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PubMed2006

Oxytocin does not contribute to the effects of cervical dilation on progesterone secretion and embryonic development in mares.

The aim of the present study was, to investigate the effects of oxytocin administration on Day 7 post-ovulation on progesterone secretion, pregnancy rate and embryonic growth in mares. Endogenous stimulation of oxytocin release was compared to the administration of native oxytocin or the long-acting oxytocin analogue carbetocin. At Day 7 after ovulation, mares had to undergo four treatments in a crossover design: (a) control, (b) oxytocin (10 IU i.v.), (c) carbetocin (280 microg i.m.) and (d) cervical dilation. On Day 13, all mares (8 of 8 mares) were pregnant on groups control, oxytocin and carbetocin and only 6 of 8 mares on group dilation. In one mare uterine fluid accumulation and uterine edema from Day 6 to 13 and early embryonic death by Day 11 occurred during dilation treatment. Another mare, which did not become pregnant during dilation treatment, developed uterine fluid accumulation and uterine edema from Day 10 to 14. Mean growth rates of the conceptuses did not differ among treatment groups and individual growth rates varied in a wide range from -0.1 to 0.8 cm per day. At Day 13, mean diameters of conceptuses yielded 1.4+/-0.1 cm in control group, 1.5+/-0.1 in oxytocin and carbetocin group and 1.3+/-0.2 cm in dilation group. Secretion of progesterone was not affected by treatments. Administration of oxytocin and carbetocin caused similar maximum plasma concentrations of oxytocin, but onset and duration of peaks differed. Maximum concentrations after intramuscular application of carbetocin were obtained almost 20 min later when compared to intravenous administration of oxytocin. Duration of peaks after injection of the long-acting oxytocin analogue was more than three-fold longer than after administration of native oxytocin. In conclusion, the present study showed that single administration of oxytocin or its long-acting analogue carbetocin at Day 7 after ovulation did not affect progesterone secretion, pregnancy rate and embryonic growth. Two possible scenarios concerning the effects of cervical dilation were observed: In the majority of mares, dilation of the caudal half to two-third of the cervical lumen up to a diameter of 4.5 cm had no negative consequences on progesterone secretion and pregnancy outcome. However, cervical dilation caused uterine inflammation and subsequent luteolysis in two mares and early embryonic death in one of them. Thus, manipulation of the cervix itself seems not to have negative impact on success rates of transcervical transfer of embryos in the mare.

Animals↗
PubMed1975

The development of microperoxisomes in the cells of the proximal tubules of the kidney and epithelium of the small intestine during the embryonic development and postnatal period.

Microperoxisomes were identified in the cells of proximal tubules of the kidney and small intestine of mice from 13-19 days old embryos, in suckling period and adult animals. Examination of both tissues after incubation in diaminobenzidine medium revealed anucleoid microperoxisomes closely related to the granular endoplasmic reticulum and occasionally found in close relation to it. The number of microperoxisomes within the cells considerably increases with the advanced stage of differentiation of both studies tissues. In the cells of proximal tubules the changes in shape and size of microperoxisomes are also observed with a higher stage of differentiation. These studies indicate that the formation and augmentation of microperoxisomes passes strictly parallelly with the differentiation, i.c. with the ability of cells to perform their specific functions.

3,3'-Diaminobenzidine↗
PubMed2002

DEAF-1 function is essential for the early embryonic development of Drosophila.

The Drosophila protein DEAF-1 is a sequence-specific DNA binding protein that was isolated as a putative cofactor of the Hox protein Deformed (Dfd). In this study, we analyze the effects of loss or gain of DEAF-1 function on Drosophila development. Maternal/zygotic mutations of DEAF-1 largely result in early embryonic arrest prior to the expression of zygotic segmentation genes, although a few embryos develop into larvae with segmentation defects of variable severity. Overexpression of DEAF-1 protein in embryos can induce defects in migration/closure of the dorsal epidermis, and overexpression in adult primordia can strongly disrupt the development of eye or wing. The DEAF-1 protein associates with many discrete sites on polytene chromosomes, suggesting that DEAF-1 is a rather general regulator of gene expression.

Amino Acid Sequence↗
PubMed1996

Xenopus spinal neurons express Kv2 potassium channel transcripts during embryonic development.

Developmentally regulated delayed rectifier potassium currents determine the waveform of the action potential in all Xenopus embryonic primary spinal neurons. To examine this developmental program at the molecular level, we have isolated Xenopus Kv2 potassium channel genes Kv2.1 and Kv2.2. Both genes induce functional heterologous expression of delayed rectifier potassium currents. Transcripts from both Kv2 genes are present in developing embryos; however, only Kv2.2 mRNA is detectable in embryonic spinal neurons. Notably, Kv2.2 transcripts localize to ventral spinal neurons, whereas previously described Kv1.1 transcripts are found in dorsal spinal neurons. Thus, spinal neuron subtypes express distinct potassium channel genes, yet they temporally coordinate functional expression of delayed rectifier potassium currents.

Amino Acid Sequence↗
PubMed2003

Calcium signalling during embryonic development.

Consider a hypothetical design specification for an integrated communication-control system within an embryo. It would require short-range (subcellular) and long-range (pan-embryonic) abilities, it would have to be flexible and, at the same time, robust enough to operate in a dynamically changing environment without information being lost or misinterpreted. Although many signalling elements appear, disappear and sometimes reappear during development, it is becoming clear that embryos also depend on a ubiquitous, persistent and highly versatile signalling system that is based around a single messenger, Ca2+.

Animals↗
PubMed1997

Participation of the female pronucleus derived from the second polar body in full embryonic development of mice.

The second polar body (2PB), extruded from metaphase II oocytes after fertilization or oocyte activation, has a haploid set of female chromosomes like its sister, the fertilized (activated) oocyte. In the present study, the female pronucleus of fertilized mouse oocytes (zygotes) was replaced with the 2PB nucleus from the same or different oocytes to examine the developmental potential of the 2PB nucleus. When the female pronucleus (FPN) was synchronously (FPN and 2PB were same age) replaced with the 2PB nucleus, the rate of reconstructed zygotes developing to blastocysts decreased with the age of donors and recipients (from 70% at 20-21 h to 15% at 26-27 h after hCG injection). When nuclei were replaced asynchronously (FPN and 2PB were of different ages), a higher developmental rate to blastocysts was obtained with young recipient zygotes (20 h after hCG injection) than with aged recipient zygotes (24 h after hCG injection) (64% versus 20%, P < 0.01) irrespective of the age of the 2PB. In this second group of embryos, in which nuclei were replaced asynchronously, the 2PB nuclei were prematurely condensed at the time of first mitosis. These findings indicate that after being extruded from the oocytes the cell cycle of the 2PB progressed more slowly than did that of the zygote. After the transfer of reconstructed embryos into pseudopregnant females, normal pups with an expected coat colour were born, indicating the competence of the 2PB chromosomes for full embryo development.

Animals↗
PubMed2004

Effect of treating induced mitochondrial damage on embryonic development and epigenesis.

Germinal vesicle transplantation (GVT) has been proposed as a possible treatment to correct age-related oocyte aneuploidy caused by dysfunctional ooplasm. How healthy ooplasm regulates normal meiosis and subsequent development has yet to be elucidated, but impaired mitochondrial metabolism may be attributable to incomplete segregation of the oocyte chromosomes. In the present study, after ooplasmic mitochondrial damage by photoirradiating chloromethyl-X-rosamine, examination of the oocyte nuclei's ability to survive after transfer into healthy ooplasts was performed. To assess their fertilizability and potential for development, GVT oocytes were fertilized by intracytoplasmic sperm injection (ICSI) and transferred to foster mice. Condition of the offspring at birth was assessed, and epigenetic analysis was performed. Photosensitization consistently inhibited oocyte maturation. However, after GVT of photosensitized nuclei into healthy ooplasts, 67.2% were reconstituted, and 76.2% of these matured normally, with an overall rate of 51.2%, much higher than that (6.0%) in the mitochondrially injured oocytes. After ICSI, 65.8% (52/79) of GVT oocytes were fertilized normally, and 21.1% (11/52) eventually reached the blastocyst stage. The transfer of 132 two-cell GVT embryos into the oviducts of pseudopregnant females resulted in 17 apparently healthy live offspring. For some key developmental genes, a high level of expression was identified in the GVT and "rescue"-derived fetal adnexa. Thus, one can induce in oocyte mitochondria a photosensitization-based type of damage, which consistently inhibits GV breakdown, meiotic spindle formation, chromosomal segregation, and polar body extrusion. Germinal vesicle transplanted and rescued oocytes were able to undergo maturation, fertilization, and embryonic cleavage and, ultimately, to develop to term. This approach may provide a model with which to study the age-related ooplasmic dysfunction seen in human oocytes.

Animals↗
PubMed1991

The thyroid hormone receptor gene (c-erbA alpha) is expressed in advance of thyroid gland maturation during the early embryonic development of Xenopus laevis.

The c-erbA proto-oncogene encodes the thyroid hormone receptor, a ligand-dependent transcription factor which plays an important role in vertebrate growth and development. To define the role of the thyroid hormone receptor in developmental processes, we have begun studying c-erbA gene expression during the ontogeny of Xenopus laevis, an organism in which thyroid hormone has well-documented effects on morphogenesis. Using polymerase chain reactions (PCR) as a sensitive assay of specific gene expression, we found that polyadenylated erbA alpha RNA is present in Xenopus cells at early developmental stages, including the fertilized egg, blastula, gastrula, and neurula. By performing erbA alpha-specific PCR on reverse-transcribed RNAs from high-density sucrose gradient fractions prepared from early-stage embryos, we have demonstrated that these erbA transcripts are recruited to polysomes. Therefore, erbA is expressed in Xenopus development prior to the appearance of the thyroid gland anlage in tailbud-stage embryos. This implies that erbA alpha/thyroid hormone receptors may play ligand-independent roles during the early development of X. laevis. Quantitative PCR revealed a greater than 25-fold range in the steady-state levels of polyadenylated erbA alpha RNA across early stages of development, as expressed relative to equimolar amounts of total embryonic RNA. Substantial increases in the levels of erbA alpha RNA were noted at stages well after the onset of zygotic transcription at the mid-blastula transition, with accumulation of erbA alpha transcripts reaching a relative maximum in advance of metamorphosis. We also show that erbA alpha RNAs are expressed unequally across Xenopus neural tube embryos. This differential expression continues through later stages of development, including metamorphosis. This finding suggests that erbA alpha/thyroid hormone receptors may play roles in tissue-specific processes across all of Xenopus development.

Animals↗
PubMed1991

Some neuronal cell populations express human dopamine beta-hydroxylase-lacZ transgenes transiently during embryonic development.

The 5' flanking region from the human dopamine beta-hydroxylase gene directs expression of bacterial beta-galactosidase reporter genes to a subset of adult neurons and adrenal chromaffin cells of transgenic mice. In this paper, we examine the spatial and temporal patterns of expression of these transgenes during embryogenesis. Expression begins at embryonic day 9 in the developing central and peripheral nervous systems and persists in cell populations in which expression is observed in adult transgenic mice. However, transient embryonic expression occurs in presumptive neuroblasts in developing sensory ganglia and ventrolateral neural tube that are destined to synthesize neurotransmitters other than catecholamines. These observations support the concept that some cells fated to become "non-catecholaminergic" neurons exhibit transient catecholaminergic features during their differentiation.

Animals↗
PubMed1996

Pluripotent bovine embryonic cell lines direct embryonic development following nuclear transfer.

Nuclear transfer (NT) procedures were used to determine the in vivo developmental capacity of bovine embryonic cell lines derived from both morula- and blastocyst-stage embryos. These cell lines differed in morphology from trophoblast and endoderm-like cells. Regardless of initial donor embryo stage, cells in the resulting bovine embryonic cell lines had a small cytoplasmic/nuclear volume ratio and contained cytoplasmic vesicles. Developmental rates to blastocyst stage for NT embryos were improved when smaller cells (15 microns) rather than larger cells (18 microns or 21 microns) were used in the NT procedure and the recipient oocyte was activated after the cell fusion step. NT embryos produced from these embryonic cell lines, both morula- and blastocyst-derived, initiated pregnancies following transfer into recipient females. However, all of these pregnancies were lost prior to 60 days of gestation. These NT embryos were able to direct development through organogenesis, with one NT fetus reaching 55 days before death. When viable NT embryos were recovered during early gestation (38 days), an absence of cotyledons and a hemorrhagic response in the caruncles were observed. A chimera produced by aggregating an NT embryo with two 8-cell-stage blastomeres from in vitro-produced embryos developed through the 85th day of gestation. However, this conceptus was also deficient of cotyledons. DNA markers indicated that 50% of the chimera conceptus tissues were derived from the embryonic cell line. Blastocyst- and morula-derived embryonic cell line nuclei are pluripotent in that they can direct development through organogenesis, with subsequent pregnancy loss due, at least in part, to a deficiency in placentome development.

Animals↗
PubMed2005

Full-term development of mouse eggs transplanted with male pronuclei derived from round spermatids: the effect of synchronization between male and female pronucleus on embryonic development.

Pronucleus transplanted mice have been produced, but their donor male pronuclei were derived from mature sperm and were completely synchronous with female pronuclei because both male and female pronuclei came from the same fertilized oocyte. The present study firstly produced male pronuclei by introducing round spermatids into enucleated mouse oocytes, then transferred the male pronuclei into mouse oocytes at three activation stages and finally compared the effect of three kinds of oocytes on the development of reconstructed embryos. Our results indicate that, in enucleated oocytes, mouse round spermatid nuclei can transform to male pronuclei in a higher proportion, and the synchronization between male and female pronucleus does not significantly influence the early cleavage but the later and full-term development of reconstructed embryos.

Animals↗