Early Embryonic Loss Research Articles

Apoptosis in the human embryo

Preimplantation human embryos are characterized by various degrees of cytoplasmic fragmentation, and a high incidence of developmental arrest before the blastocyst stage. This review examines the current morphological and biochemical evidence that apoptosis plays a role in early human development and embryonic loss. Embryos examined 24 h or more after arrest often show characteristic features of apoptosis including cytoplasmic, nuclear and DNA fragmentation. In contrast, embryos of good morphology that appear to be developing normally show no evidence of apoptosis before compaction. However, at the morula and blastocyst stages, scattered cells with fragmented nuclei and DNA characteristic of cells undergoing apoptosis are common features. Apoptosis may result from suboptimal culture conditions, or may be involved in the elimination of abnormal cells. However, the causes, role and regulation of apoptosis in the human preimplantation embryo remain to be determined.

Apoptosis in the human embryo.

Preimplantation human embryos are characterized by various degrees of cytoplasmic fragmentation, and a high incidence of developmental arrest before the blastocyst stage. This review examines the current morphological and biochemical evidence that apoptosis plays a role in early human development and embryonic loss. Embryos examined 24 h or more after arrest often show characteristic features of apoptosis including cytoplasmic, nuclear and DNA fragmentation. In contrast, embryos of good morphology that appear to be developing normally show no evidence of apoptosis before compaction. However, at the morula and blastocyst stages, scattered cells with fragmented nuclei and DNA characteristic of cells undergoing apoptosis are common features. Apoptosis may result from suboptimal culture conditions, or may be involved in the elimination of abnormal cells. However, the causes, role and regulation of apoptosis in the human preimplantation embryo remain to be determined.

Adverse effects of diphenyltin dichloride on initiation and maintenance of pregnancy in rats

The objective of this study was to characterize the adverse effects of diphenyltin dichloride (DPTCl) during early pregnancy. Following successful mating, female rats were given DPTCl by gastric intubation at 0, 4.1, 8.3, 16.5, 24.8 or 33.0 mg/kg on days 0–3 or days 4–7 of pregnancy. Female rats were sacrificed on day 20 of pregnancy and pregnancy outcome was determined. The pregnancy rate was significantly decreased after administration of DPTCl on days 0–3 at 24.8 mg/kg and on days 4–7 at 33.0 mg/kg. The incidence of preimplantation loss was significantly increased after administration on days 0–3 at 16.5 mg/kg and above and on days 4–7 at 33.0 mg/kg. In females having implantations, the numbers of implantations and live fetuses and the incidences of pre- and postimplantation loss in the groups given DPTCl on days 0–3 were comparable to the controls. The incidence of postimplantation loss was significantly increased after administration of DPTCl on days 4–7 at 33.0 mg/kg. A pair-feeding study revealed no evidence of pre- and postimplantation embryolethality induced by food restriction. It could be concluded that DPTCl during early pregnancy causes early embryonic loss and DPTCl has greater effects on reproduction when administered during earlier than later stages of blastogenesis.

Early embryonic loss in x-autosome translocation carrier sows

Early embryonic loss in x-autosome translocation carrier sows

The effect of reducing feed intake following insemination on embryo survival in cattle

In farm animals early embryonic loss is recognised as a major cause of reproductive wastage. In sheep and pigs there is evidence that high energy intakes prior to ovulation and in early pregnancy depress systemic progesterone with a detrimental effect on embryo survival. The objective of this study was to investigate the effect of short term nutritional changes pre- and post-insemination on embryo survival and systemic progesterone in cattle. Preliminary results have been presented previously (Dunne etal., 1997).Oestrus was synchronised in 247 beef cross heifers aged 18-24 months using two injections of prostaglandin (PG) administered 10 days apart. At the oestrus following the first PG injection heifers were allocated to either a Low (L, 0.6 M) or High (H, 2.3M) pasture allowance for the 10 day period prior to artificial insemination (AI). AI was carried out at the oestrus following the second PG injection using semen from a single Limousin bull. On the day following AI, heifers were randomly reallocated to either a L or H pasture allowance until embryo recovery at day 14 to 16 or pregnancy diagnosis at Day 30.

The effect of dietary protein on reproduction in the mare. VII. Embryonic development, early embryonic death, foetal losses and their relationship with serum progestagen.

Sixty-four Thoroughbred and Anglo-Arab mares aged 6-12 years were randomly allocated to 4 dietary groups and fed diets that differed in the total protein content and quality (essential amino-acids). Forty mares were non-lactating and 24 lactating. Eight mares were withdrawn from the investigation owing to injuries or gynaecological pathology. An overall conception rate of 94.6% and a foaling rate of 80% was achieved. Five of 14 (35.7%) mares (Group 1) fed a low-quality protein diet suffered from early embryonic loss before 90 days of pregnancy compared to 3 of 41 (7.3%) mares in the remaining groups that received the higher-quality protein in their diets. Serum progestagen concentrations of mares in Group 1 that suffered foetal loss were indicative of luteal function insufficiency during the 1st 40 days post-ovulation. Non-lactating mares in all 4 groups gained on average approximately 30 kg in mass during the 90 days before the breeding period. Lactating mares in Group 1 (low-quality protein) lost on average 25 kg in mass during lactation, with no weight loss observed among the lactating mares in the other 3 groups. No difference in the diameter of the embryonic vesicle was found between dietary groups until Day 35 of pregnancy.

Relationship between peripheral estrogen concentrations at insemination and subsequent fetal loss in cattle

In a survey on pregnancy rate and embryonic losses in dairy cattle on 6 Israeli farms, cows (n=78) were divided into 3 groups on the basis of ultrasonography at 21 d post insemination; pregnancy diagnosis at 40 to 50 d post insemination and blood progesterone (P 4) levels at 21 d. The groups were either pregnant (P 4 level >1.0 ng/mL); not pregnant (P 4 <0.5 ng/mL), or showed early embryo loss (P 4 >1.0 ng/mL and the presence of an embryonic vesicle on D 21 but later returned to estrus or were found not pregnant on D 40 to 50). On the day of insemination, peripheral estrogen was significantly higher (P <0.05) in the early embryo loss group (15.3±1.1 pg/mL, n=27). than in pregnant (9.4±0.6 pg/mL, n=26) or not pregnant (9.6±0.7 pg/mL, n=25) group. The cows on 3 farms which were fed 1 to 2 kg/d of vetch ( Vicia sativa ), an estrogenic legume, had higher estrogen concentrations on the day of insemination than cows (2 farms) fed other legumes (13.7±0.64, n=58 vs 10.7±0.8 pg/mL, n=42; P<0.01). On one of the 3 farms, vetch was replaced with alfalfa after the first year. Following the cessation of vetch feeding the estrogen concentrations in the blood decreased from 32±5 pg/mL to 14±2 pg/mL (n=9). These data suggest that high peripheral estrogen on the day of insemination is associated with early embryonic loss. These data also indicate that estrogen concentrations on the day of insemination can be influenced by diet.

Maternal recognition of foetal infection with bovine virus diarrhoea virus (BVDV)—the bovine pestivirus

Background: Pestiviruses are the veterinary viruses with genome homology to human hepatitis C virus (HCV). This group includes classical swine fever virus (CSFV), border disease virus of sheep (BDV) and bovine virus diarrhoea virus (BVDV). There are some similarities in the pathology of all three virus infections; in utero transmission to the foetus can cause early embryonic losses, severe congenital abnormalities and, particularly with BVDV, lifelong persistent infections. In situ hybridisation studies have demonstrated virus within reproductive tissues and the germinal centres of lymphoid tissue. Objectives: To examine the immune response of cattle throughout their pregnancy following infection with bovine pestivirus (BVDV) during the first trimester (before 110 days). Study design: In two experimental studies, heifers were infected with BVDV before 98 days gestation. Their antibody response was monitored during the remainder of the pregnancy. In another study, the antibody response of pregnant cattle was monitored following a natural infection of BVDV on a farm. Calves of the dams from all these three studies were examined, following birth, for persistent BVDV infection. Results: It was observed that in dams carrying persistently infected foetuses, the immune response was markedly higher (13 811±1273 U ELISA antibody) than in those dams carrying uninfected foetuses (2542±588 U ELISA antibody). These results were used to establish an antibody threshold (10 000 U ELISA antibody) to predict the virus status of unborn calves during a farm outbreak of BVDV infection. The combined results of experimental and farm studies showed that in dams with low antibodies, 5/15 calves were infected whereas in dams with high antibodies, 17/19 calves were infected. Conclusions: The predictive reliability of the assay appeared valuable but not secure. The ability of BVDV to infect the foetus with consequent maternal recognition, whilst remaining inaccessible to maternal immune exclusion, is a novel finding.

Reproductive effects of butyl benzyl phthalate in pregnant and pseudopregnant rats

In our previous studies, butyl benzyl phthalate (BBP) was found to be embryolethal and teratogenic in rats. In this study, the reproductive effects of BBP were investigated in pregnant and pseudopregnant rats. Rats were given BBP by gastric intubation at 0, 250, 500, 750, or 1000 mg/kg on Days 0 to 8 of pregnancy and the pregnancy outcome was determined on Day 20 of pregnancy. The same doses of BBP were given to pseudopregnant rats, with an induced decidual cell response on Days 0 to 8 of pseudopregnancy, and the uterine weight on Day 9 served as an index of the uterine decidualization. BBP caused significant increases in the incidences of preimplantation loss in females successfully mated at 1000 mg/kg and of postimplantation loss in females having implantations at 750 mg/kg and above. Uterine decidual growth in pseudopregnant rats was significantly decreased at 750 mg/kg and above. These findings suggest that early embryonic loss due to BBP may be mediated, at least in part, via the suppression of uterine decidualization, an impairment of uterine function.

Long-term stability of the bovine block to polyspermy.

Under most circumstances in eutherian mammals, mating occurs before ovulation and a defense against multiple sperm penetration of the zygote is established rapidly after fertilisation. It is generally assumed that this block to polyspermy is both stable and long-lasting, but these points have not been specifically tested. They assume particular significance in domestic farm animals in which procedures of artificial insemination could mistakenly introduce sperm suspensions into a genital tract already containing a fertilised egg. Bovine blastocysts generated in vitro were further exposed in vitro to new suspensions of capacitated bull spermatozoa containing 1.5 x 10(6) cells per ml on days 7 or 8 of development, that is, shortly before or after hatching from the zona pellucida. Inseminated and control blastocysts were examined by light or electron microscopy. Whereas accessory spermatozoa were frequently bound to the surface of the zona pellucida, non had penetrated into the substance of the zona. Similarly, whilst a few spermatozoa had attached to the trophoblast of hatched blastocysts on day 8, none had penetrated through to the blastocoele. No difference was found in the incidence of hatching or rate of expansion between experimental (re-inseminated) and control groups. Accordingly, it is concluded that the bovine block to polyspermy is both stable and long-lasting when tested in vitro in the presence of freshly capacitated bull spermatozoa. Early embryonic loss, which may reach a level of 30% or more in this species, is thus unlikely to be a consequence of instability in the block to polyspermy and accessory sperm penetration of the zygote.

Evaluation of early embryonic loss induced by tributyltin chloride in rats: phase- and dose-dependent antifertility effects.

In our previous study, tributyltin chloride (TBTCl) on days 0-7 of pregnancy was found to produce implantation failure in rats. The objective of the present study was to determine the susceptible period for the antifertility effect of TBTCl in rats. Inseminated females were orally administered TBTCl at 8.1, 16.3, or 32.5 mg/kg on days 0-3 of pregnancy, or at 8.1, 16.3, 32.5, or 65.1 mg/kg on days 4-7 of pregnancy. Pregnancy outcome was determined on day 20 of pregnancy. Dosing with TBTCl on days 0-3 of pregnancy at 16.3 mg/kg and higher produced a significant increase in the rate of implantation failure. Dosing with TBTCl on days 4-7 of pregnancy caused a significant increase in the incidence of postimplantation loss at 16.3 mg/kg and higher in females with implantations. No increase in the incidence of fetal malformations was found in any TBTCl-treated groups. It could be concluded that the susceptibility to and manifestation of the antifertility effects of TBTCl vary with the gestational stage at the time of administration.

Cre-mediated chromosome loss in mice.

Chromosome loss in early human embryos is thought to cause a large proportion of spontaneous abortions; when it occurs in specific cell lineages in older embryos or adults, it can result in neoplasia. Although early embryonic chromosome loss can be modelled by breeding mice carrying robertsonian translocation chromosomes, there is currently no method for producing mice with tissue-specific monosomies. Here we demonstrate that DNA recombination mediated by the site-specific recombinase Cre causes loss of a chromosome carrying loxP sites (Cre recognition sites) in an inverted orientation. Thus, when male mice carrying a Y-linked transgene containing inverted loxP sites are mated with females carrying a cre gene that is obiquitously expressed in the early embryo, almost all their XY progeny lose the Y chromosome early in embryogenesis and develop as XO females. Because inverted loxP sites can be targetted to any mouse chromosome and mice can be produced that express cre in specific cell lineages, these data suggest a method for engineering tissue-specific loss of particular chromosomes to provide mouse models for human diseases caused by or associated with specific monosomies.

Early Embryonic Losses After Oocyte Donation

Early Embryonic Losses After Oocyte Donation

P-114 Early embryonic losses after oocyte donation

P-114 Early embryonic losses after oocyte donation

Developmental Toxicology Evaluation of 60-Hz Horizontal Magnetic Fields in Rats

Abstract Epidemiological and laboratory studies have indicated various biological effects resulting from exposure to extremely low frequency magnetic fields. The possibility of early embryonic loss and fetal malformations arising from such exposures required investigation. A replicate study, using large numbers of animals, was conducted to determine if 60-Hz magnetic fields would produce developmental toxicity in rats. Systems used previously for electric field exposures were retrofitted to provide magnetic field exposures to small laboratory animals. Large coils, separated from the rat cages, were energized by computer-controlled function generators providing a relatively pure, 1000-μT, 60-Hz, horizontal magnetic field for the high exposure group. Leakage fields to a second system provided a second exposure group with average exposures of 0.61 μT. Ambient fields within a third (control) system were 0.09 μT. Field intensities utilized in this study represent a range of exposures encountered by humans; however, they do not encompass the extremes of human exposure. Mated female rats were exposed for 20 h/day from the day of mating until very near term, 20 days later. Gestational body weight gain was not different in exposed animals when compared with control animals. Evaluation of uterine contents revealed a decrease in the number of fetuses per litter in rats exposed to 1000 μT in replicate A. This decrease, however, did not repeat in replicate B, and significant differences between groups could not be statistically confirmed in combined replicate data. Fetal body weight and incidences of malformations and variations were equivalent among the groups. As tested, 60-Hz magnetic fields of intensities at or below the 1000-μT level would not be classified as either embryotoxic, fetotoxic, or teratogenic in rats.

The role for the uterine insulin-like growth factor I in early embryonic loss after superovulation in the rat

To examine possible roles of the insulin-like growth factor (IGF) system in increased early embryonic loss after superovulation. Changes in the uterine IGF system were examined in superovulated rats. Insulin-like growth factor I (IGF-I) was infused to the right uterine horns to mimic enhanced IGF-I actions after superovulation. Uterine luminal fluids were collected after IGF-I infusions and embryos were cultured with uterine luminal fluids. Steroid hormones, IGF-I, IGF binding protein (IGFBP), and IGF-I receptor levels, developmental rate, and cell numbers of embryos. Elevated IGF-I levels and suppressed IGFBP levels were found from days 1 to 3 of pregnancy after superovulation. Uterine luminal fluids of the IGF-I infusion and superovulation groups impaired embryo development in vitro. Anti-IGF-I antibody infusions after superovulation reversed detrimental effects of superovulation. Dialysis of uterine luminal fluids of the IGF-I infusion and superovulation groups before culture improved embryo development. Enhanced IGF-I actions in the uterus after superovulation may be responsible for the increase of early embryonic loss. The detrimental factor for embryo development seems a small molecule and is likely a local product of the uterus in which IGF-I actions are enhanced.

Livestock Environment Prospects for the 90's

When projecting livestock environmental prospects for the 1990's. it is critical to recognize the multidimensional nature of managing livestock species under hot environments. This paper identifies potential critical physiological windows during the life cycle of the animal that are sensitive to heat stress and responsive to environmental modification. Ovarian follicular development appears to be sensitive to heat stress leading to reductions in intensity of oestrus and subsequent fertility. Periods of follicular development that are sensitive to heat stress have not been defined. With current improved systems to alter the microenvironment of animals. the period of embryonic sensitivity to heat stress has shifted so that early embryonic losses are less. Potential recombinant proteins that may enhance embryo survival and correct deficiencies in placental function that are induced by heat stress warrant additional investigation. The postpartum period is a critical period in which a multitude of factors interact to influence animal productivity and its sensitivity to heat stress. Nutritional strategies to improve animal performance with the use of fat-supplementation are discussed. Environmental modification and housing systems need to not only maximize the efficiency of animal production but need to consider the potential impact on the environment relative to water use. soil and water pollution. Animal production and management systems need to consider both animal health and well-being issues. To optimize profit under conditions of greater societal constraints and available management alternatives, computer assisted management systems will become a critical tool.

Production of twin calves with in vitro fertilised embryos: effects on the reproductive performance of dairy cows

Attempts were made to produce twin calves by implanting in vitro fertilised and matured (IVF) embryos into dairy cows. Twinning rates were consistently at the lower end of the range reported to have been obtained with in vivo derived embryos. The low pregnancy rates, higher than expected early embryonic losses, and increased fetal deaths and abortions recorded may indicate that IVF embryos are less viable. Fetal oversize in single calves was a significant problem in the first two years of the trial. The subsequent conception rates of cows that calved twins and those that calved singles were similar in spite of a much higher incidence of retained placenta and an increased interval to first oestrus in the cows bearing twins.

Transvaginal Ultrasonography of the First Trimester Embryo: The First Eight Weeks of Gestation

High resolution diagnostic ultrasonography has allowed for accurate and reliable evaluation of the developmental changes which occur early in pregnancy. The ability to determine the presence or absence of a gestational sac, to assess embryonic viability, to determine the number of embryos, and to evaluate the pregnancy associated changes in the ovaries and uterus have forever changed our perceptions of the life of an embryo. It is important to understand the normal changes associated with early pregnancy before delving into complications and pathology. The corpus luteum is an essential part of early embryonic life and it must be evaluated as part of a routine assessment of early pregnancy. The process of endometrial decidualization and the uterine changes associated with implantation are described as they form the base upon which many forms of early embryonic loss may be understood better. The concept of the “discriminatory zone” representing the level at which an intrauterine gestational sac must be visualized within the uterus is described in detail. The “discriminatory zone” is dependent upon both the sensitivity of the clinical laboratory processing the patient’s serum for βhCG levels and the ultrasonography suite, its instrumentation, and interpreters. Finally, normal developmental changes in the embryo proper are described and a scheme for estimation of gestational age is presented. New observations obtained from transvaginal ultrasonography combined with known dates of ovulation are integrated with findings generated by transabdominal ultrasonography, last menstrual period (LMP) dates, and anatomic studies to stimulate discussion of new normative data for highly accurate estimation of early gestational age. It is of the utmost importance that physicians recognize normal developmental morphology in the first trimester in order to understand the problems that lead to early pregnancy failure and to apply appropriate interventional therapies.

Effect of persistent follicles on early embryonic losses in beef cows.

Low doses of progestogens in regimens for synchronization of estrus result in persistent follicles (PF) and reduced conception rates in cattle. The effects of PF on recovery of oocytes/embryos, fertilization, and embryonic development were examined in beef cows. To produce PF, cows received a used Controlled Internal Drug Releasing device on Days 4 through 13 after pretreatment estrus (Day 0) and two injections of 20 mg prostaglandin (PG) F2 alpha, i.m., 12 h apart on Day 6 (PF; n = 20). Control cows received only PGF2 alpha on Day 6 so they would ovulate growing follicles (GF; n = 22). With this model, the largest (dominant) follicle from the first wave of follicular development was being ovulated in cows in each group. Cows were observed for estrus twice daily and were then mated to highly fertile bulls. Follicular development was monitored by ultrasonography on alternate days from Day 2 until estrus and then daily until apparent ovulation. Jugular blood samples were collected every other day from Day 2 through 6 days after mating at posttreatment estrus, when uteri were flushed nonsurgically. The ovulatory follicle, which was followed retrospectively and had been observed longer (14 +/- 1 vs. 8 +/- 1 days), was larger in PF (17.2 +/- 0.5 mm) than in GF (14.5 +/- 0.6 mm; p < 0.01). Mean estradiol-17 beta (E2) in jugular plasma during the 6 days before estrus was higher in PF than in GF (5.7 +/- 0.4 vs. 2.6 +/- 0.4 pg/ml; p < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)