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At least 865 records · Page 48Linked to original sources

PubMed2003

Regional specification during embryogenesis in Rhynchonelliform brachiopods.

Fate maps have been constructed for embryos of Hemithiris and Terebratulina, representatives of two orders in the class Rhynchonellata that have been separated since the middle Ordovician. These fate maps are identical. The animal region of the egg forms the ectodermal covering of the apical lobe and the vegetal region is the site of gastrulation; the vegetal region forms the ectoderm of the ventral and posterior regions of the larva, endoderm and mesoderm. The cells that make up the animal region shift 90 degrees with respect to the vegetal pole during gastrulation. The timing and mode of regional specification in these two species are also identical. In each case, the animal region of the unfertilized egg has the intrinsic ability to form apical lobe ectoderm, while the vegetal region has the ability to form a normal larva. During embryogenesis, the vegetal region interacts with the animal region to suppress apical tuft differentiation in the apical lobe and to promote mantle lobe ectodermal differentiation, while the ability of the vegetal half to regulate by forming apical lobe structures is lost. The plane of bilateral symmetry of the larva begins to be set up between the late blastula and early gastrula stage. The fate maps and the processes of regional specification are compared in the four subphyla that make up the Brachiopoda and used to test a developmental model that provides an explanation for the variety of different body plans generated during the Cambrian.

Alkaline Phosphatase↗

PubMed1986

Acrolein and embryogenesis: an experimental study.

The effects of acrolein were studied on the chick embryos of 48 and 72 hr of incubation. Acrolein was dissolved in physiological saline and injected into the air sacs of the eggs at doses ranging from 0.001 to 0.1 mg per egg. The controls received and equal amount of saline only (0.1 ml per egg). All the embryos including controls were examined at Day 13. In all, 600 eggs were utilized for this investigation. At 48 hr incubation, the percentage survival ranged from 80 to 0 as the dosage of acrolein was increased. Embryonic mortality following 72 hr incubation did not increase significantly at any dose level. Gross malformations such as short and twisted limbs, everted viscera, microphthalmia, short and twisted neck, and hemorrhage over the body were observed. The frequency and the types of gross abnormalities did not vary much in the 48- or 72-hr-treated groups. The incidence of malformation in the controls was low. The results of this study indicate that acrolein is embryotoxic at higher doses and moderately teratogenic to chick embryogenesis.

Abnormalities, Drug-Induced↗

PubMed1986

Concentration and chemical status of arsenic in the blood of pregnant hamsters during critical embryogenesis. 1. Subchronic exposure to arsenate utilizing constant rate administration.

We have determined the concentration, availability, and chemical status of radiolabeled arsenic in the blood of pregnant hamsters at the beginning (morning of Day 8) and the end (morning of Day 9) of the critical period of embryogenesis. Hamster dams were exposed to teratogenic doses of arsenate by means of osmotic minipumps implanted on the morning of Day 6 of the gestation period. Whole blood arsenic concentrations were the same for 48 and 72 hr postimplant. The arsenic concentration of plasma equaled that of red cells. Plasma arsenic was not bound to macromolecules and had the same chemical status 48 and 72 hr postimplant. Arsenate was the dominant form (67% of the total). However, the presence of dimethylarsinic acid and arsenite indicates that the pentavalent species was metabolized. Red cell arsenic was bound to macromolecules in the cell sap. Seventy percent of red cell sap arsenic was dialyzable 48 hr postimplant, but only 56% 72 hr postimplant. Arsenate was the dominant dialyzable red cell species on Day 8 and arsenite was the major dialyzable form on Day 9. Our findings demonstrate a relationship between the maternal blood concentration and chemical status of arsenic and the presence of malformations resulting from a constant rate exposure of pregnant hamsters to arsenate via the osmotic minipump.

Animals↗

PubMed2001

Paternally inherited transgenes are down-regulated but retain low activity during early embryogenesis in Arabidopsis.

We investigated the timing of transgene activation after fertilisation in Arabidopsis following crosses and using two transgenic promoters (from the AtCYCB1 and AtLTP1 genes). Using both a transactivation system and direct transcriptional fusion to drive beta-glucuronidase reporter expression, reciprocal crosses showed a lack of expression of the paternal components. This is consistent with a lack of paternal genome activity previously reported during early seed development in Arabidopsis [Viella-Calzada et al. (2000) Nature 404, 91-94]. However, transactivation experiments of the BARNASE gene gave evidence that at least some paternal loci retain transcriptional activity, though at a low level, during early embryogenesis.

Arabidopsis↗

PubMed2003

Two variants of zebrafish p100 are expressed during embryogenesis and regulated by Nodal signaling.

Human p100 protein was first identified as a transcriptional coactivator of Epstein-Barr virus nuclear antigen 2, and has been shown to be a coactivator of other cellular transactivators. Its roles in development of vertebrate embryos, however, have not been reported. We have identified a zebrafish ortholog of the human p100 coactivator. The zebrafish p100 transcript is processed to two alternative variants, long and short forms, referred to as p100L and p100S, respectively. Both GFP-p100L and GFP-p100S fusion proteins are located in the cytoplasm of transfected culture cells and microinjected embryonic cells. Analysis of transcripts with Northern blots revealed the presence of p100L and lower amounts of p100S mRNAs from the one-cell stage throughout the life cycle. Whole-mount in situ hybridization shows that p100L and p100S share the same spatiotemporal expression pattern. Their zygotic expression is initially restricted to axial mesoderm precursors during gastrulation, and then spreads over other tissues during segmentation, and finally is constrained to some internal organs at day 5. We also find that Nodal signaling is essential for the zygotic expression of p100. These studies pave the way to understanding in depth the role of p100 during vertebrate embryogenesis.

Alternative Splicing↗

PubMed1998

Transgenic Cre recombinase expression in germ cells and early embryogenesis directs homogeneous and ubiquitous deletion of loxP-flanked gene segments.

We report on the establishment of a transgenic mouse line expressing Cre recombinase under control of the c-kit promoter. Expression of Cre recombinase was only observed in late spermatogenesis and oogenesis, however, Cre-mediated deletion of floxed gene segments occurred at this stage as well as in early embryogenesis. As a consequence of this, a chimeric distribution of loxed alleles was found in a large fraction of these mice. The chimerism was very homogeneous in different organs and tissues of the same individual but varied between different individual offspring. The potential uses for this mouse line are discussed.

Alleles↗

PubMed2002

Ovarian 3-hydroxy-3-methylglutaryl-CoA reductase in Blattella germanica (L.): pattern of expression and critical role in embryogenesis.

In the ovary of adult Blattella germanica, the enzyme 3-hydroxy-3-methylglutaryl-CoA reductase (HMG-CoA reductase) is highly expressed in mid-late vitellogenesis, suggesting a functional link of the mevalonate pathway with choriogenesis. The inhibitor of HMG-CoA reductase, fluvastatin, applied in females in late vitellogenesis, inhibits the activity of the enzyme in the ovary and in the developing embryos within the ootheca. This does not affect choriogenesis or ootheca formation but reduces the number of larvae per ootheca. Our results suggest that fluvastatin is incorporated into the oocytes and has delayed inhibitory effects on the oviposited eggs. HMG-CoA reductase is essential for embryogenesis, but not for chorion formation.

Journal Article↗

PubMed1992

Communicating bronchopulmonary foregut malformations: classification and embryogenesis.

Communicating bronchopulmonary foregut malformations (CBPFMs) are characterized by a fistula between an isolated portion of respiratory tissue (ie, a lung, a lung lobe, or a segment) and esophagus or stomach. We combine our 30-year (1959 to 1989) experience of 6 cases with 51 reported patients to propose a CBPFM classification supported by a proposed embryogenesis theory. Group I (16%): anomaly is associated with esophageal atresia and tracheoesophageal fistula. Group II (33%): one lung originates from the lower esophagus. Group III (46%): an isolated anatomic lung lobe or segment communicates with the esophagus or stomach. Group IV (5%): A portion of the normal bronchial system communicates with the esophagus. The portion of the lung served by the communicating bronchus receives systemic blood supply. The right and left lung sacs curve dorsally to embrace the lower esophagus during normal lung development. At this stage a part of the lung bud joins the esophagus. This segment then breaks away from the main pulmonary anlage to form a CBPFM. CBPFMs should be considered in the workup of infants with respiratory distress and/or recurrent pneumonias. Patients with suspected pulmonary sequestration should undergo contrast studies to exclude a gastrointestinal communication.

Bronchial Fistula↗

PubMed1999

Apoptosis in tracheoesophageal embryogenesis in rat embryos with or without adriamycin treatment.

PURPOSE: The aim of this study was to determine whether apoptosis participates in separation of the foregut into trachea and esophagus and to evaluate the potential role of apoptosis in the development of esophageal atresia and tracheoesophageal fistula (EA + TEF) induced by Adriamycin. METHODS: Timed-pregnant rats were injected daily with either saline or Adriamycin (2 mg/kg) intraperitoneally on days 6 to 9 of gestation. Paraffin sections were prepared from 31 experimental and 31 control embryos at days 12 and 13 of gestation. Condensed nuclei were identified on the paraffin sections using the TUNEL method. Apoptosis was quantified by counting the positively stained cell nuclei in transverse sections of embryos. RESULTS: In day 12 control embryos the number of apoptotic nuclei in both lateral ridges of the foregut was high (15.67 +/- 1.38) but relatively low (4.17 +/- 0.80) in Adriamycin-treated embryos (P< .0001). In day 13 Adriamycin-treated embryos, the number of apoptotic nuclei in the region of the upper esophageal pouch was extremely high (23.78.5 +/- 2.20) compared with no detectable apoptotic nuclei in the control embryos. CONCLUSIONS: Apoptosis is required for normal tracheoesophageal embryogenesis and may be an important mechanism to be involved in the embryological development of esophageal atresia and tracheoesophageal fistula.

Animals↗

PubMed1985

Congenital ureteral valves--an abnormality of ureteral embryogenesis?

Congenital ureteral valves are a rare cause of obstructive uropathy and the majority of cases are diagnosed only at surgery or autopsy. A case of congenital ureteral valve associated with an incompletely duplicated kidney is reported and the literature on ureteral valves is reviewed. Modern uroradiological and endoscopic diagnostic techniques should result in a more precise preoperative diagnosis. The high incidence of associated genitourinary anomalies, particularly duplication anomalies, suggests abnormal ureteral embryogenesis as an etiological factor in congenital ureteral valve formation.

Adolescent↗

PubMed1975

Embryogenesis of chordee.

Gross and microscopic examination of 46 consecutive male therapeutic abortion specimens, ranging in size from 60 to 180 mm. crown-rump, demonstrated that 89 per cent of the fetuses had some ventral curvature of the penis. Athough presumably all penises are ventrally curved through the tenth week of gestation, in our study this curvature was most prominent in the sixteenth through twentieth weeks of gestation and in 44 per cent of the fetuses it persisted through the sixth lunar month. Examination of premature infants revealed a 31 per cent incidence of chordee and serial examinations of a 27-week gestational age infant demonstrated gradual complete correction of the chordee during the ensuing 6 weeks. We propose that ventral curvature of the penis is a normal stage of embryogenesis and chordee without hypospadias may represent an arrest of development at this earlier stage.

Gestational Age↗

PubMed1997

Developmental toxicity induced during early stages of mammalian embryogenesis.

Both a conceptual and a practical borderland between teratology and mutagenesis is early embryogenesis, the period between fertilization and gastrulation. Radiation and a variety of chemicals adversely affect the early conceptus leading to in utero mortality and malformations. The post-fertilization period of susceptibility differs from exposures of gametes, the later producing excessive pre- and peri-implantational death and low rates of fetal anomalies predominated by growth retardation. In contrast mutagen exposure of the zygote induces peri-implantational death, pan-gestational death and fetal anomalies predominated by hydrops, abdominal wall defects, and eye aberrations. The mechanism for this pathology remains unclear. These same agents produce a broader range of phenotypic anomalies during the remainder of pre-gastrulation development with anomalies overlapping those induced during organogenesis. Retinoic acid and 5-azacytidine administered prior to gastrulation produce novel malformation syndromes indicative of gene expression modification. The rates and types of defects from mutagen treatment of both gametes and the early conceptus contrast with those resulting from embryonic treatment during organogenesis, and the mechanisms are likely to differ. The pre-gastrulation period has not been explored to the extent reported during gametogenesis or organogenesis. Pre-gastrulation teratology is a new area of investigation with relevance both to reproductive toxicology and to mammalian developmental biology.

Abnormalities, Drug-Induced↗

PubMed1996

Biphasic intestinal development in amphibians: embryogenesis and remodeling during metamorphosis.

Intestinal development in anurans is a biphasic process. The embryogenesis of intestine resembles that in higher vertebrates. The subsequent remodeling process during metamorphosis to produce an adult organ is controlled by TH. Recent progress in studying TH action and its application to amphibian metamorphosis has provided considerable insights into the remodeling process. One possible model for the TH-induced gene regulation cascade of intestinal remodeling is presented in Fig. 9. It is assumed that TRs function as heterodimers with RXRs. In the absence of TH, the TR-RXR heterodimers can bind to TH response elements present in the target genes and repress the basal transcription of these genes (Fondell et al., 1993; Damm et al., 1989; Sap et al., 1989; Baniahmad et al., 1992; Ranjan et al., 1994). The binding of TH leads to conformational changes in the receptor complexes that in turn activate gene transcription. The products of these early response genes then participate in the activation of the remaining gene regulation cascade. Exactly how this occurs remains unknown. Interestingly, the early response genes include not only transcription factors but also other proteins such as metalloproteinases. The transcription factors could activate or repress downstream TH response genes directly. Other proteins are likely to assert their effect indirectly. For example, they could modify the ECM or cell surface. In addition, they could regulate and/or participate in signal transduction by growth factors. The cooperation between these complex intra- and extracellular processes eventually results in the degeneration of the larval organ and formation of the adult tissue. This simplified scheme immediately raises many questions. Although the mRNAs for TRs and RXRs are present in the intestine and the other tissues during metamorphosis (Yaoita and Brown, 1990; Kawahara et al., 1991; Y.-B. Shi, unpublished observations), it is unknown whether the mRNA levels reflect the protein levels. It also remains to be tested whether TR-RXR is indeed the functional complex in vivo and whether the heterodimer is responsible for the activation of the early response genes isolated to date. The majority of the early response genes are ubiquitous. Of the few intestine-specific genes, none of them have yet been identified by sequence analysis. It is of great interest to understand how the same genes expressed in tissues undergoing drastically different changes can exert their biological effects. It is likely that together with existing proteins in the intestine, these early genes regulate tissue-specific downstream genes, which in turn determine the tissue-specific transformation. An important issue is to establish the identity of these downstream genes.

Amphibians↗

PubMed1996

Cadherin cell adhesion molecules in differentiation and embryogenesis.

The cadherin gene superfamily of calcium-dependent cell-cell adhesion molecules contains more than 40 members. We summarize functions attributed to these proteins, especially their roles in cellular differentiation and embryogenesis. We also describe hierarchies of protein-protein interactions between cadherins and cadherin-associated proteins (catenins). Several signal transduction pathways converge on, and diverge from, the cadherin/catenin complex to regulate its function; we speculate on roles of these signaling processes for cell structure and function. This review provides a framework for interpretation of developmental functions of cadherin cell adhesion molecules.

Animals↗

PubMed1996

A cyclin-dependent kinase inhibitor, Dacapo, is necessary for timely exit from the cell cycle during Drosophila embryogenesis.

In a screen for genes that interact with the Rap1 GTPase, we have identified a Drosophila gene, dacapo (dap), which is a member of the p21/p27 family of cdk inhibitors. Unlike mammalian cdk inhibitors studied to date, dap is essential for normal embryonic development. Dacapo inhibits cyclin-cdk activity in vitro. Overexpressing dap during eye development interferes with cell cycle progression and interacts genetically with the retinoblastoma homolog (Rbf) and cyclin E. dap expression in embryos parallels the exit of cells from the cell cycle. dap mutant embryos delay the normal cell cycle exit during development; many cells complete an additional cycle and subsequently become quiescent. Thus, dap functions during embryogenesis to achieve a precisely timed exit from the cell cycle.

Amino Acid Sequence↗

PubMed2003

Anosmin-1 immunoreactivity during embryogenesis in a primitive eutherian mammal.

Kallmann syndrome is hypogonadotropic hypogonadism coupled with anosmia. A morphological study found that the endocrine disorder in X-linked Kallmann syndrome is due to failed migration of gonadotropin releasing-hormone (GnRH) neurons from the olfactory placode to the brain during development. Anosmia results from agenesis of the olfactory bulbs and tracts. The gene responsible for the X-linked form of Kallmann syndrome, KAL-1, has been characterized. The orthologues of KAL-1 have been isolated in the chick and the zebrafish, but still await identification in rodents. In the present study, we used polyclonal and monoclonal antibodies to the human KAL-1 encoded protein, anosmin-1, in a primitive mammal, the Asian musk shrew. Musk shrews are insectivores and are therefore evolutionarily closer to primates than rodents. By immunoblot analysis of musk shrew tissues, a band of the expected apparent molecular mass (95 kDa) was detected in several structures of the central nervous system, but not in liver or muscle, which is consistent with the gene expression pattern previously reported in the chick. By immunohistochemical analysis, anosmin-1 was detected in the developing olfactory epithelium, the olfactory, vomeronasal and terminalis nerves, the olfactory bulbs, the cerebellum and the cerebral cortex and in several other regions of the brain, during musk shrew embryogenesis. Furthermore, migrating gonadotropin releasing-hormone (GnRH)-immunoreactive neurons were seen in close association with anosmin-1-immunoreactive fibers. Assuming that the protein is present at the surface of these fibers, we suggest a possible direct role of anosmin-1 in the migration of GnRH neurons in this species.

Animals↗

PubMed1998

Vsx-2, a gene encoding a paired-type homeodomain, is expressed in the retina, hindbrain, and spinal cord during goldfish embryogenesis.

Vsx-2 encodes a paired-type homeodomain and is the goldfish ortholog of the murine Chx10 gene. During development, Vsx-2 is expressed at high levels in goldfish and zebrafish retina. In addition to the retina, in situ hybridization studies using whole mount and cryosection embryos demonstrate that Vsx-2 is also expressed in subsets of neurons in the hindbrain and in the spinal cord. Expression begins approximately at the metencephalon-myelencephalon border and continues in a restricted lateral zone along the rostral-caudal axis of the spinal cord. These observations suggest a potential requirement for Vsx-2 in the specification and/or the maintenance of neurons in specific CNS regions during embryogenesis. Also discussed are other transcription factors which may act combinatorially with Vsx-2 to regulate neuronal differentiation.

Animals↗

PubMed1997

Sequence analysis of a gene family encoding Taenia ovis vaccine antigens expressed during embryogenesis of eggs.

The 45W vaccine antigen of the cestode parasite Taenia ovis is a member of a small gene family estimated to comprise six members. All six genes were cloned and characterised. Nucleotide sequence analysis of the different family members identified a set of closely related genes exhibiting between 75.2 and 98.6% DNA sequence homology. Intron/exon structure for the various genes constituting the family was found to be conserved. Open reading frame analysis and pairwise alignments of predicted polypeptides from the various members of the family revealed that the encoded proteins share between 51.8 and 96.5% amino acid identity with the host-protective 45W antigen. Polymerase chain reaction (PCR) primers were designed which allowed amplification of individual family members in a transcript-specific manner. These were used to investigate gene expression in different developmental stages of the parasite by reverse-transcription polymerase chain reaction (RT-PCR). All members of the gene family were expressed during the T. ovis life-cycle. 45W gene family transcription correlates with embryogenesis of eggs and expression is increased in activated eggs (oncospheres). One family member, ToW3S, was expressed in the early larvae (cysticercus) stages. Expression of genes closely related to the 45W vaccine antigen has important implications for immune evasion under selection from the application of a 45W-based vaccine.

Amino Acid Sequence↗