Comparative Aspects Of Reproductive Failure

Comparative Aspects of Reproductive Failure

To many, the contents of this conference may not seem appropriate at a time when the minds are preoccupied with a "population explosion." To the participants and guests of this conference, however, this was a week of fascinating discussions. While quantitative aspects of reproduc tion were touched upon, it was mostly a search for an understanding of the qualitative aspects of reproduction and its failure. Only when we understand these more completely will it be possible to render optimum care and have the foundations for meaningful population control. The conference was conceived in discussions at the Committee on Pathology of the National Academy of Sciences, W"ashington, in 1965. It was felt that investigators in medicine and the veterinary fields would profit greatly from a closer liaison. All too frequently, we work relatively isolated in our respective fields and, with the burgeoning information filling our journals, we have not enough time and leisure to stand back and attempt a comparative look at the subject of study. Often we are not familiar with the techniques other disciplines use, and which we could well employ to great advantage. ,,yhile this applies to many aspects of medicine, a comparative approach to the study of reproductive failure seemed most advantageous at this time.

Comparative, Maternal, and Epidemiologic Aspects

Modification of embryonic development by genetic differences in the mother is a well-regcognized phemomenon, but little is known about the genet ics of these maternal traits or the mechanisms by which they act. To illustrate the genetic approach to the problem, examples are given of how differences in embryonic response to a teratogen can be partitioned into those resulting from differences in embryonic genotype (including the possible role of X-linked genes in producing reciprocal cross differences), maternal genotype, and cytoplasmically transmitted factors. The advantages and limitations of analysis by appropriate crosses, in utero treatments, embryo transfers, and in vitro experiments are illustrated. The numerous inbred strains of the mouse, with well-documented physiology, the recently developed recombinant inbred strains, and the existence of easily identified biochemical marker genes offer at tractive opportunities, so far largely unexploited, for causal analysis of mater nal effects on teratological responses. VII. ADDENDUM Since this chapter was written, several relevant papers have appeared. The strain difference between AI] and C57BU6] mice in frequency of cleft-palate response to cortisone was fitted to a model of normally distributed log tolerance (Biddle and Fraser, 1976). Genetic differences, both in maternal uterine environment and embryonic response, can be represented in terms of their effect on the median effective dose required for the cleft-palate re sponse. The maternal effect of AI] dams relative to C57BU6] dams caused a two-fold reduction in embryonic tolerance to cortisone-induced cleft palate.

Comparative Aspects of Reproductive Failure