Physiological Mechanisms of Conception—: an Inventory of Unanswered Questions

PHYSIOLOGICAL MECHANISMS OF CONCEPTIONAN INVENTORY OF UNANSWERED QUESTIONS* CARL G. HARTMAN More than 150 questions are proposed in this compendium. They represent hiatuses in our knowledge of reproductive processes of man and other mammals in particular. The questions evolved from the discussions in a conference on mechanisms concerned with conception which was held at West Point inJuly, 1959, under thejoint sponsorship ofthe Population Council1 and the Planned Parenthood Federation ofAmerica.2 Each ofthe eight groups ofquestions is the outcome ofthe material provided by an appropriate panel ofexperts, compiled and submitted to the participants in the conference for their additions and emendations. This comprehensive, albeit incomplete, survey of gaps in our understanding ofreproduction, assembled for the first time by thejoint efforts of many internationally known authorities, should serve several useful purposes. It offers a guide for investigators and, furthermore, for foundations and interested individuals wishing to help finance researches that could contribute directly to human welfare. In preparing this list, the panel does not wish to imply that investigative activity in these areas is entirely lacking. The processes ofspermatogenesis have been worked out in beautiful detail in the rat, for example, but most of the finer details are as yet lacking for man. The time relations and mechanism of sperm entry into the uterus have been clearly defined for the rat, the sow, and the cow, but no reliable corresponding details are understood for the human species. A third example relates to the physiology ofimplantation ofthe human fertilized egg; when this becomes as well * This paper is being independently published in theJournal ofReproduction and Fertility, London. 1 Population Council, Rockefeller Institute, New York 21, New York. 3 Planned Parenthood Federation of America, 501 Madison Avenue, New York 22, New York. 77 understood as the mechanism ofnidation ofthe rabbit embryo, it may be possible to regulate firm anchorage ofthe human embryo in those rather common cases where it now habitually fails. While additional financial aid would have significant effect on the effort to understand better the myriad unsolved problems of reproduction, a more important contribution would come from recruitment ofnew and imaginative ideas and new tools ofresearch. More research on the physiology ofreproduction would have a tremendous impact on the advance of knowledge in an area of science that, on the most sober and considered reflection, is ofutmost importance to the human race. No new institution need be established; there are hundreds of university laboratories and research institutes staffed with well-trained investigators and equipped with millions ofdollars ofapparatus. These laboratories and their scientists need financial aid to operate effectively, but the most important requirement is the need for more able people to bring their brains and skills to bear on studies that will enable man to regulate his capacity for reproduction. 1.Spermatogenesis i. Would it be possible to identify more precisely the steps in the development of spermatozoa? Can examination of spermatozoan development in other species be helpful in defining the process in man? 2.Several stages in the spermatogenic process are vulnerable to interference . Probably the most vulnerable are: (a) spermatogonial divisions; (b) maturation division of spermatocytes; (c) spermatid transformation (spermiogenesis); (d) detachment of spermatozoa from the Sertoli cells; (e) migration of spermatozoa into epididymis. What new antagonists might be developed for use at these several stages? 3.What mechanisms and/or factors impel the process ofdifferentiation of the cells which develop into spermatozoa? Can this be elucidated by studies oftestes regenerating after various treatments? 4.What are the physical characteristics and origin of the intercellular bridges in spermatocytes and spermatids? What is their function andhow might they be controlled? 5.What is the function ofthe Sertoli cells with respect to the various stages ofspermatogenesis? 78 Carl G. Hartman · Physiological Mechanisms ofConception Perspectives in Biology and Medicine · Autumn i960 6.What are the precise hormonal influences active in the various stages ofspermatogenesis? 7.What is the mechanism involved in depression of sperm count by heat applications to the testes? What cell types are affected? How do the mechanisms differ in different species? How do they differ with different degrees of heat? 8.What mechanism is involved in the inhibition of spermatogenesis Under conditions of inanition? 9.What are the...