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Title: The genetic toxicology of carcinogenic compounds
Author: Dempsey, R.
Awarding Body: University College of Swansea
Current Institution: Swansea University
Date of Award: 1987
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This thesis involved the development of a range of assay systems for the detection of environmental mutagens and carcinogens. Initially a protocol was optimised for the induction of mitotic gene conversion in stationary-phase cultures of the yeast Saccharomyces cerevisiae, strain JD1 following exposure to compounds which require exogenous metabolic activation, which involved an initial incubation at 37oC for 2 hours followed by a 16 hour incubation at 28oC. This protocol was found to be effective for the detection of cyclophosphamide and sterigmatocystin. In two separate studies, the activities of a total of 14 different compounds were then investigated in yeast using this, and other protocols involving exponential-phase cultures. In the first study, benzidine and diaminoterphenyl were detected, although, despite being structural analogues, their metabolic requirements differed. Dimethylaminoazobenzene and cyanodimethylaniline could not be detected under any of the conditions examined. In the second of these studies 8 carcinogens and 2 non-carcinogens were examined. Only one of the carcinogens, Acrylonitrile, was detected. The inactivity of the other 7 carcinogens was considered to be due to their ineffectiveness at inducing mitotic gene conversion. A third study indicated that respiratory status of the yeast strain used, had both quantitative and qualitative effects on the detection of sterigmatocystin, benzidine and diaminoterphenyl. Further studies were performed on two additional assays, chromosomal aberration induction and mammalian cell transformation, as these endpoints had proved very successful for detecting chemicals which were not readily detected in assays for other genetic endpoints. BZD was found to induce chromosomal abberrations in peripheral human lymphocyte cultures, in the absence of S9, which was in contrast to the activity detected in the yeast system. It was suggested that this was due to metabolic competence of the human lymphocyte cells. Studies on the stepwise transformation of Syrian hamster dermal cells, led to the suggestion of a model for the occurrence of aneuploidy events during this process, and their fixation at completion of transformation. The significance of this with respect to the observed occurrence of aneuploidy with cancer is discussed.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available