Expression of intercellular junctions during preimplantation development of the human embryo

A total of 74 human embryos were stained with gap junction protein specific anti-peptide antibodies an antibodies to the desmosomal protein desmoplakin to reveal the expression pattern of intercellular junctions during preimplantation development. Prior to implantation, the human embryo expresses predominantly connexin (Cx43)-containing gap junctions. Gap junctions were first detected in apposing cell membranes at the 4-cell stage and became increasingly organized as development proceeded. In normal blastocysts, trophectoderm (TE) cells were linked by dense arrays of gap junctions while inner cell mass (ICM) cells were linked by small, punctate gap junctions. Gap junctions containing Cx32 or Cx26 were observed occasionally in the TE of late blastocysts. Desmosomes appeared between outer cells prior to cavitation and were retained in the TE, but not in the ICM. Levels of gap junction protein expression were variable in morphologically normal embryos at the same stage, suggesting that a normal appearance may not be a reliable indicator of future viability. Morphologically normal embryos often possessed multinucleate, apoptotic and decompacting cells. They could show either extensive, disorganized over-expression or reduced expression of gap junction protein. The results fit the view that only embryos destined to survive display an organized pattern of intercellular junctions.

[Effects of blastocyst deficiencies induced by aspirin treatment during preimplantation period in rats on development of embryos after implantation]

Pregnant rats were treated orally with aspirin 0.5 or 1.0 g.kg-1 on d 3 (positive vaginal smear was considered as d 0) and were sacrificed on d 4. Some blastocysts collected on d 4 were evaluated for gross morphology and cell number, and the remainings were transfered into pseudopregnant rats. Results showed that the rate of blastocysts with abnormal morphology were 23.8% and 40.8%, respectively, in 0.5 and 1.0 g.kg-1 of aspirin. These were significantly higher than 6.8% of the control group. The cell number of blastocysts also decreased in the aspirin groups. The rate of implantation and live fetuses in the case of blastocysts with normal morphology were related negatively with the aspirin doses, espesially in the group of 1.0 g.kg-1 of aspirin, the implantation rate was significantly lower (38.6%). However, the implantation rate of blastocysts with abnormal morphology in both groups of aspirin were much less than that of the control group, and all embryos after implantation were resorped. No significant malformations were observed in the live fetuses. These results suggests that the effects of blastocyst deficiencies induced by aspirin on development of embryos transfered into pseudopregnant rats mainly caused death of embryos, but not malformation of fetuses.

Assessment of developmental retardation and abnormality of in vivo produced preimplantation embryos in rat

In most mammals studied, a substantial numbers of preimplantation embryos are believed to be lost in vivo. In vitro, embryos develop slowly and lose viability. Hence, there is a need to assess the extent and cause of embryonic loss both in vivo and in vitro. In this study, we assessed the quality of in vivo produced ovulation products/embryos, recovered on days 1-5 pregnancy, from naturally bred wistar rats. From day 1 pregnant rats (n = 24), 226 ovulation products were recovered which included 52% (117) unfertilized oocytes and empty zonae with/without cell debris (UFO-EZ:CD) and 48% (109) 1-cells. Flushings of day 2 rats (n = 27) contained 229 ovulation products, consisting of 70% (160) 2-cells and 30% (69) UFO-EZ:CD. Flushings of day 3 rats (n = 27) had 23% (56) 2-cells, 6% (15) 3-cells, 23% (57) 4-cells, 1% (2) 5-7 cells, 2% (5) 8-cells and 45% (112) UFO-EZ:CD, total being 247. Flushings of day 4 rats (n = 28) had 193 ovulation products comprising of one morula, 45% (86) 8-cells, 5% (9) 5-7-cells and the rest were 4-cells (2), 3-cells (2), 2-cells (1) and 48% (92) UFO-EZ:CD. Day 5 flushings (n = 27) had 202 ovulation products which included 13% (27) morulae, 17% (34) early, 36% (73) mid and 2% (5) late blastocysts; additionally, 4-cells (1), 8-cells (2) and 30% (60) UFO-EZ:CD were also recovered. On day 4, embryos (8-cells) migrated from the oviduct to the uterus. When pregnant rats (n = 25) were allowed to term, only 15 females (60%) delivered pups (128) with variable litter size (2-12). These results indicate that 56% (619/1097) of recovered rat preimplantation embryos are of expected developmental age with a mixture of asynchronously cleaving embryos. The remaining 44% (478) is comprised of 38% (417) UFO-EZ:CD and 6% (61) abnormal and developmentally retarded embryos, which are unlikely to produce viable pups at term.

The use of fluorescent in-situ hybridization (FISH) for the analysis of in-vitro fertilization embryos: a diagnostic tool for the infertile couple

We use triple colour fluorescent in-situ hybridization (FISH) to sex human embryos for preimplantation diagnosis of X-linked disease, to analyse chromosome numbers in embryos donated for research purposes and as a diagnostic tool for patients undergoing infertility treatment, especially in cases where abnormal embryo development occurs. We have reported on the use of FISH in a case where all embryos showed accelerated cleavage. Here we report on the use of triple colour FISH in a case where five out of seven oocytes were multi-nucleated when examined for pronuclei. The embryos were spread whole using HCl/Tween 20 and triple colour FISH performed with probes for chromosomes X, Y and 1 in a 2 h procedure. Two embryos were normal for the probes used, and three showed abnormalities, including one 4-cell embryo where all nuclei were X,X,X,Y,1,1,1,1. FISH indicated that fertilization had occurred, but that the majority of embryos were abnormal confirming that such embryos should not be considered for transfer. In these cases, or where there is recurrent in-vitro fertilization failure or spontaneous abortions, embryos in future cycles can be examined using FISH to ascertain the level of chromosome abnormality which may aid future infertility treatment.

Developmental analysis of the Hba(th-J) mouse mutation: effects on mouse peri-implantation development and identification of two candidate genes

The Hba(th-J) mouse mutation is a deletion on chromosome 11 that spans the alpha-globin complex and causes alpha-thalassemia in heterozygous animals and in utero death of embryos homozygous for the deletion. We hypothesised that one or more genes closely linked to the Hba locus are also deleted in these mutant mice and that deletion of these additional genes is responsible for the embryo lethality. We have analysed the developmental profile of mutant embryos using a PCR assay to distinguish homozygous embryos from wild-type and heterozygous embryos. No homozygous embryos are detectable on Day 6.5 of gestation and morphological analysis of embryos on Day 5.5 shows that both the embryonic and extraembryonic ectoderm of the egg cylinder are reduced in size and contain degenerate cells. Preimplantation homozygous embryos are morphologically normal with the same proportion developing to the blastocyst stage as control embryos. However, the cell number of homozygous embryos on Day 4.5 is significantly reduced due predominantly to a decrease in the cell number of the trophectoderm and not the inner cell mass. When homozygous blastocysts are plated in vitro, outgrowth of giant trophectoderm cells appears similar to that of wild-type embryos but outgrowth of the inner cell mass is affected. Cells from the inner cell mass of homozygous embryos appear to undergo necrosis and dissociate from the trophectoderm outgrowth after 3 to 4 days in culture. These studies demonstrate that the development of both the inner cell mass and the trophectoderm of embryos homozygous for the Hbath-J deletion is affected by the mutation. We have used quantitative Southern blotting to show that 3-methyladenine glycosylase (mpg) and dist1, two genes closely linked to the Hba locus on chromosome 11, are also deleted in this mutation. Reverse transcriptase-polymerase chain reaction analyses demonstrate that mpg and dist1 are normally expressed by preimplantation and early postimplantation embryos, whereas alpha-globin transcripts from the Hba locus are not detected until Day 7.5 of gestation. These studies demonstrate that deletion of the mpg or dist1 genes is likely to be responsible for the homozygote embryo lethality and the potential roles of these gene products in early embryogenesis are discussed.

Deletion of beta 1 integrins in mice results in inner cell mass failure and peri-implantation lethality

Integrin receptors for extracellular matrix receptors are important effectors of cell adhesion, differentiation, and migration in cultured cells and are believed to be critical effectors of these processes during development. To determine when beta 1 integrins become critical during embryonic development, we generated mutant mice with a targeted disruption of the beta 1 integrin subunit gene. Heterozygous mutant mice were normal. Homozygous loss of beta 1 integrin expression was lethal during early postimplantation development. Homozygous embryos lacking beta 1 integrins formed normal-looking blastocysts and initiated implantation at E4.5. However, the E4.5 beta 1-null embryos in situ had collapsed blastocoeles, and whereas the trophoblast penetrated the uterine epithelium, extensive invasion of the decidua was not observed. Laminin-positive endoderm cells were detected in the inner cell mass area, but endoderm morphogenesis and migration were defective. By E5.5 beta 1-null embryos had degenerated extensively. In vitro analysis showed that trophoblast function in beta 1-null peri-implantation embryos was largely normal, including expression of tissue-specific markers, and outgrowth on fibronectin- and vitronectin-coated, although not on laminin-coated substrates. In contrast, the inner cell mass region of beta 1-null blastocyst outgrowths, and inner cell masses isolated from beta 1-null blastocysts, showed highly retarded growth and defective extraembryonic endoderm morphogenesis and migration. These data suggest that beta 1 integrins are required for normal morphogenesis of the inner cell mass and are essential mediators of growth and survival of cells of the inner cell mass. Failure of continued trophoblast development in beta 1-null embryos after inner cell mass failure could be attributable to either an intrinsic requirement for beta 1 integrins for later stages of trophoblast development, or to the lack of trophic signals from the beta 1-null inner cell mass.

Proliferation of blastomeres from biopsied cleavage stage human embryos in vitro: an alternative to blastocyst biopsy for preimplantation diagnosis

Normally fertilized human embryos were biopsied at cleavage stages on the third day after in-vitro fertilization (IVF). One or two blastomeres at the 8-cell stage were removed and co-cultured with the biopsied embryos. Embryos and blastomeres were assessed daily for morphological development until day 6, when the number of cells were counted by labelling the nuclei. In all, 53% of the biopsied embryos (25 out of 47) reached the blastocyst stage between day 5 and 6 and the proportion was the same irrespective of the number of cells removed. There was no significant difference between biopsied embryos from which one or two blastomeres respectively had been removed with regard to total cell numbers at the blastocyst stage (56.2 +/- 3.0 and 64.7 +/- 5.5), number of trophectoderm (45.4 +/- 3.5 and 44.0 +/- 5.7) and inner cell mass cells (14.0 +/- 1.2 and 16.6 +/- 1.8). Overall, 72% of the isolated blastomers divided at least once over 3 days in culture and 50% divided more than once. The mean overall cell number after 3 days in culture was 3.7 +/- 0.48 per blastomere (range 1-8 cells) if one cell was removed and 6.9 +/- 1.0 if two cells were removed. If the undivided blastomeres are excluded, the mean cell number was 4.8 +/- 0.51 and 8.3 +/- 1.0 respectively. Over this period, 55% of the blastomeres cavitated. Of the blastomeres taken from embryos that developed to the blastocyst stage, 92% divided and 76% cavitated. In those from arrested embryos, 50% divided (P < 0.002) and 32% cavitated (P < 0.003).(ABSTRACT TRUNCATED AT 250 WORDS)

Preimplantation genetic diagnosis for Tay-Sachs disease: successful pregnancy after pre-embryo biopsy and gene amplification by polymerase chain reaction

OBJECTIVE

To determine the ability to apply preimplantation genetic diagnostic techniques to screen for and prevent Tay-Sachs disease (TSD).

DESIGN

A couple, both carriers for the 4 base pair (bp) insertion in exon 11 of the beta-hexosaminidase A gene, which results in TSD, underwent IVF, pre-embryo biopsy, polymerase chain reaction (PCR) DNA amplification of the biopsied blastomeres, and pre-embryo transfer. One to two blastomeres were aspirated using a biopsy pipette that was inserted through an opening in the zona formed with acidified phosphate buffer. Polymerase chain reaction was performed on the individual blastomeres for 20 cycles followed by an additional 30 cycles using nested primers. This yielded amplified DNA products of 272 and 276 bp for the normal and mutant gene, respectively. Heteroduplex formation was used for identification of normal, homozygous affected, and heterozygous pre-embryos.

RESULTS

Seven of 13 oocytes fertilized normally and were biopsied at the four- to eight-cell stages. Deoxyribonucleic acid amplification occurred in four of seven pre-embryos (one homozygous affected and three homozygous normal pre-embryos). The three normal pre-embryos that continued to cleave after biopsy were transferred on the evening of day 3 after retrieval. Subsequently, a single gestational sac was observed and the genetic diagnosis was confirmed at amniocentesis.

CONCLUSION

A successful pregnancy and birth were accomplished after preimplantation genetic diagnostic screening for the prevention of TSD.

Increased incidence of aberrant morphological phenotypes in human embryogenesis--an association with endometriosis

PURPOSE

After noticing specific aberrant forms of development in preimplantation embryos from women with endometriosis, we embarked upon this study in order to examine the frequency of these events as compared with controls.

METHODS

A total of 235 embryos representing 30 women undergoing 56 cycles of in vitro fertilization were retrospectively analyzed on videotape and placed into categories based upon the incidence of specific morphological criteria found during observations made on the first and second days following oocyte retrieval.

RESULTS

Several of the aberrant nuclear and cytoplasmic events were found to be statistically increased in the group of embryos from women with endometriosis.

CONCLUSIONS

The incidence of defined aberrant phenotypes in embryos from women with laparoscopically documented endometriosis may allow us to identify specific embryotoxic events with reference to endometriosis and other diagnoses.

Is spontaneous resorption in the DBA/2-mated CBA/J mouse due to a defect in "seed" or in "soil"?

PROBLEM

Recurrent spontaneous resorption in DBA/2-mated CBA/J mice has been attributed to damage by NK-lineage cells and TNF-alpha beginning several days after implantation. However, some recent data have suggested CBA/J female mice have a high proportion of preimplantation embryo abnormalities resulting in defective in vitro implantation and impaired trophoblast outgrowth. Could spontaneous abortion be due to a defective embryo ("seed") rather than a hostile post-implantation uterine lining ("soil").

METHOD

Mated CBA/J females were manipulated so as to have high spontaneous abortion rates and a high percent abnormal embryos, or low resorption rates and a low percent abnormal embryos. Embryos from low aborting females were transferred into high aborting female recipients that were pseudopregnant, and vice versa.

RESULTS

Abnormal embryos from females with high abortion rates implanted in low aborting females and did not show any greater tendency to resorb than normally developed embryos in these recipients. By contrast, normal embryos to some extent and abnormal embryos to a much greater extent, gave a high abortion rate when the recipient female was a high aborter.

CONCLUSION

Properties of the "soil" into which embryos implant determines the likelihood of success or failure (abortion). Abnormal pre-implantation embryos can be "rescued" by "good soil"; "sick soil" damages both normal and abnormal embryos. Defining the cellular and molecular mechanisms may be useful in understanding basic mechanisms leading to aborting and nonaborting pregnancy.

Developmental potential of microbiopsied murine blastocysts

OBJECTIVE

To evaluate the frequency of mouse pups born following blastocyst biopsy and embryo transfer compared to nonbiopsied controls.

METHODS

ICR Swiss albino and C57B1/6 mice served as embryo donors. Pregnant mare serum gonadotropin treatment was followed 46-52 hours later by hCG, when donors were paired with fertile males. Mating was confirmed the following day and embryos were collected on the afternoon of day 4. After overnight culture, hatching trophoblast was excised by micromanipulation with a fine-pulled glass pipette. Embryos (206 controls, 206 biopsied) were transferred to 26 pseudopregnant recipients. Alternate mouse strains were used to identify pups born from control or biopsied embryos.

RESULTS

The end point was percentage of pups born ((number born/number transferred) x 100), using angular transformation before analysis. There was no significant difference (P > .1) between percent live-born in control (27.7%) or biopsied (34.5%) embryos, nor were there any strain differences.

CONCLUSION

These data support the hypothesis that the developmental potential of murine blastocysts is not affected adversely by the biopsy procedure.

In vitro study of the carry-over effect associated with early diabetic embryopathy in the rat

Embryos were recovered from diabetic rats on day 5 of pregnancy and incubated in vitro for up to 72 h. Compared to control embryos, blastocysts from diabetic rats showed a marked impairment in growth that resulted at 48 h in a higher rate of degeneration and a lower morphological score in the developing population. After 72 h in vitro, fewer developing blastocysts from diabetic rats formed trophoblastic outgrowths and fewer of those implanted developed an inner cell mass when compared with the control group. When assessed for their cell content, blastocysts from diabetic rats contained fewer cells than control embryos at the start of the culture. This difference persisted, and even worsened, during the ensuing incubation period. The increasing cellular deficiency in blastocysts from diabetic rats was primarily located to their inner cell mass lineage but trophoblast growth was also affected. When trophoblast outgrowths were compared for their surface area and number of nuclei, those collected from diabetic rats were smaller, contained fewer nuclei and had a higher proportion of giant nuclei than control outgrowths. Our data thus demonstrate that despite their removal from the abnormal intra-uterine environment, blastocysts from diabetic rats remain functionally affected by their early exposure and fare less well than control embryos cultured under the same standard conditions.

Chromosome abnormalities in human arrested preimplantation embryos: a multiple-probe FISH study

Numerical chromosome abnormalities were studied in single blastomeres from arrested or otherwise morphologically abnormal human preimplantation embryos. A 6-h FISH procedure with fluorochrome-labeled DNA probes was developed to determine numerical abnormalities of chromosomes X, Y, and 18. The three chromosomes were stained and detected simultaneously in 571 blastomeres from 131 embryos. Successful analysis including biopsy, fixation, and FISH analysis was achieved in 86.5% of all blastomeres. The procedure described here offers a reliable alternative to sexing of embryos by PCR and allows simultaneous ploidy assessment. For the three chromosomes tested, numerical aberrations were found in 56.5% of the embryos. Most abnormal embryos were polyploid or mosaics, and 6.1% were aneuploid for gonosomes or chromosome 18. Extrapolation of these results to all human chromosomes suggests that the majority of abnormally developing and arrested human embryos carry numerical chromosome abnormalities.

Direct assessment of the rate of chromosomal abnormalities in grade IV human embryos produced by in-vitro fertilization procedure

During in-vitro fertilization (IVF) procedures, human preimplantation embryos were classified into four grades according to their morphological appearance under light microscopy. The grade IV group included poor quality embryos. In our IVF programme, these embryos were never transferred or frozen, and were thus available for cytogenetic analysis. Cytogenetic analysis was performed on 411 grade IV embryos from 327 couples participating in the IVF programme. A total of 118 embryos were successfully karyotyped using at least one metaphase. Normal diploid chromosomes were found in only 12 embryos, containing a total of 19 metaphases. All others (90%) showed abnormal or aberrant chromosome complements; 48 were aneuploid and six cases of single chromatids were noted; 14 embryos (11.8%) contained haploid complements, while the remaining 44 exhibited mosaics (2n/3n, n/2n, n/3n) or fragmented chromosome sets. Also, several structural aberrations and rearrangements were observed. These results indicate that the large majority of grade IV human embryos are chromosomally abnormal. This confirms the morphological assessment of the poor quality of these embryos and demonstrates the uselessness of both the transfer and the cryopreservation of grade IV embryos.

Biopsy of the human blastocyst and polymerase chain reaction (PCR) amplification of the beta-globin gene and a dinucleotide repeat motif from 2-6 trophectoderm cells

Cultured human blastocysts have been biopsied on day 5-6 post insemination and 2-6 extra-embryonic cells from the trophectoderm were removed and their DNA subjected to specific amplification by the polymerase chain reaction (PCR). Simultaneous amplification of part of the beta-globin gene and a dinucleotide repeat sequence has been achieved in a high percentage of cases when using the DNA from both trophectoderm cell biopsies and biopsied blastocysts as template for the PCR. A similar success rate was achieved when serial biopsies were taken from the same blastocyst, thus allowing one cell sample to be held in reserve for use should equivocal results be obtained. Over the entire experimental period (5 months), no contamination was experienced with biopsy or PCR procedures. Following biopsy of the trophectoderm cells all blastocysts had reformed a blastocoele cavity within 3-4 h of the biopsy procedure. Those blastocysts remaining in culture after this time showed a high incidence (78-83%) of hatching and outgrowth.

Association of ultrarapid freezing of mouse oocytes with increased polyploidy at the pronucleate stage, reduced cell numbers in blastocysts and impaired fetal development

Mature mouse oocytes were frozen ultrarapidly with a cryoprotectant solution consisting of 3.5 mol dimethylsulfoxide l-1 and 0.5 mol sucrose l-1 or exposed to the freezing solution and recovered. Freshly collected oocytes were used as controls. After ultrarapid freezing and thawing, a high mean percentage of oocytes (78%) survived. The incidence of parthenogenetic activation in frozen-thawed oocytes was not increased. After insemination in vitro, the rate of two-cell formation was decreased (59% versus 69%). Examination of the chromosome complement of first-cleavage embryos revealed that the incidence of polyploid embryos was four times that of the control group (23% versus 6%). Fewer fertilized eggs progressed to the blastocyst stage (49% versus 81%) and the mean number of cells per blastocyst was decreased. Furthermore, the capacity of transferred blastocysts to develop in vivo was reduced. Autopsy at day 17 of gestation revealed that the proportion of embryos implanting was lower in the embryos derived from ultrarapidly frozen-thawed oocytes. Furthermore, some of the living fetuses were abnormal, but our sample size is too small for the effect to be significant. In the solution control group, no differences were found compared with the control group. Although the study needs further results to draw definite conclusions, our findings question whether the applied protocol is suitable for mouse oocytes.

Trophectoderm microbiopsy in murine blastocysts: comparison of four methods

PURPOSE

This study compares four trophectoderm microbiopsy techniques for removal of blastomeres from murine blastocysts: (1) aspiration, trophectoderm pipetted through the zona; (2) incision, trophectoderm excised with a microrazor; (3) slit/excision, the zona slit and herniating trophectoderm excised; and (4) hatch/excision, trophectoderm cells excised after spontaneous hatching.

RESULTS

Murine blastocysts were comparatively biopsied using one of four methods and contrasted to zona slit and nonmicromanipulated controls. Operative cellular injury was assessed by uptake of fluorescein isothiocyanate (FITC). Postoperative embryonic viability was assessed by blastocoele reexpansion and hatching inner cell mass development and trophectoderm plating. All techniques yielded cells available for genetic analysis.

CONCLUSIONS

The slit/excision technique and hatch/excision techniques exhibited lower operative injury and the higher postoperative viability than aspiration or incision. The slit/excision and the hatch/excision techniques, though requiring two operative steps, appear to be the least damaging of the four methods. Therefore, they should be most applicable to human blastocysts obtained either by extended culture in vitro or by uterine lavage.

Embryo biopsy strategies for preimplantation diagnosis

OBJECTIVE

To analyze different biopsy methods, embryo stages, and cellular masses that can be removed for preimplantation diagnosis of genetic diseases to find optimal biopsy conditions compatible with the subsequent development of the conceptus, the acquisition of intact viable blastomeres, and the reliability of the genetic analysis.

DATA IDENTIFICATION

The most important published studies have been identified through a computerized bibliographical search (MEDLINE; Dialog, Palo Alto, CA).

STUDY SELECTION

Studies reporting different embryo biopsy methods practiced at different stages have been selected.

RESULTS

The analysis carried out in the current review shows, at the present time, the following: [1] the displacement and push methods may be more suitable than the stitch and pull and aspiration (puncturing the zona pellucida) approaches at cleavages stages; [2] the aspiration and stitch and pull procedures may assure higher success rates than the herniation procedure at the blastocyst stage; [3] the mechanical division method and the use of acid Tyrode's solution would not be advisable before the eight-cell stage; [4] human embryos at the two-cell and blastocyst stages may not be suitable for preimplantation diagnosis because of an excessive reduction of cellular mass at the two-cell stage and a low or zero pregnancy rate after transfer at the blastocyst stage; and [5] biopsy of a quarter of the embryonic cellular mass on day 2 after insemination may increase biochemical pregnancies if the cleavage rate is not preserved.

CONCLUSIONS

At the present time, biopsy of a quarter of the embryo on day 3 after insemination may be the most feasible approach for preimplantation diagnosis.

The cleavage rate of digynic triploid mouse embryos during the preimplantation period

Triploidy is a lethal condition in mammals, with most dying at some stage between implantation and term. In humans, however, a very small proportion of triploids are liveborn but display a wide range of congenital abnormalities. In particular, the placentas of human diandric triploid embryos consistently display "partial" hydatidiform molar degeneration, while those of digynic triploids generally do not show these histopathological features. In mice, the postimplantation development of diandric and digynic triploid embryos also differs. While both classes are capable of developing to the forelimb bud stage, no specific degenerative features of their placentas have been reported. Diandric triploid mouse embryos are morphologically normal while digynic triploid mouse embryos consistently display neural tube and occasionally cardiac abnormalities. Previously it was shown that the preimplantation development of micromanipulated diandric triploid mouse embryos was similar to developmentally matched diploid control embryos. In this study, the preimplantation development of micromanipulated digynic triploid mouse embryos is analysed and compared with that of diandric triploid mouse embryos in order to determine whether there is any difference in cleavage rate between these two classes of triploids. Standard micromanipulatory procedures were used to insert a female or a male pronucleus into a recipient diploid 1-cell stage embryo. The karyoplast was fused to the cytoplasm of the embryo by electrofusion. These tripronucleate 1-cell stage embryos were then transferred to pseudopregnant recipients and, at specific times after the HCG injection to induce ovulation, the embryos were recovered and total cell counts made. These results were plotted and regression lines drawn.(ABSTRACT TRUNCATED AT 250 WORDS)

Development of in vitro fertilized mouse embryos exposed to ethanol during the preimplantation period: accelerated embryogenesis at subtoxic levels

This study examined the effects of ethanol (EtOH) on mouse preimplantation development using an in vitro culture method. Embryos at the 1-cell, 2-cell, or 4-cell stage were exposed for 24 h to medium containing EtOH, then further cultured without EtOH to determine their ability to form blastocysts and to eventually hatch from the zona pellucida. EtOH exposure either arrested or enhanced normal development, depending on dose and embryonic stage of exposure. Exposure of 1-cell and 2-cell embryos to 1.6% (w/v) EtOH decreased blastocyst formation and hatching, and exposure of 1-cell embryos to 0.4% EtOH inhibited their development. At 0.1%, EtOH had an opposite effect, causing an increase in the percent blastocyst formation of treated 1-cell and 2-cell embryos. Neither inhibition nor stimulation of blastocyst formation occurred in 4-cell embryos exposed to 0.1-1.6% EtOH. Using an in vitro outgrowth model of implantation, embryos that reached the blastocyst stage were further tested for their ability to produce differentiated trophoblast cells. Blastocysts previously exposed to 0.1% EtOH during the 1-cell stage appeared to form adhesive trophoblasts earlier than control embryos, indicating that EtOH exposure can induce precocious differentiation of the trophoblast cells. The EtOH treated blastocysts contained significantly more cells than control blastocysts. These results indicate that EtOH can alter preimplantation development by either inhibiting or accelerating cell growth and differentiation.

Preimplantation genetics and recovery of fetal cells from maternal blood

Advances in molecular genetics have made possible advances in two new areas of prenatal diagnosis. Preimplantation genetic diagnosis is being explored through polar body biopsy, biopsy of the single cell from the eight-cell embryo, and trophectoderm biopsy of the blastocyst. There are attractive theoretical advantages to the last approach. However, assessment of pregnancies to be continued has been attempted only in the former two, and has succeeded only in the eight-cell embryo. A major problem with polar body biopsy is recombination for loci near the centromere, which may make analysis of the first polar body alone uninformative. DNA amplification of a single cell by polymerase chain reaction also has inherent pitfalls. Fetal cells in maternal circulation have ostensibly been shown to exist: lymphocytes, trophoblasts, and erythroblasts. The basis for this claim is polymerase chain reaction amplification showing fetal DNA sequences in maternal blood. Diagnosis of fetal chromosomal abnormalities requires techniques other than polymerase chain reaction, namely fluorescence in situ hybridization. Fetal trisomy has thus been detected by flow-sorting maternal blood for fetal erythroblasts followed by subjecting sorted cells to fluorescence in situ hybridization for chromosome-specific probes.

The stem cells of a primordial germ cell-derived teratocarcinoma have the ability to form viable mouse chimeras

A euploid testicular teratocarcinoma line, STT-3, has been established from a tumor spontaneously occurring in the testis of a 129/Sv-ter male. Developmental ability of the STT-3 stem cells was tested by injecting these cells into mouse blastocysts. The frequency and the extent of chimerism were examined in mid-gestational fetuses and in live-born mice. STT-3 stem cells form viable chimeras at a high rate and differentiate into normal tissues. This is the first reported testicular teratocarcinoma-derived stem line with a proven capacity to form viable chimeric mice upon injection into the blastocysts.