Medically Assisted Conception An Agenda for Research (1989) / Chapter Skim
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Regulative Potential of Micromanipulated Embryos
Regulative Potential of Micromanipulated Embryos
Pages 304-318
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From page 304... ...
At both Alar arm cellular levels, material Is being awed, subrace, or all for the a~li~nt of ~ as diverse as stying embryonic inaction and prying genetically superior agricultural animals. He growth of Ear biology has awed a new Tension to the venerable practice of , e _ .
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From page 305... ...
As a practical consideration, parti~,larly ~ the manipulation of human embryos, this regulative able ity allows come leeway in the varicose techniques associated with artificially desisted ccnosption. The fact that the embryo will be able to tolerate I-== than ideal conditions and still develop into a normal individual broadens the range of manipulations that can ethically be applied In mrerc~ainq infertility In humans.
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From page 306... ...
It is 1~oi~ evident foxy ex`~ri~ntal work that ctiff~rxxs in tinier are not ache anly distinctions arm that Eerbr~6 of different species with He sag cell ~ or at the same rrSholoai~1 stare mav be fi0ar~t~llv different in the Dee of —^~ - ~—- _ ~ ~ _ determination that has taken place and ache relative potential of blast~e P - Gelatin are cell Potential During Cleavage arm Blas~lation Be Trot Sargent test of ~11 F~rtia1 ~ whether an isolate rbryonic ~11 is totip~ent, that is, why it is Feeble of r~ulatir~ its devel~nt such that it can Agate for an overa:~1 reduction in Chronic ~~l ~ arm produce a viable off~prir~. It Nat be ,, ~ determined if any or all of the calls of an early embryo have this veracity in order to fully define regulation.
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From page 307... ...
, then this result ~ ght argue that all 4 blasts meres at the 4-cel1 stage do indeed retain totipotency. A high rate of survival of half embryos to term has been demonstrated for the 2-cel1 stage through the blasts cyst stage in sheep, and both haves of all of the stages have produced ic3~ti=1 twin offspring (Willadsen 1979, 1980; Gatica et al., 1984~.
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From page 308... ...
Little work he been polished on manipulation of ather darestic dies. In the horse, 3 offspring have been sport fmn bid 2-8 cell stages, altha ~ no twin pairs, and 4 offspring comprising 2 sets of twins have been obtained from isolated 4-cel1 blasts meres (Allen 1982; Allen & Pashen 1984)
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From page 309... ...
Other sties have pelvis eerie Hat Use half embryos adjust to a~r~imat=1y normal size by the 7th day of gestation (I£'wis & Rossant 1982~. In contrast, 18 day fetus ~ derived frail half embryos have been shown to weigh significantly lace than those fr=ul centrals (Tsuncda & MeLaren 1983~.
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From page 310... ...
m e proportion of ICM cells to fetal cells was determined for embryos of each group using a differential Eye method to distinguish between ICM and trophectoderm (Handyside & Hinter 1984~. A preli ~ comparison between half and control embryos for a given culture condition fits with the prediction that embryos with lower call rammer at the time of blastulation will have a lower ICM refill ratio and also with the prediction that a lcm ICE ratio will Case viability.
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From page 311... ...
Thus the increased neonatal loss can be explained as an indirect reproductive effect and not as a reflection of a decreased survival potential of mice developing frum half embryos.
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From page 312... ...
Sway of ache forcer acting on embryos to eliminate defective eribry~= or thy that have not successfully regulated will provide insight into Educible i~pr~ver~nts in t~niq~es for hartlling embryos of any species.
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From page 313... ...
1972. An investigation of inner cell mass and trophoblast tissues following their isolation Frau the mouse blastocyst.
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From page 314... ...
1982. l~ni= of size regulation In Norse ego abater.
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From page 315... ...
1982. Lineage analysis of inner aoll mace and trcphectoderm using micrcsurgi~lly reconstitubed mc use blastocysts.
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From page 316... ...
1981. me develc~Fzuent=1 capacitor of blasts fmn 4- art 8~l sheep Embryos.
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From page 317... ...
IRE 1: Curative call Numbers and Timing (Days Aster Fertilization) of Devel~ne (Modified f~ Pa~ioar~ and At, 1986)
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From page 318... ...
a Not ~e. b 10 pairs of twins have in produced follawir~ freezing of one half of eat pear c This figure represents only two twin pairs; (W;lladsen, 1980~.
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