Medically Assisted Conception An Agenda for Research (1989) / Chapter Skim
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II. Advances in the Practive and Science Base of Medically Assisted Conception
II. Advances in the Practive and Science Base of Medically Assisted Conception
Pages 25-65
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From page 25... ...
Developments in Human In Vitro Fertilization E1] Eastern Virginia Medical School, one of the premier centers for the clinical practice of in vitro fertilization, has a pregnant rate of 18.3 percent, bash on the Or of arcs used to stimulate the ovaries with either follicle stimulating hormone (ESH)
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From page 26... ...
m e donated eggs most often come from IVFET patients who have received hormonal stimulation and produced more eggs than necessary for their own use. Scmetimes, however, women who are to undergo a tubal ligation agree to ovarian stimulation before the surgery so that eggs can be harvested simultaneously.
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From page 27... ...
Failing the recruitment of mature oocybes, research is needed to develop reliable methods of maturing oocybes in vitro. All of these areas, if improved by I knowledge of the cell biology of early reproductive events, should greatly increase the ability to identify couples with high prnh~hility of sucks== and may increase the Cc rat== of IVFET in human clinical practice.
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From page 28... ...
Embryo freezing, in concert with embryo transfer, has been generally successful in terms of pregnancy rater. Freezing embryos allows for the s borage of rare breeds and preservation of a cattle surplus.
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From page 29... ...
these irxlude ornate maturation, Sperm morphology, the biochemistry of fertilization, cryopreservation, ovarian stimulation, and molecular genetics. In addition, topics such as membrane biochemistry, hormonal control of testicular and ovarian function, gene expression In early development, and the cell biology of implantation are identified as areas of exploration that would make major contributions to the sue of human and animal [VFET.
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From page 30... ...
In monkeys, one of four chemicals is administered in combination with human chorionic gonadotropin to stimulate ovulation. these are human mencQa~sa~ gonadotropin, human FSH, pregnant mare's serum gonadotropin, or porcine FSH.
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From page 31... ...
embryo transfer, has the potential to irx:rease directly the germ pool of desirable female traits by increasing the ember of offspring fray a Valerie cow. There are a nor of different; beaten non-human prima`; and clarestic anneals ~ the ways ovarian stimulation is a ~ Cliched.
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From page 32... ...
Unlike other animals, where PMSG acts as both FSH and EH receptors, In mares PMSG has only AH activity. Some success has been achieved in mares with administration of porcine FSH, especially if combined with human chorionic gonadotropin.
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From page 33... ...
Improved ultrasonography he= potential for increasing the I of superovulation in all species. As with parleys, developing ways to bypass the use of exogenous arc like MEG and porcine FSH weld be of enough ,~ in domestic animals.
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From page 34... ...
110: i~—~1= AL—~ "~D Vet "~`w`~ `~ - ~ · ire since He variants Leaves are fertile within ache bilayer. these interactions orderly 03 Rally immense range of biological r~ of c - 1 is including ~1 1~1 ir~eractioa=, r~r~ia~ signal premising, arm t~brane transport of nutrients or t=XinDReproductive events In which Crane biochemistry is of particular i~ortarx~e include sperm capacitation arm fusion of serum arm egg membranes for fertilization.
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From page 35... ...
m e potential applications of an increased ability to mature oocybes in vitro are numerous. As disr~=c-d earlier, such an ability would be of enormous value in the production of agria naturally important animals.
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From page 36... ...
for ache national arm international transportation of Abbe embryos. If proved safe for use In clinical practice, routine cry~prm;ervation of eggs or embryos ~d route ~tantia1ly the number of ti~; a An w ~ d have to ur~ergo hor ~ ne stim ~ ation, because the eggs harbored ~ could be frozen for later fertilization or fertilized in vitro and the extra embryos stored for future transfer.
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From page 37... ...
The tissue was then cooled to some intermediate subzero temperature before being rapidly cooled to the storage temperature of -196° C research with mouse ova showed that the cooling procedure ~~.=A~ could affect the survival rate important ways.
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From page 38... ...
each of which displays unique characteristic. Other ~11 types include Sertoli cells, which are nurse cells for the developing spermatogonia a ~ spermatocytes, and Leydig rolls, which relics the hormone testosterone, required for sperm maturation.
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From page 39... ...
Very little is known regarding the mechanists of interaction between developing sperm calls and the Or nurse cells, the Sertoli cells. Cell adhesion molecules have been found on spermatocytes that' some suggest, prcmcte continued meiosis of the spermatocytes bound to the Sertoli calls.
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From page 40... ...
ytic enzy ~ . The ~ fore, there seems to be strong evidence that Sertoli cell pro ducts greatly influence the development of sperm cells.
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From page 41... ...
However, whether or not the factors are ne-=cc~ry for follicular develc~rent-and normal ovarian physiology is not } ~ . the nest r ~ ear has been done on insul~n-like growth factors (IGFs)
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From page 42... ...
Finally, it is of utmost importance to relate the findings from in vitro studies to what is actually occurring in the natural state. AE~;sment of Gametes t63 There are many reasons why [VFET techniques in human clinical practice do not result ~ ongoing pregnancies one hundred percent of the time.
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From page 44... ...
IBM associated with these Ply unfertilized eggs lack this structural feature. Although the reasons for this failure in sper~/egg birdie are unarm, a Per of possible explanations are likely.
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From page 45... ...
For example, human development is sometimes arrested when the embryo reaches the four-ce11 stage. This may be due to a failure in the expression of embryonic genes that results in a lack of proteins required for further development.
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From page 46... ...
Cue way that has been ~ to examine sperm at different stages of maturation ~ the epidi~yrnis is to stain the cells with antibodies that Agonize particular sperm antigens.
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From page 47... ...
This information, in turn, could be used productively in two different ways: to promote fertility by learning how to mature sperm in Vl=O, or to promote contraceptive c3esrelc~ent by preventing Sperm maturation E~pecifica~ly. After ejaculation, sperm mast urn a so, anal final, maturation phase.
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From page 48... ...
Lit the antibodies against zone proteins discussed abjure, antibodies di~J against specific send proteins can also inhibit fertilization. me sperm protein M42, described earlier, that is altered Purim epidi~mal maturation is one of sev~ carxtidate In proteins for this purpose.
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From page 49... ...
oortin=1 granules, which certain enzymes that modify the zone pellucida, move to the egg membrane, fuse with it, and release their contents into the space between the egg and the zone pellucids. The released enzymes modify be ZP2 protein so that abreacts In can no beer hire to ZP2.
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From page 50... ...
Coincident with these ~ s, the zone pellucida degenerates. m e blastocyst, as the embryo is called at this time, can be considered to be a polarized structure in that the inner cell mass is attached to the try layer at one side of the blastocyst.
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From page 51... ...
Other pricks of ache citric acid cycle are E~r,; for the syr~es~s of Other m:,lecules. For ensemble, certain amino acids, which are the building blob; for proteins, are ford fmn the citric acid cycle.
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From page 52... ...
It was later found that maturing oocytes and embryos up to the 8-cell stage needed pyruvate and other citric acid cycle precursors to survive. While the exact requirements have been shown to differ from one animal species to another, it is inberesting that pyravate is often used in culture media for human and monkey eggs and early embryos despite the lack of experimental data to justify its Ace.
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From page 53... ...
A similar starvatior/refeeding experiment has suggested that the presence of pyruvate inhibits the formation of fructose 1,6, biphosphate from glucose and that the addition of glare=- resulted in no increase in the metabolizes of the citric acid cycle, whereas pyruvate did result In an Increase In these metabolites at all stages of embryonic development. There is much that should be known regarding the control of glycolys~s in oocytes and early embryos.
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From page 54... ...
For such diagnostic pr ~ es to be realized, he ~ Her, certain prerequisites are necessary. First, there must be a realistic chance of maintaining a pregnancy after embryo transfer.
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From page 55... ...
So, it seems fairly clear that, in the mouse, gene activity begins at this point. However, before pre~mplantaticn diagnoses can be achieved in humans, one must know the timing of human embryonic gene activity.
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From page 56... ...
Becky tile Objective of such remark was to develop p~i~plantation diagrx~tic techniques, Me pr~e of HI was also assayed Frau hen embryos. Unlike Me fifties ~ ~ mouse, there was a large variation in EM levels an human embryos am the massive rise ~ HEM at Me 8 cell stage Characteristic of the at of gene activity in Me Muse was not son in the human.
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From page 57... ...
File 65 Event of half embryos sunrive f`~ the 2~l stage, anly about 45 pi survive fern later stages. me Exam at later so may not Sean that all the cells are toting; rather, it may mean that each half embryo contain the r~ui~ ~ and type of ~11 to Deplete develc~nent.
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From page 58... ...
A reduction in the inner ~11 mass may then cause the Denise of scan half embryos. Is idea was tats directly by ark gram of skies that use diffe~ial stains to carfare the rumba of Ells in the Bar cell mass ~ me Gal namer of ~ is.
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From page 59... ...
In * seep art cattle, twenty to forty pen sent of the fertilized eggs do not survive and, in the pig, the Len rate is thirty to forty percent.
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From page 60... ...
After this labeling, investigators can then remove the uterus and maintain explants of it in culture. Using precursors for protein synthesis that have been radioactively labeled, investigators con label the new proteins synthesized and compare the patron of proteins fran ~lantati~ and non-iT~plan~tion site.
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From page 61... ...
Such a situation sets up potential problems in bringing nutrients to the developing embryo. Nutrients must be red from the endometrium and diffuse to the embryo.
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From page 62... ...
m e exact composition of the matrix varies from tissue to tissue, but it is important in the uterus since interactions between it and the blastocyst occur during implantation. For trqphoblast aggregation and membrane fusion to occur, there must be serum proteins in the culture media an4/or the dishes mast be coated with extra~lular matrix proteins.
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From page 63... ...
Cultured human trqphdblasts produce plasminogen activator (urokinase)
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From page 64... ...
Sum fit Cold be of great tt~ in ~star~ die- states like toxemia ~ which abnor~1 i~nrasi~ of trc~l~tic Owls is ~ to be a cam-. Finally, irnrestigators seo a real need for the institution of a national or ~ternaticmal r~isbry of IVEEr program to track the incidence of abr~rmal implantation and correlate thee data with the types of Ovarian stimulation petrols used and hormone lament therapy given.
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From page 65... ...
For additional information, of Braude, P.R., Bolton, V.N., and Mbore, S., Human gene expression first coats between the fair- arxI eightball stages of pre implantation development. Nature 332:459-461, 1988; and Saute, P.R., Bolton, V.N., ark J*
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