<p>Circulating immune complexes play an important role in the modulation of antibody responses and in the pathogenesis of immune diseases. This thesis deals with the <i>in vivo </i>regulatory properties of antibodies and their specific Fc receptors.</p><p>The immunosuppressive function of IgG is used clinically, to prevent rhesus-negative women from becoming sensitized to rhesus-positive erythrocytes from the fetus. The mechanism behind this regulation is poorly understood but involvement of a receptor for IgG, FcγRII, has been suggested. It is shown in this thesis that IgG and also IgE induce immunosuppression against sheep erythrocytes to a similar extent both in mice lacking all the known Fc receptors as in wild-type animals. These findings imply that antibody-mediated suppression of humoral responses against particulate antigens is Fc-independent and that the major operating mechanism is masking of epitopes.</p><p>Immunization with soluble antigens in complex with specific IgG leads to an augmentation of antibody production. The cellular mechanism behind this control is examined here and it is found that the capture of IgG2a immune complexes by a bone marrow-derived cell expressing FcγRI (and FcγRIII) is essential. An analysis of the ability of IgG3 to mediate this regulation indicated that, in contrast, this subclass of IgG augments antibody responses independently of FcγRI (and FcγRIII). These findings suggest that distinct mechanisms mediate the enhancing effect of different subclasses of antibodies.</p><p>Finally, the contribution of FcγRIII was studied in the development of collagen-induced arthritis (CIA), an animal model for rheumatoid arthritis in humans. It was discovered that while DBA/1 wild-type control mice frequently developed severe CIA, with high incidence, FcγRIII-deficient mice were almost completely protected, indicating a crucial role for FcγRIII in CIA.</p><p>The results presented here help to understand how immune complexes regulate immune responses <i>in vivo</i> and show that Fc receptors for IgG, if involved, could be new targets for the treatment of immune complex-related disorders.</p>

<p>The domestication of the pig began about 9 000 years ago and many of the existing domestic breeds have been selected for phenotypic traits like lean meat and fast growth. Domestic pigs are phenotypically very different from the ancestral wild boar that has adapted to survive in their natural environment. Because of their divergence, crosses between domestic pigs and wild boars are suitable for constructing genetic maps and Quantitative trait locus (QTL) analyses. A cross between the Large White and the European wild boar was thus initiated in the late 1980s. A major QTL for fat deposition and growth, denoted <i>FAT1</i>, was found on chromosome 4. The aim of this thesis was to further characterise the <i>FAT1</i> locus and to identify the causative gene(s) and mutation(s). We have identified new markers and constructed a high-resolution linkage and RH map of the <i>FAT1</i> QTL interval. We also performed comparative mapping to the human genome and showed that the pig chromosome 4 is homologous to human chromosomes 1 and 8. The gene order is very well conserved between the two species. In parallel we have narrowed down the <i>FAT1</i> QTL interval by repeated backcrossing to the domestic Large White breed for six generations. The QTL could be confirmed for fatness but not for growth. Furthermore, the data strongly suggested that there might be more than one gene underlying the <i>FAT1</i> QTL. Depending on which hypothesis to consider, the one- or two-loci model, the <i>FAT1</i> interval can be reduced to 3,3 or 20 centiMorgan (cM), respectively, based on the backcross experiments. In the last study we confirm the two-loci model with one locus primarily effecting abdominal fat and another locus primarily effecting subcutaneous fat. We have identified a missense mutation in the <i>RXRG</i> gene which is in strong association with the abdominal fat QTL and the mutation is a potential candidate for that locus.</p><p>Brown adipose tissue (BAT) is a specific type of fat essential for non-shivering thermogenesis in mammals. Piglets appear to lack BAT and rely on shivering as the main mechanism for thermoregulation. Uncoupling protein 1 (<i>UCP1</i>) gene is exclusively expressed in BAT and its physiological role is to generate heat by uncoupling oxidative phosphorylation. We show that the <i>UCP1</i> gene has been disrupted in the pig lineage about 20 years ago. The inactivation of <i>UCP1</i> provides a genetic explanation for the poor thermoregulation in piglets. </p>

Circulating immune complexes play an important role in the modulation of antibody responses and in the pathogenesis of immune diseases. This thesis deals with the in vivo regulatory properties of antibodies and their specific Fc receptors. The immunosuppressive function of IgG is used clinically, to prevent rhesus-negative women from becoming sensitized to rhesus-positive erythrocytes from the fetus. The mechanism behind this regulation is poorly understood but involvement of a receptor for IgG, FcγRII, has been suggested. It is shown in this thesis that IgG and also IgE induce immunosuppression against sheep erythrocytes to a similar extent both in mice lacking all the known Fc receptors as in wild-type animals. These findings imply that antibody-mediated suppression of humoral responses against particulate antigens is Fc-independent and that the major operating mechanism is masking of epitopes. Immunization with soluble antigens in complex with specific IgG leads to an augmentation of antibody production. The cellular mechanism behind this control is examined here and it is found that the capture of IgG2a immune complexes by a bone marrow-derived cell expressing FcγRI (and FcγRIII) is essential. An analysis of the ability of IgG3 to mediate this regulation indicated that, in contrast, this subclass of IgG augments antibody responses independently of FcγRI (and FcγRIII). These findings suggest that distinct mechanisms mediate the enhancing effect of different subclasses of antibodies. Finally, the contribution of FcγRIII was studied in the development of collagen-induced arthritis (CIA), an animal model for rheumatoid arthritis in humans. It was discovered that while DBA/1 wild-type control mice frequently developed severe CIA, with high incidence, FcγRIII-deficient mice were almost completely protected, indicating a crucial role for FcγRIII in CIA. The results presented here help to understand how immune complexes regulate immune responses in vivo and show that Fc receptors for IgG, if involved, could be new targets for the treatment of immune complex-related disorders.

The domestication of the pig began about 9 000 years ago and many of the existing domestic breeds have been selected for phenotypic traits like lean meat and fast growth. Domestic pigs are phenotypically very different from the ancestral wild boar that has adapted to survive in their natural environment. Because of their divergence, crosses between domestic pigs and wild boars are suitable for constructing genetic maps and Quantitative trait locus (QTL) analyses. A cross between the Large White and the European wild boar was thus initiated in the late 1980s. A major QTL for fat deposition and growth, denoted FAT1, was found on chromosome 4. The aim of this thesis was to further characterise the FAT1 locus and to identify the causative gene(s) and mutation(s). We have identified new markers and constructed a high-resolution linkage and RH map of the FAT1 QTL interval. We also performed comparative mapping to the human genome and showed that the pig chromosome 4 is homologous to human chromosomes 1 and 8. The gene order is very well conserved between the two species. In parallel we have narrowed down the FAT1 QTL interval by repeated backcrossing to the domestic Large White breed for six generations. The QTL could be confirmed for fatness but not for growth. Furthermore, the data strongly suggested that there might be more than one gene underlying the FAT1 QTL. Depending on which hypothesis to consider, the one- or two-loci model, the FAT1 interval can be reduced to 3,3 or 20 centiMorgan (cM), respectively, based on the backcross experiments. In the last study we confirm the two-loci model with one locus primarily effecting abdominal fat and another locus primarily effecting subcutaneous fat. We have identified a missense mutation in the RXRG gene which is in strong association with the abdominal fat QTL and the mutation is a potential candidate for that locus. Brown adipose tissue (BAT) is a specific type of fat essential for non-shivering thermogenesis in mammals. Piglets appear to lack BAT and rely on shivering as the main mechanism for thermoregulation. Uncoupling protein 1 (UCP1) gene is exclusively expressed in BAT and its physiological role is to generate heat by uncoupling oxidative phosphorylation. We show that the UCP1 gene has been disrupted in the pig lineage about 20 years ago. The inactivation of UCP1 provides a genetic explanation for the poor thermoregulation in piglets.

Heavy-duty trucks are in idle operation during long periods of time, providing the vehicles with electricity via the alternator at standstill. Idling trucks contribute to large amounts of emissions and high fuel consumption as a result of the low efficiency from fuel to electricity. Auxiliary power units, which operate independently of the main engine, are promising alternatives for supplying trucks with electricity. Fuel cell-based auxiliary power units could offer high efficiencies and low noise. The hydrogen required for the fuel cell could be generated in an onboard fuel reformer using the existing truck fuel. The work presented in this thesis concerns hydrogen generation from transportation fuels by autothermal reforming focusing on the application of fuel cell auxiliary power units. Diesel and dimethyl ether have been the fuels of main focus. The work includes reactor design aspects, preparation and testing of reforming catalysts including characterization studies and evaluation of operating conditions. The thesis is a summary of five scientific papers. Major issues for succeeding with diesel reforming are fuel injection, reactant mixing and achieving fuel cell quality reformate. The results obtained in this work contribute to the continued research and development of diesel reforming catalysts and processes. A diesel reformer, designed to generate hydrogen to feed a 5 kWe polymer electrolyte fuel cell has been evaluated for autothermal reforming of commercial diesel fuel. The operational results show the feasibility of the design to generate hydrogen-rich gases from complex diesel fuel mixtures and have, together with CFD calculations, been supportive in the development of a new improved reformer design. In addition to diesel, the reforming reactor design was shown to run satisfactorily with other hydrocarbon mixtures, such as gasoline and E85. Rh-based catalysts were used in the studies and exhibit high performance during diesel reforming without coke formation on the catalyst surface. An interesting finding is that the addition of Mn to Rh catalysts appears to improve activity during diesel reforming. Therefore, Mn could be considered to be used to decrease the noble metal loading, and thereby the cost, of diesel reforming catalysts. Dimethyl ether is a potential diesel fuel alternative and has lately been considered as hydrogen carrier for fuel cells in truck auxiliary power units. The studies related to dimethyl ether have been focused on the evaluation of Pd-based catalysts and the influence of operating parameters for autothermal reforming. PdZn-based catalysts were found to be very promising for DME reforming, generating product gases with high selectivity to hydrogen and carbon dioxide. The high product selectivity is correlated to PdZn interactions, leading to decreased activity of decomposition reactions. Auxiliary power systems fueled with DME could, therefore, make possible fuel processors with very low complexity compared to diesel-fueled systems. The work presented in this thesis has enhanced our understanding of diesel and DME reforming and will serve as basis for future studies. / QC 20100804

Cycling of the relative humidity (RH) levels in the reactant streams of polymer electrolyte membrane (PEM) fuel cells has been reported to decay fuel cell performance. This study focuses on the accelerated durability testing to examine different modes of membrane failure via RH cycling. A single PEM fuel cell with an active area of 42.25 cm2 was tested. A Greenlight G50 test station was used to establish baseline cell (Run 1) performance with 840 hours of degradation under high-humidity idle conditions at a constant current density of 10 mA cm-2. Under the same conditions, two other experiments were conducted by varying the RH. For the H2-air RH cycling test (Run 2), anode and cathode inlet gases were provided as dry and humidified gases. Another RH cycling experiment was the H2 RH cycling test (Run 3): the anode inlet gas was cycled whereas keeping the other side constantly at full humidification. These two RH cycling experiments were alternated in dry and 100% humidified conditions every 10 and 40 minutes, respectively. In the experiments, the fuel cells contained a GoreTM 57 catalyst coated membrane (CCM) and 35 BC SGL gas diffusion layers (GDLs). The fuel cell test station had been performed under idle conditions at a constant current density of 10 mA cm-2. Under the idle conditions, operating at very low current density, a low chemical degradation rate and minimal electrical load stress were anticipated. However, the membrane was expected to degrade due to additional stress from the membrane swelling/contraction cycle controlled by the RH. In this work the performance of the 100% RH humidified cell (Run 1) was compared with that of RH cycling cells (Run 2 and Run 3). Chemical and mechanical degradation of the membrane were investigated using in-situ and ex-situ diagnostic methods. The results of each measurement during and after fuel cell operation are consistent. They clearly show that changing in RH lead to an overall PEM fuel cell degradation due to the increase in membrane degradation rate from membrane resistance, fluoride ion release concentration, hydrogen crossover current, membrane thinning, and hot-spot/pin-hole formation.

A molecular-level understanding of a heterogeneous catalytic reaction is the key goal of heterogeneous catalysis. A surface science approach enables the realization of this goal. However, the working conditions (ultrahigh vacuum (UHV) conditions) of traditional surface science techniques restrict the investigations of heterogeneous catalysis system under industrial working conditions (atmospheric pressures). Polarization Modulation Infrared Reflection-Absorption Spectroscopy (PM-IRAS) can be operated in both UHV and atmospheric pressure conditions with a wide temperature span while providing high resolution (4 cm-1 is used in this dissertation) spectra. In this dissertation, PM-IRAS has been employed as a major technique to: 1) obtain both electronic and chemical information of catalysts from UHV to elevated pressure conditions; 2) explore reaction mechanisms by in situ monitoring surface species with concurrent kinetic measurements. In this dissertation, NO adsorption and dissociation on Rh(111) have been studied. Our PM-IRAS spectra show a transition of NO adsorption on three-fold hollow sites to atop sites occurs at low temperatures (<275 K). NO dissociation is found to account for this transition. The results indicated the dissociation of NO occurs well below the temperature previously reported. Characterizations of highly catalytically active Au films have also been carried out. Electronic and chemical properties of (1 x 1)- and (1 x 3)-Au/TiOx/Mo(112) films are investigated by PM-IRAS using CO as a probe molecule. The Au overlayers are found to be electron-rich and to have significantly different electronic properties compared with bulk Au. The exceptionally high catalytic activity of the Au bilayer structure is related to its unique electronic properties. CO oxidation reactions on Rh, Pd, and Pt single crystals are explored from low CO pressures under steady-state conditions (less than 1 x 10-4 Torr) to high pressures (0.01-10 Torr) at various gaseous reactant compositions. Surface CO species are probed with in situ PM-IRAS to elucidate the surface phases under reaction conditions. These experimental results are used to correlate reaction kinetics and surface reactant species. It is evident that there is a continuum over the pressure range studied with respect to the reaction mechanism. The most active phase has been shown to be an oxygen-dominant surface. The formation of a subsurface oxygen layer is found to deactivate the reaction.

In questa tesi vengono affrontati due diversi tipi di studio. Il primo tratta della costruzione di una mappa di ibridi bovino-criceto di radiazione di seconda generazione tramite la tipizzazione di un pannello RH, fornito dal Roslin Institut, con un set di Est non ridondanti provenienti da una libreria di cloni a cDNA di cervello bovino. Il secondo soggetto è il coinvolgimento dei microRNA, una nuova classe di piccoli RNA regolatori non codificanti, nello sviluppo della ghiandola mammaria. E' stata analizzata l'espressione di un set di microRNA noti in letteratura nei diversi stadi dello sviluppo dell'organo e sono state costruite librerie di cloni a cDNA di potenziali microRNA a partire da diversi stadi del ciclo dell'organo. / In this thesis two different subjects have been studied. The first is the construction of a second generation high-density RH map of the bovine using the RH panel of the Roslin Institute. The panel have been characterized by PCR with a set of non-redundant EST chosen from a cDNA library of bovine brain. The second work treats about the involvement of miRNAs in the development of mammary gland. A set of 25 known miRNAs have been chosen and their expression have been examined in the different stages of mammary gland development. Libraries of potential miRNAs have been constructed from different stages of mammary gland development and some miRNAs have been validated.

No description available.

Cycling of the relative humidity (RH) levels in the reactant streams of polymer electrolyte membrane (PEM) fuel cells has been reported to decay fuel cell performance. This study focuses on the accelerated durability testing to examine different modes of membrane failure via RH cycling. A single PEM fuel cell with an active area of 42.25 cm2 was tested. A Greenlight G50 test station was used to establish baseline cell (Run 1) performance with 840 hours of degradation under high-humidity idle conditions at a constant current density of 10 mA cm-2. Under the same conditions, two other experiments were conducted by varying the RH. For the H2-air RH cycling test (Run 2), anode and cathode inlet gases were provided as dry and humidified gases. Another RH cycling experiment was the H2 RH cycling test (Run 3): the anode inlet gas was cycled whereas keeping the other side constantly at full humidification. These two RH cycling experiments were alternated in dry and 100% humidified conditions every 10 and 40 minutes, respectively. In the experiments, the fuel cells contained a GoreTM 57 catalyst coated membrane (CCM) and 35 BC SGL gas diffusion layers (GDLs). The fuel cell test station had been performed under idle conditions at a constant current density of 10 mA cm-2. Under the idle conditions, operating at very low current density, a low chemical degradation rate and minimal electrical load stress were anticipated. However, the membrane was expected to degrade due to additional stress from the membrane swelling/contraction cycle controlled by the RH. In this work the performance of the 100% RH humidified cell (Run 1) was compared with that of RH cycling cells (Run 2 and Run 3). Chemical and mechanical degradation of the membrane were investigated using in-situ and ex-situ diagnostic methods. The results of each measurement during and after fuel cell operation are consistent. They clearly show that changing in RH lead to an overall PEM fuel cell degradation due to the increase in membrane degradation rate from membrane resistance, fluoride ion release concentration, hydrogen crossover current, membrane thinning, and hot-spot/pin-hole formation.