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PubMed1989

Selection for B cells with productive IgL gene rearrangements occurs in the bursa of Fabricius during chicken embryonic development.

The vast majority of immunoglobulin-expressing mature chicken B lymphocytes contain one functionally rearranged and one unrearranged allele of the immunoglobulin light chain (IgL) gene. Therefore, nearly all IgL V-J rearrangements present in mature chickens are in-frame. In contrast, the Ig genes of mature mammalian B cells contain a high proportion of out-of-frame V-J joints. To investigate the basis for this difference, gene rearrangement at the chicken IgL locus was characterized during embryonic development and in mature B-cell lines. Joining of the single functional variable (VL) segment with the single joining (JL) segment occurs in cells in multiple tissues during a transient period of chicken embryogenesis. Only one-third of the V-J joints cloned from days 10-12 of development are in-frame. An increasing proportion of in-frame V-J joints is observed within the bursa of Fabricius at successively later stages of development. Our data suggest that the bursa of Fabricius serves during embryonic development as a site of selective amplification of cells that have undergone productive V-J joining, such that nearly all V-J joints present in postembryonic B cells are in-frame. The high frequency of rearranged alleles joined in-frame that is found in posthatching bursal cells and mature B-cell lines appears to result from a low frequency with which cells undergo IgL rearrangement at both alleles, rather than from an increase in the precision of V-J joining in avian species.

Alleles↗

PubMed1990

Influence of superovulation on endometrial and embryonic development.

The authors have studied the temporal relationship between follicular rupture and endometrial development in 13 women during a natural ovarian cycle (length 25 to 35 days), and subsequently after standard treatment with clomiphene citrate, human menopausal gonadotropin and human chorionic gonadotropin (hCG) to induce multiple folliculogenesis for oocyte recovery, in vitro fertilization, and embryo freezing (cycle length 23 to 27 days). An endometrial biopsy was taken during both cycles 1.5 to 2.0 days after the oocytes had been released or removed. The samples were examined by light and transmission electron microscopy. Samples of peripheral blood were taken at defined times for hormone analysis. After treatment 11 subjects (85%) had advanced morphological development of the endometrium (8 women by 3 to 4 days, 3 women by 1 to 2 days). The concentrations of plasma estradiol (E2) and progesterone (P) on the days of follicular rupture and endometrial biopsy were significantly raised in the treatment cycles. The concentration of total urinary estrogens on the day of hCG administration and the mean change in the concentration of plasma E2 (treatment/control) on the days of endometrial biopsy were positively correlated with the extent of endometrial advancement. In addition, the mean change in the concentration of plasma P (treatment/control) was markedly increased on the days of follicular rupture and endometrial biopsy in those subjects with an advanced endometrium. Embryonic development was not so obviously related to the extent of superovulation. Asynchronous endometrial and embryonic development may therefore contribute to the low pregnancy rate in these patients.

Adult↗

PubMed1990

Embryonic development of four different subsets of cholinergic neurons in rat cervical spinal cord.

The developmental stage at which a neuron becomes committed to a neurotransmitter phenotype is an important time in its ontogenetic history. The present study examines when choline acetyltransferase (ChAT) is first detected within each of four different subsets of cholinergic neurons previously identified in the cervical enlargement of the spinal cord: namely, motor neurons, partition cells, central canal cluster cells, and dorsal horn neurons. By examining the temporal sequence of embryonic development of these cholinergic neurons, we can infer the relationships between ChAT expression and other important developmental events. ChAT was first detected reliably on embryonic day 13 (E13) by both biochemical and immunocytochemical methods, and it was localized predominantly within motor neurons. A second group of primitive-appearing ChAT-positive cells was detected adjacent to the ventricular zone on E14. These neurons seemed to disperse laterally into the intermediate zone by E15, and, on the basis of their location, were tentatively identified as partition cells. A third group of primitive ChAT-immunoreactive cells was detected on E16, both within and around the ventral half of the ventricular zone. By E17, some members of this "U"-shaped group appeared to have dispersed dorsally and laterally, probably giving rise to dorsal horn neurons as well as dorsal central canal cluster cells. Other members of this group remained near the ventral ventricular zone, most likely differentiating into ventral central canal cluster cells. Combined findings from the present study and a previous investigation of neurogenesis (Phelps et al.: J. Comp. Neurol. 273:459-472, '88), suggest that premitotic precursor cells have not yet acquired the cholinergic phenotype because ChAT is not detectable until after the onset of neuronal generation for each of the respective subsets of cholinergic neurons. However, ChAT is expressed in primitive bipolar neurons located within or adjacent to the germinal epithelium. Transitional stages of embryonic development suggest that these primitive ChAT-positive cells migrate to different locations within the intermediate zone to differentiate into the various subsets of mature cholinergic neurons. Therefore, it seems likely that spinal cholinergic neurons are committed to the cholinergic phenotype at pre- or early migratory stages of their development. Our results also hint that the subsets of cholinergic cells may follow different migration routes. For example, presumptive partition cells may use radial glial processes for guidance, whereas dorsal horn neurons may migrate along nerve fibers of the commissural pathway. Cell-cell interactions along such diverse migratory pathways could play a role in determining the different morphological, and presumably functional, phenotypes expressed by spinal cholinergic neurons.

Animals↗

PubMed1995

Comparative embryonic development in chickens with different patterns of postnatal growth.

We compared embryonic development of two lines of chickens that exhibit different patterns of postnatal growth. Classical staging techniques and morphological measurements of bone, cartilage, feather and intestines were used to test the hypothesis that differences in postnatal growth would be reflected in patterns of embryonic tissue partitioning. During the second quarter of incubation, the line with higher postnatal growth staged significantly earlier (i.e., was less developed overall) than the line with lower postnatal growth. Embryos from the line with higher postnatal growth exhibited less (i.e., allocated away from), bone growth (beak length, ossification of long bones), feather growth (number of feather papillae, length of primary), and eye development (number of lens sclera). There were no differences in gut development between the two lines. Our results show that different postnatal growth patterns are associated with changes in the pattern of embryonic reallocation between tissue types, even when gross morphological differences are not evident at hatching. We suggest that these differences in development represent periods when the embryo is allocating to hyperplastic growth of tissues such as muscle, as a means of increasing posthatching growth potential.

Animals↗

PubMedDate not supplied

In vitro assessment of individual and interactive effects of aromatic hydrocarbons on embryonic development of the rat.

There have been reports of disruption of embryonic development following exposure of pregnant women to aromatic hydrocarbons. In the present study, the embryotoxicity of toluene, xylene, benzene, styrene, and its metabolite, styrene oxide, was evaluated using the in vitro culture of postimplantation rat embryos. Possible interactions between toluene, xylene, and benzene were also studied using mixtures of these solvents. The results of the study showed that toluene, xylene, benzene, and styrene all have a concentration-dependent embryotoxic effect on the developing rat embryo in vitro. Styrene was embryotoxic at a lower concentration (1.00 mumol/mL) than benzene (1.56 mumol/mL), toluene (2.25 mumol/mL), or xylene (1.89 mumol/mL). The metabolite of styrene, styrene oxide, was embryotoxic at a concentration (0.038 mumol/mL). more than 20 times less than the parent compound. There was no evidence of a synergistic interaction between toluene, xylene, and benzene in causing embryotoxicity; the solvents interacted in an additive manner. The embryos were exposed to the solvents for 40 h of the organogenic period. When the levels of solvents found to be embryotoxic in the present study are compared to blood levels in the human following industrial exposure or solvent abuse, it appears unlikely that the threshold blood levels for embryotoxicity would be exceeded in the workplace. However, the possibility that exposure to solvents earlier or later or throughout the entire organogenic period might result in a different conclusion cannot be excluded.

Animals↗

PubMed2002

A human homologue of mouse Mater, a maternal effect gene essential for early embryonic development.

BACKGROUND: Mater is a maternal effect gene required for early embryonic development in mice, and its protein serves as an autoantigen in a mouse model of autoimmune premature ovarian failure. METHODS: Human MATER cDNA was cloned by PCR techniques. The mRNA and protein were determined using hybridization and immunodetection respectively. The cDNA and protein sequences were analysed using bioinformatics software. RESULTS: Human MATER gene spans a approximately 63 kbp DNA at chromosome 19 and is composed of 15 exons and 14 introns. Expression of its mRNA (approximately 4.2 kb) is restricted to the oocytes. Human MATER cDNA (3885 nt) shows an open reading frame (3600 nt) encoding a polypeptide chain composed of 1200 residues with a predicted molecular mass of 134 236 Da. MATER protein (approximately 134 kDa) was detected in human oocytes. The human and mouse cDNA share 67% homology while their deduced polypeptide chains have 53% identity of amino acids. Also, their protein structures have a number of similar features. CONCLUSIONS: The human MATER and mouse Mater genes and proteins are conserved. Characterization of the human MATER and its protein provides a basis for investigating their clinical implications in autoimmune premature ovarian failure and infertility in women.

Amino Acid Sequence↗

PubMed2003

Proline365 is a critical residue for the activity of XMI-ER1 in Xenopus embryonic development.

Xmi-er1 is an immediate-early gene encoding a transcriptional regulator whose expression is activated by fibroblast growth factor (FGF) during mesoderm induction in Xenopus. In this study, we examined the role of xmi-er1 in embryonic development and mesoderm induction and investigated the importance of various functional domains in the protein sequence. Overexpression of xmi-er1 in embryos resulted in truncations of the anteroposterior axis, with most of the abnormal embryos exhibiting deficiencies in both anterior and posterior structures. Whole mount in situ hybridization for the early mesodermal marker brachyury (Xbra) revealed a dramatic reduction of Xbra expression in xmi-er1-injected embryos, while mesoderm induction assays showed that overexpression of xmi-er1 significantly reduced the percentage of explants induced by FGF-2. Site-directed mutagenesis of several functional domains, including the ELM2 domain, the SANT domain, a putative MEK phosphorylation site, and a proline-rich region showed that only proline 365 in the proline-rich region is required for the effect on embryonic development and mesoderm induction. These data demonstrate that XMI-ER1 is a negative regulator of FGF, perhaps serving to limit the extent of mesoderm formation in vivo, and that this activity is mediated by proline 365.

Animals↗

PubMed1997

Some problems on fertilization and embryonic development in vitro in mammals.

Recently, progress of studies and technique developments on human and mammalian fertilization and early embryonic development in vitro are markedly. At the present time, however, some problems are remaining. In mammalian embryo culture, the major obstacles to progress in analysing epigenic regulation of development in other than the mouse and rabbit are the infamous blocks to development in vitro. At the present time, further studies are needed to dissolve the precise mechanism of these blocks. Factors which affect on embryo development are a great number and analysis of them is considered to be important for clinical application of the embryo culture system. Intracytoplasmic sperm injection(ICSI), at the present time, is employed widely for basic research and the treatment of male infertility. Using ICSI, recent studies are showing that mouse round spermatids can fertilize mature oocyte and the fertilized oocytes(embryos) develop into normal offspring after embryo transfer to foster mothers. Also, a recent report indicates development of normal mice from oocytes injected with secondary spermacyte nuclei. However, since some unsolved problems on spermatogenic cells such as round spermatids and secondary spermacytes remain, further studies are needed.

Animals↗

PubMed1993

Gene expression during metamorphosis: an ideal model for post-embryonic development.

The precocious induction in vivo and in culture of insect and amphibian metamorphosis by exogenous ecdysteroids and thyroid hormones, and its retardation or inhibition by juvenile hormone and prolactin, respectively, has allowed the analysis of such diverse processes of post-embryonic development as morphogenesis, tissue remodelling, functional reorganization, and programmed cell death. Metamorphosis in vertebrates also shares many similarities with mammalian development in the late foetal and perinatal period. This review describes the regulation of expression of some of the 'adult' gene products during metamorphosis in invertebrates and vertebrates. Recent studies on metamorphosis have revealed the important role played by auto-induction of hormone receptor genes, based on which a model will be presented to explain the activation of 'downstream' genes which give rise to the adult phenotype. It will also be argued that metamorphosis is an ideal model for analyzing some of the major mechanisms governing post-embryonic development.

Amphibians↗

PubMed1997

Expression of transforming growth factor alpha (TGF-alpha) gene in mouse embryonic development.

PURPOSE: The expression of genes for TGF-alpha, epidermal growth factor (EGF), and the EGF receptor (EGFR) in mouse blastocysts was evaluated by the reverse transcription-polymerase chain reaction (RT-PCR). We evaluated the effects of TGF-alpha and EGF on the development of mouse embryo prior to implantation. RESULTS: The results revealed the presence of transcripts of TGF-alpha and EGFR. However, EGF mRNA was not observed in repeated experiments. None of these growth factors influenced the rate of development from the two-cell stage to the blastocyst stage when added to the culture medium. These effects were further examined on measuring the incorporation of tritiated thymidine and leucine, providing indices of the synthesis of DNA and protein, respectively. A concentration of only 0.1 ng/ml of TGF-alpha, which shares a cell surface receptor with EGF, stimulated the synthesis of both DNA and protein. EGF at a concentration of 10 ng/ml stimulated the synthesis of DNA and protein by blastocysts. To explore autocrine effects of TGF-alpha on the rate of blastocoel expansion, TGF-alpha antisense oligodeoxynucleotides was used to reduce expression of the TGF-alpha gene. TGF-alpha at a concentration of 0.1 ng/ml stimulates the rate of blastocoel expansion in early cavitating mouse blastocysts. In contrast, TGF-alpha antisense oligonucleotides significantly reduced the rate of expansion. CONCLUSIONS: Our present observations suggest that TGF-alpha/EGF and the EGFR may be involved in regulating embryonic development. In particular, TGF-alpha may serve as an autocrine factor in the regulation of embryonic development.

Animals↗

PubMed2002

The catalytic activity of the ErbB-2 receptor tyrosine kinase is essential for embryonic development.

Activation of the epidermal growth factor receptor (EGFR) family is thought to play a critical role in both embryogenesis and oncogenesis. The diverse biological activities of the EGFR family are achieved through various ligand-receptor and receptor-receptor interactions. One receptor that has been found to play a central role in this signaling network is ErbB-2/Neu, and it is considered the preferred heterodimerization partner for other members of the EGFR family. To assess the importance of the catalytic activity of ErbB-2 in embryonic development, we have generated mice expressing a kinase-dead erbB-2 cDNA under the transcriptional control of the endogenous promoter. Here, we show that mice homozygous for the kinase-dead erbB-2 allele die at midgestation and display the same spectrum of embryonic defects seen in erbB-2 knockout mutants. These observations suggest that the catalytic activity of ErbB-2 is essential for normal embryonic development.

Animals↗

PubMed1982

Changes in the neuroendocrine system during post-embryonic development in the buffalo-fly, Lyperosia exigua (De Meijere) (Diptera: Muscidae).

The neurosecretory cells of the pars intercerebralis and ring gland are examined in histological sections of larva, pupa and adult of buffalo-fly, Lyperosia exigua fixed at various intervals during the rpost-embryonic development. Three paired medial groups of the neurosecretory cells are observed in the larval brain. These groups show their displacement during the larval-pupal-adult moult. The medial neurosecretory A cells exhibit secretory activity by undergoing cyclic changes of synthesis and release during post-embryonic development. The ecdysial glands and a single corpus allatum also undergo cyclical changes in volume and histological appearance in accordance with the larval-pupal-adult moult.

Animals↗

PubMed2002

Essential role of S-adenosylmethionine decarboxylase in mouse embryonic development.

BACKGROUND: S-Adenosylmethionine decarboxylase (AdoMetDC) is one of the key enzymes involved in the biosynthesis of spermidine and spermine, which are essential for normal cell growth. To examine the role of polyamines in embryogenesis, we carried out targeted disruption of the mouse Amd1 gene, encoding AdoMetDC, to generate mice that can not synthesize spermidine and spermine. RESULTS: Amd1 heterozygous mice were viable, normal and fertile. However, homozygous Amd1(-/-) embryos died early in embryonic development, between E3.5 and E6.5 days post-coitus. Homozygous (Amd1(-/-)) blastocysts at E3.5 arrested cell proliferation immediately after the onset of cell culture, and this arrest was rescued by the addition of spermidine. Chromosomal DNA breakage did not occur in Amd1(-/-) blastocysts at E3.5, as determined by TUNEL assay. CONCLUSIONS: These results indicate that AdoMetDC plays an essential role in embryonic development and that polyamines are required for cell proliferation in the embryo after E3.5.

Adenosylmethionine Decarboxylase↗

PubMed1998

Effects of the feeding process of Ixodes scapularis (Acari: Ixodidae) on embryonic development of its parasitoid, Ixodiphagus hookeri (Hymenoptera: Encyrtidae).

The chalcid wasp Ixodiphagus hookeri (Howard) is a parasitoid of several ixodid ticks including the blacklegged tick, Ixodes scapularis Say. We evaluated effects of the feeding process of nymphal I. scapularis on the embryonic development of I. hookeri. Potentially wasp-parasitized nymphal I. scapularis were collected on Prudence Island, RI. Subsamples of the questing nymph cohort were allowed to feed on laboratory white mice. Both the body length and the scutal length of ticks were measured individually for questing nymphs and for feeding nymphs that were removed from hosts at time intervals of 12, 24, 36, 48, and 72 h after attachment. The diameters of wasp eggs they contained were also measured for each designated time interval. There was a positive relationship between the mean scutal index (ratio between body length and scutal length) of ticks and the mean diameter of wasp eggs during 72 h of tick feeding (P < 0.05). Moreover, it appeared that within 24 h of tick attachment, the scutal index of ticks remained unchanged. However, after that period, the scutal index increased significantly (P < 0.05). Diameters of wasp eggs increased continuously during tick feeding and at 72 h after attachment, enclosed eggs and completely formed larvae were found in several ticks. We conclude that factors related to the feeding process of nymphal I. scapularis are necessary to initiate the embryonic development of wasps.

Animals↗

PubMed1991

The embryonic development of the lateral nasal wall from 8 to 24 weeks.

This histological study of 20 fetal heads aged between 8 and 24 weeks of gestation demonstrates and describes the embryonic development of the lateral wall of the nose. The three turbinates (inferior, middle, and superior) arise as soft-tissue swellings (preturbinates) by 8 weeks' gestation. A cartilage capsule surrounds the nose at 8 weeks and by 9 weeks, medially directed flanges of cartilage have invaded all three preturbinates. The uncinate process arises from the medial surface of the lateral cartilaginous capsule and is first identifiable by 10 weeks. An "air space" progressively develops from 11 to 12 weeks lateral to the cartilaginous uncinate process and from this space, the embryonic channel to the maxillary sinus develops. The embryonic woven bone of the maxilla can be identified from 9 to 10 weeks and enlarges both absolutely and relatively to the nasal cavity, so that by 13 to 14 weeks, this expanding bone forms the lateral wall of the inferior meatus as the cartilaginous nasal capsule regresses.

Embryonic and Fetal Development↗

PubMedDate not supplied

Effects of lindane on oocyte maturation and preimplantation embryonic development in the mouse.

Lindane, an organochlorine insecticide, is suspected of preimplantation embryonic toxicity based on in vitro experiments with bovine and murine embryos. To verify this hypothesis in vivo we tested lindane for developmental alterations during early embryonic cleavage in the mouse. Two treatment schedules were tested: three daily doses of 15 or 25mg/kg b.w. lindane were orally administered to female mice either before mating or immediately after mating. Morphologic alterations (lysis or fragmentation of blastomeres, developmental arrest) of two-cell embryos and morulae were evaluated by inverted microscopy. In addition, cytologic abnormalities and cell proliferation delay, possibly induced during the first four cleavage cycles, were evaluated by fluorescent microscope analysis of the number and morphology of blastomere nuclei. A statistically significant increase of degenerating two-cell embryos was induced by exposure of preovulatory oocytes to the highest tested lindane dose. Early cleavage embryos exposed to the same dose showed a lower average number of blastomeres per morula, as well as a 40% reduction of the mitotic index with respect to matched controls. However, mean values in individual litters were variable and litter analysis did not show a lindane-related effect. One possible mechanism for the observed effects could be the recently demonstrated inhibitory action of lindane on gap junction-mediated cell communication between oocyte and cumulus cells. A comparison between human exposure levels and experimental doses based on measured and predicted blood concentrations suggests that there are ample margins of safety for human embryonic development at the present exposure levels.

Administration, Oral↗

PubMed1997

Role of epidermal growth factor and insulin-like growth factor-I on porcine oocyte maturation and embryonic development in vitro.

The effects of epidermal growth factor (EGF) and insulin-like growth factor-I (IGF-I) on the in vitro maturation of porcine oocytes were examined. Oocytes obtained from the ovaries of slaughtered prepubertal gilts were matured in modified Medium 199 supplemented with 25% porcine follicular fluid and gonadotropins, and fertilized in vitro. Oocytes were either fixed 16 h later to assess fertilization or cultured for 7 days to assess embryonic development. In Experiment 1, the addition of EGF to maturation medium increased the percentage of meiotically mature oocytes (88% v. 70%; P < 0.001) but did not affect the proportion of fertilized or cleaved oocytes. Blastocysts derived from oocytes matured in medium supplemented with 10 ng mL(-1) EGF had a greater number of cells compared with those of control blastocysts (51.1+/-5.1 v. 36.0+/-3.1; P < 0.02). In Experiment 2, the addition of IGF-I to maturation medium had no effect on meiotic maturation, fertilization or embryonic development. Our findings demonstrate that EGF plays an important role in both the meiotic and cytoplasmic maturation of porcine oocytes in vitro.

Animals↗

PubMed2006

Leptin has concentration and stage-dependent effects on embryonic development in vitro.

There is accumulating evidence that leptin may be directly involved in pre-implantation embryonic development, however, it is unclear whether there is a concentration and stage-dependent regulatory pattern. In this study, the addition of 10 ng/ml human recombinant leptin to the culture medium significantly increased the percentage of two-cell mouse embryos that developed into blastocysts and hatched blastocysts, whereas in the presence of 100 ng/ml leptin, the development rate was significantly inhibited. The total cell numbers in the hatched blastocysts were significantly higher in the presence of 10 ng/ml leptin compared with controls and higher concentrations. The differential sensitivity to leptin was found to vary among embryos at different stages of development. Supplementation of leptin (10 ng/ml) to culture medium at two- to eight-cell stages resulted in a consistent stimulatory effect on embryo development. Most interestingly, the inhibitory effect of high leptin concentration (100 ng/ml) on embryo development was diminished when it was added to the culture medium at the eight-cell stage of development. The concentration-dependent regulation pattern was confirmed using sheep embryos, under similar conditions although sheep embryos appeared to be more sensitive in responding to leptin. Having established the effect of exogenous leptin on embryo development, the expression pattern of leptin and its receptors were also investigated. Leptin mRNA was not detected in mouse two-, four-, eight-cell and blastocyst stage embryos, whereas three isoforms of leptin receptor (Ob-Ra, Ob-Rb and Ob-Re) were identified in these cells, indicating that leptin is likely to modulate embryo development via a paracrine signalling system.

Animals↗