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 217 records · Page 12Linked to original sources
PubMed1998

Reducing multiple pregnancies by restricting the number of embryos transferred to two at the first embryo transfer attempt.

Though the multiple pregnancy rate in in-vitro fertilization-embryo transfer must be reduced, strict and uniform regulation of the number of embryos transferred may make it impossible for women with little natural fecundity to carry children. We therefore restricted the number of embryos per transfer. In the first half of the observation period (n = 100), we limited the number of embryos transferred to three regardless of the number of previous transfers. In the second half (n = 137), we strictly regulated the number of embryos transferred to two at the first attempt and three in the second and later attempts. The multiple pregnancy rate per pregnancy was significantly lower (P < 0.005) in the second period (20.4%) than in the first period (52.9%), while the clinical pregnancy rate and the implantation rate per transfer were similar in both observation periods. 60.7% (17/28) of the multiple pregnancies arose from the first embryo transfer attempt, and 17.9% (5/28) of them arose from a second attempt. The 18 multiple pregnancies in the first period involved six sets of triplets, while the 10 multiple pregnancies that arose in the second period all involved twins. The implantation rate per transfer at the first attempt was significantly higher than that at the second or later attempts. The criterion for determining the number of embryos transferred should be simple to minimize errors of judgement. We believe that our method of restricting the numbers of embryos transferred may be one method of reducing multiple pregnancies without eliminating the possibility of having children for women with low fecundity.

Adult↗
PubMed2006

Construction of an evidence-based integrated morphology cleavage embryo score for implantation potential of embryos scored and transferred on day 2 after oocyte retrieval.

BACKGROUND: Evidence-based morphological embryo scoring models for ranking of implantation potential are still scarce, and the need for a precise model increases when aiming for singleton pregnancies. METHODS: Prospectively, 2266 IVF/ICSI double-embryo, day 2 transfers were studied. The five variables scored in 3- to 5-step scales for the embryos transferred are blastomere number (BL), fragmentation, blastomere size variation ('equality', EQ), symmetry of the cleavage and mononuclearity in the blastomeres (NU). The scoring results of embryos with an individual traceability from scoring to implantation, i.e. treatments resulting in either no implantation (n=1385) or twin implantation (n=228), were studied for prognostic potential. RESULTS: Although all five variables correlated highly with implantation potential, only BL, NU and EQ remained independently significant after regression analysis. The equation thus derived formed the basis for a 10-point integrated morphology cleavage (IMC) embryo score. A table with the scoring point for each possible combination of the embryo variables is presented. The scoring model was statistically validated on the singleton pregnancy group (n=653). CONCLUSIONS: We suggest that this IMC embryo scoring, incorporating cleavage stage and information on the variation in blastomere size and the number of mononucleated blastomeres, may optimize embryo ranking and selection for day 2 transfers.

Adult↗
PubMed1985

Matching of embryo stages and grades with recipient oestrous synchrony in bovine embryo transfer.

The efficacy of matching embryos with recipients on the basis of embryo stage and grade and donor-recipient oestrous synchrony was investigated using the records of 13,663 embryos that were collected and transferred at a commercial embryo transfer centre. The selection of early blastocysts for exact oestrous synchrony cows was effective and resulted in the highest pregnancy rates. Selection of early morulae was effective for recipients in oestrus after the donor but not when transferred into exact and negative recipients. The matching of late morulae with recipients in oestrus after the donor was not effective and had no influence on pregnancy rates. The selection of late, hatched and collapsed blastocysts for transfer into recipients in oestrus before the donor was ineffective and pregnancy rates were higher in exact and +12 hour recipients. Pregnancy rates declined 23.6 per cent in quality grades 1 to 4 whereas the range between stages was 13.3 per cent. Higher quality embryos of all stages gave the highest pregnancy rates. Examination of pregnancy rates of grades within stages suggested that the more developed the embryo the more difficult it is to grade. The difference in pregnancy rates between exact and -24 (6.9 per cent) and +24 (4.8 per cent) hour recipients was small and declined a further 4.7 per cent and 9.8 per cent in -36 and +36 hour recipients. Grade 3 and 4 embryos tolerated asynchrony better than grade 1 and 2, and early morulae tolerated asynchrony better than the other stages. It was concluded that the matching of certain embryo stages with the donor-recipient oestrous synchrony is advantageous but not always possible.

Animals↗
PubMed1999

A fiber-optic measurement system of light scattering to evaluate embryo viability: model experiment using a latex sphere suspension and mouse embryos.

In this study, we tested the efficacy of a fiber-optic light scattering system developed by us to measure mitochondrial size and particle density in embryos in order to establish a non-invasive method of evaluating human embryo viability for in vitro fertilization and embryo transfer. Particle size was determined by comparing the measured angular distribution of the light scattering intensity with that of the theoretical distribution using a 1.0 micron latex sphere suspension and mouse embryos. The measured light scattering pattern of the latex suspension was found to agree closely with the theoretically derived pattern. The measured light scattering pattern of the mouse embryo was similar to the calculated pattern of spheres, the diameter of which was equivalent to that of the mitochondria. Therefore, the measured light scattering is thought to be derived mainly from the mitochondria in the embryo. The relationship between light scattering intensity and latex particle density was also examined in order to estimate the detectable range of mitochondrial particle density. Since the detectable range of the particle density obtained in our study (1.4 x 10(6) - 1.4 x 10(11) particles/ml) was greater than the known mitochondrial particle density in human embryos (1.0 x 10(9) - 1.0 x 10(11) particles/ml), we believe that this mitochondrial particle density can be measured using our system. We concluded that it is possible to use our simple system as a non-invasive method for evaluating human embryo viability.

Animals↗
PubMed2005

Can artificial techniques supply morally neutral human embryos for research? Part I. Creating novel categories of human embryos.

Manipulations of the molecular composition and formation of human embryos are posing vital new challenges to traditional concepts of human identity and procreation. Current trends in embryology in particular are reshaping the ethical question of how scientific research should treat experimentally derived embryos. Some investigators have argued that embryos created through artificial means are technologically novel entities that should be exempt from ethical restraints placed on research involving human embryos that come into being through natural processes. These include uniparental embryos derived through cloning or parthenogenesis, as well as multiparental, hybrid-parental, and xenohybrid-parental embryos. If confined to natural means many of these genetic unions could not occur, but through the intervention of technology, it is becoming possible to design and grow strange and unusual forms of embryos, in some cases using human gametes. Regardless of the genetic contributors or the processes used to fertilize and stimulate egg activation, in each case the new embryo represents an individual organism that begins a process of development. We conclude that the prospect of creating or redesigning new human life should be held to a stringent ethical standard of precaution, even higher than that of deciding to destroy existing embryonic life. Accordingly, we urge cautious ethical reflection and broad public discussion prior to deciding whether to permit embryologic research into novel forms of procreative means in nonhuman animals, to be further extended to humans.

Animals↗
PubMed1986

Residual embryos in failed embryo transfer.

One hundred thirteen embryo transfers (ETs) were performed in an in vitro fertilization and ET program of which residual or extruded embryos were found in 17 transfers (15%). Residual or extruded embryos are those embryos found outside the uterine cavity, either at the cervical os, on the vaginal speculum, or remaining in the catheter after an ET. Patients were divided into two groups according to the method of inspection for residual embryos. In group I, microscopic visualization of the transfer catheter alone revealed that 9 of the 67 transfers (13.4%) had 17 residual embryos either at the catheter tip or adherent to mucus on the side of the catheter. In group II inspection of the catheter and cervical wash revealed that 8 of 46 ETs (17.4%) had 15 residual embryos that failed to be transferred during the initial attempt. Six of these 15 (40%) were found in the cervical wash medium. Thus, failure of the proper placement of embryos at the time of transfer may occur frequently. Evaluation of only the transfer catheter may result in a significant underestimation of the problem.

Animals↗
PubMed1985

The effect on cleavage of two-cell mouse embryos after a delay in embryo retrieval in a human in vitro fertilization programme.

Two-cell mouse embryos are used for quality control in a human in vitro fertilization programme. A controlled experiment was designed to evaluate the effect on cleavage of two-cell mouse embryos after a delay in embryo retrieval. In the test group, two fallopian tubes were incubated in Whittingham's T6 medium for 2 1/2 hours per experiment before the embryos were removed for culture. In the control group embryos were removed from the fallopian tubes immediately after the mice were sacrificed. Five experiments were performed. Eight of 141 two-cell embryos (5,7%) reached the blastocyst stage in the test group, and in the control group 143 of 151 two-cell embryos (94,7%) reached the blastocyst stage after 72 hours. Embryos must be removed immediately after the mice are sacrificed to obtain constant results. If not, poor cleavage can lead to unnecessary confusion in the laboratory.

Animals↗
PubMed2006

Culture of zygotes increases TRP53 [corrected] expression in B6 mouse embryos, which reduces embryo viability.

The expression of TRP53 in blastocysts that had been cultured from the zygote stage in vitro for 90 h was compared with that in blastocysts collected from the uterus in C57BL6 (B6) and in F1 hybrid (B6CBF1) strain mice. In both strains, there was little TRP53 detected in blastocysts collected from the uterus. There was some increased expression in cultured embryos from B6CBF1 mice and marked increased expression in cultured B6 blastocysts. In cultured B6 embryos, there was obvious accumulation of TRP53 within the nuclear region of embryonic cells. Cultured B6 zygotes had significantly poorer rates of blastocyst formation and of capacity to undergo implantation or form viable fetuses than cultured zygotes from B6CBF1 mice or B6 blastocysts collected from the uterus. Trp53-/- zygotes (B6 background) were significantly more likely to form blastocysts than sibling wild-type embryos, with Trp53+/- embryos having an intermediate level of viability (P<0.01). On transfer of blastocysts to recipient females, Trp53-/- blastocysts were more likely to form viable fetuses than wild-type or heterozygous sibling blastocysts when the embryos resulted from culture of zygotes (P<0.001). This shift in viability did not occur when embryos were only subjected to 24 h of culture from the compacted embryo stage. Culture in vitro in the B6 strain caused a marked increase in the expression and nuclear accumulation of TRP53. This expression was a significant cause of the loss of viability that occurs on culture of zygotes from this strain in vitro.

Animals↗
PubMed1998

Developmental changes in RNA polymerase II in bovine oocytes, early embryos, and effect of alpha-amanitin on embryo development.

Development of mammalian early embryos relies on stored maternal messenger RNAs (mRNAs) that have been synthesized during oogenesis until embryonic genome activation. Although embryonic genome acti vation in bovine embryos has been proposed to start at the late 4-cell stage, recent evidences suggest that embryonic genome activation starts earlier than the 4-cell stage, and molecular details of this event are not known. RNA polymerase II in eukaryotes is responsible for transcription of mRNA and most of the small nuclear RNAs. The unphosphorylated form of RNA polymerase II (IIA) has been shown to function in transcriptional initiation, and the hyperphosphorylated form (IIO) functions in translational elongation and mRNA splicing. In this study, we examined the changes in the amount of RNA polymerase IIA by immunoblotting in immature oocytes; mature oocytes; and 2-, 4- and 8-cell bovine embryos. We also examined the levels of IIO and the multiple intermediately phosphorylated form in the same oocytes and embryos. The IIA reached the highest level at the 2-cell stage and decreased gradually at the 4- and 8-cell stages, and IIO was at very low levels in mature oocytes and 2-cell stage embryos and was not detectable at later stages. The multiple intermediately phosphorylated form was present at the highest level in mature oocytes and was detectable at the other stages. We demonstrate that RNA polymerase IIA, which is responsible for initiation of transcription, is present in oocytes and preimplantation embryos and reaches the highest levels in the 2-cell stage embryos. Inhibition of RNA polymerase II-dependent transcription during any of the first four embryonic cell cycles has detrimental effects on progression of embryonic development beyond the 16-cell stage, indicating the importance of early transcripts for continuation of development. The results indicate that expression of all the genes whose transcription is inhibited by alpha-amanitin is essential for embryo development.

Amanitins↗
PubMed1994

Covering embryo cultures with mineral oil alters embryo growth by acting as a sink for an embryotoxic substance.

PURPOSE: Assisted reproductive technologies require the use of culture media for gametes and embryos. Culture media and conditions intended for use in human in vitro fertilization are tested prior to use by evaluating their ability to support normal development of mouse embryos. RESULTS: Development to blastocysts of two-cell mouse embryos was equivalent for embryos cultured in center well dishes alone (93 +/- 10%, mean +/- SD) and embryos cultured in center well dishes with an overlay of 1 ml of mineral oil (94 +/- 5%). In contrast, no development of two-cell-stage mouse embryos occurred in an embryotoxic medium when cultured in center well dishes. However, when this medium was covered with an overlay of mineral oil, development to blastocyst was no different than that of controls (96 +/- 5%). Similar results were found with cultures of one-cell-stage mouse embryos. CONCLUSION: These results indicate that in some circumstances the presence of mineral oil can significantly alter the outcome of embryo culture. Further, these results reinforce the necessity of directly testing the exact culture conditions to be used for assisted reproductive technologies.

Analysis of Variance↗
PubMed1994

Embryo growth rate in vitro as an indicator of embryo quality in IVF cycles.

PURPOSE: The role of embryo growth rate in vitro as an isolated indicator of embryo quality in IVF was evaluated retrospectively. METHODS: Comparison was made between 98 cycles (group 1), in which only embryos at a cleavage stage of two to three blastomers were transferred, and 99 cycles (group 2), in which all embryos were transferred at a cleavage stage of four or more blastomers. Embryos were transferred at a fixed interval of 42 to 44 h following oocyte insemination. The mean patients' age, number of oocytes recovered and number of embryos transferred per cycle were similar in both groups. RESULTS: The pregnancy rate and the take-home-baby rate were significantly higher in group 2 as compared to group 1 (22.2% vs 7.1% and 16.2% vs 4.1%; P < 0.05 and P < 0.001, respectively). CONCLUSIONS: These results demonstrate that embryos with a slow cleavage rate in vitro are less likely to produce pregnancy following IVF-ET and that the cleavage stage is a valuable criteria in the selection of the best embryo for transfer.

Adult↗
PubMed2005

Transplantation of a polyembryonic wasp embryo: a technique for transferring endoparasitic embryo into the host egg.

Concealed development of many animal embryos prevents examination of development and limits the application of embryo manipulation techniques aimed at understanding developmental processes. In embryos developing in utero, such as in mammals, it is necessary to dissect embryos from the mother and, upon manipulative intervention, to implant them back into the recipient. Parasitic wasps present a promising system for understanding the evolution of early developmental processes. In basal ectoparasitic species that lay eggs on the surface of the host, it is possible to adapt embryo manipulation techniques developed in Drosophila. However, their derived endoparasitic relatives, which exhibit various modifications of developmental programs, undergo concealed development within the host body. For example, the parasitic polyembryonic wasp Copidosoma floridanum oviposits an egg into the egg of the host moth Trichoplusia ni. The host larva emerges and the parasite undergoes development within the host body, preventing embryo manipulation as a means of examining developmental regulation. Here we present a protocol for embryo transfer that allows the transplantation of C. floridanum egg into the host egg. This approach opens a new avenue in the application of various embryo manipulation techniques aimed at understanding the evolution of embryogenesis in endoparasitic Hymenoptera. In addition, this approach has potential for the development of other tools in C. floridanum, such as transgenesis and reverse genetics, which can also be extended to other endoparasitic species.

Animals↗
PubMed1995

Cell death in rat and mouse embryos exposed to methanol in whole embryo culture.

Methanol induces developmental toxicity in rats and mice producing exencephaly, cleft palate, cervical skeletal defects, reduced body weight, and increased embryo/fetal death. Exposure to methanol in whole embryo culture also induces developmental retardation, dysmorphogenesis, and embryo lethality. In the present study, cultured rat and mouse embryos were exposed to methanol and subsequently observed for morphological effects and increased cell death using modified Feulgen staining which allowed nuclei throughout the embryo to be examined in situ. Growth and developmental scores were reduced by methanol in both rat and mouse embryos and the mouse embryos were affected at lower concentrations when compared to the rat. Methanol increased cell death in specific regions of both rat and mouse embryos, including the forebrain, the visceral arches, otic and optic placodes. These regions form derivatives which manifest morphological abnormalities following exposure in vivo. Methanol did not increase cell death in the neuroepithelium or neural folds and neural tube defects cannot be explained by excess cell death. The results of this study suggest that increased cell death in specific regions of the exposed embryos has a role in producing cranial malformations, abnormalities of the eye and ear, and cleft palate.

Animals↗
PubMed1988

An assessment of alternative policies for embryo transfer in an in vitro fertilization-embryo transfer program.

Conventionally, in in vitro fertilization (IVF) programs, all embryos obtained up to three are freshly transferred in the IVF cycle and supernumerary embryos frozen if cryopreservation facilities exist. This study was concerned with assessing alternative policies for embryo transfer (ET). When three or fewer embryos were obtained in the IVF cycle, fresh embryo transfer was either excluded (group I, n = 69) or only one embryo was immediately transferred (group II, n = 46), the remainder being transferred after freezing and thawing. The pregnancy rate in these two policies was compared to that in a control group of patients (group III, n = 115) in whom all the embryos were transferred in the IVF cycle. The ongoing pregnancy rate was similar in all three groups. No multiple pregnancies occurred in groups I and II compared with one in the controls. The consequences of these policies for pregnancy rates and the incidence of multiple gestation are discussed. It is concluded that the deliberate limitation of fresh ET to a maximum of one embryo followed by one or more cycles of thawed frozen ET is not detrimental to the pregnancy rate and is less likely to be associated with multiple gestations. Conversely, this policy increases the workload of the laboratory staff and raises certain ethical questions.

Chorionic Gonadotropin↗
PubMed2003

In vitro production of bovine embryos and their application for embryo transfer.

This review introduces newly developed serum-free media (IVD101 and IVMD101), that are effective for producing high yields of transferable embryos of good quality from in vitro-matured and -fertilized oocytes. Both serum-free media produced better results than serum-containing medium, including increased rates of blastocyst formation, post-thaw embryo viability, and pregnancy after transfer. In addition, reduced risks of calf mortality and large calf syndrome were also observed for the serum-free-derived embryos. Serum-derived embryos contained a large number of lipid droplets and immature mitochondria in their cytoplasm that may account for the lower production of transferable embryos and poor embryo quality. A non-invasive technique using scanning electrochemical microscopy was successful in quantitatively measuring oxygen consumption of single embryos. This technique may prove to be reliable for predicting embryo viability and subsequent developmental ability.

Animals↗
PubMed1998

Melatonin treatment of embryo donor and recipient ewes during anestrus affects their endocrine status, but not ovulation rate, embryo survival or pregnancy.

Thirty-two Border Leicester x Scottish Blackface ewes that lambed in March were individually penned with their lambs from April 16th and given daily an oral dose of 3 mg melatonin at 1500 h (Group M). A further 32 acted as controls (Group C). Within each group half were used as embryo donors (Group D) following superovulation and half received embryos (Group R) following an induced estrus. Prior to weaning on 21 May ewes received ad libitum a complete diet providing 9 megajoules (MJ) of metabolizable energy and 125 g/kg crude protein. Thereafter each received 1.6 kg of the diet daily. In early June each ewe received an intravaginal device (300 mg progesterone) inserted for 12 d. Donors were superovulated with 4 i.m. injections of porcine FSH 12 h apart, commencing 24 h before progesterone withdrawal. Ovulation in recipients was induced with 800 IU PMSG injected i.m. at progesterone removal. Donor ewes were inseminated 52 h after progesterone withdrawal. Embryos were collected 4 d later and transferred to recipients. Melatonin suppressed plasma prolactin (P < 0.001) and advanced estrus (P < 0.05) and timing of the LH peak (P < 0.05). These events also occurred earlier in donors than in recipients (P < 0.01). Mean (+/- SEM) ovulation rates for melatonin-treated and control donors were 5.5 +/- 0.71 and 4.7 +/- 0.66, respectively (NS). Corresponding recipient values were 3.3 +/- 0.40 and 3.4 +/- 0.39 (NS). Mean (+/- SEM) embryo yields were 2.9 +/- 0.64 and 2.6 +/- 0.73 for melatonin-treated (n = 15) and control (n = 16) donors, respectively, and for the 12 ewes per treatment that supplied embryos, corresponding numbers classified as viable were 2.7 +/- 0.47 and 2.3 +/- 0.61 (NS). Following transfer, 57% of embryos developed to lambs when both donor and recipient received melatonin, 86% when only the donor received melatonin, 91% when only the recipient received melatonin, and 67% when neither received melatonin (NS). Thus, embryo survival following transfer was not improved by treating recipients with melatonin. Gestation length and lamb birthweights were unaffected by melatonin. Unlike nonpregnant control ewes, melatonin-treated recipients that failed to remain pregnant sustained estrous cyclicity following embryo transfer.

Anestrus↗
PubMed1998

Tubal transfer of bovine embryos: a simple endoscopic method reducing long-term exposure of in vitro produced embryos.

Although numerous trials had shown the need to define a procedure to get free access to the bovine oviduct, there was no adequate report of a technique which was accepted for the routine transfer of early tubal-stage embryos. We have now report an endoscopically mediated transvaginal method for transferring embryos into the oviduct. The in vitro produced embryos were loaded into a curved glass capillary tube which was connected to a perfusor tube plus 1-mL syringe. The capillary tube was directly inserted via the infundibulum into the ampulla. After first having checked the ovaries for the presence of a corpus luteum the embryos were deposited under visual guidance in about 20 to 50 microL medium. Twenty-four Simmental and Brown Swiss heifers received 26 embryos and 9 animals became pregnant, of which 7 recipients delivered 8 live calves. With practice, the time used for endoscopic transfer was reduced to less than 10 min. The results demonstrate that the described technique is suitable for practical application. Especially for the early transfer of IVP-derived embryos this technique might be advantageous. In conclusion, this method is also of great potential interest for the recovery of tubal-stage embryos and for the in vivo culture of embryos followed by conventional flushing at Day 7.

Animals↗
PubMed2005

Lack of Histocompatibility Leukocyte Antigen-G expression in early embryos is not related to germinal defects or impairment of interleukin-10 production by embryos.

The expression of Histocompatibility Leukocyte Antigen (HLA)-G molecules is a mandatory prerequisite for the development of pregnancy but no hypotheses have yet been advanced regarding the lack of HLA-G modulation expression in a percentage of early embryos obtained by in vitro fertilization (IVF). One possible hypothetical model assumes that the absence of regulation of HLA-G or impaired interleukin (IL)-10 secretion could be related to germinal defects. We investigated the presence of soluble HLA-G antigens in supernatants of single embryo cultures from couples admitted to a second fertilization procedure; these couples showed a complete absence of HLA-G modulation in the first cycle's embryo supernatants (0/31). The results obtained in the second IVF cycle showed embryo supernatants positive for HLA-G (14/40), suggesting that the previous lack of antigen modulation is independent of germinal defects. Furthermore, since it has been reported that oocytes and early embryos can secrete IL-10, an anti-inflammatory cytokine produced by type 2 helper T cells that induces upregulation of HLA-G expression in monocytes and trophoblasts, we investigated the levels of IL-10 and soluble HLA-G in 40 embryo culture supernatants from 21 IVF cycles. No associations were observed between the presence of IL-10 and the production and concentrations of soluble HLA-G, or between IL-10 levels and pregnancy outcome. These results indicate that the lack of HLA-G production in early embryos is not related to germinal defects or to impairment in embryo IL-10 secretion but could be ascribed to possible uncorrected fertilization processes.

Embryo, Mammalian↗