PHEX est une protéine importante dans le processus de minéralisation osseuse. Des mutations ou la délétion d’une partie de ce gène causent l’hypophosphatémie liée au chromosome X (XLH). Cette maladie est caractérisée par une hypophosphatémie, accompagnée de défauts de minéralisation, de rachitisme et de lésions ostéomalaciques. Avec l’hypophosphatémie, les taux circulants de vitamine D devraient être augmentés, ce qui n’est pas le cas d’où une régulation anormale de la production de vitamine D a lieu. Cependant, malgré le fait que cette protéine soit une peptidase, aucun substrat physiologique n’a encore été répertorié pour PHEX. PHEX est une protéine membranaire de type II de la famille M13 des métalloendopeptidases à zinc possédant un court domaine N-terminal cytosolique, un segment transmembrannaire d’environ 20 acides aminés et une large portion C-terminale extracellulaire où se trouve le site actif de l’enzyme. PHEX est exprimée de façon majoritaire dans les os et dans les dents et elle apparaît à l’initiation de la minéralisation. Les patients souffrant de XLH et la souris Hyp, qui est un modèle animal de la maladie humaine, montrent des quantités importantes de la protéine FGF23. De plus, FGF23 est impliqué dans une autre maladie reliée au métabolisme du phosphate, l’hypophosphatémie rachitique autosomale dominante (ADHR) où des mutations de FGF23 causent sensiblement les mêmes symptômes que XLH. FGF23 est produit principalement par les ostéoblastes et les ostéocytes. FGF23 cause une hypophosphatémie par la diminution de l’expression du cotransporteur NaPi de type II, responsable de la réabsorption du phosphate rénal. L’hypothèse proposée dans la littérature serait que PHEX activerait ou inactiverait des peptides importants pour la minéralisation osseuse. Plus spécifiquement, l’activation ou l’inactivation de ces peptides aurait pour rôle de réguler les quantités de FGF23. Selon l’hypothèse mentionnée précédemment, la régulation de PHEX pourrait donc avoir un effet sur la minéralisation. Une quantité croissante de données sur la régulation de PHEX sont maintenant disponibles. Par exemple, la vitamine D diminue l’expression de PHEX tandis que les glucocorticoïdes et l’hormone de croissance augmentent son expression. Dans une première étude, nous avons voulu déterminer si un peptide relié à la minéralisation osseuse, le PTHrP1-34, pouvait réguler l’expression de PHEX. Nous avons déterminé que le PTHrP1-34 peut réguler de façon négative l’expression de PHEX dans les cellules UMR-106, une lignée cellulaire ostéoblastique. Cette régulation passe par la voie de l’AMPc/protéine kinase A. De plus, cette diminution d’expression est également observée au jour 7 dans des cultures primaires d’ostéoblastes de rat en minéralisation. Par la suite, nous avons étudié un mutant de PHEX, le mutant E4Q retrouvé chez un patient souffrant de XLH, où la mutation se retrouve dans le domaine cytosolique de PHEX. Cette mutation n’interfère pas avec le site catalytique de l’enzyme puisque ce mutant de PHEX peut tout aussi bien cliver un substrat synthétique que la protéine sauvage. Il a été déterminé que cette mutation annule un motif di-acide. Nous avons démontré que ce motif di-acide est responsable de la liaison de PHEX à COPII, responsable de la formation de vésicules de sécrétion. De plus, il semblerait que ce motif soit important, probablement par son interaction avec COPII, à l’incorporation de PHEX dans des vésicules de calcification, lesdites vésicules étant importantes dans le processus de minéralisation. Finalement, des essais de compétitions ont démontré que la minéralisation pouvait être perturbée lorsque l’on surexprimait la queue cytosolique sauvage de PHEX, contrairement à la queue mutée. Ceci suggère possiblement que l’interaction avec COPII menant à l’incorporation de PHEX dans les vésicules de calcification ou d’autres protéines comprenant de tels motifs pourrait être importante pour la minéralisation. Finalement, la dernière étude porte sur la protéine FGF23. Nous avons démontré, par la surexpression de FGF23 dans la lignée MC3T3 d’ostéoblastes de souris, que cette surexpression a un effet sur la sénescence de ces cellules. En effet, des essais de sénescence ont montré l’augmentation de celle-ci lorsque FGF23 est surexprimé. Par contre, la prolifération n’est pas altérée. De plus, il semblerait que la différenciation soit plus rapide, tel qu’observé par une minéralisation survenant plus tôt, mais n’étant pas plus importante. Bref, la surexpression de FGF23 semblerait faire en sorte que les ostéoblastes se différencient plus rapidement et passent donc à un état de sénescence prématuré comparativement aux cellules sauvages. Ceci est en accord avec la littérature où KLOTHO, un cofacteur de FGF23 permettant sa liaison avec une plus grande affinité sur son récepteur, lorsqu’inactivé démontre un phénotype similaire au vieillissement incluant un phénotype de sénescence. / PHEX is an important protein in the process of osseous mineralisation. Mutations or deletions of a part of the PHEX gene cause X-linked hypophosphatemia (XLH). This disease is characterized by hypophosphatemia, accompanied by defects of bone mineralisation, rickets and osteomalacia. With the hypophosphatemia, the circulating levels of vitamin D should be increased, which is not the case where an abnormal regulation of the production of vitamin D takes place. However, in spite of the fact that this protein is a peptidase, no physiological substrate has been identified. PHEX is a membrane type II integral protein member of the M13 family of zinc metalloendopeptidasee. These proteins have a short N-terminal cytosolic domain, a transmembrane domain of approximately 20 amino acids and a large extracellular C-terminal portion where the active site of the enzyme is located. PHEX is expressed predominantly in bones and teeth in osteoblasts and odontoblasts, respectively. PHEX is expressed at initiation of mineralization. Patients suffering from XLH and the Hyp mouse, which has been used widely as an animal model of the human disease, show large quantities of the FGF23 protein. Moreover, FGF23 is implicated in another disease connected to phosphate metabolism, the autosomal dominant hypophosphatemic rickets (ADHR) where activating mutations in FGF23 cause roughly the same symptoms as XLH. FGF23 is produced mainly by osteoblasts and osteocytes. FGF23 causes hypophosphatemia by decreasing the expression of the type II sodium phosphate cotransportor, partly responsible for renal phosphate reabsorption. The hypothesis suggested in the literature would be that PHEX would activate or inactivate important peptides for osseous mineralisation. More specifically, the activation or the inactivation of these peptides would have a role in the control of FGF23 expression. According to the assumption mentioned previously, the regulation of PHEX could thus have an effect on mineralization. An increasing quantity of data on the regulation of PHEX is now available. For example, vitamin D decreases the expression of PHEX while glucocorticoids and growth hormone increase its expression. In a first study, we examined the possibility that a peptide connected to osseous mineralization could control the expression of PHEX. We determined that PTHrP1-34 can control in a negative way the expression of PHEX in UMR-106 cells, a cell line of osteoblastic origin. This regulation involves the cAMP/protein kinase A pathway. Moreover, this decrease in PHEX expression is also observed at day 7 in primary cultures of mineralizing rat osteoblasts. Next, we looked more closely at PHEX cellular localization. We used a mutant of PHEX, mutant E4Q identified in an XLH patient, where the mutated amino acid is found in the cytosolic domain of PHEX. This change does not interfere with the catalytic site of the enzyme since this PHEX mutant can still cleave a synthetic substrate as well as wildtype protein. This mutation disrupts a di-acidic motif present in the cytosolic domain of PHEX. We showed that this di-acidic motif is reponsible for the interaction of PHEX with COPII, a protein complex involved in the formation of secretion vesicles. Moreover, it would seem that this di-acidic motif is important, probably by its interaction with COPII, to the incorporation of PHEX in matrix vesicles, which are important in the mineralization process. Finally, competition assays showed that mineralization could be disturbed when the wildtype PHEX cytosolic tail is overexpressed, as opposed with the mutated cytosolic tail. This suggests that the interaction with COPII and the subsequent incorporation of PHEX in matrix vesicles or other proteins that possesses this motif could be important for mineralization. Finally, the last study examined the role of FGF23 on mineralization. We showed, by the overexpression of FGF23 in the mouse MC3T3 osteoblast cell line, that FGF23 can cause senescence of these cells. On the other hand, proliferation is not affected. Moreover, differentiation seems to occur at a faster rate, as indicated by earlier mineralization. Overexpression of FGF23 would accelerate differentiation and induce senescence. This is in agreement with the literature where KLOTHO, a FGF23 cofactor that increase the affinity of FGF23 for its receptor, when inactivated, shows a similar phenotype that includes senescence and aging.

Two laboratory incubation studies and a growth room bioassay of forage barley were conducted to investigate nitrogen (N) and phosphorus (P) mineralization, and nitrous oxide emission from two contrasting agricultural soils amended with anaerobically digested cattle manure (ADM). The ADM is a nutrient-rich co-product from manure-based biogas plants which is applied to cropland at rates used for raw manure since scientific information on nutrient release from ADM is lacking. Application of the separated solids fraction of ADM (SS) reduced nitrous oxide emission but resulted in lower N mineralization compared to raw manure in both soils. Raw manure- and SS- treatments had similar biomass yields and P supply capacities while the application of pelletized SS (PSS) caused net N immobilization, lower P release than manure and SS, and depressed barley yields relative to non-amended (control) soils.

Organic corn (Zea mays L.) producers generally use intensive tillage for weed control. No-till methods reduce soil erosion, conserve water, maintain soil structure and reduce CO2 emissions. The objective of this study was test different cover crops, tillage systems, N sources and N rates for organic corn production. Two tillage systems (no-till and moldboard plow), two cover crops [hairy vetch (Vicia villosa) and rye (Secale cereale)] and two organic N sources [Louisville Green (LG) and Nature Safe (NF)] at four N rates (45, 90, 135, 180 kg N ha-1) were evaluated during 2008 and 2009 at three sites. A roller crimper device was used for the no-till operations. A long term aerobic incubation was conducted. Hairy vetch improved yield, ear leaf N and grain N content compared with rye in all sites. Nature Safe increased ear leaf N more than LG in all three sites and yield in two out of three sites. Both sources stopped mineralizing at 28 days after application. Inorganic N production was about 50 kg N ha-1 for LG and 60 kg N ha-1 for NF. The combination moldboard plow and hairy vetch resulted in the highest yields at all experimental sites.

Tests were conducted for 71 pesticides in weekly bulk (wet + dry) deposition samples collected from May 25 to September 21 over two years at two sites in the City of Winnipeg, Canada. Twenty-one pesticides and their metabolites were detected in this study and 99% of samples collected contained mixtures of two or more pesticides. Malathion and glyphosate were the largest contributors to bulk deposition in 2010 and 2011, respectively. A second study examined the mineralization of 2,4-D and 17β-estradiol using a novel in-field soil microcosm study and a series of laboratory experiments under different temperature incubations. Results indicated that temperature fluctuations do not greatly affect the amount or rate of mineralization relative to the traditionally constant laboratory incubations of 20°C; however long-term freezing of soil reduced potential mineralization over time. This research advances scientific knowledge of agri-chemical fate and provides data for strengthening current environmental policy analysis in Canada.

Steroidal estrogens and antibiotics used in veterinary and human medicine are detected in livestock manure or sewage sludge and biosolids. Biodegradation is an important process by which estrogenic compounds are removed from organic amendments, but antibiotics have been shown to impede microbial communities. Although both compounds are often present in these media, the fate of estrogens in association with antibiotics has not been previously studied. In this study, both rates of tetracycline (40 and 200 mg kg-1) in liquid swine manure induced a lag phase of 40 to 50 days prior to the onset of a log phase of estrone and 17 β-estradiol mineralization, and tetracycline at 200 mg kg-1 significantly reduced maximum mineralization of estrone and 17 β-estradiol in manure. In soils amended with a high rate of manure, penicillin at 200 mg kg1 also significantly decreased maximum mineralization of estrone and 17 β-estradiol relative to soils free of antibiotics. Estrogen mineralization almost always significantly decreased in the order of: manure > soil amended with a low rate of manure = soil > soil amended with a high rate of manure. In order to examine the relationship between physical and chemical parameters of media and estrogen mineralization, sewage sludge and biosolid samples with vastly different characteristics were selected for a study of 17 β-estradiol and 17 α-ethinylestradiol mineralization in the presence of ciprofloxacin, an antibiotic commonly used to treat urinary and intestinal infections in humans. Ciprofloxacin was persistent in all media, as less than 0.05% mineralization was observed over 133 d. Despite this persistence, no significant effect of ciprofloxacin addition on 17 β-estradiol or 17 α-ethinylestradiol mineralization was observed at 133 days. Consistent with its chemical structure, maximum mineralization of 17 α-ethinylestradiol was always less than that of 17 β-estradiol, indicating resistance to microbial degradation. PCA analysis indicated that total nitrogen, ammonium-nitrogen and total carbon demonstrated a positive association with respiration and maximum mineralization of 17 β-estradiol, but a negative association with 17 α-ethinylestradiol maximum mineralization. Sorption of 17 α-ethinylestradiol was greater than 17 β-estradiol in all media, limiting maximum mineralization of 17 α-ethinylestradiol.

The Skellefte ore district in northern Sweden is a Palaeoproterozoic volcanic arc and one of the most important ones hosting volcanogenic massive sulfide (VMS) deposits, producing mainly base metals and orogenic gold deposits. Due to high metal prices and increased difficulties in finding shallow deposits, the exploration for and exploitation of mineral resources is quickly being moved to greater depths. For this reason, a better understanding of the geological structures in 3D down to a few kilometers depth is required as a tool for ore targeting. As exploration and mining go deeper, it becomes more and more evident why a good understanding of geology in 3D at exploration depths, and even greater, is important to optimize both exploration and mining. Following a successful pilot 3D geological modeling project in the western part of the district, the Kristineberg mining area, a new project "VINNOVA 4D modeling of the Skellefte district" was launched in 2008, with the aim of improving the existing models, especially at shallow depth and extending the models to the central district. More than 100 km of reflection seismic (crooked) profiles were acquired, processed and interpreted in conjunction with geological observations and potential field data. Results were used to constrain the 3D geological model of the study area and provided new insights about the geology and mineral potential at depth. Results along the seismic profiles in the Kristineberg mining area proved the capability of the method for imaging reflections associated with mineralization zones in the area, and we could suggest that the Kristineberg mineralization and associated structures dip to the south down to at least a depth of about 2 km. In the central Skellefte area, we were able to correlate main reflections and diffractions with the major faults and shear zones. Cross-dip analysis, reflection modeling, pre-stack time migration, swath 3D processing and finite-difference seismic modeling allowed insights about the origin of some of the observed reflections and in defining the imaging challenges in the associated geological environments. / VINNOVA 4D modeling of the Skellefte district

Tests were conducted for 71 pesticides in weekly bulk (wet + dry) deposition samples collected from May 25 to September 21 over two years at two sites in the City of Winnipeg, Canada. Twenty-one pesticides and their metabolites were detected in this study and 99% of samples collected contained mixtures of two or more pesticides. Malathion and glyphosate were the largest contributors to bulk deposition in 2010 and 2011, respectively. A second study examined the mineralization of 2,4-D and 17β-estradiol using a novel in-field soil microcosm study and a series of laboratory experiments under different temperature incubations. Results indicated that temperature fluctuations do not greatly affect the amount or rate of mineralization relative to the traditionally constant laboratory incubations of 20°C; however long-term freezing of soil reduced potential mineralization over time. This research advances scientific knowledge of agri-chemical fate and provides data for strengthening current environmental policy analysis in Canada.

Two laboratory incubation studies and a growth room bioassay of forage barley were conducted to investigate nitrogen (N) and phosphorus (P) mineralization, and nitrous oxide emission from two contrasting agricultural soils amended with anaerobically digested cattle manure (ADM). The ADM is a nutrient-rich co-product from manure-based biogas plants which is applied to cropland at rates used for raw manure since scientific information on nutrient release from ADM is lacking. Application of the separated solids fraction of ADM (SS) reduced nitrous oxide emission but resulted in lower N mineralization compared to raw manure in both soils. Raw manure- and SS- treatments had similar biomass yields and P supply capacities while the application of pelletized SS (PSS) caused net N immobilization, lower P release than manure and SS, and depressed barley yields relative to non-amended (control) soils.

Despite the importance of soil organic matter (SOM) in C storage and provision of ecosystem services, the magnitude and direction of the response of SOM to climate change remains debated. Particularly contested is the role of biochemical recalcitrance in determining the biological stability of SOM, which in turn, may also vary with climate. Employing a climosequence study design controlling for confounding pedogenic factors, the research described in this thesis aimed to uncover the response of both SOM chemistry and SOM biological stability to changes in climate and associated land use shifts at the grassland-forest ecotone in west-central Saskatchewan. Characterization of SOM chemistry was achieved using two advanced analytical techniques: X-ray absorption near edge structure (XANES) spectroscopy and pyrolysis-field ionization mass spectrometry (Py-FIMS). Agreements between XANES and Py-FIMS revealed only minor differences in SOM chemistry resulting from a 0.7 °C mean annual temperature (MAT) gradient and associated broad differences in land use, but revealed a clear influence of depth within soil profiles. In contrast, long-term aerobic incubations revealed that biological stability of SOM varied with both climate and climate-induced differences in land use, but was not largely influenced by depth. Together, these findings suggest a decoupling of SOM chemistry and its biological stability, indicating that factors other than biochemical recalcitrance are the primary drivers of SOM persistence in these soils.

Diss. (sammanfattning). Uppsala : Sveriges lantbruksuniv., 2003. / Härtill 3 uppsatser.