An investigation of the teratogenic properties of human sera using a mammalian whole embryo culture technique.

Using the rodent embryo culture techniques of New (1978), it can be demonstrated that, over the 48-hours culture period, the in-vitro growth and development, of explanted 9.5 days old post-implantation rat conceptuses, in immediately-centrifuged and heat-inactivated homologous serum is almost indistinguishable from that which occurs in-vivo up-to 11.5 days. Moreover, using these methods, it has become possible to grow rat conceptuses in a culture medium made up of 90 per cent human serum supplemented with glucose and 10 per cent rat serum. Embryonic growth and developmental indices achieved in culture, using supplemented human serum, were reported to be comparable to those observed in whole rat serum (Reti et al., 1982). The successful growth of rat conceptuses during the major part of the organogenetic stage, is an important technical departure, since it enables the effect of potential teratogens, in human serum to be investigated. In order to validate the current embryo culture model, it was demonstrated initially that reproducible embryonic growth and development can be achieved in appropriately prepared serum samples, obtained from healthy women during the various stages of their menstrual cycles, pregnancy and the post-natal period. Furthermore, using serum from patients with ovarian malignancies, on antimitotic chemotherapy, it was demonstrated that the modified whole rat embryo culture model is highly sensitive in distinguishing between normal and embryotoxic human sera. This method of maintaining embryos in culture, was adapted to investigate the differences in the species specific embryopathic properties of valproic acid. This anticonvulsant agent, commonly used during pregnancy, was found to be embryopathic at a lower serum concentration in rats than in humans. The implications of these findings are discussed with a view to investigate potential embryotoxicity of drugs used during human pregnancy. Finally, sera from women with histories of neural tube defect (NTDS) affected pregnancies and those with unexplained recurrent miscarriages were used as a culture medium to investigate serum related environmental embryopathic factors. Experimental work reported in this thesis indicates, that culture of rat conceptuses in appropriately prepared sera from 76 per cent of women with NTD affected pregnancies and 25 per cent of the habitual aborters resulted in an abnormal growth