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Thesis (DTech (Biomedical Technology))--Cape Technikon, 2001 / Ionising radiation has the ability to induce, inter alia, DNA damage and is well established as a causative agent of carcinogenesis and mutagenesis. The effects of high doses of short duration have been well documented, whereas the effects of continuous exposure to low doses of ionising radiation have not, nor are they as clearly understood and current risk estimates are largely extrapolated from high-dose data of atomic bomb survivors. This study evaluated the clastogenic effects of low dose ionising radiation on a population of bats (Chiroptera) residing in an abandoned monazite mine. Bats were sampled from two areas in the mine, with external radiation levels measuring around 20 µSv/h (low dose) and 100 µSv/h (high dose). A control group of bats was collected from a cave with no detectable radiation above normal background levels. The most frequently encountered genetic event in human malignancy is the alteration of the p53 gene. Mutant p53 proteins have a longer half-life than the wild-type variant and accumulate to high levels in the nucleus of tumour cells. The study showed that not only was there a significant increase in p53 positive cells of radiation exposed bats, but also in the degree of positivity, especially in the cells lining the bronchioles of the lungs. Although experimental studies have shown that exposure to radiation may lead to the onset of fibrosis and an inflammatory response in the lung and other tissues, the magnitude of the dose exposure was not comparable to this study and histological examination of bat lung and liver tissues showed no morphological changes in radiation exposed bats when compared to the control group. It has been documented that chronic radiation exposures may give rise to a number of specific haematological defects which are collectively termed "preleukemia" or myelodysplastic syndrome. Full blood counts on bat samples showed a significant decrease in the MCV indicating microcytic erythrocytes from the radiation exposed bats. Differential counts performed on the peripheral blood of the bats showed a marked neutropenia. Neutrophils also showed marked dysplasia including psuedo-Pelger Huet cells in radiation-exposed bats. Cytochemical analysis using DAB myeIoperoxidase showed that control bats had hypogranular neutrophils andradiation-exposedbats had largely '1granularneutrophils. Bonemarrow biopsies were taken from both control and radiation-exposed bats and evaluated for ceIlularity, granulocyte: lymphocyte: erythrocyte (GLE) ratio and megakaryocyte morphology. A hypocelIular bone marrow, a decreased granulocytic haematopoeisis and dysplastic megakaryocyte morphology were observed in radiation-exposed bats. Mineralisation of bone osteoid was determined using image analysis and showed a highly significant decrease in the bone matrix from radiation-exposed bats. All haematological features observed are congruent with current literature describing secondary (radiation-induced) myelodysplastic syndrome.

Most breast cancer patients undergo radiation diagnostics and are also treated with radiotherapy. In addition to being an important treatment modality, ionizing radiation (IR) is a potent tumour-causing agent that has been linked to breast cancer development. However, the exact molecular etiology of IR-induced mammary gland carcinogenesis remains unknown. We set out to analyze the role of DNA methylation in mammary gland responses to low dose IR using a well-established rat model. We also studied low dose IR effects on global gene expression and microRNAome. We found that exposure to low, mammography-like dose of IR led to a significant loss of global DNA methylation in rat mammary gland tissue. Furthermore, low dose IR significantly affected rat mammary gland transcriptome and microRNAome. The datasets generated within the scope of this thesis may be used to identify novel predictive biomarkers for assessment of the magnitude of IR effects on mammary gland tissue. / xi, 120 leaves ; 29 cm

Ionizing radiation (IR), along with being an important diagnostic and treatment modality, is a potent tumor-causing agent, and the risk of secondary radiation treatment-related cancers is a growing clinical problem. Now some studies propose to link secondary radiation-induced cancers to an enigmatic phenomenon of bystander effects, whereby the exposed cells send signal damage and distress to their naïve neighbors and result in genome destabilization and carcinogenesis. Yet, no data existed on the bystander effects in an organ other than an exposed one. With this in mind, we focused on the analysis of existence and mechanisms of radiation-induced bystander effects in vivo. We have found that bystander effects occur in vivo in distant skin and spleen following half-body or cranial irradiation. These bystander effects resulted in elevated DNA damage, profound dysregulation of epigenetic machinery, and pronounced alterations in apoptosis, proliferation and gene expression. Bystander effects also exhibited persistency and sex specificity. The results obtained while using the animal model systems can potentially be extrapolated to different animals and humans. / xiii, 208 leaves : ill. ; 29 cm.

The purpose of this study was to evaluate the effectiveness of the database system used at the South African Radiation Control Authority and compare it with RAIS (Regulatory Authority Information System). A radiation regulatory authority requires an adequate and effective data management system in order to carry out its regulatory control program efficiently and effectively. RAIS is a comprehensive system that includes all of the main functionality required to support a regulatory framework. A mixed methods approach, including a quantitative descriptive comparative evaluation research study was conducted to determine if the database system currently used by the South African Radiation Control Authority is effective as a data management tool for a regulatory body. Two analyses were conducted. Firstly, the specification records of the South African database system were compared with that of RAIS. Secondly, current database users were surveyed by means of a structured questionnaire. Both analyses reveal that RAIS performs better than the Radiation Control database in the main areas of the regulatory framework. The study results also highlight some of the shortcomings and strengths of the Radiation Control database / Medical Informatics / M.A. (Public Health)

The purpose of this study was to evaluate the effectiveness of the database system used at the South African Radiation Control Authority and compare it with RAIS (Regulatory Authority Information System). A radiation regulatory authority requires an adequate and effective data management system in order to carry out its regulatory control program efficiently and effectively. RAIS is a comprehensive system that includes all of the main functionality required to support a regulatory framework. A mixed methods approach, including a quantitative descriptive comparative evaluation research study was conducted to determine if the database system currently used by the South African Radiation Control Authority is effective as a data management tool for a regulatory body. Two analyses were conducted. Firstly, the specification records of the South African database system were compared with that of RAIS. Secondly, current database users were surveyed by means of a structured questionnaire. Both analyses reveal that RAIS performs better than the Radiation Control database in the main areas of the regulatory framework. The study results also highlight some of the shortcomings and strengths of the Radiation Control database / Medical Informatics / M.A. (Public Health)

This study set out to examine the levels of galactic cosmic radiation exposure to Australian aircrew during routine flight operations, with particular attention to the high southern latitude flights between Australia and South Africa. Latitudes as high as 65?? South were flown to gain the data and are typical of the normal flight routes flown between Sydney and Johannesburg on a daily basis. In achieving this objective it became evident that suitable commercially available radiation monitoring equipment was not readily available and scientific radiation monitors were sourced from overseas research facilities to compliment my own FH4lB and Liulin monitors provided by UNSW. At the same time it became apparent that several predictive codes had been developed to attempt to model the radiation doses received by aircrew based on flight route, latitudes and altitudes. Further, it became apparent that these codes had not been subjected to verification at high southern latitudes and that they had not been validated for the effects of solar particle events. Initially measurements were required at the high latitudes followed by mid-latitude data to further balance the PCAIRE code to ensure reasonableness of results for both equatorial and high latitudes. Whilst undertaking this study new scientific monitors became available which provided an opportunity to observe comparative data and results. The Liulin, QDOS and a number of smaller personal dosimeters were subsequently obtained and evaluated. This appears to be the first time that such an extensive cross comparison of these monitors has been conducted over such a wide range of latitudes and altitudes. During the course of this study a fortuitous encounter with GLE 66 enabled several aspects of code validation to be examined, namely the inability of predictive codes to estimate the increased dose associated with a GLE or the effects of a Forbush decrease on the code results. Finally I review the known biological effects as discussed by numerous authors based on current epidemiological studies, with a view to high-lighting were the advent of future technology in aviation may project aircrew dose levels.