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Title: The analysis of chemically induced chromosomal aberrations in the germ cells of male and female mammals
Author: Albanese, R.
ISNI:       0000 0001 3409 9035
Awarding Body: CNAA
Current Institution: Open University
Date of Award: 1986
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A number of methods are currently used for the detection of chemically-induced chromosome damage but all are subject to the criticisms that they are either time-consuming and labour intensive or require a large number of animals and can be insensitive. However, for human risk-assessment, conclusive evidence that compounds possess potential heritable hazards can still only come from mammalian germ cell studies. Thus, there is a need for less demanding germ cell tests that may be used to identify potential germ cell clastogens. One such system involves the use of one-cell mouse embryos. Although not as well validated as the currently available germ cell assays i.e. the dominant lethal test (DLT) and the heritable translocation test (HTT), it has the advantage that both structural and numerical chromosome aberrations can be directly analysed. The aim of this thesis was to i) fully validate the one-cell embryo test system (analysing both male and female germ cell effects) with a number of model clastogens and spindle poisons and ii) investigate the fate/survival of these chemically induced aberrant one-cell embryos through to the F1 generation. Sexually mature male or female mice were administered test compound* as a single ip dose and then mated at different stages of gametogenesis; for males the whole of the spermatogenic cycle was sampled; for females preantral as well as antral/Graafian follicle stages were sampled. The afternoon after mating, one-cell embryos were recovered from mated females, cultured overnight in a mitotic inhibitor and then prepared for chromosomal analysis. In embryos derived from matings involving dosed males, only damage induced in the spermatid and spermatozoa was transmitted to the F1 progeny. There was no significant damage from the spermatocyte or spermatogonial stages. In embryos derived from females dosed with chemical clastogens only damage induced in the preovulatory Graafian follicle stage was transmitted. The survival of these chromosomally aberrant embryos was investigated by analysing 3-day and post-implantation embryos as well as weaned F1 progeny. These studies show that chromosomally aberrant embryos are able to survive up to at least the early post-implantation stages. At implantation and post-implantation stages, when the embryonic genome is required for continued development, those embryos with gross chromosomal aberrations (as induced by MMS, CYC, MMC and VIN) die. However, if the induced damage does not involve deletions and/or duplications of DNA (e.g. balanced reciprocal translocations - as induced by EMS) the embryo inheriting such aberrations will survive to term. One chromosomally aberrant F1 offspring was detected in this system. Thus, the analysis of one-cell embryos is a sensitive and precise method for the detection of mutagenic potential in mammalian germ cells and has the advantage that both structural and numerical chromosome aberrations can be directly analysed. Furthermore, the studies have shown it to be less costly and more sensitive than either the DLT or HTT. However, the technically demanding methods involved in the preparation of one-cell embryos prevents their use for routine screening purposes. *The model compounds selected were methyl methane sulphonate (MMS), ethyl methane sulphonate (EMS), cyclophosphamide (CYC), trenimon (TRN), mitomycin C (MMC), busulphan (BSN), hexamethyl phosphoramide (HMPA), 5-fluorouracil (5FU), colcemid (COL), vinblastine sulphate (VBS) and diethyl stilboestrol (DES)
Supervisor: Not available Sponsor: Imperial Chemical Industries plc, Department of Safety of Medicines
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Genetics