Chromosomal Abnormalities in Human Embryos

_NA_ru__ ~_v_o_L_~- 3 -~-MA__ v_'~- 3-----------------------NEWSANDVIEWS-------------------------------------2-~ Fertilization in vitro tremely high incidence of chromosomally imbalanced embryos to other work on fer tilization in vitro until more evidence is Chromosomal abnormalities in forthcoming. No one doubts that many such embryos conceived in vivo and in vitro , fail to develop to full term or even to human embryos implantation, and occasional trisomic, from R. G. Edwards monosomic and triploid abortuses have been reported after fertilization in vitro. CONVINCING and accurate data on the in found - a 47XY + D and another with There is a wealth of knowledge to be gained cidence of chromosomal abnormalities in metaphases apparently containing 44, 45 on the exact incidence and type of chromo human embryos growing in vivo or in vitro and 46 chromosomes respectively. This some disorders in early human embryos have been hard to gather. Difficulties have evidence was not unequivocal. There was conceived in various circumstances, for ex arisen in making clear and unequivocal some chromosome scatter from other ample in different age-groups of patients chromosomal preparations from the few metaphases in both embryos, and the and in various clinical conditions. 0 mitoses present in preimplantation em blastomeres were uneven in one of them. bryos, and the incidence of abnormalities Most embryos were unfortunately classi such as monosomy, trisomy, mosaicism fied by fluorimetry rather than karyotypes. R. G. Edwards is at the Physiology Laboratory, and polyploidy during these early stages of It would be premature to relate the ex- Downing Street, Cambridge. growth has not been established. There is nevertheless little doubt that these forms of Marine technology chromosomal imbalance could be very fre quent after fertilization in vivo or in vitro in some circumstances, for example in em bryos of older mothers. Boiling deep beneath the ocean The paper by Angell and collaborators in from Roger N. Anderson this week's Nature (p.336) reflects the dif ficulties found by others in establishing the IT is ironic that the oldest marine geological cold will precipitate a good coating on the correct karyotypes of cleaving human em technique has presented the most recent wall of a chimney. bryos. Most embryos could not be surprise from the mid-ocean ridges. High On the Mid-Ocean Ridge, this coating is classified, but two notable and novel obser technology has been responsible for a long made up of metals and, as Delaney and vations were made. Two of the eleven em series of discoveries that has remoulded our Cosens point out, boiling changes the kinds bryos observed were haploid or near ideas of how the sea floor cools at the of metal deposited as the hot spring fluid haploid, although one was classified only volcanically active Mid-Ocean Ridge. Bot billows forth. At some depth within a Mid by DNA microfluorimetry. The other was tom television, deep-sea drilling and deeply Atlantic Ridge chimney, boiling occurred undoubtedly gynogenetic or partheno towed remote-sensing packages have been in the past when the temperature of the hot genetic in origin, since the three classifiable the kinds of tool that first discovered, then water became high enough to intersect the mitoses were maternal 22X -17. This described, the 'Black Smoker' hot springs liquid-vapour phase transition curve. (If, remarkable embryo thus displayed two which pour forth 350°C metal-laden water however, hydro thermal fluid passing up a anomalies simultaneously, revealing a non onto the sea floor beneath up to 2 miles of chimney intersects the sea floor before disjunctional event in meiosis or im ocean. These hot springs, found active for reaching the P-T boiling curve, no steam mediately post-fertilization and an ability the first time in 1979, give us a glimpse of will occur:) The steam that then formed left of haploid embryos to reach the seven-cell how metal deposits, such as massive behind liquid of very high salinity, just as stage. It provides concrete grounds to con sulphides, are formed. the Great Salt Lake formed by evapora firm predictions that early human develop Now a technique used on HMS tion. Some of that liquid ended up as fluid ment can begin without fertilization - a Challenger to collect the first rock samples bubbles in the rock dredged, fortuitously, point for ethicists to ponder - and that from the deep sea floor of over 100 years millions of years later. monosomy might occur with some fre ago has delivered new scientific wonders. A But, what is really exciting is what quency in fertilized eggs. 'dredge' is merely a large bucket dragged Delaney and Cosens predict the steam car The implications of these observations blindly across the sea floor and connected ried to shallower parts of the chimney - for clinics working on human fertilization to the ship on the surface only by wire rope. gold and silver! In mines on land, lead, in vitro are less certain. We found no J.R. Delaney and B.A. Cosen (Mar. copper and zinc are found in the portion of haploid embryos among more than 25 ex Techno/. Soc. J. 16, 62; 1982) report inclu high-salinity chimneys deeper than the amined chromosomally, even though exact sions, or little bubbles, of super-high boiling and gold and silver are found in the counts could not be made in most of them. salinity water in basalts dredged from the steam-dominated shallow parts. But don't Eggs with one pronucleus are rare - very Mid-Atlantic Ridge. They conclude that get your pan out yet! There is probably no rare - during fertilization in vitro, boiling has taken place in the hot spring mother lode in the deep sea floor that any especially in comparison with the incidence system that generated the fluid inclusions. one could reach even with futuristic mining of haploidy reported by Angell et at. Their Boiling has never before been found equipment. But scientific tools such as methods might encourage the pathogenetic beneath the deep sea for the weight of two those which might be lowered into a deep activation of oocytes; for example, the use miles of water was thought to make it im sea drilling borehole or down a chimney by of nitrous oxide for the pneumo possible. a diving submersible might find a steam peritoneum during laparoscopy for oocyte For boiling to occur on the Mid-Atlantic vent where we could observe precious recovery, and conditions in the culture Ridge, hot spring water must move up metal deposits forming in situ for the first medium as oocytes are carried to a nearby wards from its heat source - magma time ever. Then we might learn of places on laboratory might contribute. Their un within a volcano - faster than it loses heat land to look- places we haven't thought yielding treatment of patients with clomi to the rock during its traverse to the sur tolookbefore. 0 phene, human chorionic gonadotropin and face. This requires a chimney, such as those ultrasound 19 hours later could lead to un observed by a diving submersible on the predictable follicular responses and the East Pacific Rise crest (Rise Project Roger N. Anderson is in the Lamont-Doherty collection of unripe oocytes. Group, 1980). Any good chimneysweep Geological Observatory of Columbia Two other unbalanced embryos were will tell you that hot vapour mixing with University, Palisades, New York 10964. 0028-0836/83/210283-02$01.00 <C> I 983 Macmillan Jnurnals Ltd .

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