Word: eggs
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Dates: during 1970-1979
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Many scientists shared that surprise. For years they have talked about fertilizing the human egg in a test tube. But with every claim of success has come the inevitable countercurrent of doubt. Indeed as early as the 1940s, the eminent Boston gynecologist Dr. John Rock, a pioneer in development of the birth control pill, reported that he and colleagues had managed to fertilize an egg in vitro. But other scientists believe that the few cell divisions observed by Rock were nothing more than "parthenogenic cleavage" (division of the egg without the involvement of a sperm), probably induced by incidental stimulation...
...until the mid-1960s did researchers learn how to fertilize mammalian eggs in vitro on a regular basis. The groundwork was laid by M.C. Chang of the Worcester Foundation for Experimental Biology in Shrewsbury, Mass., and C.R. Austin of Cambridge University, who had solved the problem of in-vitro capacitation of rabbit sperm, a process that enabled sperm to penetrate the egg in the laboratory. Until then, the sperm were notably ineffectual in that role. But these early successes 'involved creatures no higher than rabbits, hamsters and mice...
...difficult field as are flasks, hormones and microscopes. Though man has wondered about human reproduction since the dawn of history, it remains, in many respects, as mysterious?some would even say as mystical?as ever. At birth, the infant human female is endowed with as many as a million egg cells, many more than she will ever need during her 30 or so child-bearing years. Starting at puberty, eggs are released, usually one at a time, about midway in the menstrual cycle. The process is intricate and marvelous. Stimulated by hormones, part of the body's chemical signaling system...
...fertilized egg continues its journey, dividing as it moves through the tube. Finally, after several days, it will have become a blastocyst, a hollow, ball-shaped cluster of fewer than 100 cells. By now, it will have reached the uterus. There the blastocyst embeds itself in the uterine wall, where it begins drawing nourishment from the mother and starts the miracle of differentiation: the rapid transformation of cells into tissue that soon becomes recognizable as heart, brain, muscle, kidneys and all the other components of a living, self-sufficient being...
...egg's journey is precarious. Unless the proper hor mones are present in appropriate concentrations, setting the stage for ovulation and fertilization, this intricate chain of events will not be initiated. The egg will not burst from the ovary, the cervical mucus will be too sticky for the entry of sufficient sperm into the uterus, and the lining of the uterus will not prepare to receive the fertilized egg. Indeed, hormonal disorders at any point in the sequence make it so fraught with peril for eggs and sperm that perhaps a third of all potential pregnancies end at the time...