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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
151

Synthesis of Insulin-Regulated Aminopeptidase (IRAP) inhibitors

Agalo, Faith January 2015 (has links)
The need for alternative cognitive enhancers has risen due to the fact that clinical trial results of the drugs currently approved for treating these disorders have not been satisfactory. IRAP has become a possible drug target for treating cognitive impairment brought about by Alzheimer’s disease, head trauma or cerebral ischemia, among others. This came after the revelation that Angiotensin IV enhances memory and learning. Angiotensin IV, the endogenous ligand of IRAP has been structurally modified with the aim of producing potent IRAP inhibitors. However, the peptidic nature of these inhibitors restricts their use; they are not likely to cross the blood brain barrier. Other strategies for generating IRAP inhibitors have been through structure-based design and receptor based virtual screening. These drug-like molecules have exhibited positive results in animal studies. IRAP inhibitors have been identified via a HTS of 10500 low-molecular weight compounds to give the hit based on a spirooxindole dihydroquinazolinone scaffold, with an IC50 value of 1.5 µM. In this project, some analogues to this hit compound have successfully been synthesized using a known method, whereas others have been synthesized after additional method development. The application of the developed method was found to be limited, because poor yield was obtained when a compound with an electron withdrawing substituent on the aniline was synthesized. As a result of this, modification of this method may be required or new methods may have to be developed to synthesize these types of analogues. Inhibition capability of 5 new spirooxindole dihydroquinazolinones was tested through a biochemical assay. Compound 6e emerged as the most potent inhibitor in the series, with an IC50 value of 0.2 µM. This compound will now serve as a lead compound and should be used as a starting point for future optimization in order to generate more potent IRAP inhibitors.
152

Biopharmaceutical investigations of doxorubicin formulations used in liver cancer treatment : Studies in healthy pigs and liver cancer patients, combined with pharmacokinetic and biopharmaceutical modelling

Dubbelboer, Ilse R January 2017 (has links)
There are currently two types of drug formulation in clinical use in the locoregional treatment of intermediate hepatocellular carcinoma (HCC). In the emulsion LIPDOX, the cytostatic agent doxorubicin (DOX) is dissolved in the aqueous phase, which is emulsified with the oily contrast agent Lipiodol® (LIP). In the microparticular system DEBDOX, DOX is loaded into the drug-eluting entity DC Bead™. The overall aim of the thesis was to improve pharmaceutical understanding of the LIPDOX and DEBDOX formulations, in order to facilitate the future development of novel drug delivery systems. In vivo release of DOX from the formulations and the disposition of DOX and its active metabolite doxorubicinol (DOXol) were assessed in an advanced multisampling-site acute healthy pig model and in patients with HCC. The release of DOX and disposition of DOX and DOXol where further analysed using physiologically based pharmacokinetic (PBPK) and biopharmaceutical (PBBP) modelling. The combination of in vivo investigations and in silico modelling could provide unique insight into the mechanisms behind drug release and disposition. The in vivo release of DOX from LIPDOX is not extended and controlled, as it is from DEBDOX. With both formulations, DOX is released as a burst during the early phase of administration. The in vivo release of DOX from LIPDOX was faster than from DEBDOX in both pigs and patients. The release from DEBDOX was slow and possibly incomplete. The in vivo release of DOX from LIPDOX and DEBDOX could be described by using the PBBP model in combination with in vitro release profiles. The disposition of DOX and DOXol was modelled using a semi-PBPK model containing intracellular binding sites. The contrast agent Lipiodol® did not affect the hepatobiliary disposition of DOX in the pig model. The control substance used in this study, cyclosporine A, inhibited the biliary excretion of DOX and DOXol but did not alter metabolism in healthy pigs. The disposition of DOX is similar in healthy pigs and humans, which was shown by the ease of translation of the semi-PBPK pig model to the human PBBP model.
153

Minimizing Liquid Waste in Peptide Synthesis : A New Application for the Rotating Bed Reactor

Nordström, Peter January 2021 (has links)
Peptide drugs are used to treat a broad spectrum of diseases such as cancer and HIV and have many more promising applications, such as new vaccines against SARS-CoV-2. The most popular manufacturing method for peptides is solid-phase peptide synthesis (SPPS). The main drawback of SPPS is that it is a costly and wasteful process.  SpinChem is a company that provides technology solutions for chemical processes. Recently, SpinChem has started investigating if their Rotating Bed Reactor (RBR) is suitable for peptide synthesis. The goal of this project is to investigate how the RBR can make processes like SPPS more resource-efficient. The idea is that the RBR-system can maximize the solid-phase to liquid ratio (STL). The STL is the ratio of the volume of solid-phase material and the volume of liquid. By maximizing the STL, it is possible to manufacture peptides using less solvents and chemicals. The main quest of the project is formulated into a single question:  How does a high STL affect the efficiency of the RBR-system?  To answer the question, Minitab's statistical software and design of experiments (DOE) will be used to plan and perform experiments in both lab- and industrial scales. DOE factorial experiments are used to gain as much information as possible about the new RBR-system. The results are analyzed and summarized to make a solid foundation for the continued work on the new RBR application.  Peptide synthesis efficiency in the RBR-system is measured using ionic adsorption. The ionic adsorption rate is measured in both lab-scale and industrial-scale experiments. In the lab-scale experiments, the decrease of ions was on average 86,5% after just 15 s with an average STL of 0,936. The industrial-scale experiments showed a similar result where the average decrease in ions was 92,9% after 20 s with an average STL of 0,947. It was concluded that the RBR-system can reduce the consumption of washing-solvent in SPPS by up to 82%.
154

Studies on anti-leukemic terpenoids from medicinal mushrooms and marine sponges with ChemGPS-NP-based targets investigation of lead compounds

Lai, Kuei-Hung January 2017 (has links)
This thesis investigates the anti-leukemic activity of terpenoids isolated from medicinal mushrooms and marine sponges, as well as their possible targets and mechanisms of action. In the first section, we focused on studying the triterpenoidal components of three triterpenoid-enriched medicinal mushrooms Antrodia cinnamomea, Ganoderma lucidum, and Poria cocos, which have been used in folk medicine for centuries and also developed into several contemporary marketed products. We isolated the major and characteristic triterpenoids from these mushrooms, together with six new lanostanoids (II-1–II-6). The anti-leukemic activity of the isolates was evaluated in vitro using MTT proliferative assay and seven of them exhibited potential anti-leukemic effect. The active lead compounds were further subjected to computational analyses utilizing the ChemGPS-NP tool. We established a database for the anti-leukemic relevant chemical space of triterpenoids isolated from these three medicinal mushrooms, which could be used as a reference database for further research on anti-leukemic triterpenoids. Our results indicated that the anti-leukemic effect of the active lead compounds was mediated not only through topoisomerases inhibition but also through inhibiting DNA polymerases. The second and third sections focused on isolation of anti-leukemic sesterterpenoids from sponges. The investigation of Carteriospongia sp. led to the isolation of two new scalarane-type sesterterpenoids (III-1 and III-2) and one known tetraprenyltoluquinol-related metabolite (III-3). All isolates exhibit an apoptotic mechanism of action against Molt 4 cells, found to be mediated through the disruption of the mitochondrial membrane potential (MMP) and inhibition of topoisomerase IIα expression. Detailed investigation of the apoptotic mechanism of action using molecular docking analysis revealed that compound III-1 might target Hsp90 protein. The apoptotic-inducing effect of III-3 was supported by in vivo experiment by suppressing the volume of xenograft tumor growth (47.58%) compared with the control. In the final section of this thesis we studied manoalide and its derivatives, sesterterpenoids isolated from the sponge Luffariella sp.. Manoalide has been studied as a potential anti-inflammatory agent for the last thirty years with more than 200 publications and 40 patents. However, the configurations at positions 24 and 25 were never revealed. In the current study, ten manoalide-type sesterterpenoids (IV-1–IV-10) were isolated from Luffariella sp. and their stereoisomers at positions 24 and 25 were identified and separated for the first time. The configuration at positions 24 and 25 showed to have a significant effect on the anti-leukemic activity of manoalide derivatives, with the 24R,25S-isomer exhibiting the most potent anti-leukemic activity. The apoptotic mechanism of action of compound IV-7 against Molt 4 cells was investigated, and the compound was found to trigger MMP disruption and intracellular reactive oxygen species (ROS) generation. Compound IV-7 also inhibited activity against both human topoisomerases, I and II. The in vivo experiment further supported the anti-leukemic effect of IV-7 with a 66.11% tumor volume suppression compared to the control.
155

Selectivity in NMR and LC-MS Metabolomics : The Importance of Sample Preparation and Separation, and how to Measure Selectivity in LC-MS Metabolomics.

Elmsjö, Albert January 2017 (has links)
Until now, most metabolomics protocols have been optimized towards high sample throughput and high metabolite coverage, parameters considered to be highly important for identifying influenced biological pathways and to generate as many potential biomarkers as possible. From an analytical point of view this can be troubling, as neither sample throughput nor the number of signals relates to actual quality of the detected signals/metabolites. However, a method’s selectivity for a specific signal/metabolite is often closely associated to the quality of that signal, yet this is a parameter often neglected in metabolomics. This thesis demonstrates the importance of considering selectivity when developing NMR and LC-MS metabolomics methods, and introduces a novel approach for measuring chromatographic and signal selectivity in LC-MS metabolomics. Selectivity for various sample preparations and HILIC stationary phases was compared. The choice of sample preparation affected the selectivity in both NMR and LC-MS. For the stationary phases, selectivity differences related primarily to retention differences of unwanted matrix components, e.g. inorganic salts or glycerophospholipids. Metabolites co-eluting with these matrix components often showed an incorrect quantitative signal, due to an influenced ionization efficiency and/or adduct formation. A novel approach for measuring selectivity in LC-MS metabolomics has been introduced. By dividing the intensity of each feature (a unique mass at a specific retention time) with the total intensity of the co-eluting features, a ratio representing the combined chromatographic (amount of co-elution) and signal (e.g. in-source fragmentation) selectivity is acquired. The calculated co-feature ratios have successfully been used to compare the selectivity of sample preparations and HILIC stationary phases. In conclusion, standard approaches in metabolomics research might be unwise, as each metabolomics investigation is often unique.  The methods used should be adapted for the research question at hand, primarily based on any key metabolites, as well as the type of sample to be analyzed. Increased selectivity, through proper choice of analytical methods, may reduce the risks of matrix-associated effects and thereby reduce the false positive and false negative discovery rate of any metabolomics investigation.
156

Pharmacokinetic-Pharmacodynamic Evaluations and Experimental Design Recommendations for Preclinical Studies of Anti-tuberculosis Drugs

Chen, Chunli January 2017 (has links)
Tuberculosis is an ancient infectious disease and a leading cause of death globally. Preclinical research is important for defining drugs and regimens which should be carried forward to human studies. This thesis aims to characterize the population pharmacokinetics and exposure-response relationships of anti-tubercular drugs alone and in combinations, and to suggest experimental designs for preclinical settings. The population pharmacokinetics of rifampicin, isoniazid, ethambutol and pyrazinamide were described for the first time in two mouse models. This allowed for linking the population pharmacokinetic model to the Multistate Tuberculosis Pharmacometric (MTP) model for biomarker response, which was used to characterize exposure-response relationships in monotherapy. Pharmacodynamic interactions in combination therapies were quantitatively described by linking the MTP model to the General Pharmacodynamic Interaction (GPDI) model, which provided estimates of single drug effects together with a quantitative model-based evaluation framework for evaluation of pharmacodynamic interactions among drugs in combinations. Synergism (more than expected additivity) was characterized between rifampicin and ethambutol, while antagonism (less than expected additivity) was characterized between rifampicin and isoniazid in combination therapies. The new single-dose pharmacokinetic design with enrichened individual sampling was more informative than the original design, in which only one sample was taken from each mouse in the pharmacokinetic studies. The new oral zipper design allows for informative pharmacokinetic sampling in a multiple-dose administration scenario for characterizing pharmacokinetic-pharmacodynamic relationships, with similar or lower bias and imprecision in parameter estimates and with a decreased total number of animals required by up to 7-fold compared to the original design. The optimized design for assessing pharmacodynamic interactions in the combination therapies, which was based on EC20, EC50 and EC80 of the single drug, provided lower bias and imprecision than a conventional reduced four-by-four microdilution checkerboard design at the same total number of samples required, which followed the 3Rs of animal welfare. In summary, in this thesis the population pharmacokinetic-pharmacodynamic models of first-line drugs in mice were characterized through linking each population pharmacokinetic model to the MTP model. Pharmacodynamic interactions were quantitatively illustrated by the MTP-GPDI model. Lastly, experimental designs were optimized and recommended to both pharmacokinetic and pharmacodynamic studies for preclinical settings.
157

Growth hormone in the brain : Focus on cognitive function

Brolin, Erika January 2017 (has links)
Cognitive impairments are an increasing health problem worldwide. In the developed countries, the average life expectancy has dramatically increased over the last decades, and with an elderly population more cases of cognitive impairments appear. Age, genetics, and different medical conditions such as diabetes mellitus, and substance use disorders may all contribute to declined cognitive ability. Physiological functions also decrease with increasing age, as does the activity of the growth hormone (GH)/insulin-like growth factor-1 (IGF-1) axis. Interestingly, both GH and IGF-1 are recognized for their neuroprotective effects and cognitive enhancement. The overall aim of this thesis was to investigate the impact of the somatotrophic axis (i.e. GH/IGF-1 axis) in rodents with cognitive deficiencies induced by diabetes or long-term drug exposure. For the first time cognitive impairments were characterized in diabetic mice using a spatial learning and memory task called the Barnes maze (BM). In diabetic mice, impaired learning in the BM was associated with decreased expression of the GH receptor (GHR) in the frontal cortex, a region important for e.g. working memory. Treatment with GH reversed certain cognitive impairments seen in diabetic animals. In rats treated with gamma-hydroxybutyrate (GHB), a significant decrease of Igf1 mRNA expression in the frontal cortex was observed. This observation may explain the impaired cognitive function previously seen following GHB administration. Furthermore, rats exposed to chronic morphine delivered in mini-osmotic pumps displayed memory impairments in the Morris water maze (MWM), an effect that seems to be associated with the composition of the N-methyl-d-aspartate (NMDA) receptor complex in the frontal cortex. In conclusion, the result strengthens the evidence for GH being a cognitive enhancer. Moreover, the result within this thesis identifies the frontal cortex as an important brain region, where gene expression related to the somatotrophic system is affected in rodents with cognitive impairments. The thesis especially emphasizes the importance of the local somatotrophic system in the brain with regard to cognitive function.
158

The Role of Cyclooxygenase-2 in Models of Epilepsy and Traumatic Brain Injury : Effects of Selective Cyclooxygenase-2 Inhibitors

Kunz, Tina January 2002 (has links)
<p>Cyclooxygenase-2 (COX-2) catalyses prostaglandin synthesis from arachidonic acid during inflammation. COX-2 is expressed in the normal brain and is induced in neurological disorders. There is evidence that COX-2 is involved in secondary events leading to cell death in the brain. The first objective was to study the expression of COX-2 in the brain after kainate (KA)-induced limbic seizures and brain trauma caused by controlled cortical contusion (CCC) and fluid percussion injury (FPI). COX-2 mRNA and protein were strongly induced by limbic seizures in the hippocampus, amygdala and piriform cortex. CCC and FPI resulted in an upregulation of COX-2 mainly in the dentate gyrus and cortex, with differences in expression levels in these regions between the models. The second objective was to evaluate the effects of selective COX-2 inhibitors on delayed cell death. Limbic seizures induced cell death in parts of the hippocampus, amygdala and functionally connected regions. Treatment with the selective COX-2 inhibitor rofecoxib 8 h after KA injection significantly reduced hippocampal cell death. Pre-treatment with the COX-2 inhibitor nimesulide augmented acute seizures with increased mortality and thus the effect of nimesulide on delayed cell death could not be evaluated. Effects of rofecoxib on trauma-induced cell death were studied in the FPI model. FPI induced delayed cell death mainly in the ipsilateral cortex and bilaterally in the dentate gyrus. Rofecoxib treatment, starting directly after injury was caused, had no protective effect against cell death. </p><p>The results suggest that COX-2 inhibition may be both detrimental and beneficial and largely dependent on the time schedule of treatment. COX-2 inhibitors might thus be of value as a neuroprotective treatment approach, provided that the role of COX-2 and the time course of effects of its metabolites in the brain are elucidated.</p>
159

Separation of Proteins with Capillary Electrophoresis in Coated Capillaries with and without Electroosmosis : Studies on Zone Broadening and Analytical Performances

Mohabbati, Sheila January 2006 (has links)
<p>Proteins have such structural features that they may interact with different types of surfaces by all possible forces, i.e., electrostatic, hydrogen bonding, hydrophobic. In this thesis two different types of coatings for fused silica capillaries aimed to eliminate such interactions have been studied. The first is a covalent, electroosmosis-free coating with polyacrylamide (PAA) and the second involves a non-covalent coating with the quaternary ammonium compound N, N-didodecyl –N, N- dimethylammonium bromide (DDAB) with a strong anodic electroosmosis. Optimal conditions regarding efficiency and resolution were established by variations of the composition and ionic strengths of buffers at pH below the isoelectric point of the proteins. To achieve high efficiency and resolution the choice of buffer constituents was extremely important. </p><p>The PAA coating was very stable at neutral and acidic conditions. Ammonium acetate (0.12 M) and ammonium hydroxyacetate (0.15 M) both at pH 4 provided the best separations with plate numbers up to 1 700 000 plate/m that is among the highest reported in the literature. Capillaries coated with DDAB were stable enough to, without recoating, permit consecutive separations of the proteins up to 9 hours (90 injections). High apparent efficiencies (over 1 million plates/m) were achieved with ammonium acetate (0.07 M), ammonium hydroxyacetate (0.08 M) and sodium phosphate (0.1 M) at pH 4. </p><p>Zone broadening was studied by determination of the variance contributions from all main parameters. Significant variances were contributions from longitudinal diffusion, capillary curvature, injection plug, detector time response and detector slit width while other variances, e.g., variances for Joule heat and vertical sedimentation were negligible. The remaining undetermined variance may have its origin in all types of relatively slow interactions including adsorption onto the capillary surfaces and protein-buffer component interactions. The results indicate that the latter is the main cause to zone broadening in protein separations.</p>
160

Interaction between Crosslinked Polyelectrolyte Gels and Oppositely Charged Surfactants

Nilsson, Peter January 2007 (has links)
<p>The interactions between anionic, crosslinked gels and cationic surfactants have been investigated. When exposed to oppositely charged surfactant, the gel collapses into a dense complex of polyion and micelles. During deswelling, the gel phase separates into a micelle-rich, collapsed surface phase, and a swollen, micelle-free core, both still part of the same network. As more surfactant is absorbed, the surface phase grows at the expense of the core, until the entire gel has collapsed. Polyacrylate (PA) gels with dodecyl- (C<sub>12</sub>TAB), and cetyltrimethylammonium bromide (C<sub>16</sub>TAB), as well as hyaluronate gels with cetylpyridinium chloride, have been studied. </p><p>Kinetic experiments have been performed on macro- as well as microgels, using micromanipulator assisted light microscopy for the latter. A surfactant diffusion controlled deswelling model has been employed to describe the deswelling. The deswelling kinetics of PA microgels have been shown to be controlled by surfactant diffusion through the stagnant layer surrounding the gel, as the surface phase is relatively thin for the major part of the deswelling. For macroscopic PA gels the surface phase is thicker, and the kinetics with C<sub>12</sub>TAB were therefore also influenced by diffusion through the surface phase, while for C<sub>16</sub>TAB they were dominated by it. </p><p>Relevant parameters have also been determined using equilibrium experiments. An irregular, balloon-forming deswelling pattern, mainly found for macrogels, as well as unexpectedly long lag times and slow deswelling for microgels, are reported and discussed. </p><p>The microstructure of fully collapsed PA/C<sub>12</sub>TAB complexes has been studied using small-angle X-ray scattering. A cubic <i>Pm3n</i> structure was found at low salt concentration, which melted into a disordered micellar phase as the salt concentration was increased. Further increasing the salt concentration dissolved the micelles, resulting in no ordering.</p>

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