| 1. |
- Holmboe, Michael
(författare)
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The bentonite barrier : microstructural aspects on colloid filtration and radiation effects on bentonite colloid stability
- 2009
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In many countries a multi-barrier concept in a deep geological repository is planned for final disposal of nuclear waste. Many of these different concepts, for example the Swedish KBS-3 model, include an engineered barrier consisting of compacted bentonite. The compacted bentonite barrier will be positioned around copper canisters holding the nuclear waste and act as a transport barrier for various radioactive species. This is due to the compact microstructure as well as the large sorption capacity of compacted water saturated bentonite. During its required lifetime (> 100000 years) a deep geological repository and the bentonite barrier itself will be subjected to changing groundwater composition and flow, geochemistry, temperature, and large doses of ionizing irradiation. The long lifetime and significance of a deep geologic repository mean that it must be regarded as a thermodynamically open system and be assessed in terms of worst case scenarios. In case of water bearing fractures, formed by future movements in the granitic host bedrock, low ionic strength groundwater can endanger the stability of the bentonite barrier. Prolonged erosion of the bentonite barrier might cause significant loss of buffer material and jeopardize its overall functionality. This thesis deals with the microstructure of the water saturated compacted bentonite as a function of compaction, as well as effects of γ-radiation on bentonite dispersions. The microstructure was investigated both indirectly through colloid filtration experiments, as well as using low-angle XRD. Effects of γ-irradiation were investigated in terms of colloid stability and sediment behavior of bentonite (and Na-montmorillonite) dispersions. The colloid filtration experiments, using small gold colloids of different sizes as tracers, shows that the microstructural constraints of bentonite effectively filter even extremely small inorganic colloids. Colloid transport was only observed at very low compactions (i.e. dry density g/cm3) where the average interlayer distances of montmorillonite exceeded the colloid size, indicating interlayer rather than interparticle transport. From the low-angle XRD experiments the free porosity of water saturated compacted bentonite was determined by comparing its basal spacings (interlayer distances + 1 nm) with the hypothetical basal spacings assuming no free porosity. Irrespective of compaction, the maximum free porosity proved to be very low, in line with the colloid filtration experiments. The results showed that existing microstructural models sometimes exaggerate the importance of interparticle voids. The γ-irradiation experiments showed a radiation induced increase in colloid stability. This radiation induced effect also changed the sedimentation behavior of irradiated bentonite dispersions compared to unirradiated samples. The effect is attributed to an increase in surface potential of the bentonite colloids, due to reactions with the short-lived radicals formed upon water radiolysis.
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| 2. |
- Deyhle Jr, Richard
(författare)
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Cross-modal Imaging in Lung Research: From µCT dosimetry to synchrotron phase contrast microtomography biomechanical insights in preclinical lung injury models
- 2024
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Lung diseases continue to present a large burden to public health, especially in industrialized countries. For abetter understanding of the underlying patho-mechanisms in lung related diseases as well as for testing theefficacy of novel therapies, preclinical studies in animal models are indispensable. The significance of preclinical X-ray based micro-computed tomography (µCT) research lies in its ability to provide high-resolution, non-invasive lung imaging of small animals as the air inside the lung acts as a natural contrast and to image the lung parenchyma longitudinally to assess functional and morphological alterations and test efficacy of therapeutic interventions. This often requires requires imaging protocols that balance between sufficient image quality and clinically relevant radiation absorbed doses. A reproducible method for evaluation of absorbed radiation absorbed doses is desirable. Absorbed radiation absorbed doses were measured in a polymethyl methacrylate (PMMA) phantom using standard TLD and a novel type of OSLD made form household salt. Four imaging protocols from MILabs “xUHR-µCT” scanner were tested. A large discrepancy was observed from results compared to vendor-provided values. The results indicate a need for thorough empirical dose measurements prior to performing longitudinal studies. Four-dimensional imaging, allows for investigation of the dynamics of regional lung functional parameters simultaneously with structural deformation of the lung as a function of time. It is of significant interest to have direct visualization and quantification of interstitial lung diseases at spatial resolutions beyond the capabilities of clinical and conventional absorption-based only CT. Thus far, the high intensity of synchrotron X-ray light sources offer a tool to investigate dynamic morphological and mechanistic features, enabling dynamic in-vivo microscopy. This investigation elucidates the direct effects of interventions targeting the pathophysiology of Acute Respiratory Distress Syndrome (ARDS) and Ventilator-Induced Lung Injury (VILI) on the terminal airways and alveolar microstructure within intact lungs. In such conditions, the relationship between microscopic strain within the mechanics of the alveolar structure and the broader mechanical characteristics and viscoelastic properties of the lungs remains poorly understood. A time-resolved synchrotron phase-contrast micro-computed tomography imaging acquisition protocol based on the synchronization between the mechanical ventilation and the cardiac activity was used to resolve the lung parenchyma motion with an effective isotropic voxel size of 6 µm. Quantitative maps of microscopic local lung tissue strain within aerated lung alveolar tissue under protective mechanical ventilation in anesthetized rats were obtained. This approach was used to assess the effect of alterations in lung tissue biomechanics induced by lung injury at 7 days after single-dose, intratracheal bleomycin instillation in combination with short-term high-tidal volume (VT) mechanical ventilation. Overall, this work address the aspects of radiation exposure to in experimental imaging of small animals and lays a foundation for a more nuanced understanding of lung injury and mechanical ventilation. In the future, it may result in a more effective and less injurious respiratory support for patients with acute lung injury or chronic lung diseases.
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| 3. |
- Pfister, Anna, 1984-
(författare)
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Outcomes of Myosin 1C Gene Expression Depletion on Cancer-related Pathways, in Vitro and in Clinical Samples
- 2016
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The unconventional myosin IC has previously been suggested to be a haploinsufficient tumour suppressor. The mechanism for this action has hitherto been unknown, however, and hence we decided to attempt to elucidate the genes involved. The first study involved knock-down of MYO1C using siRNA technology followed by whole transcriptiome microarray analysis performed on samples taken at different time points post transfection. This revealed a cornucopia of differential expressions compared to the negative control, among them we found an early up-regulation of the PI3K/AKT pathway and the pathway for prostate cancer. Among the down regulated pathways we found endometrial-, colorectal cancer and small cell lung cancer as well as the cell cycle pathway which was a little counter intuitive to the hypothesis that MYO1C suppresses cancer. For the next study six different genes (CCND1, CCND2, CDKN2B, CDKN2C, MYC, RBL1) important for the transitions into S-phase of the cell cycle were therefore chosen for validation using qPCR. These six genes and MYO1C were analysed on both the original time series and a new biological replicate as well as a well stratified set of endometrial carcinoma samples. We were able to verify the significant down-regulation of CCND2 in both time series indicating that this is caused by the depletion of MYO1C. In the tumour samples we saw a negative correlation between the expression of MYO1C and FIGO grade corroborating results previously found by our group when looking at protein expression.
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| 4. |
- Lundberg, Stina
(författare)
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Examining Female Resilience to Early Environmental Influences : Short- and long-term consequences on behaviour, HPA axis activity and alcohol intake after prolonged maternal separation
- 2017
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Early-life experiences are an important factor influencing further development of the individual. Adverse experiences early in life, such as various kinds of abuse or neglect, are types of early-life stress that can adversely affect an individuals health, as well as contribute to the development of an array of disorders later in life. Most prominent is the increased risk for psychiatric disorders, primarily depression, anxiety-related and substance use disorders. Many of the implicated disorders also exhibit sex-dependent differences in prevalence and severity. Thus, it is important to consider sex-dependent effects when modeling early-life stress and its consequences. A common animal model for early-life stress is prolonged maternal separation (MS). MS is an umbrella term for different manipulations of the early environment of rodent pups. In this thesis, a prolonged MS condition with separation of rat litters from their dams for six hours per day during the first three weeks of life (MS360) was used. In male offspring MS360 have been associated with early-life stress and negative effects apparent during both adolescence and adulthood. The literature regarding female offspring is not as substantial as for the males, but it seems that females’ exhibit less pronounced or no effect after prolonged MS independent of separation time. In addition, the studies that have examined female offspring have done so in adulthood and thus, short-term consequences of prolonged MS possibly present during adolescence have not been investigated. The aim of this thesis is to provide a broad investigation into the consequences of prolonged MS in female offspring, in both adolescence and adulthood. As stated above, MS360 was used as the adverse rearing condition in this thesis. As control, daily short MS (15 min; MS15) was used; this ensured that all animals were handled equally, except for the length of separation. Any detected differences are thus due to the length of separation only. Three categories of assessments were used to evaluate short- and long-term consequences: 1) hypothalamus-pituitary-adrenal (HPA) axis assessments, 2) behavioral assessments and 3) assessment of voluntary alcohol consumption. HPA axis reactivity was assessed in adolescent and adult offspring by blood sampling before and after challenge. HPA activity was also evaluated after long-term alcohol consumption by measurement of the fecal corticosterone content. Behavior was assessed in adolescence by registration of social play behavior and in adulthood by generation of behavioral profiles in the multivariate concentric square fieldTM (MCSF). Alcohol consumption was evaluated using the modified intermittent alcohol access schedule with the two- (20% alcohol) and three- bottle (5% and 20% alcohol) free-choice paradigms. Female offspring did not differ depending on rearing condition in HPA reactivity in adolescence or adulthood. However, after the long-term alcohol intake, MS360 females had increased levels of corticosterone in their feces compared to MS15 females. No difference was detected in adolescent social play among female offspring and only a minor alteration was detected in the adult behavioral profile, where MS360 females had increased risk assessment compared to MS15 females. No effect of rearing condition was seen during the two-bottle choice paradigm of alcohol intake, while whole- group differences over time were discovered. Alcohol intake and preference were highest the first week of access and directly after a two-week deprivation period, apart from those time-points, intake and preference were maintained on a stable level. In the three-bottle choice, an interaction with rearing condition was revealed for the total alcohol preference, however this only translated to a minor group-dependent difference. In conclusion, females reared under a prolonged MS paradigm exhibited no or only minor basal changes in HPA axis reactivity, behavior and alcohol consumption. However, after long-term alcohol intake females subjected to prolonged MS had increased corticosterone excretion into feces. That differences only emerge after long-term perturbation can be a sign that females have higher buffering capabilities than males after early-life adversity, as modeled through prolonged MS, and thus require additional challenges before consequences become apparent. This thesis highlights the importance of considering sex when studying the impact of early-life stress, and that the choice of animal model needs to be considered carefully in relation to the research question posed.
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| 5. |
- Larsson, Mikael, 1982
(författare)
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Heterogeneities in polymer gels: Effects on swelling and mechanical properties
- 2010
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Polymeric hydrogels is a class of scientifically interesting materials that are being extensively studied. They are found in numerous applications within; drug delivery, hygiene products, food industry, analytical chemistry, etc. In addition, polymeric hydrogels have promising future applications as; cell scaffolds, implants, sensors, etc.One of the critical parameters for the performance of hydrogels in different applications is their structure. One such structural feature is the heterogeneity of the material, where the term heterogeneity applies to many different types of structural variations.The aim of this thesis was to investigate how different kinds of heterogeneities can be introduced into hydrogels, and how the presence of the different heterogeneities can be related to swelling and mechanical properties of such materials. The materials investigated were; polyacrylic acid neutralized with calcium hydroxide, polysodium acrylate superabsorbents with microfibrillated cellulose utilized as a filler and hydroxypropyl methylcellulose with heterogeneous distribution of the substituents.It was found that the presence of calcium ions during the synthesis of crosslinked polyacrylic acid introduces heterogeneities, both in network structure and in the form of phase separation, with dramatic impact on gel properties. Microfibrillated cellulose was found to even in small amounts cause significant changes to the swelling and shear modulus of crosslinked polysodium acrylate superabsorbents. The effect of the microfibrillated cellulose was similar as if an equivalent mass of covalent crosslinker had been used, but with improved resistance to fracture. For hydroxypropyl methylcellulose it was found that a heterogeneous distribution of the substituents causes increased interactions within the material, as determined from the glass transition temperature. Those increased interactions are coherent with earlier reports on solution behaviour for heterogeneously substituted hydroxypropyl methylcellulose.Hopefully the results presented in this thesis can contribute to the field of gel science, and in particular to the design of new multi-component soft materials.
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| 6. |
- Ersson, Lisa, 1985-
(författare)
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β-N-methylamino-L-alanine (BMAA)-induced neurotoxicity : Studies in vitro and in vivo
- 2020
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- β-N-methylamino-L-alanine (BMAA) is a neurotoxic non-proteinogenic amino acid produced naturally by cyanobacteria, diatoms and dinoflagellates and it has been detected in samples from fresh and marine water from all over the world. It can bioaccumulate in fish and shellfish, and has a potential to biomagnify in a terrestrial food chain. BMAA was first discovered in the search for a neurotoxin related to the amyotrophic lateral sclerosis/Parkinsonism-dementia complex (ALS/PDC) found among the Chamorro people in Guam. This non-proteinogenic amino acid has also been suggested to contribute to sporadic neurodegenerative diseases such as amyotrophic lateral sclerosis (ALS), Parkinson's disease (PD) and Alzheimer's disease (AD). BMAA can induce neurotoxicity via multiple mechanisms. It can act as an excitotoxin by activating glutamate receptors and to induce oxidative stress. It has also been suggested to be misincorporated into proteins leading to misfolded protein aggregates. Previous studies have demonstrated a specific damage in the hippocampus, including intracellular fibril formation, in adult rats following neonatal exposure to BMAA. In this thesis both in vitro and in vivo models were used to characterize the uptake, transport and effects of BMAA in cultured cell lines and in neonatal rodent brain tissue. The uptake of radiolabeled BMAA, as well as the effects of various amino acids and transporter antagonists on the uptake were studied in human mammary epithelial cells, intestinal epithelial cells, glioblastoma and neuroblastoma cells. Based on the obtained results a potential human mother-to-infant transfer of BMAA was suggested. BMAA-induced metabolic changes in a differentiated human neuroblastoma cell line were also characterized. The results revealed a plentitude of altered metabolites, many of them involved in amino acid metabolism and the TCA cycle. Of special interest were the perturbations in alanine, aspartate and glutamate metabolism as this pathway is involved in neurotransmission. The results revealed that BMAA can interfere with fundamental metabolic and neurotransmission pathways. Finally, the levels of free and protein-associated BMAA in the brain and peripheral tissues in neonatal rats exposed to BMAA were analysed. The results revealed high levels of free BMAA in some brain regions, thus demonstrating that the neonatal brain is not protected from BMAA by the blood-brain barrier. The results also revealed a protein-association of BMAA in the neonatal hypothalamus and hippocampus. Although the total amount of BMAA in the hippocampus was not high compared to other brain regions, the percentage of protein-associated BMAA was significantly higher. The results suggest that the protein-association of BMAA may play a role in the long-term effects in the hippocampus following neonatal exposure to BMAA. The studies in this thesis have demonstrated 1) a potential transfer of BMAA via breast milk to the brain of the nursing infant, 2) BMAA-induced metabolic alterations related to neurotransmission in human neuroblastoma cells and 3) that both free and protein-associated BMAA can be detected in the neonatal rat brain.
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| 7. |
- Alinaghizadeh, Hassan, Statistiker, 1961-
(författare)
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Radioactive fall-out from the Chernobyl nuclear power plant accident in 1986 and cancer rates in Sweden, a 25-year follow up
- 2019
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Aim: The current research aimed to study the association between exposure to low-dose radiation fallout after the Chernobyl accident in 1986 and the incidence of cancer in Sweden.Methods: A nationwide study population, selecting information from nine counties out of 21 in Sweden for the period from 1980 – 2010.In the first study, an ecological design was defined for two closed cohorts from 1980 and 1986. A possible exposure response pattern between the exposure to 137Cs on the ground and the cancer incidence after the Chernobyl nuclear power plant accident was investigated in the nine northernmost counties of Sweden (n=2.2 million). The activity of 137Cs at the county, municipality and parish level in 1986 was retrieved from the Swedish Radiation Safety Authority (SSI) and used as a proxy for received dose of ionizing radiation. Information about diagnoses of cancer (ICD-7 code 140-209) from 1958 – 2009 were received from the Swedish Cancer Registry, National Board of Health and Welfare (368,244 cases were reported for the period 1958 to 2009). The incidence rate ratios were calculated by using Poisson Regression for pre-Chernobyl (1980 – 1986) and post-Chernobyl (1986 – 2009) using average deposition of 137Cs at three geographical levels: county (n=9), municipality (n=95), and parish level (n=612). Also, a time trend analysis with age standardized cancer incidence in the study population and in the general Swedish population was drawn from 1980 – 2009.In the second study, a closed cohort was defined as all individuals living in the three most contaminated counties in mid-Sweden in 1986. Fallout of 137Cs was retrieved as a digital map from the Geological Survey of Sweden, demographic data from Statistics Sweden, and cancer diagnosis from the Swedish Cancer Registry, National Board of Health and Welfare. Individuals were assigned an annual 137Cs exposure based on their place of residence (1986 through 1990), from which 5-year cumulative 137Cs exposures were calculated, accounting for the physical decay of 137Cs and changing residencies. Hazard ratios for having cancer during the follow-up period, adjusted for age, sex, rural/non-rural residence, and pre-Chernobyl total cancer incidence, were calculated.Results: No obvious exposure-response pattern in the age-standardized total cancer incidence rate ratios could be seen in the first study. However, a spurious association between the fallout and cancer incidence was present, where areas with the lowest incidence of cancer before the accident coincidentally had the lowest fallout of cesium-137. Increasing the geographical resolution of exposure from the average values of nine counties to the average values of 612 parishes resulted in two to three times higher degree of variance explanation by regression model. There was a secular trend, with an increase in age standardized incidence of cancer from 1980 – 2009. This trend was stronger in the general Swedish population compared to the nine counties of the present study.In the second study, 734,537 people identified were divided into three exposure categories: the first quartile was low exposure (0.0 to 45.4 kBq/m2), the second and third quartiles were intermediate exposure (45.41 to 118.8 kBq/m2), and the fourth quartile was highest exposure (118.81 to 564.71 kBq/m2). Between 1991 and 2010, 82,495 cancer cases were registered in the three counties. Adjusted HRs (95% CI) were 1.03 (1.01 to 1.05) for intermediate exposure, and 1.05 (1.03 to 1.07) for the highest exposure, when comparing to the reference exposure.Conclusion: Using the ecological data, there was no exposure response trend; however, after refining the data to the individual level of exposure, there was an overall exposure response pattern. Nonetheless, due to the time dependency, these results were restricted to the age group of 25 – 49 among males. Using register-based data only, for determining the association between low-dose exposure to radiation and the risk of developing cancer, is difficult since we cannot control for other significant factors that are associated with cancer.
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| 8. |
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| 9. |
- Holm, Patrik
(författare)
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Single-chain antibody construction and functional mapping of the monoclonal antibody TS1 : Its interaction with the antigen and the anti-idiotype
- 2005
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The aims of this study are to synthesize and produce a single-chain antibody (scFv) of the anti-cytokeratin 8 monoclonal IgG antibody TS1 and to functionally map amino acid residues important for the interaction with its antigen and the anti-idiotypic antibody TS1. The TS1 antibody has been shown to be effective in binding cytokeratin 8 (CK8) expressed in tumors in vivo and is proposed to be useful in immunotargeting and/or immunotherapy. The anti-idiotypic antibody TS1 can be used to regulate the tumor:non-tumor ratio. Mutagenesis of certain amino acid residues can be used to alter the affinity to improve the tumor:non-tumor ratio further. In the present study, the TS1 IgG was chemically modified to specify groups of residues important for interaction with both CK8 and TS1. If important residues were found in the CDRs, they were mutated in the TS1 scFv construct and the effect was studied using ELISA. The main conclusions drawn from this study are that the important amino acid residues in TS1 for the interaction with both CK8 and TS1 are mainly tyrosines, charged residues and a tryptophan. A central interacting interface was identified with the somewhat unusual participation of residues in the CDR 2 of the light chain. Mutations which resulted in increased affinity to both CK8 and TS1 were also identified.
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| 10. |
- Liao, Rong-Zhen
(författare)
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Mechanistic insights into dinuclear zinc enzymes from density functional theory studies
- 2009
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In this thesis, quantum chemical methods have been used to shed light on the reaction mechanisms of several dinuclear zinc enzymes. The enzymes studied are involved in the hydrolysis of phosphates, amides, and carboxylic esters, namely RNase Z, Dihydroorotase (DHO), and N-acyl homoserine lactone hydrolase (AHL lactonase). The density functional method B3LYP, together with quite large active site models, was used to investigate these enzymatic reactions. Several plausible proposed mechanisms, involving protonation states of important active site residues (DHO), substrate orientations (AHL lactonase), have been considered. The calculated energetics can be used to assess the feasibility of the suggested reaction mechanisms. Based on the calculations and also on other related dinuclear zinc enzymes studied previously, some general mechanistic features have been uncovered. For all three enzymes, the nucleophilicity of the bridging hydroxide is shown to be sufficient to perform the nucleophilic attack on the substrates. During the attack, the negative charge is transferred from the bridging hydroxide to the substrate oxygen (P=O or C=O). For phosphate hydrolysis, an in line attack have been suggested for RNase Z. In addition, the two zinc ions in RNase Z are directly involved in stabilizing the negative charge in the penta-coordinated transition states. For carbonyl substrates, only one zinc ion participates in the oxygen anion stabilization in the transition states and the tetrahedral intermediates. Furthermore, the enzymes always use the zinc ion with less negatively-charged ligands to play such role. All the substrates investigated have poor leaving groups. Therefore, either the zinc ions or some active site residues help the cleavage of the scissile bond. For RNase Z, a Glu-His diad was suggested to protonate the leaving group. For DHO, an Asp residue was shown to transfer a proton from the bridging hydroxide to the leaving group nitrogen. For AHL lactonase, a zinc ion was also observed to stabilize the leaving oxygen anion.
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