Word: musts
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Dates: during 1970-1979
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...versity of Pennsylvania's Dr. Luigi Mastroianni, who has him self fertilized eggs in vitro but never attempted to implant them, points out that the British researchers had not provided any details about the condition of Mrs. Brown's fallopian tubes. "If they are completely absent," said Mastroianni, "you must accept the fact that the egg was fertilized in vitro. But if they are just damaged, there's always the possibility that the egg may actually have been fertilized in vivo [in the body] ? that the tubes may have functioned again." Sir John Stallworthy, president of the British Medical...
...despite the British team's long experience, the procedure had never resulted in a live birth. To bring it off successfully requires scientific ingenuity, surgical dexterity and, some might say, a lot of plain luck. The doctor must remove the egg at the exact moment in the monthly cycle when it has reached maturity. To ensure the success of that crucial initial step, Steptoe and Edwards follow a standard procedure for treating infertility: they administer fertility hormones, like those that have been responsible for the rash of multiple births in recent years. That encourages the ripening of several eggs...
Equally important, the sperm must be primed for fertilization or, in the technical term, capacitated. This means that the chemical inhibitors preventing the sperm from penetrating the egg must be removed from the surface of the sperm. How this trick is accomplished in the body remains a puzzle; some scientists think that the woman's secretions do the job. But in the lab, experimenters usually are able to prime the sperm simply by gently bathing them in a salt solution. There is also the critical matter of timing: neither eggs nor sperm have unlimited lifetimes, nor does the uterus remain...
Even after fertilization, doctors have no assurance that the egg will divide; again the culture medium must be carefully controlled. Some researchers think that the highest rate of success could be achieved if the content of the solution were continually altered as the cells go through stages of division. Finally, when the egg becomes a blastocyst or shortly before, it is ready for implanting. One way this can be done is by picking up the egg, which is still no bigger than the dot at the end of this sentence, with a tiny hollow tube, or pipette, then inserting...
...find that cloning mammals is a much more complicated affair. For one thing, mammalian eggs are one-tenth to one-twentieth the size of frog eggs and thus difficult to manipulate. And while tadpoles grow into frogs in a pond (and therefore easily in a laboratory tank), mammalian embryos must develop in a womb...