Tc-zen-1, Tc-otd-1 and Tc-cad play key roles in patterning serosa, head and trunk regions, respectively, of the blastoderm fate map, which are impacted by changes in Wnt activity levels. However, interactions between these genetic factors have not been described. My work revealed that cross talk between the Wnt and Dpp signaling pathways regulates the expression of Tc-zen-1 to determine the serosa. Furthermore, mutually repression between Tcotd-1 and Tc-cad defines the head and trunk regions while mutual repression between Tc-zen-1 and cad determines the posterior extent of the dorsal serosa. Analysis of target genes of the posterior Tc-cad gradient indicates that the Tc-cad gradient regulates the serial expression of gap genes, which are predominately regulators of Hox genes. Thus the posterior Tc-cad gradient determines segment formation through regulation of pair-rule genes in the insect segmentation clock, and defines segmental identity through regulation of gap genes. Given its effect on Tc-zen-1 and Tc-cad, the Wnt activity gradient is a key organizer of the Tribolium blastoderm fate map. Since homologs of these genes as well as the Wnt signaling pathway have also been identified in several other short germ band insects, and affect cell fates along the A-P body axis, this work provides a new paradigm for the short germ mode of development to guide studies in other arthropods.