No description available.

No description available.

This study investigates the Monte Carlo calculations of cell survival in metastatic subcutaneous melanoma cancer tumours. To achieve this goal, a Monte Carlo program called SLAB.FOR was developed by Prof. David Charlton. The program randomly places alphas from 213Bi in the medium, which is a cancer cell sized micro dosimeter with a SiO2 converter on the top and Si as the sensitive volume. Then the Monte Carlo program calculates the energy deposited by alphas and their chord length and also the dose deposited in the sensitive volume. To be able to use this program, some information was taken from phase one of a clinical trial conducted by the Centre of Experimental Radiation Oncology (CERO) in 2001. During the course of this study the administered activities on tumours with different diameters are determined. Using this information the number of alpha particles going through each m3 of the tumour was found. Based on this number, the program SLAB.FOR was run for different administered activities in the tumours. The output of the program yielded the energy deposited and the number of hits by the alpha particles as they go through the tumours. The output data was also used to calculate the cell survival values, energy and hit distribution probabilities. The cell survival values were then used to plot the cell survival curves. They were plotted against dose, number of hits and injected activity per volume of the tumours. These data were also used to plot the energy and hit distribution probability curves. Our results show that survival is dependent on the diameter of the cell and decreases when the dose deposited in the tumour increases. The survival also has a relationship with the number of hits that a cell receives and it also depends on the injected activity to the volume. The survival decreases as the number of hits and injected activity increases. Our results confirmed what was stated in the clinical trial conducted by the Centre of Experimental Radiation Oncology (CERO) in 2001.

No description available.

The practice of targeted killings is not a recent phenomenon in International Law. It has been practiced over the years and has been debated. In recent times, the term was popularized by the killing of Osama bin Laden. On 2 May 2011, U.S. Special Forces conducted an operation in Pakistan in which Osama Bin Laden was killed. He was said to be the leader of the Al-Qaeda Terrorist Group that claimed responsibility for the September 9/11 attacks on the U.S. that resulted in the death of thousands. There have been several other incidents of this nature and it is important to determine the legality of such strikes in order to regulate them better. This study comparatively examines state practice of those nations including the U.S., Israel and Russia that have carried out targeted killings while paying special attention to the justifications put forth in defense of the practice. These defenses range from national security and self-defenses. The paper goes a step further to examine some court cases that have particularly dealt with the issue of targeted killings to ascertain the judicial attitude to the practice. It also looks at the main killing techniques which include kill or capture raids and air strikes from unmanned aerial vehicles known as drones. The targeted individuals are alleged terrorists or others deemed dangerous, and their inclusion in kill/capture lists is based on undisclosed intelligence applied against secret criteria. The number of targeted killings that have been specifically carried out by the US has steadily escalated through the different presidential administrations. With reference to some prominent incidents of targeted killings, this study will present an international law perspective analyzing whether this practice can be legally justifiable. The study also focuses on the interaction between international law and the practice of targeted killing. An examination of the pertinent principles of the two branches of international law will be necessary to determine which one is applicable and when. / Dissertation (LLM)--University of Pretoria, 2013. / gm2014 / Public Law / unrestricted

A subgroup of non-small cell lung cancer (NSCLC) cases harbour mutations in classical oncogenes, which can affect therapy response and prognosis. By therapeutically targeting the corresponding proteins with inhibitory drugs, the clinical outcome for these lung cancer patients may be improved. One of these oncogenes is the phosphatidylinositol-4,5-bisphosphate 3-kinase, catalytic subunit alpha (PIK3CA) which encodes the catalytic subunit of the phosphatidylinositol 3 kinase (PI3K). PIK3CA is a central regulator in the PI3K/Akt/mTOR pathway, which controls cell growth and apoptosis. Mutations in the PIK3CA gene are considered to up-regulate the kinase activity in tumour cells and through that dysregulate fundamental cellular processes. PI3K inhibitors are currently tested in clinical trials and present a promising therapy option in lung cancer patients. In this study, a pyrosequencing assay for detection of PIK3CA mutations in tumours from patients with NSCLC was established. The three "hot-spot" codons 542, 545 and 1047 of the PIK3CA gene were analysed. The sensitivity of this assay was determined to the presence of 5 % of mutant alleles. In agreement with previous reports, three of the 60 lung cancer cases revealed PIK3CA mutations (5 %). All mutations occurred in exon 9 codon 542 or 545. In line with previous reports, two of the three samples harboured concurrent mutation in the EGFR or KRAS gene. The established pyrosequencing analysis for PI3KCA mutations provides a reliable and cost-effective assay for clinical diagnostics. The determination of the PI3KCA mutation status may help to distinguish patients for treatment targeting the PI3K pathway.

Solid tumors are commonly subject to hypoxia. Hypoxic cancer cells have undesirable properties such as a high tendency to metastasize and resistance to chemotherapy and radiotherapy. Hypoxia-inducible factors (HIFs) respond to the changes in oxygen levels, orchestrating the transcription of many proteins that are vital for the survival of hypoxic cancer cells. With their parent drug SN-38 as an inhibitor of both topoisomerase 1 and HIF-1, hypoxia-activated SN-38s may have a dual inhibitory effect on hypoxic tumor cells due to hypoxia-targeting and HIF-1 inhibition. To develop hypoxia-activated prodrugs of SN-38; 2-, 3-, and 4-nitrobenzyl SN-38s have been synthesized with good yields (78%, 67% and 68%, respectively). Topoisomerase 1 inhibitory assay on 2- and 4-nitrobenzyl SN-38s and cell viability assay on 2-, 3- and 4-nitrobenzyl SN-38s have been performed. All three derivatives showed less toxicity on K562 cells, which meets the principle of prodrug design. Cyclic voltammetry results suggest that the reduction potentials of these three derivatives may be not high enough for these compounds to be activated. The manner of reduction of three nitrobenzyl SN-38s is quasi-reversible under the testing condition, not against the proposed mechanism of activation. Two new derivatives of SN-38 have been designed to elevate reduction potential and further reduce toxicity. They are to be synthesized and tested for future work. / October 2016

Targeted sanctions’ impact over rebel groups has not been examined by scholars, making it unclear whether the policy mechanism has the capacity to peacefully resolve intrastate armed conflicts and cease hostilities by weakening rebel groups. Considering the mentioned, the paper explores how targeted sanctions impact rebel groups, and suggests that properly monitored and effectively enforced targeted sanctions have the capacity to weaken rebel groups, via shortening rebels’ economic, military and political resources. Using the method of structured, focused comparison, the suggested hypothesis is empirically tested on the rebel groups of Revolutionary United Front in Sierra Leone and the National Union for the Total Independence of Angola in Angola. The findings of the study revealed that effectively monitored and enforced targeted sanctions are capable of lessening rebels’ military and political resources, however, observing sanctions impact on economic resources proved difficult. Based on the analyses and findings the paper suggests that imposition of targeted sanctions should be initiated at the early warning phase of a conflict, rather at the point when the intensity of conflict has reached its peak.

Injury and degenerative disease of the central nervous system (CNS) are among the major causes for disabilities in humans. They result in permanent damage that is not repaired by regenerative processes. In contrast, anamniotes like fish and amphibia display a striking potential for successful regeneration in the CNS. The zebrafish (Danio rerio) has been established as a model for successful regeneration after spinal cord injury. However, it is yet unknown which factors are involved in regeneration after spinal lesions and other insults to the CNS. Focusing on motor neurons, I asked whether regeneration can also be observed in larval zebrafish. This would allow to take advantage of their accessibility to live imaging, pharmacological and genetic manipulation. It is unknown, whether the loss of a specific cell type in the absence of injury, which is reminiscent of the pathological change observed in neurodegenerative diseases, would be sufficient to induce regeneration. Comparing the regenerative response after spinal lesion to that after selective neuronal cell loss would allow to identify factors that act as a trigger for regeneration, e.g. mechanical injury signals, the extent of cell death or microglia activation. To address these questions, an experimental paradigm in which motor neurons can be selectively ablated without the need to inflict tissue damage would prove useful. Key findings of this work are: · Motor neuron generation ceases during early larval developmental stages. · The Nitroreductase system can be used for successful ablation of motor neurons in the larval spinal cord. · New motor neurons are generated in a regenerative response to both targeted ablation of motor neurons and spinal lesion in larval zebrafish after cessation of developmental generation of MNs. To test whether larval zebrafish can be used to analyse motor neuron regeneration, I carried out a birthdating study to establish a developmental time line for motor neuron generation in the spinal cord. The end of developmental motor neuron generation at an early time point, at around 54 hours post fertilisation, allows for the use of larval zebrafish to assess the regenerative response after insults to the spinal cord. In addition, I could show a time dependent role for Hedgehog signalling during the generation of a motor neuron subpopulation. The influence of Hedgehog is diminished before the end of motor neurogenesis. Utilizing the Gal4/UAS system to combine the Nitroreductase‐mCherry fusion protein expressing Tg(UAS:nfsB‐mCherry) with the motor neuron specific driver Tg(hb9:Gal4), I generated a new transgenic zebrafish line for the genetically targeted ablation of motor neurons. In the resulting transgenic fish, the administration of the prodrug Metronidazole induces apoptotic cell death in ~25% of spinal motor neurons leading to impaired motor performance and increased numbers of microglia in the spinal cord. My work shows that larval animals subjected to motor neuron ablation or spinal lesion display a regenerative response detected by increased numbers of newborn motor neurons. Importantly, this happens after developmental production of motor neurons has ceased, suggesting that progenitor cells are reverting to the generation of motor neurons. The data presented shows that in larval zebrafish, the selective loss of motor neurons is sufficient to induce a regenerative response in the spinal cord. The increased numbers of microglial profiles in the spinal cord after both spinal lesion and targeted cell ablation indicates a role for the immune system in mediating a regenerative response. This new targeted cell ablation paradigm in larval zebrafish will allow to identify and characterize the progenitor cell population forming new motor neurons. One can then further investigate how specific loss of motor neurons is sensed and which factors contribute to the activation of the endogenous stem cell populations. Using larval zebrafish has many benefits, as they are accessible to pharmacological testing with small molecules and live imaging. Moreover, the combination of additional transgenic reporter lines will allow for the investigation of single cell behaviour during regeneration.

The isoenzyme heme oxygenase 1 (HO-1) is a key element for maintaining cellular homeostasis. Upregulated in response to cellular stress, the HO-1 degrades heme into carbon monoxide (CO), biliverdin, and Fe2+. By means of a local cell-protective feedback loop the enzyme triggers numerous effects including anti-oxidative, anti-apoptotic, and anti-inflammatory events associated with complex signalling patterns which are largely orchestrated by CO. Various approaches to mimic this physiological HO-1 / CO system aiming for a treatment of medical conditions have been described [1]. These preclinical studies commonly applied CO systemically via (i) inhalation or (ii) using CO-Releasing Molecules (CORMs) [2]. The clinical use of these approaches, however, is challenged by a lack of practicability and substantial safety issues associated with the toxicity of high systemic doses of CO that are required for triggering therapeutic effects. Therefore, one rational of this thesis is to describe and evaluate strategies for the local delivery of CO aiming for safe and effective CO therapeutics of tomorrow. / Das Isoenzym Hämoxygenase 1 (HO-1) ist ein zentraler Bestandteil in der Aufrechterhaltung der zellulären Homöostase. Es wird durch zellulären Stress induziert und baut daraufhin Häm zu Kohlenstoffmonoxid (CO), Biliverdin und Fe2+ ab. Im Sinne eines lokalen Rückkopplungsmechanismus stößt es damit eine Vielzahl physiologischer Mechanismen mit anti-oxidativen, anti-apoptotischen und anti-inflammatorischen Effekten an, welche zumeist durch CO reguliert und durch ein komplexes Netzwerk aus Signaltransduktionsprozessen vermittelt werden. Es wurden zahlreiche Versuche unternommen, diesen als HO-1 / CO System bezeichneten Mechanismus nachzuahmen, um dadurch eine Behandlung von verschiedenen Krankheitszuständen zu ermöglichen. In diesen präklinischen Studien wurde CO regelmäßig systemisch (i) per Inhalation oder (ii) in Form von CO freisetzenden Verbindungen (CO-Releasing Molecules - CORM) verabreicht . Die klinische Anwendung dieser Strategien ist jedoch durch Sicherheitsrisiken erheblich erschwert, insbesondere durch die Toxizität der notwendigen hohen systemischen Dosen von CO. Entsprechend beschäftigt sich diese Dissertation unter anderem mit der Beschreibung und Evaluation von Strategien zur lokalen Verabreichung von CO, mit dem Ziel sichere und effektive Konzepte zu dessen Anwendung zu entwickeln.