Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Embryos”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 955 records · Page 53Linked to original sources
PubMed1989

Abnormal development and dye coupling produced by antisense RNA to gap junction protein in mouse preimplantation embryos.

Antisense RNA to the 27/32-kDa rat liver gap junction (GJ) protein was used to explore the role of GJs in preimplantation embryos. When all blastomeres of two- and four-cell embryos were injected with GJ antisense RNA, the percentage of embryos compacted at 60 hr of development was reduced to less than 20%, while 90% of uninjected embryos and 75% of embryos injected with an unrelated RNA were compacted. When most cells of compacted eight-cell embryos were injected with the GJ antisense RNA, 20% of the embryos were decompacted and only 5% had developed to the blastocyst stage at 90 hr, when blastulation had occurred in 90% of the control embryos. When antisense RNA was injected in one blastomere of four-cell embryos, 40% of the embryos presented a large cell that was not included in the compacted embryo at the time of compaction, and an additional 30% of the embryos had two smaller, excluded blastomeres. These excluded cells were identified as the injected cell with a rhodamine-conjugated dextran marker. To assess effects on junctional communication, one blastomere of some embryos was injected with Lucifer yellow, a GJ-penetrating dye, at various times after a blastomere was injected with antisense RNA. The dye was visible in the whole cell mass of control embryos, but it was excluded from a portion of experimental embryos when the delay between the RNA and the Lucifer yellow injections was 1 hr or longer.

Animals↗
PubMed1997

The chromosomal constitution of embryos developing from abnormally fertilized oocytes after intracytoplasmic sperm injection and conventional in-vitro fertilization.

The aim of this study was to analyse the chromosomal constitution of embryos developing from mono- (1PN) and tripronuclear (3PN) oocytes, after in-vitro fertilization (IVF) and after intracytoplasmic sperm injection (ICSI) into oocytes, by means of the fluorescent in-situ hybridization (FISH) technique with specific probes for the chromosomes X, Y and 18. FISH analysis was carried out on embryos from 3PN oocytes: 106 after ICSI and 71 after conventional IVF. In the 3PN embryos after ICSI, equal ratios of XXX and XXY were observed and no XYY embryos were present. This shows the digynic origin of such 3PN embryos. On the other hand, after conventional IVF, the XYY status indicative of dispermic fertilization was observed in some embryos. After IVF, only 12.7% of the 3PN oocytes developed into embryos with uniformly triploid blastomeres, compared with 55.7% after ICSI (P < 0.001). On the other hand, after ICSI only 16.0% of the embryos developing from 3PN oocytes were mosaic, compared with 42.3% after conventional IVF (P < 0.001). FISH was also carried out on embryos from 1PN oocytes: 61 after ICSI and 115 after conventional IVF. In 35.6% of IVF embryos developing from 1PN oocytes Y-specific hybridization signals were observed. This indicates that in 70-75% of such cases a spermatozoon had penetrated the oocyte and that only 25-30% of them were parthenogenetic. A significantly higher proportion (P < 0.001) of embryos developing from 1PN oocytes were diploid after IVF (48.7%) than after ICSI (27.9%); equal ratios of XX and XY embryos were observed in the two groups. Formation of a single pronucleus in an embryo subsequently shown to be diploid indicates that normal fertilization was followed by asynchronous formation of pronuclei. A significantly (P < 0.001) higher proportion of 1PN oocytes developed into haploid embryos after ICSI (31.2%) than after conventional IVF (13.1%). In both groups most of the haploid embryos were X-bearing (IVF, 93.3%; ICSI, 84.2%) and only a few were Y-bearing (IVF, 6.7%; ICSI, 15.8%). A contribution of normal fertilization and androgenetic activation thus led to 1PN oocytes. Gynogenetic and/or parthenogenetic activation, both leading to indistinguishable chromosomal distributions, also contributed to the formation of 1PN oocytes after ICSI and IVF.

Chromosome Aberrations↗
PubMed2004

Changes in water status and proline and abscisic acid concentrations in developing somatic embryos of pedunculate oak (Quercus robur) during maturation and germination.

Somatic embryos of oak (Quercus robur L.) were matured on P24 media differing in gel strength (0.8, 0.9 and 1.0% (w/v) agar). Viscosity and osmotic potential (Psipi,medium) of the media were determined. Developing cotyledonary embryos were analyzed at maturity Stages I-III for water content, osmotic potential (Psipi,embryo) and concentrations of abscisic acid (ABA) and proline. Proliferation of embryogenic tissue, germination rates and the number of embryos formed were also determined in order to relate embryo quality to physiological parameters. Viscosity increased with agar concentration, a phenomenon apparently related to water availability. Many Stage III embryos with high germination potentials were obtained on P24 medium containing 1.0% agar. Embryo water content decreased progressively from 94 to 80% during embryo maturation. Stage I and II embryos that matured on media containing 0.8 or 0.9% agar had similar values of Psipi,embryo, whereas Psipi,embryo of Stage III embryos that matured on medium containing 1.0% agar was significantly lower, although Psipi,medium was unaffected by gel strength. Stage III embryos showed a nearly 16-fold increase in proline concentration and a 50% decrease in ABA concentration compared with Stage I embryos. We conclude that tissue water status and a complex relationship between ABA and proline concentrations, modulated by medium gel strength, are important factors in the maturation process and the quality of oak somatic embryos.

Abscisic Acid↗
PubMed2004

Role of messenger RNA expression of platelet activating factor and its receptor in porcine in vitro-fertilized and cloned embryo development.

Platelet activating factor (PAF) is known as an autocrine growth/survival factor in mammalian preimplantation embryos. This study investigated the expression of porcine PAF receptor (PAFr) mRNA and its role in porcine in vitro fertilized (IVF) or somatic cell nuclear transfer (SCNT) embryo development. The expression of PAFr mRNA in IVF or SCNT blastocysts was shown by reverse transcription-polymerase chain reaction (RT-PCR) and Southern blot analysis. Semiquantitative RT-PCR and Southern blot analysis demonstrated that PAFr mRNA was expressed during preimplantation embryo development, it was highly expressed through the 2-cell to 8-cell embryo stage, and it decreased at the morula stage. PAFr mRNA expression was detected steadily in IVF embryos, whereas it was varied at the 2-cell, 4-cell, and blastocyst stages in SCNT embryos. To determine the role of PAF in IVF and SCNT embryo development, embryos were cultured in North Carolina State University (NCSU)-23 medium supplemented with different concentrations of PAF (0, 0.037, 0.37, 3.72, or 37.2 nM). The PAF supplement significantly increased the rate of blastocyst formation in SCNT embryos, but not in IVF embryos. The PAF supplement for the entire 168 h of culture showed significantly higher blastocyst formation in SCNT embryos. Upregulation of PAFr mRNA by PAF in SCNT embryos indicated that the embryotrophic effect of PAF was mediated through its functional receptors in SCNT embryos. In conclusion, the present study demonstrated that PAFr mRNA was expressed in porcine IVF and SCNT embryos, and that PAF supplement improved the developmental competence of SCNT embryos through its specific receptors.

Animals↗
PubMed2002

In vitro production and nuclear transfer affect dosage compensation of the X-linked gene transcripts G6PD, PGK, and Xist in preimplantation bovine embryos.

Equal expression of X-linked genes such as G6PD and PGK in females and males and the initiation of X-chromosome inactivation are critically dependent on the expression of the X-inactive specific transcript (Xist). The objective of the present study was to determine the effects of in vitro production (IVP) and nuclear transfer (NT) on the relative abundance (RA) of the X-linked transcripts G6PD, PGK, and Xist in preimplantation bovine embryos. In experiment 1, sex-determined IVP or in vivo-produced embryos were analyzed for mRNA expression of the 3 genes. The sex ratio was 36% vs. 64% in IVP blastocysts and thus deviated significantly from the expected ratio of 50% in the vivo control group. The RA of G6PD transcripts was significantly higher in female IVP embryos than in male embryos. In contrast, no significant differences were seen between in vivo-derived female embryos and their male counterparts. At the morula stage, female IVP embryos transcribed significantly more PGK mRNA than did male embryos. However, blastocysts did not exhibit significant differences in PGK transcripts. No differences were observed for in vivo-derived embryos with regard to the RA of PGK transcripts. The RA of Xist mRNA was significantly higher in all female embryos than in their male counterparts. In experiment 2, IVP, in vivo-developed, NT-derived, and parthenogenetic embryos carrying two X chromosomes of either maternal and paternal origin or of maternal origin only (parthenogenotes) were analyzed for the RA of the 3 genes. In NT-derived morulae, the RA of G6PD transcripts was significantly increased compared with their IVP and in vivo-generated counterparts. G6PD transcript levels were significantly increased in IVP blastocysts compared with in vivo-generated and parthenogenetic embryos. At the morula stage, PGK transcripts were similar in all groups, but the RA of PGK transcripts was significantly higher in IVP blastocysts than in their in vivo-generated, parthenogenetic, and NT-derived counterparts. The RA of Xist was significantly elevated in NT-derived morulae compared with IVP, in vivo-generated, and parthenogenetic embryos. NT-derived blastocysts showed an increased Xist expression compared with that of IVP, in vivo-generated, and parthenogenetic embryos. Results of the present study show for the first time that differences in X-chromosome-linked gene transcript levels are related to a perturbed dosage compensation in female and male IVP and female NT-derived embryos. This finding warrants further studies to improve IVP systems and NT protocols to ensure the production of embryos with normal gene expression patterns.

Animals↗
PubMed1999

Cloning of bovine embryos from vitrified donor blastomeres.

The use of cryopreserved in vitro produced bovine embryos as nuclear transfer donors was assessed. Day 4 or 5 morulae were vitrified and warmed using the open pulled straw method and used as donors for nuclear transfer. Although the proportion of morulae and blastocysts that developed from nuclear transfer embryos derived from day 5 vitrified embryos did not differ from that derived from fresh embryos (16.7 and 24.3%, respectively), development to blastocysts was reduced when vitrified donor cells were used (8.3 and 19.1%, respectively). Likewise, development to morulae and blastocysts was not different between nuclear transfer embryos derived from day 4 vitrified embryos allowed to recover for 24 h, and day 5 vitrified embryos allowed to recover for 1-2 h (27.7 and 15.6%, respectively), but the development to blastocysts was reduced when day 5 vitrified donor cells were used (23.2 and 10.0%, respectively). However, in nuclear transfer embryos derived from either day 4 vitrified or day 5 fresh donors, no differences were observed in development rates to morulae and blastocysts (34.3 and 36.3%, respectively) or to blastocysts alone (20.2 and 18.1%, respectively). Nor were there differences in the development rates of fresh or day 4 or day 5 vitrified in vitro produced (non-nuclear transfer) embryos (47.9, 51.0 and 35.5% developing to blastocysts at day 7, respectively). In vitro produced embryos and nuclear transfer embryos derived from day 4 vitrified or day 5 fresh donors were transferred to recipients at morula or blastocyst stage at day 6 or 7. The pregnancy rates were similar in both groups of nuclear transfer embryos, but higher in the control group consisting of in vitro produced embryos (47, 42 and 67%, respectively). In conclusion, if vitrified donor embryos are allowed to recover for 24 h after warming, their use in nuclear transfer results in similar efficiencies to those achieved with fresh embryos.

Animals↗
PubMed2001

Development of porcine embryos in vitro: effects of culture medium and donor age.

We compared development of porcine embryos in three media and evaluated the effect of age of the donor on embryo development in vitro. In Exp. 1, embryos were collected from 35 postpubertal females on d 2 or 3 after onset of estrus. Embryos were cultured 144 h in Whitten's Medium (WM), North Carolina State University Medium-23 (NCSU-23), or Beltsville Embryo Culture Medium-3 (BECM-3) in 95% air: 5% CO2 at 39 degrees C. More (P < 0.01) embryos that were initially one cell or two cells developed to blastocysts when cultured in NCSU-23 (56%) and BECM-3 (43%) rather than in WM (7.5%). More (P < 0.01) embryos that were four cells at recovery developed to blastocysts in NCSU-23 (97%) than in BECM-3 (69%) or WM (69%). Blastocysts that developed from four-cell embryos cultured in BECM-3 had more (P < 0.01) nuclei than blastocysts that developed from four-cell embryos in the other two media. In Exp. 2, ovarian responses, fertilization rates, and in vitro embryo development in NCSU-23 and BECM-3 were compared for postpubertal (approximately 170-d-old) gilts vs gilts given exogenous gonadotropins at 102 d of age. Ovulation rate (P < 0.01), number of eggs recovered, and number of eggs fertilized per gilt (P < 0.001) were greater in the older gilts. The percentage of eggs fertilized, the number of unfertilized eggs, and the number of unclassifiable eggs were similar (P > 0.10) for both age groups. More (P < 0.10) blastocysts developed from embryos recovered from 170-d-old than from 102-d-old gilts, and more (P < 0.05) blastocysts developed in NCSU-23 than in BECM-3. Zona thicknesses and number of nuclei per embryo were similar (P > 0.10) for both ages. We conclude that embryos from prepubertal gilts do not have the same in vitro developmental potential as those from cyclic gilts. However, superior development of embryos in NCSU-23 from both 102-d-old and 170-d-old gilts indicates that media composition did not differentially affect embryos produced by younger vs older gilts.

Age Factors↗
PubMed1990

Culturing two- to eight-cell caprine embryos using domestic chicken eggs.

Early-stage caprine embryos were placed in the chick embryo amnion to determine if this culture method would support the development of embryos from a farm animal species. Following superovulation and natural mating, two- to eight-cell embryos were surgically collected from crossbred donor goats. Embryos were allotted to in vitro culture treatments across two different experiments (EXP). In EXP-I, embryos allotted to Treatment A (control) were cultured in Ham's F-10 with 10% fetal calf serum and 1% antibiotic-antimycotic (HF-10). Embryos in Treatment B were placed on a bovine fetal uterine fibroblast monolayer in HF-10, embryos allotted to Treatment C were agarose embedded and injected into the amniotic cavity of a day-4 chick embryo and those placed in Treatment D were co-cultured in HF-10 with day-15 caprine trophoblastic vesicles. In EXP II Treatments A, B, and C were the same; however Treatment D was omitted. EXP-I and EXP-II also differed in that chick embryo co-culture was for 72 hr in EXP-I but was extended to 96 hours in EXP-II. Additionally, the monolayer co-culture was limited to 96 hr in EXP-II; whereas, embryos in EXP-I remained on monolayer culture for 96 hr plus an additional 72 hr for subsequent embryo evaluation. Results indicate that the amniotic cavity of the developing chick embryo enhanced the development of two- to eight-cell caprine embryos through to hatching blastocysts when compared with that of the control medium alone.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2005

Differences in gene expression patterns between somatic cell nuclear transfer embryos constructed with either rabbit granulosa cells or their derivatives.

Successful production of offspring by somatic cell nuclear transfer (SCNT) is affected by the nature of the donor cells used. The purpose of this study was to determine whether characteristic changes induced in donor cells by culture conditions influenced gene expression patterns in the resultant SCNT embryos. Rabbit granulosa cells (rGC) were cultured under different conditions, either with or without hCG, and the two derivative cell types obtained (named respectively cGC+ and cGC-) were used as donor cells for SCNT. There were characteristic differences between fresh rGC and the two derivative cell types: p450scc expression and progesterone secretion were both higher in cGC+ than in cGC-; expression of bmp4 and fgfr2 was decreased in cGC+ and cGC- compared with rGC; and cGC+ and cGC- cell types gained collagenIV expression. Use of fresh rGC, or cGC+ and cGC- derivative cells, did not alter either the developmental potencies of SCNT oocytes or cell numbers at the blastocyst stage. The expression patterns of four genes (bmp4, fgfr2, gata4, oct3/4) in SCNT embryos and in fertilized embryos were analyzed by quantitative RT-PCR. We found that oct3/4 was expressed in all embryos. The expression patterns of the other three genes showed considerable variation between the different types of embryo: bmp4 was found in most fertilized embryos but only some of rGC and none of cGC+ and cGC- derived SCNT embryos; fgfr2 was present in fertilized embryos but was present in some rGC and cGC- NT embryos and in all cGC+ NT embryos; gata4 was not expressed in fertilized embryos but was present in a few rGC and cGC+ NT embryos and in most cGC- NT embryos. Our results suggest that the gene expression patterns in SCNT embryos derived from granulosa donor cells are affected by characteristic changes to the cells during in vitro culture.

Animals↗
PubMed2005

Comparison of embryo quality in high-yielding dairy cows, in dairy heifers and in beef cows.

The purpose of this study was to compare embryo quality of lactating Holstein Friesian cows (LHFC), non-lactating Holstein Friesian heifers (NLHFH) and Belgian Blue beef cows (BB) and to identify factors that are associated with embryo quality in LHFC and NLHFH. After superovulation and embryo recovery at Day 7, embryos (n=727 from 47 LHFC, 27 NLHFH and 50 BB) were scored morphologically for quality, colour and developmental stage. Blood samples and data concerning parity, age, milk production and management were collected. Data were compared univariably between the three groups. A multivariable regression model was built with quality and colour of the LHFC and NLHFH embryos as dependent variables. Only 13.1% of LHFC embryos were categorized as excellent compared to 62.5% and 55.0% of the embryos in NLHFH and BB, respectively. Almost none of the NLHFH or BB embryos displayed a dark appearance of the cytoplasm compared to 24.1% of the LHFC embryos. Only 4% of all LHFC embryos reached blastocyst stage compared to 23.2% and 17.3% in NLHFH and BB. Based on the multivariable regression analysis, "physiological status" (lactating or not) together with the serum total protein concentration of LHFC and NLHFH, was significantly associated with embryo quality and colour. Thus, LHFC display an inferior embryo quality compared to NLHFH and BB. Producing milk or not seems to be significantly associated with embryo quality. Therefore, reduced embryo quality on Day 7 following AI, could be an important factor in the subfertility problem in modern high-yielding dairy cows.

Animals↗
PubMed1999

Initial experience with extended culture and blastocyst transfer of cryopreserved embryos.

OBJECTIVE: Our purpose was to evaluate the viability and transfer efficiency of cryopreserved embryos allowed to develop into blastocysts in extended culture for in vitro fertilization. STUDY DESIGN: The embryos for in vitro fertilization that had been cryopreserved at either 2 PN (pronuclear) or cleaving stage (day 1-3) were thawed and cultured for uterine transfer on day 5. Outcome for day 5 embryo transfer was prospectively compared with previous outcomes from embryos transferred on day 2 or 3. RESULTS: For embryos thawed and transferred on day 2 or 3 (n = 99), the pregnancy rate was 33%, the implantation rate per embryo transferred was 15.2%, and the rate of multiple gestations was 42.4% (14/33) with 35.7% of pregnancies having >/=3 gestational sacs. For extended culture embryos transferred on day 5 (n = 25), the pregnancy rate was 36%, the implantation rate per embryo transferred was 16.7%, and the rate of multiple gestations was 33.3% (3/9) with all of these being twins. For embryo transfers performed on day 5 in which only blastocysts were transferred (n = 9), the pregnancy rate was 66.7%, the implantation rate per blastocyst was 44.4% (greater than the rate for the day 2 or 3 embryos, P =.0043), and the rate of multiple gestations was 33.3% (2/6) with all of these being twins. In extended culture 29.8% of cryopreserved embryos progressed to the blastocyst stage. In this series 4 subjects (15.4%) did not have blastocysts by day 5. CONCLUSION: Acceptable pregnancy rates can be obtained from cryopreserved embryos cultured to the blastocyst stage with a significantly higher implantation rate. Transfer of embryos that have "self-selected" to blastocysts results in reduced risk of higher-order (>2) multiple gestations, because only 1 or 2 embryos are transferred.

Blastocyst↗
PubMed2004

Exposure of preimplantation embryos to platelet-activating factor increases birth rate.

PROBLEM: Platelet-activating factor (PAF) plays a significant role in fertility. Preimplantation stage embryos produce PAF (ePAF) which is required for development. PAF's mechanism of action is receptor-mediated and its presence has been reported in the developing mouse and human embryo. Exposure of preimplantation stage mouse embryos results in higher implantation rates. However, the effect of such treatment on live-birth rates and birth weights has not been reported. Therefore, the objective the study was to determine the effect of exposing preimplantation mouse embryos to PAF on subsequent birth rate and weight. DESIGN: Two-cell stage preimplantation stage mouse embryos exposed to PAF (10(-7) M) for 15 min prior to intraoviductal transfer. METHODS: Preimplantation stage embryos were recovered from eCG/hCG primed BDF1 female mice. Embryos were exposed to synthetic PAF (10(-7) M) for 15 min. PAF-treated embryos were transferred to the oviducts of pseudopregnant female CD-1 female mice. Superovulated and cultured BDF1 embryos not treated with PAF served as in vitro controls and naturally ovulated embryos with no collection/culture served as in vivo controls. Embryos were permitted to develop to term (18-21 days). The number of pups born per litter and litter weights subsequently were recorded. RESULTS: A total of 160 BDF1 mouse embryos were collected, treated, and transferred (20 per CD-1 recipient) as described. There was a significant (P < 0.05) increase in the number of pups born to the PAF treatment group (56/80; 70%) as compared to the control group (44/80; 55%). There was also a significant difference (P < 0.05) in litter birth weights between the PAF (1.31 g/litter) and controls groups (1.25 g/litter). There was a significant difference (P < 0.05) in birth weights between the PAF treatment group and the in vivo group (1.51 g/litter). There was a significant difference in birth weights between the in vitro-control and in vivo groups (1.51 g/litter). There were no observational malformaties to pups born in any group. CONCLUSIONS: Brief exposure of preimplantation stage embryos to PAF will result in a significant increase of delivery rates (pups/litter) as well as birth weights. However, the increase of birth weight was significantly below that found naturally. Additional studies are warranted to elucidate the mechanism of PAF's action in the preimplantation stage embryo and subsequent uterine development.

Animals↗
PubMed1995

Delaying transfer to the third day post-insemination, to select non-arrested embryos, increases development to the fetal heart stage.

The purpose of this study was to determine whether delaying embryo transfer by 24 h, until day 3 post-insemination, allowed improved selection of non-arrested embryos for transfer. We have retrospectively analysed pregnancy rates in a large series of patients who had embryo transfer either on day 2 or on day 3 post-insemination over a 27 month period. From January 1990 to March 1992, 567 patients received embryo transfer on day 2, and 661 patients had transfer on day 3 post-insemination, but these transfers were not contemporary. Pregnancy rates were slightly higher in patients who had embryo transfer on day 3 (37%) than in those patients who had their embryos transferred on day 2 (35%), but this difference was not significant. The implantation rate, as measured by the proportion of embryos developing to the fetal heart stage, was significantly higher following transfer on day 3 (23%) than after transfer on day 2 (19%) (P < 0.05), suggesting that selection of viable embryos is improved on day 3. Furthermore, of the embryos which gave rise to a fetal sac, significantly fewer miscarried before the fetal heart stage (P < 0.05) following transfer on day 3 (6%) than after transfer on day 2 (12%). Delaying transfer until day 3 provides a further 24 h to observe embryo development. During this period 16% of embryos arrested or became developmentally retarded; thus waiting until day 3 allowed these embryos to be identified and avoided for consideration for transfer. Embryo transfer may be safely delayed until day 3, and this may help in selecting embryos most likely to implant and develop after transfer.

Adult↗
PubMed1998

Cryopreservation in human assisted reproduction is now routine for embryos but remains a research procedure for oocytes.

Human embryo cryopreservation represents an indispensable extension of in-vitro fertilization (IVF) programmes as long as they are based upon the recovery of a large number of oocytes. The most widely used procedures include the cryopreservation of human zygotes or embryos in early cleavage, using 1,2-propanediol and sucrose as cryoprotectants. Our results over a 10 year period (1986-1995) on 5032 thawed cycles involving 14 222 stored embryos make it possible to appraise the results and the contribution of embryo freezing to assisted reproduction. Embryos survived the freeze-thaw process in 73% of cases leading to 4590 transfers of 2.2 embryos (91% of thawed cycles). The clinical pregnancy rate per transfer was 16%, the live birth rate 12%, and the rate of babies born alive per transferred embryo was 6%. Embryo freezing monitored 10 years later produced an average of 8% of additional births. By then, 86% of stored embryos had been thawed for transfer to patients. Destruction or donation were required for only 8% of all frozen embryos and there was no news from the parental couple in relation to almost 6% of embryos. The fate of the vast majority of embryos was decided during the first 5 years of storage. Blastocyst cryopreservation is making new strides, thanks to co-culture systems and embryo selection. Micromanipulation procedures seem to have little impact on the outcome of embryo freezing. Human oocyte freezing is again clinically applied. Indeed, much of the concern about injuries to the oocyte structures through the freeze-thaw process do not seem to be justified, and the problems with frozen-thawed oocyte fertilization has been overcome using intracytoplasmic sperm injection (ICSI). As long as oocyte in-vitro maturation is not well controlled, better results will probably be obtained with mature oocyte cryopreservation. Emerging methods include the freezing of immature oocytes, follicles and ovarian tissue.

Cryopreservation↗
PubMed2003

[Co-culture of embryos: influencing factors and mechanisms of action].

In comparison with their in vivo counterparts, the in vitro produced mammalian embryos had markedly lower rates of morula/blastocyst development and pregnancy after transfer to the recipients. Things became even worse in the cloned embryos. This necessitates improvement of the embryo culture system. Co-culture of embryos with different types of somatic cells was found beneficial for embryo development in vitro and many studies have been conducted in this area in recent years. In this paper, recent developments and the authors' own work in studies of co-culture of early mammalian embryos with somatic cells were reviewed, with emphasis on the effects of cell type, stage of estrous cycle and number of passages of somatic cells and supplement of serum on embryo development, and the mechanisms by which co-culture promote embryo development. The recent developments are summarized as follows: 1. Somatic cells of both homogeneous and heterogeneous origins can be used for co-culture of mammalian embryos, with similar developmental rates. 2. Supplementation of animal serum at appropriate concentrations improved the somatic cell growth and consequently the development of embryos in co-culture. 3. The estrous cycle stages of oviduct epithelial cells used for co-culture had no effect on the development of embryos. 4. Over-passaging of somatic cells reduced their efficiency in promoting development of the co-cultured embryos. In conclusion, studies have shown that co-culture overcame the block of embryo development in vitro and improved embryo quality with increased rates of implantation and pregnancy, but many problems remain to be solved on its influencing factors and mechanisms of action.

Animals↗
PubMed1985

Cytoplasmic localization and chordamesoderm induction in the frog embryo.

The experiments described here were designed to reveal the distribution in the frog early embryo of components which are sufficient for specification of the dorsal structures of the embryonic body axis. The approach was to allow cleavage planes to divide the embryo into various well-defined regions and to transplant cells from each region into recipient embryos which would otherwise fail to form axial structures. Partial or complete body axis development could then be scored by the use of external criteria or histological methods. Recipients were embryos which had been irradiated before first cleavage with ultraviolet light on the vegetal surface. Irradiated embryos display a well-characterized set of deficiencies in the dorsal structures of the body axis, but their development can be 'rescued' toward normalcy in several ways. In particular, transplantation of certain small groups of blastomeres from the normal 32- to 64-cell embryo into irradiated recipients was sufficient to cause partial or complete axis development. Cell groups which could cause rescue were located in the vegetal and equatorial levels of one quadrant of the normal embryo--the quadrant centered on the future dorsal midline. Clonal marking analysis showed that the vegetal-most cells of this quadrant contribute primarily to endodermal structures in normal development. In rescued recipient embryos, these cells also contributed only to the endoderm; the dorsal mesoderm and central nervous system were formed exclusively by host cells which originated near the transplant. Rescue could also result from transplantation of equatorial cells from the dorsal quadrant of the normal embryo. As in normal development, these cells formed primarily the chordamesoderm of the rescued embryo. Host cells were induced to contribute the somitic mesoderm, central nervous system, and other structures which would have been missing but for the presence of the transplanted cells. The frequency and degree of rescue caused by equatorial and vegetal transplants is variable. This was explained by the discovery that the location of components needed for rescue varies among individual embryos without regard to the positions of cleavage planes. This was true even when donor embryos were selected on the basis of a precisely regular pattern of cleavage. In such selected embryos, particular blastomeres make a predictable contribution of progeny to the body axis. Thus it may be that the positions of components which can cause axis formation vary without exact regard to the fate map of prospective areas. The implications of this for the study of cytoplasmic localization in the early embryo are discussed.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed2002

Cleavage stage versus blastocyst stage embryo transfer in assisted conception.

BACKGROUND: Despite numerous advances in the field of in vitro fertilisation (IVF), many of the widely applied embryo culture techniques and resulting implantation rates have remained relatively unchanged since the first treatment was performed in the mid 1970's. Recent advances in the understanding of nutrient requirements of embryos, have led to a renaissance of extending their culture from the standard procedure of 2-3 days (early cleavage embryo transfer) to 5-6 days (blastocyst culture). The rationale for blastocyst culture is to improve the synchronicity of uterine and embryonic development and provide a mechanism for self-selection of viable embryos. Numerous reports on the clinical benefits of blastocyst culture have led to the worldwide introduction of this technique, despite a deficiency of conclusive evidence to do so. OBJECTIVES: Primary: To determine if blastocyst stage embryo transfers (ET's) result in higher success rates, than cleavage stage embryo transfers. Secondary: To assess the overall embryo utilisation rate of both techniques. SEARCH STRATEGY: Electronic searches of the Cochrane Menstrual Disorders and Subfertility Group specialised register of controlled trials, CCTR, MEDLINE, EMBASE, and Bio extracts were performed to identify relevant randomised controlled trials (RCTs). Attempts were also made to identify trials from the National Research Register, the Clinical Trial Register and the citation lists of review articles and included trials. The first or corresponding author of each included trial was also contacted for additional information. SELECTION CRITERIA: Trials were included if they were randomised and compared the effectiveness of early cleavage versus blastocyst stage transfers. DATA COLLECTION AND ANALYSIS: Of the 29 trials that were identified, ten trials met the inclusion criteria and were reviewed. Primary outcomes were rates of; live birth, clinical pregnancy and implantation per woman. Secondary outcomes were rates of; miscarriage, monozygotic twinning, embryo freezing, embryo utilisation, cancellation, multiple pregnancy and high order pregnancy and per cycle data. Quality assessment and data extraction were performed independently by two reviewers. Meta analysis was performed using odds ratios for dichotomous outcomes and weighted mean differences for continuous outcomes. MAIN RESULTS: There was no significant difference between the two treatment groups in live birth rate, although this was reported by only one quasi-random trial (Peto OR 1.59, 95% CI 0.80, 3.15). There was also no evidence of a difference in pregnancy rate (both overall and subgroups) between the two groups for pregnancy rate per couple randomised (4 RCTs: Peto OR 0.86, 95% CI 0.57, 1.29). There was also no suggestion of an overall difference in implantation rates per embryo's transferred although it was impossible to calculate valid confidence intervals from published data (Day 2/3 17.1% vs Day 5/6 18.9%). The subgroup of sequential media trials suggested higher implantation rate for blastocyst transfer (Day 2/3 22.6% vs Day 5/6 32%). The miscarriage rate was no different between the two groups (1 RCT, Peto OR 1.66, 95% CI 0.41, 6.81). The RCTs reporting embryo freezing showed no difference (Peto OR 1.71, 95% CI 1.00, 2.94), however the two quasi-random trials showed a significant difference in favour of the Day 2/3 group (Peto OR 2.99, 95% CI 1.88, 4.75). Embryo transfer cancellation rates were significantly higher in the Day 5/6 group (5 RCTs: Peto OR 0.57, 95% CI 0.40, 0.83). There was no significant difference in the rate of multiple pregnancies or the rate of high order pregnancies (3 RCTs, Peto OR 0.58, 95% CI 0.30, 1.12)(2 RCTs, Peto OR 7.88, 95% CI 0.49, 126.30 respectively). REVIEWER'S CONCLUSIONS: Overall this review of the best available evidence based on data from randomised controlled trials, suggests that to date little difference in the major outcome parameters has been demonstrated between early embryo transfer and blastocyst culture. Collectively, the increase in cancellation and the possible decrease in cryopreservation rates suggest that the routine practice of blastocyst culture should be offered to patients with caution. The subgroup of trials employing sequential media, did however demonstrate a substantial improvement in implantation rates and similar pregnancy rates, despite the transfer of less embryos. Whether this trend will culminate in convincing higher live birth rates per woman, has yet to be validated.

Blastocyst↗
PubMed1989

Platelet activating factor (PAF) production by mouse embryos in vitro and its effect on embryonic metabolism.

Factors affecting the production of platelet activating factor (PAF) by mouse embryos during culture in vitro were investigated. Detectable levels of embryo-derived PAF were produced within 1-4 hr with maximum PAF activity being observed after 6 hr of culture in vitro. The amount of PAF detected in media after 24 hr of culture of two-cell embryos was equivalent to 12.8 ng PAF/embryo. However, differences in activity were apparent with increased time in culture. Reduced synthesis of PAF during culture in vitro was supported by the observation that morulae stage embryos collected fresh from the reproductive tract displayed more PAF activity than morulae resulting from the 48 hr culture of two-cell embryos. In addition to determining production characteristics of PAF by embryos, we also show that the production of CO2 from carbon-1 position of lactate is positively correlated with the ability of embryos to develop during subsequent culture in vitro and therefore could be used as a measure of embryo viability. Furthermore, culture of embryos in media supplemented with PAF resulted in an increase in lactate utilization demonstrating a direct effect of PAF on the embryo. As PAF is produced by preimplantation embryos, an autocoid role of PAF in regulating embryo development is implicated. Therefore, the reduced production of PAF by embryos in vitro may explain the decreased viability of embryos commonly observed following their culture in vitro.

Animals↗